title: Impact of obesity on respiratory function.
abstract: Obesity has long been recognized as having significant effects on respiratory function. The topic has been studied for at least the last half century, and some clear patterns have emerged. Obese patients tend to have higher respiratory rates and lower tidal volumes. Total respiratory system compliance is reduced for a variety of reasons, which will be discussed. Lung volumes tend to be decreased, especially expiratory reserve volume. Spirometry, gas exchange and airway resistance all tend to be relatively well preserved when adjusted for lung volumes. Patients may be mildly hypoxaemic, possibly due to ventilation-perfusion mismatching at the base of the lungs, where microatelectasis is likely to occur. Weight loss leads to a reversal of these changes. For all of these changes, the distribution of fat, that is, upper versus lower body, may be more important than body mass index.
authors: Pulmonary, Critical Care, and Sleep Medicine, Cook County Hospital and Rush University Medical Center, Chicago, Illinois, USA. slittleton@cookcountyhhs.org
authors: Stephen W
authors: SW
authors: Littleton
mesh_terms: D000403:Airway Resistance; D050218:Body Fat Distribution; D015992:Body Mass Index; D004417:Dyspnea / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D009765:Obesity / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D013147:Spirometry; D035441:Thoracic Wall / Q000503:physiopathology*; D013990:Tidal Volume; D015431:Weight Loss