Figure 1
From: Clinical application of esophageal manometry: how I do it
This figure represents positive end-expiratory pressure (PEEP) titration in a mildly obese woman with moderate-severe acute respiratory distress syndrome (ARDS) secondary to ascites and TRALI, with increased chest wall stiffness and mildly elevated basal pleural pressures. Patient was on Vt 250 cc (close to 5 cc/kg IBW), RR 34 and FiO2 0.6. This example illustrates the use in PEEP titration and monitoring of cyclic and total lung stress levels and how esophageal manometry can be used to titrate PEEP not only to HIGH levels, but also be used to titrate downwards to an optimal mid-range. PEEP (airway pressure—Pao) was adjusted to match the measured esophageal pressure (Pes) to calculate the transpulmonary pressure (PL = Pao – Pes) and target a PL equal to zero. a Empiric PEEP of 18cmH2O (equivalent to using empiric high PEEP ARDSnet tables) was utilized initially on this patient. On these initial settings, the total PEEP was 20cmH2O, plateau pressure was 40cmH2O, respiratory system driving pressure (∆PRS) was 20cmH2O, and respiratory system compliance was 12.5 ml/cmH2O. The end-expiratory transpulmonary pressure (PL) was + 5cmH2O, and end-inspiratory PL 20cmH2O with a transpulmonary driving pressure (∆PL) of 15cmH2O with a lung compliance of 15 ml/cmH2O. These numbers suggested PEEP application was too high and could be resulting in overdistension as measured by the cyclic and total lung stress. b Lowering PEEP to 12cmH2O resulted in finding optimized mechanics at a PEEP of 12cmH2O. This resulted in a total PEEP of 14.5cmH2O, plateau pressure of 29.5cmH2O, ∆PRS of 15cmH2O, respiratory system compliance of 18 ml/cmH2O, end-expiratory PL of + 0.5cmH2O, end-inspiratory PL of 11cmH2O, ∆PL of 10.5 ml/cmH2O and lung compliance of 24 ml/cmH2O. c Dropping PEEP further to 6cmH2O resulted in apparent derecruitment with worsened mechanics. Total PEEP was 8.5cmH2O, plateau pressure 26.5cmH2O, ∆PRS 18cmH2O, respiratory system compliance 13.9 ml/cmH2O, end-expiratory PL was − 5.8cmH2O, end-inspiratory PL was 9cmH2O, ∆PL 14.8cmH2O, lung compliance 16.8 ml/cmH2O