Acute cardio-respiratory changes induced by hyperpnoea using a respiratory muscle trainer

Abstract

The aim of this study was to examine the cardio-respiratory effects of voluntary hyperpnoea using a respiratory muscle trainer (RMT) with three different sized rebreathing bags. In particular, the effects of hyperpnoea on inspired and end-tidal gas concentrations were determined. Seven adult males completed three 30 min bouts of hyperpnoea using optimal, oversized and undersized rebreathing bags. Inspired (F _I) and expired end-tidal (F _ET) O₂ and CO₂ concentrations, arterial O₂ saturation (S _AO2) and heart rate were measured during hyperpnoea. Before and after a bout of hyperpnoea, pulmonary function and blood pressure (BP) were assessed. Data were analysed using a two-way repeated-measures ANOVA, with p < 0.05 considered significant. Three subjects experienced discomfort during hyperpnoea and stopped after 20 min. During hyperpnoea, the F _ETCO2 was maintained at 4.6 ± 0.7% irrespective of bag size. The increase in F _ICO2 over time reached 0.5 ± 0.5% at 20 min. The F_IO2 fell to 19.4 ± 0.8% at 20 min, and S_AO2 decreased to 97%. Heart rate and systolic BP increased slightly, but independently of rebreathing bag volume. No changes in pulmonary function or diastolic BP were found. It is concluded that the RMT maintained a constant F _ETCO2 at the expense of a mild hypoxia. The acute effects of hyperpnoea on the cardio-respiratory system are generally mild, but not always tolerable for 30 min.

Keywords:

• Isocapnia
• Hypoxia
• Respiratory muscle training
• Lung function
• Heart rate