High Inspired Oxygen Concentrations Research Articles

Haemodynamic effects of a 10-min treatment with a high inspired oxygen concentration in the emergency department: a prospective observational study

Previous studies show that prolonged exposure to a high inspired oxygen concentration (FiO2) is associated with unfavourable haemodynamic effects. Until now, it is unknown if similar effects also occur after...

Redefining exchange of tracheal tube from nasal to oral in high risk sepsis patient

A 35-year-old male weighing 94 kg developed significant oropharyngeal and perilaryngeal oedema with sepsis in the postoperative period following mandibular advancement surgery. He needed change of an existing nasotracheal tube to the orotracheal route in the intensive care unit (ICU). The procedure had to be abandoned in the ICU for fear of losing the airway in this patient requiring high inspired oxygen concentration of 60% and positive end expiratory pressure of 8.0 cm H2O. The changeover of tube was safely achieved in the operation theatre by utilising the splinting effect of the existing nasotracheal tube that helped to keep the oedematous epiglottis lifted while an airway exchange catheter (AEC) was placed by its side under videolaryngoscopic guidance. Railroading the new orotracheal tube over the preplaced AEC after withdrawing the nasal tube while receiving oxygen at 4 litres per minute helped to accomplish the safe exchange of the tracheal tube.

The outcomes of using high oxygen concentration in pediatric patients.

Oxygen reserve index, available as part of Masimo Rainbow SET pulse oximetry, is a noninvasive and continuous variable intended to provide insight into a patient's oxygen status in the moderate hyperoxic range (PaO2 > 100 and ≤ 200mm Hg), defined as a patient's oxygen "reserve". When used in conjunction with pulse oximetry, ORi extends the knowledge on a patient's oxygen status providing clinically important information helping to prevent hyperoxemia and hypoxemia. There are limited data on patients undergoing craniosynostosis surgery. Our primary goal was to evaluate the effects of different concentrations of inspiratory oxygen (FiO2) on patient oxygenation status by monitoring ORi. Thirty patients scheduled for craniosynostosis were included in this observational cohort study. Patients were randomized into two equal groups: Group 1 received a fraction of inspired oxygen of 0.8 and group 2 received a FiO2 of 0.6 during induction of anaesthesia. In addition to standard haemodynamic variables with ORi were recorded at baseline 1min, 5min, 60min, and 120min after intubation. Postoperative complications, length of stay in the intensive care unit and hospital were recorded. In total, 14 patients were evaluated in each group. Gender, age, BMI, ASA scores were similar between groups (p > 0.05). In Group 1, ORi values were significantly higher when compared to group 2 at baseline (0.86 ± 0.21 vs 0.45 ± 0.32, p = 0.001), one minute (0.61 ± 0.24 vs 0.27 ± 0.21, p = 0.001), and 5min (0.34 ± 0.31 vs 0.10 ± 0.13, p = 0.033). High inspired oxygen concentration during induction of anesthesia in pediatric patients is associated with higher levels of ORi. Therefore, ORi may provide the means to safely reduce the inspired oxygen fraction during inhalational induction in paediatric patients.

Anesthetic Management Using Low Fraction of Inspiratory Oxygen for Living Donor Liver Transplantation in a Patient With Hepatopulmonary Syndrome Complicated by Interstitial Pneumonia: A Case Report

Hepatopulmonary syndrome frequently complicates end-stage liver disease. It causes hypoxemia and requires oxygen administration. Additionally, interstitial pneumonia causes hypoxemia; however, it is known to be aggravated by high-concentration oxygen administration. A 71-year-old woman with hepatopulmonary syndrome and interstitial pneumonia underwent living donor liver transplantation, requiring conflicting management in terms of the inspiratory oxygen concentration. We achieved a low intraoperative fraction of inspiratory oxygen by increasing the cardiac output with intravenous catecholamines. As a result, the transplanted liver functioned well postoperatively, and the patient was discharged without exacerbation of the interstitial pneumonia. We suggest that patients with hepatopulmonary syndrome complicated with interstitial pneumonia can undergo successful living donor liver transplantation without the use of high inspiratory oxygen concentration by using catecholamines to maintain a high mixed venous oxygen saturation.

