Clinical physiology and functional imaging
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Clin Physiol Funct Imaging · Jul 2006
Measurement of expired carbon dioxide, oxygen and volume in conjunction with pretest probability estimation as a method to diagnose and exclude pulmonary venous thromboembolism.
The classical alveolar pCO(2)-pO(2) relationship predicts that pulmonary embolism (PE) causes a low ratio of pCO(2)/pO(2) at end expiration. Our purpose was to define a simple protocol to collect expired pCO(2)/pO(2) to diagnose PE. Emergency department patients with suspected PE were enrolled. Clinical pretest probabilities for PE were estimated prior to diagnostic testing using the Canadian score and clinicians' unstructured estimate. Patients provided three 30-s periods of tidal breathing, separated by three deep exhalations. Expired pCO(2), pO(2) and breath volume were measured. All patients underwent standardized objective testing for PE including 90-day follow-up. Diagnosis (PE+) required anticoagulation for image-proven PE within 90 days. ⋯ This preliminary work demonstrates that the end-tidal pCO(2)/pO(2) averaged from 30 s of breathing can produce clinically relevant likelihood ratios for the diagnosis and exclusion of PE.
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Clin Physiol Funct Imaging · May 2006
Test-retest reliability for two indices of ventilatory efficiency measured during cardiopulmonary exercise testing in healthy men and women.
The level of ventilation (VE)) at a given carbon dioxide output (CO2) determines ventilatory efficiency. During cardiopulmonary exercise testing (CPET), ventilatory efficiency can be measured as the slope of the (VE) versus VCO2 relationship or the lowest VE/VCO2. We evaluated the test-retest reliability of these two ventilatory efficiency indices in 29 healthy subjects (14 males). ⋯ The bias (mean of difference scores between tests) and 95% limits of agreement for the VE versus VCO2 slope in the males, females, and both sexes combined were -0.05 +/- 2.41, -0.57 +/- 1.92, and -0.32 +/- 2.20, respectively. The bias and 95% limits of agreement for the lowest VE/VCO2 were very similar with values of 0.06 +/- 2.45, -0.22 +/- 2.03, and -0.10 +/- 2.27. We conclude that the test-retest reliability for the VE versus VCO2 slope and the lowest VE/VCO2 is the same and that there is no sex difference in reliability for either index of ventilatory efficiency.
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Clin Physiol Funct Imaging · Mar 2006
Multiple pressure-volume loops recorded with sinusoidal low flow in a porcine acute respiratory distress syndrome model.
To develop a method for automatic recording of multiple dynamic elastic pressure-volume (P(el)/V) loops. To analyse the relationship between multiple dynamic P(el)/V loops and static P(el)/V loops in a porcine model of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). To test the hypothesis that increasing lung collapse and re-expansion with decreasing positive end expiratory pressure (PEEP) can be characterized by hysteresis of the P(el)/V loops. MATERIAL AND INTERVENTIONS: In eight anaesthetized and paralysed pigs, ALI/ARDS was induced by inhalation of dioctyl sodium sulfosuccinate and large tidal volume ventilation. ⋯ Automated multiple P(el)/V loop determination is feasible and provides comprehensive information on lung derecruitment and recruitment. It requires determination of volume dependence of expiratory resistance. An expiratory curve serves as a reference to inspiratory curves and provides information about hysteresis.
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Clin Physiol Funct Imaging · Nov 2005
Clinical TrialRecording of dynamic arterial compliance changes during hand elevation.
Finger arterial compliance has been studied on the beat-to-beat basis by using the digital arterial pressure and volume waveforms and performing measurements at zero transmural pressure during arm elevation in 11 volunteers. Continuous non-invasive finger blood pressure was measured by applying the Finapres monitor and the finger volume pulses were recorded by the UT9201 physiograph by using the photoplethysmographic principle of registration. ⋯ The results of the study demonstrate that the applied two methods similarly (correlation coefficient r = 0.97) describe the changes of the beat-to-beat compliance during hand elevation test. At the same time the second estimate was 18% higher than the first one (P = 0.003).
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Ventilation with pure oxygen (hyperoxic ventilation, HV) increases arterial oxygen content (CaO(2)). However HV induces arteriolar constriction and thus potentially affects O(2) supply. We therefore investigated the effects of HV on regional blood flow (RBF) and O(2) supply of different vital organs during moderate normovolaemic anaemia. ⋯ The initiation of HV during moderate normovolaemic anaemia (Hb =7 g dl(-1)) was accompanied by RBF redistribution with preference for renal, hepatic and intestinal O(2) supply. Cardiac, pancreatic and muscular O(2) supply decreased, however without any critical restriction of organ function.