Continuous Positive Airways Pressure (CPAP) ✅

💨 CPAP (Continuous Positive Airway Pressure) delivers a constant positive airway pressure via a tight-fitting mask. In acute care, it is used mainly to improve oxygenation and reduce work of breathing, especially in cardiogenic pulmonary oedema. It should only be started in an area with close monitoring, experienced staff, and a clear escalation plan.

📌 Main indications

• Acute cardiogenic pulmonary oedema / acute heart failure with severe respiratory distress.
• Obstructive sleep apnoea (OSA) – chronic nocturnal treatment in the appropriate sleep-medicine setting.
• Selected specialist use in some acute hypoxaemic respiratory failure settings, usually after senior/critical care review.

🚨 NICE-aligned acute heart failure point

• Do not use CPAP/NIV routinely in acute heart failure with cardiogenic pulmonary oedema.
• Consider without delay if there is cardiogenic pulmonary oedema with severe dyspnoea and acidaemia, either:
  • at initial presentation, or
  • as an adjunct when the patient has not responded adequately to medical therapy.

⚡ Physiological effects of CPAP

• 🫀 Reduces preload by increasing intrathoracic pressure and reducing venous return.
• 🫀 Reduces left ventricular afterload by lowering LV transmural pressure, which can improve cardiac output in LV failure.
• 🫁 Recruits alveoli, increases functional residual capacity, and improves oxygenation.
• 😮‍💨 Reduces work of breathing by splinting open alveoli and improving lung compliance.

🛠️ Practical setup

• Typical starting pressure: 5–10 cm H₂O, adjusted according to response and local protocol.
• Use supplemental oxygen as needed to maintain target saturations.
• Monitor:
  • respiratory rate and work of breathing,
  • SpO₂,
  • heart rate and blood pressure,
  • mental state,
  • arterial/venous blood gas where appropriate.

🚨 Escalation / ITU referral

• Falling GCS or inability to protect the airway.
• Worsening hypoxia despite optimal oxygen and CPAP.
• Physical exhaustion or signs of impending respiratory arrest.
• Haemodynamic instability or hypotension.
• Persistent or worsening acidaemia despite treatment.
• Need for possible invasive ventilation.

⚠️ Be ready for intubation

• Apnoea or profound respiratory depression.
• Inability to maintain airway patency.
• Deteriorating conscious level.
• Failure to improve clinically despite optimal non-invasive support and medical therapy.

⛔ Contraindications / situations where CPAP may be unsafe

• Reduced consciousness or inability to protect airway.
• Active vomiting or high aspiration risk.
• Severe agitation, confusion, or inability to cooperate with the mask.
• Untreated pneumothorax.
• Facial trauma, facial burns, or base of skull fracture preventing safe mask fit.
• Marked hypotension or haemodynamic instability.

⚠️ Important differential point: CPAP vs NIV (BiPAP)

• CPAP mainly improves oxygenation and reduces preload/afterload.
• NIV/BiPAP provides inspiratory ventilatory support as well as expiratory pressure.
• In acute COPD exacerbation with persistent acidotic hypercapnic respiratory failure despite optimal medical therapy, NIV is the usual treatment rather than CPAP.

⚠️ Complications

• Hypotension from reduced venous return.
• Mask intolerance, panic, or claustrophobia.
• Gastric insufflation and abdominal discomfort.
• Aspiration if vomiting occurs.
• Pressure sores over nasal bridge / face.
• Barotrauma (uncommon, but important).

🛑 Reassessment and stopping CPAP

• Reassess early after initiation for improvement in:
  • oxygenation,
  • work of breathing,
  • respiratory rate,
  • haemodynamics,
  • gas exchange/acidaemia where relevant.
• If the patient is improving, continue and gradually wean according to clinical response and local protocol.
• If there is no improvement or deterioration, urgently escalate to senior/critical care review.

🌟 Teaching pearl: In cardiogenic pulmonary oedema, CPAP can produce rapid improvement because it both recruits flooded alveoli and unloads the failing left ventricle. In contrast, in hypercapnic COPD exacerbations, the key problem is ventilatory failure, so NIV/BiPAP is usually the more appropriate non-invasive support.

Case examples

• 💨 Case 1 – Acute cardiogenic pulmonary oedema: A 72-year-old presents with severe breathlessness, bilateral crackles, frothy sputum, and hypoxia. CPAP is started alongside standard medical treatment in a monitored setting. Teaching point: CPAP may rapidly improve oxygenation and reduce preload/afterload while other therapy takes effect.
• 😴 Case 2 – Obstructive sleep apnoea: A 55-year-old with obesity, loud snoring, witnessed apnoeas, and daytime somnolence is diagnosed with OSA after sleep assessment. Night-time CPAP abolishes upper airway collapse during sleep. Teaching point: In OSA, CPAP acts as a pneumatic splint to keep the pharyngeal airway open.
• 🌬️ Case 3 – COPD exacerbation with hypercapnic acidosis: A 68-year-old with COPD has pH 7.31 and pCO₂ 8.4 kPa despite controlled oxygen and medical treatment. He is referred for NIV rather than CPAP. Teaching point: Persistent acidotic hypercapnic ventilatory failure in COPD is a classic indication for NIV/BiPAP.