Pulmonary System

The objectives of this chapter are the following:

1 Provide a brief review of the structure and function of the pulmonary system

2 Give an overview of pulmonary evaluation, including physical examination and diagnostic testing

3 Describe pulmonary diseases and disorders, including clinical findings, medical-surgical management, and physical therapy intervention

Preferred Practice Patterns

The most relevant practice patterns for the diagnoses discussed in this chapter, based on the American Physical Therapy Association’s Guide to Physical Therapist Practice, second edition, are as follows:

• Impaired Aerobic Capacity/Endurance Associated with Deconditioning: 6B

• Impaired Ventilation, Respiration/Gas Exchange, and Aerobic Capacity/Endurance Associated with Airway Clearance Dysfunction: 6C

• Impaired Ventilation and Respiration/Gas Exchange Associated with Ventilatory Pump Dysfunction or Failure: 6E

• Impaired Ventilation and Respiration/Gas Exchange Associated with Respiratory Failure: 6F

• Impaired Ventilation, Respiration/Gas Exchange, and Aerobic Capacity/Endurance Associated with Respiratory Failure in the Neonate: 6G

Please refer to Appendix A for a complete list of the preferred practice patterns, as individual patient conditions are highly variable and other practice patterns may be applicable.

To safely and effectively provide exercise, bronchopulmonary hygiene program(s), or both to patients with pulmonary system dysfunction, physical therapists require an understanding of the pulmonary system and of the principles of ventilation and gas exchange. Ventilation is defined as gas (oxygen [O₂] and carbon dioxide [CO₂]) transport into and out of lungs, and respiration is defined as gas exchange across the alveolar-capillary and capillary-tissue interfaces. The term pulmonary primarily refers to the lungs, their airways, and their vascular system.¹

Body Structure and Function

Structure

The primary organs and muscles of the pulmonary system are outlined in Tables 4-1 and 4-2, respectively. A schematic of the pulmonary system within the thorax is presented in Figure 4-1.

TABLE 4-1

Structure and Function of Primary Organs of the Pulmonary System

Structure	Description	Function
Nose	Paired mucosal-lined nasal cavities supported by bone and cartilage	Conduit that filters, warms, and humidifies air entering lungs
Pharynx	Passageway that connects nasal and oral cavities to larynx, and oral cavity to esophagusSubdivisions naso-, oro-, and laryngopharynx	Conduit for air and foodFacilitates exposure of immune system to inhaled antigens
Larynx	Passageway that connects pharynx to tracheaOpening (glottis) covered by vocal folds or by the epiglottis during swallowing	Prevents food from entering the lower pulmonary tractVoice production
Trachea	Flexible tube composed of C-shaped cartilaginous rings connected posteriorly to the trachealis muscleDivides into the left and right main stem bronchi at the carina	Cleans, warms, and moistens incoming air
Bronchial tree	Right and left main stem bronchi subdivide within each lung into secondary bronchi, tertiary bronchi, and bronchioles, which contain smooth muscle	Warms and moistens incoming air from trachea to alveoliSmooth muscle constriction alters airflow
Lungs	Paired organs located within pleural cavities of the thoraxThe right lung has three lobes, and the left lung has two lobes	Contains air passageways distal to main stem bronchi, alveoli, and respiratory membranes
Alveoli	Microscopic sacs at end of bronchial tree immediately adjacent to pulmonary capillariesFunctional unit of the lung	Primary gas exchange siteSurfactant lines the alveoli to decrease surface tension and prevent complete closure during exhalation
Pleurae	Double-layered, continuous serous membrane lining the inside of the thoracic cavityDivided into parietal (outer) pleura and visceral (inner) pleura	Produces lubricating fluid that allows smooth gliding of lungs within the thoraxPotential space between parietal and visceral pleura

Data from Marieb E: Human anatomy and physiology, ed 3, Redwood City, Calif, 1995, Benjamin-Cummings; Moldover JR, Stein J, Krug PG: Cardiopulmonary physiology. In Gonzalez EG, Myers SJ, Edelstein JE et al: Downey & Darling’s physiological basis of rehabilitation medicine, ed 3, Philadelphia, 2001, Butterworth-Heinemann.

