Articles: mechanical-ventilation.
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Pediatr Crit Care Me · Jul 2000
Comparison of predictors of extubation from mechanical ventilation in children.
Unsuccessful extubation from mechanical ventilation increases mortality and morbidity. Therefore, the identification of an accurate predictor of successful extubation is desirable. This study was designed to determine whether the results of easily performed respiratory measurements, particularly if reported as "combined extubation" indices, were better predictors of extubation failure in a pediatric population than were readily available clinical data. DESIGN: Prospective observational study. SETTING: Tertiary pediatric intensive care unit. PATIENTS: All children who required mechanical ventilation for >/=24 hrs during a 12-month period and whose parents gave informed written consent. INTERVENTIONS: Respiratory function measurements were made (on average) 7 hrs (range, 0.2-25.0 hrs) before extubation. Arterial blood gas results were obtained immediately before extubation. The values of each predictor associated with maximum sensitivity and specificity were determined, and the areas under receiver operator characteristic curves were compared to determine the most accurate predictor of successful extubation. MEASUREMENTS AND MAIN ⋯ Volume measurements during pediatric mechanical ventilation may facilitate successful extubation.
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Pediatr Crit Care Me · Jul 2000
Comparison of plasma levels and pharmacodynamics after intraosseous and intravenous administration of fosphenytoin and phenytoin in piglets.
To compare plasma drug levels and pharmacodynamics of fosphenytoin or phenytoin when given intraosseously or intravenously in doses relevant to children. DESIGN: Prospective controlled randomized study. SETTING: University hospital animal laboratory. SUBJECTS: A total of 40 mixed-breed piglets (age, 4-6 months; weight, 20-40 kg). INTERVENTIONS: The animals were anesthetized, after which they underwent intubation, instrumentation, and mechanical ventilation. A central venous catheter and an arterial catheter were placed for monitoring and blood sampling. A peripheral intravenous catheter with a 15-gauge intraosseous needle was inserted for drug infusion. A total of 40 animals (ten per group) were randomly assigned to receive intravenous or intraosseous phenytoin or fosphenytoin infusions. Phenytoin (20 mg/kg) was infused over 20 mins, and fosphenytoin (20 mg phenytoin equivalent kg) was infused over 7 mins. All infusions were followed by the administration of a 5-mL normal saline flush. MEASUREMENTS AND MAIN ⋯ There is no need to adjust standard drug doses of phenytoin when given intraosseously. The initial high levels of phenytoin in the fosphenytoin groups are of concern because neurologic toxic effects may occur in humans at those levels. Slower infusion rates of fosphenytoin may be needed to avoid toxic levels.
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To measure airflow resistance in prongs of nasal CPAP, making use of different gas admission flow (GAF) in the ventilation circuit, in different internal diameters of the nasal prongs, besides verifying whether a GAF responding only to the demand of three times the minute-volume(MV) is enough to the circuit not to be cause of CO(2) retention. METHODOLOGY: Nasal prongs, assembled in the original circuits, were used, having their prongs kept open to the atmosphere. Pressure was read at a pressure monitor, in water centimeters, connected to the appropriate entrance of the circuit. A flowmeter balanced to the pressure was used, gauged at 50 psi, installed to the oxygen net of the Hospital, connected to the assessing set of the CPAP circuit. Initially, making use of the 8 l/min flow and keeping the exhaling set of the circuit closed, it was possible to eliminate the nasal prongs larger than two once the measured resistance was equal to zero. Having nasal parts number zero, 1 and 2 selected for this study, the system was then assembled as for the neonate: the inhaling set to the gas source and the exhaling set sunk into different depths in the water seal (2, 4, 6 and 8 centimeters). At the level of patient analysis, in order to assess the CO(2) retention, a mechanical pulmonary ventilation device was used as gas source and a nasal CPAP circuit was assembled to the device in adequate places. GAF values and FiO(2) were determined in the commands of the mechanical ventilation device. The assessment of gas concentration in the ventilation circuit was made while assisting two newborns. Gas samples were obtained within the ventilation circuit in the system assessing set (samples A), and right after the distal prong to the gas entrance (samples B). To determine MV the Tidal Volume (considered 10ml/kg) was multiplied by the respiratory frequency of the patient; GAF was three times MV. ⋯ Taking into account that during ventilation assistance through nasal CPAP there is the possibility of GAF incurring in the increase in resistance, what would involve a greater effort from the newborn to overcome such resistance during exhaling into the system (generating possibly an unexpected CPAP), and minimum GAF determined is that sufficient to meet no more than three times the MV, the conclusion is that prongs with the largest internal diameter possible and GAF only the necessary to meet, at least, the needs of the demand three times the MV should be used during this therapeutic procedure.
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Semin Respir Crit Care Med · Jan 2000
Techniques for automated feedback control of mechanical ventilation.
Mechanical ventilators have become more sophisticated with the advent of microprocessor control. Advances in monitoring have also improved our ability to harmonize patient-ventilator interaction. The next obvious step in this technologic progression is to turn over some decision making to the ventilator. ⋯ An example is the automated control of pressure support to maintain a deired tidal volume. More sophisticated closed-loop techniques, such as proportional assist ventilation and adaptive support ventilation, not only monitor multiple input variables but also use closed-loop control of several variables. This article reviews the closed-loop ventilation modes currently available to clinicians.
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Journal of anesthesia · Dec 1997
Effect of fentanyl on heart rate variability during mechanical ventilation.
This study was performed to investigate the effect of fentanyl alone on heart rate variability (HRV) during mechanical ventilation using power spectral analysis. Arterial baroreceptor reflex was also tested with pharmacological manipulation to assess the contribution of vagal baroreceptor reflex modulation of HRV during fentanyl anesthesia. ⋯ Our data indicate that fentanyl modulates the respiratory frequency fluctuation of HRV. This is partly caused by the effects of fentanyl on arterial baroreflex sensitivity.