All of the following criteria are required for diagnosis of obesity hypoventilation syndrome except-

Ans. is 'a' i.e., Hypertension o Obesity hyoventilation syndrome (OHS) is defined as the triad of obesity, daytime hypoventilation, and sleep- disordered breathing in the absence of an alternative neuromuscular, mechanical or metabolic explanation for hypoventilation.Obesity hypoventilation syndrome||||ObesityDay time hypoventilationSleep disordered breathingo OHS is defined as daytime hypercapnia and hypoxemia (Paco2 > 45 mm Hg and Pao2 < 70 mm Hg at sea level) in an obese patient (body mass index > 30 kg/m2) with sleep-disordered breathing in the absence of any other cause of hypoventilation. It is important to recognize that OHS is a diagnosis of exclusion and should be distinguished from other conditions that are commonly associated with hypercapnia.Definition of Obesity Hypoventilation SyndromeRequired ConditionsDescriptionObesityo Body mass index > 30 kg/m2Chronic hypoventilationo Awake daytime hypercapnia(PaCo2 > 45 mm Hg and Pao2 < 70 mm Hg)Sleep-disordered breathingo Obstructive sleep apnea (apneahypopnea index > 5 events/h, with or without sleep hypoventilation) present in 90% of caseso Non-obstructive sleep hypoventilation (apnea-hypopnea index 5 events/h) in 10% of casesExclusion of other causes of hypercapniao Severe obstructive airways diseaseo Severe interstitial lung diseaseo Severe chest-wall disorders (eg, kyphoscoliosis)o Severe hypothyroidismo Neuromuscular diseaseo Congenital central hypoventilation syndromeMechanisms bv which obesity can lead to chronic daytime hypercapnia Obesity | | |Leptin resistance Increased mechanical load and weak respiratory muscles Obstructive sleep apnea upper-airway resistance||||| |||| | Acute hypercapnia during sleep | -Decreased Co3 response-------Blunted ventilatory response-Increased serum HCO3- | -Decreased HC03- excretion rate Chronic hypercapnia