TABLE 4-2

Primary and Accessory Ventilatory Muscles with Associated Innervation

	Pulmonary Muscles	Innervation
Primary inspiratory muscles	Diaphragm	Phrenic nerve (C3-C5)
	External intercostals	Spinal segments T1-T9
Accessory inspiratory muscles	Trapezius	Cervical nerve (C1-C4), spinal part of cranial nerve XI
	Sternocleidomastoid	Spinal part of cranial nerve XI
	Scalenes	Cervical/brachial plexus branches (C3-C8, T1)
	Pectorals	Medial/lateral pectoral nerve (C5-C8, T1)
	Serratus anterior	Long thoracic nerve (C5-C7)
	Latissimus dorsi	Thoracodorsal nerve (C5-C8)
Primary expiratory muscles	Rectus abdominis	Spinal segments T5-T12
	External obliques	Spinal segments T7-T12
	Internal obliques	Spinal segments T8-T12
	Internal intercostals	Spinal segments T1-T9
Accessory expiratory muscles	Latissimus dorsi	Thoracodorsal nerve (C5-C8)

Data from Kendall FP, McCreary EK, editors: Muscles: testing and function, ed 3, Baltimore, 1983, Lippincott, Williams, and Wilkins; Rothstein JM, Roy SH, Wolf SL: The rehabilitation specialist’s handbook, ed 2, Philadelphia, 1998, FA Davis; DeTurk WE, Cahalin LP: Cardiovascular and pulmonary physical therapy: an evidence-based approach, New York, 2004, McGraw-Hill Medical Publishing Division.

FIGURE 4-1 A, Right lung positioned in the thorax. Bony landmarks assist in identifying normal right lung configuration. B, Anterior view of the lungs in the thorax in conjunction with bony landmarks. Left upper lobe is divided into apical and left lingula, which match the general position of the right upper and middle lobes. C, Posterior view of the lungs in conjunction with bony landmarks. (From Ellis E, Alison J, editors: Key issues in cardiorespiratory physiotherapy, Oxford, 1992, Butterworth-Heinemann, p 12.)

Clinical Tip

The compression of the abdominal contents can be observed with the protrusion of the abdomen. Clinicians use the term “belly breathing” to facilitate diaphragmatic breathing.

The contraction of the intercostal muscles results in two motions simultaneously: bucket and pump handle. The combined motions further increase the volume of the thorax. The overall increase in the volume of the thoracic cavity creates a negative intrathoracic pressure compared with outside the body. As a result, air is pulled into the body and lungs via the pulmonary tree, stretching the lung parenchyma, to equalize the pressures within the thorax with those outside the body.

Accessory muscles of inspiration, noted in Table 4-2, are generally not active during quiet breathing. Although not the primary actions of the individual muscles, their contractions can increase the depth and rate of ventilation during progressive activity by increasing the expansion of the thorax. Increased expansion results in greater negative pressures being generated and subsequent larger volumes of air entering the lungs.

Clinical Tip

In healthy lungs, depth of ventilation generally occurs before increases in rate.

Although inhalation is an active process, exhalation is a generally passive process. The muscles relax, causing a decrease in the thoracic volume while the lungs deflate to their natural resting state. The combined effects of these actions result in an increase of intrathoracic pressure and flow of air out of the lungs. Contraction of the primary and accessory muscles of exhalation, found in Table 4-2, results in an increase in intrathoracic pressure and a faster rate of decrease in thoracic size, which forces air out of the lungs. These motions are outlined schematically in Figure 4-2.^6,7

FIGURE 4-2 Respiratory mechanics (bucket and pump handle motions). (From Snell RS, editor: Clinical anatomy by regions, ed 9, Baltimore, 2012, Lippincott, Williams & Wilkins.)

In persons with primary or secondary chronic pulmonary health conditions, changes in tissue and mechanical properties in the pulmonary system can result in accessory muscle use being observed earlier in activity or may even be present at rest. Determination of the impairment(s) resulting in the observed activity limitation can help a clinician focus a plan of care. In addition, clinicians should consider the reversibility, or the degree to which the impairment can be improved, when determining a patient’s prognosis for improvement with physical therapy. If reversing a patient’s ventilatory impairments is unlikely, facilitation of accessory muscle use can be promoted during functional activities and strengthening of these accessory muscles (e.g., use of a four-wheeled rolling walker with a seat and accompanying arm exercises).

Clinical Tip

Patients with advanced pulmonary conditions may automatically assume positions to optimize accessory muscle use, such as forward leaning on their forearms (i.e., tripod posturing).

Gas Exchange.

Once air has reached the alveolar spaces, respiration or gas exchange can occur at the alveolar-capillary membrane. Diffusion of gases through the membrane is affected by the following:

• A concentration gradient in which gases will diffuse from areas of high concentration to areas of low concentration:

• Surface area, or the total amount of alveolar-capillary interface available for gas exchange (e.g., the breakdown of alveolar membranes that occurs in emphysema will reduce the amount of surface area available for gas exchange)

• The thickness of the barrier (membrane) between the two areas involved (e.g., retained secretions in the alveolar spaces will impede gas exchange through the membrane)

Ventilation and Perfusion Ratio.

