Proposed protocol for utilising high-flow nasal oxygen therapy in treatment of dogs hospitalised due to pneumonia.

BACKGROUND: High-flow nasal oxygen (HFNO) therapy is a non-invasive respiratory support method that provides oxygen-enriched, warmed, and humidified air to respiratory-compromised patients. It is widely used in human medical care, but in veterinary medicine it is still a relatively new method. No practical guidelines exist for its use in canine pneumonia patients, although they could potentially benefit from HFNO therapy. This study aims to provide a new, safe, non-invasive, and effective treatment protocol for oxygen supplementation of non-sedated dogs with pneumonia. METHODS: Twenty privately owned dogs with pneumonia will receive HFNO therapy at a flow rate of 1-2 L/kg, and the fraction of inspired oxygen will be determined individually (ranging from 21% to 100%). HFNO therapy will continue as long as oxygen support is needed based on clinical evaluation. Patients will be assessed thrice daily during their hospitalisation, with measured primary outcomes including partial pressure of oxygen, oxygen saturation, respiratory rate and type, days in hospital, and survival to discharge. DISCUSSION: The proposed protocol aims to provide a practical guideline for applying HFNO to dogs hospitalised due to pneumonia. The protocol could enable more efficient and well-tolerated oxygenation than traditional methods, thus hastening recovery and improving survival of pneumonia patients.

Impaired Cognitive Performance in Mice Exposed to Prolonged Hyperoxia.

Supplementation of oxygen at concentrations significantly above environmental level for prolonged periods may lead to hyperoxia and tissue toxicity. The mammalian brain undergoes structural and functional changes during adaptation to hypoxia and hyperoxia. In this study we investigated the effect of prolonged hyperoxic exposure on cognitive and motor performance in mice. Two-month-old male mice were placed in either hyperoxic (50% O2) or normoxic conditions for 3 weeks. Cognitive function was measured using the Y-maze test. High alteration rate between the three arms of the maze is indicative of sustained memory and cognitive function. Motor function was measured using the grip strength and rotarod tests. In the rotarod test high speed and long latency are indicative of coordination and resistance. After 3 weeks of exposure, hematocrit levels were significantly decreased in the hyperoxia group compared to normoxic control littermates (%, mean ± SD, 37.8 ± 1.3, n = 15 vs. 49.9 ± 5.1, n = 15, p < 0.05). In the Y-maze test, chronic hyperoxic exposure resulted in a statistically significant decrease in alteration rate compared to normoxic control (%, mean ± SD, 53.4 ± 9.9, n = 30 vs. 61.2 ± 9.5, n = 15, p < 0.05). The rotarod and grip strength tests did not show statistically significant changes between the two groups. Our data suggest that chronic hyperoxia may lead to decreased cognitive performance in adult mice, which may be secondary to structural and functional changes in the brain.

Experimental Models to Study End-Organ Morbidity in Sleep Apnea: Lessons Learned and Future Directions.

Sleep apnea (SA) is a very prevalent sleep breathing disorder mainly characterized by intermittent hypoxemia and sleep fragmentation, with ensuing systemic inflammation, oxidative stress, and immune deregulation. These perturbations promote the risk of end-organ morbidity, such that SA patients are at increased risk of cardiovascular, neurocognitive, metabolic and malignant disorders. Investigating the potential mechanisms underlying SA-induced end-organ dysfunction requires the use of comprehensive experimental models at the cell, animal and human levels. This review is primarily focused on the experimental models employed to date in the study of the consequences of SA and tackles 3 different approaches. First, cell culture systems whereby controlled patterns of intermittent hypoxia cycling fast enough to mimic the rates of episodic hypoxemia experienced by patients with SA. Second, animal models consisting of implementing realistic upper airway obstruction patterns, intermittent hypoxia, or sleep fragmentation such as to reproduce the noxious events characterizing SA. Finally, human SA models, which consist either in subjecting healthy volunteers to intermittent hypoxia or sleep fragmentation, or alternatively applying oxygen supplementation or temporary nasal pressure therapy withdrawal to SA patients. The advantages, limitations, and potential improvements of these models along with some of their pertinent findings are reviewed.

Exertional Desaturation in Idiopathic Pulmonary Fibrosis: The Role of Oxygen Supplementation in Modifying Cerebral-Skeletal Muscle Oxygenation and Systemic Hemodynamics.

