Chest
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Randomized Controlled Trial Comparative Study Clinical Trial
Fluid balance during pulmonary edema. Is fluid gain a marker or a cause of poor outcome?
To evaluate the importance of fluid balance and changes in extravascular lung water (EVLW) on survival in the ICU and short-term outcome in patients with pulmonary edema. ⋯ These data support the concept that positive fluid balance per se is at least partially responsible for poor outcome in patients with pulmonary edema and defend the strategy of attempting to achieve a negative fluid balance if tolerated hemodynamically.
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Comparative Study
Comparison of inspiratory work of breathing in T-piece breathing, PSV, and pleural pressure support ventilation (PPSV).
We have compared the inspiratory work of breathing during T-piece breathing, pressure support ventilation (PSV), and pleural pressure support ventilation (PPSV) by using a lung model with variable compliance and resistance, under simulated spontaneous breathing. Our lung model consists of two spring-loaded bellows, representing the lung and diaphragm, placed in an airtight container. Inspiration begins with the withdrawal of air from the diaphragm bellows by a time-cycled jet-flow-creating Venturi mechanism. ⋯ The serious limitations of PSV remain in its application to the lung with high resistance. It is concluded that PPSV is closer to the actual patient's signal and has a potential advantage in reducing WOB in the lung with low compliance or high resistance (or both). The lung with flow limitation is still a challenging issue for mechanical ventilatory assistance.
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To evaluate the interaction between patient and ventilator during widely varying levels of pressure support (PS) ventilation, we studied 33 patients who had undergone aortocoronary bypass. All patients were without preoperative evidence of lung disease and had left ventricular ejection fractions greater than 45 percent. We assessed both changes in ventilatory pattern and the use of an extension of the Campbell technique to determine the components of the mechanical work of breathing (WOB). ⋯ We were surprised to observe that although inspiratory WOB fell 67 +/- 13 percent as the PSL increased to 30 cm H2O, postinspiratory work by the inspiratory muscles (WOBPIIM) did not show significant change. The persistence and substantial values of WOBPIIM in some patients suggested the presence of significant patient-ventilator dyssynchrony, especially at higher levels of PS. Total inspiratory WOB per minute, including both patient WOB and WOB by the ventilator, increased by 186 +/- 29 percent, demonstrating that PS results in a respiratory pattern requiring substantially greater total mechanical work.
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Ventilator autocycling can occur with any ventilator if the sensitivity is improperly set or if a gas leak exists in the respiratory system which creates a negative change in proximal airway pressure. We report a case of ventilator autocycling in a paralyzed patient secondary to an endotracheal cuff leak which was misconstrued as assisted ventilation. We believe this is the first report of autocycling due to a cuff leak.