Table 7. Results of the nocturnal oximetry.

Variable	Cases (n = 40) COPD	Controls (n = 32) Smokers, non-COPD	P
MNSpO2, %	89·0 ± 4·07	92·3 ± 2·2	< 0·0001
CT90, %	48·6 ± 32·7	17·8 ± 21·5	< 0·0001
DI4, n°/h	14·1 ± 13·8	14·1 ± 13·6	0·64
Sawtooth pattern, n, %	15 (37·5%)	14 (43·7%)	0·85

MNSpO₂: mean nighttime oxygen saturation; CT90: percentage of recording time with SpO₂ <90%; DI4: number of dips in SpO₂ ≥4% per hour of recording time.