Obesity Hypoventilation Syndrome

Educational Objectives

The goal of this program is to improve the management of obesity hypoventilation syndrome (OHS). After hearing and assimilating this program, the clinician will be better able to:

1. Evaluate the impact of a ketogenic diet on OHS.

Summary

Obesity hypoventilation syndrome (OHS): affects 8% to 20% of all patients that are referred to sleep centers; diagnostic criteria for OHS include, after ruling out other causes of daytime hypercapnia, presence of obesity, daytime hypercapnia, and sleep-disordered breathing; 90% of patients with OHS also have sleep apnea; of these, 70% have severe sleep apnea, while 30% with no mild to moderate sleep apnea have disproportionate reductions in their oxygenation compared with their age

American Thoracic Society 2019 guidelines: a serum bicarbonate level of <27 mmol/L excludes the diagnosis of OHS in patients with high suspicion; stable outpatients with OHS should receive positive airway pressure (PAP) therapy; hospitalized patients with OHS with acute respiratory failure should have noninvasive ventilation until tested as outpatients; weight loss is critical to managing the underlying obesity (weak recommendation of 25%-30% of weight loss); continuous PAP (CPAP) is preferred over noninvasive ventilation as first-line treatment for the management of OHS and severe sleep apnea; compared with patients with nonhypercapnia, patients with OHS (with same BMI) have a lower quality of life, increased risk for pulmonary hypertension, increased health care expenses, and increased risk for mortality

OHS in literature: improvement of OHS and hypercapnia with a ketogenic diet — crossover study (Osman et al [2023]) concluded that the ketogenic diet improved the carbon dioxide level, apnea severity, and oxygenation; the greater the hypercapnia, the greater the effect observed; the study also reported rebound hypercapnia on resumption of regular diet; however, the rebound was not associated with recurrence of symptoms; no change was observed between the regular and ketogenic diet in patients on PAP; long-term treatment with CPAP compared with noninvasive ventilation — Masa et al (2022) found that long-term noninvasive ventilation therapy was similar to CPAP in improving awake hypercapnia regardless of baseline severity; consider other factors along with the severity of hypercapnia in deciding the type of device used

Obesity sleep-related hypoventilation: is regarded as a precursor to OHS; Sivam et al (2019) found that the predictors of sleep-related hypoventilation included awake upright saturations of ≤93% and supine partial pressure of carbon dioxide (pCO2) levels of ≥45 mm Hg

Effect of altitude: at sea level, the normal pH is 7.40, pCO2 is 41 mm Hg, and the serum bicarbonate level is 25 mmol/L; at an altitude of 1500 m, the expected pCO2 is reduced to ≈35 mm Hg and the bicarbonate level to 21 mmol/L; as the bicarbonate level is increased to 25 mmol/L, the pCO2 is increased to 40 mm Hg (slight acidosis); if the bicarbonate level is increased to 27 mmol/L, the expected pCO2 is increased to 44 mm Hg

Final points: serum bicarbonate levels are helpful, but the cutoff of 27 mmol/L might not apply, even at moderate altitude

Readings

Masa JF, Benítez ID, Sánchez-Quiroga MÁ, et al. Effectiveness of CPAP vs noninvasive ventilation based on disease severity in obesity hypoventilation syndrome and concomitant severe obstructive sleep apnea. Arch Bronconeumol. 2022;58(3):228-236. doi:10.1016/j.arbres.2021.05.019; Mokhlesi B, Masa JF, Brozek JL, et al. Evaluation and management of obesity hypoventilation syndrome. An Official American Thoracic Society Clinical Practice Guideline [published correction appears in Am J Respir Crit Care Med. 2019;200(10):1326. doi: 10.1164/rccm.v200erratum7]. Am J Respir Crit Care Med. 2019;200(3):e6-e24. doi:10.1164/rccm.201905-1071ST; Osman A, Gu C, Kim DE, et al. Ketogenic diet acutely improves gas exchange and sleep apnoea in obesity hypoventilation syndrome: A non-randomized crossover study. Respirology. 2023;28(8):784-793. doi:10.1111/resp.14526; Sivam S, Yee B, Wong K, et al. Obesity hypoventilation syndrome: Early detection of nocturnal-only hypercapnia in an obese population. J Clin Sleep Med. 2018;14(9):1477-1484. doi:10.5664/jcsm.7318.

Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Sarmiento was recorded at the 29th Annual Advances in Diagnosis and Treatment of Sleep Apnea and Snoring, held February 16-17, 2024, in San Francisco, CA, and presented by the University of California, San Francisco. For information on future CME activities from this presenter, please visit https://sleepapnea.ucsf.edu/. Audio Digest thanks the speakers and presenters for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0.25 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0.25 CE contact hours.

Lecture ID:

OT571904

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.