SURVIVAL IN PATIENTS WITH SEVERE ADULT-RESPIRATORY-DISTRESS-SYNDROME TREATED WITH HIGH-LEVEL POSITIVE END-EXPIRATORY PRESSURE

Objective: To assess the mortality rate and complications in a populat ion of surgical patients with severe adult respiratory distress syndro me (ARDS) treated with positive end-expiratory pressure (PEEP) of >15 cm H2O in an attempt to reduce intrapulmonary shunt to similar to 0.20 and reduce FIO2 to <0.50. Design: Retrospective review of patients tr eated by a standardized ventilatory support protocol at the time of th eir illness. Setting: A 24-bed surgical intensive care unit in a unive rsity medical center.Patients: All patients admitted to the surgical i ntensive care unit during a 34-month period who met the criteria for s evere ARDS (PaO2 of less than or equal to 70 torr [less than or equal to 9.3 kPa] on an FIO2 of greater than or equal to 0.50, diffuse inter stitial and/or alveolar infiltrates on chest radiograph, decreased lun g compliance, no evidence of congestive heart failure, and a likely pr edisposing etiology) were evaluated. Patients treated with PEEP of >15 cm H2O were selected for this review. Interventions: Patients were tr eated by a protocol to achieve oxygenation end points, which consisted of maintaining arterial oxyhemoglobin saturation (as determined by pu lse oximetry of greater than or equal to 0.92), while reducing FIO2 to <0.50 and decreasing intrapulmonary shunt fraction to less than or eq ual to 0.20 by adding PEEP. With the exception of patients with suspec ted intracranial hypertension related to closed-head injury, low-rate intermittent mandatory ventilation was the primary mode of ventilation . Pressure-support ventilation was added, when needed, to improve pati ent comfort, enhance spontaneous tidal volume, or improve CO2 excretio n. Measurements and Main Results: Eighty-six patients with severe ARDS were treated with a PEEP of >15 cm H2O. Nineteen of these patients di ed early of severe closed-head injury or massive uncontrollable hemorr hage and were excluded from the evaluation. The remaining 67 patients had a mean Lung Injury Score of 3.3 during their treatment with high P EEP. Twenty (30%) of 67 patients died. Eight of the deaths occurred af ter decrease of ventilatory support and with acceptable blood gases. T he other 12 patients who died had continued oxygenation deficits and r eceived increased levels of ventilatory support at the time of death. Twenty-six (39%) of 67 patients had radiographic manifestations of bar otrauma (pneumothorax, subcutaneous emphysema, etc.) related to their primary injuries or to complications related to central venous cathete r placement. Seven (17%) of 41 patients developed clinical or radiogra phic signs of barotrauma while receiving high-level PEEP. The hemodyna mic effects of increased airway pressure were managed with fluids and inotropic agents, when necessary, and did not limit the application of PEEP to reach the defined end point of treatment. Conclusions: This s ubset of patients with severe ARDS treated with high-level PEEP had a mortality rate lower than those rates previously reported by other res earchers using more conventional ventilatory support and resuscitation techniques. FIO2 may be significantly reduced and PaO2 may be maintai ned at acceptable values by decreasing intrapulmonary shunt fraction u sing high-level PEEP.