Clinical Heterogeneity among Patients with Obesity Hypoventilation Syndrome: Therapeutic Implications

Abstract

Background: Obesity hypoventilation syndrome (OHS) can be treated with noninvasive positive pressure ventilation (NIPPV). Once clinical stability is achieved, continuous positive airway pressure (CPAP) can be recommended in many cases. However, some patients respond only partially to CPAP and NIPPV is a better option for them. Objectives: To assess treatment effectiveness in 2 groups of patients: those who could be switched to CPAP after polysomnographic titration and those who required NIPPV. Methods: A prospective study of 24 OHS patients was conducted, 11 were treated with CPAP and 13 with NIPPV. Morning and evening arterial blood gases were measured. Daytime and overnight oximetric recordings were performed. A post hoc analysis compared both groups. Results: Neither group exhibited deterioration on morning-to-evening blood gases. All patients in the CPAP group presented SaO₂ of less than 90% (CT90%) for <15% of the time on nocturnal and daytime recordings. In the NIPPV group, 8 patients had either daytime or nocturnal CT90% ≧15%. There were no intergroup differences regarding age, body mass index, Epworth scale values or PaO₂/PaCO₂ prior to treatment. FVC in the NIPPV group was lower than in the CPAP group (p = 0.01). Apnea-hypopnea index was higher (56 ± 23 vs. 36 ± 23, p = 0.049) and baseline CT90% was lower (76 ± 19% vs. 92 ± 14%, p = 0.03) in the CPAP group. Conclusions: Two patient subtypes can be identified. Those controlled with CPAP have better spirometry and a significantly higher apnea-hypopnea index. None of these patients showed daytime hypoxemia and all exhibited satisfactory overnight oxygenation. However, 61% of the NIPPV group had suboptimal oximetry results. Nocturnal/diurnal oximetries should be made to assess treatment efficacy in stable OHS patients who fail to achieve good control with CPAP.

An evaluation of the role of noninvasive positive pressure ventilation in the management of acute respiratory failure in a developing country

“…Previous studies have reported improvements in clinical and biochemical endpoints in patients with obesity hypoventilation syndrome (OHS). [12,13] Although we were unable to further evaluate our patients to document the coexistence of OHS, this area warrants further study.…”

Upper Airway Mechanics

“…Patients may demonstrate a spectrum of findings: episodes of obstruction, hypoventilation or sustained obstructive hypoventilation due to partial upper airway obstruction [81]. We do not know why some obese patients develop OHS, while others do not, nor do we fully understand the pathogenesis of OHS, although it is almost certainly multifactorial in nature [82]. Some authors suggest that OHS is a mixed disorder of ‘can’t breathe’ (unable to overcome impediments to breathing resulting from derangements in lung function or the performance of the respiratory muscles) and ‘won’t breathe’ (decreased ventilatory drive disorder) [83,84,85].…”

“…Some authors suggest that OHS is a mixed disorder of ‘can’t breathe’ (unable to overcome impediments to breathing resulting from derangements in lung function or the performance of the respiratory muscles) and ‘won’t breathe’ (decreased ventilatory drive disorder) [83,84,85]. Ventilatory muscle dysfunction, abnormal load responsiveness, increased respiratory work and CO 2 production, impaired central respiratory drive and repeated airway occlusion during sleep are all possible pathophysiological components in this entitity, but the precise contribution of each remains to be fully clarified [81, 82, 86, 87]. Different responses to CPAP or non-invasive positive pressure ventilation (NIPPV) might reflect an intriguing possibility: the weight of the different pathophysiological mechanisms may vary in individuals with OHS.…”

“…On the other hand, other patients might stand out as having moderate or severe restrictive pulmonary defects and considerable nocturnal desaturation with low AHI values. These patients would require long-term NIPPV [82, 88]. …”

Obesity Hypoventilation Syndrome

“…Arter kan gazında solunumsal asidoza bağlı HCO 3 düzeyinde yükselme sıktır. Yapılan çalışmalarda OUAS tanısı alan hastaların kan gazlarında serum bikarbonat seviyesinin 27 mEq/L üstünde olmasının OHS için duyarlılığı %92, özgüllüğü %50 saptanmıştır (24). Polisomnografide en belirgin bulgu ciddi uzun süreli desatürasyonlardır.…”