5.1 Respiratory Assessment & Diagnostics

Inspection: What You See Before You Touch

Begin every respiratory assessment with inspection. Note respiratory rate (normal 12-20 breaths/min), rhythm, work of breathing, and chest configuration.

• Barrel chest — an anteroposterior (AP) to transverse diameter ratio approaching 1:1 (normal is about 1:2). It reflects chronic air trapping and is classic in emphysema.
• Clubbing — flattening of the nail bed angle to 180 degrees or more with loss of the Schamroth window (the diamond-shaped gap seen when two opposing fingernails are placed together). Clubbing signals chronic hypoxemia from conditions such as lung cancer, bronchiectasis, pulmonary fibrosis, or cyanotic congenital heart disease. Uncomplicated COPD alone usually does not cause clubbing — its presence should prompt a search for malignancy or suppurative disease.
• Accessory muscle use — visible contraction of the sternocleidomastoid and scalene muscles plus intercostal retractions indicates increased work of breathing and impending fatigue.
• Tripod position — leaning forward with hands braced on the knees fixes the shoulder girdle and maximizes accessory muscle use; seen in severe COPD and acute respiratory distress.
• Cyanosis — central cyanosis (lips, tongue, oral mucosa) indicates roughly 5 g/dL or more of deoxygenated hemoglobin and is a late, serious sign; peripheral cyanosis (nail beds, earlobes) may reflect only poor local perfusion.

Palpation and Percussion

Tactile fremitus is the palpable vibration of the chest wall as the patient says "ninety-nine." Sound transmits better through solid tissue than air, so fremitus is increased over consolidation (pneumonia, atelectasis with patent airways) and decreased or absent where air or fluid separates the lung from the chest wall (pneumothorax, pleural effusion, severe emphysema). Crepitus — a crackling sensation under the skin — indicates subcutaneous emphysema from air leaking into soft tissue, seen after chest trauma, chest tube placement, or tracheostomy. Palpate the trachea at the suprasternal notch: tracheal deviation away from the affected side suggests tension pneumothorax or large effusion; deviation toward the affected side suggests atelectasis.

Percussion tones map the density beneath your fingers:

Breath Sounds and Sputum

Normal breath sounds include vesicular (soft, low-pitched, heard over the periphery), bronchovesicular (over the mainstem bronchi), and bronchial (loud, tubular, heard only over the trachea — bronchial sounds over peripheral lung indicate consolidation).

Sputum analysis supports diagnosis: collect specimens before starting antibiotics whenever possible, ideally first thing in the morning from a deep cough (not saliva). Purulent yellow-green sputum suggests bacterial infection; rust-colored sputum is classic for pneumococcal pneumonia; pink frothy sputum indicates pulmonary edema; hemoptysis requires investigation for malignancy, tuberculosis, or pulmonary embolism.

Arterial Blood Gas Interpretation

Normal values: pH 7.35-7.45, PaCO2 35-45 mmHg, HCO3 22-26 mEq/L, PaO2 80-100 mmHg. Use a consistent stepwise method (the ROME mnemonic — Respiratory Opposite, Metabolic Equal — helps):

1. Look at the pH. Below 7.35 is acidemia; above 7.45 is alkalemia.
2. Look at PaCO2 (the respiratory component). If it moves opposite to the pH, the disorder is respiratory (high CO2 with low pH = respiratory acidosis).
3. Look at HCO3 (the metabolic component). If it moves in the same direction as the pH, the disorder is metabolic (low bicarbonate with low pH = metabolic acidosis).
4. Determine compensation. If the other component is abnormal in the direction that corrects the pH, compensation is occurring. Compensation is partial if the pH remains abnormal and full if the pH returns to normal range. Remember: the lungs compensate in minutes to hours; the kidneys need 2-5 days, so chronic respiratory acidosis (as in COPD) shows an elevated bicarbonate.
5. Assess oxygenation with PaO2 and SaO2 — acid-base status and oxygenation are separate questions.

Worked example: pH 7.30, PaCO2 55, HCO3 28. Low pH = acidemia. CO2 is high (opposite the pH) = respiratory acidosis. Bicarbonate is elevated = partial compensation. This pattern fits an acute COPD exacerbation with early renal retention of bicarbonate.

Pulse Oximetry: Strengths and Limits

Pulse oximetry (SpO2) estimates arterial oxygen saturation noninvasively. A normal reading is 95-100%. Understand its blind spots, because the exam tests them:

• Carbon monoxide poisoning — carboxyhemoglobin absorbs light like oxyhemoglobin, so SpO2 reads falsely normal while the patient suffocates at the tissue level. Obtain a co-oximetry ABG.
• Methemoglobinemia — SpO2 classically plateaus around 85% regardless of oxygen delivery.
• Poor perfusion (shock, hypothermia, vasoconstriction), motion artifact, dark nail polish, and severe anemia all degrade accuracy.
• The oxyhemoglobin dissociation curve is sigmoid: a patient can drop from a PaO2 of 60 into steep desaturation rapidly. An SpO2 of 90% corresponds to a PaO2 of roughly 60 mmHg — treat 90% as the alarm threshold, not "good enough."

Pulmonary Function Tests

Pulmonary function tests (PFTs) quantify airflow and gas exchange. Key values:

• FEV1/FVC ratio (forced expiratory volume in 1 second over forced vital capacity): below 0.70 post-bronchodilator defines obstruction (COPD, asthma).
• FVC reduced with a normal or high ratio suggests restriction (pulmonary fibrosis, kyphoscoliosis, obesity).
• DLCO (diffusing capacity for carbon monoxide): reduced in emphysema and interstitial lung disease; preserved in chronic bronchitis and asthma — useful for distinguishing them.

Nursing preparation: withhold bronchodilators and smoking for 4-6 hours before testing as ordered; the test requires maximal patient effort.

Bronchoscopy and Thoracentesis: Nursing Care

Bronchoscopy allows airway visualization, biopsy, and secretion removal. Before: keep the patient NPO for 6-8 hours, verify consent, remove dentures, and give pre-procedure sedation as ordered. After: keep NPO until the gag and swallow reflexes return (topical anesthetic abolishes them — aspiration risk), position semi-Fowler's, monitor for laryngospasm, hemoptysis, and respiratory distress. Blood-tinged sputum is expected; frank bleeding is not. If a biopsy or transbronchial brushing was performed, obtain a chest x-ray to rule out pneumothorax.

Thoracentesis drains pleural fluid for diagnosis or relief. Position the patient sitting upright, leaning over the overbed table with arms supported — this widens the intercostal spaces. Instruct the patient not to cough or take deep breaths during needle insertion. Watch for cough, chest pain, or dyspnea during the procedure (needle injury), and afterwards for pneumothorax and re-expansion pulmonary edema (risk rises when more than 1,000-1,500 mL is removed at once). A post-procedure chest x-ray is standard. Record the amount, color, and character of fluid and send ordered studies (cell count, protein, LDH, glucose, culture, cytology).