In patients with a stiff chest wall, the degree of http://www.selleckchem.com/products/INCB18424.html airway pressure transmitted to the pleural space would be larger than in patients with a normal chest wall; thus, the decrease in the pressure gradient for venous return observed during application of RM might explain the reduction in cardiac output [36,37]. Patients with stiff chest walls are usually ventilated for more than seven days [28]; however, that was not the case in our study.Our data indicate that the between-group difference in PaO2 decreased 30 minutes after RM. It must be emphasized that, for methodological reasons, the PEEP level was set at 5 cmH2O throughout the study. This PEEP level was probably insufficient to avoid alveolar de-recruitment and therefore decreased the RM effect [23].

The potential risk of RM-induced bacterial translocation has been discussed previously [24,38]. Several investigators have studied such translocation through the lungs [39-42] of animal models. Verbrugge and colleagues demonstrated that mechanical ventilation with a peak inspiratory pressure of 30 cmH2O, without PEEP, induced growth of Klebsiella pneumoniae bacteremia after three hours [39]. In that study blood cultures were only obtained after three hours of mechanical ventilation. Therefore, the onset of bacterial dissemination in their experimental model could not be determined. Addition of PEEP to mechanical ventilation reduces bacterial translocation. Cakar and colleagues also showed that high inflation pressures (45 cmH2O positive inspiratory pressure (PIP)) without PEEP caused dissemination of intratracheally inoculated bacteria into the systemic circulation in rats [41].

However, in the cited study, repetitive RMs (45 cmH2O CPAP for 30 Drug_discovery seconds every 15 minutes for 2 hours) did not cause translocation of bacteria. Nahum and colleagues showed that over-distention of the lungs resulted in bacterial translocation and increased lung injury in dogs [40]. In the cited study, the highest transpulmonary pressure in the low-PEEP group (PIP of 35 cmH2O and PEEP of 3 cmH2O) was associated with the earliest positive blood culture, at 30 minutes. Furthermore, the number of animals that developed positive blood cultures in this group was more than in other groups (ventilated with 13 cmH2O PIP and 3 cmH2O PEEP, or 30 cmH2O PIP and 10 cmH2O PEEP). In the same study, PEEP had a protective effect on bacteremia, despite lung over-distention. Unfortunately, no clinical data on this topic have been published to date. In our study, positive blood culture following intubation occurred in more than 30% of patients, showing the same microorganisms as found in endotracheal aspirates. There was no difference between groups, suggesting a possible causal role for mechanical ventilation in this phenomenon.