Critical care medicine
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Critical care medicine · Sep 1994
Value of routine pressure monitoring system changes after 72 hours of continuous use.
To assess the infection potential of not routinely changing invasive monitoring kits and associated plasticware. ⋯ Invasive hemodynamic pressure monitoring systems including tubing and plasticware need not be changed routinely as these changes may cause a higher incidence of contamination due to increased violations of the systems.
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Critical care medicine · Sep 1994
Cerebral lactate-oxygen index in acute brain injury with acute anemia: assessment of false versus true ischemia.
To evaluate the occurrence of global cerebral ischemia in acute brain trauma with acute anemia by combined measurements of cerebral hemodynamics, oxygenation, and lactate production. ⋯ In acute brain injury with acute anemia, global cerebral ischemia is a rare finding. However, false cerebral ischemia may be frequently found, if assessed by the lactate-oxygen index, because the denominator of the index (the arteriojugular oxygen content difference) frequently decreases as a function of decreasing hemoglobin, thus yielding false calculated ischemic high values for lactate-oxygen index despite normal cerebral oxygenation and lactate production.
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Critical care medicine · Sep 1994
Airway pressure measurements during high-frequency positive pressure ventilation in extremely low birth weight neonates.
Evaluation of a modified, computer-controlled, shutter method to determine the complete intrapulmonary pressure course and to ascertain the expiratory time constant for the respiratory system during high-frequency positive pressure ventilation. ⋯ The computer-controlled shutter method is noninvasive and applicable without impairment, even in preterm neonates with birth weights of < 1000 g. This method provides important information to optimize respiratory therapy, particularly knowledge of the individual time constant. To avoid inadvertent positive end-expiratory pressure and gas trapping, expiratory time should be > 4 time constants.
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Controversy exists as to whether high-frequency oscillatory ventilation can be used on babies and small laboratory animals only, or whether high-frequency oscillatory ventilation can also be efficient in the adult patient and large (> 65 kg body weight) laboratory animals. Moreover, controversy exists as to whether limitations in high-frequency oscillation efficiency are caused by the size and shape of the bronchial system, by the lack of low impedant intersegmental gas flow in lung parenchyma, or by inappropriate high-frequency ventilators and ancillary hardware. Therefore, our objective in this study using the adult pig as a model of the adult patient was to test whether the adult airway system is suited to the use of high-frequency oscillatory ventilation or whether there are geometrical, structural, or functional limitations to efficient ventilation by high-frequency oscillation. ⋯ Adult pigs with a body weight in the range of the weight of clinical adult patients can be ventilated by high-frequency oscillation at tidal volumes smaller than, equal to, or slightly more than anatomical deadspace. The most efficient frequency for gas exchange varied between individuals. Tidal volume had an enhancing effect on CO2 elimination. The frequency dependency of PaO2 may have been related to a frequency-dependent structural remodeling of the airway system, which occurred even though the mean airway pressure was kept constant. These results demonstrate that failure of adequate ventilation by high-frequency oscillation is caused by a) CO2 rebreathing, b) the avoidance of an appropriate alveolar recruitment strategy, and c) an underpowered, high-frequency ventilatory system (oscillator) that is unable to deliver appropriate pressure oscillations. These limitations led to insufficient CO2 elimination and/or inadequate arterial oxygenation.
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Critical care medicine · Sep 1994
Clinical experiences with high-frequency oscillatory ventilation in newborns with severe respiratory distress syndrome.
To generate hypotheses about which subgroups of newborns with severe respiratory distress syndrome might benefit most from high-frequency oscillatory ventilation. ⋯ As a result of our analysis, we hypothesize that term newborns with severe respiratory distress syndrome complicated by persistent pulmonary hypertension and hypercarbia can benefit from high-frequency oscillatory ventilation. Premature neonates with ventilation-induced lung injury are not likely to respond to high-frequency oscillatory ventilation.