BACKGROUND: In patients with idiopathic pulmonary fibrosis (IPF) with isolated exertional desaturation, there are limited data regarding the effectiveness of oxygen supplementation during exercise training; the underlying mechanisms that contribute to these responses are unknown. OBJECTIVES: To examine in these IPF patients the effects of oxygen supplementation during submaximal exercise (vs. medical air) on cerebral/skeletal muscle oxygenation and systemic hemodynamics. METHODS: In this randomized, cross-over, placebo-controlled trial, IPF patients (n = 13; 63.4 ± 9.6 years) without resting hypoxemia but a significant desaturation during maximal cardiopulmonary exercise testing underwent 2 steady-state exercise trials (65% peak-work-load), breathing either oxygen-enriched or medical air. Cerebral/skeletal muscle oxygenation (near-infrared spectroscopy) and beat-by-beat hemodynamics (photoplethysmography) were monitored. RESULTS: In the air protocol, from the initial minutes of submaximal exercise, patients exhibited a marked decline in cerebral oxygenated hemoglobin (O2Hb) and an abrupt rise in deoxygenated hemoglobin (HHb). Oxygen supplementation alleviated desaturation, lessened dyspnea, and prolonged exercise duration (p < 0.01). Oxygen supplementation during exercise (i) attenuated cerebral deoxygenation (cerebral-HHb: 0.7 ± 1.9 vs. 2.5 ± 1.5 µmol/L, O2 and air protocol; p = 0.009) and prevented cerebral-Hbdifference decline (2.1 ± 2.7 vs. -1.7 ± 2.0 µmol/L; p = 0.001), (ii) lessened the decline in muscle O2-saturation index, and (iii) at isotime exercise, it resulted in lower muscle-HHb (p = 0.05) and less leg fatigue (p < 0.05). No differences between protocols were observed in exercise cardiac output and vascular resistance. CONCLUSIONS: IPF patients with isolated exertional hypoxemia exhibit an inability to increase/maintain cerebral oxygenation during submaximal exercise. Correcting desaturation with O2 supplementation prevented the decline in brain oxygenation, improved muscle oxygenation, and lessened dyspnea, suggesting an efficacy of acute oxygen supplementation during exercise training in protecting brain hypoxia in these IPF patients.

Physiologic and blood gas effects of xylazine-ketamine versus xylazine-tiletamine-zolazepam immobilization of white-tailed deer before and after oxygen supplementation: a preliminary study.

OBJECTIVE: To compare oxygenation and ventilation in white-tailed deer (Odocoileus virginianus) anesthetized with two treatments with and without oxygen supplementation. STUDY DESIGN: Randomized, blinded, crossover study. ANIMALS: A total of eight healthy adult white-tailed deer weighing 49-62 kg. METHODS: Each deer was anesthetized twice intramuscularly: 1) treatment XK, xylazine (2 mg kg-1) and ketamine (6 mg kg-1) and 2) treatment XTZ, xylazine (2 mg kg-1) and tiletamine-zolazepam (4 mg kg-1). With the deer in sternal position, arterial and venous blood was collected before and at 30 minutes during administration of oxygen at 1 L minute-1 through a face mask. PaO2 and heart rate (HR) were compared using two-way repeated measures anova. pH, PaCO2 and lactate concentration were analyzed using mixed-effects linear models, p < 0.05. RESULTS: When breathing air, PaO2 was < 80 mmHg (10.7 kPa) in six and seven deer with XK and XTZ, respectively, and of these, PaO2 was < 60 mmHg (8.0 kPa) in three and five deer, respectively. With oxygen supplementation, PaO2 increased to 128 ± 4 and 140 ± 5 mmHg (17.1 ± 0.5 and 18.7 ± 0.7 kPa), mean ± standard error, with XK and XTZ, respectively (p < 0.001). PaO2 was not significantly different between treatments at either time point. HR decreased during oxygen supplementation in both treatments (p < 0.001). Lactate was significantly lower (p = 0.047) with XTZ than with XK (2.2 ± 0.6 versus 3.5 ± 0.6 mmol L-1) and decreased (p < 0.001) with oxygen supplementation (4.1 ± 0.6 versus 1.6 ± 0.6 mmol L-1). PaCO2 increased in XTZ during oxygen breathing. CONCLUSIONS AND CLINICAL RELEVANCE: Treatments XK and XTZ resulted in hypoxemia, which responded to oxygen supplementation. Both treatments are suitable for immobilization of white-tailed deer under the study circumstances.

Daily oxygen supplementation to the incubator at different stages of embryonic development alters the activity of antioxidant enzymes in the lung tissue of broiler chicks at a high altitude.

