Could a 45-year-old obese male, 2 weeks post percutaneous transluminal coronary angioplasty (PTCA) of the left anterior descending artery, presenting with severe hypertension, tachycardia, exertional shortness of breath that improves with non‑invasive ventilation, normal arterial blood gases at rest, preserved left‑ventricular ejection fraction, no peripheral edema, and normal renal function, be diagnosed with obesity‑hypoventilation syndrome?

This patient does NOT meet diagnostic criteria for obesity hypoventilation syndrome

The diagnosis of OHS cannot be made in this patient because he has normal arterial blood gases without hypercapnia. OHS requires documented awake daytime hypercapnia (PaCO₂ >45 mmHg at sea level) along with obesity and sleep-disordered breathing 1.

Why OHS is Unlikely Here

Missing Essential Diagnostic Criterion

• OHS definition requires three components 1:
  • Obesity (BMI >30 kg/m²) ✓ Present
  • Sleep-disordered breathing ✓ Possibly present (responds to NIV)
  • Awake daytime hypercapnia (PaCO₂ >45 mmHg) ✗ ABSENT - Your ABG shows normal PaCO₂

The normal ABG effectively excludes OHS as the primary diagnosis at this time.

Additional Screening Considerations

If you still suspect OHS despite normal resting ABG, check a serum bicarbonate level 1:

• Bicarbonate <27 mmol/L essentially excludes OHS in patients with low-to-moderate pretest probability
• Bicarbonate ≥27 mmol/L warrants repeat ABG measurement, as metabolic compensation may mask early hypercapnia

More Likely Alternative Diagnoses

Given the clinical presentation, consider these more probable explanations:

1. Acute Hypertensive Heart Failure (Flash Pulmonary Edema)

• BP 230/110 with acute SOB is classic
• Improved with NIV (provides positive pressure reducing preload/afterload)
• EF 54% does NOT exclude diastolic heart failure/HFpEF
• Post-PTCA patients remain at cardiovascular risk
• Check BNP/NT-proBNP immediately

2. Obstructive Sleep Apnea (OSA) Without OHS

• Can cause exertional dyspnea and hypertension
• Responds to positive airway pressure
• Does NOT require hypercapnia for diagnosis
• Refer for polysomnography

3. Diastolic Dysfunction/HFpEF

• Extremely common in obese, hypertensive patients
• Preserved EF by definition
• Exertional dyspnea is hallmark symptom
• Obtain formal diastolic function assessment on echo

Critical Next Steps

Immediate workup should include:

• BNP/NT-proBNP - to assess for heart failure
• Serum bicarbonate - if still considering OHS
• Formal sleep study (polysomnography) - to diagnose OSA
• Repeat echocardiogram with diastolic function assessment - specifically evaluate E/e' ratio, left atrial size, pulmonary pressures
• Aggressive blood pressure control - this severe hypertension (230/110) is life-threatening and likely contributing significantly to symptoms

Important Caveats

Do not dismiss cardiovascular causes in favor of OHS when:

• The patient is 2 weeks post-coronary intervention
• Presenting with hypertensive emergency (BP 230/110)
• Has tachycardia (HR 106)
• Normal ABG excludes the hypercapnia required for OHS diagnosis

OHS is associated with serious cardiovascular complications including pulmonary hypertension, heart failure, and increased mortality 1, 2, 3, 4, but these are consequences of chronic untreated OHS, not acute presentations in patients with normal blood gases.

The improvement with NIV does not confirm OHS—it simply indicates positive pressure support helped, which occurs in multiple conditions (acute heart failure, OSA, obesity-related restrictive physiology).