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The aim of the study was to investigate Propofol's effect on breathing stability in brain damage patients, as quantified by the Loop Gain (LG) of the respiratory system (breathing stability increases with decreasing LG). In 11 stable brain damage patients full polysomnography was performed before, during and after propofol sedation, titrated to achieve stage 2 or slow wave sleep. During each period, patients were ventilated with proportional assist ventilation and the % assist was increased in steps, until either periodic breathing (PB) occurred or the highest assist (95%) was achieved. The tidal volume amplification factor (VT(AF)) at the highest assist level reached just before PB occurred was used to calculate LG (LG=1/VT(AF)). In all but one patient, PB was observed. With propofol, the assist level at which PB occurred (73 + or - 19%) was significantly higher, than that before (43 + or - 35%) and after propofol sedation (49 + or - 29%). As a result, with propofol LG (0.49 + or - 0.2) was significantly lower than that before (0.74 + or - 0.2) and after propofol sedation (0.69 + or - 0.2) (p<0.05). We conclude that Propofol decreases LG. Therefore it exerts an overall stabilizing effect on control of breathing., (Copyright 2010 Elsevier B.V. All rights reserved.)

Introduction: The cuff-leak test has been proposed as a simple method to predict the occurrence of post-extubation stridor. The test is performed by cuff deflation and measuring the expired tidal volume a few breaths later (VT). The leak is calculated as the difference between VT with and without a deflated cuff. However, because the cuff remains deflated throughout the respiratory cycle a volume of gas may also leak during inspiration and therefore this method (conventional) measures the total leak consisting of an inspiratory and expiratory component. The aims of this physiological study were, first, to examine the effects of various variables on total leak and, second, to compare the total leak with that obtained when the inspiratory component was eliminated, leaving only the expiratory leak., Methods: In 15 critically ill patients mechanically ventilated on volume control mode, the cuff-leak volume was measured randomly either by the conventional method (Leakconv) or by deflating the cuff at the end of inspiration and measuring the VT of the following expiration (Leakpause). To investigate the effects of respiratory system mechanics and inspiratory flow, cuff-leak volume was studied by using a lung model, varying the cross-sectional area around the endotracheal tube and model mechanics., Results: In patients Leakconv was significantly higher than Leakpause, averaging 188 +/- 159 ml (mean +/- SD) and 61 +/- 75 ml, respectively. In the model study Leakconv increased significantly with decreasing inspiratory flow and model compliance. Leakpause and Leakconv increased slightly with increasing model resistance, the difference being significant only for Leakpause. The difference between Leakconv and Leakpause increased significantly with decreasing inspiratory flow (V'I) and model compliance and increasing cross-sectional area around the tube., Conclusion: We conclude that the cross-sectional area around the endotracheal tube is not the only determinant of the cuff-leak test. System compliance and inspiratory flow significantly affect the test, mainly through an effect on the inspiratory component of the total leak. The expiratory component is slightly influenced by respiratory system resistance.

Background: Noninvasive bilevel positive pressure ventilation (N-BiPAP) has an established role in providing respiratory support in patients with acute respiratory failure. The significant advantage of N-BiPAP is to avoid endotracheal intubation and its complications. Currently there are no data that support N-BiPAP as first-line treatment in patients with blunt thoracic trauma. Objective: To evaluate the safety and efficacy of N-BiPAP in patients with acute respiratory failure due to blunt thoracic trauma. Methods: Prospective observational study. Twenty-two patients with blunt chest trauma (mean injury severity score 26 ± 9) were studied. N-BiPAP was applied via a tight-fitting full or total-face mask, combined with regional anesthesia in all patients. Results:N-BiPAP resulted in significant changes in blood gasses, heart rate and breathing frequency at 1 h. Eighteen out of 22 patients avoided intubation and were discharged from the ICU (success group). Four patients met predefined criteria and required intubation (failure group) within 24 h after N-BiPAP. Three of the patients in the failure group survived while 1 developed septic shock and died. The acute response of oxygenation to N-BiPAP differed significantly between groups, being higher in the success group. Complications related to N-BiPAP were minor, consisting of nose bridge injury (1 patient) and gastric distention (1 patient). Conclusions: N-BiPAP administration could be a safe and effective method to improve the gas exchange in patients with acute respiratory failure due to blunt thoracic trauma. Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]