Table 2

Physiological variables at baseline and at the end of FiO2 0.28 and FiO2 0.50 tests

 FiO2 0.28FiO2 0.50
Room air baseline20 minAdj. p valueRoom air baseline20 minAdj. p value
OHS group
SpO2 (%)94±399±194±3100±0
PavCO2 (kPa)7.1±0.67.4±0.60.0137.2±0.67.7±1.00.012
pH7.371±0.0197.359±0.0270.406*7.373±0.0217.346±0.0300.011
VE (L/min)9.9±2.39.9±2.80.9979.6±2.19.3±2.90.224*
VD/VT (ratio)0.28±0.050.29±0.030.0120.29±0.050.32±0.050.012
VDphys (mL)200±55196±26>0.999194±56192±37>0.999
VT (mL)633±149597±1290.012578±105489±1070.012
RR (br/min)17.5±5.218.2±4.7>0.99918.1±4.918.1±4.2>0.999
Control group
SpO2 (%)98±1100±198±1100±0
PavCO2 (kPa)5.5±0.45.6±0.20.7265.4±0.35.4±0.4>0.999
pH7.408±0.0237.397±0.010>0.9997.407±0.0207.407±0.023>0.999
VE (L/min)7.5±1.67.5±1.7>0.9997.6±1.88.6±1.90.019
VD/VT (ratio)0.27±0.050.29±0.040.0120.28±0.040.32±0.040.012
VDphys (mL)232±79237±530.085*244±123263±970.085*
VT (mL)813 (353)754 (356)>0.999751 (285)751 (264)>0.999
RR (br/min)10.3±4.210.5±4.50.195*10.6±3.711.8±3.60.195*
  • Data presented as mean±SD or median (IQR).

  • Adj. p value: significance level from general linear model analysis, change over time (ie room air vs oxygen) after Holm's Bonferroni correction (refer to table E1, online supplement for full details).

  • *Raw p value significant but adj. p value=non-significant.

  • FiO2, inspired oxygen fraction; PavCO2, arterialised-venous carbon dioxide; RR, respiratory rate; SpO2, pulse oxygen saturation; VD/VT, physiological dead space to tidal volume ratio; VDphys, physiological dead space; VE, minute ventilation; VT, tidal volume.