The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

THE EFFECT ON VARYING INSPIRATORY FLOW AND AIRWAY RESISTANCE ON CONTINUOUS POSITIVE PRESSURE (CPAP) MACHINES

Daniel Fisher BS RRT, Yuji Fujino MD, Peggi Robart RRT, and Robert M. Kacmarek Ph.D. RRT. Anesthesia and Respiratory Care, Massachusetts General Hospital and Harvard Medical School, Boston MA

INTRODUCTION: Continuos positive airway pressure (CPAP) is frequently used for the treatment of obstructive sleep apnea (OSA). We have evaluated the ability of 4 CPAP machines to maintain the desired level of CPAP distal to a resistor in the airway during inspiration at various inspiratory flow rates and resistances.

Methods: The units studied were: Respironics Solo and BiPAP S/T (Respironics, Murrysville, PA) Sullivan V (ResMed Corp. San Diego, CA), and Tranquility Quest (Healthdyne Technologies, Marietta, GA). The CPAP unit was connected to a spontaneously breathing test lung (SMC AR200, SMC Inc. Tokyo, Japan) at two different airway resistances (5 cmH_{2}O/L/s and 20 cmH_{2}O/L/s) and three levels of CPAP 4, 8 and 12 cmH_{2}O. Airway pressure and flows were monitored by inline transducer and pneumontachometer distal to the resistor. The signal was then digitized and recorded using WINDAQ software (DATAQ Instruments, Akron, OH). Results: The data was analyzed using a two way ANOVA with the p < 0.05 Pharyngeal pressure ± standard deviation (cmH_{2}O) at the various flows and Raw are presented below:

Flow LPM 30 60

Raw 5 20 5 20

Solo

4 2.5±0.03 -1.4±0.04 -2.4±0.04 -5.5±0.00

8 5.5±0.03 -1.5±0.00 1.7±0.08 -1.4±0.04

12 9.5±0.12 -1.3±0.03 5.8±0.04 2.7±0.03

Sullivan

4 1.4±0.04 0.6±0.04 -2.7±0.53 -5.6±0.06

8 4.7±0.04 3.8±0.04 0.7±0.00 -2.1±0.03

12 8.8±0.04 8.0±0.03 4.4±0.03 1.5±0.03

Tranquility

4 0.8±0.04 -0.0±0.04 -3.0±0.05 -6.1±0.04

8 5.5±0.04 4.2±0.04 1.2±0.03 -2.0±0.18

12 9.1±0.03 8.2±0.05 5.6±0.05 2.3±0.03

BiPAP

4 2.3±0.15 1.4±0.03 -1.5±0.04 -4.5±0.06

8 6.2±0.08 5.4±0.05 2.1±0.04 -1.0±0.04

12 10±0.04 9.3±0.59 5.7±0.03 2.6±0.03

Flow LPM 90

Raw 5 20

Solo

4 -8.0±0.04 -14±0.03

8 -3.4±0.20 -9.0±0.06

12 1.3±0.05 -4.4±0.04

Sullivan

4 -8.7±0.00 -14±0.06

8 -5.5±0.06 -11±0.04

12 -1.7±0.09 -7.1±0.06

Tranquility

4 -9.4±0.06 -15±0.03

8 -4.6±0.06 -11±0.04

12 -0.5±0.04 -6.5±0.04

BiPAP

4 -7.4±0.11 -13±0.08

8 -3.8±0.06 -9.7±0.05

12 -0.3±0.06 -6.1±0.09

CONCLUSION: As the inspiratory flow demand and pharyngeal resistance increased, the pressure measured distal to the pharynx during inspiration decreased significantly (p < 0.001) within all three flow groupings. Significant differences (p < 0.001) existed between machines at each flow settings.

The 44th International Respiratory Congress Abstracts-On-Disk®, November 7 - 10, 1998, Atlanta, Georgia.

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