The Science Journal of the American Association for Respiratory Care

2009 OPEN FORUM Abstracts

THE EFFECT OF LUNG COMPLIANCE CHANGES ON DELIVERED TIDAL VOLUME AND AMPLITUDE IN AN ADULT PATIENT VENTILATED WITH HIGH FREQUENCY OSCILLATORY VENTILATION: A BENCH MODEL

John England, Lynda Goodfellow, Arzu Ari, Robert Harwood, Yong Wang; Respiratory Therapy, Georgia State University, Atlanta, GA

Clinical concerns exist regarding the delivered tidal volume (Vt) during high-frequency oscillatory ventilation (HFOV). HFOV is increasingly being used as a lung protective mode of ventilation for patients with Adult Respiratory Distress Syndrome (ARDS). The purpose of this study was to investigate the effect of lung compliance on Vt delivered by HFOV to an adult patient. Method: An in-vitro model was used to simulate an ARDS patient using a high fidelity breathing simulator (ASL 5000,IngMar Medical,Pittsburgh,PA). The simulation included independent lung ventilation with a fixed resistance of 15 cm H2O/L/s and adjustable compliances of 10, 15, 20 and 25 ml/cmH2O. The ventilator SensorMedics 3100B (Cardinal Health,Dublin,Ohio) was fixed at a power setting 6.0,insp-% 33, bias flow 30 L/min, oxygen 50% and Hz of 5.0 for each compliance setting (n=5). Vt and amplitude (AMP) varied as compliance changes were made. Approximately 250 breaths were recorded at each compliance setting and the data was collected via the host computer and transferred to a log to be analyzed by SPSS v.16. Data Analysis: The data analysis performed included descriptive statistics, One-way ANOVA, Post Hoc Bonferroni test and Pearson Correlation Coefficient to determine the statistical significance (p < 0.05) of the delivered Vt and different AMP at different compliance settings. Results: As compliance improved Vt increased and there was a corresponding decrease in AMP. The one-way ANOVA test showed that there were significant differences between the delivered Vt and AMP. When the Post hoc Bonferroni test was used the data showed significant differences between AMP achieved with each compliance change. Pearson Correlation Coefficient showed that there was a significant inverse relationship between Vt delivered and the AMP readings. Conclusion: Vt is not constant during HFOV. Compliance is one determinant of Vt in adults with ARDS during HFOV. An ARDS patient suffers from very non-compliant lungs. As shown by this study, if the patient’s lung compliance improves so will the Vt delivered at a lower ventilating pressure. Lower ventilating pressures and smaller tidal volumes are considered the proper ventilating strategies for ARDS patients. AMP and Vt are inversely related during HFOV, therefore the patient may receive a larger Vt at a lower ventilating pressure as compliance improves. Sponsored Research - None

Amplitude and Vt at each Compliance Setting

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