The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

The Effects Of Varying Set Humidifier Temperature And Ventilator Flow Rate On The Relative Humidity Delivered By The Fischer & Paykel Mr-730 Heated Humidifier

Russell T. Reid, RRT, Mark Goldstein, RRT, Mercy San Juan Medical Center, Carmichael, California.

This study examined the effect of varying ventilator flow rate and set humidifier temperature on the relative humidity delivered by the Fischer & Paykel (F&P) MR-730 heated humidification system.

Methods: An F&P MR-730 heated humidifier (Auckland, New Zealand) equipped with a model #290 high flow humidification chamber and 72" dual heated wire circuit (Hudson RCI Model 780-32, Temecula, CA) was attached to a Hamilton Veolar (Reno, Nevada) mechanical ventilator. The mechanical ventilator was placed in the volume control mode with a square inspiratory flow wave form. A heated humidity chamber (HC), 37.3 Cº (±1.8Cº), was constructed to accommodate the probe of a capacitance type digital hygrometer (Curtin-Matheson Scientific, Brisbane, CA, Model # 244-355). Inspiratory gas passed through the HC for relative humidity measurement. The heated wire controller was set for 0 Cº temeprature differential between the humidifier chamber and the proximal airway. A thermocouple themometer (Baxter Inc, Duo Temp) continuously displayed temperature from two areas within the ventilator circuit 1) adjacent to the F&P MR-730 humidifier chamber temperature probe and; 2) adjacent to the humidifier temperature probe on the inspiratory side of the patient wye. Stabilized, repeat measures were collected at 1 minute intervals until 10 measurements at each variation of temperature and set ventilator flow rate were complete. Prior to testing all equipment was calibrated to the manufacturer's specifications.

Results: Data was analyzed using Analysis of Variance (ANOVA). Statistical significance existed within and between all groups pɘ.0001.

Set VentilatorHygrometer Relative Absolute Humidity

Temperature Flowrate TemperatureHumidity (mg H_2O/L ±SD)

(Cº) (L/min)(Cº ±SD) (%±SD)

32 40 31.41 (±0.08) 99.36 (±0.76) 32.60 (±0.25)

34 40 32.16 (±0.57) 97.15 (±2.10) 33.42 (±0.71)

36 40 34.87 (±0.47) 94.21 (±1.72) 37.14 (±0.64)

38 40 36.23 (±0.28) 97.08 (±0.94) 41.12 (±0.39)

32 60 31.30 (±0.22) 99.07 (±0.72) 32.27 (±0.23)

34 60 32.90 (±0.15) 100.0 (±0.00) 35.58 (±0.00)

36 60 34.52 (±0.08) 95.38 (±0.80) 36.77 (±0.29)

38 60 38.43 (±0.07) 100.0 (±0.0) 47.45 (±0.00)

32 80 31.24 (±0.05) 99.83 (±0.19) 32.51 (±0.06)

34 80 32.73 (±0.12) 99.68 (±0.30) 35.21 (±0.11)

36 80 34.51 (±0.23) 96.74 (±0.75) 37.57 (±0.28)

38 80 37.51 (±0.68)100 (±0.0)45.16 (±0.00)

32 10031.18 (±0.30) 99.46 (±0.52) 32.16 (±0.17)

34 10032.82 (±0.54)100.0 (±0.0) 35.32 (±0.00)

36 10035.02 (±1.26) 95.89 (±0.75) 38.07 (±0.29)

38 10036.31 (±0.09) 99.28 (±0.60) 42.06 (±0.25)

Conclusion: The F&P MR-730 met the American National Standards Institute (ANSI) heated humidifier output standard of 30 mg H_2O/L under all test conditions.

OF-95-160

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