1. Pulmonary hypertension, associated with mitochondrial function in the lung tissue of broilers, can occur at hypoxic high altitudes. The present research examined the impacts of O2 supplementation at different embryonic stages on broiler organ development and antioxidant enzyme activities.2. In total, 360 eggs from Ross 308 broiler breeders at sea level were divided into a control group (O2 non-supplementation group) and three experimental groups daily 1 h 23.5% O2 supplementation from days 0 to 11 (O0-11), from days 12 to 21 (O12-21), and from days 18 to 21 (O18-21) of embryonic age.3. The lung, heart, right ventricular (RV), and left ventricular (LV) + septum of newly hatched and seven day old chicks from every group were dissected and weighed. Antioxidant enzyme activities were examined in their lung tissue.4. The lung weight did not change in any group. At hatching, the heart weight (g and %) was higher in the O12-21 and O18-21 groups than in the O0-11 and control groups, but the relative heart weight was the highest in the O18-21 group in comparison with the O12-21 group.5. Superoxide dismutase (SOD) activity increased in all experimental groups at both ages, but glutathione peroxidase (GPx) activity increased only in seven day old chicks. Catalase (CAT) exhibited high activity in the O12-21 and O18-21 groups at hatching. In the seven day old chicks, while the CAT activity did not change in the O18-21 group, it decreased in the O0-11 group and increased in the O12-21 group.6. Glutathione reductase (GR) activity did not change in the O18-21 group, but GR exhibited low activity in the O0-11 group and high activity in the O18-21 group in newly hatched chicks. The GR activity only decreased in the O18-21 group of seven day old chicks.7. The results indicated that oxygen supplementation to the incubator caused alterations in the antioxidant enzyme activities in the lungs of broiler chicks, and this may have been in response to oxidative stress.

Association between SpO2/FiO2 Ratio and PaO2/FiO2 Ratio in Different Modes of Oxygen Supplementation.

BACKGROUND: Acute hypoxemic respiratory failure (AHRF) is a major factor for increased mortality in the intensive care unit (ICU). We hypothesized that the noninvasive index SpO2/FiO2 (SF) ratio can be used as a surrogate to invasive index PaO2/FiO2 (PF) as SF ratio correlates with PF ratio in all modes of oxygen supplementation. PATIENTS AND METHODS: Patients with acute respiratory failure admitted to the intensive care unit were enrolled in this retrospective cross-sectional study. Fraction of inspired oxygen (FiO2), method of oxygen supplementation, and partial pressure of arterial oxygen (PaO2) were noted from the ABG reports in the medical records. The corresponding SpO2 was noted from the nurse's chart. The calculated SF and PF ratios were recorded, and correlation between the same was noted in different methods of oxygen administration. RESULTS: A total of 300-sample data were collected. Pearson's correlation was used to quantify the relationship between the variables. The study showed a positive correlation, r = 0.66 (p <0.001), between PF ratio and SF ratio. SF threshold values were 285 and 323 for corresponding PF values of 200 and 300 with a sensitivity and specificity in the range of 70 to 80%. In addition, SF and PF could also be used interchangeably irrespective of the mode of oxygen supplementation, as the median values of PF ratio (p = 0.06) and SF ratio (p = 0.88) were not statistically significant. CONCLUSION: In patients with AHRF, the noninvasive SF ratio can be used as a surrogate to invasive index PF in all modes of oxygen supplementation. HOW TO CITE THIS ARTICLE: Babu S, Abhilash KPP, Kandasamy S, Gowri M. Association between SpO2/FiO2 Ratio and PaO2/FiO2 Ratio in Different Modes of Oxygen Supplementation. Indian J Crit Care Med 2021;25(9):1001-1005.

Accuracy of oxygen delivery through bubble humidifiers and nasal catheters.

OBJECTIVE: To evaluate the equipment used for nasal insufflation of oxygen and determine its accuracy. STUDY DESIGN: Original study. METHODS: Oxygen delivery assemblies consisting of a flowmeter, bubble humidifier, oxygen delivery tubing and nasal insufflation catheters were assembled. Single and double catheter assemblies were made for four sizes of nasogastric feeding tubes (3.5 Fr, 5.0 Fr, 8.0 Fr and 10.0 Fr) resulting in 64 individual assemblies. A gas flow analyzer measured oxygen flow at the tip of the nasal catheter assemblies and from the pressure relief valve (PRV) of the bubble humidifiers. Statistical analyses were conducted to assess the functionality of assemblies. For functional assemblies, the accuracy of oxygen flow relative to the prescribed flow settings was determined. RESULTS: Catheter size was significantly associated with the functionality of assemblies. Probability (95% confidence interval) of 3.5 Fr, 5.0 Fr and 8.0 Fr assemblies being functional was estimated at 0.53 (0.14, 0.89), 0.83 (0.36, 0.98) and 0.98 (0.76, 0.99), respectively. All 10.0 Fr assemblies were functional. Functional assemblies, in general, consistently under-delivered the prescribed flow because a large portion of set flow was diverted through the bubble humidifier PRV. CONCLUSIONS: Leaks through the PRV cause significant diversion of oxygen prior to it reaching the catheter tips. Smaller patients are particularly susceptible, as small catheters limit oxygen delivery creating proportionally greater leaks through the PRV. CLINICAL RELEVANCE: It was not possible to accurately deliver oxygen because of leaks through the PRV. Targeting a specific outcome (e.g., oxyhemoglobin saturation > 94%, PaO2 80-120 mmHg; 11-16 kPa) and avoiding unnecessarily high fractions of inspired oxygen cannot be done if flow delivery cannot be accurately assured. One possible solution would be to use a bubble humidifier with a 6 psi PRV that does not leak prior to reaching the opening pressure.

