scholarly journals Vagal Threshold Determination during Incremental Stepwise Exercise in Normoxia and Normobaric Hypoxia

2020 ◽  
Vol 17 (20) ◽  
pp. 7579
Author(s):  
Filip Neuls ◽  
Jakub Krejci ◽  
Ales Jakubec ◽  
Michal Botek ◽  
Michal Valenta
Keyword(s):  
Exercise Intensity ◽  
Bicycle Ergometer ◽  
Normobaric Hypoxia ◽  
Maximal Heart Rate ◽  
Simulated Altitude ◽  
Three Stages ◽  
Fraction Of Inspired Oxygen ◽  
Substantial Decline ◽  
Inspired Oxygen

This study focuses on the determination of the vagal threshold (Tva) during exercise with increasing intensity in normoxia and normobaric hypoxia. The experimental protocol was performed by 28 healthy men aged 20 to 30 years. It included three stages of exercise on a bicycle ergometer with a fraction of inspired oxygen (FiO2) 20.9% (normoxia), 17.3% (simulated altitude ~1500 m), and 15.3% (~2500 m) at intensity associated with 20% to 70% of the maximal heart rate reserve (MHRR) set in normoxia. Tva level in normoxia was determined at exercise intensity corresponding with (M ± SD) 45.0 ± 5.6% of MHRR. Power output at Tva (POth), representing threshold exercise intensity, decreased with increasing degree of hypoxia (normoxia: 114 ± 29 W; FiO2 = 17.3%: 110 ± 27 W; FiO2 = 15.3%: 96 ± 32 W). Significant changes in POth were observed with FiO2 = 15.3% compared to normoxia (p = 0.007) and FiO2 = 17.3% (p = 0.001). Consequentially, normoxic %MHRR adjusted for hypoxia with FiO2 = 15.3% was reduced to 39.9 ± 5.5%. Considering the convenient altitude for exercise in hypoxia, POth did not differ excessively between normoxic conditions and the simulated altitude of ~1500 m, while more substantial decline of POth occurred at the simulated altitude of ~2500 m compared to the other two conditions.

In vitro evaluation of delays in the adjustment of the fraction of inspired oxygen during CPAP: effect of flow and volume

2020 ◽  
pp. fetalneonatal-2020-319058
Author(s):  
Christoph E. Schwarz ◽  
Gordon Lightbody ◽  
Ingo Müller-Hansen ◽  
Jörg Arand ◽  
Christian F. Poets ◽  
...  
Keyword(s):  
Gas Flow ◽  
Closed Loop ◽  
Volume Flow ◽  
Target Range ◽  
Equilibration Time ◽  
Ventilator Circuit ◽  
Fraction Of Inspired Oxygen ◽  
Inspired Oxygen

BackgroundAdjusting the fraction of inspired oxygen (FiO2) delivered to preterm infants to keep their oxygen saturation within target range remains challenging. Closed-loop automated FiO2 control increases the time infants spend within the assigned target range. The delay with which FiO2 adjustments at the ventilator result in a change in the inspired gas limits the performance of both manual and automated controls.ObjectiveTo evaluate the equilibration time (Teq) between FiO2 adjustments and changes in FiO2 reaching the patient.MethodsIn vitro determination of the delay in FiO2 adjustments at the ventilator at 5 and 8 L/min of gas flow and two different humidifier/ventilator circuit volumes (840 and 432 mL).ResultsTeq values were 31, 23, 20 and 17 s for the volume–flow combinations 840 mL+5 L/min, 840 mL+8 L/min, 432 mL+5 L/min and 432 mL+8 L/min, respectively.ConclusionThe identified delay seems clinically relevant and should be taken into account during manual and automatic control of FiO2.

scholarly journals Performance of ventilators at simulated altitude: study of fraction of inspired oxygen

Critical Care ◽  
2010 ◽  
Vol 14 (Suppl 1) ◽  
pp. P273
Author(s):  
J Tourtier ◽  
S Ramsang ◽  
E Forsans ◽  
S De Rudnicki ◽  
A Chrissment ◽  
...  
Keyword(s):  
Simulated Altitude ◽  
Fraction Of Inspired Oxygen ◽  
Inspired Oxygen

scholarly journals Overnight hypoxic exposure and glucagon-like peptide-1 and leptin levels in humans

2008 ◽  
Vol 33 (5) ◽  
pp. 929-935 ◽  
Author(s):  
Eric M. Snyder ◽  
Richard D. Carr ◽  
Carolyn F. Deacon ◽  
Bruce D. Johnson
Keyword(s):  
Normobaric Hypoxia ◽  
Hypoxic Exposure ◽  
Healthy Humans ◽  
Endocrine Factors ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Fraction Of Inspired Oxygen ◽  
Loss Of Appetite ◽  
Plasma Leptin ◽  
Inspired Oxygen

