Work of breathing associated with pressure support ventilation in two different ventilators

The purpose of this study was to compare the work of breathing during press ure support ventilation (PSV) with positive end expiratory pressure (PEEP) utilizing the Siemens SV300((R)) (SV300) and Drager Evita 4((R)) (EV4) vent ilators. Our hypothesis was that patients' work of breathing (WOBp) would b e unchanged in PSV utilizing flow triggering (FT) in both the SV300((R)) an d EV4((R)). We compared two ventilators using six healthy, intubated, sedat ed, spontaneously breathing pigs weighing approximately 10 kg each. WOBp (j /L) and ventilator work of breathing (WOBV) (j/L) were measured using a por table monitor which utilizes an esophageal balloon and flow transducer, Eac h breath was further analyzed for duration of inspiratory effort and negati ve deflection of pressure needed to trigger PSV. Animals were studied with the SV300((R)) and EV4((R)) on a pressure support of 5 cmH(2)O and PEEP set tings of 0 and 5 cmH(2)O, Data were analyzed using the Wilcoxon signed rank test with significance set at P less than or equal to 0.05. WOBp was 90% (PS 5, PEEP 0) and 52% (PS 5, PEEP 5) lower on the SV300((R)) compared to the EV4((R)), WOBV was 94% (PS 5, PEEP 0) and 39% (PS 5, PEEP 5 ) higher on the SV300((R)) when compared to the EV4((R)), The change in air way pressure (delta p) from baseline and most negative deflection of pressu re were greater with the EV4((R)) as compared to the SV300((R)), although d elta pressure was not found to be statistically significant on PS of 5 cmH( 2)O and PEEP of 5 cmH20. The SV300((R)) also had shorter duration of inspir atory effort from initiation of breath to most negative deflection of press ure and to maximum flow than the EV4((R)). In conclusion, these results suggest there are significant differences in W OE, between the SV300((R)) and EV4((R)) ventilators. Response time of the v entilators may explain the differences in duration of inspiratory effort an d the patient's work of breathing and thus may have an impact on weaning ti me for ventilated patients. (C) 2001 Wiley-Liss, Inc.