Comparison of the effect of oxygen supplementation using flow-by or a face mask on the partial pressure of arterial oxygen in sedated dogs.

AIMS To compare the effect of oxygen supplementation using flow-by or a face mask on the partial pressure of arterial oxygen (PaO2) in sedated dogs. METHODS Twenty healthy dogs weighing >15 kg, of mixed sex and breed, were enrolled in a randomised cross-over study. Each dog was sedated with I/M 0.015 mg/kg medetomidine and 0.5 mg/kg methadone. Twenty minutes later dogs were exposed to two 5-minute treatment periods of oxygen supplementation separated by a 15-minute washout period during which dogs were allowed to breathe room air. During the treatment periods, oxygen was delivered at a flow rate of 3 L/minute either through a face mask (face mask oxygenation), or via a tube held 2 cm from the dog's nares (flow-by oxygenation). The order in which the treatments were administered was randomised. Arterial blood was collected for blood gas analysis and rectal temperature measured at four times: prior to commencing treatments, after each treatment, and at the end of the 15 minutes washout period between treatments. RESULTS The mean PaO2 in arterial samples taken from the dogs after face mask oxygen supplementation was 371.3 (SE 13.74) mmHg which was higher than in samples taken after they received flow-by oxygen supplementation (182.2 (SE 6.741) mmHg; p<0.001). The mean PaO2 in samples taken after receiving either form of oxygen supplementation was higher than in samples taken after the dogs had been breathing room air (82.43 (SE 2.143) mmHg; p<0.001). There was no association between sex, age, weight or breed of dogs and blood gas parameters or rectal temperature (p>0.05). CONCLUSIONS Oxygen supplementation delivered using a face mask was more effective at increasing PaO2 than flow-by oxygen supplementation. Flow-by oxygen supplementation at a distance of 2 cm from the nose may be a suitable alternative when the use of a face mask is not tolerated by the patient.

Oxygen Supplementation is Effective in Attenuating Maternal Cerebral Blood Deoxygenation After Spinal Anesthesia for Cesarean Section.

The purpose of this study was to measure changes in maternal cerebral blood oxygenation using near-infrared spectroscopy (NIRS) for 15 min after spinal anesthesia performed for cesarean section, and to determine the efficacy of supplemental oxygen in maintaining maternal cerebral blood oxygenation. Thirty patients were randomly assigned to either receive 100% oxygen via a facemask at a constant flow rate of 3 l/min throughout the study (O2 group), or were evaluated without supplemental oxygen (Air group). Changes in cerebral blood oxygenation were evaluated using the following parameters: oxy-hemoglobin (Hb), deoxy-Hb, and total-Hb concentrations, as well as tissue oxygen index (TOI), measured over the forehead by NIRS. Mean arterial pressure (MAP) and heart rate (HR) were also recorded throughout the study. Mean oxy-Hb, total-Hb, TOI, and MAP in both groups decreased significantly from baseline values (P<0.05). The reduction in oxy-Hb and TOI in the Air group was significantly greater than that in the O2 group (oxy-Hb: -4.72 vs. -2.96 µmol/l; P<0.05, TOI: -6.82 vs. -1.68%; P<0.01); however, there were no significant differences in the reduction of total-Hb and MAP between the groups. Mean deoxy-Hb in the Air group was significantly higher than that in the O2 group (0.02 vs. -1.01 µmol/l; P<0.05). The results of the present study demonstrate that oxygen supplementation attenuates cerebral blood deoxygenation secondary to the reduction in cerebral blood flow following spinal anesthesia.

Minimum anesthetic concentration of isoflurane and sevoflurane and cardiorespiratory effects of varying inspired oxygen fractions in Magellanic penguins (Spheniscus magellanicus).

The aim of this study was to determine the minimum anesthetic concentration of isoflurane (MACISO) and sevoflurane (MACSEVO) and evaluate the cardiorespiratory changes induced by varying fractions of inspired oxygen (FiO2) in Magellanic penguins (Spheniscus magellanicus). Twenty adult penguins (3.53 ± 0.44 kg) of undetermined sex were used. Both MACISO (n = 9) and MACSEVO (n = 13) were established using an up-and-down design. Next, twelve mechanically ventilated penguins were maintained at 1 MACISO or 1 MACSEVO (n = 6 per group) with the FiO2 initially set at 1.0. Three FiO2 values (0.6, 0.4 and 0.2) were then held constant during anesthesia for 20 minutes each. Arterial blood samples were collected for gas analysis after the 20-minute period for each FiO2. Mean ± SD MACISO was 1.93 ± 0.10% and MACSEVO was 3.53 ± 0.13%. Other than heart rate at 0.6 FiO2 (86 ± 11 beats/minute in MACISO and 132 ± 37 beats/minute in MACSEVO; p = 0.041), no significant cardiorespiratory differences were detected between groups. In both groups, decreasing the FiO2 produced increased pH values and reduced partial pressures of carbon dioxide and bicarbonate. Partial pressures of oxygen (PaO2) gradually lowered from 1.0 FiO2 through 0.2 FiO2, though hypoxemia (PaO2 < 80 mmHg) occurred only with the latter FiO2. The MACISO and the MACSEVO for the Magellanic penguin fell within the upper range of reported avian MAC estimates. To prevent hypoxemia in healthy, mechanically ventilated, either isoflurane- or sevoflurane-anesthetized Magellanic penguins, a minimum FiO2 of 0.4 should be used.

