Physiological measurement
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Physiological measurement · Aug 2002
Comparative StudyInvestigation of oesophageal photoplethysmographic signals and blood oxygen saturation measurements in cardiothoracic surgery patients.
Pulse oximeter probes attached to the finger may fail to estimate blood oxygen saturation (SpO2) in patients with compromised peripheral perfusion (e.g. hypothermic cardiopulmonary bypass surgery). The measurement of SpO2 from a central organ such as the oesophagus is suggested as an alternative to overcome this problem. A reflectance oesophageal pulse oximeter probe and a processing system implemented in LabVIEW were developed. ⋯ Also, the oesophageal pulse oximeter was found to be reliable and accurate in five cases of poor peripheral perfusion when a commercial finger pulse oximeter probe failed to estimate oxygen saturation values for at least 10 min. These results suggest that the arterial blood circulation to the oesophagus is less subject to vasoconstriction and decreased PPG amplitudes than are the peripheral sites used for pulse oximetry such as the finger. It is concluded that oesophageal SPO2 monitoring may be of clinical value.
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Physiological measurement · Aug 2002
Noninvasive quantification of respiratory modulation on left ventricular size and stroke volume.
To noninvasively explore the complex interactions between heart rate, left ventricular (LV) stroke volume (SV) and respiration, different techniques were proposed and applied to the beat-to-beat measurements of end-diastolic (ED), end-systolic (ES) volumes and SV, obtained from echocardiographic acoustic quantification LV volume signal. Data were obtained from eight patients with dilated cardiomyopathy (DCM, age 60 +/- 2, mean +/- SE), and from 11 age-matched healthy volunteers (N, age 63 +/- 2). ⋯ Moreover, the prevalent effect of increased afterload generating SV reduction during inspiration was pointed out in N, while an intersubject dispersion in the relation between respiratory phase and LV dimension changes was found in DCM. Black-box model identification summarized these mechanisms by means of a few quantitative parameters.
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Physiological measurement · Aug 2002
On-line, simultaneous quantification of ethanol, some metabolites and water vapour in breath following the ingestion of alcohol.
Selected ion flow tube mass spectrometry, SIFT-MS, has been used to measure simultaneously the concentrations in exhaled breath of ethanol, acetaldehyde, ammonia, acetone and, routinely, water vapour, following the ingestion of various amounts of ethanol in 500 ml of water. These breath analyses were obtained from only single exhalations, the results being available immediately in real time. The breath ethanol reaches concentrations that are only approximately consistent with its dilution in blood and body water. ⋯ The simultaneous breath acetone concentrations increase somewhat with time as is expected during the fasting state. The water vapour measurements are indicators of the precision and accuracy of the breath analyses, these being sufficient to show the differences between the breath (body) temperatures of the individuals of less than 1 degrees C. This study demonstrates the potential of SIFT-MS for non-invasive physiological measurement.