| Popis: |
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), but caution must be utilized. The purpose of this study was to investigate the effect of airway compliance on Vt delivered by HFOV to the adult patient. Method: An in vitro model was used to simulate an adult passive patient with ARDS, using a high fidelity breathing simulator (ASL 5000, IngMar Medical). The simulation included independent lung ventilation with a fixed resistance and adjustable compliance for each lung. Compliances of 10, 15, 20 and 25 ml/cmH2O were used and resistance (Raw) was fixed at 15 cm H2O/L/s. The ventilator SensorMedics 3100B (Cardinal Health, Dublin, Ohio) was set to a fixed power setting of 6.0, insp-% of 33%, bias flow =30 L/min, and 50% oxygen and Hz of 5.0 (n=5) for each compliance setting. Mean airway pressure (mPaw) and amplitude (AMP) varied as the 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. 10. Data Analysis: The data analysis was performed using SPSS v. 10 to determine the statistical significance of the delivered Vt with different compliances, different AMP and a fixed power setting. A probability of (p < 0.05) was accepted as statistically significant. Results: The average delivered Vt with each compliance was 124.181 mL (range of 116.4276 mL and 132.6637 mL) and average AMP of 84.85 cm/H2O (range 82.0 cm/H2O and 88.0801 cm/H2O) n=5. There was an inverse relationship between Vt and AMP at a fixed power of 6.0. 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 tidal volume and AMP at a fixed power setting. When the post hoc Bonferroni test was used the data showed significant differences between AMP achieved with each compliance change and a fixed power of 6.0. When the post hoc Bonferroni test was used the data showed significant differences between Vt delivered with each compliance change and a fixed power setting of 6.0. Conclusion: Vt is not constant during HFOV. Compliance is one determinant of Vt in adults with ARDS during HFOV. AMP and Vt are inversely related during HFOV at a fixed power setting and improving compliance. |
