The effect of the inspired oxygen fraction on arterial blood oxygenation in spontaneously breathing, isoflurane anaesthetized horses: a retrospective study

2015 ◽  
Vol 42 (3) ◽  
pp. 280-285 ◽  
Author(s):  
Stijn Schauvliege ◽  
Ioannis Savvas ◽  
Frank Gasthuys
Keyword(s):  
Retrospective Study ◽  
Blood Oxygenation ◽  
Oxygen Fraction ◽  
Arterial Blood ◽  
Spontaneously Breathing ◽  
Inspired Oxygen

scholarly journals Clinical study of the effect of inspired oxygen fraction and type of surgery on pulmonary venous admixture, in isoflurane-anaesthetised, spontaneously breathing dogs

2017 ◽  
Author(s):  
Αλεξία-Σουλτάνα Μπουργαζλή
Keyword(s):  
Clinical Study ◽  
Venous Admixture ◽  
Oxygen Fraction ◽  
Spontaneously Breathing ◽  
Inspired Oxygen ◽  
Type Of Surgery

Στον άνθρωπο, ασθενείς με φυσιολογικούς πνεύμονες πριν την αναισθησία, ενδέχεται, κατά τη διάρκεια αυτής να εμφανίσουν μειωμένη ικανότητα οξυγόνωσης του αίματος. Η ανισοκατανομή αερισμού-αιμάτωσης (V/Q) είναι αποτέλεσμα της πρόσμειξης οξυγονωμένου αρτηριακού αίματος με φλεβικό αίμα της πνευμονικής κυκλοφορίας. Οι στόχοι της διατριβής ήταν να γίνει σύγκριση της επίδρασης δύο συγκεντρώσεων εισπνεόμενου οξυγόνου (FiΟ2), 1,0 και 0,4, καθώς και η επίδραση του χειρουργικού τραύματος μη ενδοκοιλιακών σε σύγκριση με αυτή των ενδοκοιλιακών επεμβάσεων, στον αερισμό των πνευμόνων και στην ανταλλαγή αερίων σε σκύλους, οι οποίοι βρίσκονται υπό γενική αναισθησία με ισοφλουράνιο, έχουν αυτόματη αναπνοή για μη ενδοθωρακικές χειρουργικές επεμβάσεις. Οι υποθέσεις οι οποίες εξετάστηκαν ήταν: 1) Η χορήγηση υψηλού FiO2 θα οδηγούσε σε μεγαλύτερη διαταραχή του αερισμού των πνευμόνων και της ανταλλαγής αερίων, δηλαδή σε μεγαλύτερη διαταραχή του λόγου V/Q, σε σύγκριση με τη χορήγηση χαμηλότερου FiΟ2 και 2) Η ενδοκοιλιακή χειρουργική επέμβαση θα συνέβαλε σε μεγαλύτερο βαθμό στην αύξηση της διαταραχής του λόγου V/Q σε σχέση με τη μη ενδοκοιλιακή χειρουργική επέμβαση. Εβδομήντα σκύλοι συμπεριλήφθηκαν στη μελέτη, ηλικίας 1-10 ετών, βάρους 7-50 kg, κλινικά υγιείς για μη ενδοθωρακικές χειρουργικές επεμβάσεις. Η προνάρκωση περιελάμβανε την ενδομυϊκή χορήγηση δεξμεδετομιδίνης μαζί με μορφίνη. Σε κάθε ζώο καθετηριάστηκαν η ραχιαία μετατάρσια αρτηρία και η πνευμονική αρτηρία για λήψη δειγμάτων αρτηριακού και μεικτού φλεβικού αίματος αντίστοιχα. Η εγκατάσταση της αναισθησίας έγινε με προποφόλη και η διατήρησή της με ισοφλουράνιο σε 100% ή σε 40% οξυγόνο. Τα ζώα κατανεμήθηκαν τυχαία σε τέσσερις ομάδες, οι οποίες διέφεραν ως προς το ποσοστό του FiO2 στο μείγμα αερίου και ως προς το είδος της χειρουργικής επέμβασης (μη ενδοκοιλιακή/ενδοκοιλιακή). Έγινε ταυτόχρονη αναερόβια λήψη ηπαρινισμένων δειγμάτων αρτηριακού και μεικτού φλεβικού αίματος σε διάφορες χρονικές στιγμές. Το ενδοπνευμονικό shunt (venous admixture, Qs/Qt) υπολογίσθηκε σε όλες τις παραπάνω χρονικές στιγμές. Οι δύο ομάδες των ζώων με βάση τη συγκέντρωση του FiO2 διέφεραν ως προς το Qs/Qt στατιστικώς σημαντικά (p=0,003). Το shunt για την ομάδα με 0,4 FiO2 ήταν 11 ± 4,1%, ενώ για την ομάδα με 1,0 FiO2 ήταν 7,9 ± 3,9%. Δεν παρατηρήθηκε στατιστικά σημαντική διαφορά ανάμεσα στις ομάδες με βάση το είδος της χειρουργικής επέμβασης (μη ενδοκοιλιακή-ενδοκοιλιακή) ως προς το shunt, αλλά ούτε προς κάποια άλλη μεταβλητή. Στατιστικά σημαντική διαφορά παρατηρήθηκε ως προς την αλληλεπίδραση του FiO2 και του είδους της χειρουργικής επέμβασης στον όγκο αναπνοής ανά κιλό σωματικού βάρους (p=0,018). Συμπερασματικά, Η χορήγηση μέγιστης συγκέντρωσης FiO2 (1,0) δεν οδηγεί σε μεγαλύτερη ανισοκατανομή V/Q, όπως αναμενόταν, σε σύγκριση με τη χρήση χαμηλότερης συγκέντρωσης FiO2 (0,4), σε σκύλους υπό γενική αναισθησία με αυτόματη αναπνοή. Η ενδοκοιλιακή χειρουργική επέμβαση φάνηκε να μην έχει καμία επίδραση στην αύξηση της ανισοκατανομής του V/Q σε σύγκριση με τη μη ενδοκοιλιακή επέμβαση.

