Cheyne-Stokes respiration: system identification and computer modeling

Cheyne-Stokes respiration (CSR) is a major cause of ventilatory instability during sleep in patients with heart failure (HF). Dynamic loop gain and delay of the central chemoreflex (CCR) loop was measured during wakefulness in HF patients with and without CSR using a pseudorandom binary CO₂ stimulus (PRBS) method while breathing 100% O₂. The closed-loop and open-loop central chemoreflex loop gain, estimated from the impulse response, was three times greater in patients with nocturnal CSR (n=9) than in non-CSR patients (n=9) or in a group of normal subjects (n=7). Loop dynamics, estimated by absolute delay time and 95% response duration time, did not differ among all three groups. A computational model indicates that a three-fold increase in the CCR loop gain produces periodic breathing (T=57 sec) but with an unrealistic ventilation (V₁)-arterial O₂ saturation (O₂ Sat) phase relationship. A phase relation corresponding to that reported for CSR requires an increase in delay and gain of the peripheral chemoreflex loop (PCR). The results indicate that CSR results from increased gain of the CCR loop as well as alterations of the PCR loop