Environmental Perturbations: Obesity

Abstract

Obesity currently affects about one third of the U.S. population, while another one third is overweight. The importance of obesity for certain conditions such as heart disease and type 2 diabetes is well appreciated. The effects of obesity on the respiratory system have received less attention and are the subject of this chapter. Obesity alters the static mechanic properties of the respiratory system leading to a reduction in the functional residual capacity (FRC) and the expiratory reserve volume (ERV). There is substantial variability in the effects of obesity on FRC and ERV, at least some of which is related to the location, rather than the total mass of adipose tissue. Obesity also results in airflow obstruction, which is only partially attributable to breathing at low lung volume, and can also promote airway hyperresponsiveness and asthma. Hypoxemia is common is obesity, and correlates well with FRC, as well as with measures of abdominal obesity. However, obese subjects are usually eucapnic, indicating that hypoventilation is not a common cause of their hypoxemia. Instead, hypoxemia results from ventilation perfusion mismatch caused by closure of dependent airways at FRC. Many obese subjects complain of dyspnea either at rest or during exertion, and the dyspnea score also correlates with reductions in FRC and ERV. Weight reduction should be encouraged in any symptomatic obese individual, since virtually all of the respiratory complications of obesity improve with even moderate weight loss.

Impact of intermittent hypoxia and exercise on blood pressure and metabolic features from obese subjects suffering sleep apnea-hypopnea syndrome

“…On the other hand, it has been reported that obesity impairs pulmonary functional capacities and causes airflow obstruction, poor arterial oxygenation, or hypoventilation [42], and it is related to SAHS [49]. All these conditions may benefit from weight loss induced by behavioral interventions [15] or bariatric surgery [27], and also by lifestyle strategies including dietary and physical activity interventions [4].…”

Obesity is associated with severe disease and mortality in patients with coronavirus disease 2019 (COVID-19): a meta-analysis

“…Finally, obesity results in physiological lung alterations, such as decreased functional residual capacity and hypoxemia [ 67 ]. In addition, obstructive sleep apnoea hypopnea syndrome (OSAHS) increases adverse outcomes of COVID-19 [ 68 ].…”

Oxidative stress in the lung – The essential paradox

“…Obesity can cause or exacerbate numerous respiratory conditions including reduction in lung volume, hypoxia, dyspnea, and increased bronchial hyperresponsiveness, and can reduce the effectiveness of inhaled corticosteroids and increase susceptibility to asthma. The inflammatory responses and hypoxemia caused by obesity increase production of ROS, precipitate tissue injury, and disrupt mitochondrial respiratory chain control (44). Sepsis is a state of acute inflammation that affects the lung in an indirect manner.…”