Physiologic evaluation of non-invasive pressure support ventilation in trauma patients with acute respiratory failure

To investigate the effectiveness of noninvasive (face mask) versus invasive (endotracheal tube) equal pressure values on blood gases and respiratory pattern and to evaluate the feasibility of using mask ventilation after the short term physiologic study.

Open, prospective, physiologic study and uncontrolled clinical study.

Intensive care unit of a trauma center.

22 intubated trauma patients were studied.

Patients were intubated and ventilated in a pressure support mode (IPSV) of 13.5 +/- 1.5 cmH2O and a post end-expiratory pressure (PEEP) of 5.8 +/- 2.57 cmH2O. After a T-piece trial to assess patient's ability to breath spontaneously, patients were switched over to noninvasive pressure support (NIPSV). The pressure levels were set as during IPSV. Blood gases and respiratory parameters were measured during IPSV, during the T-piece trial, and after 1 h of NIPSV. After the physiologic study, all patients were asked if they wished to continue on NIPSV. The patient's subjective compliance with IPSV and NIPSV was measured by means of an arbitrary score. A successful outcome was defined as no need for reintubation.

IPSVand NIPSV showed no statistical differences for blood gas and respiratory parameters by using the same values of PSV (13 +/- 5 vs 12.8 +/- 1.7 cmH2O, NS) and PEEP (5.8 +/- 2.5 and 5.2 +/- 2.2 cmH2O NS). The median length of time on NIPSV was 47 h (range 6 to 144). All patients wished to continue on NIPSV, but 9 patients (40.9%) were reintubated after 54 +/- 54 h. Six of them died after 36 +/- 13 days while still on mechanical ventilation. There was no statistically significant difference in compliance score between IPSVand NIPSV.

NIPSV is comparable to IPSV in terms of blood gases and respiratory pattern. The clinical uncontrolled study indicates that NIPSV could be used in selected trauma patients.