A new breath-holding test may noninvasively reveal early lung abnormalities caused by smoking and/or obesity.
BACKGROUND
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.


METHODS
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], >or= 25 kg/m(2); range, 25.0 to 37.2 kg/m(2)); 19 overweight smokers (1 female smoker; BMI range, 25.2 to 33.5 kg/m(2)); and 8 ex-smokers (BMI range, 20.8 to 24.1 kg/m(2)). A modified pulse oximeter was employed for measuring the fall in pulse oximetric saturation caused by 20-s breath-holding (dSpo(2)) at resting end expiration in the sitting posture.


RESULTS
In healthy subjects, dSpo(2) had no significant correlation with age (r(2) = 0.009; p = 0.66). In smokers, dSpo(2) correlated with both the number of pack-years (r(2) = 0.590; p < 0.001) and closing volume (CV)/vital capacity (VC) ratio (r(2) = 0.573; p < 0.001). In overweight nonsmokers, dSpo(2) increased significantly with BMI alone (r(2) = 0.667; p < 0.001). In overweight smokers, the largest increase in the mean dSpo(2) was observed. Multiple linear regression analysis suggested that BMI and CV/VC are the two major contributing factors determining dSpo(2) during breath-holding. In young former smokers, no significant increase in the mean dSpo(2) was observed (p = 0.77) a mean (+/- SD) duration of 5.2 +/- 2.9 years after the cessation of smoking. No significant difference in dSpo(2) was observed between men and women.


CONCLUSIONS
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.
Divisions of Pulmonary Medicine, Allergy, and Rheumatology, Department of Internal Medicine, Iwate Medical University School of Medicine, Morioka, Japan. Electronic address: hinoue@iwate-med.ac.jp.
Hiroshi
H
Inoue
Divisions of Pulmonary Medicine, Allergy, and Rheumatology, Department of Internal Medicine, Iwate Medical University School of Medicine, Morioka, Japan.
Kohei
K
Yamauchi
Divisions of Pulmonary Medicine, Allergy, and Rheumatology, Department of Internal Medicine, Iwate Medical University School of Medicine, Morioka, Japan.
Hitoshi
H
Kobayashi
Divisions of Pulmonary Medicine, Allergy, and Rheumatology, Department of Internal Medicine, Iwate Medical University School of Medicine, Morioka, Japan.
Toshiki
T
Shikanai
Divisions of Pulmonary Medicine, Allergy, and Rheumatology, Department of Internal Medicine, Iwate Medical University School of Medicine, Morioka, Japan.
Yutaka
Y
Nakamura
Diabetes and Metabolism, Department of Internal Medicine, Iwate Medical University School of Medicine, Morioka, Japan.
Jo
J
Satoh
Department of Molecular and Internal Medicine, Graduate School of Biomedical Science, Hiroshima University, Hiroshima, Japan.
Nobuoki
N
Kohno
Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Michiaki
M
Mishima
Akita University of Nursing and Welfare, Akita, Japan.
Hidetada
H
Sasaki
Department of Physiology and Biophysics, University of Washington, Seattle, WA.
Jack
J
Hildebrandt
D000328:Adult; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007320:Inspiratory Capacity; D007321:Inspiratory Reserve Volume; D016014:Linear Models; D008171:Lung Diseases / Q000175:diagnosis* / Q000209:etiology; D008297:Male; D008451:Maximal Voluntary Ventilation / Q000502:physiology*; D015999:Multivariate Analysis; D009765:Obesity / Q000150:complications*; D010101:Oxygen Consumption / Q000502:physiology; D011336:Probability; D012016:Reference Values; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D013147:Spirometry; D014797:Vital Capacity / Q000502:physiology; D055815:Young Adult