Critical care medicine
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Capnography, the science of CO2 waveforms analysis, can play a role in the management of mechanically ventilated patients. Mass spectrometers are the devices most commonly used to collect sequentially and examine CO2 waveforms from multiple patients in the ICU or operating rooms. ⋯ The patient's progress during weaning and the consequences of changes in mechanical assistance can be virtually and noninvasively determined. An expanded role of capnography in mechanically ventilated patients can increase the use of mass spectrometers in the ICU.
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Critical care medicine · May 1988
Comparative StudyCardiac output changes and continuous mixed venous oxygen saturation measurement in the critically ill.
For many years, the pulmonary artery catheter has been used to monitor cardiac filling pressures and to determine cardiac output in hemodynamically unstable patients. Recently, a new pulmonary artery catheter with fiberoptic capabilities, which provides continuous mixed venous O2 saturation (SvO2) measurements, has become available and has been found to be helpful in managing unstable patients. ⋯ More importantly, we found that only 50% of the SvO2 changes predicted anticipated changes in cardiac output. As can best be determined from the limitations of a nonrandomized study, the value of continuous SvO2 monitoring as an early predictor of cardiac output change remains questionable.
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Critical care medicine · May 1988
Comparative StudyMulticomponent noninvasive physiologic monitoring of circulatory function.
A multicomponent noninvasive monitoring system for high-risk critically ill patients was developed and tested in a series of 58 high-risk surgical patients. The system was comprised of a thoracic electric bioimpedance (TEB) method for cardiac output estimation, laser-Doppler velocimeter for small vessel flow, transcutaneous oxygen (PtcO2) sensor for tissue oxygenation, pulse oximeter for arterial hemoglobin saturation (SaO2) and finger pressor sensor for arterial pressure. In a series of critically ill patients, this noninvasive system was compared with the widely used invasive monitoring system with systemic and pulmonary artery catheters. ⋯ Monitored events defined as abrupt reductions in these variables often occurred from reduced cardiac output, PtcO2 or PtcO2/PaO2 index, and infrequently from unanticipated reductions in SaO2. Recovery from the nadir of the monitored event was associated usually with improvements in flow, PtcO2, or both. Hemodynamic and oxygen transport patterns of a few commonly encountered patterns are described.
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Critical care medicine · May 1988
Dissociation of mean airway pressure and lung volume during high-frequency oscillatory ventilation.
Eight kittens were studied during high-frequency oscillatory ventilation (HFOV) using an airway vibrator. HFOV was performed at 1000 and 1800 cycle/min at three present oscillatory amplitude settings and with lungs normal and injured by saline lavage. Change in lung volume (LV) during HFOV was compared to change in LV obtained during static inflation at matched mean airway pressure (Paw) of 5, 10, 15 and 20 cm H2O. ⋯ LV was significantly lower after lung injury for matched HFOV settings, and was not affected by rate. Dissociation of Paw and LV during HFOV is observed implying that mean alveolar pressure (Palv) exceeds Paw during HFOV in this experimental model. The safe clinical application of HFOV may involve measurement of Palv or LV.