In others, the total PEEP rises as a consequence of PEEP application and adverse effects can occur due to the worsening of hyperinflation. In some patients, here referred to as “complete PEEP- absorbers,” the application of PEEP reduces the auto-PEEP to maintain a constant total PEEP (i.e., the sum of PEEP and auto-PEEP as measured by the end-expiratory airway occlusion), therefore reducing the inspiratory threshold load and the work of breathing without detrimental cardiovascular or respiratory effects. ConclusionsĮxpiratory flow limitation was associated with both high and complete “PEEP-absorber” behavior, but setting a relatively high respiratory rate on the ventilator can prevent from observing complete “PEEP-absorption.” Therefore, the effect of PEEP application in patients with auto-PEEP can be accurately predicted at the bedside by measuring the respiratory rate and observing the flow-volume loop during manual compression of the abdomen.ĭeciding whether to use positive end-expiratory pressure (PEEP) in mechanically ventilated patients with auto-PEEP is a daily challenge for intensivists, since in these patients the application of PEEP can increase or not the end-expiratory lung volume and end-expiratory plateau pressure. The predictive ability of the model was excellent, with an overoptimism-corrected area under the receiver operating characteristics curve of 0.89 (95 % CI 0.80–0.97). Thirty-three percent of the patients were “complete PEEP-absorbers.” Multiple logistic regression was used to predict the behavior of “complete PEEP-absorber.” The best model included a respiratory rate lower than 20 breaths/min and the presence of flow limitation. The mean total PEEP was 7 ± 2 cmH 2O at ZEEP and 9 ± 2 cmH 2O after the application of PEEP ( p < 0.001). Resultsįorty-seven percent of the patients suffered from chronic pulmonary disease and 52 % from acute pulmonary disease 61 % showed flow limitation at ZEEP, assessed by manual compression of the abdomen. All measurements were repeated three times, and the average value was used for analysis. Total PEEP (i.e., end-expiratory plateau pressure) was measured both at ZEEP and after applied PEEP equal to 80 % of auto-PEEP measured at ZEEP. One hundred patients with auto-PEEP of at least 5 cmH 2O at zero end-expiratory pressure (ZEEP) during controlled mechanical ventilation were enrolled. This study aimed to empirically assess the extent to which flow limitation alone explains a “complete PEEP-absorber” behavior (i.e., absence of further hyperinflation with PEEP), and to identify other factors associated with it. From a pathophysiological perspective, all subjects with flow limitation are expected to be “complete PEEP-absorbers,” whereas PEEP should increase total PEEP in all other patients. We refer to these patients as “complete PEEP-absorbers.” Conversely, adverse effects of PEEP application could occur in patients with auto-PEEP when the total PEEP rises as a consequence. In some patients with auto-positive end-expiratory pressure (auto-PEEP), application of PEEP lower than auto-PEEP maintains a constant total PEEP, therefore reducing the inspiratory threshold load without detrimental cardiovascular or respiratory effects.
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