Hypoxic Challenge Testing Research Articles

Can resting lung function predict the response of a person living with motor neuron disease to a hypoxic challenge test?

People living with MND (PlwMND) are at risk of altitude-related hypoxia during flight. The Hypoxic Challenge Test (HCT) determines whether in-flight oxygen is required but can be expensive and inaccessible. To assist with travel recommendations, we investigated the relationship between altitude simulation-induced hypoxemia and baseline lung function. Retrospective audit of clinical database of PlwMND who had HCT and lung function. Pearson's correlation assessed relationships between oxygen saturation at altitude (AltSpO2) and lung function. Univariate logistic regression analysis and receiver operator characteristic (ROC) curves determined associations between lung function and HCT pass or fail. Between 2004-2023, 50 PlwMND were identified (median (IQR) diagnosis to HCT = 11.6 (16.9) months, mean ± SD forced vital capacity (FVC) = 2.4 ± 0.9 liters). Ten patients dropped below 85% SpO2 during testing (HCT fail). Baseline SpO2 was associated with AltSpO2 (r = 0.64) and predicted HCT pass or fail (OR 2.0 [95% CI 1.2-3.4], area under ROC curve (AUC) =0.8 [0.6-1.0]), as did FVC (AUC = 0.8 [0.6-0.9]). PlwMND with a FVC > 2.7L or a resting SpO2 > 97% are likely to pass HCT, whereas all those with FVC < 1L and SpO2 < 92% failed. PlwMND with FVC >2.7L or SpO2 >97% are unlikely to require oxygen or ventilatory supports for airline travel. A FVC below 2.7L will require a HCT to confidently determine HCT outcome, with testing still required for FVC <1L or baseline SpO2 <92%, to provide evidence to the airlines for in-flight respiratory support.

Retrospective analysis of referrals for hypoxic challenge testing in children born preterm

IntroductionChildren with a history of bronchopulmonary dysplasia (BPD) may be at risk of hypoxaemia at altitude, such as during air travel. We have performed preflight hypoxic challenge testing (HCT) since...

'It gives me more freedom': Family perspectives on travelling with children on nocturnal ventilation.

Children with neuromuscular weakness or central hypoventilation often require nocturnal ventilation. Children with these conditions are living longer and the numbers of children affected are increasing. The challenges associated with managing ventilation at home have been documented; however, there has been limited investigation into accessing wider experiences such as travel. Air travel, in particular, may be considered challenging for children with these conditions because oxygen levels are lower in airplane cabins than at sea levels. We sought to understand experiences of and attitudes towards travel amongst families of children using nocturnal ventilation for neuromuscular weakness or central hypoventilation. Two semi-structured interviews were conducted amongst participants enrolled in a trial of a new pre-flight assessment of their tolerance of reduced oxygen levels during flight (known as a hypoxic challenge test). Children participating in the trial were aged 19 months to 18 years. Parents were interviewed and provided proxy views for younger children, and older children were encouraged to present their own views during these interviews. One interview was conducted immediately after the assessment, and a second 3 months later. Data were analysed utilising the framework approach to thematic analysis. Seventeen families participated in the first interview with 14 of these families completing the follow-up interview. Three further families participated in the follow-up interview only. Here, we report three themes relating to participant experience of travel and how this is impacted by their condition. The three themes and their sub-themes were (1) insight into children's lives: hospital attendances, gaining knowledge and confidence, and child as a person; (2) travelling with your child: planes, trains and automobiles, rules of air travel, and uncertainty; and (3) the meaning of travel: normalisation, connection to extended family, expanded experiences, and freedom and equality. This population of children and their families aspire to travel but face challenges from clinical and social barriers. It is essential that we further our understanding of the physiological, social and cultural aspects of their experience to facilitate their access to broadened life experiences.

Fitness to fly for children and adolescents after Fontan palliation.

