Moderate Altitude Research Articles

Ultrasound reference values for the calcaneus of children and adolescents at moderate altitudes in Peru

Objectivea) Establish reference values for bone parameters by using the speed of sound (SOS, m/s) of broadband ultrasound attenuation (BUA, dB/MHz) and establish a bone quality index (BQI=αSOS+βBUA) for children and adolescents living in a region of moderate altitude, b) compare bone parameters with an international standard (with different ethnic, socio-economic, and lifestyle backgrounds) by using ultrasound of the calcaneus (heel bone) (QUS). MethodsA descriptive cross-sectional study was carried out with children and adolescents between the ages of 6.0 and 16.9 years old. The sample was selected randomly. A total of 1322 subjects were studied. Weight, height, and bone parameters, using ultrasound of the calcaneus, were evaluated SOS, BUA, and BQI. Body Mass Index BMI was calculated. ResultsThe average age of males was 11.44±0.35 years old, and for females, it was 11.43±0.35 years old. The students in this research showed slightly higher values of SOS, BUA, and BQI for both sexes when compared with the international reference (the 50th percentile). Percentiles were generated (P3, P10, P25, P50, P75, P90, and P97) using the LMS method [median (M), standard deviation (S), and power of the Box-Cox transformation (L)] by age and sex. ConclusionThe students living at a moderate altitude showed slightly higher values in bone parameters in relation to the international reference. This pattern depicted a population with a better state of bone health. The proposed percentiles may be used to categorize adequate to at risk bone parameters based on age and sex.

Validation of Maximal, Submaximal, and Nonexercise Indirect [Formula: see text]O2max Estimations at 2600 m Altitude.

Aim: To study the criterion validity of three indirect maximal oxygen uptake ([Formula: see text]O2max) assessment equations at altitude. Methods: We studied 64 young adults (53% men) at Bogota, Colombia (2600 m altitude). Direct [Formula: see text]O2max was measured by indirect calorimetry using a maximal incremental treadmill protocol. Indirect [Formula: see text]O2max was estimated by two exercise field tests (the 20-m shuttle-run test [20-MST] and the 2-km walking test (UKK)) and one nonexercise method (the perceived functional ability-physical activity rating questionnaire [PFA-PAR]). Altitude-adjusted PFA-PAR was estimated as a 13% linear reduction in PFA-PAR. We calculated Lin concordance coefficients (LCC) and standard error of the estimates (SEEs), and we performed Bland-Altman analyses for each indirect method. Results: Mean [Formula: see text]O2max was 41.2 ± 5.8 mL/kg/min in men and 32.2 ± 3.6 mL/kg/min in women. We found the highest agreement with direct [Formula: see text]O2max for the 20-MST (LCC = 0.79, SEE = 3.91 mL/kg/min), followed in order by the altitude-adjusted PFA-PAR (LCC = 0.71, SEE = 4.12 mL/kg/min), the UKK (LCC = 0.67, SEE = 5.48 mL/kg/min), and the unadjusted PFA-PAR (LCC = 0.57, SEE = 4.75 mL/kg/min). The unadjusted PFA-PAR tended to overestimate [Formula: see text]O2max, but Bland-Altman analysis showed that this bias disappeared after altitude adjustment. Conclusion: Several maximal, submaximal, and nonexercise methods provide estimates of [Formula: see text]O2max with acceptable validity for use in epidemiological studies of populations living at moderate altitude.

Aerobic Exercise Performance During Load Carriage and Acute Altitude Exposure.

Coffman, KE, Luippold, AJ, Salgado, RM, Heavens, KR, Caruso, EM, Fulco, CS, and Kenefick, RW. Aerobic exercise performance during load carriage and acute altitude exposure. J Strength Cond Res 34(4): 946-951, 2020-This study quantified the impact of combined load carriage and acute altitude exposure on 5-km running time-trial (TT) performance and self-selected pacing strategy. Furthermore, this study developed a velocity prediction tool (nomogram) for similar aerobic exercise tasks performed under various combinations of altitude and load stress. Nine volunteers (6M/3F, age: 24 ± 7 years, height: 171 ± 6 cm, body mass: 72 ± 7 kg, and V[Combining Dot Above]O2peak: 50.5 ± 5.2 ml·min·kg) completed a randomized, repeated-measures design protocol. Volunteers performed 3 familiarization (FAM) trials at sea level (SL; 250 m) with no-load carriage. Experimental testing included 3 self-paced, blinded 5-km running TT on a treadmill while carrying a 30% body mass external load at SL, moderate altitude (MA; 2000 m), and high altitude (HA; 3000 m). At SL, load carriage resulted in a 36% decrement in 5-km exercise performance in comparison with FAM trials (43 ± 7 vs. 32 ± 3 minutes; p < 0.001). Time required to complete the 5-km distance while carrying an external load was increased by 11% when performed at HA vs. SL (48 ± 7 vs. 43 ± 7 minutes; p = 0.001). TT pace was not different among experimental conditions (load carriage at SL, MA, and HA) until after 1 km of the running distance had been completed. Heart rate was not different among experimental conditions throughout the entire TT (170 ± 17 b·min). These data quantify the anticipated reduction in aerobic exercise performance under various combinations of acute altitude exposure and load carriage conditions. The self-paced running TT approach used presently allowed for development of an altitude-load nomogram for use in recreational, occupational, or military settings.

