--- module: 016-01 language: en chapter: 16 title: "Respiratory History, Examination, Blood Gases, and Investigations" module_title: "Foundations" source_sha256: 5c672c029a0c3071aaa2d8c387d587d80fa954534c045713d9e94dc965c8d52f --- # Respiratory history, examination and investigation ## What the assessment must deliver ### Urgency, compartment, defect, cause, function ### Overlap with cardiac, metabolic and neuromuscular disease ### History and examination set pre-test probability ## Symptom history ### Dyspnoea #### Sudden: embolism, pneumothorax, obstruction, oedema #### Progressive: obstructive, interstitial, vascular, cardiac ### Cough: purulent colour reflects leukocytes, not bacteria ### Haemoptysis: estimate volume and assess airway risk #### Separate nasopharyngeal and gastrointestinal bleeding ### Wheeze: focal obstruction or diffuse airway disease ### Stridor is loud upper-airway obstruction and urgent ### Pleuritic pain: pleura, embolism, chest wall ### Exposure and background #### Smoking, vaping, occupational dust and fumes #### Tuberculosis contact, travel, immune suppression #### Drugs causing cough, bronchospasm or interstitial disease ## Observation and vital signs ### Position, speech, rate, pattern, accessory muscles ### Count the respiratory rate rather than estimate it ### Record oxygen device and flow with saturation ### Tachycardia: hypoxaemia, work, fever, embolism, drugs ### Instability demands support before a full examination ## Hands, face and neck ### Nicotine staining, cyanosis, tremor, asterixis ### Clubbing: cancer, bronchiectasis, fibrosis, abscess ### Not expected in uncomplicated asthma or airflow obstruction ### Pallor, central cyanosis, dentition, upper airway ### Tracheal deviation: volume loss, mass, effusion, tension ## Chest examination ### Inspection: shape, scars, symmetry, expansion ### Unilateral lag: pain, collapse, pleural disease ### Fremitus rises over consolidation, falls with fluid or gas ### Percussion: resonant, dull or hyperresonant, compared ### Auscultation #### Bronchial breathing peripherally: consolidation or cavity #### Fine late crackles: fibrosis or oedema #### Coarse crackles: secretions, but overlap is large #### Pleural rub is grating and localised ### Vocal resonance for consolidation or effusion ### Systemic examination: venous pressure, oedema, calves ## A reproducible examination map ### Specify side, surface, height, phase and comparison ### Not a pathological or segmental diagnosis ### Lets another examiner revisit the same region ### Compare paired sites before changing height ### Poor technique must not become confident localisation ### New asymmetry: ventilation, transmission or pain ### Record unassessed regions, and never delay support ## Arterial and venous blood gases ### Arterial gas: pH, carbon dioxide, oxygen, bicarbonate ### Venous gas cannot replace arterial oxygen ### Sampling errors: bubbles, delay, contamination ### Interpret in order #### pH, then the primary direction of change #### Expected compensation #### Anion gap in metabolic acidosis #### Oxygenation with inspired oxygen and context ### Acute retention limits bicarbonate rise, chronic allows more ### Alveolar-arterial difference separates hypoventilation ### Co-oximetry measures dyshemoglobins directly ## Imaging and function testing ### Chest radiograph: volume, opacity, pleura, devices ### Technique alters appearance: portable, rotation, supine ### A normal film excludes little ### Computed tomography, including high-resolution technique ### Ultrasound cannot see through aerated lung ### Spirometry: a reduced ratio confirms obstruction ### Total lung capacity confirms restriction ### Diffusing capacity with haemoglobin correction ### Challenge testing, walk test, exercise testing ## Sampling, severity and procedures ### Sputum quality: saliva contamination reduces value ### Bronchoscopy samples and clears, with real risk ### Pleural fluid: protein, enzymes, pH, cells, cytology ### Very low pH in parapneumonic effusion supports drainage ### Severity tools supplement rather than replace judgement ### A low score misses trajectory, frailty and barriers ### Procedures need indication, consent and clotting review ### Complications: pneumothorax, bleeding, re-expansion oedema ### Preoperative: optimise rather than test without a question