Gas exchange is optimized when the ratio of air flow (ventilation ) to blood flow (perfusion ) approaches a 1 : 1 relationship. However, the actual ratio is 0.8 because alveolar ventilation is approximately equal to 4 L per minute and pulmonary blood flow is approximately equal to 5 L per minute.2,8,9

Gravity, body position, and cardiopulmonary dysfunction can influence this ratio. Ventilation is optimized in areas of least resistance. For example, when a person is in a sitting position, the upper lobes initially receive more ventilation than the lower lobes; however, the lower lobes have the largest net change in ventilation.

Perfusion is greatest in gravity-dependent areas. For example, when a person is in a sitting position, perfusion is the greatest at the base of the lungs; when a person is in a left side-lying position, the left lung receives the most blood.

A mismatch (inequality in the relationship between ventilation and perfusion) can occur in certain situations. Two terms associated with mismatch are dead space and shunt. Dead space occurs when ventilation is in excess of perfusion, as with a pulmonary embolus. A shunt occurs when perfusion is in excess of ventilation, as in alveolar collapse from secretion retention. These conditions are shown in Figure 4-3.

FIGURE 4-3 Ventilation and perfusion mismatch. A, Normal alveolar ventilation. B, Capillary shunt. C, Alveolar dead space.

Gas Transport.

O₂ is transported away from the lungs to the tissues in two forms: dissolved in plasma (PO₂) or chemically bound to hemoglobin on a red blood cell (oxyhemoglobin). As a by-product of cellular metabolism, CO₂ is transported away from the tissues to the lungs in three forms: dissolved in plasma (PCO₂), chemically bound to hemoglobin (carboxyhemoglobin), and as bicarbonate.

Approximately 97% of O₂ transported from the lungs is carried in chemical combination with hemoglobin. The majority of CO₂ transport, 93%, occurs in the combined forms of carbaminohemoglobin and bicarbonate. A smaller percentage, 3% of O₂ and 7% of CO_2, is transported in dissolved forms.¹⁰ Dissolved O₂ and CO₂ exert a partial pressure within the plasma and can be measured by sampling arterial, venous, or mixed venous blood.¹¹ See the Arterial Blood Gas section for further description of this process.

Evaluation

Pulmonary evaluation is composed of patient history, physical examination, and interpretation of diagnostic test results.

Patient History

In addition to the general chart review presented in Chapter 2, other relevant information regarding pulmonary dysfunction that should be ascertained from the chart review or patient interview is listed as follows^11–13:

• History of smoking, including packs per day or pack years (packs per day × number of years smoked) and the amount of time that smoking has been discontinued (if applicable)

• Presence, history, and amount of O₂ therapy at rest, with activity and at night

• Exposure to environmental or occupational toxins (e.g., asbestos)

• History of pneumonia, thoracic procedures, or surgery

• History of assisted ventilation or intubation with mechanical ventilation

• History or current reports of dyspnea either at rest or with exertion. Dyspnea is the subjective complaint of difficulty with respiration, also known as shortness of breath. A visual analog scale or ratio scale (Modified Borg scale) can be used to obtain a measurement of dyspnea. The American Thoracic Society Dyspnea Scale can be found in Table 4-3. Note: The abbreviation DOE represents “dyspnea on exertion”

TABLE 4-3

American Thoracic Society Dyspnea Scale

Grade	Degree
0	None	Not troubled with breathlessness except with strenuous exercise
1	Slight	Troubled by shortness of breath when hurrying on the level or walking up a slight hill
2	Moderate	Walks slower than people of the same age on the level because of breathlessness, or has to stop for breath when walking at own pace on the level
3	Severe	Stops for breath after walking about 100 yards or after a few minutes on the level
4	Very severe	Too breathless to leave the house or breathless when dressing or undressing

From Brooks SM: Surveillance for respiratory hazards, ATS News 8:12-16, 1982.

• Level of activity before admittance

• History of baseline sputum production, including color (e.g., yellow, green), consistency (e.g., thick, thin), and amount. Familiar or broad terms can be applied as units of measure for sputum (e.g., quarter-sized, tablespoon, or copious)

• Sleeping position and number of pillows used

Clinical Tip

Dyspnea also may be measured by counting the number of words a person can speak per breath. For example, a patient with one- to two-word dyspnea is noticeably more dyspneic than a person who can speak a full sentence per breath. Measurement of dyspnea can be used in goal writing (e.g., “Patient will ascend/descend 10 stairs with one rail with reported dyspnea < 2/10.”).

