Obstructive sleep apnea (OSA) can be described as a condition characterized by repetitive obstruction of the upper airway resulting in oxygen desaturation and awakening from sleep, loud snoring, and increased daytime sleepiness . Many studies have shown that a link exists between OSA and cardiovascular disease, chronic heart failure ischemia, hypertension, obesity, and impaired glucose tolerance . A number of factors are likely to play role in development of clinical OSA syndrome (OSAS) ranging from upper airway anatomy to central respiratory control mechanisms. The pathophysiology of OSA is unclear and complex. Several previous studies have explored pulmonary function in the OSAS patients Interestingly, OSAS has been found to be highly correlated with lower airway obstruction, although it is originally defined as an upper airway disease

American Sleep Apnea Association considers exercise as a non-pharmacological treatment modality of sleep disorders . Theoretical reviews and hypotheses on the effects of exercise in OSA have suggested thermoregulatory, metabolic, and biochemical mechanisms although clinical trials on the topic are inadequate .

Cardiopulmonary exercise testing (CPET) is used as a stress test to evaluate cardiac, pulmonary, and muscle function. It has also been used to differentiate whether the etiology of impairment of the ca. rdiopulmonary exercise test is cardiac, pulmonary or muscle dysfunction In otherwise healthy subjects, exercise limitation is due to heart disease. Patients with OSAS are frequently overweight and may exhibit lung function abnormalities related to their weight. These include a decrease in the functional residual capacity (FRC) due mainly to a decrease in the expiratory reserve volume (ERV) and a decrease in compliance of the respiratory system. These functional abnormalities cause an increase in the energy cost of breathing. In addition, increased body mass is associated with greater metabolic energy requirements during muscular exercise, resulting in further ventilatory stress. There are reports demonstrating that there are discriminating measurements during exercise in obesity, including a high O2 cost to perform external work, and upward displacement of the VO2 -WR relationship OSAS patients have daytime hypersomnolence, decreased daily activity and tissue hypoxemia which may further impair muscle function and decrease exercise fitness. Recently, Peppard and Young (2004) found that, independent of body habitus, lack of exercise was associated with increased severity of sleep-disordered breathing measurements during exercise in obesity, including a high O2 cost to perform external work, and upward displacement of the VO2 -WR relationship. OSAS patients have daytime hypersomnolence, decreased daily activity and tissue hypoxemia which may further impair muscle function and decrease exercise fitness. Recently, Peppard and Young (2004) found that, independent of body habitus, lack of exercise was associated with increased severity of sleep-disordered breathing

Inclusion Criteria:

• Stable OSA patients

Exclusion Criteria:

• Cardiovascular diseases .
• Orthopedic or neurological conditions affecting the ability of exercise.
• Patients with previous lung resection or malignancies.
• Patients with liver cell failure, renal failure.
• Muscloskeletal disease.
• Other chronic chest disease eg, ILD.

The study will be conducted as prospective study including 50 patients either admitted at our chest department or presented at our out patient clinic and diagnosed as Obstructive sleep apnea according to clinical picture and sleep study.