Table 5

Functional residual capacity (FRC) values in the upright seated position and FRC change from reclined to upright

PatientsControlsp Value for difference between patient and control groups
FRC seated (litres)Median (IQR)2.84 (2.30 to 3.15)2.92 (2.54 to 3.84)0.31†
FRC seated (% predicted)Median (IQR)84.0 (73.0 to 104.0)99. 5 (86.5 to 112.3)0.02†
FRC change from reclined to upright (litres)Median difference
0.21 (0.1 to 0.37)0.235 (–0.08 to 0.43)0.88
p Value for difference between paired (reclined and upright) values for each group<0.01‡<0.01‡
  • *Of the 21 patients with upright FRC measurements, 6 did not have reclined FRC measurements, as they did not tolerate reclining for a prolonged period wearing the facemask; so there are 15 patients with paired upright and reclined measurements.

  • †p Value calculated using Mann-Whitney U test.

  • ‡p Value calculated using Wilcoxon matched pairs test.