Receiver operating characteristics of impulse oscillometry parameters for predicting obstructive sleep apnea in preobese and obese snorers

Table 4 Results of backward and forward stepwise logistic regression for predicting OSAS

Model construct by backward stepwise method	Explanatory variable	B	S.E.	Wald	p-values
First step	Weight	0.019	0.034	0.326	0.568
	BMI	0.067	0.119	0.314	0.575
	ERV	−0.643	0.553	1.354	0.245
	FRC	−0.067	0.526	0.016	0.899
	Sex	3.526	0.946	13.887	0.000
	Zrs5 supine	33.114	11.199	8.742	0.003
	R5 supine	−31.050	11.438	7.369	0.007
	X5 supine	−10.980	3.608	9.259	0.002
	Constant	−10.845	2.790	15.110	0.000
Last step	BMI	0.126	0.057	4.831	0.028
	ERV	−0.658	0.372	3.126	0.077
	Sex	3.761	0.847	19.743	0.000
	Zrs5 supine	33.474	11.223	8.937	0.003
	R5supine	−31.493	11.457	7.556	0.006
	X5supine	−10.814	3.560	9.229	0.002
	Constant	−11.356	2.282	22.774	0.000
Model construct by forward stepwise method
First step	X5 supine	−15.475	2.650	34.094	0.000
First step	Constant	−3.797	0.627	36.654	0.000
Last step	Sex	3.559	0.849	17.572	0.000
	Zrs5 supine	34.100	11.483	8.819	0.003
	R5supine	−31.506	11.723	7.222	0.007
	X5supine	−11.372	3.583	10.076	0.002
	Constant	−12.428	2.240	30.784	0.000

Abbreviations: BMI body mass index, ERV expiratory reserve volume, FRC functional residual capacity, Zrs5 respiratory impedance at 5 Hz, R5 respiratory resistance at 5 Hz, X5 respiratory reactance at 5 Hz. Outcome variable is the probability (p) of the presence of OSAS (RDI ⩾15) / absence of OSAS (RDI <15); namely, ln(p/(1-p)

ISSN: 1471-2466