Influencing factors and the reference frame for the ratio of residual volume to total lung capacity in the elderly
PAN Jing1, ZHENG Yongke1, DAI Xinjian2, YE Shaoming3
1.Department of Cadres’s Health, Wenzhou Central Hospital, Wenzhou 325000, China; 2.Department of Respiratory, Wenzhou Central Hospital, Wenzhou 325000, China; 3.Pulmonary Function Chamber, Wenzhou Central Hospital, Wenzhou 325000, China
PAN Jing,ZHENG Yongke,DAI Xinjian, et al. Influencing factors and the reference frame for the ratio of residual volume to total lung capacity in the elderly[J]. JOURNAL OF WEZHOU MEDICAL UNIVERSITY, 2019, 49(1): 56-58，62.
Abstract：Objective: To explore the influencing factors and the rationality of the current criteria for judging the ratio of residual volume (RV) to total lung capacity (TLC) in the elderly. Methods: A total of 587 healthy elderly patients were enrolled in this research from January 2016 to January 2018 in Wenzhou Central Hospital. According to the standard, 190 cases including 105 males and 85 females were selected and tested by MasterScreen pulmonary function analyzer. The relevant parameters were recorded for statistical analysis. Results: Age, sex, height and body mass had a significant effect on RV/TLC (P<0.05); age increase had no effect on RV (P>0.05), but had significant effect on TLC (P<0.01). Pearson correlation analysis showed RV/TLC was positively correlated with age (r=0.297, P<0.001), negatively correlated with height (r=-0.329, P<0.001) and body mass (r=-0.246, P=0.001). Multiple stepwise linear regression showed that 3 variables, age, sex and height, entered the regression equation: RV/TLC=41.704+0.253×age+2.240×sex (males=1, females=2) -0.152×height (cm) (r=0.462, F=16.249, P<0.001). There were three different criteria for RV/TLC>35%, Shanghai’s old prediction formulas and new prediction formulas (the ratio of measured value to predicted value is>1.2), the positive rates were 68.95% (131/190), 5.26% (10/190) and 8.42%/(16/190) respectively, and there was statistical difference between each other (P<0.05). Conclusion: Age, sex, height and body mass all had effects on RV/TLC. It is probably unreasonable that RV/TLC>35% is used as a critical point for the elderly and it is suggested that a new prediction formula for the elderly should be established.