Physical Examination

The physical examination of the pulmonary system consists of inspection, auscultation, palpation, mediate percussion, and cough examination. Suggested guidelines for physical therapy intervention(s) that are based on examination findings and diagnostic test results are found at the end of this chapter.

Inspection

A wealth of information can be gathered by simple observation of the patient at rest and with activity. Physical observation should proceed in a systematic fashion and include the following:

• General appearance and level of alertness

• Ease of phonation

• Skin color

• Posture and chest shape

• Ventilatory or breathing pattern

• Presence of digital clubbing

• Presence of supplemental O₂ and other medical equipment (refer to Chapter 18)

• Presence and location of surgical incisions

Observation of Breathing Patterns

Breathing patterns vary among individuals and may be influenced by pain, emotion, body temperature, sleep, body position, activity level, and the presence of pulmonary, cardiac, metabolic, or nervous system disease (Table 4-4). The optimal time, clinically, to examine a patient’s breathing pattern is when he or she is unaware of the inspection because knowledge of the physical examination can influence the patient’s respiratory pattern.

TABLE 4-4

Description of Breathing Patterns and Their Associated Conditions

Breathing Pattern	Description	Associated Conditions
Apnea	Lack of airflow to the lungs for >15 seconds	Airway obstruction, cardiopulmonary arrest, alterations of the respiratory center, narcotic overdose
Biot’s respirations	Constant increased rate and depth of respiration followed by periods of apnea of varying lengths	Elevated intracranial pressure, meningitis
Bradypnea	Ventilation rate <12 breaths per minute	Use of sedatives, narcotics, or alcohol; neurologic or metabolic disorders; excessive fatigue
Cheyne-Stokes respirations	Increasing depth of ventilation followed by a period of apnea	Elevated intracranial pressure, CHF, narcotic overdose
Hyperpnea	Increased depth of ventilation	Activity, pulmonary infections, CHF
Hyperventilation	Increased rate and depth of ventilation resulting in decreased PCO₂	Anxiety, nervousness, metabolic acidosis
Hypoventilation	Decreased rate and depth of ventilation resulting in increased PCO₂	Sedation or somnolence, neurologic depression of respiratory centers, overmedication, metabolic alkalosis
Kussmaul respirations	Increased regular rate and depth of ventilation	Diabetic ketoacidosis, renal failure
Orthopnea	Dyspnea that occurs in a flat supine position. Relief occurs with more upright sitting or standing	Chronic lung disease, CHF
Paradoxic ventilation	Inward abdominal or chest wall movement with inspiration and outward movement with expiration	Diaphragm paralysis, ventilation muscle fatigue, chest wall trauma
Sighing respirations	The presence of a sigh >2-3 times per minute	Angina, anxiety, dyspnea
Tachypnea	Ventilation rate >20 breaths per minute	Acute respiratory distress, fever, pain, emotions, anemia
Hoover’s sign*	The inward motion of the lower rib cage during inhalation	Flattened diaphragm often related to decompensated or irreversible hyperinflation of the lungs

CHF, Congestive heart failure; PCO₂, partial pressure of carbon dioxide.

†Data from Johnson CR, Krishnaswamy N, Krishnaswamy G: The Hoover’s sign of pulmonary disease: molecular basis and clinical relevance, Clin Mol Allergy 6:8, 2008.

^*Hoover’s sign has been reported to have a sensitivity of 58% and specificity of 86% for detection of airway obstruction. Hoover’s sign is associated with a patient’s body mass index, severity of dyspnea, and frequency of exacerbations and is seen in up to 70% of patients with severe obstruction.†

Data from Kersten LD: Comprehensive respiratory nursing: a decision-making approach, Philadelphia, 1989, Saunders; DesJardins T, Burton GG: Clinical manifestations and assessment of respiratory disease, ed 3, St Louis, 1995, Mosby;

Observation of breathing pattern should include an assessment of rate (12 to 20 breaths per minute is normal), depth, ratio of inspiration to expiration (one to two is normal), sequence of chest wall movement during inspiration and expiration, comfort, presence accessory muscle use, and symmetry.

Clinical Tip

If possible, examine a patient’s breathing pattern when he or she is unaware of the inspection because knowledge of the physical examination can influence the patient’s respiratory pattern. Objective observations of ventilation rate may not always be consistent with a patient’s subjective complaints of dyspnea. For example, a patient may complain of shortness of breath but have a ventilation rate within normal limits. Therefore the patient’s subjective complaints, rather than the objective observations, may be a more accurate measure of treatment intensity.

