Smoking and obesity are leading global causes of death. The aim of the present study was to develop a test to detect early lung abnormalities caused by smoking and/or obesity and to elucidate the underlying mechanisms and major contributory factors.
One hundred twenty-nine healthy adults, 20 to 40 years of age, with normal spirometry findings, were divided into the following five groups: 38 healthy subjects (15 female subjects); 46 smokers (5 female smokers); 18 overweight nonsmokers (2 female nonsmokers; normal body mass index [BMI], ≥ 25 kg/m2; range, 25.0 to 37.2 kg/m2); 19 overweight smokers (1 female smoker; BMI range, 25.2 to 33.5 kg/m2); and 8 ex-smokers (BMI range, 20.8 to 24.1 kg/m2). A modified pulse oximeter was employed for measuring the fall in pulse oximetric saturation caused by 20-s breath-holding (dSpo2) at resting end expiration in the sitting posture.
In healthy subjects, dSpo2 had no significant correlation with age (r2 = 0.009; p = 0.66). In smokers, dSpo2 correlated with both the number of pack-years (r2 = 0.590; p < 0.001) and closing volume (CV)/vital capacity (VC) ratio (r2 = 0.573; p < 0.001). In overweight nonsmokers, dSpo2 increased significantly with BMI alone (r2 = 0.667; p < 0.001). In overweight smokers, the largest increase in the mean dSpo2 was observed. Multiple linear regression analysis suggested that BMI and CV/VC are the two major contributing factors determining dSpo2 during breath-holding. In young former smokers, no significant increase in the mean dSpo2 was observed (p = 0.77) a mean (± SD) duration of 5.2 ± 2.9 years after the cessation of smoking. No significant difference in dSpo2 was observed between men and women.
A new test that measures oxygen saturation during breath-holding reveals early lung abnormalities in subjects who either smoke or are overweight, especially if these factors are combined. Peripheral airway abnormalities and/or lung volume reduction may play roles in the greater desaturation.