Non-Invasive Positive Pressure Ventilation
Continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) are non-invasive ventilation methods that deliver pressurized air through a tight-fitting mask. These devices have revolutionized prehospital respiratory care by providing an intermediate option between supplemental oxygen and endotracheal intubation. Studies consistently show that prehospital CPAP reduces intubation rates, ICU admissions, and mortality for patients with acute pulmonary edema and COPD exacerbations.
CPAP delivers a constant level of positive pressure throughout the breathing cycle, keeping alveoli open and improving gas exchange. BiPAP delivers two levels of pressure: a higher pressure during inspiration (IPAP) and a lower pressure during expiration (EPAP). BiPAP provides additional ventilatory support and is particularly useful for patients who are tiring and need help moving air. Many EMS systems carry CPAP; BiPAP availability in the prehospital setting is growing.
Indications and Contraindications
Primary indications for prehospital CPAP include acute pulmonary edema (CHF exacerbation), COPD exacerbation, and severe asthma not responding to bronchodilators. The patient must be conscious, able to maintain their airway, and able to cooperate with the mask. CPAP is contraindicated in patients who are apneic or near-apneic, unable to protect their airway, actively vomiting, have a pneumothorax (untreated), have facial trauma preventing mask seal, or have a systolic blood pressure below 90 mmHg.
Application and Monitoring
When applying CPAP, explain the device to the patient before placing it. The mask delivers air under pressure, which can feel claustrophobic. Coach the patient to breathe normally through the mask. Start at a pressure of 5 to 10 cm H2O and adjust based on patient response. Monitor vital signs, SpO2, and ETCO2 continuously. Improvement should be seen within 5 to 10 minutes: decreasing respiratory rate, improving SpO2, decreasing heart rate, and subjective improvement reported by the patient.
Recognizing Treatment Failure
If the patient does not improve or deteriorates on CPAP, be prepared to escalate to BVM ventilation and possible intubation. Signs of treatment failure include worsening respiratory distress, decreasing mental status, inability to tolerate the mask, vomiting (remove the mask immediately to prevent aspiration), and worsening vital signs. CPAP is a bridge to hospital care, not a definitive treatment. All patients on CPAP should be transported for ongoing evaluation and management.