The Relation Between Oxygen Consumption and the Equilibrated Inspired Oxygen Fraction in an Anesthetic Circle Breathing System: A Mathematic Formulation & Laboratory Simulations

2008 ◽  
Vol 37 (1) ◽  
pp. 246-254
Author(s):  
Tsai-Hsin Chen ◽  
Chung-Han Hsin ◽  
Wen-Ru Ko ◽  
Cher-Ming Liou ◽  
Wei-Te Hung
Keyword(s):  
Oxygen Consumption ◽  
Breathing System ◽  
Laboratory Simulations ◽  
System A ◽  
Oxygen Fraction ◽  
Inspired Oxygen ◽  
Circle Breathing System

scholarly journals The Effect of Combined Hypoxemia and Cephalic Hypotension on Fetal Cerebral Blood Flow and Metabolism

1991 ◽  
Vol 11 (1) ◽  
pp. 99-105 ◽  
Author(s):  
A. Roger Hohimer ◽  
Conrad R. Chao ◽  
John M. Bissonnette
Keyword(s):  
Oxygen Consumption ◽  
Glucose Uptake ◽  
Glucose Utilization ◽  
Fetal Sheep ◽  
Oxygen Fraction ◽  
Arterial Blood ◽  
Arterial Blood Oxygen ◽  
Cerebral Vasodilation ◽  
Inspired Oxygen ◽  
Cerebral Vascular Resistance

The effect of hypoxemia and cephalic hypotension, alone and in combination, on hemispherical CBF and metabolism was examined in seven chronically catheterized fetal sheep. Hypoxemia was induced by lowering the maternal inspired oxygen fraction and cephalic hypotension was generated by partial occlusion of the fetal brachiocephalic artery. CBF was measured with radionuclide-labeled microspheres. During control, the arterial blood oxygen content (Cao2) was 3.2 ± 1.0 (SD) m M and CBF averaged 131 ± 21 (SD) ml min−1 100 g−1. The cephalic perfusion pressure (PP, mean cephalic arterial - sagittal venous) was 40 ± 4 mm Hg and cerebral vascular resistance (CVR, PP/CBF) was 0.31 ± 0.06 mm Hg ml−1 min 100 g. During induced hypoxemia, Cao2 was 1.4 ± 0.7 m M and CBF was elevated to 223 ± 60 ml min−1 100 g−1. PP was not different from control and CVR was lower at 0.19 ± 0.04 mm Hg ml−1 min 100 g, reflecting cerebral vasodilation. With cephalic hypotension alone (PP = 21 ± 4 mm Hg; Cao2 = 3.4 ± 0.9 m M), CBF fell to 83 ± 23 ml min−1 100 g−1 and there was no significant change in CVR (0.26 ± 0.05 mm Hg ml−1 min 100 g). During combined hypoxemia and hypotension (Cao2 = 1.5 ± 0.8 m M and PP = 18 ± 4 mm Hg), CBF was significantly greater than during hypotension alone (100 ± 6 ml min−1 100 g). CVR was 0.19 ± 0.05 mm Hg ml−1 min 100 g, identical to that measured in normotensive hypoxemia and significantly less than found during hypotension alone. Cerebral oxygen consumption was lower during combined hypoxemia and cephalic hypotension than during hypoxemia alone. Cerebral glucose uptake was significantly higher than control in both the hypoxemic and combined hypoxemic-hypotensive conditions. The glucose:oxygen quotient (6 × molar glucose uptake/molar oxygen consumption) was not different from unity during control or hypotension but was 2.31 ± 1.16 and 3.63 ± 1.99 during the hypoxemic and hypoxemic-hypotensive conditions, respectively, suggesting an anaerobic glucose utilization. No significant lactate efflux could be measured in any of these conditions.

scholarly journals The Effect of Neuromuscular Blockade on Oxygen Supply, Consumption, and Total Chest Compliance in Patients with High Oxygen Requirements Undergoing Mechanical Ventilation

