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Gas Exchange and
Respiratory Function
Case Study •
Applying Concepts From NANDA, NIC,
and NOC
A Patient With Impaired Cough Reflex A Patient With Impaired Cough Reflex
Mrs. Lewis , age 77 years, is admitted to the hospital for left lower lobe pneumonia. Her vital signs are: Temp 100.6°F; HR 90 and regular; B/P: 142/74; Resp. 28. She has a weak cough, diminished breath sounds over the lower left lung field, and coarse rhonchi over the midtracheal area. She can expectorate some sputum, which is thick and grayish green. She has a history of stroke. Secondary to the stroke she has impaired gag and cough reflexes and mild weakness of her left side. She is allowed food and fluids because she can swallow safely if she uses the chin-tuck maneuver.
Visit thePoint to view a concept map that illustrates the relationships that exist between the nursing diagnoses, interventions, and outcomes for the patient’s clinical problems.
Nursing Classifications and Languages
485
NANDA NURSING DIAGNOSES
NIC NURSING INTERVENTIONS
NOC NURSING OUTCOMES
Return to functional baseline sta- tus, stabilization of, or improvement in: RESPIRATORY STATUS : A IRWAY PATENCY —Extent to which the tracheobronchial passages remain open
RESPIRATORY STATUS : G AS EXCHANGE —The alveolar exchange of O 2 and CO 2 to main- tain arterial blood gas concentra- tions
RESPIRATORY STATUS : VENTILATION—Movement of air in and out of the lungs
INEFFECTIVE AIRWAY CLEARANCE — Inability to clear secretions or ob- structions from the respiratory tract to maintain a clear airway
IMPAIRED GAS EXCHANGE —Excess or deficit in oxygenation and/or carbon dioxide elimination at the alveolar-capillary membrane
INEFFECTIVE BREATHING PATTERN — Inspiration and/or expiration that does not provide adequate venti- lation
RISK FOR ASPIRATION—At risk for entry of gastrointestinal secretions, oropharyngeal secre- tions, solids, or fluids into tracheobronchial passages
RESPIRATORY MONITORING — Collection and analysis of patient data to ensure airway patency and adequate gas exchange
AIRWAY MANAGEMENT—Facilitation of patency of air passages
COUGH ENHANCEMENT— Promotion of deep inhalation by the patient with subsequent gen- eration of high intrathoracic pres- sures and compression of under- lying lung parenchyma for the forceful expulsion of air
AIRWAY SUCTIONING —Removal of airway secretions by inserting a suction catheter into the patient’s oral airway and/or trachea
ASPIRATION PRECAUTIONS— Prevention or minimization of risk factors in the patient at risk for aspiration
Bulechek, G. M., Butcher, H. K., & Dochterman, J. M. (2008). Nursing interventions classification (NIC) (5th ed.). St. Louis: Mosby. Johnson, M., Bulechek, G., Butcher, H. K., et al. (2006). NANDA, NOC, and NIC linkages (2nd ed.). St. Louis: Mosby. Moorhead, S., Johnson, M., Mass, M. L., et al. (2008). Nursing outcomes classification (NOC) (4th ed.). St. Louis: Mosby. NANDA International. (2007). Nursing diagnoses: Definitions & classification 2007–2008. Philadelphia: North American Nursing Diagnosis Association.
Chapter 21 Assessment of Respiratory Function 487
Disorders of the respiratory system are common and are en- countered by nurses in every setting from the community to the intensive care unit. Expert assessment skills must be de- veloped and used to provide the best care for patients with acute and chronic respiratory problems. In order to differ- entiate between normal and abnormal assessment findings, an understanding of respiratory function and the signifi- cance of abnormal diagnostic test results is essential.
Anatomic and Physiologic Overview
The respiratory system is composed of the upper and lower respiratory tracts. Together, the two tracts are responsible for ventilation (movement of air in and out of the airways). The upper respiratory tract, known as the upper airway, warms and filters inspired air so that the lower respiratory tract (the lungs) can accomplish gas exchange. Gas exchange involves delivering oxygen to the tissues through the bloodstream and expelling waste gases, such as carbon dioxide, during ex- piration. The respiratory system works in concert with the cardiovascular system; the respiratory system is responsible for ventilation and diffusion, and the cardiovascular system is responsible for perfusion (Farquhar & Fantasia, 2005).
Anatomy of the Respiratory System
Upper Respiratory Tract
Upper airway structures consist of the nose, sinuses and nasal passages, pharynx, tonsils and adenoids, larynx, and trachea.
Nose
The nose serves as a passageway for air to pass to and from the lungs. It filters impurities and humidifies and warms the air as it is inhaled. The nose is composed of an external and an internal portion. The external portion protrudes from the face and is supported by the nasal bones and cartilage. The anterior nares (nostrils) are the external openings of the nasal cavities. The internal portion of the nose is a hollow cavity sepa- rated into the right and left nasal cavities by a narrow vertical divider, the septum. Each nasal cavity is divided into three passageways by the projection of the turbinates from the lat- eral walls. The turbinate bones are also called conchae (the name suggested by their shell-like appearance). Because of their curves, these bones increase the mucous membrane sur- face of the nasal passages and slightly obstruct the air flowing through them (Fig. 21-1). Air entering the nostrils is deflected upward to the roof of the nose, and it follows a circuitous route before it reaches the nasopharynx. It comes into contact with a large surface of moist, warm, highly vascular, ciliated mucous membrane (called nasal mucosa) that traps practically all the dust and organisms in the inhaled air. The air is mois- tened, warmed to body temperature, and brought into con- tact with sensitive nerves. Some of these nerves detect odors; others provoke sneezing to expel irritating dust. Mu- cus, secreted continuously by goblet cells, covers the surface of the nasal mucosa and is moved back to the nasopharynx by the action of the cilia (fine hairs).
Paranasal Sinuses The paranasal sinuses include four pairs of bony cavities that are lined with nasal mucosa and ciliated pseudostrati- fied columnar epithelium. These air spaces are connected by a series of ducts that drain into the nasal cavity. The sinuses are named by their location: frontal, ethmoidal, sphenoidal, and maxillary (Fig. 21-2). A prominent function of the si- nuses is to serve as a resonating chamber in speech. The si- nuses are a common site of infection.
Pharynx, Tonsils, and Adenoids The pharynx, or throat, is a tubelike structure that connects the nasal and oral cavities to the larynx. It is divided into three regions: nasal, oral, and laryngeal. The nasopharynx is located posterior to the nose and above the soft palate. The oropharynx houses the faucial, or palatine, tonsils. The laryngopharynx extends from the hyoid bone to the cricoid cartilage. The epiglottis forms the entrance to the larynx.
Frontal sinus
Superior turbinate Middle turbinate
Inferior turbinate
Hard palate
Cribriform plate of ethmoid Sphenoidal sinus Sella turcica
Soft palate
Orifice of auditory (eustachian) tube Figure 21-1 Cross-section of nasal cavity.
Frontal Ethmoid Sphenoid Maxillary
Figure 21-2 The paranasal sinuses.
