Table 3. Effects of different CPAP levels on breathing pattern in COPD patients.

CPAP (cmH2O)	RR (b/min)	Ti (s)	Ti/Ttot	Vt (L)	Ve (L/min)	Vt/Ti (L/s)
SB	17.43±1.11	3.74±0.26	1.50±0.10	0.41±0.01	0.72±0.05	11.86±0.88
4	21.15±1.53*	3.12±0.22*	1.37±0.11	0.44±0.02*	0.92±0.06*	18.81±1.36*
5	22.93±1.93*#	3.03±0.27*	1.43±0.13	0.48±0.02*	1.05±0.07*#	22.68±1.66*#
6	23.24±1.78*#	2.90±0.26*#	1.31±0.13*	0.46±0.02*	1.02±0.08*#	22.63±1.94*#
7	22.55±1.51*	2.81±0.19*	1.28±0.09*	0.46±0.02*	0.96±0.08*	20.87±1.78*
8	24.31±1.75*#§	2.77±0.23*#	1.29±0.10*†	0.47±0.02*	1.01±0.08*	23.75±2.26*#§
9	24.06±1.69*#§	2.77±0.19*#	1.24±0.09*†	0.45±0.02*	0.90±0.08*†‡	21.40±2.22*
10	25.73±1.98*#‡§	2.66±0.21*#†	1.22±0.09*#†	0.46±0.02*	0.85±0.07†‡	21.57±2.36*
F value	10.438	3.817	2.583	6.101	11.808	10.481
P value	<0.001	0.008	0.041	<0.001	<0.001	<0.001

Data are presented as mean ± SE unless otherwise stated; P results of repeated analysis of variance (ANVOA) comparison between different CPAP levels; *P<0.05 vs. steady breathing; ^#P<0.05 vs. 4 cmH₂O level; ^†P<0.05 vs. 5 cmH₂O level; ^‡P<0.05 vs. 6 cmH₂O; ^§P<0.05 vs. 7 cmH₂O level; ^ÄP<0.05 vs. 8 cmH₂O level; ^▲P<0.05 vs. 9 cmH₂O level. CPAP, continue positive airway pressure; RR, respiratory rate; Ttot, respiratory cycle time; Ti, inspiratory time; Ti/Ttot, inspiratory duty ratio; Vt, tidal volume; Ve, minute ventilation; Vt/Ti, inspiratory flow; SB, stable breathing.