Altitude exposure has been associated with loss of appetite and weight loss in healthy humans; however, the endocrine factors that contribute to these changes remain unclear. Leptin and glucagon-like peptide-1 (GLP-1) are peptide hormones that contribute to the regulation of appetite. Leptin increases with hypoxia; however, the influence of hypoxia on GLP-1 has not been studied in animals or humans to date. We sought to determine the influence of normobaric hypoxia on plasma leptin and GLP-1 levels in 25 healthy humans. Subjects ingested a control meal during normoxia and after 17 h of exposure to normobaric hypoxia (fraction of inspired oxygen of 12.5%, simulating approximately 4100 m). Plasma leptin was assessed before the meal, and GLP-1 was assessed premeal, at 20 min postmeal, and at 40 min postmeal. We found that hypoxia caused a significant elevation in plasma leptin levels (normoxia, 4.9 ± 0.8 pg·mL–1; hypoxia, 7.7 ± 1.5 pg·mL–1; p < 0.05; range, –16% to 190%), no change in the average GLP-1 response to hypoxia, and only a small trend toward an increase in GLP-1 levels 40 min postmeal (fasting, 15.7 ± 0.9 vs 15.9 ± 0.7 pmol·L–1; 20 min postmeal, 21.7 ± 0.9 vs 21.8 ± 1.2 pmol·L–1; 40 min postmeal, 19.5 ± 1.2 vs. 21.0 ± 1.2 pmol·L–1 for normoxia and hypoxia, respectively; p > 0.05 normoxia vs hypoxia). There was a correlation between SaO2 and leptin after the 17 h exposure (r = 0.45; p < 0.05), but no relation between SaO2 and GLP-1. These data confirm that leptin increases with hypoxic exposure in humans. Further study is needed to determine the influence of hypoxia and altitude on GLP-1 levels.

scholarly journals Influences of Hypoxia Exercise on Whole-Body Insulin Sensitivity and Oxidative Metabolism in Older Individuals

2019 ◽  
Vol 104 (11) ◽  
pp. 5238-5248 ◽  
Author(s):  
Kristine Chobanyan-Jürgens ◽  
Renate J Scheibe ◽  
Arne B Potthast ◽  
Markus Hein ◽  
Andrea Smith ◽  
...  
Keyword(s):  
Heart Rate ◽  
Insulin Sensitivity ◽  
Oxidative Metabolism ◽  
Perceived Exertion ◽  
Glucose Clamp ◽  
Normobaric Hypoxia ◽  
Metabolic Effects ◽  
Whole Body ◽  
Fraction Of Inspired Oxygen ◽  
Inspired Oxygen

Abstract Context Aging is a primary risk factor for most chronic diseases, including type 2 diabetes. Both exercise and hypoxia regulate pathways that ameliorate age-associated metabolic muscle dysfunction. Objective We hypothesized that the combination of hypoxia and exercise would be more effective in improving glucose metabolism than normoxia exercise. Design and Participants We randomized 29 older sedentary individuals (62 ± 6 years; 14 women, 15 men) to bicycle exercise under normobaric hypoxia (fraction of inspired oxygen = 15%) or normoxia (fraction of inspired oxygen = 21%). Intervention Participants trained thrice weekly for 30 to 40 minutes over 8 weeks at a heart rate corresponding to 60% to 70% of peak oxygen update. Main Outcome Measures Insulin sensitivity measured by hyperinsulinemic-euglycemic glucose clamp and muscle protein expression before and after hyperinsulinemic-euglycemic glucose clamp. Results Heart rate and perceived exertion during training were similar between groups, with lower oxygen saturation when exercising under hypoxia (88.7 ± 1.5 vs 96.2 ± 1.2%, P < 0.01). Glucose infusion rate after 8 weeks increased in both the hypoxia (5.7 ± 1.1 to 6.7 ± 1.3 mg/min/kg; P < 0.01) and the normoxia group (6.2 ± 2.1 to 6.8 ± 2.1 mg/min/kg; P = 0.04), with a mean difference between groups of –0.44 mg/min/kg; 95% CI, –1.22 to 0.34; (P = 0.25). Markers of mitochondrial content and oxidative capacity in skeletal muscle were similar after training in both groups. Changes in Akt phosphorylation and glucose transporter 4 under fasting and insulin-stimulated conditions were not different between groups over time. Conclusions Eight weeks of hypoxia endurance training led to similar changes in insulin sensitivity and markers of oxidative metabolism compared with normoxia training. Normobaric hypoxia exercise did not enhance metabolic effects in sedentary older women and men beyond exercise alone.

scholarly journals Influence of Dietary Nitrate Supplementation on High-Intensity Intermittent Running Performance at Different Doses of Normobaric Hypoxia in Endurance-Trained Males

2020 ◽  
pp. 1-8
Author(s):  
George P. Robinson ◽  
Sophie C. Killer ◽  
Zdravko Stoyanov ◽  
Harri Stephens ◽  
Luke Read ◽  
...  
Keyword(s):  
High Intensity ◽  
Arterial Oxygen Saturation ◽  
Normobaric Hypoxia ◽  
Arterial Oxygen ◽  
Altitude Training ◽  
Beetroot Juice ◽  
Running Performance ◽  
Fraction Of Inspired Oxygen ◽  
Inspired Oxygen ◽  
Different Doses