Effect of acute hypoxia on microcirculatory and tissue oxygen levels in rat cremaster muscle

2005 ◽  
Vol 98 (4) ◽  
pp. 1177-1184 ◽  
Author(s):  
Paul C. Johnson ◽  
Kim Vandegriff ◽  
Amy G. Tsai ◽  
Marcos Intaglietta
Keyword(s):  
Acute Hypoxia ◽  
Hypoxic Exposure ◽  
Cremaster Muscle ◽  
Tissue Oxygen ◽  
Oxygen Levels ◽  
Oxygen Fraction ◽  
Arterial Blood ◽  
S Period ◽  
Inspired Oxygen

Repeated exposure to brief periods of hypoxia leads to pathophysiological changes in experimental animals similar to those seen in sleep apnea. To determine the effects of such exposure on oxygen levels in vivo, we used an optical method to measure Po2 in microcirculatory vessels and tissue of the rat cremaster muscle during a 1-min step reduction of inspired oxygen fraction from 0.21 to 0.07. Under control conditions, Po2 was 98.1 ± 1.9 Torr in arterial blood, 52.2 ± 2.8 Torr in 29.0 ± 2.7-μm arterioles, 26.8 ± 1.7 Torr in the tissue interstitium near venous capillaries, and 35.1 ± 2.6 Torr in 29.7 ± 1.9-μm venules. The initial fall in Po2 during hypoxia was significantly greater in arterial blood, being 93% complete in the first 10 s, whereas it was 68% complete in arterioles, 47% at the tissue sites, and 38% in venules. In the 10- to 30-s period, the fall in normalized tissue and venular Po2 was significantly greater than in arterial Po2. At the end of hypoxic exposure, Po2 at all measurement sites had fallen very nearly in proportion to that in the inspired gas, but tissue oxygen levels did not reach critical Po2. Significant differences in oxyhemoglobin desaturation rate were also observed between arterial and microcirculatory vessels during hypoxia. In conclusion, the fall in microcirculatory and tissue oxygen levels in resting skeletal muscle is significantly slower than in arterial blood during a step reduction to an inspired oxygen fraction of 0.07, and tissue Po2 does not reach anaerobic levels.

scholarly journals Prone position in wards for spontaneous breathing Covid-19 patients: a retrospective study.

2020 ◽  
Author(s):  
Johan Wormser ◽  
Christophe Romanet ◽  
François Philippart
Keyword(s):  
Retrospective Study ◽  
Adverse Events ◽  
Prone Position ◽  
Primary Outcome ◽  
Length Of Hospital Stay ◽  
Prone Positioning ◽  
Oxygen Fraction ◽  
Poor Tolerance ◽  
Secondary Outcomes ◽  
Inspired Oxygen

Abstract The pandemic of coronavirus disease 2019 (Covid-19) caused a large number of non-ventilated hypoxemic patients to require the use of prone position. The aim of this study is to measure the efficiency and tolerance of prone positioning in ward hypoxemic patients treated for Covid-19. This retrospective study included confirmed Covid-19 hypoxemic patients treated by at least one prone position session. Primary outcome was pulse oximetry over inspired oxygen fraction ratio (SpO2/FiO2) before, during and after prone position. Secondary outcomes were failure, adverse events and poor tolerance rate. Twenty-seven patients were included. During first, second and third sessions, SpO2/FiO2 ratio was significantly higher during posture than before (p<0.0001, p<0.01 and p<0.01 respectively). Eighteen patients were responders (defined as an improvement of SpO2/FiO2 of more than 50) during the first posture and have a shorter length of hospital stay than non-responders patients. Failure rate was 5 %, poor tolerance and adverse events rates were 8 % and 7 % respectively. Our study found that prone position in wards improved alveolar exchange during posture and is well-tolerated. This technique could be used in any medical ward.

