2001 OPEN FORUM Abstracts
A BENCH COMPARISONOF FOUR NASAL CPAP PASSOVER HUMIDIFIERS
J. Lewarski,BS, RRT, G. Austin, Eng., RC Medical, Inc. and TAGA Medical, Inc., Ohio.
Background: Nasal continuouspositive airway pressure (CPAP) is an accepted treatment for individuals withmoderate to severe obstructive sleep apnea. Previous studies show that patientcompliance with CPAP treatment can be as low as 45%. The studies suggest thereare a number of primary contributors to low patient compliance, including oro-nasopharynxdrying. Providing humidity in-line to the CPAP delivery system is the standardtreatment. Although a number of CPAP humidifiers are available, there is limitedinformation regarding performance. The purpose of this study was to comparethe humidity outputs of 3 commercial and one prototype CPAP humidity systems.
Methods: We studied 3 commercialnon-heated passover style humidifiers and one manufacturer?s molded prototype(TAGA Velocity®). Using a Respironics Bi-PAP® S/T as theflow generator, standard 18 inch and 6 foot smooth bore tubing, a flow resistorwith a leak placed distal to the flow generator, mimicking mask CPAP, and acalibrated hygrometer, we measured relative humidity (RH) levels at the patientinterface. Ambient temperature and humidity levels were recorded prior to thestart of each phase of the testing. CPAP generator output humidity measurementswithout a humidifier in-line acted as the baseline for each test. A 5-minutestabilization period was maintained before sampling output humidity. Pressureand flow settings were selected to represent a typical range of CPAP pressuresused in clinical practice. Pressure and flow was verified using a Timeter analyzer,model RT-200. The increase in mean output RH over ambient was compared usingrepeated measures ANOVA. Pairwise multiple comparisons were performed with Tukeytest.
Results: Data represent themean of 3 complete measurements/unit.
|CPAP Pressure& Flow Rate||Humidifier||Ambient Temp.¼F||Ambient R.H.||Output R.H.||Increase inR.H. Over Ambient|
|10cmH20 ~90L/min||TAGA Velocity¨||70.9||47.4||75.8||60.1%|
|Nellcor PuritanBennett S-616386-00-A||71.0||47.9||63.6||33.0%|
|15cmH20 ~130L/min||TAGA Velocity¨||73.3||40.3||73.7||83.1%|
|Nellcor PuritanBennett S-616386-00-A||72.5||41.2||58.03||40.6%|
The TAGA unit demonstrated a significantlyhigher humidity gain compared to all other units (p < 0.004). The Respironicsunit had a higher gain than the ResMed and Nellcor units (p < 0.05). Pressures/flowsmeasured at patient interface were consistent to those measured at the outletof the CPAP generator, showing that the humidifiers created little back-pressure.
Conclusions: All devices testedincreased the output humidity levels. Units with a baffling system (TAGA &Respironics) consistently performed better than non-baffled units. Further researchis needed to established standards for CPAP humidification testing and to determinethe effects of humidity use on patient complaints and overall nasal CPAP compliance.