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Table 2 Relationship between lung volumes and AHI after adjustment for BMI by multiple regression analysis in males

From: Impact of obstructive sleep apnea on lung volumes and mechanical properties of the respiratory system in overweight and obese individuals

Model Step Explanatory variable Standardized coefficients t p Partial correlation Collinearity statistics
Included variables Beta Tolerance VIF
1 First (Constant)   −4.830 <0.001    
BMI 0.441 6.782 <0.001 0.441 1.000 1.000
2 Second (Constant)   −3.271 0.001    
BMI 0.413 6.297 <0.001 0.416 0.963 1.039
ERV −0.143 −2.188 0.030 −0.157 0.963 1.039
3 (Constant)   −1.943 0.054    
BMI 0.408 6.156 <0.001 0.408 0.943 1.060
FRC −0.136 −2.043 0.042 −0.147 0.943 1.060
   Excluded variables       
A First age 0.042 0.615 0.539 0.045 0.921 1.086
height 0.026 0.402 0.688 0.029 0.998 1.002
weight 0.102 0.716 0.475 0.052 0.207 4.830
TLC −0.077 −1.183 0.283 −0.086 1.000 1.000
RV 0.000 −0.008 0.993 0.000 0.991 1.009
IC 0.045 0.679 0.498 0.049 0.946 1.057
VC −0.085 −1.318 0.189 −0.095 0.999 1.001
  1. Dependent variable: apnea + hypopnea index (AHI). Independent variables: age, height, weight, body mass index (BMI) and total lung capacity (TLC), inspiratory capacity (IC), vital capacity (VC), residual volume (RV), expiratory reserve volume (ERV) or functional residual capacity (FRC). Models 1 and 2 derived from ERV; Models 1 and 3 derived from FRC combined with other independent variables. Variables shown in Model A were excluded variables and were derived from the first of the regression analysis with AHI as dependent and ERV or FRC combined with other independent variables