Hypoxic Training Is Beneficial in Elite Athletes.

There is no doubt that many hypoxic conditions or prolonged exposures to altitude result in “biological costs of hypoxic adaptations that outweigh their benefits” (1), particularly in endurance athletes exposed to a) exercise-induced arterial hypoxemia leading to a larger decrease in VO2max and aerobic endurance; b) increased sympathetic activity and decreased baroreflex sensitivity; and c) increased pulmonary arterial pressure. There is also no doubt that sleeping in moderate altitude (2000-3000 m) as performed by the athletes using either live high-train high (LHTH) or live high-train low (LHTL) methods leads to periodic breathing, intermittent hypoxia (IH) and increase in desaturation periods; e.g. 3% oxygen desaturation index, but to a larger extent in hypobaric hypoxia (HH, real altitude) than in normobaric hypoxia (NH, simulated altitude), as shown at 2250 m (2). The three main questions debated in the present contrasting perspective are however different: 1. Are there any evidences showing if the “counteracting maladaptation” (reported above) outweigh the benefits of the different hypoxic methods at short- or long-term in elite athletes? ; 2. Are there any robust data supporting that hypoxic training is beneficial in elite athletes? ; 3. Contradictory, are there robust data showing that hypoxic training is not beneficial in elite athletes?

Evolution and Preservation of Venous Gas Emboli at Alternating High and Moderate Altitude Exposures.

INTRODUCTION: The evolution and preservation of venous gas emboli (VGE), as markers of decompression stress, were investigated during alternating high- and moderate altitude exposures, thus, simulating a fighter aircraft high-altitude flight, interrupted by refueling excursions to lower altitudes.METHODS: Eight men served as subjects during three normoxic simulated altitude exposures: High = 90 min at 24,000 ft; High-Low = three × 30 min at 24,000 ft, interspersed by two 30-min intervals at 15,000 ft; Low = 90 min at 15,000 ft. VGE scores were assessed by cardiac ultrasound, using a 5-grade scale. Respiratory nitrogen exchange was measured continuously using a modified closed-circuit electronic rebreather.RESULTS: Both High and High-Low induced persistent VGE, with no inter-condition difference either at rest [median (range): High: 1 (0-3), High-Low: 2 (0-3)] or during unloaded knee-bends [High: 3 (1-4), High-Low: 3 (0-4)], whereas VGE was considerably less in Low, both at rest [0 (0-1)] and during knee-bends [0 (0-2)]. In High-Low, VGE decreased temporarily during the 15,000-ft excursions, but resumed pre-excursion values upon return to 24,000 ft. During the final descent to ground level, VGE were more persistent following High-Low than High. In both High and Low, nitrogen was continuously washed out at altitude, whereas in High-Low, the washout at 24,000 ft was interrupted by nitrogen uptake at 15,000 ft.DISCUSSION: In normoxic conditions, long-duration flying at a cabin altitude of 24,000 ft is associated with substantial VGE occurrence, which is not abolished by intermittent excursions to a cabin altitude of 15,000 ft.Ånell R, Grönkvist M, Gennser M, Eiken O. Evolution and preservation of venous gas emboli at alternating high and moderate altitude exposures. Aerosp Med Hum Perform. 2020; 91(1):11-17.

