Circadian dynamics of respiratory parameters from ambulatory monitoring

Knowledge of respiratory activity is of interest in patients with cardiac, pulmonary and neurological diseases; moreover, it is helpful for a proper evaluation of the autonomic nervous system influence on cardiac activity. To achieve 24-hour recording of ECG and respiratory activity an original solution was provided by the use of a piezoelectric transducer (PVDF) implemented in a FM 2-channel Holter recorder. A computer program for the dynamic analysis of the respiratory signal over the 24 hours, oriented to the detection of apnea and to the derivation of the clinically most significant parameters (such as respiratory rate, tidal volume, total inspiratory and expiratory time), was developed and applied in a preliminary group of 13 normal controls. A night-time decrease in respiratory rate was observed due to an increase in both inspiratory and expiratory time, together with a corresponding decrease in tidal volume presumably related to reduced metabolic demand. An analysis of the influence of the respiratory rate and the "computed tidal volume" upon R-R spectral indexes was performed.<>