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Lung aeration during sleep
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
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2007 (English)In: Chest, ISSN 0012-3692, E-ISSN 1931-3543, Vol. 131, no 1, 122-129 p.Article in journal (Refereed) Published
Abstract [en]

Background: During sleep, ventilation and functional residual capacity (FRC) decrease slightly. This study addresses regional lung aeration during wakefulness and sleep. Methods: Ten healthy subjects underwent spirometry awake and with polysomnography, including pulse oximetry, and also CT when awake and during sleep. Lung aeration in different lung regions was analyzed. Another three subjects were studied awake to develop a protocol for dynamic CT scanning during breathing. Results: Aeration in the dorsal, dependent lung region decreased from a mean of 1.14 ± 0.34 mL (± SD) of gas per gram of lung tissue during wakefulness to 1.04 ± 0.29 mL/g during non-rapid eye movement (NREM) sleep (- 9%) [p = 0.034]. In contrast, aeration increased in the most ventral, nondependent lung region, from 3.52 ± 0.77 to 3.73 ± 0.83 mL/g (+ 6%) [p = 0.007]. In one subject studied during rapid eye movement (REM) sleep, aeration decreased from 0.84 to 0.65 mL/g (- 23%). The fall in dorsal lung aeration during sleep correlated to awake FRC (R2 = 0.60; p = 0.008). Airway closure, measured awake, occurred near and sometimes above the FRC level. Ventilation tended to be larger in dependent, dorsal lung regions, both awake and during sleep (upper region vs lower region, 3.8% vs 4.9% awake, p = 0.16, and 4.5% vs 5.5% asleep, p = 0.09, respectively). Conclusions: Aeration is reduced in dependent lung regions and increased in ventral regions during NREM and REM sleep. Ventilation was more uniformly distributed between upper and lower lung regions than has previously been reported in awake, upright subjects. Reduced respiratory muscle tone and airway closure are likely causative factors.

Place, publisher, year, edition, pages
2007. Vol. 131, no 1, 122-129 p.
Keyword [en]
Airway closure, anesthesia, CT, lung aeration, lung volume, sleep, ventilation
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-90214DOI: 10.1378/chest.06-0359ISI: 000243548100020PubMedID: 17218565OAI: oai:DiVA.org:uu-90214DiVA: diva2:162496
Available from: 2003-04-14 Created: 2003-04-14 Last updated: 2011-02-17Bibliographically approved
In thesis
1. Ventilation and Lung Volume During Sleep and in Obstructive Sleep Apnea
Open this publication in new window or tab >>Ventilation and Lung Volume During Sleep and in Obstructive Sleep Apnea
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Obstructive sleep apnea (OSA) appears to affect up to 5% of the population. The extent to what pulmonary function awake and during sleep relates to obstructive breathing and hypoxemia during sleep in these patients is unclear. The aim of this study was to investigate respiratory function in patients with varying degree of snoring and OSA and to analyse regional lung aeration during sleep.

In all, 35 healthy subjects and 90 patients with snoring and OSA were studied. The ventilatory response to CO2 (VRCO2) was measured. Lung function tests were performed. A technique based on computed tomography was developed to study lung aeration during sleep.

Patients with OSA displayed a higher VRCO2 in comparison to healthy subjects and snorers (p<0.01). Increased closing volume and reduced expiratory reserve volume (ERV) were found in patients with OSA (p<0.001). In a multiple regression analysis, ERV was an independent predictor of nocturnal apnea (R2=0.13; p=0.001) and desaturation frequency (R2=0.11; p<0.01). In both healthy subjects and OSA patients, lung aeration was reduced during sleep by 0.10 ml gas/g tissue in the dorsal lung region (p<0.05 and p<0.01). OSA patients had a significantly lower gas/tissue ratio in comparison to healthy subjects both awake (-23%; p<0.04) and during sleep (-25%; p<0.04). In a univariate analysis, functional residual capacity (FRC) correlated with the change in lung aeration from wakefulness to sleep (r=-0.78; p<0.001). In patients with OSA, ERV (r=-0.69; p<0.05) and sleep time (r=0.69; p<0.05) correlated with the fall in lung aeration.

In conclusion, patients with OSA display an increased ventilatory response to CO2, reduced ERV and increased closing volume. ERV predicts nocturnal apnea and desaturation frequency to a similar extent as obesity. Lung aeration is reduced in the dorsal region during sleep and patients with OSA display a lower amount of gas in comparison to healthy subjects. Decrease in lung volumes, promoting airway closure, and loss of muscle tone contributed to the altered lung function during sleep.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 76 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 1246
Physiology, Sleep, Ventilation, Sleep apnea syndromes, Snoring, Lung volume, Respiration, Computed tomography, Ventilatory response, Ventilation-perfusion, Airway closure, Fysiologi
National Category
Research subject
Clinical Physiology
urn:nbn:se:uu:diva-3363 (URN)91-554-5588-3 (ISBN)
Public defence
2003-05-09, Robergsalen, Akademiska sjukhuset, Uppsala, 09:15
Available from: 2003-04-14 Created: 2003-04-14Bibliographically approved

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