488 Unit 5 Gas Exchange and Respiratory Function
The adenoids, or pharyngeal tonsils, are located in the roof of the nasopharynx. The tonsils, the adenoids, and other lymphoid tissue encircle the throat. These structures are important links in the chain of lymph nodes guarding the body from invasion by organisms entering the nose and the throat. The pharynx functions as a passageway for the respiratory and digestive tracts.
Larynx
The larynx, or voice organ, is a cartilaginous epithelium- lined structure that connects the pharynx and the trachea. The major function of the larynx is vocalization. It also pro- tects the lower airway from foreign substances and facili- tates coughing. It is frequently referred to as the voice box and consists of the following:
- Epiglottis: a valve flap of cartilage that covers the opening to the larynx during swallowing
- Glottis: the opening between the vocal cords in the larynx
- Thyroid cartilage: the largest of the cartilage struc- tures; part of it forms the Adam’s apple
- Cricoid cartilage: the only complete cartilaginous ring in the larynx (located below the thyroid cartilage)
- Arytenoid cartilages: used in vocal cord movement with the thyroid cartilage
- Vocal cords: ligaments controlled by muscular move- ments that produce sounds; located in the lumen of the larynx
Trachea The trachea, or windpipe, is composed of smooth muscle with C-shaped rings of cartilage at regular intervals. The cartilaginous rings are incomplete on the posterior surface and give firmness to the wall of the trachea, preventing it from collapsing. The trachea serves as the passage between the larynx and the bronchi.
Lower Respiratory Tract The lower respiratory tract consists of the lungs, which contain the bronchial and alveolar structures needed for gas exchange.
Lungs The lungs are paired elastic structures enclosed in the thoracic cage, which is an airtight chamber with distensible walls (Fig. 21-3). Ventilation requires movement of the walls of the thoracic cage and of its floor, the diaphragm. The effect of these movements is alternately to increase and decrease the ca- pacity of the chest. When the capacity of the chest is in- creased, air enters through the trachea (inspiration) because of the lowered pressure within and inflates the lungs. When the chest wall and diaphragm return to their previous positions (ex- piration), the lungs recoil and force the air out through the bronchi and trachea. Inspiration occurs during the first third of the respiratory cycle, expiration during the later two thirds. The inspiratory phase of respiration normally requires energy; the expiratory phase is normally passive, requiring very little energy.
A
Frontal sinus Nasal cavity
Epiglottis Right Lung
Right bronchus
Nasopharynx Oropharynx Laryngeal pharynx
Pharynx
Larynx and vocal cords Esophagus
Trachea
Left lung
Mediastinum
Terminal bronchiole
Diaphragm
From pulmonary artery
To pulmonary vein Alveolar duct
Alveoli
Capillaries B
C
Thoracic vertabra
Visceral pleura
Parietal pleura
Pleural space
Left Lung
Wall of thorax
Sternum
Right Lung
Sphenoidal sinus
Figure 21-3 The respiratory system; A, upper respiratory structures and the structures of the thorax; B, alveoli, C, and a horizontal cross-section of the lungs.
490 Unit 5 Gas Exchange and Respiratory Function
survive for long without a continuous supply of oxygen. However, as a result of oxidation in the body tissues, carbon dioxide is produced and must be removed from the cells to prevent the buildup of acid waste products. The respiratory system performs this function by facilitating life-sustaining processes such as oxygen transport, respiration and ventila- tion, and gas exchange.
Oxygen Transport
Oxygen is supplied to, and carbon dioxide is removed from, cells by way of the circulating blood. Cells are in close con- tact with capillaries, the thin walls of which permit easy passage or exchange of oxygen and carbon dioxide. Oxygen diffuses from the capillary through the capillary wall to the interstitial fluid. At this point, it diffuses through the mem- brane of tissue cells, where it is used by mitochondria for cellular respiration. The movement of carbon dioxide oc- curs by diffusion in the opposite direction—from cell to blood.
Respiration
After these tissue capillary exchanges, blood enters the sys- temic veins (where it is called venous blood) and travels to the pulmonary circulation. The oxygen concentration in blood within the capillaries of the lungs is lower than in the lungs’ air sacs (alveoli). Because of this concentration gra- dient, oxygen diffuses from the alveoli to the blood. Carbon dioxide, which has a higher concentration in the blood than in the alveoli, diffuses from the blood into the alveoli. Movement of air in and out of the airways (ventilation) continually replenishes the oxygen and removes the carbon dioxide from the airways and lungs. This whole process of gas exchange between the atmospheric air and the blood and between the blood and cells of the body is called respi- ration.
Ventilation
During inspiration, air flows from the environment into the trachea, bronchi, bronchioles, and alveoli. During expira- tion, alveolar gas travels the same route in reverse. Physical factors that govern air flow in and out of the lungs are collectively referred to as the mechanics of venti- lation and include air pressure variances, resistance to air flow, and lung compliance.
Air Pressure Variances
Air flows from a region of higher pressure to a region of lower pressure. During inspiration, movement of the diaphragm and other muscles of respiration enlarges the thoracic cavity and thereby lowers the pressure inside the thorax to a level below that of atmospheric pressure. As a result, air is drawn through the trachea and bronchi into the alveoli. During expiration, the diaphragm relaxes and the lungs recoil, re- sulting in a decrease in the size of the thoracic cavity. The alveolar pressure then exceeds atmospheric pressure, and air flows from the lungs into the atmosphere.
Airway Resistance
Resistance is determined chiefly by the radius or size of the airway through which the air is flowing. Any process that changes the bronchial diameter or width affects airway re-
sistance and alters the rate of air flow for a given pressure gradient during respiration (Chart 21-1). With increased resistance, greater-than-normal respiratory effort is required to achieve normal levels of ventilation.
Compliance Compliance, or distensibility, is the elasticity and expand- ability of the lungs and thoracic structures. Compliance al- lows the lung volume to increase when the difference in pressure between the atmosphere and thoracic cavity (pres- sure gradient) causes air to flow in. Factors that determine lung compliance are the surface tension of the alveoli (nor- mally low with the presence of surfactant) and the connec- tive tissue (ie, collagen and elastin) of the lungs. Compliance is determined by examining the volume– pressure relationship in the lungs and the thorax. Compli- ance is normal (1.0 L/cm H 2 O) if the lungs and thorax eas- ily stretch and distend when pressure is applied. High or in- creased compliance occurs if the lungs have lost their elasticity and the thorax is overdistended (eg, in emphy- sema). Low or decreased compliance occurs if the lungs and thorax are “stiff.” Conditions associated with decreased compliance include morbid obesity, pneumothorax, hemo- thorax, pleural effusion, pulmonary edema, atelectasis, pul- monary fibrosis, and acute respiratory distress syndrome (ARDS), which are discussed in later chapters in this unit. Measurement of compliance is one method used to assess the progression and improvement in patients with ARDS. Lungs with decreased compliance require greater-than- normal energy expenditure by the patient to achieve nor- mal levels of ventilation. Compliance is usually measured under static conditions.
