Table 3.

Pulmonary characteristics

	Overlap Syndrome n = 12	COPD Only n = 47	OSA Only n = 9	Former Smoker Controls n = 21	P Value
Daytime pulmonary measures
COPD GOLD Stage
Stage 1, n, %	1 (8)	3 (7)	0 (0)	0 (0)
Stage 2, n, %	8 (67)	19 (42)	0 (0)	0 (0)
Stage 3, n, %	2 (17)	12 (27)	0 (0	0 (0)
Stage 4, n, %	1 (8)	11 (24)	0 (0)	0 (0)
FEV1/FVC, %	61.1 ± 10.5	48.7 ± 12.0*†	76.4 ± 4.5*†	79.7 ± 4.8*†	<0.001
FEV1, % predicted	57.1 ± 17.7	49.6 ± 21.0	80.3 ± 17.1*†	97.3 ± 17.3*†‡	<0.001
Daytime resting O2 saturation, %	92.2 ± 2.5	93.0 ± 3.3	93.7 ± 3.3	94.4 ± 2.6	0.18
O2 use while sitting, n, %	5 (42)	19 (40)	1 (11)	0(0)	0.003
6MWT, total distance walked, m	389 ± 83	395 ± 102	461 ± 120	514 ± 86*†	<0.001
Nocturnal continuous pulse oximetry
O2 use during nocturnal recording, n, %	9 (75)	27 (60)	3 (33)	1 (5)	<0.001
CPAP use during nocturnal recording, n, %	8 (67)	0 (0)	3 (33)	0 (0)	<0.001
Mean Nocturnal $\mathrm{S}{\mathrm{p}}_{{\mathrm{O}}_2}$, %	89.4 ± 5.4	91.0 ± 4.4	90.9 ± 1.7	90.2 ± 2.5	0.64
Oxygen desaturation index (ODI)	0.10 ± 0.1	0.11 ± 0.1	0.19 ± 0.2	0.18 ± 0.1	0.08
Time spent $\mathrm{S}{\mathrm{p}}_{{\mathrm{O}}_2}$ <88, %	27.9 ± 33.5	25.2 ± 33.2	14.3 ± 15.1	16.2 ± 22.5	0.51

Data are means ± SD. COPD, chronic obstructive pulmonary disease; GOLD, global initiative for chronic obstructive lung disease; FEV₁, forced expiratory volume in one second; FVC, forced vital capacity; CPAP, continuous positive airway pressure; O₂, oxygen; $\mathrm{S}{\mathrm{p}}_{{\mathrm{O}}_2}$, peripheral blood oxygen saturation. One-way analysis of covariance (ANCOVA) tests were used for all continuous variables and χ² tests were used for categorical variables.*P < 0.05 vs. overlap syndrome group; †P < 0.05 vs. COPD group; ‡P < 0.05 vs. OSA group. n = number of subjects.