Critical care medicine
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To determine the applicability of the Acute Physiology and Chronic Health Evaluation (APACHE) II scoring system in predicting outcome in a subgroup of critically ill obstetrical patients. ⋯ Obstetrical patients requiring intensive care in our ICU had a better outcome than predicted, as expressed by a low mortality ratio. Various explanations that may be applicable to any subgroup of critically ill patients with a different mortality ratio are presented. The subgroup itself may be uniquely different, similar to our obstetrical patients with their physiologic changes of pregnancy. Another explanation may relate to an improvement in care of the subgroup and therefore a better outcome.
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Critical care medicine · Sep 1994
Multicenter StudyDaily prognostic estimates for critically ill adults in intensive care units: results from a prospective, multicenter, inception cohort analysis.
To develop daily prognostic estimates for individual patients treated in adult intensive care units (ICU). ⋯ Equations using initial and repeated physiologic measurements provide a high degree of explanatory power for subsequent hospital mortality rate. These daily prognostic estimates deserve evaluation for their potential role in improving the process and outcome from clinical decision-making.
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Critical care medicine · Sep 1994
ReviewUnderstanding the pressure cost of ventilation: why does high-frequency ventilation work?
To understand when the use of high-frequency ventilation would be advantageous, we formulated the problem of achieving adequate alveolar ventilation at minimal pressure cost by dividing it into two simpler problems: a) the pressure cost per unit of convective oscillatory flow; and b) the convective flow cost necessary to achieve a unit of alveolar ventilation. ⋯ This analysis illustrates the importance of using high-frequency ventilation in infant respiratory distress syndrome and of optimizing the amount of PEEP. It also points out the danger of barotrauma in the derecruited lung. When the lungs are in a derecruited state, the combinations of frequency, PEEP, and tidal volume that yield adequate ventilation with safe distention of recruited alveoli are severely limited.
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Critical care medicine · Sep 1994
Comparative StudyMechanical respiratory system input impedance during high-frequency oscillatory ventilation in rabbits.
To study the mechanical properties of the rabbit respiratory system during high-frequency oscillatory ventilation by means of mechanical respiratory impedance measurement and to characterize the changes in oscillation mechanics of the respiratory system occurring after bilateral vagotomy. ⋯ Mechanical respiratory impedance measurement proved to be a useful method to study the mechanical properties of the respiratory system during high-frequency oscillatory ventilation. The results suggest that vagally mediated reflex changes in respiratory system mechanics are associated with high-frequency oscillatory ventilation, depending on the ventilatory variables that are used.
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To determine the influence of the dynamic properties of the oscillator on the oscillatory volume delivered through the endotracheal tube to the lung or lung surrogate (delivered volume) under conditions of high-frequency ventilation. In particular, the relation between the tidal volume of the pump (oscillator) and the delivered volume was analyzed. PaCO2 was measured further as a function of the delivered volume in a number of experiments performed with healthy dogs. ⋯ a) The delivered volume has to be monitored under clinical conditions; b) however, because the impedance of the endotracheal tube in general considerably exceeds the impedance of the lung, the influence of the impedance of the lung on the delivered volume is generally small, and thus an in vitro calibration may serve as a useful approximation; c) at least two independent quantities are needed for an adequate oscillatory control; d) a necessary (not necessarily sufficient) condition for adequate CO2 removal is that the delivered volume must exceed the machine-related deadspace; e) in a clinical environment involving extremely pathologic lung conditions, e.g., adult respiratory distress syndrome, mechanical lung characteristics may deviate substantially from those characteristics used in this study (i.e., the results obtained may not necessarily be applicable under all clinical situations).