initiating nighttime NIV for chronic hypercapnia in OHS

Untreated obesity hypoventilation syndrome (OHS) increases the risk of morbidity and mortality, particularly in patients who require hospitalization due to acute-on-chronic hypercapnic respiratory failure. These patients frequently are mislabeled as having “COPD exacerbation” or “heart failure.” It is important for clinicians to maintain a high index of suspicion and recognize patients with OHS in a timely fashion in order to institute appropriate therapy. In ambulatory patients with OHS who have concomitant severe OSA, several clinical trials have demonstrated that CPAP is equally effective as NIV modes such as bilevel positive airway pressure (PAP) spontaneous timed (with a backup rate) or volume-targeted pressure support modes of positive pressure ventilation. In contrast, there is growing consensus that hospitalized patients suspected of having OHS who survive an episode of acute-on-chronic hypercapnic failure should be discharged from the hospital on empiric nocturnal NIV while awaiting outpatient workup, such as polysomnography and PAP titration. This patient has experienced multiple admissions due to acute-on-chronic hypercapnic respiratory failure, and each time he has benefited from NIV therapy. It is likely that home nocturnal NIV therapy using empiric pressure settings, similar to the ones used in the hospital, will decrease the chance of readmission (choice B is correct). Although there are challenges in getting health insurance providers to approve home NIV therapy without a sleep study, the fact that this patient has chronic hypercapnic respiratory failure with frequent hospital admissions justifies this therapy. Retrospective data suggest that there is an increase in all-cause mortality at 3 months and 6 months in patients who are not discharged from the hospital with NIV therapy. Although there are no randomized clinical trials exploring the impact of discharge from the hospital with NIV therapy in this patient population, preliminary evidence from observational studies suggests that mortality may be lower in those who are discharged on NIV therapy.

Bariatric surgery is not performed during an acute hospitalization and requires extensive counseling and outpatient workup to ensure the patient is an adequate candidate. Bariatric surgery is an important intervention in patients with OHS because 25% to 30% actual body weight loss can lead to resolution of hypoventilation. Once this patient has been started on home PAP therapy and has demonstrated adequate adherence, it is important to initiate discussion about bariatric surgery (choice A is incorrect).

There are two major phenotypes of OHS. Nearly 70% of patients with OHS have severe concomitant OSA, with an apnea-hypopnea index (AHI) >30. Approximately 10% of patients have minimal OSA (AHI <5) and are “pure hypoventilators.” The remaining 20% of patients have mild to moderate OSA (AHI 5-29). In the phenotype of OHS with severe OSA, tracheostomy alone can resolve upper airway obstruction during sleep and thereby improve OSA and lead to resolution of chronic hypercapnia, similar to CPAP therapy. However, given the lack of a sleep study, at this point it is unclear whether this patient has the phenotype of OHS with severe OSA. Tracheostomy alone, without nocturnal ventilation, is unlikely to improve chronic hypoventilation in the subgroup of patients without severe OSA. Moreover, the patient has had multiple episodes of exacerbation that have responded favorably to NIV therapy and clearly states that he has felt better with it (choice C is incorrect). Some patients may need supplemental oxygen added to PAP therapy, but supplemental oxygen is inappropriate as monotherapy. Moreover, after recovering from the acute phase of hypercapnic respiratory failure, this patient did not have hypoxemia significant enough (SpO2 on room air of 93%) to justify supplemental oxygen therapy (choice D is incorrect).1

Footnotes

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