Comparison of Albuterol Delivery between High Frequency Oscillatory Ventilation and Conventional Mechanical Ventilation in a Simulated Adult Lung Model using Different Compliance Levels

COMPARISON OF ALBUTEROL DELIVERY BETWEEN HIGH FREQUENCY OSCILLATORY VENTILATION AND CONVENTIONAL MECHANICAL VENTILATION IN A SIMULATED ADULT LUNG MODEL USING DIFFERENT COMPLIANCE LEVELS By Waleed A. Alzahrani, BSRT BACKGROUND: Delivery of aerosol by pMDI has been described with conventional mechanical ventilation (CMV) but not with high frequency oscillatory ventilation (HFOV). The purpose of this study was to compare aerosol delivery to a simulated 75 kg adult with low compliance during both CMV and HFOV. Since actuation of pMDI with inspiration is not feasible with HFOV, we investigated the impact of actuation timing only during CMV. METHOD: CMV (Respironics Esprit) and HFOV (Sensor Medics 3100B) ventilators with passover humidifiers and heated circuits were connected by 8 mm ID ETT and filter (Respirgard II, Vital Signs) to a test lung (TTL) with compliance settings of 20 and 40 ml/cm H2O in order to simulate a non compliant lung. Settings for CMV (VT 6 ml/kg, I:E 1:1, PEEP 20 cm H2O, and RR 25/min), and HFOV (RR 5 Hz, IT 33%, ∆P 80 cm H2O and mPaw 35 cm H2O) were used, with similar mPaw on CMV and HFOV. Parameters were selected based on ARDSnet protective lung strategy (Fessler and Hess, Respiratory Care 2007) Eight actuations of albuterol from pMDI (ProAir HFA, Teva Medical) with double nozzle small volume spacer (Mini Spacer, Thayer Medical) placed between the “Y” adapter and ETT at more than 15 sec intervals for each condition (n=3). During CMV, pMDI actuations were synchronized (SYNC) with the start of inspiration at more than 15 s, and nonsynchronized (NONSYNC) with actuations at 15 s intervals. Drug was eluted from the filter and analyzed by spectrophotometry (276 nm). Repeated measures ANOVA, pairwise comparisons and independent t- tests were performed at the significance level of 0.05. RESULTS: In all cases, aerosol delivery was greater with HFOV than CMV (p\u3c0.05). Synchronizing pMDI actuations with the beginning of inspiration increased aerosol deposition significantly at compliance levels 20 ml/cm H2O and 40 ml/cm H2O (p=0.011 and p=0.02, respectively). Lung compliance and aerosol delivery are directly related. Increasing lung compliance to 40 ml/cmH2O improved aerosol delivery during CMV and HFOV (p\u3c0.05). CONCLUSION: Albuterol deposition with pMDI was more than two fold greater with HFOV than CMV in this in-vitro lung model. Changing lung compliance has almost 2 fold impact on aerosol delivery during both modes of ventilation. Furthermore, synchronizing pMDI actuations during CMV improved aerosol delivery up to 4 fold