An issue associated with the use of bi-level ventilation is patient compliance. The purpose of this study was to evaluate the performance of a new bi-level embellishment called Bi-Flex, which allows a small amount of pressure relief at the beginning of exhalation to improve patient compliance.
A 2-chambered lung model was used to simulate spontaneous breathing. Pressure and flow were measured immediately proximal to the lung model. IPAP/EPAP settings of 10/8, 15/10, and 16/6 cm H2O were used with 3 levels of Bi-Flex (0 = no pressure relief, 3 = maximal pressure relief). For each combination of settings, the following exhalation parameters were measured: time for pressure to drop from IPAP to EPAP (Time 1), time of pressure relief below EPAP (Time 2), and maximal pressure drop below EPAP. Summary data are provided for 3 breaths.
There was a significant decrease in Time 1 as the Bi-Flex level was increased (0.49 ± 0.09 s for setting 0, 0.25 ± 0.02 s for setting 1, 0.17 ± 0.01 s for setting 2, and 0.14 ± 0.03 s for setting 3; P<0.001). There was no significant change in Time 2 as the Bi-Flex level was increased (0.80 ± 0.11 s for setting 1, 0.81 ± 0.12 s for setting 2, 0.90 ± 0.17 s for setting 3; P=0.29). The pressure drop below EPAP was 0.70 ± 0.17 cm H2O for Bi-Flex setting 1, 1.42 ± 0.19 cm H2O for Bi-Flex setting 2, and 2.29 ± 0.11 cm H2O for Bi-Flex setting 3. These results are illustrated in the figure.CONCLUSIONS: Bi-Flex produces a significant pressure relief at the beginning of the exhalation phase.
The potential for Bi-Flex to improve patient compliance should be subjected to appropriate clinical study.
D.R. Hess, Respironics, Inc., grant monies.