Safe use of PEEP in patients with severe head injury

Abstract

Thirty-three patients with severe head trauma were studied to determine whether the use of positive end-expiratory pressure (PEEP) would cause an increase in intracranial pressure (ICP). Changes in ICP induced by PEEP were then correlated with a panel of physiological variables to try to explain these changes. Mean ICP increased from 13.2 +/- 7.7 mm Hg (+/- standard deviation) to 14.5 +/- 7.5 mm Hg (p less than 0.005) due to 10 cm H2O PEEP, but the eight patients with elevated baseline ICP experienced no significant increase. Cardiac output and venous admixture (Qs/Qt) declined significantly, while central venous pressure, peak inspiratory pressure, functional residual capacity, and arterial pCO2 increased significantly due to PEEP. Blood pressure and cerebral perfusion pressure were unchanged. The change in ICP due to PEEP correlated significantly with a combination of cardiac output, peak inspiratory pressure, Qs/Qt, and changes in blood pressure and arterial pCO2 due to PEEP, indicating that the effect of PEEP on ICP could be largely explained by its effect on hemodynamic and respiratory variables. No patient deteriorated clinically due to PEEP. It is concluded that 10 cm H2O PEEP increases ICP slightly via its effect on other physiological variables, but that this small increase in ICP is clinically inconsequential.

Effects of Positive End-Expiratory Pressure on Intracranial Pressure and Cerebral Perfusion Pressure

“…These side effects of PEEP [4,14,26] could potentially produce critical reductions and elevations in CPP and ICP, respectively. The relationship of PEEP therapy on ICP and CPP has been of considerable interest to many investigators [3,7,9,11,30]. Thus, a considerable effort has been made for investigating repeatedly in human [1,3,5,9,11,21,30] and animal experiments [2,10,12,18], with different designs, to understand the interplay between PEEP and the physiologic dynamics relating to cardiac, pulmonary and CNS.…”

“…The relationship of PEEP therapy on ICP and CPP has been of considerable interest to many investigators [3,7,9,11,30]. Thus, a considerable effort has been made for investigating repeatedly in human [1,3,5,9,11,21,30] and animal experiments [2,10,12,18], with different designs, to understand the interplay between PEEP and the physiologic dynamics relating to cardiac, pulmonary and CNS. Sometimes, the results of the studies are contradictory [6,10] and conclusions unclear [5].…”

Respiratory mechanics in brain injury: A review

“…On the contrary, reduced lung compliance could exert a protective role by minimizing airway pressure transmission [86] . However, clinical studies investigating the influence of respiratory system mechanics on the transmission of PEEP to the intracranial compartment have reported conflicting results [78,87] . Caricato et al [51] found that PEEP application resulted in reduction of CPP only in patients with normal respiratory system compliance, but had no effect on ICP regardless of the latter.…”

Influence of Positive End-Expiratory Pressure Ventilation on Cerebral Perfusion and Cardiac Hemodynamics

“…Other physiological variables, such as cardiac output and cerebral perfusion (determined by ultrasonography), were also measured. The authors concluded that 10 cm H 2 O PEEP increases ICP slightly through an effect on other physiological variables, but found no clinical consequence [28]. Another prospective study undertaken by Caricato et al [29] involved examination of 21 patients with head injury and subarachnoid hemorrhage who were given mechanical ventilation.…”

“…The effect of bloodbrain barrier disruption is known; particularly in cases of cerebral ischemia, it results in a neuro inflammatory response that is attended by edema and has consequences for ICP and vascular auto regulation [27]. Cooper et al [28] examined 33 patients with severe head injury to determine whether changes in PEEP would cause an increase in ICP. Other physiological variables, such as cardiac output and cerebral perfusion (determined by ultrasonography), were also measured.…”