The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

Evaluation of the Effects of Long-Term Use on Heated Inspiratory and Non-Heated Disposable Mechanical Ventilator Circuits

Jennifer Keller RRT, Frank Sandusky, RRT and Thomas Kallstrom, RRT, FAARC

Background: In current literature, there are numerous studies that discuss ventilator circuit change intervals. Current strategies promote longer intervals between circuit changes up to and beyond seven days. All are based on bacteriological surveillance. Little is written about the effect, on the circuit after prolonged use. We sought to determine if prolonged use resulted in deleterious effect on the disposable circuit. Method: A PB7200 Ventilator with a Fisher & Paykel MR730 humidifier was utilized during the testing. The PB7200, was set at the following settings: A/C, Vt.6L, Peep 5 cm H2O, Resp. Rate 16 BPM, and humidity set at 37%. The Ventilator was equipped with an Airlife non-heated ventilator circuit and allowed to run for 30 days. At the end of 30 days, the ventilator circuit was change to an Isothermal heated inspiratory breathing circuit. A BIO-TEK adult ventilator test lung was utilized for this study. The test lung was set with a compliance of .010 L/cm H2O and an airway resistance adapter of Rp20. We devised a system to prevent condensation from entering the test lung, and which could be easily removed during test measurements. PIP, MAP and Vt, were recorded. A total of seven circuits were tested. Three non-heated and four heated circuits.

Results:
After 30 days, there was a decline in peak inspiratory pressure for both heated and non-heated circuits of-1 cm H2O. The test lung at the end of 30 days recorded an average increase of .02 Liters for each delivered breath. The system compliance had an average increase of 0.4 ml/cm H2O, with a range of 0.0 to 0.8 ml/cm H2O, with no difference between circuits. Discussion: A significant increase in tubing compliance was not observed in either heated or non-heated circuits. There was no significant difference between the initial delivered volume and that at the end of 30 days. Non heated circuits utilized two (2) liters of water every 24 hours. However, the heated wire circuits required one two (2) liter bag of water ever two (2) days. The cost savings may be enough to justify the purchase of heated wire ventilator circuits. Using disposable ventilator circuits for up to 30 days does not alter the physical attributes of the circuit and is a practice that we now feel can be done without change in ventilation of the patient.

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