[A comparison of the continuous positive airway pressures produced by two systems].

OBJECTIVE To compare the generation of continuous positive airway pressure using a hand-made device (underwater seal) or a ventilator (Inter 3). METHOD Two positive airway pressure generation systems were compared through laboratory simulations. Measurements were not considered if the mechanical ventilator required calibration or in the presence of gas flow variation (flowmeter sphere oscillation). Recordings were assessed in terms of the capacity to produce the desired pressure (3, 5 and 6 cmH2O) when submitted to three different flow values (8, 10 and 12 l/min). For that end, Student's t test for paired samples and the nonparametric Man-Whitney test for independent samples were employed. RESULTS We verified that the systems behave in different manners under the same conditions of flow and positive end expiratory pressure. For the mechanical ventilator, the mean pressure behavior under continuous positive airway pressure at 3 cmH2O with flows of 8, 10 and 12 l/min were 2.26+/-0.41, 2.22+/-0.37, 2.04+/-0.41, respectively; under positive end-expiratory pressure at 5 cmH2O we found 3.96+/-0.41, 3.87+/-0.43 and 3.75+/-0.52; and under positive end-expiratory pressure at 6 cmH2O the values recorded were 4.94+/-0.40, 4.85+/-0.41 and 4.72+/-0.37. For the underwater seal, the mean pressure behavior under continuous positive airway pressure at 3 cmH2O with flows of 8, 10 and 12 l/min were 4.24+/-0.24, 4.46+/-0.26, 4.72+/-0.37, respectively; at 5 cmH2O the values were 5.97+/-0.17, 6.28+/-0.18, 6.47+/-0.31; and at 6 cmH2O we recorded 6.85+/-0.20, 7.17+/-0.29 and 7.53+/-0.31. All the comparisons were statistically significant (p = 0.000). CONCLUSION Through our recordings it was possible to observe that the Inter 3 continuous positive airway pressure system was more stable than the underwater seal.