At cruising altitude, the cabin pressure of passenger aircraft needs to be adjusted and, therefore, the oxygen content is equivalent to ambient air at 2,500 masl, causing mild desaturation and a rising pulmonary vascular resistance (PVR) in healthy subjects. For Fontan patients with passive pulmonary perfusion, a rising PVR can cause serious medical problems. The purpose of this fitness to fly investigation (FTF) is to assess the risk of air travel for children and adolescents after Fontan palliation. We investigated 21 Fontan patients [3-14y] in a normobaric hypoxic chamber at a simulated altitude of 2,500 m for 3 h. Oxygen saturation, heart rate, and regional tissue saturation in the forehead (NIRS) were measured continuously. Before entering the chamber, after 90 and 180 min in the hypoxic environment, blood gas analysis and echocardiography were performed. Heart rate and blood pressure did not show significant intraindividual changes. Capillary oxygen saturation (SaO2) decreased significantly after 90 min by a mean of 5.6 ± 2.87% without further decline. Lactate, pH, base excess, and tissue saturation in the frontal brain did not reach any critical values. In the case of open fenestration between the tunnel and the atrium delta, P did not increase, indicating stable pulmonary artery pressure. All 21 children finished the investigation successfully without any adverse events, so flying short distance seems to be safe for most Fontan patients with good current health status. As the baseline oxygen saturation does not allow prediction of the maximum extent of desaturation and adaption to a hypoxic environment takes up to 180 min, the so-called hypoxic challenge test is not sufficient for these patients. Performing an FTF examination over a period of 180 min allows for risk assessment and provides safety to the patients and their families, as well as the airline companies.

ERS International Congress 2022: highlights from the Paediatrics Assembly.

This review has been prepared by the Early Career Members and Chairs of the European Respiratory Society (ERS) Assembly 7: Paediatrics. We here summarise the highlights of the advances in paediatric respiratory research presented at the ERS International Congress 2022. The eight scientific groups of this Assembly cover a wide range of research areas, including respiratory physiology and sleep, asthma and allergy, cystic fibrosis (CF), respiratory infection and immunology, neonatology and intensive care, respiratory epidemiology, bronchology, and lung and airway developmental biology. Specifically, we report on abstracts presented at the congress on the effect of high altitude on sleep, sleep disorders, the hypoxic challenge test, and measurements of ventilation inhomogeneity. We discuss prevention of preschool wheeze and asthma, and new asthma medications. In children with CF, we describe how to monitor the effect of CF transmembrane conductance regulator modulator therapy. We present respiratory manifestations and chronic lung disease associated with common variable immunodeficiency. Furthermore, we discuss how to monitor respiratory function in neonatal and paediatric intensive care units. In respiratory epidemiology, we present the latest news from population-based and clinical cohort studies. We also focus on innovative and interventional procedures for the paediatric airway, such as cryotherapy. Finally, we stress the importance of better understanding the molecular mechanisms underlying normal and abnormal lung development.

Age matters: Comparing life-stage responses to diluted bitumen exposure in coho salmon (Oncorhynchus kisutch)

Millions of liters of diluted bitumen (dilbit), a crude oil product from Canada's oil sands region, is transported through critical Pacific salmon habitat each day. While the toxicity of the water-soluble fraction of dilbit (WSFd) to early life-stages of salmon is known, quantitative data on life-stage differences in sensitivity to WSFd is missing. To fill this knowledge gap, we exposed two juvenile life-stages of coho salmon (O. kisutch) in parallel to very low (parts per billion), environmentally-relevant concentrations of WSFd for acute (48 h) and sub-chronic (4 wk) durations. The relative sensitivities of the two life-stages (fry and parr) were assessed by comparing the timing and magnitude of biological responses using common organismal and molecular endpoints of crude oil exposure. A significant reduction in body condition occurred in both fry and parr after 4 wk exposure to WSFd. Both life-stages also experienced a concentration-dependent decrease in time-to-loss-of-equilibrium during a hypoxia challenge test at both 48 h and 4 wk of exposure. Although organismal responses were similar, molecular responses were distinct between life-stages. In general, unexposed fry had higher baseline values of hepatic phase I biotransformation indicators than unexposed parr, but induction of EROD activity and cyp1a mRNA expression in response to WSFd exposure was greater in parr than in fry. Neither gst nor hsp70 mRNA expression, markers of phase II biotransformation and cell stress, respectively, were reliably altered by WSFd exposure in either life-stage. Taken together, results of this study do not support differential sensitivities of coho fry and parr to WSFd. All the same, the potential for ontogenic differences in the expression and induction of phase I biotransformation need to be considered because age does matter for these endpoints if they are used as bioindicators of exposure in post-spill impact assessments.

