Application of noninvasive ventilation in acute respiratory failure after cardiovascular surgery.

OBJECTIVE

To examine ventilatory response, oxygenation-related, and hemodynamics of patients with hypoxemic acute respiratory failure (ARF) submitted to noninvasive mechanical ventilation (NIV) during the postoperative phase of cardiovascular surgery in order to identify predictive variables of success, and to compare the different types of NIV.

METHODS

Seventy patients with hypoxemic ARF were randomized to one of three modalities of NIV--continuous positive airway pressure (CPAP) and ventilation with two pressure levels (PEEP + SP and BiPAP). Ventilation, oxygenation-related, and hemodynamics variables were analyzed at pre-application, and 3, 6, and 12 hours after the protocol began.

RESULTS

Thirteen patients were excluded. Thirty-one patients progressed to independence from ventilatory support and comprised the success group, and 26 required orotracheal intubation and were considered the nonsuccess group. Age, initial heart rate (HR), and respiratory rate (RR) showed elevated levels in the nonsuccess group (p=0.042, 0.029, and 0.002, respectively). A greater number of intraoperative complications were seen in the nonsuccess group (p=0.025). Oxygenation variables increased only in the success group. Among the NIV types, 57.9% of patients in the ventilator group, 57.9% in the two-pressure levels group, and 47.3% in the CPAP group progressed with success. Oxygenation and RR variables showed improvement only in the groups with two pressure levels.

CONCLUSION

Patients with hypoxemic ARF in the postoperative stage after cardiovascular surgery showed better oxygenation, RR, and HR during NIV application. In older patients and those with higher baseline RR and HR values, NIV was not sufficient to reverse ARF. The two-pressure level modes showed better results.