Energy Transfer High Frequency Chest Compression

High frequency chest compression (HFCC) supplies a sequence of air pulses to an inflatable vest-like garment that covers the thorax. The pulses produce oscillatory airflow within the lungs of patients with chronic obstructive lung disease (COLD). The energy produced from the machine and transferred from the vest to the patient’s lungs assists in opening airways and increases air volume flow rate to remove mucus for clearance by expectoration or swallowing. Evaluation of relative efficacy for such a system requires an estimate of the pressure and frequency of the vibration energy transferred from vest to body over the operating range of the system. The purpose of this study is to measure the spatial energy distribution of acceleration applied to the vest/chest wall using a 3-D accelerometer. This study is of two waveforms, sinus and triangle, with two different vests, two pulse pressures, and two frequencies to observe the distribution of energy. The results of energy transfer are presented for three protocols: vest on mannequin, vest on control subject and vest on a CF patient. For both a normal subject and a CF patient, volume airflow and pressure at the mouth are reported as an index of energy coupled to the lungs. Our results show significant differences in the both intra-vest and thoracic energy distribution patterns between the machine-vest systems. The products of estimated energy from the normal subject and CF patient vary with machine settings. The premise that all HFCC machines deliver comparable therapy is called into question. Further studies are needed to analyze machine differences and define optimal performance characteristics.