HOSPITAL ACQUIRED PNEUMONIA Definition: "HAP refers to a new episode of pneumonia occurring at least 2 days after the administration to hospital. It is the most common Hospital Acquired Infection (HAI) and leading cause of HAI-associated death". Predisposing factors: Aspiration of nasopharyngeal secretion Bacteria introduced into the lower GIT. Bacteriaemia Old age Mode of Spread: Droplet infection Infecting agent: Bacteria: S.pneumonia , S.aureus , H.influenza Virus: Adenovirus, Corona virus, Herpes Simplex Clinical Features: Purulent sputum New radiological infiltrates Temperature > 38 degree Celsius Leukocytosis Investigations: Chest Pain: to confirm the diagnosis and exclude complication. Pulse Oximetry : to monitor response to oxygen therapy, if SaO2 < 93% features of sever pneumonia, identify ventilatory failure or acidosis. Cell count: ESR, Neutrophil leukocytosis Microbiological studies: for severe CAP and those that do not respond to initial therapy (Gr