Retrospective evaluation of the respiratory rate-oxygenation index to predict the outcome of high-flow nasal cannula oxygen therapy in dogs (2018-2021): 81 cases.

OBJECTIVE: To evaluate the respiratory rate-oxygenation index (ROX), modified ROX index (ROX-HR), and the ratio of pulse oximetry saturation (Spo2) to Fio2 (SF) to determine if these indices over time are predictive of outcome in dogs treated with high-flow nasal cannula oxygen therapy (HFNC). DESIGN: Retrospective study. SETTING: Two university teaching hospitals. ANIMALS: Eighty-one client-owned dogs treated with HFNC for hypoxemic respiratory failure. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The ROX was defined as the SF divided by the respiratory rate (RR), and the ROX-HR was defined as the ROX divided by the heart rate multiplied by 100. The overall success rate of HFNC was 44% (n = 36/81). Dogs weaned from HFNC had a significantly higher ROX (P < 0.0001) at 1-3, 5-10, 12, and 15 hours than dogs that failed HFNC. Both the ROX and SF showed excellent discriminatory power in predicting HFNC failure at 6 hours, with an area under receiver operating curve of 0.85 (95% confidence interval: 0.72-0.99; P < 0.002) and 0.86 (95% confidence interval: 0.73-0.99; P < 0.001), respectively. The optimal cutoff values for predicting HFNC failure at 6 hours were a ROX ≤3.68 (sensitivity 72%, specificity 92%) and an SF ≤143 (sensitivity 79%, specificity 93%). CONCLUSIONS: These results suggest that similar to people, the ROX and SF are useful predictors of HFNC failure. These indices are easy to measure at the bedside and may have clinical use. Future prospective studies are warranted to confirm the findings and to optimize cutoff values in a larger population of dogs undergoing HFNC.

Clinical Implementation of Automated Oxygen Titration in a Tertiary Care Hospital.

BACKGROUND: When treating acute respiratory failure, both hypoxemia and hyperoxemia should be avoided. SpO2 should be monitored closely and O2 flows adjusted accordingly. Achieving this goal might be easier with automated O2 titration compared with manual titration of fixed-flow O2. We evaluated the feasibility of using an automated O2 titration device in subjects treated for acute hypoxemic respiratory failure in a tertiary care hospital. METHODS: Health-care workers received education and training about oxygen therapy, and were familiarized with an automated O2 titration device (FreeO2,). A coordinator was available from 8:00 am to 5:00 pm during weekdays to provide technical assistance. The ability of the device to maintain SpO2 within the prescribed therapeutic window was recorded. Basic clinical information was recorded. RESULTS: Subjects were enrolled from November 2020 to August 2022. We trained 508 health-care workers on the use of automated O2 titration, which was finally used on 872 occasions in 763 subjects, distributed on the respiratory, COVID-19, and thoracic surgery wards, and in the emergency department. Clinical information could be retrieved for 609 subjects (80%) who were on the system for a median (interquartile range) of 3 (2-6) d, which represented 2,567 subject-days of clinical experience with the device. In the 82 subjects (14%) for whom this information was available, the system maintained SpO2 within the prescribed targets 89% of the time. Ninety-six subjects experienced clinical deterioration as defined by the need to be transferred to the ICU and/or requirement of high flow nasal oxygen but none of these events were judged to be related to the O2 device. CONCLUSIONS: Automated O2 titration could be successfully implemented in hospitalized subjects with hypoxemic respiratory failure from various causes. This experience should foster further improvement of the device and recommendations for an optimized utilization.

Effect of oxygen supplementation on cognitive performance among HEMS providers after acute exposure to altitude: the HEMS II randomized clinical trial.

