Another interesting observation derived from this study is based on the comparison of selected values among patients. It is obvious that the conversion to HFPV rapidly improved the Pa02/Fl02 ratio, increased the MAP, and decreased the PIP as shown by the comparison of the last value recorded before HFPV with the first value after initiation of HFPV. This improvement was sustained over the next 2 days, as shown by the significant difference between the last value in the three parameters before HFPV and the last value in the 48-h period after conversion to HFPV. However, it seems that the maximal effect of HFPV is achieved rapidly and further improvement is hard to document on the basis of the current number of patients; this is shown by the absence of a significant difference between the first and the last value of these three parameters during the monitored period of HFPV. asthma inhaler
The combination of continuous pneumatic percussions with the partially deflated cuff allows for a dramatic mobilization of secretions and clearance of lung infiltrates. The effect of delivering high-frequency percussions on the clearance of secretions may be analogous to that of highly effective chest physical therapy (which is rarely possible in the setting of critically ill patients). It seems that there is no adverse effect on circulatory function. As most studies have only compared cardiac outputs, we decided to incorporate in our analysis parameters that reflect the circulatory function but are more specific for oxygen transport and tissue perfusion information. Oxygen delivery, consumption, and extraction ratio were not affected by the conversion to HFPV. Similarly, the mean arterial pressure remained unchanged.
The results of this nonrandomized study must be approached with caution. The course of the disease if the patients had been left on CV is not known. The rate of change per hour of different respiratory parameters demonstrated ongoing deterioration before HFPV.
Tags: ARDS, high-frequency percussive ventilation, mean airway pressure, oxygen consumption, oxygen delivery, Pao2/fraction of inspired oxygen, peak inspiratory pressure