Differential Response of Pentanal and Hexanal Exhalation to Supplemental Oxygen and Mechanical Ventilation in Rats.

High inspired oxygen during mechanical ventilation may influence the exhalation of the previously proposed breath biomarkers pentanal and hexanal, and additionally induce systemic inflammation. We therefore investigated the effect of various concentrations of inspired oxygen on pentanal and hexanal exhalation and serum interleukin concentrations in 30 Sprague Dawley rats mechanically ventilated with 30, 60, or 93% inspired oxygen for 12 h. Pentanal exhalation did not differ as a function of inspired oxygen but increased by an average of 0.4 (95%CI: 0.3; 0.5) ppb per hour, with concentrations doubling from 3.8 (IQR: 2.8; 5.1) ppb at baseline to 7.3 (IQR: 5.0; 10.8) ppb after 12 h. Hexanal exhalation was slightly higher at 93% of inspired oxygen with an average difference of 0.09 (95%CI: 0.002; 0.172) ppb compared to 30%. Serum IL-6 did not differ by inspired oxygen, whereas IL-10 at 60% and 93% of inspired oxygen was greater than with 30%. Both interleukins increased over 12 h of mechanical ventilation at all oxygen concentrations. Mechanical ventilation at high inspired oxygen promotes pulmonary lipid peroxidation and systemic inflammation. However, the response of pentanal and hexanal exhalation varies, with pentanal increasing by mechanical ventilation, whereas hexanal increases by high inspired oxygen concentrations.

Relationship between a High-inspired Oxygen Concentration and Dorsal Atelectasis in High-energy Trauma Patients.

We performed a retrospective cohort study of 911 high-energy trauma patients who underwent chest CT scans at least twice after admission. We hypothesized that in high-energy trauma patients, a high-inspired oxygen concentration delivered after admission results in dorsal atelectasis. The study's primary outcome was dorsal atelectasis formation diagnosed based on CT images. We defined dorsal atelectasis as the presence of atelectasis at ≥ 10 mm thick on CT images. We defined high-inspired oxygen concentration as >60% oxygen delivered between two CT scans. Four hundred sixty-five patients (51.0%) developed atelectasis according to the second CT scan, and 338 (37.1%) received a high-inspired oxygen concentration. A univariate analysis showed that the rate of the high-inspired oxygen concentration in the atelectasis group was significantly higher than that in the non-atelectasis group (43.4% vs. 30.1%, p<0.001). However, a logistic regression analysis showed that there was no significant relationship between the oxygen concentration and the formation of dorsal atelectasis (OR: 1.197, 95%CI: 0.852-1.683, p=0.30). Age, the Injury Severity Score, BMI, and smoking were found to be risk factors of dorsal atelectasis formation in high-energy trauma patients. There was no relationship between the oxygen concentration and atelectasis formation in our series of high-energy trauma patients.

Hyperoxia and antioxidants during major non-cardiac surgery and risk of cardiovascular events: Protocol for a 2×2 factorial randomised clinical trial.

Myocardial injury after non-cardiac surgery occurs in a high number of patients, resulting in increased mortality in the post-operative period. The use of high inspiratory oxygen concentrations may cause hyperoxia, which is associated with impairment of coronary blood flow. Furthermore, the surgical stress response increases reactive oxygen species, which is involved in several perioperative complications including myocardial injury and death. Avoidance of hyperoxia and substitution of reactive oxygen species scavengers may be beneficial. Our primary objectiveis to examine the effect of oxygen and added antioxidants for prevention of myocardial injury assessed by area under the curve for troponin measurements during the first three post-operative days. The VIXIE trial (VitamIn and oXygen Interventions and cardiovascular Events) is an investigator-initiated, blinded, 2×2 factorial multicentre clinical trial. We include 600 patients with cardiovascular risk factors undergoing major non-cardiac surgery. Participants are randomised to an inspiratory oxygen fraction of 0.80 or 0.30 during and for 2hours after surgery and either an intravenous bolus of vitamin C and an infusion of N-acetylcysteine or matching placebo of both. The primary outcome is the area under the curve for high-sensitive cardiac troponin release during the first three post-operative days as a marker of the extent of myocardial injury. Secondary outcomes are mortality, non-fatal myocardial infarction and non-fatal serious adverse events within 30days. The current trial will provide further evidence for clinicians on optimal administration of perioperative oxygen in surgical patients with cardiovascular risks and the clinical effects of two common antioxidants.