IMPORTANCE: Emergency medical services (EMS) providers transiently ascend to high altitude for primary missions and secondary transports in mountainous areas in helicopters that are unpressurised and do not have facilities for oxygen supplementation. The decrease in cerebral oxygen saturation can lead to impairment in attention and reaction time as well as in quality of care during acute exposure to altitude. OBJECTIVE: The primary aim of the current study was to investigate the effect of oxygen supplementation on cognitive performance in Helicopter EMS (HEMS) providers during acute exposure to altitude. DESIGN, SETTING, AND PARTICIPANTS: This interventional, randomized, controlled, double-blind, cross-over clinical trial was conducted in October 2021. Each trial used a simulated altitude scenario equivalent to 4000 m, in which volunteers were exposed to hypobaric hypoxia with a constant rate of ascent of 4 m/s in an environmental chamber under controlled, replicable, and safe conditions. Trials could be voluntarily terminated at any time. Inclusion criteria were being members of emergency medical services and search and rescue services with an age between 18 and 60 years and an American Society of Anesthesiologists physical status class I. EXPOSURES: Each participant conducted 2 trials, one in which they were exposed to altitude with oxygen supplementation (intervention trial) and the other in which they were exposed to altitude with ambient air supplementation (control trial). MAIN OUTCOMES AND MEASURES: Measurements included peripheral oxygen saturation (SpO2), cerebral oxygenation (ScO2), breathing and heart rates, Psychomotor Vigilance Test (PVT), Digit-Symbol Substitution Test (DSST), n-Back test (2-BACK), the Grooved Pegboard test, and questionnaires on subjective performance, stress, workload, and positive and negative affect. Paired t-tests were used to compare conditions (intervention vs. control). Data were further analyzed using generalized estimating equations (GEE). RESULTS: A total of 36 volunteers (30 men; mean [SD] age, 36 [9] years; mean [SD] education, 17 [4] years) were exposed to the intervention and control trials. The intervention trials, compared with the control trials, had higher values of SpO2 (mean [SD], 97.9 [1.6] % vs. 86 [2.3] %, t-test, p = 0.004) and ScO2 (mean [SD], 69.9 [5.8] % vs. 62.1 [5.2] %, paired t-test, p = 0.004). The intervention trials compared with the control trials had a shorter reaction time (RT) on the PVT after 5 min (mean [SD], 277.8 [16.7] ms vs. 282.5 [15.3] ms, paired t-test, p = 0.006) and after 30 min (mean [SD], 276.9 [17.7] ms vs. 280.7 [15.0] ms, paired t-test, p = 0.054) at altitude. While controlling for other variables, there was a RT increase of 0.37 ms for each % of SpO2 decrease. The intervention trials showed significantly higher values for DSST number of correct responses (with a difference of mean [SD], 1.2 [3.2], paired t-test, p = 0.035). Variables in the intervention trials were otherwise similar to those in the control trials for DSST number of incorrect responses, 2-BACK, and the Grooved Pegboard test. CONCLUSIONS AND RELEVANCE: This randomized clinical trial found that oxygen supplementation improves cognitive performance among HEMS providers during acute exposure to 4000 m altitude. The use of oxygen supplementation may allow to maintain attention and timely reaction in HEMS providers. The impact of repeated altitude ascents on the same day, sleep-deprivation, and additional stressors should be investigated. Trial registration NCT05073406, ClinicalTrials.gov trial registration.

Reversal of arterial oxygen desaturation with the use of an oxygen concentrator during injectable anaesthesia in feral cats positioned in the Trendelenburg, dorsal or lateral surgical position.

INTRODUCTION: This study observed the effects of oxygen supplementation, via an oxygen concentrator, on peripheral arterial blood oxygenation (SpO2) measured by pulse oximetry in anaesthetised cats undergoing spay in three different surgical positions. A total of 192 female feral cats were investigated for a large-scale trap-neuter-release program. Cats were anaesthetised with an intramuscular combination of butorphanol (0,4 mg / kg), ketamine (7-10 mg / kg) and medetomidine (0,03-0,05 mg / kg). Cats were randomly allocated to undergo spay in either Trendelenburg (TR) (70° downward head tilt), lateral (LR) or dorsal (DR) recumbency. Cats were breathing spontaneously either room air or 2 L/minute oxygen via a tight-fitting face mask. Pulse rate (in beats per minute), respiratory rate (in breaths per minute) and SpO2 (in percentage) were measured at baseline in left lateral recumbency and afterwards continuously after being positioned in allocated surgical position. At the end of surgery, cats were placed again in left recumbency, and all parameters were re-evaluated after five minutes. Overall, 33 % of cats showed severe arterial oxygen desaturation (SpO2 < 90 %) at baseline when breathing room air. When oxygen was supplemented during the procedure, arterial oxygen desaturation resolved in all cats. At the end of the procedure, 29 % of cats were hypoxaemic when oxygen was not supplemented, with an overall higher percentage of hypoxaemic cats in TR as compared to DR and LR recumbencies. All cats recovered well from surgery and were released within 24 hours post-anaesthesia. Arterial oxygen desaturation is frequent in cats anaesthetised with injectable anaesthesia for spay under field conditions. Oxygen supplementation administered via a tight-fitting mask resolved arterial oxygen desaturation in this feral cat population regardless of the surgical position and therefore oxygen supplementation is recommended in any case.

