Respiratory variation of the ballistocardiogram during increased respiratory load and voluntary central apnoea.

Heavy snoring is associated with increased respiratory variation of the ballistocardiogram (BCG). The cause for this association is not known. Although the BCG is a sensitive method to measure myocardial performance, the validity of the signal as a marker of snoring-related haemodynamic changes has not been tested. The aim of this study was to investigate whether ballistocardiographic respiratory variation (BRV) correlates with intrathoracic pressure variation (IPV). The BRV and the IPV were measured in five healthy, normal-weight, awake adults during normal breathing, during breath-holding with constant intrathoracic pressure, and during breathing against increased respiratory resistance (high IPV). The BCG was recorded with the static charge-sensitive bed (SCSB) and the intrathoracic pressure with an oesophageal balloon. The mean BRV was significantly lower during central apnoea than during free breathing (8.2 versus 29.4% p less than 0.0001). When breathing against increased respiratory load, the BRV increased in a linear manner as function of the IPV (r = 0.68, p less than 0.01). There was significant interindividual variation in the response. We conclude that changes in the BRV reflect changes in the IPV. Further studies are needed to evaluate whether the BCG could be used as a noninvasive alternative to the oesophageal balloon in monitoring changes of respiratory resistance during heavy snoring.