医院获得性肺炎(HAP)是指患者入院时不存在、也不处于感染潜伏期,而在入院48小时后发生的由细菌、真菌、支原体等病原体引起的各种类型的肺实质炎症。该病病情复杂,预后不佳,多见于年老体弱的患者,在重症监护(ICU)病房占有较大的比例。一方面,ICU的HAP患者常存在机械通气、留置胃管或意识障碍等误吸因素; Hospital Acquired Pneumonia (HAP) refers to various types of pulmonary parenchymal inflammation caused by pathogens such as bacteria, fungi, and mycoplasma occurring 48 hours after admission, which are not present at admission and are not yet infected. The disease is complicated and has a poor prognosis, which is more common in older and frail patients and occupies a larger proportion in intensive care unit (ICU) wards. On the one hand, ICU patients with HAP often have mechanical ventilation, indwelling gastric tube or disturbance of consciousness and other factors;