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.

Respiratory Functions in Textile Mill Workers: Role of Peak Expiratory Flow Rate

“…An increased BMI also plays a significant role in increasing health-related issues. Obese people generally presented with higher respiratory rated and lower tidal volumes [22] similar to this study since after comparing this study population on the basis of BMI there was the decreased level of FVC, FEV 1 and PEFR were observed in those having increased BMI (>25 kgm 2 ). PEFR generally depends on the various factors, i.e., age, sex, and height [23].…”

The Dose-Response Relationship Between Body Mass Index and Mortality in Subjects Admitted to the ICU With and Without Mechanical Ventilation

“…Second, obese patients may have been intubated earlier because of their body habitus rather than the severity of their illness. 32,33 Third, the care given to obese patients may be different from normal-or under-weight patients. For example, obese patients may be more carefully observed and treated.…”

Airway management and oxygenation in obese patients

“…5 Alterations in respiratory physiology include increased oxygen consumption, higher respiratory rates, reduced lung volumes (most notably functional residual capacity), significantly higher minute ventilation, reduced total respiratory system compliance, and increased airway resistance (Table). 6 The association of obesity with widening of the alveolararterial O 2 gradient appears to be due to ventilation-perfusion mismatch caused by microatelectasis, particularly when the patient is in the supine position. Following induction of general anesthesia in morbidly obese patients, the functional residual capacity decreases by approximately 50% compared with preanesthetic values.…”

“…5 Parmi les changements au niveau de la physiologie respiratoire, citons une augmentation de la consommation d'oxygène, une fréquence respiratoire plus élevée, une réduction de la capacité pulmonaire (et tout particulièrement de la capacité résiduelle fonctionnelle), une ventilation minute significativement plus élevée, une réduction de la compliance totale du système respiratoire et une résistance accrue des voies aériennes (tableau). 6 L'association entre obésité et élargissement du gradient d'O 2 alvéolaire-artériel semble être due à une inadéquation ventilation-perfusion provoquée par une microatélectasie, particulièrement lorsque le patient est en position dorsale. Après l'induction de l'anesthésie générale chez les patients obèses morbides, la capacité résiduelle fonctionnelle diminue d'environ 50 % par rapport aux valeurs préanesthésie.…”