Respirator management of sepsis-related respiratory failure

The first description of acute respiratory distress syndrome (ARDS) in adults appeared in 1967 and was characterized by dyspnea, hypoxemia, diffuse alveolar infiltrates, and reduced respiratory system compliance. ARDS and acute lung injury (ALI) syndrome have no specific treatment, only supportive care: treating the underlying cause, when possible, and using mechanical ventilation. Historically, mechanical ventilation applied normal/large tidal volumes and low levels of positive end-expiratory pressure (PEEP). Experimental data showed that a high-volume, high-pressure ventilation strategy may lead to lung lesions indistinguishable from ARDS. Subsequent randomized clinical trials showed improved survival using low tidal volumes (6 vs 12 mL/kg ideal body weight) and limiting plateau pressure to 30 cm H(2)O, although the optimal level of PEEP remains controversial. Prone positioning should be reserved for severely ill patients. Inhaled nitric oxide, which is a pulmonary vasodilator with anti-inflammatory properties, is associated with limited improvement in oxygenation without improvement in survival

Following tracheal intubation, mucus flow is reversed in the semirecumbent position : possible role in the pathogenesis of ventilator-associated pneumonia

OBJECTIVES: Critically ill intubated patients are positioned in the semirecumbent position to prevent pneumonia. In tracheally intubated sheep, we investigated the effects of gravitational force on tracheal mucus transport and on bacterial colonization of the respiratory system. DESIGN: Prospective randomized animal study. SETTING: Animal research facility at the National Institutes of Health. SUBJECTS: Sixteen healthy sheep. INTERVENTIONS: Spontaneously breathing or mechanically ventilated sheep were randomized to be positioned with the orientation of the trachea above (40 degrees, trachea-up) or below (5 degrees, trachea-down) horizontal. MEASUREMENTS AND MAIN RESULTS: Tracheal mucus velocity was measured through radiographic tracking of radiopaque tantalum disks, insufflated into the trachea. After 24 hrs, sheep were euthanized, and samples from the airways and lungs were taken for microbiological analysis. The proximal trachea was colonized in all sheep. In trachea-down sheep, all mucus moved toward the glottis at a mean velocity of 2.1 +/- 1.1 mm/min. When mucus reached the endotracheal tube, it either entered the endotracheal tube or was lodged at the inflated endotracheal tube cuff. In all trachea-up sheep, abnormal tracheal mucus clearance was found. Mucus, mostly on the nondependent part of the trachea, moved toward the glottis at an average velocity of 2.2 +/- 2.0 mm/min and constantly accumulated at the inflated endotracheal tube cuff. From the proximal trachea, mucus eventually moved toward the lungs on the dependent part of the trachea, leading to an "intratracheal route" of colonization of the lungs. Pneumonia was found in 6/8 of trachea-up sheep and the same microorganisms were isolated from the lungs and the proximal trachea. No pneumonia was found in trachea-down sheep (p = .007). CONCLUSIONS: The study indicates that following tracheal intubation gravitational force influences tracheal mucus clearance. When the trachea is oriented above horizontal, a flow of mucus from the proximal trachea toward the lungs is highly associated with bacterial colonization of the airways and pneumonia

A double-layer tracheal tube cuff designed to prevent leakage : a bench-top study

OBJECTIVE: We designed a new endotracheal tube (ETT) cuff that does not form the folds that cause leakage of colonized subglottic secretions upon inflation within the trachea: a standard high-volume low-pressure cuff was draped with a second, highly elastic cuff made of a low-protein guayule natural latex rubber with 0.5 ml gel between the cuffs. We compared this prototype ETT cuff with four commercially available ETTs for efficacy in the prevention of fluid leakage across the cuff. DESIGN: In vitro study. MEASUREMENTS AND RESULTS: We compared fluid leakage in our prototype cuff with that in four commercially available ETTs. Three cylindrical glass tubes 16, 20, and 22 mm in diameter were used as model tracheas, and five different intracuff pressures (20, 25, 30, 40, and 50 cmH(2)O) were tested. Each test was repeated three times with new ETTs. The guayule latex ETT cuff showed an average fluid leakage of 0.0007 +/- 0.002 ml/min which was significantly lower than that in any of the other ETTs (Microcuff 0.07 +/- 0.09, Mallinckrodt/Hi-Lo Evac 5 +/- 5, Euromedical 7 +/- 4, Sheridan/CF 41 +/- 69). CONCLUSIONS: Our prototype ETT cuff significantly reduced fluid leakage in this bench-top study. In vivo testing and evaluation is to follow