Lung Volumes and Capacities Lung function, which reflects the mechanics of ventilation, is viewed in terms of lung volumes and lung capacities. Lung volumes are categorized as tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual vol- ume. Lung capacity is evaluated in terms of vital capacity, inspiratory capacity, functional residual capacity, and total lung capacity. These terms are described in Table 21-1.
Pulmonary Diffusion and Perfusion Diffusion is the process by which oxygen and carbon diox- ide are exchanged at the air–blood interface. The alveo- lar–capillary membrane is ideal for diffusion because of its
Chart 21-1 • Causes of Increased Airway
Resistance
Common phenomena that may alter bronchial diameter, which affects airway resistance, include the following:
- Contraction of bronchial smooth muscle—as in asthma
- Thickening of bronchial mucosa—as in chronic bronchitis
- Obstruction of the airway—by mucus, a tumor, or a foreign body
- Loss of lung elasticity—as in emphysema, which is characterized by connective tissue encircling the airways, thereby keeping them open during both inspiration and expiration
Chapter 21 Assessment of Respiratory Function 491
thinness and large surface area. In the normal healthy adult, oxygen and carbon dioxide travel across the alveolar– capillary membrane without difficulty as a result of differ- ences in gas concentrations in the alveoli and capillaries. Pulmonary perfusion is the actual blood flow through the pulmonary circulation. The blood is pumped into the lungs by the right ventricle through the pulmonary artery. The pulmonary artery divides into the right and left branches to supply both lungs. These two branches divide further to supply all parts of each lung. Normally about 2% of the blood pumped by the right ventricle does not perfuse the alveolar capillaries. This shunted blood drains into the left side of the heart without participating in alveolar gas exchange. The pulmonary circulation is considered a low-pressure system because the systolic blood pressure in the pul- monary artery is 20 to 30 mm Hg and the diastolic pressure is 5 to 15 mm Hg. Because of these low pressures, the pul- monary vasculature normally can vary its capacity to ac- commodate the blood flow it receives. However, when a person is in an upright position, the pulmonary artery pres- sure is not great enough to supply blood to the apex of the lung against the force of gravity. Thus, when a person is up- right, the lung may be considered to be divided into three sections: an upper part with poor blood supply, a lower part with maximal blood supply, and a section between the two with an intermediate supply of blood. When a person who
is laying down turns to one side, more blood passes to the dependent lung. Perfusion is also influenced by alveolar pressure. The pul- monary capillaries are sandwiched between adjacent alve- oli. If the alveolar pressure is sufficiently high, the capillar- ies are squeezed. Depending on the pressure, some capillaries completely collapse, whereas others narrow. Pulmonary artery pressure, gravity, and alveolar pressure determine the patterns of perfusion. In lung disease, these factors vary, and the perfusion of the lung may become very abnormal.
Ventilation and Perfusion Balance and Imbalance Adequate gas exchange depends on an adequate ventila- tion–perfusion (V
. /Q
. ) ratio. In different areas of the lung, the (V
. /Q
. ) ratio varies. Alterations in perfusion may occur with a change in the pulmonary artery pressure, alveolar pressure, or gravity. Airway blockages, local changes in compliance, and gravity may alter ventilation. (V
. /Q
. ) imbalance occurs as a result of inadequate ventila- tion, inadequate perfusion, or both. There are four possible (V
. /Q
. ) states in the lung: normal (V
. /Q
. ) ratio, low (V
. /Q
. ) ra- tio (shunt), high (V
. /Q
. ) ratio (dead space), and absence of ventilation and perfusion (silent unit) (Chart 21-2). (V
. /Q
. ) imbalance causes shunting of blood, resulting in hypoxia (low level of cellular oxygen). Shunting appears to be the main cause of hypoxia after thoracic or abdominal surgery
Table 21-1 LUNG VOLUMES AND LUNG CAPACITIES Term Symbol Description Normal Value Significance Lung Volumes* Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume
Lung Capacities Vital capacity
Inspiratory capacity
Functional residual capacity
Total lung capacity
VT or TV
IRV
ERV
RV
VC
IC
FRC
TLC
500 mL or 5–10 mL/kg
3000 mL
1100 mL
1200 mL
4600 mL
3500 mL
2300 mL
5800 mL
The tidal volume may not vary, even with severe disease.
Expiratory reserve volume is decreased with restrictive conditions, such as obesity, ascites, pregnancy. Residual volume may be increased with obstructive disease.
A decrease in vital capacity may be found in neuromuscular disease, generalized fatigue, atelectasis, pulmonary edema, COPD, and obesity. A decrease in inspiratory capacity may indicate restrictive disease. May also be decreased in obesity. Functional residual capacity may be increased with COPD and decreased in ARDS and obesity. Total lung capacity may be decreased with restrictive disease (atelectasis, pneumonia) and increased in COPD.
The volume of air inhaled and exhaled with each breath The maximum volume of air that can be inhaled after a normal inhalation
The maximum volume of air that can be exhaled forcibly after a normal exhalation
The volume of air remaining in the lungs after a maximum exhalation
The maximum volume of air exhaled from the point of maximum inspiration VC TV IRV ERV
The maximum volume of air inhaled after normal expiration IC TV IRV The volume of air remaining in the lungs after a normal expiration FRV ERV RV The volume of air in the lungs after a maximum inspiration TLC TV IRV ERV RV
- Values for healthy men; women are 20–25% less. ARDS, acute respiratory distress syndrome; COPD, chronic obstructed pulmonary disease.
Chapter 21 Assessment of Respiratory Function 493
When a gas is exposed to a liquid, the gas dissolves in the liquid until an equilibrium is reached. The dissolved gas also exerts a partial pressure. At equilibrium, the partial pressure of the gas in the liquid is the same as the partial pressure of the gas in the gaseous mixture. Oxygenation of venous blood in the lung illustrates this point. In the lung, venous blood and alveolar oxygen are separated by a very thin alveolar membrane. Oxygen diffuses across this membrane to dissolve in the blood until the partial pressure of oxygen in the blood is the same as that in the alveoli (104 mm Hg). However, be- cause carbon dioxide is a by-product of oxidation in the cells, venous blood contains carbon dioxide at a higher partial pressure than that in the alveolar gas. In the lung, carbon dioxide diffuses out of venous blood into the alveolar gas. At equilibrium, the partial pressure of carbon dioxide in the blood and in alveolar gas is the same (40 mm Hg). The changes in partial pressure are shown in Figure 21-5.
