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Oxygen Difference (oxygen + difference)

Distribution by Scientific Domains
Medical Sciences60%
Life Sciences40%

Selected Abstracts

Physiological Society Symposium , the Athlete's Heart

EXPERIMENTAL PHYSIOLOGY, Issue 5 2003
Athlete's heart, effect of age, ethnicity, sporting discipline
Regular physical training is associated with several physiological and biochemical adaptations which enable an increase in cardiac output and widening of the systemic arterio-venous oxygen difference. An increase in cardiac chamber size is fundamental to the generation of a sustained increase in cardiac output for prolonged periods. Echocardiographic studies have shown that the vast majority of athletes have modest cardiac enlargement although a small proportion exhibit substantial increases in heart size. Recognised determinants of cardiac size include age, sex, ethnicity and type of sport. Cardiac dimensions vary considerably amongst athletes, even when allowances are made for these variables, suggesting that genetic, endocrine and biochemical factors also influence heart size. This review discusses the effects of age, sex, ethnicity and sporting discipline on cardiac dimensions in athletic individuals. [source]

Electrical impedence tomography and heterogeneity of pulmonary perfusion and ventilation in porcine acute lung injury

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 10 2009
A. FAGERBERG
Background: The heterogeneity of pulmonary ventilation (V), perfusion (Q) and V/Q matching impairs gas exchange in an acute lung injury (ALI). This study investigated the feasibility of electrical impedance tomography (EIT) to assess the V/Q distribution and matching during an endotoxinaemic ALI in pigs. Methods: Mechanically ventilated, anaesthetised pigs (n=11, weight 30,36 kg) were studied during an infusion of endotoxin for 150 min. Impedance changes related to ventilation (ZV) and perfusion (ZQ) were monitored globally and bilaterally in four regions of interest (ROIs) of the EIT image. The distribution and ratio of ZV and ZQ were assessed. The alveolar,arterial oxygen difference, venous admixture, fractional alveolar dead space and functional residual capacity (FRC) were recorded, together with global and regional lung compliances and haemodynamic parameters. Values are mean±standard deviation (SD) and regression coefficients. Results: Endotoxinaemia increased the heterogeneity of ZQ but not ZV. Lung compliance progressively decreased with a ventral redistribution of ZV. A concomitant dorsal redistribution of ZQ resulted in mismatch of global (from ZV/ZQ 1.1±0.1 to 0.83±0.3) and notably dorsal (from ZV/ZQ 0.86±0.4 to 0.51±0.3) V and Q. Changes in global ZV/ZQ correlated with changes in the alveolar,arterial oxygen difference (r2=0.65, P<0.05), venous admixture (r2=0.66, P<0.05) and fractional alveolar dead space (r2=0.61, P<0.05). Decreased end-expiratory ZV correlated with decreased FRC (r2=0.74, P<0.05). Conclusions: EIT can be used to assess the heterogeneity of regional pulmonary ventilation and perfusion and V/Q matching during endotoxinaemic ALI, identifying pivotal pathophysiological changes. [source]

Monitoring of pacemaker induced changes in cardiac output with inspired to endtidal oxygen difference in paediatric cardiac surgery patients

PEDIATRIC ANESTHESIA, Issue 2 2001
Jan Bengtsson MD
Methods:,Fourteen children aged 4,15 months were studied after corrective cardiac surgery. Heart rate was increased by 20% with an external pacemaker. Cardiac output (CO) was measured with thermodilution. Oxygen saturation was measured in systemic artery (SaO2), central vein (ScvcO2) and pulmonary artery (SvO2). Inspiratory to endtidal oxygen difference (FI - ETO2) was measured using a paramagnetic technique. SvO2 was measured continuously using a spectrophotometric technique. Results:,CO increased in three patients and decreased in 11 patients during pacing. Regression between ,CO and ,(1/Sa-vO2), ,(FI - ETO2/Sa-vO2), ,(FI - ETO2/Sa-cvcO2) showed r=0.70, r=0.76 and r=0.75, respectively. ,CO exceeded 10% in 17 of 26 interventions. Changes in FI - ETO2 of equal direction as changes in CO occurred in 12 of these 17 interventions. Conclusions:,Estimations of CO changes, based on SvO2, can be enhanced if changes in FI - ETO2 are also measured. ScvcO2 instead of SvO2 gives equivalent results. Sudden changes in FI - ETO2 after pacemaker initiation or termination can predict the direction of CO changes. [source]

Cerebral oxygenation is reduced during hyperthermic exercise in humans

ACTA PHYSIOLOGICA, Issue 1 2010
P. Rasmussen
Abstract Aim:, Cerebral mitochondrial oxygen tension (PmitoO2) is elevated during moderate exercise, while it is reduced when exercise becomes strenuous, reflecting an elevated cerebral metabolic rate for oxygen (CMRO2) combined with hyperventilation-induced attenuation of cerebral blood flow (CBF). Heat stress challenges exercise capacity as expressed by increased rating of perceived exertion (RPE). Methods:, This study evaluated the effect of heat stress during exercise on PmitoO2 calculated based on a Kety-Schmidt-determined CBF and the arterial-to-jugular venous oxygen differences in eight males [27 ± 6 years (mean ± SD) and maximal oxygen uptake (VO2max) 63 ± 6 mL kg,1 min,1]. Results:, The CBF, CMRO2 and PmitoO2 remained stable during 1 h of moderate cycling (170 ± 11 W, ,50% of VO2max, RPE 9,12) in normothermia (core temperature of 37.8 ± 0.4 °C). In contrast, when hyperthermia was provoked by dressing the subjects in watertight clothing during exercise (core temperature 39.5 ± 0.2 °C), PmitoO2 declined by 4.8 ± 3.8 mmHg (P < 0.05 compared to normothermia) because CMRO2 increased by 8 ± 7% at the same time as CBF was reduced by 15 ± 13% (P < 0.05). During exercise with heat stress, RPE increased to 19 (19,20; P < 0.05); the RPE correlated inversely with PmitoO2 (r2 = 0.42, P < 0.05). Conclusion:, These data indicate that strenuous exercise in the heat lowers cerebral PmitoO2, and that exercise capacity in this condition may be dependent on maintained cerebral oxygenation. [source]