Topographic variables to determine the diversity of woody species in the exclosure of Northern Ethiopia

Exclosures are established with the objective of rehabilitating degraded lands and restoring of woody vegetation. Various studies have been conducted to evaluate the success of exclosure on restoring woody species diversity. However, works focusing on the effect of topographic factors on woody species diversity are scarce. Understanding the factors that determine woody species diversity is important for management purposes. Therefore, this paper analyzes the effect of altitude, slope, and aspect as topographic variables on woody species diversity in Dawsura exclosure in northern Ethiopia. Data on species identity, abundance, slope, elevation and aspect were recorded from 58 sampling plots. Different diversity indices were used to analyze the data and one-way ANOVA and linear regression was conducted. There were a total of 34 woody species represented 15 families, of which 62% and 38% were trees and shrubs respectively. Altitude (r2 = 0.63, p = 0.000 and r = 0.794, p < 0.01) and slope (r2 = 0.57, p = 0.002 and r = 0.68, p < 0.01) correlated significantly and positively with Shannon diversity, whereas aspect (r2 = 0.12, p = 0.378 and r = 0.27, p > 0.05) did not correlate significantly with Shannon diversity. Woody species diversity at moderate (1.44) and high (1.85) altitudes was significantly different from that of low (0.86) altitude areas (p = 0.0013). Furthermore, significantly higher woody species diversity was recorded at steep slope (1.88) and moderately steep slope (1.62) areas as compared to the gentle slope (0.95) areas. No significant variation was observed in woody species diversity among the aspect categories (p > 0.05). The study concludes that woody species diversity is largely regulated by slope and altitude than aspect in the exclosure. We suggest other environmental and anthropogenic variables should be taken into consideration in future studies on woody species diversity.

Effect of a 16-Day Altitude Training Camp on 3,000-m Steeplechase Running Energetics and Biomechanics: A Case Study.

The purpose of this study was to investigate the effect of a 16-day training camp at moderate altitude on running energetics and biomechanics in an elite female 3,000-m steeplechase athlete (personal best: 9 min 36.15 s). The 16-day intervention included living and training at 1,600 m altitude. A maximal incremental test was performed at sea level to determine the maximal oxygen uptake (). Before (pre-) and after (post-) intervention, the participant performed a specific training session consisting of 10 × 400 m with 5 hurdles with oxygen uptake (), blood lactate, stride length and stride rate being measured. A video analysis determined take-off distance and landing around the hurdle (DTH and DLH), take-off velocity and landing around the hurdle (VTH and VLH), and the maximal height over the hurdle (MH). The results demonstrated that the mean maintained during the ten 400 m trials represented 84–86% of and did not change from pre- to post-intervention (p = 0.22). Mean blood lactate measured on the 6 last 400-m efforts increased significantly (12.0 ± 2.2 vs. 17.0 ± 1.6 mmol.l−1; p < 0.05). On the other hand, post-intervention maximal lactate decreased from 20.1 to 16.0 mmol.l−1. Biomechanical analysis revealed that running velocity increased from 5.12 ± 0.16 to 5.49 ± 0.19 m.s−1 (p < 0.001), concomitantly with stride length (1.63 ± 0.05 vs. 1.73 ± 0.06 m; p < 0.001). However, stride rate did not change (3.15 ± 0.03 vs. 3.16 ± 0.02 Hz; p = 0.14). While DTH was not significantly different from pre- to post- (1.34 ± 0.08 vs. 1.40 ± 0.07 m; p = 0.09), DLH was significantly longer (1.17 ± 0.07 vs. 1.36 ± 0.05 m; p < 0.01). VTH and VLH significantly improved after intervention (5.00 ± 0.14 vs. 5.33 ± 0.16 m.s−1 and 5.18 ± 0.13 vs. 5.51 ± 0.22 m.s−1, respectively; both p < 0.01). Finally, MH increased from pre- to post- (52.5 ± 3.8 vs. 54.9 ± 2.1 cm; p < 0.05). A 16-day moderate altitude training camp allowed an elite female 3,000-m steeplechase athlete to improve running velocity through a greater glycolytic—but not aerobic—metabolism.

Kinetics of Changes in Hemoglobin After Ascent to and Return from High Altitude

Decreased oxygen availability in sojourners requires adjustments in tissue oxygen supply, the most effective of which is an increase in the hemoglobin (Hb) concentration. It is achieved by two independent processes: a fast increase in Hb is achieved by decreasing plasma volume due to enhanced renal Na- and water excretion. A further but slow increase in Hb concentration is achieved by stimulation of erythropoiesis by mechanisms depending on stabilization of hypoxia-inducible factor 2α resulting in elevated levels of erythropoietin in blood. The magnitude of decrease in plasma volume and of stimulation of erythropoiesis depends on the degree and duration of exposure to hypoxia at high altitude. Upon descent from high to low altitude elevated O2-transport capacity is no longer needed. Thus, plasma volume can be restored and excess erythrocytes can be removed from circulation. This latter process is called erythrolysis. Its effectiveness seems to depend on the altitude to which individuals had been exposed. Whereas most of the excess erythrocytes seem to be removed from circulation within 1–2 weeks after a stay at altitudes > 3500 m, total Hb mass seems to remain elevated for up to 4 weeks when individuals had been exposed to more moderate altitudes, e.g. in the range of 2500 m. These are the altitudes where athletes typically perform altitude training. Thus, it appears that improved performance in the weeks after return from altitude training depends in part on maintaining elevated total Hb mass, which is known to increase aerobic capacity.

