Obesity alters the topographical distribution of ventilation and the regional response to bronchoconstriction.
- Publisher:
- AMER PHYSIOLOGICAL SOC
- Publication Type:
- Journal Article
- Citation:
- Journal of applied physiology (Bethesda, Md. : 1985), 2020, 128, (1), pp. 168-177
- Issue Date:
- 2020
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Obesity is associated with reduced operating lung volumes that may contribute to increased airway closure during tidal breathing and abnormalities in ventilation distribution. We investigated the effect of obesity on the topographical distribution of ventilation before and after methacholine-induced bronchoconstriction using single-photon emission computed tomography (SPECT)-CT in healthy subjects. Nine obese and 10 non-obese subjects underwent baseline and post-bronchoprovocation SPECT-CT imaging, in which Technegas was inhaled upright followed by supine scanning. Lung regions that were non-ventilated (Ventnon), low-ventilated (Ventlow) or well-ventilated (Ventwell) were calculated using an adaptive threshold method and were expressed as a percentage of total lung volume. To determine regional ventilation, lungs were divided into upper, middle and lower thirds of axial length derived from CT. At baseline, Ventnon and Ventlow for the entire lung, were similar in obese and non-obese subjects. However, in the upper lung zone, Ventnon (17.5±10.6% vs. 34.7±7.8%, p<0.001) and Ventlow (25.7±6.3% vs. 33.6±5.1%, p<0.05) were decreased in obese subjects with a consequent increase in Ventwell (56.8±9.2% vs. 31.7±10.1%, p<0.001). The greater diversion of ventilation to the upper zone was correlated with BMI (rs=0.74, p<0.001), Rrs (rs=0.72, p<0.001), and Xrs (rs=-0.64, p=0.003), but not with lung volumes or basal airway closure. Following bronchoprovocation overall Ventnon increased similarly in both groups, however in non-obese subjects Ventnon only increased in the lower zone, whereas in obese subjects Ventnon increased more evenly across all lung zones. In conclusion, obesity is associated with altered ventilation distribution during baseline and following bronchoprovocation that are independent of reduced lung volumes.
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