The American review of respiratory disease
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Am. Rev. Respir. Dis. · Oct 1993
Airway occlusion pressure and breathing pattern as predictors of weaning outcome.
Airway occlusion pressure (P0.1) and the ratio of breathing frequency (f) to tidal volume (VT) (f/Vt) are good predictors of weaning outcome. However, the specificity of f/VT in predicting weaning success is relatively low. We postulated that the product of P0.1 and f/VT (P0.1*f/VT) would better predict weaning outcome than either variable alone. ⋯ The areas under the ROC curves for P0.1*f/VT, P0.1, and f/VT were not significantly different. We conclude that P0.1*f/VT has equivalent sensitivity as P0.1 and f/VT. P0.1 slightly improves the specificity of f/VT in predicting weaning success.
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Am. Rev. Respir. Dis. · Oct 1993
Comparative StudyDelivery of ultrasonic nebulized aerosols to a lung model during mechanical ventilation.
Ultrasonic nebulizers may be particularly suitable for the administration of therapeutic aerosols to patients undergoing mechanical ventilation, but the amount of aerosol that reaches the patients' respiratory tract during ultrasonic nebulization has not been adequately studied. The delivery through an endotracheal tube of nebulized aerosols labeled with 99mTechnetium human serum albumin was therefore measured for five commercially available ultrasonic nebulizers using an in vitro model representing mechanical ventilation of an adult patient. Delivery of aerosol through the endotracheal tube ranged from 3.1 +/- 0.3% for Samsonic to 10.1 +/- 2.0% for Portasonic using 3 ml nebulizer solution. ⋯ Addition of a 600 ml aerosol storage chamber to the ventilator circuit increased delivery for the Samsonic (18 ml solution) to 22.3 +/- 5.0%. Aerosol delivery was also increased by reducing the respiratory rate and minute volume and by increasing the inspiratory time settings on the ventilator. These results confirm the potential value of ultrasonic nebulizers during mechanical ventilation and indicate that clinical trials in ventilated patients are warranted.
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Am. Rev. Respir. Dis. · Sep 1993
Comparative StudyModes of tracheal gas insufflation. Comparison of continuous and phase-specific gas injection in normal dogs.
Tracheal gas insufflation (TGI) improves the efficiency of CO2 elimination accomplished by conventional mechanical ventilation, primarily by reducing the anatomic (series) dead space volume. Dead space proximal to the catheter tip can be reduced by two methods. Fresh gas introduced at the carinal level during inspiration may effectively "bypass" the upper airway. ⋯ Continuous catheter flow at 5 or 10 L/min reduced PaCO2 and physiologic dead space fraction (VD/VT) more than either proximal bypass or end-expiratory washout (p < 0.001). At the same catheter flow settings expiratory washout tended to improve VD/VT more than did inspiratory bypass. Under the conditions tested, constant tracheal insufflation of fresh gas improves alveolar ventilation by mechanisms that include, but are not limited to, a functional reduction in the dead space proximal to the catheter tip.
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Am. Rev. Respir. Dis. · Sep 1993
Comparative StudyTidal volume measurements in newborns using respiratory inductive plethysmography.
Respiratory inductive plethysmography (RIP) is a well-accepted noninvasive technology for monitoring breathing patterns in adults. Prior attempts to calibrate this device in babies have been fraught with technical difficulties, thereby limiting applications in this population. Recently, a new method, qualitative diagnostic calibration (QDC), has been shown to provide accurate calibration of tidal volume in adults. ⋯ In the supine and prone postures, weighted mean difference between RIP (VT) and PNT (VT) and 95% confidence intervals were -0.05 ml (-0.27, 0.18) and -0.32 ml (-0.08, 0.55), respectively. There was no difference in the accuracy of RIP relative to PNT calibrated during active sleep when thoracoabdominal incoordination was present or quiet sleep when it was not in either the supine or the prone postures. Therefore, in full-term infants, RIP calibrated with QDC solely in the supine posture provides clinically acceptable measurements of VT in both supine and prone postures.