HOME VERSUS INTENSIVE-CARE PRESSURE SUPPORT DEVICES - EXPERIMENTAL AND CLINICAL COMPARISON

A bench study using an artificial lung model and a clinical study in p atients were performed to evaluate six commercially available home pre ssure support devices. Six devices were tested in the in vitro study, including five designed for home use and one designed for use in inten sive care units. Minimal positive end-expiratory pressure (PEEP) varie d across home devices, from 0.5 cm H2O to 4.3 cm H2O. Work imposed dur ing exhalation varied up to six-fold across devices. A substantial reb reathing volume was present for the three home devices with a common i nspiratory and expiratory line. This rebreathing volume decreased with increasing PEEP level, as expected, but remained substantial at the w idely used PEEP level of 5 cm H2O. Use of a non-rebreathing valve incr eased both the work imposed by the circuit during the exhalation phase and the time required to attain the relaxation equilibrium. Except fo r two home devices and a bilevel positive airway pressure (BiPAP) devi ce equipped with a non-rebreathing valve, differences in inspiratory t rigger sensitivities were small between home and intensive care device s. During pressure support, the total work performed by the machines d id not differ by more than 15% between devices, whereas differences of more than 300% were observed in flow acceleration. Only one home devi ce gave a flow acceleration similar to or better than that obtained wi th the intensive care device. In a randomized, crossover clinical stud y, we compared a home device to a device specially designed for intens ive care use in seven intubated patients during weaning from mechanica l ventilation. The main differences between these two devices were tri gger sensitivity and initial flow acceleration. For the same level of pressure support, there were no significant differences in arterial PC O2, tidal volume, respiratory rate, or minute ventilation between thes e two devices. However, the esophageal pressure-time product was 30% h igher with the home device (165 +/- 93 versus 119 +/- 80 cm H2O/min, p < 0.05). In conclusion, differences exist between devices in terms of occurrence of rebreathing, speed of attainment of stable pressure sup port level, and expiratory resistance. These differences characterizin g the delivery of pressure support may have clinical impact on the ins piratory effort of patients.