11.1 Pulmonary Evaluation, Auscultation, and Gas Analysis

Pulmonary Evaluation, Auscultation, and Gas Analysis

Cardiopulmonary physical therapy requires rigorous bedside diagnostic skills to assess ventilatory mechanics, gas exchange efficacy, and respiratory muscle function. Physical therapists working in acute intensive care units, inpatient wards, and outpatient pulmonary rehabilitation clinics must systematically evaluate the thoracic cage, interpret acoustic lung phenomena, and analyze laboratory blood gas values to establish safe, effective therapeutic interventions.

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Clinical Pulmonary Inspection

The clinical examination begins the moment the clinician observes the patient at rest. Visual inspection focuses on chest wall architecture, resting posture, work of breathing, and ventilatory rate and rhythm.

Chest Wall Architecture

Inspect the shape and symmetry of the thorax and observe how the chest and abdomen move. Interpret morphology with symptoms and measured function.

• Barrel-shaped chest: Increased anteroposterior diameter may accompany chronic hyperinflation. Chest shape alone has limited diagnostic value.
• Pectus excavatum and carinatum: The sternum is displaced inward or outward, respectively. Significant excavatum can affect cardiopulmonary function. Check symptoms and measured exercise limitation before assigning functional importance.
• Kyphoscoliosis: Severe deformity can restrict chest wall excursion and may contribute to hypoventilation. Functional impact varies with severity.

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Breathing Patterns and Respiratory Dynamics

Observation of respiratory rate ($RR$), depth (tidal volume), and thoracic symmetry provides immediate diagnostic clues regarding central neurological drive and peripheral ventilatory mechanics:

• Eupnea: Quiet breathing at rest. In an awake adult, 12–20 breaths/min is a common reference interval. Interpret rate with depth, effort, mental status and change from baseline.
• Tachypnea and bradypnea: Faster or slower breathing than expected in context. Pain, fever, hypoxemia or metabolic acidosis can increase rate. Sedating drugs can slow breathing or reduce its depth.
• Cheyne–Stokes breathing: Recurrent waxing and waning ventilation with central apneas or hypopneas. It can occur in heart failure and neurologic disease. Circulatory delay and altered ventilatory control can contribute.
• Kussmaul breathing: Deep, often rapid breathing associated with significant metabolic acidosis, as in diabetic ketoacidosis.
• Thoracoabdominal paradox: Observe which segment moves inward and when. Inspiratory abdominal indrawing can occur with diaphragmatic weakness. An unstable chest-wall segment can move paradoxically after trauma. Evaluate a new finding with the patient's work of breathing and stability.
• Hoover's sign: The lateral lower rib cage draws inward on inspiration. Altered diaphragm geometry and the balance of inspiratory forces can contribute in COPD. The sign alone cannot grade hyperinflation.

Quiet breathing       Similar breath depth across successive breaths
Cheyne–Stokes         Smaller → larger → smaller breaths → pause → repeat
Kussmaul              Repeated deep breaths in significant metabolic acidosis

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Palpation: Chest Expansion and Tactile Fremitus

Palpation helps compare motion and the transmission of sound between sides. Interpret the findings with inspection, percussion, auscultation and the clinical presentation.

Chest Wall Expansion

Place both hands symmetrically over the lower posterolateral thorax and compare their movement during inspiration. Anterior or more superior hand positions can assess other chest wall regions. Document the position and respiratory effort so changes can be compared. Reduced unilateral movement can accompany pain, pleural disease, pneumothorax, atelectasis or neuromuscular dysfunction. Surface motion alone cannot isolate an individual lobe.

Tactile Fremitus

Tactile fremitus is the vibration felt at the chest wall while the patient speaks. Use the same spoken phrase and comparable hand contact as you compare corresponding interspaces.

• Increased fremitus can occur when consolidated lung transmits central airway vibrations through a patent bronchus.
• Reduced fremitus can occur over pleural fluid or air, with hyperinflation or when a bronchus is obstructed.

Percussion can add context. Dullness can accompany consolidation or pleural fluid, while hyperresonance can occur with excess air. Compare findings and refer for further assessment when the patient is deteriorating or the cause is uncertain.

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Pulmonary Auscultation

Use a stethoscope on skin and compare corresponding sites over the anterior, lateral and posterior chest. Listen through inspiration and expiration. Note the location, intensity, timing and changes after coughing or repositioning.

Peripheral bronchial breathing can occur over consolidated lung with a patent airway. Reduced or asymmetric sounds can reflect reduced airflow or altered transmission. Interpret either finding with the rest of the examination.

Adventitious Sounds

• Crackles: Brief, discontinuous sounds. Fine crackles are shorter and higher pitched, often late inspiratory in fibrosis. Coarse crackles are longer and lower pitched. Retained secretions can contribute, especially when the sound changes after coughing. Both types can occur in more than one disorder.
• Wheeze: A continuous musical sound associated with airflow through narrowed airways. Record its phase and distribution. A low-pitched, snoring continuous sound is often called a rhonchus.
• Stridor: A loud sound from narrowing of the upper airway, often inspiratory and sometimes biphasic. New stridor with respiratory distress warrants an immediate airway and emergency response.
• Pleural rub: A localized grating sound with respiration can accompany pleural inflammation.

Vocal Resonance

Listen over matched regions during a repeated phrase (bronchophony), a sustained “ee” (egophony), or a whispered phrase (whispered pectoriloquy). Greater clarity or loudness of transmitted words, or an “ee” that sounds like “ay,” can support the suspicion of altered transmission from consolidation. Egophony can also occur near the upper border of a pleural effusion. Use the history, vital signs and appropriate investigations to establish the cause.