Perfluorocarbons: Knowledge Gained From Clinical Trials.

Research into potential use of perfluorocarbons for liquid ventilation and as oxygen delivery agents in humans has been underway since the 1960s. While partial liquid ventilation with perfluorocarbons showed promise in animal models and early human investigation, randomized controlled human trials failed to show benefit and an elevated rate of adverse events. Initial approval of Fluosol-DA (Green Cross Corporation, Osaka, Japan) by the United States Food and Drug Administration as an oxygen delivery agent for use in high-risk coronary angioplasty represents the only approved application of these compounds to supplement tissue oxygenation, but the compound was rendered obsolete and removed from the market with the development of advanced angioplasty catheters in the 1990s. Second-generation perfluorocarbons were developed with a higher capacity to increase the amount of oxygen dissolved in the fluid phase of blood. Early clinical trials of perflubron emulsion in non-cardiac and cardiac surgery were promising, but dose restriction and the requirement for high inspired oxygen concentration to maximize oxygen delivery for prolonged periods of time limited the clinical utility as a replacement for the oxygen carrying capacity of red blood cells. Identification of excess serious adverse events in treated patients resulted in discontinuation of pivotal clinical trials. Continued research investigating different formulations of perfluorocarbons has shown promise in animal studies, but continued research is necessary to prove safety and efficacy in humans.

Perioperative respiratory complications: current evidence and strategy discussed in 2017 JA symposium.

Respiratory management during general anesthesia aims to safely secure the airway and maintain adequate ventilation to deliver oxygen to the vital organs, maintaining homeostasis even during surgery. Despite its clinical importance, anesthesiologists often encounter difficulties in properly managing respiration during the perioperative period, leading to severe respiratory complications. In this year's JA symposium, 5 editorial board members of Journal of Anesthesia (JA) who are experts in the field of respiratory management in anesthesia discussed the following topics: quitting smoking before surgery: exposure to passive smoke is damaging to children, ventilator-associated pneumonia, high inspiratory oxygen concentration and lung injury, aspiration pneumonia, and postoperative respiratory management strategy in patients with obstructive sleep apnea. We hope that this special article regarding this year's JA symposium may be useful for JA readers to manage clinical anesthesia on a daily basis.

Managing Persistent Hypoxemia: what is new?

Mechanical ventilation is the standard life-support technique for patients with severe acute respiratory failure. However, some patients develop persistent and refractory hypoxemia because their lungs are so severely damaged that they are unable to respond to the application of high inspired oxygen concentration and high levels of positive end-expiratory pressure. In this article, we review current knowledge on managing persistent hypoxemia in patients with injured lungs.

Effect of High Inspiratory Oxygen Fraction on Endothelial Function in Healthy Volunteers: A Randomized Controlled Crossover Pilot Study.

It has been suggested that high inspiratory oxygen concentrations during anesthesia may be associated with higher postoperative mortality due to endothelial dysfunction. A randomized controlled crossover study was conducted with 25 healthy male volunteers. They inhaled an oxygen concentration of 30% and 80%. The endothelial function was assessed using noninvasive digital pulse amplitude tonometry (EndoPAT) supported by endothelial biomarkers. The difference in endothelial function between the 2 treatments was 0.05 (95% confidence interval, -0.36 to 0.27; P = .77). Endothelial biomarkers were unaffected. Inhalation of a high oxygen fraction in healthy volunteers did not result in a significant reduction of endothelial function.

