Application of pseudo random binary sequence input to identification of respiratory control dynamics

A new method for studying the chemical control of breathing in man is described which uses a Pseudo Random Binary Sequence (PRBS) inhalation of CO2. Impulse responses of endtidal CO2, minute ventilation, tidal volume, inspiratory and expiratory durations were estimated by cross-correlating outputs with the PRBS input. Data collected in seven normal men suggest that impulse responses may be useful in isolating the contribution of peripheral chemoreceptors. Estimates of peripheral sensitivity to CO2 based on PRBS show significantly smaller intrasubject variability than those based on sinusoidal test inputs. Application of a Nelder-Mead parameter estimation procedure demonstrated that a third order model is sufficient to explain impulse response dynamics.