Abstract:  Objective    To evaluate the incidence of expiratory flow limitation in patients with mechanical ventilation in Intensive Care Unit,  and to identify the main clinical characteristics,  risk factors and prognostic implications associated with expiratory flow limitation. Methods    A total of 202 patients requiring mechanical ventilation in the department of intensive medicine were selected and divided into two groups by positive endexpiratory pressure (PEEP) test: the expiratory flow limitation group and the nonexpiratory flow limitation group. The respiratory mechanics indexes were measured within 12 hours after mechanical ventilation and daily for 3 days. All patients were assessed with SAPS score and Sequential Organ Failure Assessment(SOFA) score. The modified British Medical Council dyspnea score scale (mMRC) was used to assess the severity of dyspnea. Results    22.77%  of the patients were found to have expiratory flow limitation,  including 39 cases of septic shock,  25 cases of ARDS,  27 cases of hemorrhagic shock,  32 cases of acute exacerbation of chronic obstructive pulmonary disease,  45 cases of acute respiratory failure,  12 cases of heart failure and 22 cases of cerebrovascular disease with pneumonia. Patients with expiratory flow limitation had a higher body mass index (BMI). Limited expiratory velocity was associated with history of heart disease and history of chronic lung disease (all P<0.05). In terms of respiratory mechanics data,  patients with expiratory flow limitation had poor scores of dyspnea,  high maximum airway resistance and increased elastic resistance,  higher positive endexpiratory resistance pressure and endogenous endexpiratory pressure,  higher peak pressure and lower oxygenation index (all P<0.05). The SOFA scores and SAPSⅡ were higher in the expiratory flow limitation group,  and the mechanical ventilation was longer,  with higher mortality (all P<0.05). Conclusion    High BMI and a history of lung disease or heart disease are high risk factors for expiratory flow limitation in patients with mechanical ventilation in Intensive Care Unit. The respiratory parameters of patients with expiratory flow limitation were worse. Patients with expiratory flow limitation have longer mechanical ventilation time,  longer hospitalization time,  higher mortality and poor prognosis.

Key words: respiration, , artificial；expiratory flow limitation；risk factors