2002 ◽  
Vol 30 (2) ◽  
pp. 192-197 ◽  
Author(s):  
W. C. Russell ◽  
R. Greer ◽  
N. J. N. Harper
Keyword(s):  
Mechanical Ventilation ◽  
Oxygen Consumption ◽  
Neuromuscular Blockade ◽  
Lung Compliance ◽  
Intensive Care Patients ◽  
Oxygen Fraction ◽  
Standard Level ◽  
Oxygen Requirements ◽  
Measure Oxygen Consumption ◽  
Inspired Oxygen

We investigated the effects of neuromuscular blockade with atracurium on oxygen consumption, oxygen delivery and total chest compliance in 20 sedated intensive care patients who required mechanical ventilation with an inspired oxygen fraction of at least 0.6. The reverse Fick method was used to measure oxygen consumption. Total chest compliance was measured from the ventilator pneumotachograph and pressure transducer. Measurements were made before neuromuscular blockade, at a standard level of neuromuscular blockade, and after demonstrated recovery of neuromuscular function. There was no statistical difference in any of the parameters measured. However there were large changes in oxygen consumption (range -35% to +17%) and total chest compliance (range -19.7% to +9.7%) in individuals. We conclude that in the setting of critical oxygenation, neuromuscular blockade cannot be assumed to reduce oxygen requirements or improve total lung compliance. If, however, neuromuscular blockade is selected as an adjunct to therapy, we recommend that the indices of oxygenation are calculated.

Lactate accumulation during incremental exercise with varied inspired oxygen fractions

1983 ◽  
Vol 55 (4) ◽  
pp. 1134-1140 ◽  
Author(s):  
M. C. Hogan ◽  
R. H. Cox ◽  
H. G. Welch
Keyword(s):  
Cycle Ergometer ◽  
Work Rate ◽  
O2 Uptake ◽  
Lactate Accumulation ◽  
Oxygen Fraction ◽  
Co2 Output ◽  
Break Points ◽  
Expired Gas ◽  
Gas Fractions ◽  
Inspired Oxygen

Six subjects pedaled a stationary cycle ergometer to exhaustion on three separate occasions while breathing gas mixtures of 17, 21, or 60% O2 in N2. Each subject rode for 3 min at work rates of 60, 90, 105 W, followed by 15-W increases every 3 min until exhaustion. Inspired and expired gas fractions, ventilation (V), heart rate, and blood lactate were measured. O2 uptake (VO2) and CO2 output (VCO2) were calculated for the last minute of each work rate; blood samples were drawn during the last 5 s. “Break points” for lactate, V, VCO2, V/VO2, and expired oxygen fraction (FEO2) were mathematically determined. VO2 was not significantly different at any work rate among the three different conditions. Nor did maximal VO2 differ significantly among the three treatments (P greater than 0.05). Lactate concentrations were significantly lower during hyperoxia and significantly higher during hypoxia compared with normoxia. Lactate values at exhaustion were not significantly different among the three treatments. Four subjects were able to work for a longer period of time during hyperoxic breathing. The variations in lactate accumulation as reported in this study cannot be explained on the basis of differences in VO2. The results of this research lend support to the hypothesis that differences in the performance of subjects breathing altered fractions of inspired oxygen may be caused by differences in lactate (or H+) accumulation.

scholarly journals Hematologic changes in propofol-anesthetized dogs with or without tramadol administration

2013 ◽  
Vol 65 (5) ◽  
pp. 1306-1312 ◽  
Author(s):  
P.F. Costa ◽  
N. Nunes ◽  
E.A. Belmonte ◽  
J.V. Moro ◽  
P.C.F. Lopes
Keyword(s):  
Blood Cells ◽  
Early Postoperative Period ◽  
Control Group ◽  
Anesthesia Induction ◽  
Monocyte Count ◽  
Mechanically Ventilated ◽  
Oxygen Fraction ◽  
Anesthetized Dogs ◽  
Inspired Oxygen ◽  
Rate Infusion