Hyperoxia Reduces Oxygen Consumption in Children with Pulmonary Hypertension.

High inspired oxygen concentration (FiO2 > 0.85) is administered to test pulmonary vascular reactivity in children with pulmonary hypertension (PH). It is difficult to measure oxygen consumption (VO2) if the subject is breathing a hyperoxic gas mixture so the assumption is made that baseline VO2 does not change. We hypothesized that hyperoxia changes VO2. We sought to compare the VO2 measured by a thermodilution catheter in room air and hyperoxia. A retrospective review of the hemodynamic data obtained in children with PH who underwent cardiac catheterization was conducted between 2009 and 2014. Cardiac index (CI) was measured by a thermodilution catheter in room air and hyperoxia. VO2 was calculated using the equation CI = VO2/arterial-venous oxygen content difference. Data were available in 24 subjects (males = 10), with median age 8.3years (0.8-17.6years), weight 23.3kg (7.5-95kg), and body surface area 0.9m2 (0.4-2.0m2). In hyperoxia compared with room air, we measured decreased VO2 (154 ± 38 to 136 ± 34ml/min/m2, p = 0.007), heart rate (91 [Formula: see text] 20 to 83 [Formula: see text] 21 beats/minute, p=0.005), mean pulmonary artery pressure (41 [Formula: see text] 16 to 35 [Formula: see text] 14 mmHg, p=0.024), CI (3.6 [Formula: see text] 0.8 to 3.3 [Formula: see text] 0.9L/min/m2, p = 0.03), pulmonary vascular resistance (9 [Formula: see text] 6 to 7 [Formula: see text] 3WUm2, p = 0.029), increased mean aortic (61 [Formula: see text] 11 to 67 [Formula: see text] 11mmHg, p = 0.005), pulmonary artery wedge pressures (11 [Formula: see text] 8 to 13 [Formula: see text] 9mmHg, p = 0.006), and systemic vascular resistance (12 [Formula: see text] 6 to 20 [Formula: see text] 7WUm2, p=0.001). Hyperoxia decreased VO2 and CI and caused pulmonary vasodilation and systemic vasoconstriction in children with PH. The assumption that VO2 remains unchanged in hyperoxia may be incorrect and, if the Fick equation is used, may lead to an overestimation of pulmonary blood flow and underestimation of PVRI.

Vagal denervation inhibits the increase in pulmonary blood flow during partial lung aeration at birth.

Lung aeration at birth significantly increases pulmonary blood flow, which is unrelated to increased oxygenation or other spatial relationships that match ventilation to perfusion. Using simultaneous X-ray imaging and angiography in near-term rabbits, we investigated the relative contributions of the vagus nerve and oxygenation to the increase in pulmonary blood flow at birth. Vagal denervation inhibited the global increase in pulmonary blood flow induced by partial lung aeration, although high inspired oxygen concentrations can partially mitigate this effect. The results of the present study indicate that a vagal reflex may mediate a rapid global increase in pulmonary blood flow in response to partial lung aeration. Air entry into the lungs at birth triggers major cardiovascular changes, including a large increase in pulmonary blood flow (PBF) that is not spatially related to regional lung aeration. To investigate the possible underlying role of a vagally-mediated stimulus, we used simultaneous phase-contrast X-ray imaging and angiography in near-term (30days of gestation) vagotomized (n=15) or sham-operated (n=15) rabbit kittens. Rabbits were imaged before ventilation, when one lung was ventilated (unilateral) with 100% nitrogen (N2 ), air or 100% oxygen (O2 ), and after all kittens were switched to unilateral ventilation in air and then ventilation of both lungs using air. Compared to control kittens, vagotomized kittens had little or no increase in PBF in both lungs following unilateral ventilation when ventilation occurred with 100% N2 or with air. However, relative PBF did increase in vagotomized animals ventilated with 100% O2 , indicating the independent stimulatory effects of local oxygen concentration and autonomic innervation on the changes in PBF at birth. These findings demonstrate that vagal denervation inhibits the previously observed increase in PBF with partial lung aeration, although high inspired oxygen concentrations can partially mitigate this effect.