This study investigated whether supplementation with nitrate-rich beetroot juice (BR) can improve high-intensity intermittent running performance in trained males in normoxia and different doses of normobaric hypoxia. Eight endurance-trained males (, 62 ± 6 ml·kg−1·min−1) completed repeated 90 s intervals at 110% of peak treadmill velocity, from an initial step incremental test, interspersed by 60 s of passive recovery until exhaustion (Tlim). Participants completed the first three experimental trials during days 3, 5, and 7 of BR or nitrate-depleted beetroot juice (PLA) supplementation and completed the remaining experimental visits on the alternative supplement following at least 7 days of washout. The fraction of inspired oxygen during visits 1–3 was either 0.209, 0.182, or 0.157, equivalent to an altitude of 0, 1,200, and 2,400 m, respectively, and this order was replicated on visits 4–6. Arterial oxygen saturation declined dose dependently as fraction of inspired oxygen was lowered (p < .05). Plasma nitrite concentration was higher pre- and postexercise after BR compared with PLA supplementation (p < .05). There was no difference in Tlim between PLA and BR at 0 m (445 [324, 508] and 410 [368, 548] s); 1,200 m (341 [270, 390] and 332 [314, 356] s); or 2,400 m (233 [177, 373] and 251 [221, 323] s) (median and [interquartile range]; p > .05). The findings from this study suggest that short-term BR supplementation does not improve high-intensity intermittent running performance in endurance-trained males in normoxia or at doses of normobaric hypoxia that correspond to altitudes at which athletes typically train while on altitude training camps.

Pronation Technique in ARDS Patients

ABOUTOPEN ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 21-23
Author(s):  
Raffaele Di Fenza ◽  
Hedwige Gay ◽  
Martina Favarato ◽  
Isabella Fontana ◽  
Roberto Fumagalli
Keyword(s):  
Intensive Care ◽  
Intensive Care Units ◽  
Distress Syndrome ◽  
Daily Practice ◽  
Volume Distribution ◽  
Intensive Care Unit Staff ◽  
Safe Technique ◽  
Fraction Of Inspired Oxygen ◽  
And Diffusion ◽  
Inspired Oxygen

In severe acute respiratory distress syndrome (ARDS), characterized by the ratio of arterial partial pressure of oxygen over fraction of inspired oxygen (P/F) less than 150 mm Hg, pronation cycles are the only intervention that showed improved survival, in combination with protective ventilation. The physiological advantages of performing pronation cycles, such as the improvement of oxygenation, better tidal volume distribution with increased involvement of dorsal regions, and easier drainage of secretions, overcome the possible complications, that is, endotracheal tube occlusion or misplacement, pressure ulcers, and brachial plexus injury. However, the incidence of complications is dramatically lower in intensive care units with expertise, adopting prone positioning in daily practice. In this video we are proposing step by step an easy and ergonomic technique to perform pronation maneuvers in patients with severe ARDS. Recent literature suggests that a high percentage of these patients are treated without undergoing pronation cycles. The main purpose of this video is to help increase the number of intensive care units worldwide commonly performing pronation cycles in patients that have indications to be pronated, in order to decrease healthcare burden and costs directly caused by ARDS. Proper intensive care unit staff training is fundamental in minimizing the risks associated with the maneuver for both patients and operators; and diffusion of a safe technique encouraging the operators is the second main purpose of this video.

scholarly journals Nebulized in-line endotracheal dornase alfa and albuterol administered to mechanically ventilated COVID-19 patients: a case series

2020 ◽  
Vol 26 (1) ◽  
Author(s):  
Andrew G. Weber ◽  
Alice S. Chau ◽  
Mikala Egeblad ◽  
Betsy J. Barnes ◽  
Tobias Janowitz
Keyword(s):  
Case Series ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Dornase Alfa ◽  
Extracellular Traps ◽  
Dnase 1 ◽  
Fraction Of Inspired Oxygen ◽  
Oxygen Requirements ◽  
Inspired Oxygen ◽  
Ventilated Patients

Abstract Background Mechanically ventilated patients with COVID-19 have a mortality of 24–53%, in part due to distal mucopurulent secretions interfering with ventilation. DNA from neutrophil extracellular traps (NETs) contribute to the viscosity of mucopurulent secretions and NETs are found in the serum of COVID-19 patients. Dornase alfa is recombinant human DNase 1 and is used to digest DNA in mucoid sputum. Here, we report a single-center case series where dornase alfa was co-administered with albuterol through an in-line nebulizer system. Methods Demographic and clinical data were collected from the electronic medical records of five mechanically ventilated patients with COVID-19—including three requiring veno-venous extracorporeal membrane oxygenation—treated with nebulized in-line endotracheal dornase alfa and albuterol, between March 31 and April 24, 2020. Data on tolerability and response were analyzed. Results The fraction of inspired oxygen requirements was reduced for all five patients after initiating dornase alfa administration. All patients were successfully extubated, discharged from hospital and remain alive. No drug-associated toxicities were identified. Conclusions Results suggest that dornase alfa will be well-tolerated by patients with severe COVID-19. Clinical trials are required to formally test the dosing, safety, and efficacy of dornase alfa in COVID-19, and several have been recently registered.

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