Critical care medicine
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Critical care medicine · Sep 1988
Comparative StudySome infant ventilators do not limit peak inspiratory pressure reliably during active expiration.
In order to minimize barotrauma in newborn infants with respiratory failure, peak inspiratory pressures should not exceed those required for adequate gas exchange. We examined whether four commonly used pressure-limited, constant flow ventilators limit pressure reliably during simulated active expiration against the inspiratory stroke of the ventilator. Three machines of each type were tested at 13 different expiratory flow rates (2 to 14 L/min). ⋯ Pressure overshoot above 20 cm H2O was consistently lowest in the Healthdyne (0.8 cm H2O at 2 L/min, 3.6 cm H2O at 14 L/min) and highest in the Bourns BP200 (3.0 cm H2O at 2 L/min, 15.4 cm H2O at 14 L/min). We conclude that peak inspiratory pressure overshoots on pressure-limited ventilators occur during asynchronous expiration. This shortcoming may contribute to barotrauma in newborn infants who "fight" positive-pressure ventilation.
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Critical care medicine · Sep 1988
Comparative StudyUse of flexible fiberoptic endoscopy for determination of endotracheal tube position in the pediatric patient.
Flexible fiberoptic endoscopy (FFE) was utilized in a series of 24 critically ill pediatric patients to determine the position of the endotracheal tube (ETT) tip relative to the carina. Training on a model system revealed no significant differences in predicting ETT-to-carina distance (ETT-C) with respect to operator, ETT size, or absolute ETT-C as measured directly. No significant differences in ETT-C could be determined between traditional bedside chest x-ray (CXR) or FFE when FFE was performed on intubated pediatric ICU patients. ⋯ No clinically significant changes in patient pulse oximetry, heart rate, or physical exam were observed during FFE. Only copious secretions impaired the utility of FFE. We concluded that FFE is a safe, fast, easily learned method to determine relative ETT position or precise ETT-C in the mechanically ventilated pediatric patient.
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Critical care medicine · Sep 1988
Comparative StudyCerebral effects of isovolemic hemodilution with crystalloid or colloid solutions.
The cerebral effects of iv fluids have not been well defined, particularly the differences between crystalloids and colloids. We thus evaluated the effects of lactated Ringer's (LR) and 6% hetastarch (HES) solutions on brain edema, intracranial pressure (ICP), and cerebral blood flow (CBF) in anesthetized rabbits, using a model of isovolemic hemodilution (IVHD). In this model, arterial blood was removed at a rate of approximately 2 ml/min for one hour and replaced simultaneously with LR or HES in amounts needed to maintain arterial BP and CVP; Hct decreased from approximately 40% to approximately 19%. ⋯ To permit the examination of both acute and delayed fluid effects, each group was further divided into two subgroups (n = 6 each): one in which animals were sacrificed immediately on completion of the one-hour IVHD period (early), and one in which animals were sacrificed 4 h later (late). After sacrifice, brain and skeletal muscle water contents (% H2O) were determined, and the specific gravity (SpGr) of multiple brain samples was measured. Much larger volumes of LR were required to maintain normovolemia as compared with HES, (e.g., totals 203 +/- 68 vs. 76 +/- 18 ml/kg, respectively in late animals) and those given LR had larger increases in body weight and muscle % H2O.(ABSTRACT TRUNCATED AT 250 WORDS)
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Critical care medicine · Sep 1988
Comparative StudyRewarming from experimental hypothermia: comparison of heated aerosol inhalation, peritoneal lavage, and pleural lavage.
This study compares the thermal transfer and rewarming characteristics of heated aerosol inhalation (HAI) alone and combined with peritoneal lavage (PEL) or pleural lavage (PLL). Closed-system PEL and PLL are equally efficient at rewarming hypothermic dogs and do so at a rate approximating 6 degrees C/h/m2. Cardiovascular responses to PEL and PLL were similar. ⋯ HAI alone provides little heat for rewarming; more heat is realized from endogenous metabolism. Nevertheless, HAI's ease of use and possible selective cardiac rewarming characteristics argue for its inclusion with other methods of active rewarming. The use of PEL or PLL is governed by clinical circumstances.