Investigations & What You Expect to Find
| Test | Why / expected finding |
|---|---|
| CBC | Secondary polycythaemia (chronic hypoxaemia); eosinophil count — absolute eosinophils > 300–350/mm³ favours a response to inhaled corticosteroids |
| CXR | Hyperinflation (low flat diaphragms, horizontal ribs, wide intercostal spaces, hyperlucent lungs), tubular heart, bullae (pneumothorax risk); rule out active infection |
| ECG | Signs of right-heart disease: P-pulmonale (RA enlargement), right-axis deviation, RVH (dominant R in V1–V3, RSR′); also to rule out IHD |
| 2-D Echo | If cardiac symptoms, heart failure or advanced pulmonary disease — pulmonary hypertension, RV function |
| ABG | Hypoxaemia, CO₂ retention, prognosis — PaCO₂ > 45 mmHg and PaO₂ < 60 mmHg (room air) both signal a worse prognosis |
Pulmonary Function Tests & Spirometry
📉 What spirometry shows in COPD
- ↓ FEV₁ and ↓ FEV₁/FVC ratio < 0.70 (the defining obstruction)
- ↑ FRC and RV (air trapping / hyperinflation)
- ↓ DLCO (emphysematous loss of alveolar surface)
- ↓ FEF25–75% (small-airway obstruction) & ↓ PEFR (early airway obstruction)
Is routine PFT needed? Chiefly useful to predict post-resection pulmonary function and confirm/grade disease. For non-thoracic surgery, spirometry is a tool for pre-operative optimisation and severity assessment, not a mandatory routine — clinical assessment and functional capacity matter more.
Bedside Pulmonary Function Tests & PPC Predictors
| Bedside test | Interpretation |
|---|---|
| Sabrasez breath-holding | > 25 s normal reserve · 15–25 s limited · < 15 s very poor cardiopulmonary reserve |
| Single-breath count | Normal 30–40 (reflects vital capacity); < 15 = severe impairment |
| Snider's match-blowing test | Cannot blow out a match at 15 cm → MBC < 60 L/min (significant obstruction) |
| Forced expiratory time | Normal 3–5 s; > 6 s = obstructive; < 3 s = restrictive |
| Cough test / effective cough | Inadequate if FVC < 20 mL/kg, FEV₁ < 15 mL/kg, PEFR < 200 L/min (VC should be ≥ 3× tidal volume) |
| 6-minute walk test | Normal 400–700 m; < 350 m correlates with ↑ exacerbation, hospitalisation & mortality risk |