All of the following criteria are required for diagnosis of obesity hypoventilation syndrome except-
**Core Concept**
Obesity hypoventilation syndrome (OHS) is a condition characterized by the combination of obesity and chronic hypoventilation, leading to hypercapnia and hypoxemia. The pathophysiology of OHS involves impaired lung function, reduced chest wall compliance, and increased airway resistance due to excess body fat.
**Why the Correct Answer is Right**
For a diagnosis of OHS, the following criteria must be met: (1) a body mass index (BMI) of 30 kg/m² or higher, (2) daytime hypercapnia (PaCO2 ≥ 45 mmHg) despite adequate respiratory drive, and (3) the absence of other causes of hypoventilation (e.g., pulmonary disease, neurological disorders, or sleep apnea). The presence of cor pulmonale is also a diagnostic criterion for OHS.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a required criterion for diagnosing OHS, as the presence of daytime hypercapnia is the key indicator of impaired respiratory function.
**Option B:** While a BMI of 30 kg/m² or higher is a necessary condition for OHS, it is not sufficient on its own to diagnose the syndrome.
**Option C:** Cor pulmonale is actually a diagnostic criterion for OHS, not an exclusion criterion.
**Clinical Pearl / High-Yield Fact**
It's essential to note that OHS often coexists with other sleep disorders, such as obstructive sleep apnea (OSA), and that the diagnosis of OHS requires a comprehensive evaluation of respiratory function and sleep quality.
**Correct Answer: C. Cor pulmonale is a diagnostic criterion for OHS, not an exclusion criterion.**