INTRODUCTION: Cette étude a observé les effets d'une supplémentation en oxygène, via un concentrateur d'oxygène, sur l'oxygénation du sang artériel périphérique (SpO2) mesurée par oxymétrie de pouls chez des chats anesthésiés subissant une stérilisation dans trois positions chirurgicales différentes. Au total, 192 chats sauvages femelles ont été examinés dans le cadre d'un programme de piégeage, de stérilisation et de remise en liberté à grande échelle. Les chats ont été anesthésiés avec une combinaison de butorphanol (0,4 mg / kg), de kétamine (7­10 mg / kg) et de médétomidine (0,03­0,05 mg / kg) appliquée par voie intramusculaire. Les chats ont été répartis au hasard pour subir une stérilisation en position de Trendelenburg (TR) (inclinaison de la tête de 70° vers le bas), en décubitus latéral (LR) ou en décubitus dorsal (DR). Les chats respiraient spontanément soit de l'air ambiant, soit de l'oxygène à raison de 2 L/minute par l'intermédiaire d'un masque facial bien ajusté. Le pouls (en battements par minute), la fréquence respiratoire (en respirations par minute) et la SpO2 (en pourcentage) ont été mesurés au départ en décubitus latéral gauche, puis en continu après avoir été placés dans la position chirurgicale attribuée. À la fin de l'opération, les chats ont été replacés en décubitus latéral gauche et tous les paramètres ont été réévalués au bout de cinq minutes. Dans l'ensemble, 33 % des chats présentaient une désaturation sévère en oxygène artériel (SpO2 < 90 %) au départ lorsqu'ils respiraient de l'air ambiant. Lorsque de l'oxygène a été ajouté pendant la procédure, la désaturation en oxygène artériel s'est résorbée chez tous les chats. À la fin de l'intervention, 29 % des chats étaient hypoxémiques lorsque l'oxygène n'était pas administré, avec un pourcentage global plus élevé de chats hypoxémiques en décubitus dorsal qu'en décubitus latéral. Tous les chats se sont bien remis de l'opération et ont été libérés dans les 24 heures suivant l'anesthésie. La désaturation en oxygène artériel est fréquente chez les chats anesthésiés par injection pour la stérilisation dans des conditions de terrain. La supplémentation en oxygène administrée via un masque étanche a résolu la désaturation en oxygène artériel dans cette population de chats sauvages, quelle que soit la position chirurgicale et la supplémentation en oxygène est donc recommandée dans tous les cas.

Effect of high perioperative oxygen supplementation on surgical site infections.

Over the past 15 years, several randomized controlled trials, long-term follow-up studies, meta-analyses, and editorials have been published in regard to the effect of a high fraction of inspired oxygen concentration (FiO(2)) during the perioperative period on the incidence of surgical site infections. Although the evidence is not uniformly favorable for all types of surgeries, a beneficial association of 80% FiO(2) has been documented among open abdominal procedures, especially colorectal surgeries.

Epidemiological analysis over two years of SARS-CoV-2 circulation in southern Brazil: old and novel predictors of COVID-19 outcome.

The overwhelming majority of SARS-CoV-2 epidemiological studies cover a narrow time period, making general knowledge about the COVID-19 pandemic difficult. To assess COVID-19-related host aspects in the overall pandemic, we analyzed COVID-19 cases during the first two years of SARS-CoV-2 circulation in southern Brazil. Herein, 390 patients admitted in 2020-2022 to a Brazilian public referral hospital were allocated into two groups according to the COVID-19 outcome: hospital discharge (n=237) or death (n=153). In the univariate analysis, several variables, including sociodemographic, clinical and laboratory aspects (primary data), were significantly different between the analyzed groups. In multivariate logistic regression, eight of these factors remained associated with the COVID-19 outcome. In particular, we report oxygen supplementation and the need for hemodialysis as predictors of hospital discharge and death from COVID-19, respectively. To the best of our knowledge, none of these findings have been previously reported in the Brazilian or world population. In conclusion, our results contribute to current knowledge by demonstrating that factors described at different times may remain associated with COVID-19 over the pandemic and by identifying novel predictors of COVID-19 outcome.

Evaluation of Nasal Oxygen Administration at Various Flow Rates and Concentrations in Conscious, Standing Adult Horses.

This study evaluated the effects of various flow rates and fractions of oxygen on arterial blood gas parameters and on the fraction of inspired oxygen (FIO2) delivered to the distal trachea. Oxygen was administered to 6 healthy, conscious, standing, adult horses via single nasal cannula positioned within the nasopharynx. Three flow rates (5, 15, 30 L/min) and fractions of oxygen (21, 50, 100%) were delivered for 15 minutes, each in a randomized order. FIO2 was measured at the level of the nares and distal trachea. Adverse reactions were not observed with any flow rate. FIO2 (nares and trachea) and PaO2 increased with increasing flow rate and fraction of oxygen (P < .0001). FIO2 (trachea) was significantly less than FIO2 (nares) at 50% and 100% oxygen at all flow rates (P < .0001). Differences in PaO2 were not observed between 100% oxygen-5L/min and 50% oxygen-15L/min and or between 100% oxygen-15L/min and 50% oxygen-30L/min. Tracheal FIO2 for 100% oxygen-15L/min was increased compared to 50% oxygen-30L/min (P < .0001). Respiratory rate, ETCO2, PaCO2, and pH did not differ between treatments. Administration of 50% oxygen via nasal cannula at 15 and 30 L/min effectively increased in PaO2 and was well tolerated in conscious, standing, healthy horses. While these results can be used guide therapy in hypoxemic horses, evaluation of the administration of 50% oxygen to horses with respiratory disease is warranted.