Effects of Pressure on Oxygen Transport
Oxygen and carbon dioxide are transported simultaneously either dissolved in blood or combined with hemoglobin in red blood cells. Each 100 mL of normal arterial blood car-
ries 0.3 mL of oxygen physically dissolved in the plasma and 20 mL of oxygen in combination with hemoglobin. Large amounts of oxygen can be transported in the blood because oxygen combines easily with hemoglobin to form oxyhemo- globin: O 2 Hgb 4 HgbO (^2)
The volume of oxygen physically dissolved in the plasma is measured by the partial pressure of oxygen in the arteries (PaO 2 ). The higher the PaO 2 , the greater the amount of oxygen dissolved. For example, at a PaO 2 of 10 mm Hg, 0. mL of oxygen is dissolved in 100 mL of plasma. At PaO 2 of 20 mm Hg, twice this amount is dissolved in plasma, and at PaO 2 of 100 mm Hg, 10 times this amount is dissolved. Therefore, the amount of dissolved oxygen is directly pro- portional to the partial pressure, regardless of how high the oxygen pressure becomes. The amount of oxygen that combines with hemoglobin depends on both the amount of hemoglobin in the blood and on PaO 2 , but only up to a PaO 2 of about 150 mm Hg. This is measured as O 2 saturation (SaO 2 ), the percentage of the O 2 that could be carried if all the hemoglobin held the maximum possible amount of O 2. When the PaO 2 is 150 mm Hg, hemoglobin is 100% saturated and does not combine with any additional oxygen. When hemoglobin is 100% saturated, 1 g of hemoglobin combines with 1.34 mL of oxy- gen. Therefore, in a person with 14 g/dL of hemoglobin, each 100 mL of blood contains about 19 mL of oxygen as- sociated with hemoglobin. If the PaO 2 is less than 150 mm Hg, the percentage of hemoglobin saturated with oxygen decreases. For example, at a PaO 2 of 100 mm Hg (normal value), saturation is 97%; at a PaO 2 of 40 mm Hg, satura- tion is 70%.
Oxyhemoglobin Dissociation Curve The oxyhemoglobin dissociation curve (Chart 21-4) shows the relationship between the partial pressure of oxygen (PaO 2 ) and the percentage of saturation of oxygen (SaO 2 ). The percentage of saturation can be affected by carbon dioxide, hydrogen ion concentration, temperature, and 2,3- diphosphoglycerate. An increase in these factors shifts the curve to the right, so that less oxygen is picked up in the lungs, but more oxygen is released to the tissues, if PaO 2 is unchanged. A decrease in these factors causes the curve to shift to the left, making the bond between oxygen and he- moglobin stronger. If the PaO 2 is still unchanged, more oxy- gen is picked up in the lungs, but less oxygen is given up to the tissues. The unusual shape of the oxyhemoglobin disso- ciation curve is a distinct advantage to the patient for two reasons:
- If the PaO 2 decreases from 100 to 80 mm Hg as a re- sult of lung disease or heart disease, the hemoglobin of the arterial blood remains almost maximally satu- rated (94%), and the tissues do not suffer from hy- poxia.
- When the arterial blood passes into tissue capillaries and is exposed to the tissue tension of oxygen (about 40 mm Hg), hemoglobin gives up large quantities of oxygen for use by the tissues. With a normal value for PaO 2 (80 to 100 mm Hg) and SaO 2 (95% to 98%), there is a 15% margin of excess oxygen
Air into the lungs
Pulmonary Capillary
Abbreviation
Venous system blood (Desaturated)
Arterial system blood (Oxygenated)
= alveolar = arterial = venous = partial pressure = oxygen = carbon dioxide = nitrogen = water vapor
A a v P
158 mm Hg 0.3 mm Hg 596 mm Hg 5.7 mm Hg
97 mm Hg 40 mm Hg
40 mm Hg 46 mm Hg
100 mm Hg 40 mm Hg 47 mm Hg 573 mm Hg
Air in the alveolus
PO 2 PCO 2 PN 2
N 2 H 2 O
CO 2
O 2
CO
CO 2
PAO 2
PvO 2 PvCO 2
PAN 2
PAH 2 O
PACO (^2)
O 2
PaO (^2) PaCO (^2) O 2
PH 2 O
Figure 21-5 Changes occur in the partial pressure of gases dur- ing respiration. These values vary as a result of the exchange of oxygen and carbon dioxide and the changes that occur in their partial pressures as venous blood flows through the lungs.
Chart 21-3 • Partial Pressure Abbreviations
P pressure PO 2 partial pressure of oxygen PCO 2 partial pressure of carbon dioxide PAO 2 partial pressure of alveolar oxygen PACO 2 partial pressure of alveolar carbon dioxide PaO 2 partial pressure of arterial oxygen PaCO 2 partial pressure of arterial carbon dioxide Pv–O 2 partial pressure of venous oxygen Pv–CO 2 partial pressure of venous carbon dioxide P 50 partial pressure of oxygen when the hemoglobin is 50% saturated
494 Unit 5 Gas Exchange and Respiratory Function
available to the tissues. With a normal hemoglobin level of 15 mg/dL and a PaO 2 level of 40 mm Hg (SaO 2 75%), there is adequate oxygen available for the tissues but no reserve for physiologic stresses that increase tissue oxygen demand. If a serious incident occurs (eg, bronchospasm, aspiration, hypotension, or cardiac dysrhythmias) that reduces the in- take of oxygen from the lungs, tissue hypoxia results. An important consideration in the transport of oxygen is cardiac output, which determines the amount of oxygen de- livered to the body and affects lung and tissue perfusion. If the cardiac output is normal (5 L/min), the amount of oxy- gen delivered to the body per minute is normal. Under nor- mal conditions, only 250 mL of oxygen is used per minute, which is approximately 25% of available oxygen. The rest of the oxygen returns to the right side of the heart, and the PaO 2 of venous blood drops from 80 to 100 mm Hg to about 40 mm Hg. If cardiac output falls, however, the amount of oxygen delivered to the tissues also falls and may be inade- quate to meet the body’s needs.
Carbon Dioxide Transport
At the same time that oxygen diffuses from the blood into the tissues, carbon dioxide diffuses from tissue cells to blood and is transported to the lungs for excretion. The amount of carbon dioxide in transit is one of the major determinants of the acid–base balance of the body. Normally, only 6% of the venous carbon dioxide is removed in the lungs, and enough remains in the arterial blood to exert a pressure of
40 mm Hg. Most of the carbon dioxide (90%) is carried by red blood cells; the small portion (5%) that remains dis- solved in the plasma (partial pressure of carbon dioxide [PCO 2 ]) is the critical factor that determines carbon diox- ide movement in or out of the blood. Although the many processes involved in respiratory gas transport seem to occur in intermittent stages, the changes are rapid, simultaneous, and continuous.
Neurologic Control of Ventilation Resting respiration is the result of cyclic excitation of the respiratory muscles by the phrenic nerve. The rhythm of breathing is controlled by respiratory centers in the brain. The inspiratory and expiratory centers in the medulla ob- longata and pons control the rate and depth of ventilation to meet the body’s metabolic demands. The apneustic center in the lower pons stimulates the in- spiratory medullary center to promote deep, prolonged in- spirations. The pneumotaxic center in the upper pons is thought to control the pattern of respirations. Several groups of receptor sites assist in the brain’s con- trol of respiratory function. The central chemoreceptors, lo- cated in the medulla, respond to chemical changes in the cerebrospinal fluid, which result from chemical changes in the blood. These receptors respond to an increase or de- crease in the pH and convey a message to the lungs to change the depth and then the rate of ventilation to correct the imbalance. The peripheral chemoreceptors are located in the aortic arch and the carotid arteries and respond first to changes in PaO 2 , then to partial pressure of carbon diox- ide (PaCO 2 ) and pH. The Hering-Breuer reflex is activated by stretch receptors in the alveoli. When the lungs are dis- tended, inspiration is inhibited; as a result, the lungs do not become overdistended. In addition, proprioceptors in the muscles and joints respond to body movements, such as ex- ercise, causing an increase in ventilation. Thus, range-of- motion exercises in an immobile patient stimulate breath- ing. Baroreceptors, also located in the aortic and carotid bodies, respond to an increase or decrease in arterial blood pressure and cause reflex hypoventilation or hyperventila- tion.
