By Anastasios F. Palamidas, Pulmonologist, Scientific Associate, Department of Interventional Pulmonology at the Athens Medical Center
Obesity is a very serious public health problem and its complications with regards to the respiratory system play a very important role in the mortality rate of this syndrome.
Obesity is defined by a body mass index, or BMI, and is classified as moderate, severe, and if the BMI exceeds 40 (kg/m2) as morbid obesity.
The prevalence of the syndrome was calculated in a French study, accounting for about 10-12% of the general population of each European country, and has been steadily rising over the past decades.
Complications of the respiratory system involving obese patients
Despite the magnitude of the problem, complications of the respiratory system involving obese patients have begun to appear in medical articles and magazines only in the last 40 years.
As always, prose and science fiction precede science, and so, if we look at the bibliography, the first report of an obese patient with respiratory disturbances is found in Charles Dickens' 1836 texts, published under the title Posthumous Papers of the Pickwick Club. Only 120 years later, a Bickelmann publication attempted to interpret the physiological mechanisms of apnea and the hypoventilation syndrome observed in these patients, especially the hero of the Dickens book. Thus, the name Pickwick Syndrome has since been used to describe obese patients with respiratory problems.
Obesity is a serious risk factor for respiratory diseases. It generates respiratory disorders, in the mechanism of breathing, respiratory muscle strength, gas exchange, respiratory center control and fitness for exercise. In obese patients, gases of the blood, that is oxygen (necessary for keeping the organs alive) and carbon dioxide (that needs to be discharged from the body), as well as a disorder in their levels, are proportional, directly, to the body mass index. On a chronic basis these disorders lead to chronic respiratory insufficiency and permanent disability.
The main mechanisms for blood gas disorders are mismatches in blood supply ventilation and the hypoventilation observed in these patients (commonly referred to as obesity hypoventilation syndrome).
The hypoventilation syndrome is the result of mainly two pathophysiological mechanisms, inefficient coupling between the respiratory muscles and the thoracic cage, and reduced respiratory rate defined by the respiratory center in the central nervous system.
Finally, two other very important conditions that we often find in these patients and which can potentiate the hypoventilation syndrome are chronic obstructive pulmonary disease and obstructive sleep apnea.
Hypoventilation obesity syndrome is usually under-diagnosed and diagnosis is either when the patient is admitted to the hospital with respiratory problems or when diagnosed with Sleep Apnea Syndrome. Studies show that this syndrome is associated with increased mortality while hypoxemia (low oxygen) and hypercapnia (increased carbon dioxide) may have complications, such as pulmonary hypertension and pulmonary heart disease.
The latest therapies include, in particular, oxygen therapy adjusted for the patient and non-invasive mechanical ventilation by a positive or alternating pressure machine.