Altitude-induced effects on muscular metabolic stress and hypertrophy-related factors after a resistance training session

This study examined the acute effects of exposure to moderate altitude on factors associated with muscular adaptations following whole-body hypertrophy-oriented resistance training (R T) sessions. Thirteen resistance-trained males completed both counterbalanced standard hypertrophic R T sessions (3 sets × 10RM, 2 min rest) at moderate-altitude (H; 2320 m asl) and under normoxic conditions (N; <700 m asl). Participants rested 72 h between training sessions. Before and after the exercise session, blood samples were obtained for determination of metabolites and ions (lactate, inorganic phosphate, liquid carbon dioxide and calcium) and hormones (testosterone and growth hormone). Session-related performance and perception of effort (s-RPE) were also monitored. Results showed no meaningful differences in performance or s-RPE (8.5 ± 1.4 vs 8.6 ± 0.8 respectively for N and H; p = 0.603). All blood variables displayed statistically significant changes throughout the recovery period compared to basal levels (p < 0.05), except for the testosterone. However, no altitude effect was observed in maximal blood lactate, calcium or anabolic hormones (p > 0.05). The reduction observed in the liquid carbon dioxide concentration in H (21.11 ± 1.46 vs 16.19 ± 1.61 mmol·l−1) seems compatible with an increase in buffering capacity. Compared to N, inorganic phosphate displayed lower recovery values after the R T in H (2.89 ± 0.64 vs 2.23 ± 0.60 mg dl−1; p = 0.007). The results of this study do not support an accentuated effect of acute moderate terrestrial hypoxia on metabolic and hormonal factors linked to muscle growth during hypertrophic resistance training.

Increased Frequency of Thromboses Among Patients with Philadelphia (Ph) Negative Myeloproliferative Neoplasms in New Mexico: The Role of Prothrombotic Risk Factors

Introduction Thromboses are a common complication in patients with myeloproliferative neoplasms (MPN) and are reported to occur at a rate of 15- 20% at sea level. In the MPN-Thromboses spectrum which includes both arterial and venous thrombosis, cardiovascular disease (CVD) is noted to be the most common thrombotic event. JAK2 V617F is reported to be the most common driver mutation in MPNs and is associated with increased risk of thromboses. CALR and MPL are other mutations whose contribution to the thrombotic phenotype is not known. Chronic hypoxia from living in moderate or high altitude is reported to be an independent prothrombotic risk factor. The average elevation of New Mexico is 5,700 feet (1,740 meters) above sea level. The goal of this study is to evaluate the frequency of thromboses and prothrombotic risk factors in patients with MPN in patients in this distinct population. Methods We reviewed 134 patients, who were diagnosed with MPN in University of New Mexico Comprehensive Cancer Center between 2001 to 2019. A retrospective chart review was conducted to identify demographics, clinical and molecular risk factors for both arterial and venous thromboses. The mutation analyses for Janus Kinase 2 (JAK2), myeloproliferative leukemia (MPL) gene and calreticulin (CALR) gene were performed by polymerase chain reaction (PCR). Contingency table and logistic regression methods were applied to analyze and compare the distribution of the prothrombotic risk factors between the patients with and without thrombosis. Results In this study, 62 patients (47%) were diagnosed with ET, 47 patients (35%) with PV, and 22 patients (17%) with primary myelofibrosis (PMF). Seventy-five patients (56%) were females. Mean age at diagnosis was 62 years. 102 patients (77%) were living in the Albuquerque metropolitan area with an average elevation of 5312 feet above sea level and others were in areas with an elevation of 6000 feet or higher in New Mexico. Forty-four patients (33%) experienced either arterial (29) or venous thromboses (11) or both (4). A significant percentage (70.4%) of thrombotic events were either ischemic stroke or myocardial infarction. The patients with thromboses were predominantly males (21/36, 57%) while most patients without thromboses were females (56/90, 62%) with p=0.003. Twenty-one (53%) patients with thromboses had ET; however, a higher proportion of patients with PV (20/47, 42.5%) developed thromboses compared to ET or PMF (32.2% and 9% respectively). Also, a significant number of patients (32/44, 76%) with thromboses have JAK2 mutations while only 4 patients (9%) have CALR gene mutation. Although not statistically significant, CALR mutation was associated with lesser thrombotic events than other MPN patients. In univariate logistic regression analysis, PV and ET were significantly associated with increased thrombotic events. Patients with PV showed a 7.7-fold increase and patients with ET have a 5.1-fold increase in odds for thrombosis compared to patients with PMF (p=0.0365). Female gender was associated with decreased thrombotic risk with an odds ratio of 0.46 (p=0.0387). There was no significant difference between patients with and without thromboses, regarding other clinical characteristics such as age, previous aspirin use, leukocytosis, diabetes, hypertension, hyperlipidemia, obesity, and smoking. Conclusion An increased frequency of thromboses was observed among patients with Ph negative MPN in New Mexico which is significantly higher than previously reported studies. This strongly suggests the role of mild to moderate hypoxia as a contributing prothrombotic risk factor for MPN. The role of chronic hypoxia and its influence in thrombotic events in MPN need to be further evaluated in prospective studies. The decreased risk of thrombosis in females and patients harboring CALR mutations compared to other common mutations was consistent with other published studies. JAK2 mutation was not associated with an increased risk of thrombosis. Other genetic factors in this population were not evaluated in this study. Disclosures Arana Yi: Jazz Pharmaceuticals: Other: Advisory Board.

