Arterial SO2 Research Articles

Reflection spectrophotometry (OxySat-2®) for monitoring oxygen saturation and hematocrit during extracorporeal circulation

Continuous measurement of sO2 and hematocrit during extracorporeal circulation has become feasible using reflection spectrophotometry. We have compared simultaneous measurements with in-line reflection spectrophotometry (OxySat-2® American Bent-ley), and in-vitro transmission spectrophotometry (OSM3 Hemoximeter® Radiometer) on discrete samples.In 8 patients undergoing open heart surgery during hypothermic extracorporeal circulation with hemodilution arterial and venous sO2 and hematocrit were measured continuous in-line in the extracorporeal circuit. Simultaneous and anaerobically collected blood samples were analyzed within one minute in the OSM3. The relationship between hemoglobin concentration (cHb) measured in the OSM3 and hematocrit (Hct) measured by the OxySat-2 was estimated from a mean cell hemoglobin concentration of 20 mmol·l-1, i.e. Hct (%) = 100 cHb/20.There was a systematic difference between the OxySat-2 and the reference method for sO 2</sb and cHb, the mean difference being: −2.4 s.d.2.8 ...

Pulse oximetry versus transcutaneouspO2in sick newborn infants

A pulse oximeter (Ohmeda Biox 3700) and two transcutaneous systems (Radiometer TCM3) were applied simultaneously to 18 newborn infants with respiratory insufficiency. All infants had either an umbilical catheter placed in the mid thoracic aorta or a radial artery catheter. The average monitoring time was 2 hours. Arterial blood pO2, pCO2 and pH (Radiometer ABL300), arterial sO2, HbCO and metHb (Radiometer OSM3), erythrocyte 2,3 DPG concentration, and fetal hemoglobin fraction (alkali denaturation kinetic method) were measured.Using arterial sO2 and pO2 as reference, the analytical bias of pulse oximetry (-0.5 ±1.0%, mean ± 1 SD) corresponded in magnitude, when coverted to pO2, to that of transcutaneous -pO2 (0.6 ±1.4 kPa for combined O2-CO2 electrode and -0.1 ±2.3 kPa for single O2 electrode). Transcutaneous pCO2 showed the smallest bias (0.3 ± 0.3 kPa). Both pulse oximetry and transcutaneous pO2 electrodes were good as trend monitors detecting rapid changes in the infants' oxygenation status. The pulse oximeter offers certain advantages in not requiring calibration or heating. The variations in the levels of fetal hemoglobin fraction (44 to 97 %), pH (7.27 to 7.49), pCO2 (3.3 to 6.8 kPa) and 2,3 diphosphoglycerate concentration (1.6 to 5.9 mmol/1) between the infants studied, resulted in a variable pO2-sO2 relation (p50 2.5 to 3.5 kPa). This presents difficulties in interpreting sO2 values in sick newborn infants, and we therefore recommend caution in using apulse oximeterto apply strict limits foravoiding hypoxia and hyperoxia in this population.

Pulse oximetry versus transcutaneous pO2 in sick newborn infants

A pulse oximeter (Ohmeda Biox 3700) and two transcutaneous systems (Radiometer TCM3) were applied simultaneously to 18 newborn infants with respiratory insufficiency. All infants had either an umbilical catheter placed in the mid thoracic aorta or a radial artery catheter. The average monitoring time was 2 hours. Arterial blood pO2, pCO2 and pH (Radiometer ABL300), arterial sO2, HbCO and metHb (Radiometer OSM3), erythrocyte 2,3 DPG concentration, and fetal hemoglobin fraction (alkali denaturation kinetic method) were measured. Using arterial sO2 and pO2 as reference, the analytical bias of pulse oximetry (-0.5 +/- 1.0%, mean +/- 1 SD) corresponded in magnitude, when converted to pO2, to that of transcutaneous - pO2 (0.6 +/- 1.4 kPa for combined O2-CO2 electrode and -0.1 +/- 2.3 kPa for single O2 electrode). Transcutaneous pCO2 showed the smallest bias (0.3 +/- 0.3 kPa). Both pulse oximetry and transcutaneous pO2 electrodes were good as trend monitors detecting rapid changes in the infants' oxygenation status. The pulse oximeter offers certain advantages in not requiring calibration or heating. The variations in the levels of fetal hemoglobin fraction (44 to 97%), pH (7.27 to 7.49), pCO2 (3.3 to 6.8 kPa) and 2,3 diphosphoglycerate concentration (1.6 to 5.9 mmol/l) between the infants studied, resulted in a variable pO2-sO2 relation (p50 2.5 to 3.5 kPa). This presents difficulties in interpreting sO2 values in sick newborn infants, and we therefore recommend caution in using a pulse oximeter to apply strict limits for avoiding hypoxia and hyperoxia in this population.

Myocardial oxygen supply during hypocapnia and hypercapnia in the dog.

