Gastric Intramucosal pH is Stable During Titration of Positive End-Expiratory Pressure to Improve Oxygenation In Acute Respiratory Distress Syndrome

Ibrahim Ozkan Akinci, Nahit Çakar, Gökhan Mehmet Mutlu, Simru Tugrul, Perihan Ergin Ozcan, Musa Gitmez, Figen Esen Lutfi Telci

Disclosures

Crit Care. 2003;7(3) 

In This Article

Results

A total of 17 patients were enrolled in the present study (11 male and 6 female). The characteristics of the individual patients are shown in Table 1 . The mean age of the study population was 47.2 ± 19.8, the mean Acute Physiology and Chronic Health Evaluation II score was 19.7 ± 3.5, and the mean Sequential Organ Failure Assessment score was 6.3 ± 1.8. By titrating PEEP, we were able to achieve a mean PEEPopt of 10.4 ± 3.9 cmH2O and a PEEPmax of 13.3 ± 2.9 cmH2O (P = 0.0001). The highest PEEP value applied was 17 cmH2O. Static compliance improved slightly at PEEPopt, but this did not achieve statistical significance (P = 0.84; Table 2 ). Changes in peak airway and mean airway pressures at PEEPbaseline, PEEPopt and PEEPmax were statistically significant (P < 0.001; Table 2 ). Reasons for stopping the titration of PEEP were reduction in PaO2 (from 20% to 40%; n = 6), reduction in MAP (from 25% to 60%; n = 4), adequate oxygenation (PaO2350-450 mmHg; n = 4) and excessive peak upper ariway pressure (n = 3).

Although PEEP significantly improved shunt fraction, and consequently PaO2, its greater effect on cardiac output led to a reduction in DO2 both at PEEPopt and PEEPmax. However, none of the changes in haemodynamic parameters, including those in central venous pressure, pulmonary artery occlusion pressure, cardiac output, cardiac index and DO2, achieved statistical significance ( Table 2 and Fig. 1). PaO2 values remained stable at each level of PEEP. The mean pHi was 7.31 ± 0.13 at baseline and 7.32 ± 0.12 at PEEPopt; it decreased to 7.29 ± 0.12 at PEEPmax, but this reduction was not statistically significant (P = 0.84). Similar to pHi, alterations in the gap between partial tissue and arterial carbon dioxide tension (P(t-a)CO2) were not significant (P = 0.353).

Cardiac output changes at baseline positive end-expiratory pressure (PEEPbaseline; 5 cmH 2 O), PEEPopt and PEEPmax.

Although the increase in PEEP had no impact on the group as a whole, changes in pHi and P(t-a)CO2 during PEEP titration differed between individual patients ( Table 3 ). The pHi decreased in eight patients (47%), it increased in five (29.4%) and it was unchanged in four (23.5%) at PEEPopt as compared with PEEPbaseline. The pHi at PEEPmax was lower in 12 (70.6%) and higher in five (29.4%) patients as compared with baseline values. The P(t-a)CO2 values increased in nine (52.3%) patients at PEEPopt and in 10 (58.3%) patients at PEEPmax as compared with PEEPbaseline ( Table 3 ). However, there were no statistically significant differences in P(t-a)CO2 values between PEEPbaseline, PEEPopt and PEEPmax (P = 0.353; Table 2 ). Interestingly, DO2 in those patients who exhibited a rise in pHi did not increase. Rather, DO2 in these patients also decreased (although this was not statistically significant) at PEEPopt and PEEPmax, to a degree similar to that in patients who exhibited a drop in pHi.

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