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Respiratory resistance (Rrs) changes during physical labor can modify the work of breathing and thus influence the time that the labor can be performed. Ideal in vivo human respiratory performance measurements should have fine temporal resolution and minimally impact the respiratory system itself. The airflow perturbation device (APD) provides respiratory resistance measurements in this manner. Pre-exercise Rrs was compared with post-exercise Rrs, continuously monitored for 6 min in 12 non-asthmatic subjects. Rrs following exercise at 70-75% VO2max was below pre-exercise levels for 40 s into recovery (p < 0.05) and inhalation resistance differed more markedly than exhalation resistance. The same post-exercise Rrs decline was found when Rrs measurements were compared to those taken during flow rates comparable to those found late in recovery. Results indicate that (1) Rrs indeed declines following exercise in non-asthmatic subjects, probably due to bronchial dilation, (2) Rrs changes can occur on short time scales, (3) Rrs changes are not related primarily to flow rate.

Absfract-The Airflow perturbation Device (APD) is a new device for measuring respiratory resistance. What makes it different is the convenience and ease of use. The device operates by small changes in respiratory airflow and mouth pressure induced by a rotating wheel in the air now path. Resistance measurements do not require special breathing maneuvers and can be made on small children and unconscious or uncooperative humans and animals. Measurements are sensitive to changes and are reproducible.

Background: The Airflow Perturbation Device (APD) is a lightweight, portable device that can be used to measure total respiratory resistance as well as inhalation and exhalation resistances. There is a need to determine limits to the accuracy of APD measurements for different conditions likely to occur: leaks around the mouthpiece, use of an oronasal mask, and the addition of resistance in the respiratory system. Also, there is a need for resistance measurements in patients who are ventilated.

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