Resonant frequency does not predict high-frequency chest compression settings that maximize airflow or volume

The effects of high-frequency chest compression on end-tidal CO2

INTRODUCTION

High-frequency chest compression (HFCC) is used for airway clearance, but may have other effects. We sought to determine if HFCC provides augmented ventilation.

METHODS

During treatment, capnometry was measured with the HFCC vest set to 6-20 Hz. End-tidal CO₂ (etCO₂ ) was compared using generalized estimating equations.

RESULTS

Twenty-four measurements were obtained from 15 subjects with mean age 15.2 ± 2.5 years and forced expiratory volume in one second (FEV₁ ) % predicted 70 ± 23. EtCO₂ decreased with HFCC at 6 Hz when compared with baseline (P < .001), with small changes with increasing oscillation frequency. Change in etCO₂ was not predicted by FEV₁ , body mass index, age, or sex.

CONCLUSIONS

While HFCC has been shown to be a suitable method of airway clearance, investigators have failed to demonstrate differences between techniques. Assessment of these methodologies will become important as new airway clearance devices are proposed. Other outcome measures (besides FEV₁ ) may be needed to assess effects of airway clearance, and we propose that physiologic measures might be one such measure which deserves further exploration.