Gerontologic Considerations
A gradual decline in respiratory function begins in early to middle adulthood and affects the structure and function of the respiratory system. The vital capacity of the lungs and strength of the respiratory muscles peak between 20 and 25 years of age and decrease thereafter. With aging (40 years and older), changes occur in the alveoli that reduce the sur- face area available for the exchange of oxygen and carbon dioxide. At approximately 50 years of age, the alveoli begin to lose elasticity. A decrease in vital capacity occurs with loss of chest wall mobility, which restricts the tidal flow of air. The amount of respiratory dead space increases with age. These changes result in a decreased diffusion capacity for oxygen with increasing age, producing lower oxygen lev- els in the arterial circulation. Elderly people have a de- creased ability to rapidly move air in and out of the lungs. Gerontologic changes in the respiratory system are sum- marized in Table 21-2. Despite these changes, in the ab- sence of chronic pulmonary disease, elderly people are able
Chart 21-4 • Oxyhemoglobin Dissociation Curve
The oxyhemoglobin dissociation curve is marked to show three oxygen levels:
- Normal levels—PaO 2 above 70 mm Hg
- Relatively safe levels—PaO 2 45 to 70 mm Hg
- Dangerous levels—PaO 2 below 40 mm Hg The normal (middle) curve (N) shows that 75% saturation occurs at a PaO 2 of 40 mm Hg. If the curve shifts to the right (R), the same saturation (75%) occurs at the higher PaO 2 of 57 mm Hg. If the curve shifts to the left (L), 75% saturation occurs at a PaO 2 of 25 mm Hg.
Shift to left Hgb affinity for O 2
Shift to right Hgb affinity for O 2
L N R
L N R
Partial pressure O 2 (mm Hg)
O
Sa
tu
ra
tion (%)
2
100 90 80 70 60 50 40 30 20 10
10 20 30 40 50 60 70 80 90 100
496 Unit 5 Gas Exchange and Respiratory Function
sound heard (usually on inspiration) when someone is breathing through a partially blocked upper airway is called stridor. The presence of both inspiratory and expiratory wheezing usually signifies asthma if the patient does not have heart failure. Because dyspnea can occur with other disorders (eg, cardiac disease, anaphylactic reactions, severe anemia), these disorders also need to be considered when obtaining the patient’s health history (Davis & Holliday, 2005). The circumstance that produces the dyspnea must be de- termined. Therefore, it is important to ask the patient the following questions:
- How much exertion triggers shortness of breath? Does it occur at rest? With exercise? Running? Climbing stairs?
- Is there an associated cough?
- Is the shortness of breath related to other symptoms?
- Was the onset of shortness of breath sudden or gradual?
- At what time of day or night does the shortness of breath occur?
- Is the shortness of breath worse when laying flat?
- Is the shortness of breath worse while walking? If so, when walking how far? How fast?
- How severe is the shortness of breath? On a scale of 1 to 10, if 1 is breathing without any effort and 10 is breathing that is as difficult as it could possibly be, how hard is it to breathe? It is especially important to assess the patient’s rating of the intensity of breathlessness, the effort required to breathe, and the severity of the breathlessness or dyspnea. Patients use a variety of terms and phrases to describe breathlessness, and the nurse needs to clarify what terms are most familiar to the patient and what these terms mean. Vi- sual analogue or other scales can be used to assess changes in the severity of dyspnea over time (Dorman, Byrne & Ed- wards, 2007; Porth & Matfin, 2009).
Cough
Cough is a reflex that protects the lungs from the accumu- lation of secretions or the inhalation of foreign bodies. Its presence or absence can be a diagnostic clue because some disorders cause coughing and others suppress it. The cough reflex may be impaired by weakness or paralysis of the res- piratory muscles, prolonged inactivity, the presence of a na- sogastric tube, or depressed function of the medullary cen- ters in the brain (eg, anesthesia, brain disorders) (Irwin, Baumann, Bolser, et al., 2006; Porth & Matfin, 2009). Cough results from irritation of the mucous membranes anywhere in the respiratory tract. The stimulus that pro- duces a cough may arise from an infectious process or from an airborne irritant, such as smoke, smog, dust, or a gas. A persistent and frequent cough can be exhausting and cause pain. Cough may indicate serious pulmonary disease or a va- riety of other problems as well, including cardiac disease, medication reactions (eg, amiodarone [Cordarone], an- giotensin-converting enzyme [ACE] inhibitors), smoking, and gastroesophageal reflux disease (Irwin, et al., 2006). To help determine the cause of the cough, the nurse de- scribes the cough: dry, hacking, brassy, wheezing, loose, or severe. A dry, irritative cough is characteristic of an upper respiratory tract infection of viral origin, or it may be a side effect of ACE inhibitor therapy. An irritative, high-pitched cough can be caused by laryngotracheitis. A brassy cough is
the result of a tracheal lesion, while a severe or changing cough may indicate bronchogenic carcinoma. Pleuritic chest pain that accompanies coughing may indicate pleural or chest wall (musculoskeletal) involvement. The nurse inquires about the onset and time of cough- ing. Coughing at night may indicate the onset of left-sided heart failure or bronchial asthma. A cough in the morning with sputum production may indicate bronchitis. A cough that worsens when the patient is supine suggests postnasal drip (rhinosinusitis). Coughing after food intake may indi- cate aspiration of material into the tracheobronchial tree. A cough of recent onset is usually from an acute infection. A persistent cough may affect a patient’s quality of life and may produce embarrassment, exhaustion, inability to sleep, and pain. Therefore, the nurse should explore the ef- fect of a chronic cough on the patient and the patient’s view about the significance of the cough and its effect on his or her life. Violent coughing causes bronchial spasm, obstruction, and further irritation of the bronchi and may result in syn- cope (fainting). A severe, repeated, or uncontrolled cough that is nonproductive is exhausting and potentially harmful.
Sputum Production A patient who coughs long enough almost invariably pro- duces sputum. Sputum production is the reaction of the lungs to any constantly recurring irritant. It also may be as- sociated with a nasal discharge. The nature of the sputum is often indicative of its cause. A profuse amount of purulent sputum (thick and yellow, green, or rust-colored) or a change in color of the sputum is a common sign of a bacte- rial infection. Thin, mucoid sputum frequently results from viral bronchitis. A gradual increase of sputum over time may occur with chronic bronchitis or bronchiectasis. Pink- tinged mucoid sputum suggests a lung tumor. Profuse, frothy, pink material, often welling up into the throat, may indicate pulmonary edema. Foul-smelling sputum and bad breath point to the presence of a lung abscess, bronchiecta- sis, or an infection caused by fusospirochetal or other anaer- obic organisms.
