Journal of clinical monitoring and computing
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The Lightman is intended to test the optical and electrical properties of a pulse oximeter probe including the wavelength of the light emitting diode by means of a micro spectrometer. The aim of this study was to evaluate the ability of the Lightman to detect faulty pulse oximeter finger probes by testing the accuracy of the wavelength of the light emitting diode in isolation from the monitor. ⋯ Our findings suggest that the Lightman can detect faulty probes and predict reasonably accurately the direction of the probe's error. The Lightman may be considered as a useful tool to assess the accuracy of pulse oximeters. The national survey highlighted a wide variation in the testing procedure utilised to evaluate the accuracy of pulse oximeters. Introduction of guidelines regarding the testing procedure would promote a uniform practice.
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J Clin Monit Comput · Jun 2011
Power spectral analysis of plethysmographic pulse waveform in pregnant women.
To investigate the effect of pregnancy on the pulse wave of the mother. ⋯ The power of harmonics of pulse wave can be described by an exponential decay function with respect to the order of harmonics in both non-pregnant and pregnant women. The effects of pregnancy on the pulse wave are the reduction in the total power of pulse and the power of higher order harmonics, and the increase in the power of lower order harmonics in the power spectrum of pulse wave. This effect of pregnancy on the pulse wave might be caused by the decrease in vascular resistance during pregnancy, the increase in workload on the heart due to increased demand of the growing fetus, and the aortocaval compression caused by the progressively enlarged gravid uterus and fetus.
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J Clin Monit Comput · Jun 2011
Assessment of cerebral oxygenation using near infrared spectroscopy during isovolemic hemodilution in pediatric patients.
One means of limiting the need for allogeneic blood transfusions is isovolemic hemodilution where blood is removed in the operating room and replaced with isotonic fluids to maintain euvolemia. Although the delivery of oxygen to the tissues is generally maintained by compensatory physiologic mechanisms, there are limited data evaluating tissue oxygenation in actual clinical practice. The current study evaluates the effects of isovolemic hemodilution on cerebral oxygenation using near-infrared spectroscopy (NIRS). ⋯ Our data provides preliminary evidence supporting the safety of moderate isovolemic hemodilution in a pediatric population. We found that cerebral oxygenation is well maintained by compensatory mechanisms. Modalities such as NIRS to monitor end-organ oxygenation may be particularly valuable in patients with co-morbid disease processes which may affect end organ oxygenation or prevent the compensatory mechanisms that maintain oxygen delivery during anemia.
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Cyanosis was used for a century after dentists began pulling teeth under 100% N(2)O in 1844 because brief (2 min) severe hypoxia is harmless. Deaths came with curare and potent anesthetic respiratory arrest. Leland Clark's invention of a polarographic blood oxygen tension electrode (1954) was introduced for transcutaneous PO2 monitoring to adjust PEEP and CPAP PO2 to prevent premature infant blindness from excess O2 (1972). ⋯ Continuous monitoring of airway anesthetic concentration and oxygen also became very common after 1980. Death from anesthesia fell 10 fold between 1985 and 2000 as pulse oximetry became universally used, but no proof of a causative relationship to pulse oximetry exists. It is now assumed that all anesthesiologist became much more aware of the dangers of prolonged hypoxia, perhaps by using the pulse oximeters.
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J Clin Monit Comput · Jun 2011
Evaluation of mean systemic filling pressure from pulse contour cardiac output and central venous pressure.
The volemic status of a patient can be determined by measuring mean systemic filling pressure (Pmsf). Pmsf is obtained from the venous return curve, i.e. the relationship between central venous pressure (Pcv) and blood flow. We evaluated the feasibility and precision of Pmsf measurement. ⋯ During an inspiratory hold pulmonary flow and aortic flow equilibrate. Cardiac output estimates by arterial pulse contour and by a flow probe around the aorta are interchangeable. Therefore, the venous return curve and Pmsf can be estimated accurately by pulse contour methods.