Chest
Original ResearchLung Aeration During Sleep
Section snippets
Subjects
Ten healthy, nonsmoking subjects (7 men and 3 women; mean age, 34 ± 10 years [± SD]) were investigated awake and during sleep. Three additional men (mean age, 38 ± 16 years) were studied awake in order to develop the CT scan protocol. Informed consent was obtained from all subjects, and the regional ethics committee approved the study protocol in advance.
Spirometry and Airway Closure
Pulmonary function tests were performed in the afternoon with the subjects awake (Vmax 229; SensorMedics; Yorba Linda, CA). Spirometry was
Spirometry and Airway Closure
Characteristics of the subjects and spirometric data are given inTable 1. The spirometric findings (vital capacity and FEV1) and CV (supine position) were normal. However, as expected the FRC and ERV measured in the supine position were lower than reference values acquired in the upright position. CV-ERV was close to zero, indicating airway closure near to, and in some subjects above, the FRC level.
Awake
No significant change regarding gas/tissue ratio was seen in any of the four ROIs over the 4-cm
Discussion
In the present study, using a novel approach of CT, new data have been obtained regarding aeration of the lung during sleep. The results indicate the occurrence of what has previously been anticipated but not shown, namely an increased lung density and loss of air in the dependent lung region during sleep.
Acknowledgments
The authors are grateful for the assistance of Maj Olofsson and Lena Nilsson, radiograph technicians, Anders Persson, MD, PhD, and Pia Franberg, physicist.
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The authors have no conflicts of interest to disclose.
This study was supported by grants from the Swedish Medical Research Council (No. 5315), the Swedish Heart and Lung Foundation, the Uppsala County Association Against Heart and Lung Diseases, and the Mid Sweden's Research and Development Centre.