Chest Pain Chest pain or discomfort may be associated with pulmonary or cardiac disease. Chest pain associated with pulmonary conditions may be sharp, stabbing, and intermittent, or it may be dull, aching, and persistent. The pain usually is felt on the side where the pathologic process is located, but it may be referred elsewhere—for example, to the neck, back, or abdomen. Chest pain may occur with pneumonia, pulmonary em- bolism with lung infarction, pleurisy, or as a late symptom of bronchogenic carcinoma. In carcinoma, the pain may be dull and persistent because the cancer has invaded the chest wall, mediastinum, or spine. Lung disease does not always cause thoracic pain because the lungs and the visceral pleura lack sensory nerves and are insensitive to pain stimuli. However, the parietal pleura has a rich supply of sensory nerves that are stimulated by in- flammation and stretching of the membrane. Pleuritic pain from irritation of the parietal pleura is sharp and seems to “catch” on inspiration; patients often describe it as being
Chapter 21 Assessment of Respiratory Function 497
“like the stabbing of a knife.” Patients are more comfortable when they lay on the affected side because this splints the chest wall, limits expansion and contraction of the lung, and reduces the friction between the injured or diseased pleurae on that side. Pain associated with cough may be re- duced manually by splinting the rib cage. The nurse assesses the quality, intensity, and radiation of pain and identifies and explores precipitating factors and their relationship to the patient’s position. In addition, it is important to assess the relationship of pain to the inspira- tory and expiratory phases of respiration.
Wheezing
Wheezing is a high-pitched, musical sound heard mainly on expiration (asthma) or inspiration (bronchitis). It is often the major finding in a patient with bronchoconstriction or airway narrowing. Rhonchi are low pitched continuous sounds heard over the lungs in partial airway obstruction. Depending on their location and severity, these sounds may be heard with or without a stethoscope.
Hemoptysis
Hemoptysis (expectoration of blood from the respiratory tract) is a symptom of both pulmonary and cardiac disor- ders. The onset of hemoptysis is usually sudden, and it may be intermittent or continuous. Signs, which vary from blood-stained sputum to a large, sudden hemorrhage, always merit investigation. The most common causes are:
- Pulmonary infection
- Carcinoma of the lung
- Abnormalities of the heart or blood vessels
- Pulmonary artery or vein abnormalities
- Pulmonary embolus and infarction Diagnostic evaluation to determine the cause includes chest x-ray, chest angiography, and bronchoscopy. A careful history and physical examination are necessary to identify the underlying disorder, irrespective of whether the bleed- ing involved a small amount of blood in the sputum or a massive hemorrhage. The amount of blood produced is not always proportional to the seriousness of the cause. First, it is important to determine the source of the bleeding—the gums, nasopharynx, lungs, or stomach. The nurse may be the only witness to the episode. When docu- menting the bleeding episode, the nurse considers the fol- lowing points:
- Bloody sputum from the nose or the nasopharynx is usually preceded by considerable sniffing, with blood possibly appearing in the nose.
- Blood from the lung is usually bright red, frothy, and mixed with sputum. Initial symptoms include a tickling sensation in the throat, a salty taste, a burning or bub- bling sensation in the chest, and perhaps chest pain, in which case the patient tends to splint the bleeding side. The term hemoptysis is reserved for the coughing up of blood arising from a pulmonary hemorrhage. This blood has an alkaline pH (greater than 7.0).
- If the hemorrhage is in the stomach, the blood is vom- ited (hematemesis) rather than coughed up. Blood that has been in contact with gastric juice is some- times so dark that it is referred to as “coffee ground emesis.” This blood has an acid pH (less than 7.0).
Past Health, Family, and Social History After exploring the current problem, the nurse obtains a brief history of events and conditions that could affect cur- rent health status. Specific questions are asked about child- hood illnesses, immunizations, chronic medical conditions, injuries, hospitalizations, surgeries, allergies, and current medications (including over-the-counter medications and herbal remedies). Since many lung disorders are related to or exacerbated by tobacco smoke, smoking history (includ- ing exposure to second-hand smoke) is also obtained. Smoking history is usually expressed in pack-years, which is number of packs of cigarettes smoked per day times the number of years the patient smoked. It is important to find out if (and when) the patient quit smoking or is still smok- ing. The nurse assesses for risk factors and genetic factors that may contribute to the patient’s lung condition (Charts 21-5 and 21-6). In addition, psychosocial factors that may affect the pa- tient are explored (Chart 21-7). These factors include anx- iety, role changes, family relationships, financial problems, employment status, and the strategies the patient uses to cope with them. Many respiratory diseases are chronic and progressively debilitating and disabling. It is important that the patient with a respiratory disorder understand the con- dition and be familiar with necessary self-care interven- tions. The nurse evaluates these factors over time and pro- vides education as needed.
Physical Assessment of the
Respiratory System
General Appearance The patient’s general appearance may give clues to respira- tory status. In particular, the nurse inspects for clubbing of the fingers and notes skin color.
Clubbing of the Fingers Clubbing of the fingers is a sign of lung disease that is found in patients with chronic hypoxic conditions, chronic lung infections, or malignancies of the lung (Bickley, 2007). This finding may be manifested initially as sponginess of the nail bed and loss of the nail bed angle (Fig. 21-6).
Cyanosis Cyanosis, a bluish coloring of the skin, is a very late indica- tor of hypoxia. The presence or absence of cyanosis is de- termined by the amount of unoxygenated hemoglobin in the blood. Cyanosis appears when there is at least 5 g/dL of unoxygenated hemoglobin. A patient with a hemoglobin
- Smoking (the single most important contributor to lung disease)
- Exposure to secondhand smoke
- Personal or family history of lung disease
- Genetic makeup
- Exposure to allergens and environmental pollutants
- Exposure to certain recreational and occupational hazards
CHART
Risk Factors for Respiratory
Disease
Chapter 21 Assessment of Respiratory Function 499
Nose and Sinuses
The nurse inspects the external nose for lesions, asymmetry, or inflammation and then asks the patient to tilt the head back- ward. Gently pushing the tip of the nose upward, the nurse ex- amines the internal structures of the nose, inspecting the mu- cosa for color, swelling, exudate, or bleeding. The nasal mucosa is normally redder than the oral mucosa. It may ap- pear swollen and hyperemic if the patient has a common cold, but in allergic rhinitis, the mucosa appears pale and swollen. Next, the nurse inspects the septum for deviation, perfo- ration, or bleeding. Most people have a slight degree of sep- tal deviation, but actual displacement of the cartilage into either the right or left side of the nose may produce nasal obstruction. Such deviation usually causes no symptoms. While the head is still tilted back, the nurse inspects the inferior and middle turbinates. In chronic rhinitis, nasal polyps may develop between the inferior and middle turbinates; they are distinguished by their gray appearance. Unlike the turbinates, they are gelatinous and freely movable. Next, the nurse may palpate the frontal and maxillary si- nuses for tenderness (Fig. 21-7). Using the thumbs, the
nurse applies gentle pressure in an upward fashion at the supraorbital ridges (frontal sinuses) and in the cheek area adjacent to the nose (maxillary sinuses). Tenderness in ei- ther area suggests inflammation. The frontal and maxillary sinuses can be inspected by transillumination (passing a strong light through a bony area, such as the sinuses, to in- spect the cavity; Fig. 21-8). If the light fails to penetrate, the cavity likely contains fluid or pus.