Testing the hypoxia tolerance and hypoxic performance of fishes: A two-tier screening approach

With regional hypoxic episodes in the world’s oceans becoming more severe and more frequent, a valuable management need will be a screening protocol to characterize the full diversity of hypoxic robustness among fishes (defined here as their tolerance and performance). Yet, high-throughput screening protocols to deal with the almost 33,000 fish species have the potential to trade off convenience with the information depth normally provided with comprehensive but more time-consuming phenotyping protocols. As a solution, we propose a two-tier testing approach, one that combines a simple, rapid, cost-effective, and well-established hypoxia challenge test (a measure of hypoxic tolerance) with an individual-based hypoxic performance test that defines maximum aerobic capacity over a wide range of ambient water oxygen levels (a hypoxic performance curve). The later test would be performed on selected indicator species identified from the tolerance screening test. Here we describe the two methodological approaches for this two-tier approach using some existing data to illustrate the potential for their applications in marine science.

Exercise and hypoxia unmask pulmonary vascular disease and right ventricular dysfunction in a 10- to 12-week-old swine model of neonatal oxidative injury.

Prematurely born young adults who experienced neonatal oxidative injury (NOI) of the lungs have increased incidence of cardiovascular disease. Here, we investigated the long‐term effects of NOI on cardiopulmonary function in piglets at the age of 10–12 weeks. To induce NOI, term‐born piglets (1.81 ± 0.06 kg) were exposed to hypoxia (10–12% FiO2), within 2 days after birth, and maintained for 4 weeks or until symptoms of heart failure developed (range 16–28 days), while SHAM piglets were normoxia raised. Following recovery (>5 weeks), NOI piglets were surgically instrumented to measure haemodynamics during hypoxic challenge testing (HCT) and exercise with modulation of the nitric‐oxide system. During exercise, NOI piglets showed a normal increase in cardiac index, but an exaggerated increase in pulmonary artery pressure and a blunted increase in left atrial pressure – suggesting left atrial under‐filling – consistent with an elevated pulmonary vascular resistance (PVR), which correlated with the duration of hypoxia exposure. Moreover, hypoxia duration correlated inversely with stroke volume (SV) during exercise. Nitric oxide synthase inhibition and HCT resulted in an exaggerated increase in PVR, while the PVR reduction by phosphodiesterase‐5 inhibition was enhanced in NOI compared to SHAM piglets. Finally, within the NOI piglet group, prolonged duration of hypoxia was associated with a better maintenance of SV during HCT, likely due to the increase in RV mass. In conclusion, duration of neonatal hypoxia appears an important determinant of alterations in cardiopulmonary function that persist further into life. These changes encompass both pulmonary vascular and cardiac responses to hypoxia and exercise. Key points Children who suffered from neonatal oxidative injury, such as very preterm born infants, have increased risk of cardiopulmonary disease later in life.Risk stratification requires knowledge of the mechanistic underpinning and the time course of progression into cardiopulmonary disease.Exercise and hypoxic challenge testing showed that 10‐ to 12‐week‐old swine that previously experienced neonatal oxidative injury had increased pulmonary vascular resistance and nitric oxide dependency.Duration of neonatal oxidative injury was a determinant of structural and functional cardiopulmonary remodelling later in life.Remodelling of the right ventricle, as a result of prolonged neonatal oxidative injury, resulted in worse performance during exercise, but enabled better performance during the hypoxic challenge test.Increased nitric oxide dependency together with age‐ or comorbidity‐related endothelial dysfunction may contribute to predisposition to pulmonary hypertension later in life.

Assessing air travel safety in neuromuscular disease: standard versus prolonged hypoxic challenge tests.

