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Systemic Oxygen Delivery (systemic + oxygen_delivery)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Deceptive simplicity: Systemic oxygen delivery and pulse oximetry

JOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 7-8 2007
Clare L Collins
Abstract: Pulse oximetry is often perceived to be a measure of the adequacy of oxygen delivery. It is, however, only a measure of oxygen bound to haemoglobin. Systemic oxygen delivery is principally determined by cardiac output, haemoglobin concentration and haemoglobin saturation. Changes to both cardiac output and haemoglobin concentration will significantly alter oxygen delivery without changing oxygen saturation. This article will describe the components of systemic oxygen delivery and the physiologic limitation of pulse oximetry and caution against over-interpretation of oximetry in the care of newborns. [source]

A simple method to reduce the inspiratory oxygen fraction for high pulmonary blood flow patients in an operating room

PEDIATRIC ANESTHESIA, Issue 12 2007
AYAKO ASAKURA MD
Summary Background:, Low inspired oxygen acutely increases pulmonary vascular resistance and decreases pulmonary-systemic blood flow ratio. We present a simple method to lower inspired oxygen fraction (FIO2 < 0.21) without supplemental nitrogen, during mechanical ventilation by an anesthesia machine. Methods:, After institutional approval, seven healthy adult volunteers and three infants (0,12 month old) scheduled for congenital heart surgery were enrolled in this study. All the infants were diagnosed with congestive heart failure because of high pulmonary blood flow and were thought to benefit from low FIO2. The volunteers performed spontaneous ventilation (fresh air flow rate = 10 l·min,1, tidal volume = 600 ml, frequency = 10 br·min,1). The infants were mechanically ventilated with air (fresh air flow rate = 6 l·min,1, tidal volume = 10 ml·kg,1, 15 < frequency < 30 br·min,1 to adjust PaCO2 between 5.8 kPa and 6.5 kPa (45,50 mmHg), after induction of general anesthesia and tracheal intubation. The fresh gas flow rates were determined by the following formula. Fresh gas flow rate = (FIO2 , FEO2) EVE/(0.21 + FIO2 , FEO2 , target FIO2). We recorded FIO2 every 5 min for 30 min. When arterial oxygen saturation decreased >15%, fresh gas flow rates were increased to adjust FIO2 to 0.21. Results:, In all of the seven volunteers and three infants target FIO2 was achieved in <10 min. FIO2 was kept at 0.18 ± 0.01 (SD) by calculated fresh air flow rates. In one infant, SpO2 decreased >15% 20 min after lowering FIO2, we had to discontinue this study, and increase fresh gas flow to ventilate the infant with FIO2 0.21. In the other two infants, FIO2 was maintained throughout the study. Conclusions:, This simple and convenient method to decrease FIO2, has a utility in clinical situations, in which pulmonary vascular resistance is to be increased to improve systemic oxygen delivery in patients with high pulmonary blood flow during cardiac surgery. [source]

Haemodynamic responses to exercise, ATP infusion and thigh compression in humans: insight into the role of muscle mechanisms on cardiovascular function

THE JOURNAL OF PHYSIOLOGY, Issue 9 2008
José González-Alonso
The muscle pump and muscle vasodilatory mechanims are thought to play important roles in increasing and maintaining muscle perfusion and cardiac output during exercise, but their actual contributions remain uncertain. To evaluate the role of the skeletal muscle pump and vasodilatation on cardiovascular function during exercise, we determined leg and systemic haemodynamic responses in healthy men during (1) incremental one-legged knee-extensor exercise, (2) step-wise femoral artery ATP infusion at rest, (3) passive exercise (n= 10), (4) femoral vein or artery ATP infusion (n= 6), and (5) cyclic thigh compressions at rest and during passive and voluntary exercise (n= 7). Incremental exercise resulted in progressive increases in leg blood flow (,LBF 7.4 ± 0.7 l min,1), cardiac output ( 8.7 ± 0.7 l min,1), mean arterial pressure (,MAP 51 ± 5 mmHg), and leg and systemic oxygen delivery and . Arterial ATP infusion resulted in similar increases in , LBF, and systemic and leg oxygen delivery, but central venous pressure and muscle metabolism remained unchanged and MAP was reduced. In contrast, femoral vein ATP infusion did not alter LBF, or MAP. Passive exercise also increased blood flow (,LBF 0.7 ± 0.1 l min,1), yet the increase in muscle and systemic perfusion, unrelated to elevations in aerobic metabolism, accounted only for ,5% of peak exercise hyperaemia. Likewise, thigh compressions alone or in combination with passive exercise increased blood flow (,LBF 0.5,0.7 l min,1) without altering , MAP or . These findings suggest that the skeletal muscle pump is not obligatory for sustaining venous return, central venous pressure, stroke volume and or maintaining muscle blood flow during one-legged exercise in humans. Further, its contribution to muscle and systemic peak exercise hyperaemia appears to be minimal in comparison to the effects of muscle vasodilatation. [source]