Heterogeneity in management of category II fetal tracings: data from a multihospital healthcare system.

BACKGROUND: Electronic fetal monitoring is widely used to identify and intervene in suspected fetal hypoxia and/or acidemia. Category II fetal heart rate tracings are the most common class of fetal monitoring in labor, and intrauterine resuscitation is recommended given the association of category II fetal heart rate tracings with fetal acidemia. However, limited published data are available to guide intrauterine resuscitation technique selection, leading to heterogeneity in the response to category II fetal heart rate tracings. OBJECTIVE: This study aimed to characterize approaches to intrauterine resuscitation in response to category II fetal heart rate tracings. STUDY DESIGN: This was a survey study administered to labor unit nurses and delivering clinicians (physicians and midwives) across 7 hospitals in a Midwestern healthcare system spanning 2 states. The survey posed 3 category II fetal heart rate tracing scenarios (recurrent late decelerations, minimal variability, and recurrent variable decelerations) and asked participants to select first- and second-line intrauterine resuscitation management strategies. The participants were asked to quantify the level of influence certain factors have on their choice using a scale from 1 to 5. Intrauterine resuscitation strategy selection was compared by clinical role and hospital type (nurses vs delivering clinicians and university-affiliated hospital vs non-university-affiliated hospital). RESULTS: Of 610 providers invited to take the survey, 163 participated (response rate of 27%): 37% of participants from university-affiliated hospitals, 62% of nurses, and 37% of physicians. Maternal repositioning was the most selected first-line strategy, regardless of the type of category II fetal heart rate tracing. First-line management varied by clinical role and hospital affiliation for each fetal heart rate tracing scenario, particularly for minimal variability, which was associated with the most heterogeneity in the first-line approach. Previous experience and recommendations from professional societies were the most influential factors in intrauterine resuscitation selection overall. Of note, 16.5% of participants reported that published evidence did not influence their choice at all. Participants from a university-affiliated hospital were more likely than participants from a non-university-affiliated hospital to consider patient preference when selecting an intrauterine resuscitation technique. Nurses and delivering clinicians differed significantly in the rationale for management choices: nurses were more often influenced by advice from other healthcare providers on the team (P<.001), whereas delivering clinicians were more influenced by literature (P=.02) and ease of technique (P=.02). CONCLUSION: There was significant heterogeneity in the management of category II fetal heart rate tracing. In addition, motivations for choice in intrauterine resuscitation technique varied by hospital type and clinical role. These factors should be considered when creating fetal monitoring and intrauterine resuscitation protocols.

Clinical, polysomnographic, and heart rate variability in highland obstructive sleep apnea patients responding to one-night nocturnal oxygen supplementation: A post-hoc analysis from a randomized, crossover trial.

OBJECTIVE: /Background: This study aimed to explore the clinical, polysomnographic, and heart rate variability (HRV) characteristics of highland obstructive sleep apnea (OSA) patients receiving one-night nocturnal oxygen supplementation (NOS) and to identify factors predicting response. PATIENTS/METHODS: Thirty-four highland OSA patients living in Shangri-La were randomly assigned to receive NOS and sham oxygen in a randomized, placebo-controlled, crossover trial. Clinical assessments, polysomnography, and HRV were measured. A responder was defined as a ≥50% reduction in apnea-hypopnea index (AHI) with NOS compared with sham oxygen. RESULTS: Eighteen participants responded and 16 did not respond, with a median (interquartile range [IQR]) age of 46.5 (36.5-53.0) and 48.0 (44.3-53.3) years, respectively. The median treatment effect (95% CI) on total AHI was -23.2/h (-30.0 to -17.5) and -12.0/h (-16.6 to -7.6) in responders and non-responders (p = 0.004), with similar effects on oxygen desaturation index. The mean OAH duration was prolonged by 7 s in responders together with improved sleep quality and daytime blood pressure. The mean OAH duration at baseline predicted responses to NOS with a sensitivity and specificity of 88.9% and 68.7% (AUC 0.809) at a cut-off point of 24.9 s. Changes in HRV parameters were negatively correlated with changes in mean oxygen saturation and daytime systolic blood pressure only in responders. CONCLUSIONS: NOS significantly improved OSA severity and clinical outcomes in responders, which was related to improvements in parasympathetic activity. Highlanders with shorter mean OAH may be suitable candidates for NOS. These findings provide new information about tailored treatment strategies for highland OSA patients.