Drugs commonly used in anesthesia practice may significantly alter the oxidative state of blood cells. This mechanism could contribute to the immune suppression that occurs transiently in the early postoperative period. Thus, we assessed the effects of continuous rate infusion (CRI) of propofol associated or not with tramadol on hematologic parameters in dogs. Eight adult mongrel dogs were anesthetized on 2 occasions, 15 d apart. Two groups were formed: control group (CG) and tramadol group (GT). Propofol was used for induction (10mg kg-1) followed by a CRI (0.7mg kg-1minute-1). The animals were positioned in lateral recumbency and mechanically ventilated with inspired oxygen fraction of 0.6. In TG, tramadol (2mg kg-1) followed by a CRI (0.5mg kg-1minute-1) was administered in dogs. In the CG the sodium chloride (NaCl) solution at 0.9% was administered followed by its CRI, in the same volume that was used in TG. The measurement was taken before anesthesia induction (Tbasal), 30 minutes after induction (T0) and then at 30-minute intervals (T30 to T60). Red blood cells, hematocrit, hemoblogin concentration and total leukocytes count decreased from T0 in both groups. In TG, lymphocytes count at Tbasal [1.86 (0.82) x103µl-1] was greater than at T0, T30 and T60 [0.96(0.50), 0.92(0.48) and 0.95(0.48) x103µl-1, respectively]. No significant differences were observed for platelets neutrophil, eosinophil, basophil and monocyte count. In dogs, propofol-anesthesia associated or not with tramadol promoted decrease in blood cell count and should be used with caution in immunossupressed patients.

scholarly journals Systemic haemodynamic, renal perfusion and renal oxygenation responses to changes in inspired oxygen fraction during total intravenous or volatile anaesthesia

2020 ◽  
Vol 125 (2) ◽  
pp. 192-200 ◽  
Author(s):  
Naoya Iguchi ◽  
Junko Kosaka ◽  
Yoko Iguchi ◽  
Roger G. Evans ◽  
Rinaldo Bellomo ◽  
...  
Keyword(s):  
Renal Perfusion ◽  
Oxygen Fraction ◽  
Inspired Oxygen

Risks from Breathing Elevated Oxygen

2019 ◽  
Vol 90 (12) ◽  
pp. 1041-1049 ◽  
Author(s):  
Barbara E. Shykoff ◽  
Rees L. Lee
Keyword(s):  
Blood Pressure ◽  
Sea Level ◽  
Middle Ear ◽  
Paranasal Sinuses ◽  
Decompression Sickness ◽  
Oxygen Toxicity ◽  
Pressure Control ◽  
Small Airways ◽  
Oxygen Fraction ◽  
Inspired Oxygen

INTRODUCTION: Effects of breathing gas with elevated oxygen partial pressure (Po2) and/or elevated inspired oxygen fraction (FIo2) at sea level or higher is discussed. High FIo2 is associated with absorption problems in the lungs, middle ear, and paranasal sinuses, particularly if FIo2 > 80% and small airways, Eustachian tubes, or sinus passages are blocked. Absorption becomes faster as cabin altitude increases. Pulmonary oxygen toxicity and direct oxidative injuries, related to elevated Po2, are improbable in flight; no pulmonary oxygen toxicity has been found when Po2 < 55 kPa [418 Torr; 100% O2 higher than 15,000 ft (4570 m)]. Symptoms with Po2 of 75 kPa [520 Torr; 100% O2 at 10,000 ft (3050 m)] were reported after 24 h and the earliest signs at Po2 of 100 kPa (760 Torr, 100% O2 at sea level) occurred after 6 h. However, treatment for decompression sickness entails a risk of pulmonary oxygen toxicity. Elevated Po2 also constricts blood vessels, changes blood pressure control, and reduces the response to low blood sugar. With healthy lungs, gas transport and oxygen delivery are not improved by increasing Po2. Near zero humidity of the breathing gas in which oxygen is delivered may predispose susceptible individuals to bronchoconstriction.Shykoff BE, Lee RL. Risks from breathing elevated oxygen. Aerosp Med Hum Perform. 2019; 90(12):1041–1049.

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