The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

EVALUATION OF THE PULSAIR OXYGEN DELIVERY SYSTEM.

Dean Hess, PhD. RRT, Hideaki Imanaka, MD, Robert M. Kacmarek, PhD, RRT. Respiratory Care and Anesthesia, Massachusetts General Hospital and Harvard Medical School, Boston, MA.

Pulse-dose systems sense a pressure drop in the cannula and deliver a pulsed dose of O_2. We evaluated the Pulsair OMS 50 pulse-dose O_2 delivery system (DeVilbiss, Somerset PA) relative to trigger pressure (P_{TR}), trigger delay (T_D), pulse volume delivery (vol), peak flow delivery (V_{PK}), time of active flow from the Pulsair (T_{ACT}), and total time of flow from the cannula (T_{TOT}).

Methods: O_2 pressure into the Pulsair was controlled to 35 or 50 psi with a regulator. An O_2 cannula with 7 ft of tubing was used (Baxter, Valcenia CA) and additional tubing (Baxter, Valcenia CA) was connected to extend the length to 35 ft. The cannula prongs were connected via a Y-piece to a screen pneumotachometer (Hans Rudolf, Kansas City MO) that was calibrated at 0 and 0.25 L/s (Brooks, Hatfield PA). Pressure (±2 cm H_2O, Validyne, Northridge CA) was measured immediately proximal to the pneumotachometer. Pressure and flow signals were digitized (CODAS) at 1000 Hz. Flow leaving the cannula was integrated to volume. P_{TR} was determined by slowly decreasing pressure distal to the pneumotachometer until the Pulsair responded. T_D was determined by producing a large step change in pressure and measuring the time between P_{TR} and Pulsair response. T_{ACT} was measured as the interval from the beginning of flow to V_{PK}, T_{TOT} was measured as the entire time interval of flow from the cannula, and [Delta] T was the difference between T_{ACT} and T_{TOT}. Flow settings of 1, 2, 3, and 4 were evaluated. Statistical analysis consisted of mean ± SD (n=5) and ANOVA.

Results:

flow 50 psi; 7 ft 50 psi; 35 ft35 psi; 7 ft 35 psi; 35 ft

setting T_D vol [Delta]T T_D vol [Delta]T T_D vol [Delta]T T_D vol [Delta]T

154.2± 17.3± 0.099±123.6± 17.6± 0.227±37.6± 13.3± 0.098±121.6± 13.4± 0.190±

2.7 0.040.009 6.3 0.060.009 2.7 0.050.007 3.9 0.030.003

254.2± 34.0± 0.095±126.0± 34.4± 0.267±36.8± 25.8± 0.100±114.2± 26.0± 0.225±

3.3 0.030.002 7.7 0.040.003 1.9 0.020.004 7.5 0.060.017

354.2± 50.4± 0.093±118.0± 50.7± 0.287±41.6± 38.2± 0.105±112.6± 38.4± 0.221±

5.5 0.020.001 2.5 0.050.004 1.1 0.030.008 2.6 0.2 0.002

467.2± 66.6± 0.094±127.0± 66.6± 0.279±40.2± 50.6± 0.118±116.6± 50.7± 0.227±

5.3 0.010.002 3.4 0.060.003 3.1 0.050.001 2.5 0.010.003

Mean P_{TR} for all settings was 0.09 ± 0.01 cm H_2O. T_{ACT} was 0.1 ± 0.003 s, 0.2 ± 0.003 s, 0.2 ± 0.002 s, and 0.4 ± 0.002 s for settings of 1, 2, 3, and 4, respectively. O_2 volume was affected by the driving pressure (P < 0.001) and flow setting (P < 0.001), but was not affected by tubing length (P=0.685). Vdot_{PK} was lower with longer tubing length and lower driving pressure (Pɘ.001 in each case). Differences between T_{TOT} were significant for tubing length (P < 0.001) and driving pressure (P < 0.001).

Conclusions: P_{TR} of the Pulsair was very low ([approx]0.1 cm H_2O). T_D was affected by driving pressure and tubing length and the magnitude of these differences may be clinically important. T_D differences are probably due to the effects of driving pressure and tubing length on the time constant of the system. T_{TOT} was greater than T_{ACT} due to decompression of O_2 from the tubing, and compression and decompression of O_2 in the tubing explains why the O_2 volume delivered was not affected by tubing length. It is important for homecare providers to appreciate the effects of tubing length and driving pressure on the performance of these devices. (Supported in part by DeVilbiss)

OF-95-098

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