A bench study using an artificial lung model and a clinical study in patients were performed to evaluate six commercially available home pressure support devices. Six devices were tested in the in vitro study, including five designed for home use and one designed for use in intensive care units. Minimal positive end-expiratory pressure (PEEP) varied across home devices, from 0.5 cm H2O to 4.3 cm H2O. Work imposed during exhalation varied up to six-fold across devices. A substantial rebreathing volume has present for the three home devices with a common inspiratory and expiratory line. This rebreathing volume decreased with increasing PEEP level, as expected, but remained substantial at the widely used PEEP level of 5 cm H2O. Use of a non-rebreathing valve increased both the work imposed by the circuit during the exhalation phase and the time required to attain the relaxation equilibrium. Except for two home devices and a bilevel positive airway pressure (BiPAP) device equipped with a non-rebreathing valve, differences in inspiratory trigger sensitivities were small between home and intensive care devices. During pressure support, the total work performed by the machines did not differ by more than 15% between devices, whereas differences of more than 300% were observed in flow acceleration. Only one home device gave a flow acceleration similar to or better than that obtained with the intensive care device. In a randomized, crossover clinical study, we compared a home device to a device specially designed for intensive care use in seven intubated patients during weaning from mechanical ventilation. The main differences between the two devices were trigger sensitivity and initial flow acceleration. For the same level of pressure support, there were no significant differences in arterial PCO2, tidal volume, respiratory rate, or minute ventilation between these two devices. However, the esophageal pressure-time product was 30% higher 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 support level, and expiratory resistance. These differences characterizing the delivery of pressure support may have clinical impact on the inspiratory effort of patients.