Effect of peep on esophageal catheter optimal calibration volume and esophageal pressure measurements
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KeywordsChest Compression Transpulmonary Pressure Esophageal Pressure Occlusion Test Chest Wall Compliance
The use of esophageal balloon catheter to estimate pleural pressure has gained renewed popularity in recent years. Indeed, measurement of transpulmonary pressure may allow a more pathophysiological-based approach to ventilator strategy in ARDS patients. Nevertheless it is well known that esophageal balloon catheter derived parameters can be influenced by several patient-related or technical-related factors.
To evaluate in-vivo the effect of positive end-expiratory pressure (PEEP) variations on esophageal catheter optimal calibration volume and measured esophageal pressure.
Experimental study in 8 (5 ARDS, 3 control) sedated, intubated, paralyzed and mechanically ventilated (volume-control) patients. Patients were monitored with esophageal balloon catheter (Cooper Surgical, Trumbull, CT USA).
Three PEEP groups were defined: lowPEEP (8 and 4 cmH2O respectively in ARDS and control patients), mediumPEEP (12 and 8 cmH2O) and highPEEP (16 and 12 cmH2O).
During each PEEP level, we inflated the esophageal balloon with increasing amount of air (from 0.2 to 2 ml). For each injected volume, we performed an end-inspiratory occlusion maneuver followed by an occlusion test by applying manual chest compression during an end-expiratory airway occlusion maneuver. We measured the ratio between airway pressure variation and esophageal pressure variation (ΔPaw/ΔPes ratio) during the occlusion test, end-expiratory esophageal pressure (Pes,e), end-expiratory transpulmonary pressure (Pl,e), chest wall compliance (CplCW), lung compliance (CplL), elastance-derived transpulmonary plateau pressure (ΔPl,i). The optimal calibration volume (defined as the injected volume at which ΔPaw/ΔPes ratio was closer to 1) was identified for each PEEP group (VCLPEEP for lowPEEP, VCMPEEP for mediumPEEP, VCHPEEP for highPEEP). Effect of PEEP on derived parameters was assessed by comparing at PEEP medium and high values obtained at the VCLPEEP against values obtained with the optimal VC at each PEEP.
Partitioned respiratory system mechanic parameters are show in Table.
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