Obesity hypoventilation syndrome

Abstract

Obesity hypoventilation syndrome (OHS) is defined as a combination of obesity (body mass index ≥30 kg·m−2), daytime hypercapnia (arterial carbon dioxide tension ≥45 mmHg) and sleep disordered breathing, after ruling out other disorders that may cause alveolar hypoventilation. OHS prevalence has been estimated to be ∼0.4% of the adult population. OHS is typically diagnosed during an episode of acute-on-chronic hypercapnic respiratory failure or when symptoms lead to pulmonary or sleep consultation in stable conditions. The diagnosis is firmly established after arterial blood gases and a sleep study. The presence of daytime hypercapnia is explained by several co-existing mechanisms such as obesity-related changes in the respiratory system, alterations in respiratory drive and breathing abnormalities during sleep. The most frequent comorbidities are metabolic and cardiovascular, mainly heart failure, coronary disease and pulmonary hypertension. Both continuous positive airway pressure (CPAP) and noninvasive ventilation (NIV) improve clinical symptoms, quality of life, gas exchange, and sleep disordered breathing. CPAP is considered the first-line treatment modality for OHS phenotype with concomitant severe obstructive sleep apnoea, whereas NIV is preferred in the minority of OHS patients with hypoventilation during sleep with no or milder forms of obstructive sleep apnoea (approximately <30% of OHS patients). Acute-on-chronic hypercapnic respiratory failure is habitually treated with NIV. Appropriate management of comorbidities including medications and rehabilitation programmes are key issues for improving prognosis.

Obesity Hypoventilation Syndrome: New Insights

“…The diagnosis of OHS is made regularly between the fifth and sixth decades of life, and two clinical presentations commonly observed are the patients who are diagnosed during an acute exacerbation of chronic respiratory failure with acute respiratory acidosis leading to hospital admission (often in the intensive or intermediate care unit) and who remain hypercapnic at hospital discharge or during routine patient evaluation for suspected OSA or dyspnoea [28][29][30][31][32] .…”

“…As such, it leads to a higher prevalence and more severe pulmonary hypertension and metabolic syndrome and a higher risk of other cardiovascular events and mortality compared to eucapnic obese patients 30,45 . 28,47,48 .…”

“…The latter prevents upper airway obstructive events but in contrast to NIV, it is not designed to augment ventilation 65 . In patients with OHS and concomitant severe OSA, NIV and CPAP have been shown to be similar in improving daytime symptoms, quality of life, sleep quality, daytime and nocturnal gas exchange status, as well as spirometric and polysomnographic outcomes in medium-term 28,[35][36][37][38][39] and long-term 33,52,66 randomised controlled trials (RCTs).…”

Pickwickian syndrome - "the tip of the iceberg" in extremely obese patients

“…Evidence of right ventricle enlargement from pulmonary hypertension that complicates advanced OHS may be seen on ECG and echocardiogram [9]. History and examination cannot diagnose OHS alone, but it requires the demonstration of daytime hypercapnia [5]. Certain laboratory results complete the anamnesis and physical examination [elevated serum bicarbonate (> 27 mEq/L), hypercapnia (arterial pressure of carbon dioxide PaCO 2 > 45 mmHg), hypoxemia (PaO 2 < 70 mmHg), polycythemia].…”

“…OHS often remains undiagnosed until late in the course of the disease. Its exact prevalence is unknown, but it has been estimated that 10-20% of obese patients with obstructive sleep apnea have hypercapnia [5]. Early recognition is important because these patients have significant morbidity and mortality.…”