End-expiratory lung volume measurement by the nitrogen washin-washout technique (EELV WI-WO) is available at the bedside from an ICU ventilator, and may help titrating PEEP during mechanical ventilation of ARDS patients. The reliability of the WI-WO technique is critically dependent on ventilatory settings, but sufficient to accurately detect EELV change greater than 200 mL.Īcute respiratory distress syndrome (ARDS) is characterized by a major decrease in lung aerated volume. Diagnostic accuracy was good for detection of absolute EELV changes above 200 mL (AUC = 0.79). Concordance rate of EELV changes between consecutive measurements was fair (79%). Bias between methods was greater at high PEEP, and further increased when high PEEP was combined with low V T. Limits of agreement for bias were ☓98 mL. ResultsĮELV WI-WO underestimated EELV CT with a non-constant linear bias, as it decreased with increasing EELV. EELV WI-WO and EELV CT were determined after ARDS onset, at variable PEEP and V T. kg -1) were finally applied at optimal PEEP.Optimal PEEP was selected during a decremental PEEP trial, based on best compliance, best EELV WI-WO, or a PEEP-FiO 2 table. MethodsĪRDS was induced in 14 piglets by saline lavage.
The aims of this study were (1) to evaluate the reliability of EELV WI-WO measurements at different PEEP and V T during experimental ARDS and (2) to evaluate trending ability of EELV WI-WO to detect EELV changes over time. Validation of this technique has been previously performed using computed tomography (EELV CT), but at mild PEEP levels, and relatively low fraction of inspired oxygen (FiO 2), which may have insufficiently challenged the validity of this technique. End-expiratory lung volume measurement by the nitrogen washin-washout technique (EELV WI-WO) may help titrating positive end-expiratory pressure (PEEP) during acute respiratory distress syndrome (ARDS).
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