It has been postulated that a coronary vasoconstriction during hypocapnia might be opposed by a compensating coronary vasodilatation due to impaired myocardial oxygen supply. The present study was performed first to examine whether a maximal decline in coronary sinus (CS) oxygen content was reached during hypocapnia. During hypercapnia a myocardial "over perfusion" has been demonstrated. The second purpose of the present study was to examine whether a myocardial "over perfusion" is essential to maintain a sufficient myocardial tissue oxygen supply during hypercapnia. Closed-chest dogs were anesthetized with pentobarbital and hypocapnia was induced by hyperventilation. Nitrogen gas and carbon dioxide could both be added to the inspiratory gas to create arterial hypoxemia (arterial SO2 65%) and hypercapnia, respectively. Arterial hypoxemia during hypocapnia increased myocardial blood flow (MBF) by 50%, while CS SO2 decreased significantly. The decrease in CS SO2 demonstrates a reserve capacity of myocardial oxygen extraction during hypocapnia, thereby ruling out any major coronary vasoconstriction during hypocapnia. Hypercapnia during normoxemia increased MBF, myocardial oxygen delivery, and CS SO2 substantially, but this was not observed when hypercapnia was created during arterial hypoxemia. From the present results we conclude that hypocapnia does not cause any major coronary vasoconstriction, while hypercapnia results in a myocardial "over perfusion," which is a luxury perfusion not essential to maintain sufficient myocardial oxygen supply during hypercapnia.

Effect of intermittent mandatory ventilation on respiratory drive and timing.

Seven patients receiving chronic ventilatory support were studied to better define the effects of intermittent mandatory ventilation (IMV) on the control and timing of spontaneous breathing between mandatory breaths. Each of these patients could sustain adequate spontaneous ventilation, as reflected by stable end-tidal carbon dioxide concentration (FETCO2), and arterial oxygen saturation (SO2) during periods of unassisted ventilation of sufficient duration to allow study. Inspiratory time (TI), respiratory cycle duration (Ttot), tidal volume (VT), and tracheal occlusion pressure (P0.1) were measured as IMV rate was progressively reduced. Respiratory timing was unaltered by decreasing IMV frequency; however, VT increased progressively. The P0.1 and mean inspiratory flow rate (VT/TI) also increased with each decrease in IMV rate, whereas FETCO2 and arterial SO2 remained constant. Thus, in these stable but ventilator-dependent patients, IMV did not alter respiratory timing or chemical stimuli, but it did alter respiratory drive as measured by VT/TI and P0.1.

Hemodynamic Effects of Intravenous Digoxin in Acute Myocardial Infarction.

Meeting Abstracts1 May 1972Hemodynamic Effects of Intravenous Digoxin in Acute Myocardial Infarction.Harry Lipp, M.B.B.S., Pablo Denes, M.D., Miguel Gambetta, M.D., Leon Resnekov, M.D.Harry Lipp, M.B.B.S.Search for more papers by this author, Pablo Denes, M.D.Search for more papers by this author, Miguel Gambetta, M.D.Search for more papers by this author, Leon Resnekov, M.D.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-76-5-865_4 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptEight patients with acute myocardial infarction, three not in failure and five in moderate or severe clinical or hemodynamic failure, were investigated after the intravenous administration of 0.5 to 0.75 mg digoxin. Mean aortic pressure (Ao), mean pulmonary arterial pressure (PA), left ventricular filling pressure (LVFP), cardiac index (CI), stroke index (SI), arterial PO2, pulmonary arterial oxygen saturation (pulmonary arterial So2), systemic vascular resistance (SVR), left ventricular stroke work index (LVSWI), left ventricular minute work index (LVMWI), and tension time index (TTI) were obtained before and 1 hour after intravenous digoxin. Patients in moderate or severe failure had significant changes... This content is PDF only. To continue reading please click on the PDF icon. Author, Article, and Disclosure InformationAuthors: Harry Lipp, M.B.B.S.; Pablo Denes, M.D.; Miguel Gambetta, M.D.; Leon Resnekov, M.D.Affiliations: Chicago, Ill. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetails Metrics 1 May 1972Volume 76, Issue 5Page: 865-866KeywordsAcute myocardial infarctionBlood pressureHemodynamicsOxygenPartial pressure of oxygenPulmonary arteryStrokeSystemic vascular resistance ePublished: 1 December 2008 Issue Published: 1 May 1972 PDF downloadLoading ...

41. Oxygen transport capacity in the neonatal period

The oxygen consumption of resting lambs in from 8 to 13 ml/min/kg during the 1st week of life. Assuming a cardiac output of 300 ml/min/kg and a hemoglobin of 13 g/100 ml, it may be seen that about one-third of the oxygen transport capacity is used at rest. In the present study lambs 2–7 days old were subjected to shivering during hypothermia. The animals were breathing 100% oxygen and were anesthetized with chloralose. Oxygen consumption, dye dilution curves, pressures of the central arteries, and arterial SO2 and acid-base balance values were registered. The oxygen consumption of the lambs increasd to a maximum of 35 ml/min/kg during shivering. Cardiac outputs increased from about 300 ml/min/kg to 500–700 ml/min/kg in the lambs with the highest values of oxygen consumption. The arterial oxygen saturation did not change at the cardiac output values. These results were also observed when the body temperature had been lowered to about 30°. About one-third of the oxygen carried by the arterial blood was extracted by the organism. Decreasing values of standard bicarbonate were often associated with lowered cardiac outputs. Correction of metabolic acidosis increased cardiac outputs but did not influence the oxygen consumptions. It may be concluded that shivering increases the oxygen consumption and cardiac output in the neonatal lambs. Metabolic acidosis conteracts teh cardiac response but does not influence the rate of oxygen consumption.