Nocturnal Oxygen Desaturation Index is Inversely Correlated with Airflow Limitation in Patients with Chronic Obstructive Pulmonary Disease

Figures & data

Table 1.  Baseline characteristics of subjects

	All patients, n = 103
Age, mean (SD), years	72 (8)
Male, n (%)	91 (88)
BMI, mean (SD), kg/m^2	22 (3)
Underlying co-morbidity
Hypertension	40 (39)
Diabetic mellitus	15 (15)
Heart failure	16 (16)
Coronary artery diseases	12 (12)
Cerebral infarction	9 (9)
Smoking history, median (IQR), pack-years	53 (41–76)
Treatment
LAMA, n (%)	84 (82)
LABA, n (%)	32 (31)
ICS/LABA, n (%)	41 (40)
Oral corticosteroids, n (%)	6 (6)
Theophyline, n (%)	7 (7)

BMI = Body mass index; LAMA = Long-acting methacholine antagonist; LABA = Long-acting beta agonist; ICS = Inhaled corticosteroid.

Table 2.  Medical conditions associated with COPD

	All patients, n = 103
Resting SpO2, mean (SD), %	96 (2)
Exacerbation of COPD within a year, n (%)	29 (28)
CAT, median (IQR)	13 (7–18)
ESS, median (IQR)	5 (3–8)
HADS
Anxiety	3 (1–7)
Depression	6 (2–9)
Pulmonary function test
FEV1, mean (SD), L	1.59 (0.63)
FEV1/FVC, % (SD)	51 (12)
FEV1, mean (SD), % predicted	61 (21)
FVC, mean (SD), L	3.1 (0.9)
FVC, mean (SD), % predicted	95 (23)

SpO₂ = Percutaneous oxygen saturation; COPD = Chronic obstructive pulmonary disease; CAT = COPD assessment test; ESS = Epworth sleepiness scale; HADS = Hospital anxiety and depression scale; FEV₁ = Forced vital capacity in one second; FVC = Forced vital capacity.

Table 3.  Nocturnal oximetry

	All patients, n = 103
Mean SpO2, mean (SD), %	93 (4)
%T90, median (IQR), %	3.3 (0.4–10.4)
ODI, median (IQR)	4 (2–7)
ODI≥5, n (%)	31 (30)
ODII≥10, n (%)	15 (15)
ODII≥15, n (%)	9 (9)

SpO₂ = Percutaneous oxygen saturation; %T90 = Percentage of time of SpO₂ < 90%; ODI = Oxygen desaturation index.

Table 4.  Correlations between ODI and clinical variables

	ODI
	Coefficient	P value
Age	0.11	0.3
BMI	0.05	0.6
Pack-years of smoking	−0.08	0.4
Resting SpO2	0.15	0.1
CAT	−0.15	0.1
ESS	0.05	0.6
HADS
Anxiety	0.05	0.6
Depression	−0.11	0.3
FEV1	0.38	<0.001
FEV1/FVC	0.36	<0.001
FEV1% predicted	0.32	0.001
FVC	0.18	0.07
FVC% predicted	0.15	0.1

Data are Spearman correlation coefficients. ODI = Oxygen desaturation index; BMI = Body mass index; SpO₂ = Percutaneous oxygen saturation; CAT = Chronic obstructive pulmonary disease assessment test; ESS = Epworth sleepiness scale; HADS = Hospital anxiety and depression scale; FEV₁ = Forced vital capacity in one second; FVC = Forced vital capacity.

Figure 1.  Oxygen desaturation index (ODI) by the GOLD (Global Initiative for Chronic Obstructive Lung Disease) classification. ODI was significantly different among GOLD classifications and tended to be higher in the milder GOLD classification groups.

Table 5.  Logistic regression analysis for predictors of ODI ≥ 15

		ODII ≥15
	OR	95% CI	P value
Age (per year)	1.22	1.08–1.42	< 0.001
BMI (per kg/m^2)	1.09	0.87–1.38	0.5
Pack-years of smoking (per pack-years)	0.99	0.96–1.01	0.3
Resting SpO2 (per percent)	1.39	0.87–2.49	0.2
CAT (per score)	0.88	0.77–0.99	0.02
ESS (per score)	1.02	0.86–1.18	0.8
Exacerbation of COPD within a year	0.81	0.10–3.16	0.7
HADS
Anxiety (per score)	0.94	0.73–1.18	0.6
Depression (per score)	0.97	0.79–1.16	0.7
FEV1 (per liter)	2.59	0.91–7.83	0.08
FEV1/FVC (per percent)	1.07	1.00–1.16	0.04
FEV1% predicted (per percent)	1.03	1.00–1.07	0.03
FVC (per liter)	1.42	0.66–3.15	0.4
FVC% predicted (per percent)	1.01	0.98–1.04	0.4

OR = Odds ratio; CI = Confidence interval; ODI = Oxygen desaturation index; BMI = Body mass index; SpO₂ = Percutaneous oxygen saturation; CAT = Chronic obstructive pulmonary disease assessment test; ESS = Epworth Sleepiness Scale; HADS = Hospital Anxiety and Depression Scale; FEV₁ = Forced vital capacity in one second; FVC = Forced vital capacity.

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