Effects of high-frequency chest wall oscillation on respiratory control in humans

[Effects of high frequency chest wall oscillatory (HFCWO) therapy on gas exchange and ventilation in healthy participants]

INTRODUCTION

Chest physiotherapy is an essential part of the treatment of respiratory diseases with increased respiratory secretion and ineffective cough. To date, there have been no studies on the effect of high frequency chest wall oscillatory (HFCWO) therapy on respiratory muscle strength, ventilation and gas exchange. The aim of this study was therefore to assess these three factors in healthy participants.

METHODS

Respiratory muscle strength was measured before and immediately after HFCWO therapy in 25 healthy participants. During the treatment, we continuously measured ventilation parameters, gas exchange, oxygen saturation and heart rate. All participants underwent HFCWO sessions twice (with 24hours difference) with the same procedure. Symptoms during the session and discomfort were measured with the visual analog scale (VAS).

RESULTS

HFCWO therapy produced a change in breathing pattern with increased ventilation associated with altered gas exchange. Heart rate also increased, with no changes in oxygenation. There was no effect, either beneficial or deleterious, on the strength of respiratory muscles. Up to 20% of participants reported substantial discomfort (VAS≥5/10) during the session.

CONCLUSIONS

This study shows that, during the application of HFCWO therapy in healthy participants, ventilation and heart rate increased. However, there were undesirable effects on gas exchange with a high degree of intolerance among volunteers, with no effects on respiratory muscle strength.

High frequency chest compression effects heart rate variability

High frequency chest compression (HFCC) supplies a sequence of air pulses through a jacket worn by a patient to remove excessive mucus for the treatment or prevention of lung disease patients. The air pulses produced from the pulse generator propagates over the thorax delivering the vibration and compression energy. A number of studies have demonstrated that the HFCC system increases the ability to clear mucus and improves lung function. Few studies have examined the change in instantaneous heart rate (iHR) and heart rate variability (HRV) during the HFCC therapy. The purpose of this study is to measure the change of HRV with four experimental protocols: (a) without HFCC, (b) during Inflated, (c)HFCC at 6Hz, and (d) HFCC at 21Hz. The nonlinearity and regularity of HRV was assessed by approximate entropy (ApEn), a method used to quantify the complexities and randomness. To compute the ApEn, we sectioned with a total of eight epochs and displayed the ApEn over the each epoch. Our results show significant differences in the both the iHR and HRV between the experimental protocols. The iHR was elevated at both the (c) 6Hz and (d) 21Hz condition from without HFCC (10%, 16%, respectively). We also found that the HFCC system tends to increase the HRV. Our study suggests that monitoring iHR and HRV are very important physiological indexes during HFCC therapy.