A 32 year old severely obese male non smoker with no major past medical history is brought to ED in respiratory distress. After two hours in waiting room, he becomes confused and somnolent. Initial vital signs are temperature of 37.5 C, HR of 105, resp rate of 25 and BP of 154/102. ABG shows PaO2 of 65 mmhg and PaCO2 75. A CXR shows basilar atelectasis with minimal symmetric diaphragmatic elevation and without pneumonia, pneumothorax, pleural effusion. CT of the chest without contrast shows no lung abnormalities but does indicate right ventricular enlargement. ECG shows sinus tachycardia. labs are remarkable for elevated D dimer, elevated RBC and elevated serum bicarbonate. 1. What is the likely diagnosis and why?

The main function of the respiratory system is gas exchange (O2 and CO2). Ventilation is the movement of air through the respiratory tract into (inspiration) and out of (expiration) the respiratory zone (lungs).