Auscultation

Auscultation is the process of listening to the sounds of air passing through the tracheobronchial tree and alveolar spaces. The sounds of airflow normally dissipate from proximal to distal airways, making the sounds less audible in the periphery than the central airways. Alterations in airflow and ventilation effort result in distinctive sounds within the thoracic cavity that may indicate pulmonary disease or dysfunction.

Auscultation proceeds in a systematic, side-to-side, and cephalocaudal fashion. Breath sounds on the left and right sides are compared in the anterior, lateral, and posterior segments of the chest wall, as shown in Figure 4-4. The diaphragm (flat side) of the stethoscope should be used for auscultation. The patient should be seated or lying comfortably in a position that allows access to all lung fields. Full inspirations and expirations are performed by the patient through the mouth, as the clinician listens to the entire cycle of respiration before moving the stethoscope to another lung segment.

FIGURE 4-4 Landmarks for lung auscultation on (A) anterior, (B) posterior, and (C) lateral aspects of the chest wall. (Courtesy Peter P. Wu.)

All of the following ensure accurate auscultation:

• Make sure stethoscope earpieces are pointing up and inward (toward your patient) before placing in the ears.

• Long stethoscope tubing may dampen sound transmission. Length of tubing should be approximately 30 cm (12 in) to 55 cm (21 to 22 in).¹²

• Always check proper function of the stethoscope before auscultating by listening to finger tapping on the diaphragm while the earpieces are in place.

• Apply the stethoscope diaphragm firmly against the skin so that it lays flat.

• Observe chest wall expansion and breathing pattern while auscultating to help confirm palpatory findings of breathing pattern (e.g., sequence and symmetry). For example, decreased chest wall motion palpated earlier in the left lower lung field may present with decreased breath sounds in that same area.

Breath sounds may be normal or abnormal (adventitious or added) breath sounds; all breath sounds should be documented according to the location and the phase of respiration (i.e., inspiration, expiration, or both) and in comparison with the opposite lung. Several strategies can be used to reduce the chance of false-positive adventitious breath sound findings, including the following:

• Ensure full, deep inspirations (decreased effort can be misinterpreted as decreased breath sounds).

• Be aware of the stethoscope tubing’s touching other objects (especially ventilator tubing) or chest hair.

• Periodically lift the stethoscope off the chest wall to help differentiate extraneous sounds (e.g., chest or nasogastric tubes, patient snoring) that may appear to originate from the thorax.

To maximize patient comfort, allow periodic rest periods between deep breaths to prevent hyperventilation and dizziness.

Normal Breath Sounds.

Clinically, tracheal or bronchial and vesicular breath sounds generally are documented as “normal” or “clear” breath sounds; however, the use of tracheal or vesicular breath sounds is more accurate.

Tracheal, Bronchial, or Bronchovesicular Sounds.

Normal tracheal or bronchial breath sounds are loud tubular sounds heard over the proximal airways, such as the trachea and main stem bronchi. A pause is heard between inspiration and expiration; the expiratory phase is longer than the inspiratory phase. Normal bronchovesicular sounds are similar to bronchial breath sounds; however, no pause occurs between inspiration and expiration.11,12

Vesicular Sounds.

Vesicular sounds are soft rustling sounds heard over the more distal airways and lung parenchyma. Inspiration is longer and more pronounced than expiration because a decrease in airway lumen during expiration limits transmission of airflow sounds.11,12

Note: In most reference books, a distinction between normal bronchial and bronchovesicular sounds is made to help with standardization of terminology. Often, however, this distinction is not used in the clinical setting.

Clinical Tip

The abbreviation CTA stands for “clear to auscultation.”

Abnormal Breath Sounds.

Breath sounds are abnormal if they are heard outside their usual location in the chest or if they are qualitatively different from normal breath sounds.¹⁴ Despite efforts to make the terminology of breath sounds more consistent, terminology may still vary from clinician to clinician and facility to facility. Always clarify the intended meaning of the breath sound description if your findings differ significantly from what has been documented or reported. Abnormal breath sounds with possible sources are outlined in Table 4-5.

TABLE 4-5

Possible Sources of Abnormal Breath Sounds

Sound	Possible Etiology
Bronchial (abnormal if heard in areas where vesicular sounds should be present)	Fluid or secretion consolidation (airlessness) that could occur with pneumonia
Decreased or diminished (less audible)	Hypoventilation, severe congestion, or emphysema
Absent	Pneumothorax or lung collapse