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
N21*30
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†
N15*30
FRC change from reclined to upright (litres)Median difference
(IQR)
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.