Inspiratory occlusion pressure as a measure of hypoxic ventilatory drive (1178.14)

The pressure generated during the first 0.1 sec of an occluded inspiration (P 0.1 ) has been proposed as a measure of neural ventilatory drive that is independent of respiratory mechanics. We attempted to validate P 0.1 as a measure of hypoxic ventilatory drive against traditional measurement of the isocapnic hypoxic ventilatory response (HVR). Ten healthy subjects breathed through a mask and non‐rebreathing valve. The HVR ([[Unsupported Character ‐ Symbol Font □]]Ventilation / ‐[[Unsupported Character ‐ Symbol Font □]]Sa O 2 ) was measured when inspired O 2 decreased from 30% to 10% and end‐tidal P CO2 was held constant 2‐3 Torr above the level measured on 30% O 2 . The change in P 0.1 (averaged over 3 randomly occluded breaths) was measured under the same conditions. HVR averaged 0.87 + 0.62 L/(min %) and the change in P 0.1 with hypoxia was 0.16 + 0.12 cm H 2 O/%; the two responses were not correlated across all subjects. HVR was < 0.10 in 3 subjects but only 2 of these subjects had a low P 0.1 response (<0.06) and another subject with a P 0.1 response < 0.06 had HVR > 0.10. Reanalysis of previous HVR data collected in our laboratory shows the HVR is not significantly different within subjects (n=6) between 2 trials in 1 day, or between 4 trials over 4 days. Additional measurements of P 0.1 hypoxic response reproducibility are necessary to evaluate if it can be used to test for time‐dependent changes in the HVR of patients with hypoxemia from chronic lung disease. NIH RO1 HL‐081823, P01 HL‐098053 and CAPES‐10326/12‐0 Grant Funding Source : NIH RO1 HL‐081823, P01 HL‐098053 and CAPES‐10326/12‐0