Makindo Medical Notes

CPAP (Continuous Positive Airway Pressure) provides constant positive pressure via a nasal or full-face mask. Consider in acute respiratory distress not responding to medical therapy — always discuss with a senior. ⚠️ Requires close monitoring by experienced staff to avoid complications.

📌 Indications

• Acute pulmonary oedema (confirmed on CXR).
• Obstructive sleep apnoea (OSA).
• Sometimes used as a bridge in Type I respiratory failure (e.g. pneumonia, post-op atelectasis).

🚨 Escalation: ITU Referral

• Falling GCS (risk of airway compromise).
• SpO₂ <90% on high-flow O₂ via non-rebreather mask.
• PaO₂ <8 kPa on ABG despite oxygen therapy.
• Refractory pulmonary oedema despite diuretics and vasodilators.
• Systolic BP >90 mmHg is generally required for safe CPAP initiation.

⚠️ Be Ready for Intubation

• Absolute indication: apnoea or profound respiratory depression (RR <10/min).
• Persistent hypoxaemia or hypercapnia despite optimal CPAP + medical management.
• Deteriorating mental status or inability to protect airway → urgent ITU referral.

⚡ Physiological Effects of CPAP

• 💉 Reduces preload: increased intrathoracic pressure ↓ venous return.
• 🫀 Lowers afterload: augments LV ejection, improving stroke volume in LV failure.
• 🫁 Respiratory effects: alveolar recruitment, airway splinting, ↑ functional residual capacity, ↓ work of breathing.
• Typical starting pressure: 5 cm H₂O, titrate up to 10 cm H₂O if needed.

⛔ Contraindications

• Reduced consciousness (AVPU ≤ P) → cannot protect airway.
• Dementia or agitation → intolerance to mask.
• Systolic BP <90 mmHg → risk of cardiovascular collapse.
• Pneumothorax.
• Facial trauma or base of skull fracture.
• Type II respiratory failure (CO₂ retention) — consider BiPAP instead.

⚠️ Complications

• Hypotension (due to ↓ venous return and cardiac output).
• Aspiration (air insufflation can overcome oesophageal sphincter).
• Gastric distension (risk of vomiting, discomfort).
• Anxiety/panic due to tight-fitting mask and hypoxia.

🛑 When to Stop CPAP

• Continue until lungs clear of crackles and patient haemodynamically stable.
• Wean airway pressure first, then reduce FiO₂ and step down to a facemask.
• If no improvement within 30 minutes → discontinue and escalate care.

🌟 Teaching pearl: In acute pulmonary oedema, CPAP rapidly improves oxygenation and reduces preload/afterload, often buying time for diuretics and vasodilators to work. Always have an intubation backup plan before starting CPAP.

Case examples

• 💨 Case 1 – Age 72: Presented to A&E with acute shortness of breath, frothy pink sputum, and hypoxia (SpO₂ 84% on air). CXR showed pulmonary oedema due to acute left ventricular failure. Management: CPAP started at 10 cm H₂O alongside IV furosemide and nitrates. Oxygenation improved rapidly, avoiding intubation. Teaching point: In cardiogenic pulmonary oedema, CPAP reduces preload and afterload, improving gas exchange and cardiac performance.
• 😴 Case 2 – Age 55: Overweight man reported loud snoring, witnessed apnoeas, and daytime sleepiness. Overnight oximetry showed repetitive desaturations; sleep study confirmed moderate OSA. Management: CPAP during sleep eliminated apnoeas and improved daytime alertness and blood pressure. Teaching point: In obstructive sleep apnoea, CPAP splints the upper airway open, preventing collapse during inspiration.
• 🌬️ Case 3 – Age 68: Known COPD with type 2 respiratory failure (pH 7.31, pCO₂ 8.4 kPa, HCO₃⁻ 31 mmol/L) presented with acute dyspnoea and fatigue. Initially treated with controlled oxygen but remained hypercapnic. Management: Trial of non-invasive ventilation (BiPAP), but early CPAP used to improve alveolar recruitment and reduce work of breathing. Teaching point: CPAP or BiPAP may prevent intubation in COPD exacerbations by supporting ventilation and reducing CO₂ retention.