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Case Studies in Physiology: The Case of the Giant Giraffe.

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Developing an objective method for analyzing vital signs changes in neonates during general anesthesia.

Commonly used general anesthetics are considered to be neurotoxic to the developing rodent brain, leading to poor long-term outcome. However, it is unclear whether these rodent studies can be extrapolated to the human neonate. Given that anesthesia for urgent neonatal surgery cannot be avoided, it is vitally important to assess other factors that may impact neurological outcome following anesthesia and surgery. The purpose of this study is to identify thresholds for detecting vital sign deviations, which may have the potential for affecting neurological outcome following anesthesia and surgery in neonates. These data may be suitable to identify targets for prospective quality improvement projects and guide future research for strategies to reduce detrimental neurocognitive outcomes. A retrospective analysis of vital sign data was performed for neonates (age ≤28 days), undergoing noncardiac surgery over a 4-year period (2010-2013). Thresholds for detecting bradycardia, tachycardia, hypothermia, hyperthermia, hypertension, hypotension, hypocarbia, hypoxemia, significant changes in mean arterial blood pressure, and periods of high inspired oxygen concentration, were proposed. Selected chart review, to identify additional risk factors, and identify sources of data artifact, was performed for 224 cases. Data from 435 procedures in neonates, with median (IQR [range]) ages of 6 (2-16 [0-28]) days were available for analysis. Five (3-6 [0-12]) rule deviations per case were observed; only 11 cases had no rule deviations. Hypothermia was observed in 285/435 (70%), moderate hypocapnia in 298/430 (69%), and severe hypotension in 270/435 (62%) cases. An objective method of comparing cases has been created with a method to automatically identify neonatal vital sign deviations. With further validation the method has the potential to be a powerful tool to drive future quality improvement projects in neonatal anesthesia.

Current concepts of protective ventilation during general anaesthesia.

Mechanical ventilation with high tidal volumes (VT) has been common practice in operating theatres because this strategy recruits collapsed lung tissue and improves ventilation-perfusion mismatch, thus decreasing the need for high inspired oxygen concentrations. Positive end-expiratory pressure (PEEP) was not used routinely because it was thought to impair cardiovascular function. Over the past two decades there have been advances in our understanding of the causes and importance of ventilation-induced lung injury based on studies in animals with healthy lungs, and trials in critically ill patients with and without acute respiratory distress syndrome. Recent data from randomised controlled trials in patients receiving ventilation during general anaesthesia for surgery have demonstrated that lung-protective strategies (use of low VT, use of PEEP if indicated, and avoidance of excessive oxygen concentrations) are also of importance during intraoperative ventilation.

Central venous-to-arterial carbon dioxide gradient as a marker of occult tissue hypoperfusion after major surgery.

The central venous-arterial carbon dioxide tension gradient ('CO₂gap') has been shown to correlate with cardiac output and tissue perfusion in septic shock. Compared to central venous oxygen saturation (SCVO2), the CO₂gap is less susceptible to the effect of hyperoxia and may be particularly useful as an adjunctive haemodynamic target in the perioperative period. This study investigated whether a high CO₂gap was associated with an increased systemic oxygen extraction (O2ER >0.3) or occult tissue hypoperfusion in 201 patients in the immediate postoperative period. The median CO₂gap of all patients was 8 mmHg (IQR 6 to 9), and a large CO₂gap was very common (> 6mmHg in 139 patients [69%], 95% CI 63 to 75; >5 mmHg in 170 patients [85%], 95% CI 79 to 89). A CO₂ gap >5 mmHg had a higher sensitivity (93%) and negative predictive value (74%) than a CO₂gap >6 mmHg in excluding occult tissue hypoperfusion. Of the four variables that were predictive of an increased O₂ER in the multivariate analysis-CO₂gap, arterial pH, haemoglobin and arterial lactate concentrations-the CO₂gap (odds ratio 4.41 per mmHg increment, 95% CI 1.7 to 11.2, P=0.002) was most important and explained about 34% of the variability in the risk of occult tissue hypoperfusion. In conclusion, a normal CO₂ gap (<5 mmHg) had a high sensitivity and negative predictive value in excluding inadequate systemic oxygen delivery and may be useful as an adjunct to other haemodynamic targets in avoiding occult tissue hypoperfusion in the perioperative setting when high inspired oxygen concentrations are used.

