Obesity Hypoventilation Syndrome (OHS)
Definition
OHS: Presence of awake alveolar hypoventilation (PaCO2 > 45 mmHg) in an obese individual (BMI > 30 kg/m²) without other causes of hypoventilation.
Risk Factors
- Obesity: Especially severe obesity (BMI > 50 kg/m²).
- Leptin Resistance: Reduced respiratory drive due to leptin resistance.
Clinical Presentation
- Symptoms: Daytime sleepiness, dyspnea, morning headaches, and sleep-disordered breathing.
- Physical Exam: Enlarged neck circumference, crowded airway, loud S2 heart sound, lower extremity edema.
Diagnosis
- Criteria: BMI > 30 kg/m², PaCO2 > 45 mmHg, sleep-disordered breathing, and exclusion of other causes of hypercapnia.
- Lab Findings: Elevated PaCO2 and HCO3 on arterial blood gas (ABG), hypoxemia.
Complications
- Cardiovascular Morbidity: Increased risk of cardiovascular disease and hospital admissions.
- Pulmonary Hypertension: Common comorbidity.
Treatment
- Noninvasive Positive Airway Pressure (PAP): CPAP or BiPAP.
- Weight Loss: Essential for long-term management.
- Tracheostomy: In severe cases.
For further information try this obesity hypoventilation syndrome book.
Mnemonic for OHS
OHS CAN HELP
Obesity
Hypercapnia (PaCO2 > 45 mmHg)
Sleep-disordered breathing
CPAP/BiPAP
ABG (Elevated PaCO2 and HCO3)
Neck circumference (enlarged)
Headaches (morning)
Edema (lower extremity)
Leptin resistance
Pulmonary hypertension
This post covers the points you need to know for your board exams as well as for teaching residents on the daily rounds. Medical professionals can't use the information here to treat their patients nor people can use the information her to treat themselves. If you are having any medical issues, contact your local emergency services. Please refer to your doctor for medical advice.