Gastric intramucosal pH is stable during titration of positive end-expiratory pressure to improve oxygenation in acute respiratory distress syndrome

Abstract

Correspondence: I Ozkan Akinci, iozkana@yahoo.com R17 ALI = acute lung injury; ARDS = acute respiratory distress syndrome; DO 2 = oxygen delivery; MAP = mean arterial pressure; Pao 2 = partial arterial oxygen tension; P (t-a) CO 2 = gap between partial tissue and arterial carbon dioxide tension; PEEP = positive end-expiratory pressure; pH i = gastric mucosal pH. AbstractBackground Optimal positive end-expiratory pressure (PEEP) is an important component of adequate mechanical ventilation in acute lung injury and acute respiratory distress syndrome (ARDS). In the present study we tested the effect on gastric intramucosal pH of incremental increases in PEEP level (i.e. PEEP titration) to improve oxygenation in ARDS. Seventeen consecutive patients with ARDS, as defined by consensus criteria, were included in this clinical, prospective study. All patients were haemodynamically stable and were not receiving vasopressors. From an initial level of 5 cmH 2 O, PEEP was titrated at 2 cmH 2 O increments until the partial arterial oxygen tension was 300 mmHg or greater, peak airway pressure was 45 cmH 2 O or greater, or mean arterial blood pressure decreased by 20% or more of the baseline value. Optimal PEEP was defined as the level of PEEP that achieved the best oxygenation. The maximum PEEP was the highest PEEP level reached during titration in each patient. Results Gastric mucosal pH was measured using gastric tonometry at all levels of PEEP. The thermodilution technique was used for measurement of cardiac index. Gastric mucosal pH was similar at baseline and at optimal PEEP levels, but it was slightly reduced at maximum PEEP. Cardiac index and oxygen delivery remained stable at all PEEP levels. Conclusion Incremental titration of PEEP based on improvement in oxygenation does not decrease gastric intramucosal perfusion when cardiac output is preserved in patients with ARDS.

Effects of positive end-expiratory pressure on gastric mucosal perfusion in acute respiratory distress syndrome

“…In contrast, we found no decrease in cardiac output in our patients tested with increasing PEEP levels when fluid administration was optimized according to respiratory variation in systolic arterial pressure. A similar result was reported by Kiefer and colleagues and by Akinci and colleagues [11,16]. Possible explanations for these contradictory results are a higher rate of fluid administration and the use of lower tidal volumes in the latter studies.…”

“…This is consistent with the findings of two other studies on the effects of PEEP on splanchnic perfusion in patients with ARDS. Nevertheless, in contrast with our study, neither of those studies included patients in septic shock or under adrenergic support [11,16]. …”

“…This is consistent with the results reported by Kiefer and Akinci in similar studies. In all these studies cardiac output remained unchanged [11,16]. In contrast, Trager reported, in a series of septic shock patients with acute respiratory failure, that an increase in PEEP from 5 to 15 cmH 2 O induced a decrease in cardiac output associated to a decrease in hepatic vein O 2 saturation and in hepatic glucose production [20].…”

Changes of splanchnic perfusion after applying positive end expiratory pressure in patients with acute respiratory distress syndrome

“…and by Akinci et al . [ 11 16 ] Possible explanations for these contradictory results are a higher rate of fluid administration and the use of lower tidal volumes in the latter studies. Although we did not determine the upper inflection point of the pressure–volume curve, we think that by keeping tidal volume at 6 ml kg −1 any overdistension of the lungs was minimized.…”

“…However, in contrast to our study, neither of those studies included patients in septic shock or on adrenergic support. [ 11 16 ]…”