Distortion Correction in Open Circuit Respiration Systems

In open circuit respiratory systems an error in dynamic response is introduced by dilution of expired gases in the chamber volume. This dampened response presents no problem for steady-state measurements and is a desired characteristic for long-term monitoring of oxygen consumption. However, this dampened response seriously distorts results for dynamic measurements. To compensate for this error, the chamber can be modeled as a first-order linear system and solved for responses of the subject. Our technique enables rapid determination, from noisy sampled data, of values necessary to compute this corrected response, which is shown to reflect actual dynamics more accurately than an uncorrected response. To demonstrate that the corrected dynamic response yields accurate long-term results, we give an example in which total oxygen consumed (integral under dynamic curve) over an event is computed with and without the corrections; the 2 methods differ by