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.

Normalization of experimental results with respect to inlet conditions in membrane oxygenator testing

Perfusion ◽  
1996 ◽  
Vol 11 (1) ◽  
pp. 45-51 ◽  
Author(s):  
ML Costantino ◽  
GB Fiore
Keyword(s):  
Blood Flow Rate ◽  
Normalization Procedure ◽  
Membrane Oxygenator ◽  
Oxygen Fraction ◽  
Arterial Blood ◽  
Numerical Computing ◽  
Inlet Conditions ◽  
Inspired Oxygen ◽  
Oxyhaemoglobin Saturation

This study looked at the problem of the excessive variability in oxygenator testing results, induced by variation of inlet parameters, particularly of inlet oxyhaemoglobin saturation. The investigation was carried out in the laboratory. An in vitro circuit was used to perfuse a small oxygenating cell. Blood flow rate (BFR) and film thickness (BFT) were varied to obtain different oxygenation conditions, while the inspired oxygen fraction (FiO 2) and ventilation ratio were kept at constant values. With each test condition, inlet saturation was varied in the range 60-70% and a number of veno-arterial blood samples (at least 20) were withdrawn and analysed for numerical computing and statistical analysis. The generic law relating oxygenation increment to inlet saturation was found. This allowed a useful normalization procedure to be applied to oxygenator testing results and render them comparable, even if obtained at different inlet conditions.

Oxygen Fraction Adjustment According to Body Surface Area during Extracorporeal Circulation

2015 ◽  
Vol 18 (3) ◽  
pp. 098
Author(s):  
Cem Arıtürk ◽  
Serpil Ustalar Özgen ◽  
Behiç Danışan ◽  
Hasan Karabulut ◽  
Fevzi Toraman
Keyword(s):  
Body Temperature ◽  
Surface Area ◽  
Body Surface Area ◽  
Body Surface ◽  
Extracorporeal Circulation ◽  
Group Iii ◽  
Oxygen Fraction ◽  
Arterial Blood ◽  
Group I ◽  
Group Ii

<p class="p1"><span class="s1"><strong>Background:</strong> The inspiratory oxygen fraction (FiO<sub>2</sub>) is usually set between 60% and 100% during conventional extracorporeal circulation (ECC). However, this strategy causes partial oxygen pressure (PaO<sub>2</sub>) to reach hyperoxemic levels (&gt;180 mmHg). During anesthetic management of cardiothoracic surgery it is important to keep PaO<sub>2</sub> levels between 80-180 mmHg. The aim of this study was to assess whether adjusting FiO<sub>2</sub> levels in accordance with body temperature and body surface area (BSA) during ECC is an effective method for maintaining normoxemic PaO<sub>2</sub> during cardiac surgery.</span></p><p class="p1"><span class="s1"><strong>Methods:</strong> After approval from the Ethics Committee of the University of Acıbadem, informed consent was given from 60 patients. FiO<sub>2</sub> adjustment strategies applied to the patients in the groups were as follows: FiO<sub>2</sub> levels were set as 0.21 × BSA during hypothermia and 0.21 × BSA + 10 during rewarming in Group I; 0.18 × BSA during hypothermia and 0.18 × BSA + 15 during rewarming in Group II; and 0.18 × BSA during hypothermia and variable with body temperature during rewarming in Group III. Arterial blood gas values and hemodynamic parameters were recorded before ECC (T1); at the 10th minute of cross clamp (T2); when the esophageal temperature (OT) reached 34°C (T3); when OT reached 36°C (T4); and just before the cessation of ECC (T5).</span></p><p class="p1"><span class="s1"><strong>Results:</strong> Mean PaO<sub>2</sub> was significantly higher in Group I than in Group II at T2 and T3 (<em>P</em> = .0001 and <em>P</em> = .0001, respectively); in Group I than in Group III at T1 (<em>P</em> = .02); and in Group II than in Group III at T2, T3, and T4 <br /> (<em>P</em> = .0001 for all). </span></p><p class="p1"><span class="s1"><strong>Conclusion: </strong>Adjustment of FiO<sub>2</sub> according to BSA rather than keeping it at a constant level is more appropriate for keeping PaO<sub>2</sub> between safe level limits. However, since oxygen consumption of cells vary with body temperature, it would be appropriate to set FiO<sub>2</sub> levels in concordance with the body temperature in the <br /> rewarming period.</span></p>

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