The hypoxic challenge test (HCT) is used to evaluate safety for air travel in individuals with respiratory disease by breathing in 15% oxygen for 20min. Our aim was to determine if a prolonged HCT, lasting 120min, identified more individuals with neuromuscular disease at potential risk than the standard HCT lasting 20min. This was a cross-sectional study. All of the clinical testing took place at SickKids, Toronto, Canada. Patients were included in the study if they had a diagnosis of NMD, greater than 6years of age, resting oxygen saturation ≥ 94%, and partial pressure of carbon dioxide (pCO2) ≤ 45mmHg. Notable exclusion criteria were left ventricular ejection fraction < 30%, presence of a tracheostomy, and use of non-invasive ventilation for more than 12h daily. Participants underwent a standard HCT as well as the prolonged HCT on the same day. Twenty-three patients consented to the study. One patient was withdrawn because he was unable to follow the study procedures. The 22 study participants had a mean age of 14.9years (standard deviation (SD) of 5years). Seventeen (77%) participants were male. Two participants were withdrawn on the day of testing due to hypercapnia. Twenty participants completed the standard and prolonged HCTs. None of the participants had a positive standard or prolonged HCT. Our results suggest that performing a standard or prolonged HCT may, in fact, not be of clinical utility in individuals with less severe NMD.

Feasibility of a Hypoxic Challenge Test Under Noninvasive Ventilation Versus Oxygen in Neuromuscular Patients with Chronic Respiratory Insufficiency.

Ribeiro Baptista, Bruno, Morgane Faure, Gimbada Benny Mwenge, Capucine Morelot-Panzini, Christian Straus, Thomas Similowski, and Jésus Gonzalez-Bermejo. Feasibility of a hypoxic challenge test under noninvasive ventilation versus oxygen in neuromuscular patients with chronic respiratory insufficiency. High Alt Med Biol. 22:346-350, 2021. Background: The British Thoracic Society recommendations suggest that all patients with an oxygen saturation (SpO2) <85% during a hypoxic challenge test (HCT) should receive supplemental oxygen during air travel. However, neuromuscular patients already using ventilatory support are a specific population and noninvasive ventilation (NIV) during a flight could be an alternative to oxygen for hypoxemia correction, through the augmentation of ventilation. Methods: We conducted a comparative, observational study of neuromuscular patients with chronic respiratory failure, requiring nocturnal mechanical ventilation, who were planning to take a flight. HCT was performed with a ventilated canopy placed over the patient's head or the patient's home ventilator. The positive threshold value chosen for the HCT was <90% SpO2. Results: HCTs were performed on 13 adults with neuromuscular diseases using their home ventilator. Among them, 11 had a positive HCT. For all patients with a positive test, hypoxemia was corrected (SpO2 to >90%) by oxygen therapy (+9 [6-12]%, p = 0.0029). Patient's home ventilator also significantly increased the SpO2 by 8 [7-12]% (p = 0.016). Correction of SpO2 during the HCT was not different between oxygen and NIV. NIV was associated with a significant decrease in pressure, end tidal, carbon dioxide (PetCO2) (-10 [-16 to -7.5] mmHg, p = 0.04). Conclusions: The performance of an adapted HCT in home-ventilated patients with a neuromuscular pathology may be useful in a personalized treatment plan for air travel. NIV can be a new alternative to oxygen therapy for neuromuscular patients planning to take a flight.

Assessment of portable oxygen concentrators in infants undergoing hypoxic challenge testing. A randomised controlled crossover trial.

Due to reduced PaO2 , aircrafts at cruising altitudes are pressurised to a cabin altitude of 2438m, equivalent to breathing FiO2 0.15. Portable oxygen concentrators (POCs) are approved for onboard oxygen supply with lack of evidence, especially in infants. We assessed POCs (continuous-flow cPOC vs. pulsed-flow pPOC) under simulated altitude conditions performing Hypoxic Challenge Testing (HCT). In a randomised controlled crossover trial, we included patients <1year born prematurely. In incidents of hypoxia (SpO2 ≤85%), oxygen was administered through POC. In patients with a positive hypoxia reversal, HCT was repeated 24hours later. If hypoxia occurred during the second testing, oxygen was given using the alternative POC. We randomised 26 patients; 22 patients received allocated intervention (4 dropped out). Mean gestational age 30.4weeks, mean corrected age 38.2weeks. Both POCs achieved immediate hypoxia reversal in all cases (SpO2 cPOC/pPOC 98%/99.4% (95%CI -2.91, 0.01)) without any adverse events. No significant difference was observed in patients with BPD. Both POCs generated sufficient oxygen to reverse HCT induced hypoxia. Although pPOCs are not recommended in paediatric age, our data suggest their effectiveness even in neonates without any associated adverse events. Future research on pPOCs safety is required to establish recommendations for their use.