Mouth and Pharynx After the nasal inspection, the nurse assesses the mouth and pharynx, instructing the patient to open the mouth wide and take a deep breath. Usually this flattens the pos- terior tongue and briefly allows a full view of the anterior and posterior pillars, tonsils, uvula, and posterior pharynx (see Chapter 35, Fig. 35-2). The nurse inspects these struc- tures for color, symmetry, and evidence of exudate, ulcera- tion, or enlargement. If a tongue blade is needed to depress the tongue to visualize the pharynx, it is pressed firmly be- yond the midpoint of the tongue to avoid a gagging re- sponse.
Trachea Next, the position and mobility of the trachea are noted by direct palpation. This is performed by placing the thumb and index finger of one hand on either side of the trachea just above the sternal notch. The trachea is highly sensi- tive, and palpating too firmly may trigger a coughing or gag- ging response. The trachea is normally in the midline as it enters the thoracic inlet behind the sternum, but it may be deviated by masses in the neck or mediastinum. Pleural or pulmonary disorders, such as a pneumothorax, may also dis- place the trachea.
Lower Respiratory Structures and Breathing Assessment of the lower respiratory structures includes inspec- tion, palpation, percussion, and auscultation of the thorax.
Figure 21-6 Clubbed finger. In clubbing, the distal phalanx of each finger is rounded and bulbous. The nail plate is more con- vex, and the angle between the plate and the proximal nail fold increases to 180 degrees or more. The proximal nail fold, when palpated, feels spongy or floating. Among the many causes are chronic hypoxia and lung cancer.
Figure 21-7 Technique for palpating the frontal sinuses at left and the maxillary sinuses at right.
Figure 21-8 At left, the nurse positions the light source for tran- sillumination of the frontal sinus. At right, the nurse shields the patient’s brow and shines the light. In normal conditions (a dark- ened room), the light should shine through the tissues and ap- pear as a reddish glow (above the nurse’s hand) over the sinus.
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500 Unit 5 Gas Exchange and Respiratory Function
Thoracic Inspection
Inspection of the thorax provides information about the musculoskeletal structure, the patient’s nutritional status, and the respiratory system. The nurse observes the skin over the thorax for color and turgor and for evidence of loss of subcutaneous tissue. It is important to note asymmetry, if present. In recording or reporting the findings, anatomic landmarks are used as points of reference (Chart 21-8).
Chest Configuration. Normally, the ratio of the anteropos- terior diameter to the lateral diameter is 1:2. However, there are four main deformities of the chest associated with respiratory disease that alter this relationship: barrel chest, funnel chest (pectus excavatum), pigeon chest (pectus car- inatum), and kyphoscoliosis.
BARREL CHEST. Barrel chest occurs as a result of overinflation of the lungs. There is an increase in the anteroposterior diam- eter of the thorax. In a patient with emphysema, the ribs are more widely spaced and the intercostal spaces tend to bulge on expiration. The appearance of the patient with advanced emphysema is thus quite characteristic and often allows the observer to detect its presence easily, even from a distance.
FUNNEL CHEST ( PECTUS EXCAVATUM ). Funnel chest occurs when there is a depression in the lower portion of the ster- num. This may compress the heart and great vessels, result- ing in murmurs. Funnel chest may occur with rickets or Marfan’s syndrome.
PIGEON CHEST (PECTUS CARINATUM). A pigeon chest occurs as a result of displacement of the sternum. There is an in- crease in the anteroposterior diameter. This may occur with rickets, Marfan’s syndrome, or severe kyphoscoliosis.
KYPHOSCOLIOSIS. Kyphoscoliosis is characterized by eleva- tion of the scapula and a corresponding S-shaped spine. This deformity limits lung expansion within the thorax. It may occur with osteoporosis and other skeletal disorders that affect the thorax.
Breathing Patterns and Respiratory Rates. Observing the rate and depth of respiration is a simple but important aspect of assessment. The normal adult who is resting comfortably takes 12 to 18 breaths per minute. Except for occasional sighs, respirations are regular in depth and rhythm. This nor- mal pattern is described as eupnea. The rate and depth of various patterns of respiration are presented in Table 21-3. Certain patterns of respiration are characteristic of spe- cific disease states. Respiratory rhythms and their devia- tion from normal are important observations that the nurse reports and documents. Temporary pauses of breath- ing, or apnea , may be noted. When apneas occur repeat- edly during sleep, secondary to transient upper airway blockage, the condition is called obstructive sleep apnea. In thin people, it is quite normal to note a slight retraction of the intercostal spaces during quiet breathing. Bulging of the intercostal spaces during expiration implies obstruc- tion of expiratory airflow, as in emphysema. Marked re- traction on inspiration, particularly if asymmetric, implies blockage of a branch of the respiratory tree. Asymmetric bulging of the intercostal spaces, on one side or the other, is created by an increase in pressure within the hemitho- rax. This may be a result of air trapped under pressure within the pleural cavity, where it is not normally present
(pneumothorax), or the pressure of fluid within the pleu- ral space (pleural effusion).
Thoracic Palpation The nurse palpates the thorax for tenderness, masses, lesions, respiratory excursion, and vocal fremitus. If the patient has reported an area of pain or if lesions are apparent, the nurse performs direct palpation with the fingertips (for skin lesions and subcutaneous masses) or with the ball of the hand (for deeper masses or generalized flank or rib discomfort).
Respiratory Excursion. Respiratory excursion is an estima- tion of thoracic expansion and may disclose significant in- formation about thoracic movement during breathing. The nurse assesses the patient for range and symmetry of excur- sion. For anterior assessment, the nurse places the thumbs along the costal margin of the chest wall and instructs the patient to inhale deeply. The nurse observes movement of the thumbs during inspiration and expiration. This move- ment is normally symmetric (Bickley, 2007). Posterior assessment is performed by placing the thumbs adjacent to the spinal column at the level of the tenth rib (Fig. 21-9). The hands lightly grasp the lateral rib cage. Sliding the thumbs medially about 2.5 cm (1 inch) raises a small skin fold between the thumbs. The patient is in- structed to take a full inspiration and to exhale fully. The nurse observes for normal flattening of the skin fold and feels the symmetric movement of the thorax. Decreased chest excursion may be caused by chronic fi- brotic disease. Asymmetric excursion may be due to splint- ing secondary to pleurisy, fractured ribs, trauma, or unilat- eral bronchial obstruction (Bickley, 2007).
