ARDS: dramatic rises in arterial PO2 with the 'open lung' approach
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KeywordsPeak Pressure Medical Intensive Care Unit Inspiratory Peak Pressure Open Lung Lung Injury Score
In a pilot study the 'open lung' concept was applied 22 times in 13 patients of a university medical intensive care unit with ARDS (lung injury score 3.7 ± 0.7) due to sepsis of various origin (APACHE II score 27.4 ± 6.3). Starting with the actual respirator adjustment, peak inspiratory pressure was increased by 10 cmH2O every 3 min up to a mean pressure of 61 ± 9 cmH2O, depending on the hemodynamic state and blood gas results of the patient. PEEP was increased to 15 to 25 cmH2O. After achieving maximal elevation of arterial PaO2, the peak pressure was then lowered to 30, maximal 40, cmH2O and PEEP adjusted just above the alveolar occlusion pressure which guaranteed a tidal volume of about 6 ml/kg body weight. Under this regimen, FiO2 could be significantly lowered from 0.9 to 0.55 with marked rise in oxygenation index from 100 ± 36 to 177 ± 63 mmHg in responders (15 maneuvers in 11 patients). Plain chest X-ray and CT scan showed marked reduction of signs of pulmonary infiltration in a very short time.
The 'open lung' approach, though short-lived, might provoke pneumothorax and mediastinal emphysema. However, it enables rapid recruitment of previously atelectatic alveoli, thus resulting in better oxygenation on the one hand, and help avoid oxygen toxicity and protracted volu- and barotrauma on the other hand which are the usual sequel of prolonged ventilation using conventional mode in ARDS. Depending on our experience, the advantages of the concept are far more obvious than its possible risks. Continuous blood gas monitoring systems may help shorten the period of high inspiratory peak pressure. Multicentre studies are required to validate long-term results and possible complications.