Fit for high altitude: are hypoxic challenge tests useful?

&#x0D; &#x0D; &#x0D; Altitude travel results in acute variations of barometric pres- sure, which induce different degrees of hypoxia, changing the gas contents in body tissues and cavities. Non ventilated air containing cavities may induce barotraumas of the lung (pneumothorax), sinuses and middle ear, with pain, vertigo and hearing loss. Commercial air planes keep their cabin pres- sure at an equivalent altitude of about 2,500 m. This leads to an increased respiratory drive which may also result in symp- toms of emotional hyperventilation. In patients with pre- existing respiratory pathology due to lung, cardiovascular, pleural, thoracic neuromuscular or obesity-related diseases (i.e. obstructive sleep apnea) an additional hypoxic stress may induce respiratory pump and/or heart failure. Clinical pre-altitude assessment must be disease-specific and it includes spirometry, pulsoximetry, ECG, pulmonary and sys- temic hypertension assessment. In patients with abnormal values we need, in addition, measurements of hemoglobin, pH, base excess, PaO2, and PaCO2 to evaluate whether O2- and CO2-transport is sufficient.&#x0D; Instead of the hypoxia altitude simulation test (HAST), which is not without danger for patients with respiratory insuffi- ciency, we prefer primarily a hyperoxic challenge. The supple- mentation of normobaric O2 gives us information on the acute reversibility of the arterial hypoxemia and the reduc- tion of ventilation and pulmonary hypertension, as well as about the efficiency of the additional O2-flow needed during altitude exposure. For difficult judgements the performance of the test in a hypobaric chamber with and without supple- mental O2-breathing remains the gold standard. The increas- ing numbers of drugs to treat acute pulmonary hypertension due to altitude exposure (acetazolamide, dexamethasone, nifedipine, sildenafil) or to other etiologies (anticoagulants, prostanoids, phosphodiesterase-5-inhibitors, endothelin receptor antagonists) including mechanical aids to reduce periodical or insufficient ventilation during altitude exposure (added dead space, continuous or bilevel positive airway pressure, non-invasive ventilation) call for further randomized controlled trials of combined applications.&#x0D; &#x0D; &#x0D;

Postmenstrual age at discharge in premature infants with and without ventilatory pattern instability.

To determine if ventilatory pattern instability, manifested as periodic breathing (PB) during physiologic challenge testing, affects postmenstrual age (PMA) at discharge. Eighty infants underwent challenge testing at 36 weeks PMA. Infants breathing supplemental O2 received a room air challenge (RAC, N = 51); those breathing ambient air underwent a hypoxic challenge test (HCT, N = 29). Infants were assigned one of four ventilatory control phenotypes based on the presence or absence of PB during their test, and if they passed or failed because of hypoxemia during the challenge test. There were no clinical or demographic differences between groups. Infants who passed their challenge testing were, on average, discharged 1.6 weeks sooner than those who failed. The groups of ventilatory control phenotypes differed in PMA at discharge (p = 0.0020), but those with PB were younger by PMA at discharge. Ventilatory pattern instability did not prolong time to discharge. Passing either challenge was associated with earlier discharge, suggesting these tests might identify infants who can have nasal cannula support removed and be safely discharged sooner. Most of the infants who failed their challenge tests with PB were receiving nasal cannula support. Nasal cannula support may be not only treating hypoxemia due to bronchopulmonary dysplasia (BPD), but also mitigating their ventilatory pattern instability.