Self-reported attitudes versus actual practice of oxygen therapy by ICU physicians and nurses.

BackgroundHigh inspiratory oxygen concentrations are frequently administered in ventilated patients in the intensive care unit (ICU) but may induce lung injury and systemic toxicity. We compared beliefs and actual clinical practice regarding oxygen therapy in critically ill patients.MethodsIn three large teaching hospitals in the Netherlands, ICU physicians and nurses were invited to complete a questionnaire about oxygen therapy. Furthermore, arterial blood gas (ABG) analysis data and ventilator settings were retrieved to assess actual oxygen practice in the same hospitals 1 year prior to the survey.ResultsIn total, 59% of the 215 respondents believed that oxygen-induced lung injury is a concern. The majority of physicians and nurses stated that minimal acceptable oxygen saturation and partial arterial oxygen pressure (PaO2) ranges were 85% to 95% and 7 to 10 kPa (52.5 to 75 mmHg), respectively. Analysis of 107,888 ABG results with concurrent ventilator settings, derived from 5,565 patient admissions, showed a median (interquartile range (IQR)) PaO2 of 11.7 kPa (9.9 to 14.3) [87.8 mmHg], median fractions of inspired oxygen (FiO2) of 0.4 (0.4 to 0.5), and median positive end-expiratory pressure (PEEP) of 5 (5 to 8) cm H2O. Of all PaO2 values, 73% were higher than the upper limit of the commonly self-reported acceptable range, and in 58% of these cases, neither FiO2 nor PEEP levels were lowered until the next ABG sample was taken.ConclusionsMost ICU clinicians acknowledge the potential adverse effects of prolonged exposure to hyperoxia and report a low tolerance for high oxygen levels. However, in actual clinical practice, a large proportion of their ICU patients was exposed to higher arterial oxygen levels than self-reported target ranges.

Cardiac Compression of Lung Lower Lobes after Coronary Artery Bypass Graft with Cardiopulmonary Bypass

BackgroundAtelectasis is a major cause of hypoxemia after coronary artery bypass grafting (CABG) and is commonly ascribed to general anesthesia, high inspiratory oxygen concentration and cardiopulmonary bypass (CPB). The objective of this study was to evaluate the role of heart-induced pulmonary compression after CABG with CPB.MethodsSeventeen patients without pre-operative cardiac failure who were scheduled for coronary artery bypass graft underwent pre- and postoperative thoracic computed tomography. The cardiac mass, the pressure exerted on the lungs by the right and left heart and the fraction of collapsed lower lobe segments below and outside of the heart limits were evaluated on a computed tomography section 1 cm above the diaphragmatic cupola.ResultsIn the postoperative period, cardiac mass increased by 32% (117±31 g versus 155±35 g, p<0.001), leading to an increase in the pressure that was exerted on the lungs by the right (2.2±0.6 g.cm−2 versus 3.2±1.2 g.cm−2, p<0.05) and left heart (2.4±0.7 g.cm−2 versus 4.2±1.8 g.cm−2, p<0.001). The proportion of collapsed lung segments beneath the heart markedly increased [from 6.7% to 32.9% on the right side (p<0.001) and from 6.2% to 29% on the left side (p<0.001)], whereas the proportion of collapsed lung segments outside of the heart limits slightly increased [from 0.7% to 10.8% on the right side (p<0.001) and from 1.5% to 12.6% on the left side (p<0.001)].ConclusionThe pressure that is exerted by the heart on the lungs increased postoperatively and contributed to the collapse of subjacent pulmonary segments.