Abstract: The objective was to compare the collectable relevant physiological data of survivors and non-survivors of severe acute respiratory syndrome(SARS)on noninvasive positive pressure ventilation(NIPPV),and to evaluate the timing of NIPPV for SARS.Methods:Twenty-five SARS patients with respiratory dysfunction on NIPPV were divided into two groups:survivor group(n=13)and non-survivor group(n=12).The PAPCHEⅡscore,respiratory rate(RR),saturation of oxygen(SpO₂ )and modificative repiratory index(MRI)were compared between the survivors and non-survivors before NIPPV and after NIPPV for three to twenty four hours,respectively.Results:NIPPV administered with full-face masks avoided the need for endotracheal intubation,with rapidly improved vital signs and gas exchange and sense of dyspnea.Although NIPPV could be one of the effective treatments for improving oxygenation in both groups during the initial 3 to 24h of ventilatory support,the patients in non-survivor group had higher PAPCHEⅡscore,respiratory rates and lower SpO₂ ,MRI than those of the patients in survivor group(P<0.05)at the same intervals.The average time span from beginning of SARSto NIPPV in the non-survivor group was much longer than that in survivor group.Four patients in non-survivor group and none in survivor group were intubated at last.The non-survivors underlying diseases were easily accompanied with serious nosocomial pneumonia and multiple organ dysfunction syndrome(MODS).conclusions:Because severe SARS might rapidly deteriorate,appropriate use of NIPPV should be recommended,and NIPPV or IPPV should be given without hesitation when refractory hypoxemia is found.Noninvasive ventilation should be used as a preventive tool against endotracheal intubation rather than as an alternative treatment for acute respiratory failure related to SARS.Therefore,efforts should be made to avoid missing the timing for intubation.Because gas exchange disturbances in advanced SRAS may not be amenable to NIPPV,available indications for NIPPV should not be restricted.Several factors are vital to the success of NIPPV therapy,including training and experience of the staff,appropriate patient selection,properly timed intervention,patient coaching and encouragement and careful monitoring.Because most relevant studies have been retrospective and uncontrolled,many issues remain unresolved.The safety and efficacy of NIPPV,the most appropriate selection of patients and timing of intervention for SARS need to be further studied.

Key words: SARS, acute respiratory failure, noninvasive positive pressure ventilation