Effects of Agricultural Pesticides in Aquafeeds on Wild Fish Feeding on Leftover Pellets Near Fish Farms.

Screening has revealed that modern-day feeds used in Atlantic salmon aquaculture might contain trace amounts of agricultural pesticides. To reach slaughter size, salmon are produced in open net pens in the sea. Uneaten feed pellets and undigested feces deposited beneath the net pens represent a source of contamination for marine organisms. To examine the impacts of long-term and continuous dietary exposure to an organophosphorus pesticide found in Atlantic salmon feed, we fed juvenile Atlantic cod (Gadus morhua), an abundant species around North Atlantic fish farms, three concentrations (0.5, 4.2, and 23.2 mg/kg) of chlorpyrifos-methyl (CPM) for 30 days. Endpoints included liver and bile bioaccumulation, liver transcriptomics and metabolomics, as well as plasma cholinesterase activity, cortisol, liver 7-ethoxyresor-ufin-O-deethylase activity, and hypoxia tolerance. The results show that Atlantic cod can accumulate relatively high levels of CPM in liver after continuous exposure, which is then metabolized and excreted via the bile. All three exposure concentrations lead to significant inhibition of plasma cholinesterase activity, the primary target of CPM. Transcriptomics profiling pointed to effects on cholesterol and steroid biosynthesis. Metabolite profiling revealed that CPM induced responses reflecting detoxification by glutathione-S-transferase, inhibition of monoacylglycerol lipase, potential inhibition of carboxylesterase, and increased demand for ATP, followed by secondary inflammatory responses. A gradual hypoxia challenge test showed that all groups of exposed fish were less tolerant to low oxygen saturation than the controls. In conclusion, this study suggests that wild fish continuously feeding on leftover pellets near fish farms over time may be vulnerable to organophosphorus pesticides.

Choosing an Adequate Test to Determine Fitness for Air Travel in Obese Individuals

Air travel is physically demanding and, because obesity is rising, physicians increasingly need to assess whether such patients can fly safely. Our aim was to compare the diagnostic accuracy of two routinely used exercise tests, 50-m walk test and 6-min walk test, and hypoxic challenge testing (HCT) in obese individuals. We further explored the diagnostic potential of perceived dyspnea as measured with the Borg scale because this is often recorded subsequent to walking tests. In this prospective study, we examined 21 obese participants (10 women, age 51 ± 15 [mean ± SD], BMI 36 ± 5 kg/m2). The most prevalent comorbidity was COPD (n= 11). The reference standard for in-flight hypoxia, defined as oxygen saturation below 90%, was established in an altitude chamber. Diagnostic accuracy of each index test was estimated by area under the receiver operating characteristic curve (AUC). Of the 21 participants, 13 (9 with COPD) were identified with in-flight hypoxia. HCT was the only test separating the reference groups significantly with AUC 0.87 (95%CI, 0.62-0.96). Neither of the walking tests predicted noticeably above chance level: 50m walk test had an AUC of 0.63 (0.36-0.84) and 6MWT had an AUC of 0.64 (0.35-0.86). We further observed good prognostic ability of subjective dyspnea assessment when recorded after 6MWT with an AUC of 0.80 (0.55-0.93). In-flight hypoxia in obese individuals can be predicted by HCT but not by simple walking tests.

A Protocol to Evaluate Retinal Vascular Response Using Optical Coherence Tomography Angiography.