Tactile Fremitus. Sound generated by the larynx travels distally along the bronchial tree to set the chest wall in res- onant motion. This is especially true of consonant sounds. The detection of the resulting vibration on the chest wall by touch is called tactile fremitus. Normal fremitus is widely varied. It is influenced by the thickness of the chest wall, especially if that thickness is muscular. However, the increase in subcutaneous tissue asso- ciated with obesity may also affect fremitus. Lower-pitched sounds travel better through the normal lung and produce greater vibration of the chest wall. Therefore, fremitus is more pronounced in men than in women because of the deeper male voice. Normally, fremitus is most pronounced where the large bronchi are closest to the chest wall and least palpable over the distant lung fields. Therefore, it is most palpable in the upper thorax, anteriorly and posteriorly. The patient is asked to repeat “ninety-nine” or “one, two, three,” or “eee, eee, eee” as the nurse’s hands move down the patient’s thorax. The vibrations are detected with the palmar surfaces of the fingers and hands, or the ulnar aspect of the ex- tended hands, on the thorax. The hand or hands are moved in sequence down the thorax. Corresponding areas of the tho- rax are compared (Fig. 21-10). Bony areas are not tested. Air does not conduct sound well, but a solid substance such as tissue does, provided that it has elasticity and is not com- pressed. Therefore, an increase in solid tissue per unit volume of lung enhances fremitus, and an increase in air per unit vol- ume of lung impedes sound. Patients with emphysema, which results in the rupture of alveoli and trapping of air, exhibit al- most no tactile fremitus. A patient with consolidation of a
502 Unit 5 Gas Exchange and Respiratory Function
lobe of the lung from pneumonia has increased tactile fremi- tus over that lobe. Air in the pleural space does not conduct sound (Bickley, 2007).
Thoracic Percussion
Percussion sets the chest wall and underlying structures in motion, producing audible and tactile vibrations. The nurse uses percussion to determine whether underlying tissues are filled with air, fluid, or solid material. Percussion also is used to estimate the size and location of certain structures within the thorax (eg, diaphragm, heart, liver). Percussion usually begins with the posterior thorax. Ideally, the patient is in a sitting position with the head flexed forward and the arms crossed on the lap. This position separates the scapulae widely and exposes more lung area for assessment. The nurse percusses across each shoulder top, locating the 5-cm width of resonance overlying the lung apices (Fig. 21-11). Then the nurse proceeds down the posterior thorax, percussing sym- metric areas at intervals of 5 to 6 cm (2 to 2.5 inches). The mid- dle finger is positioned parallel to the ribs in the intercostal space; the finger is placed firmly against the chest wall before it is struck with the middle finger of the opposite hand. Bony structures (scapulae or ribs) are not percussed.
Percussion over the anterior chest is performed with the patient in an upright position with shoulders arched back- ward and arms at the side. The nurse begins in the supra- clavicular area and proceeds downward, from one intercostal space to the next. In the female patient, it may be necessary to displace the breasts for an adequate examination. Dullness noted to the left of the sternum between the third and fifth intercostal spaces is a normal finding, because that is the lo- cation of the heart. Similarly, there is a normal span of liver dullness in the right thorax, from the fifth intercostal space to the right costal margin at the midclavicular line (Bickley, 2007). The anterior and lateral thorax is examined with the pa- tient in a supine position. If the patient cannot sit up, per- cussion of the posterior thorax is performed with the patient positioned on the side. Dullness over the lung occurs when air-filled lung tissue is replaced by fluid or solid tissue. Table 21-4 reviews per- cussion sounds and their characteristics.
Diaphragmatic Excursion. The normal resonance of the lung stops at the diaphragm. The position of the diaphragm is different during inspiration and expiration.
Table 21-3 RATES AND DEPTHS OF RESPIRATION Type Description Eupnea Normal, breathing at 12–18 breaths/min
Bradypnea Slower than normal rate (10 breaths/min), with normal depth and regular rhythm Associated with increased intracranial pressure, brain injury, and drug overdose
Tachypnea Rapid, shallow breathing 24 breaths/min Associated with pneumonia, pulmonary edema, metabolic acidosis, septicemia, severe pain, or rib fracture Hypoventilation Shallow, irregular breathing
Hyperpnea Increase depth of respirations Hyperventilation Increased rate and depth of breathing that results in decreased PaCO 2 level Inspiration and expiration are nearly equal in duration Called Kussmaul’s respiration if associated with diabetic ketoacidosis or renal origin
Apnea Period of cessation of breathing; time duration varies; apnea may occur briefly during other breathing disorders, such as with sleep apnea; life-threatening if sustained
Cheyne-Stokes Regular cycle where the rate and depth of breathing increase, then decrease until apnea (usually about 20 seconds) occurs Duration of apnea may vary and progressively lengthen; therefore, it is timed and reported Associated with heart failure and damage to the respiratory center (drug-induced, tumor, trauma)
Biot’s respiration Periods of normal breathing (3–4 breaths) followed by a varying period of apnea (usually 10–60 seconds) Also called cluster breathing Associated with some nervous system disorders
Chapter 21 Assessment of Respiratory Function 503
To assess the position and motion of the diaphragm, the nurse instructs the patient to take a deep breath and hold it while the maximal descent of the diaphragm is percussed. The point at which the percussion note at the midscapular line changes from resonance to dullness is marked with a pen. The patient is then instructed to exhale fully and hold it while the nurse again percusses downward to the dullness of the di-
aphragm. This point is also marked. The distance between the two markings indicates the range of motion of the diaphragm. Maximal excursion of the diaphragm may be as much as 8 to 10 cm (3 to 4 inches) in healthy, tall young men, but for most people it is usually 5 to 7 cm (2 to 2.75 inches). Normally, the diaphragm is about 2 cm (0.75 inches) higher on the right because of the position of the heart and the liver above and below the left and right segments of the di- aphragm, respectively. Decreased diaphragmatic excursion may occur with pleural effusion and emphysema. An in- crease in intra-abdominal pressure, as in pregnancy, obesity, or ascites, may account for a diaphragm that is positioned high in the thorax (Bickley, 2007).
Thoracic Auscultation Assessment concludes with auscultation of the anterior, posterior, and lateral thorax. Auscultation is useful in as- sessing the flow of air through the bronchial tree and in evaluating the presence of fluid or solid obstruction in the lung. The nurse auscultates for normal breath sounds, ad- ventitious sounds, and voice sounds. The nurse places the diaphragm of the stethoscope firmly against the chest wall as the patient breathes slowly and deeply through the mouth. Corresponding areas of the chest are auscultated in a systematic fashion from the apices to the bases and along midaxillary lines. The sequence of ausculta- tion and the positioning of the patient are similar to those used for percussion. It often is necessary to listen to two full inspirations and expirations at each anatomic location for valid interpretation of the sound heard. Repeated deep breaths may result in symptoms of hyperventilation (eg, lightheadedness); this is avoided by having the patient rest and breathe normally periodically during the examination.
Breath Sounds. Normal breath sounds are distin- guished by their location over a specific area of the lung and
Figure 21-9 Method for assessing posterior respiratory excur- sion. Place both hands posteriorly at the level of T9 or T10. Slide hands medially to pinch a small amount of skin between your thumbs. Observe for symmetry as the patient exhales fully fol- lowing a deep inspiration.
1 1
2 2
3 4 4
5 5
3
1 1
2 2 3 3
Figure 21-10 Palpation se- quence for tactile fremitus: pos- terior thorax ( left ) and anterior thorax ( right ).
