Ans. is 'd' i.e., All of the above * Positive airway pressure therapy means proving positive pressure during breathing. It may be :-1) Positive end-expiratory pressure (PEEP)# PEEP is the positive pressure is applied at the end of expiration during mechanical ventilation. So, PEEP has two features : -i) Positive pressure is applied during expiration (at the end).ii) Used for mechanical ventilation2) Continuous positive Airway pressure (CPAP)# CPAP is application of positive-pressure : -i) During both inspiration and expiration.ii) In spontaneous breathingPulmonary effects of PEEP and CPAP* Positive pressure in PEEP 8c CPAP results in : -i) Re-expansion (recruitment) and stabilization of partially collapsed lung, which causes : -a) Increased FRC, tidal volume & lung compliance.b) Correction of ventilation!perfusion abnormalities - Improved oxygenation.ii) Redistribution ofextravascular lung water from interstitial space between alveoli and endothelial cells towards peri-bronchial and perihilar areas - As fluid moves away from the space between vessels & alveolar space, oxygen can diffuse more easily from alveoli into the blood - Improved arterial oxygenation.Adverse effects of PEEP/CPAP1. Pulmonary* Controlled PEEP or CPAP improve lung compliance and correct ventilation/perfusion abnormalities. However, excessive PEEP or CPAP can overdistend alveoli & bronchi which results in : -i) Increased dead space ventilationii) Reduced lung complianceiii) Increased pulmonary vascular resistance & Right ventricular afterload.iv) Barotrauma (Pneumothorax, pneumopericardium, pneumoperitonium, Subcutaneous emphysema).2. Extrapulmonary* These adverse effects are primary circulatory and are related to transmission of elevated airway pressure to the chest :-i) Decreased cardiac output (due to increased intrathoracic pressure venous return is decreased).ii) Decreased hepatic & renal blood flow (due to decreased cardiac output 8c elevated CVP)iii) Increased ADH & angiotensiniv) Decreased urinary output, GFR and free water clearance (Decrease Renal function).v) Increased ICT (due to increased CVP).