Intensive care medicine
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Intensive care medicine · Jan 1992
Comparative StudyMonitoring of central venous oxygen saturation versus mixed venous oxygen saturation in critically ill patients.
Continuous monitoring of mixed venous (SvO2) and central venous (ScO2) oxygen saturation was compared in 7 critically-ill patients (Apache II score: 19 +/- 2.1) to determine whether or not information derived from ScO2 were reliable in clinical practice. Patients were catheterized with both a pulmonary artery (PA) and a central venous (CV) catheter, each of them mounted with fiberoptic sensors (Opticath PA Catheter P7110 and Opticath CV Catheter U440, Abbott). A total of 580 comparative measurements were obtained during periods without and with therapeutic interventions (drug-titration, bronchial suction, use of PEEP, changes in FiO2 ...). ⋯ There were poor correlations between the values during periods without (r = 0.48) and with therapeutic interventions (r = 0.62). Better, but still less than ideal, correlations were obtained with changes in SvO2 and ScO2 during periods without (r = 0.70) and with therapeutic interventions (r = 0.77). Although there is a need to develop a simple technique to monitor mixed venous oxygen saturation, the present study indicates that ScO2 monitoring was not reliable in the study patients.
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Intensive care medicine · Jan 1992
Tidal volume, breathing frequency, and oxygen consumption at different pressure support levels in the early stage of weaning in patients without chronic obstructive pulmonary disease.
The objective of this study was to evaluate the influence of different PSV levels on VT, F, VO2 in the early weaning phase of patients without chronic obstructive pulmonary disease. These parameters were tested for the predictive power for the success of the weaning. Patients on SIMV were studied during the first weaning attempt with PSV. ⋯ Responders and nonresponders could be separated by the response of VO2, VT and F to a change in PS 10 to PS 20 cmH2O. Patients who significantly increased VT and significantly decreased F did not fulfil our weaning criteria. Our responders did not show a significant change in these two parameters, but a significant increase in VO2 at PS 20 cmH2O could be observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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The development of the flexible, fiberoptic bronchoscope has made bronchoscopic examinations possible in ICU patients undergoing mechanical ventilation. Over the years, the number of such procedures has greatly increased, with both diagnostic and therapeutic objectives, such as performing difficult intubation, management of atelectasis and hemoptysis, diagnosis of nosocomial pneumonia in ventilated patients, and early detection of airway lesions in selected situations, such as high-frequency ventilation. The complication rate can be kept low if the endoscopist has a precise knowledge of the many pathophysiological and technical facets particular to bronchoscopy under these difficult conditions. This article reviews some of these aspects, in the light of our personal experience.
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Intensive care medicine · Jan 1992
Test of 20 similar intensive care ventilators in daily use conditions--evaluation of accuracy and performances.
Infrequent control, aging of components, may compromise the accuracy of ICU ventilators. In order to assess the reliability of ventilators during their clinical use, we bench tested a group of 20 CPU1 ventilators (Ohmeda) sampled at random in several ICU units. We found major leaks in 5 ventilators, attributable to the disposable tubings used in these systems. ⋯ The valve opening pressure threshold was correlated to the inspiratory flow (r = 0.81) contrary to the valve opening delay (average 138 +/- 40 ms). These two parameters did not correlate with the age of the ventilator. Our study addresses the need for periodic control of ventilator performance in order to minimize the risks of errors and malfunctions.
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Intensive care medicine · Jan 1992
Inspiratory work imposed by continuous positive airway pressure (CPAP) machines: the effect of CPAP level and endotracheal tube size.
Inspiratory work imposed by Continuous Positive Airway Pressure (CPAP) machines has been a matter of concern. The imposed inspiratory work of CPAP machine circuits (Wcir) and the effect of the total breathing apparatus with endotracheal tube (ETT) and connector included in the circuit (Wapp), were measured in three continuous flow (CF) and various configurations of three demand flow (DF) CPAP machines. The performance was assessed at 0, 5, 10 and 15 cmH2O CPAP using a Michigan Instruments Test Lung Model 1600, internal compliance set at 50 ml/cmH2O, driven at square wave inspiratory flows (VI) of 20, 40 and 60 l/min at a tidal volume of 500 ml. ⋯ No consistent advantage of CF over DF machines was demonstrated. There was little advantage of high gas flows (greater than 5 l/min) in various DF circuits. Within an individual machine maximum negative pressures generated during inspiration correlated with both Wcir and Wapp.