Which positive end expiratory pressure (PEEP) should be used during noninvasive positive pressure ventilation (NPPV) in acute lung injury/acute respiratory distress syndrome (ALI/ARDS) patients?

Objective

To establish the effects of different levels of PEEP on blood oxygenation and intra-abdominal pressurization (IAP), in order to select a sufficient level of PEEP during NPPV of ALI/ARDS patients.

Methods

Six early ALI/ARDS patients, four male/two female, aged 49.67 ± 16.28 years, paO₂/FIO₂ = 202.50 ± 79.69, with bilateral infiltrates on thoracic roentgenogram, APACHE II = 15.67 ± 5.43, were prospectively studied.

Patients were ventilated on a BIPAP Vision. Pressure support was fixed at 10 cmH₂O. EPAP (PEEP) was applied at 5, 8, 11, 14, 17 and 20 cmH₂O. paO₂/FiO₂ and gradients between paCO₂ and EtCO₂ were calculated after 20 min at each level of EPAP. IAP was measured through intravesical catheters. Arterial blood pressure (ABP) and heart rate (HR) were continuously monitored.

Results

Increased levels of EPAP had positive effects on oxygenation and little effect on IAP and on hemodynamic features, showing that most of the applied pressure was dissipated at the respiratory system, probably recruiting collapsed alveolar units (Table 1). Mean EPAP was 12 ± 4.90 cmH₂O (range = 8–20 cmH₂O). Only one of these six patients was invasively ventilated. All patients survived.

Table 1

Conclusions

These EPAP levels have improved gas exchange without aditional abdominal distension. These preliminary results of high survival should mean that an adequate level of EPAP has been chosen.