Journal of critical care
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Journal of critical care · Dec 1999
Flow triggering added to pressure support ventilation improves comfort and reduces work of breathing in mechanically ventilated patients.
The purpose of this study was to measure the effect of flow triggering (FT), added to pressure support ventilation (PSV), during spontaneous breathing in intubated patients. ⋯ Flow triggering offers an excellent complement to PSV because it improves patient comfort and reduces the magnitude of the inspiratory effort as well as the delay time between inspiratory muscle contraction and gas flow. It augments gas exchange at no metabolic cost to the patient while reducing the work of breathing.
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Journal of critical care · Dec 1999
Clinical TrialInductance cardiography (thoracocardiography): a novel, noninvasive technique for monitoring left ventricular filling.
Thoracocardiography noninvasively records left ventricular volume curves by an inductive plethysmographic transducer transversely encircling the chest near the xiphoid process. Amplitudes of thoracocardiographic curves track stroke volume as previously validated by thermodilution. We investigated whether thoracocardiographic curves reflect left ventricular filling. ⋯ Thoracocardiography reflects characteristics of left ventricular filling similar to Doppler echocardiography. Because it does not require hand-holding a transducer, thoracocardiography has the potential for continuous monitoring of mechanical cardiac performance.
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Journal of critical care · Dec 1999
Experimental critical care in ventilated rats: effect of hypercapnia on arterial oxygen-carrying capacity.
We have previously demonstrated an increased arterial O2-carrying capacity in normal ventilated dogs subjected to both acute and prolonged exogenous hypercapnia. In the present study, we tested if arterial hypercapnia, during controlled ventilation, can increase O2-carrying capacity also in rats. ⋯ Rats subjected to controlled ventilation and permissive hypercapnia, unlike dogs and perhaps humans, show no augmentation of Hb concentration. Hypercapnia in rats also provokes much stronger Bohr effect than in dogs. Hypercapnia-induced Bohr effect in rats is accompanied with extreme desaturations of Hb-O2, and substantial reduction in the O2-carrying capacity. We speculate that the strong hypercapnia-induced Bohr effect in rats may prevent hypoxia at the tissue level. However, to maintain a stable oxygen-carrying capacity in rats used for pulmonary critical care studies with hypercapnia, we suggest to use hyperoxia, with or without a mild hypothermia.
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Journal of critical care · Dec 1999
A model analysis of lactate accumulation during muscle ischemia.
The mechanistic basis of the relationship between tissue [O2] and tissue or blood lactate (LA) concentration during tissue hypoxia are not fully understood. However, blood and tissue lactate accumulation are still used as indicators of tissue hypoxia in critically ill patients. To investigate this relationship, we applied a previously developed mathematical model of human bioenergetics to simulate the integrated responses (cellular, tissue, and whole body) to moderate (10% to 45%) and severe (50% to 80%) reductions in muscle blood flow. ⋯ Based on the simulations, the commonly used threshold value for venous [LA]/[PY] = 14 as evidence of tissue hypoxia seems appropriate during severe ischemia.
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Journal of critical care · Dec 1999
Nitric oxide metabolism in canine sepsis: relation to regional blood flow.
To investigate the role of nitric oxide (NO) in early endotoxemia on the systemic and regional blood flow by measuring the plasma nitrite/nitrate (NOx) and blood nitrosyl-hemoglobin (NO-Hb) levels. ⋯ In the early phase of endotoxemia in the dog, the significant reduction in systemic vascular resistance and hepatic arterial resistance are not associated with any measurable NOx release in the systemic circulation or the liver.