2005 OPEN FORUM Abstracts
CIRCUIT COMPLIANCE COMPENSATION FACTORS REMAIN CONSTANT OVER TIME.
Denise Lawson, RRT; John Heinz, RRT; Ira M. Cheifetz, MD, FAARC Respiratory Care Services and Pediatric Critical Care Medicine Duke Children's Hospital, Durham, North Carolina
Background: The ventilator circuit compliance is a significant factor in determining the fraction of the ventilator delivered tidal volume that actually reaches a patient's lungs. Traditionally, this factor has been calculated by the bedside respiratory therapist. Fourth generation ventilators perform this function during the initial setup process. However, the stability of this calculated factor over time remains unknown. Changes in temperature and humidity could theoretically be significant variables. Thus, we evaluated the stability of the circuit compliance compensation factor over 72 hours. We hypothesized that despite warming and humidification of the inspired gas, circuit compliance compensation factors do not change over time.
Methods: Stability of the circuit compliance compensation factor was evaluated for neonatal, pediatric, and adult circuits. Each circuit was run in triplicate on three different AVEA ventilators (Viasys Healthcare). An appropriate sized test lung was used for each circuit (neonatal - Rusch; pediatric - Bio-Med; adult - Siemens). The initial setup included a dry non-heated circuit. Data were collected for each circuit when dry, after introduction of heat and humidity (Fisher Paykel 840), and then every 24 hours for three days. For each data collection point, five circuit compliance compensation calculations were performed with the results averaged.
Results: Data were compared by analysis of variance with correction for repeated measures. For each circuit type, the circuit compliance compensation factor remained constant over the course of data collection (p = ns). Data are represented as the mean value (ml/cm H2O) ± standard deviation.
|Dry circuit||1.6 ± 0.04||2.3 ± 0||3.3 ± 0|
|Humidified circuit||1.4 ± 0.05||2.2 ± 0||3.1 ± 0|
|Humidified @ 37ºC||1.4 ± 0||2.2 ± 0||3.2 ± 0.04|
|Humidified @ 37ºC at 24 hrs||1.4 ± 0||2.2 ± 0||3.3 ± 0.04|
|Humidified @ 37ºC at 48 hrs||1.4 ± 0||2.2 ± 0||3.3 ± 0.04|
|Humidified @ 37ºC at 72 hrs||1.4 ± 0||2.2 ± 0.05||3.3 ± 0|
Conclusion: Circuit compliance compensation factors remained constant over 72 hours despite heating and humidification of the inspired gas. Practitioners may use these parameters when setting the AVEA ventilator, but, more importantly, practitioners can rely on the stability of these compensation factors over time despite heat and humidity.