inclusion criteria: - age > 18 with one or more of the following: dyspnea respiratory rate >= 30 breaths/min oxygen saturation <=93% pao2/fio2 <300 bilateral airspace opacities on chest radiograph at 24 to 48 hours

inclusion criteria: - age > 18 with one or more of the following: dyspnea respiratory rate >= 30 breaths/min oxygen saturation <=93% pao2/fio2 <300 bilateral airspace opacities on chest radiograph at 24 to 48 hours