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Arterial Blood Gas (ABG) Interpretation

Arterial blood gas values describe acid-base status, ventilation and arterial oxygen tension at the time of sampling. Record the oxygen device or room air and compare with prior measurements.

Adult Reference Values

Common reference intervals are pH 7.35–7.45, $PaCO_2$ 35–45 mmHg and bicarbonate 22–26 mmol/L. A commonly taught room-air $PaO_2$ in a healthy adult at sea level is around 80–100 mmHg. Oxygen tension depends on age, inspired oxygen and altitude. $PaO_2$ is an oxygen partial pressure. $SaO_2$ describes hemoglobin oxygen saturation and $SpO_2$ estimates saturation peripherally.

Interpret the Direction and Expected Compensation

1. Read the pH. A value below 7.35 is acidemia and a value above 7.45 is alkalemia using the intervals above. An in-range pH can occur with offsetting or compensated processes.
2. Identify a process that explains the direction. Higher $PaCO_2$ or lower bicarbonate can contribute to acidemia. Lower $PaCO_2$ or higher bicarbonate can contribute to alkalemia. Consider the clinical setting and timing.
3. Compare with expected compensation. Reference intervals describe healthy values. The expected response to a disturbance can remain inside them. A result outside the expected response suggests a mixed process or a different time course.

For acute respiratory acidosis, a practical starting estimate is a bicarbonate rise of about 1 mmol/L for each 10 mmHg rise in $PaCO_2$. For chronic respiratory acidosis, the rise is several times larger and depends on the population and baseline. Compare with prior gases when available. At $PaCO_2$ of 56 mmHg, starting from 40 mmHg and bicarbonate 24 mmol/L, the acute estimate is about 25.6 mmol/L.

For metabolic acidosis, the expected $PaCO_2$ is approximately $1.5 \times [HCO_3^-] + 8$, with a range of about ±2 mmHg. At bicarbonate 16 mmol/L, the expected value is 32 ±2 mmHg. If measured $PaCO_2$ is 43 mmHg, consider a concurrent respiratory acidosis even though 43 is within the usual reference interval. Use the clinical context, electrolytes and trend to complete the interpretation.

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Pulse Oximetry ($SpO_2$) Principles and Limitations

A conventional pulse oximeter uses the pulsatile optical signal at two wavelengths, commonly near 660 and 940 nm, to estimate functional arterial oxygen saturation. Check the trend and signal quality alongside respiratory effort, alertness and circulation.

• Signal and measurement conditions: Motion, low peripheral perfusion, temperature and nail products can interfere. Some devices can overestimate saturation in people with darker skin pigmentation, especially at low true saturation. Investigate discordance between the reading and the clinical picture.
• Carbon monoxide: A two-wavelength oximeter can give a falsely reassuring result in the presence of carboxyhemoglobin. Suspected exposure requires urgent evaluation and blood co-oximetry, using a venous or arterial sample according to the service.
• Methemoglobinemia: Substantial methemoglobin can drive a conventional reading toward about 85%. Use blood co-oximetry for a reliable measurement of dyshemoglobin fractions.
• Oxygen content and ventilation: A high saturation can coexist with reduced oxygen content in severe anemia, or with hypoventilation and elevated $PaCO_2$. Assess ventilation and hemoglobin separately when indicated.

Use the ordered oxygen range and the protocol for the setting. A patient with suspected hypoxemic COPD exacerbation and risk of hypercapnic respiratory failure is commonly treated initially to 88%–92% with controlled oxygen and prompt blood gas assessment. Stable rehabilitation targets and walk-test stopping rules have separate clinical purposes.

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Dyspnea Assessment Scales

Quantifying breathlessness during rest and therapeutic exertion requires validated, standardized rating scales.

Modified Medical Research Council (mMRC) Dyspnea Scale

The modified Medical Research Council (mMRC) scale grades activity limitation from breathlessness in everyday life.

For current symptoms during exercise, use a standardized breathlessness scale such as the modified Borg 0–10 scale. Use the same wording and time point when comparing results. The Borg 6–20 scale is commonly used for overall perceived exertion. Heart rate is measured separately. Choose training intensity using the patient's test results, symptom ratings, saturation response and medical plan.

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Clinical Case Scenario: Bedside Decision-Making

A 68-year-old with COPD is admitted with more breathlessness, cough and purulent sputum. There are coarse crackles and expiratory wheezes at the bases. On room air, $SpO_2$ is 86%. The arterial sample shows pH 7.32, $PaCO_2$ 58 mmHg, bicarbonate 29 mmol/L and $PaO_2$ 54 mmHg. Stable results had shown $PaCO_2$ 48 mmHg and bicarbonate 28 mmol/L.

Interpretation: The current sample shows acidemia with hypercapnia and hypoxemia. Relative to the known baseline, $PaCO_2$ rose by 10 mmHg and bicarbonate by 1 mmol/L, consistent with an acute respiratory acidosis superimposed on chronic hypercapnia. Elevated bicarbonate alone would be insufficient to determine timing.

Priority: Pause treatment and alert the medical team promptly. Support controlled oxygen delivery under the local protocol, typically targeting 88%–92% initially in this setting. Repeat gas assessment and evaluation for noninvasive ventilatory support are priorities if respiratory acidosis persists despite initial treatment. Once stable, assess cough effectiveness and secretion retention to decide whether targeted airway clearance is indicated.