IntroductionOptical coherence tomography angiography (OCT-A) is a novel diagnostic tool with increasing applications in ophthalmology clinics that provides non-invasive high-resolution imaging of the retinal microvasculature. Our aim is to report in detail an experimental protocol for analyzing both vasodilatory and vasoconstriction retinal vascular responses with the available OCT-A technology.MethodsA commercial OCT-A device was used (AngioVue®, Optovue, CA, United States), and all examinations were performed by an experienced technician using the standard protocol for macular examination. Two standardized tests were applied: (i) the hypoxia challenge test (HCT) and (ii) the handgrip test, in order to induce a vasodilatory and vasoconstriction response, respectively. OCT-A was performed at baseline conditions and during the stress test. Macular parafoveal vessel density of the superficial and deep plexuses was assessed from the en face angiograms. Statistical analysis was performed using STATA v14.1 and p < 0.05 was considered for statistical significance.ResultsTwenty-four eyes of 24 healthy subjects (10 male) were studied. Mean age was 31.8 ± 8.2 years (range, 18–57 years). Mean parafoveal vessel density in the superficial plexus increased from 54.7 ± 2.6 in baseline conditions to 56.0 ± 2.0 in hypoxia (p < 0.01). Mean parafoveal vessel density in the deep plexuses also increased, from 60.4 ± 2.2 at baseline to 61.5 ± 2.1 during hypoxia (p < 0.01). The OCT-A during the handgrip test revealed a decrease in vessel density in both superficial (55.5 ± 2.6 to 53.7 ± 2.9, p < 0.001) and deep (60.2 ± 1.8 to 56.7 ± 2.8, p < 0.001) parafoveal plexuses.DiscussionIn this work, we detail a simple, non-invasive, safe, and non-costly protocol to assess a central nervous system vascular response (i.e., the retinal circulation) using OCT-A technology. A vasodilatory response and a vasoconstriction response were observed in two physiologic conditions—mild hypoxia and isometric exercise, respectively. This protocol constitutes a new way of studying retinal vascular changes that may be applied in health and disease of multiple medical fields.

Assessment of Portable Oxygen Concentrators in Infants Undergoing Hypoxic Challenge Testing.

Assessment of Portable Oxygen Concentrators in Infants Undergoing Hypoxic Challenge Testing.

Nutritional programming by dietary carbohydrates in European sea bass larvae: Not always what expected at juvenile stage

Optimizing the metabolic use of these carbohydrate-rich plant products in fish feeds could be achieved through nutritional programming strategies of fish larvae. The present study aims at testing the long-term effect of an early-life high-carbohydrate nutritional (34% of starch in the feed) stimulus in European sea bass (Dicentrarchus labrax), by examining several biochemical and molecular parameters involved in carbohydrate metabolism in sea bass larvae and juveniles, compared to a control group fed standard larval regime (phase 1). As awaited, specific activities of digestive enzymes, from pancreatic and intestinal segments, involved in glucide digestion (amylase, sucrase) were enhanced together with an up-regulation of glucokinase gene and down-regulation of glucose 6-phosphatase gene assayed in whole-body larvae fed the high-carbohydrate diet. However, this regime also induced a significant lowering in growth and survival.Six months later, while all the fish were fed the same standard diet, a first hypoxia challenge test allowed to distinguish two groups of fish according their nutritional history at larval stage: fish had been fed high-carbohydrate regime performed much better than control. When fed again during 2 months with a high-carbohydrate diet (phase 2), such larval nutritional history did not confer any subsequent “advantage” or “disadvantage” in term of carbohydrate metabolism and growth. A second hypoxia challenge test performed just after phase 2, did not confirm the first one. All together our results indicated that the larval conditioning may fade over time. It was suggested to apply regular nutritional stress pulses during the first months of fish life.

Time to improve training for hypoxic pulmonary challenge test

Time to improve training for hypoxic pulmonary challenge test

Moderate hypoxia but not warming conditions at larval stage induces adverse carry-over effects on hypoxia tolerance of European sea bass (Dicentrarchus labrax) juveniles

Environmental conditions, to which organisms are exposed during all their life, may cause possible adaptive responses with consequences in their subsequent life-history trajectory. The objective of this study was to investigate whether ecologically relevant combinations of hypoxia (40% and 100% air saturation) and temperature (15° and 20 °C), occurring during the larval period of European sea bass larvae (Dicentrarchus labrax), could have long-lasting impacts on the physiology of resulting juveniles. Hypoxic challenge tests were performed over one year to give an integrative evaluation of physiological performance. We revealed that juvenile performance was negatively impacted by hypoxia but not by the thermal conditions experienced at larval stage. This impact was related to the prevalence of opercular abnormalities. The present study indicates that exposure to a moderate hypoxia event during larval stage may have adverse carry-over effects, which could compromise fitness and population recruitment success.