Effect of Temperature and Precipitation on the Vegetation Dynamics of High and Moderate Altitude Natural Forests in India

In the present study, the high-altitude vegetation dynamics of natural forest cover were analyzed to find the effect of local hydrology for about 10 years. Vegetation dynamics in four different topographical and climatic conditions in India were studied using normalized difference vegetation index (NDVI) data from vegetation sensor of SPOT satellite, and daily temperature and precipitation data from Asian Precipitation–Highly Resolved Observational Data Integration Towards Evaluation project. The main objective was to understand how and to what extent the natural vegetation reciprocates in various climatic conditions. First, the vegetation data was denoised by using empirical mode decomposition technique. The relation between the vegetation growth and hydrological parameters was studied to find the anomalies. Then, the wavelet analysis of the hydrological data was carried out to find the frequency and extent of the anomalies. Finally, nonparametric Mann–Kendall trend analysis and Sen’s slope analysis were applied to find the trend of the vegetation, temperature, and precipitation dynamics. Results indicate that the growth of the vegetation starts when the average temperature is 10 °C or higher. Beyond that the increase in temperature may have a negligible effect on growth of vegetation. The vegetation also shows positive change in monthly NDVI with the increase in precipitation depending forest type and local climate. However, with excessive rainfall, a declining trend in vegetation growth was observed. The NDVI data show positive trend in all four sites. In northern region, the temperature showed positive trend, while precipitation had negative trend. In eastern and western regions, the temperature had negative trend and precipitation had positive trend.

A Retrospective Analysis of Collegiate Athlete Blood Biomarkers at Moderate Altitude.

Morris, KL, Widstrom, L, Goodrich, J, Poddar, S, Rueda, M, Holliday, M, San Millian, I, and Byrnes, WC. A retrospective analysis of collegiate athlete blood biomarkers at moderate altitude. J Strength Cond Res 33(11): 2913-2919, 2019-Blood biomarkers are used to assess overall health and determine positive/negative adaptations to training/environmental stimuli. This study aimed to describe the changes in blood biomarkers in collegiate football (FB) (n = 31) and cross-country (XC) (n = 29; 16 women [FXC], 13 men [MXC]) athletes across a competitive season while training and living at a moderate altitude (1,655 m). This study used a database of previously collected hematological (complete blood count and serum ferritin) and muscle damage (lactate dehydrogenase and creatine kinase) blood biomarkers. Data were analyzed both within and between groups using linear mixed-model and variance component analyses, alpha = 0.05. All 3 groups had significant but different patterns of change in the measured biomarkers. Hematological blood biomarkers increased at different time points but remained within the normal reference ranges with greater between-subject vs. within-subject variability, suggesting no significant decrements to oxygen-carrying capacity across the season for FB, MXC, or FXC. Muscle damage biomarkers increased over time and exceeded the normal reference ranges, indicating cell damage pathology. However, it is also possible that the demands of training and competition might alter baseline values in these athletes, although this cannot be confirmed with the current experimental design. The patterns of change in the hematological and muscle damage biomarkers varied by sport discipline, suggesting that the training/competitive environments of these athletes influence these changes. Further studies should assess how much training, altitude, and nutrition influence these changes by using a more comprehensive set of biomarkers and related performance parameters.

Iron insufficiency diminishes the erythropoietic response to moderate altitude exposure.

The effects of iron stores and supplementation on erythropoietic responses to moderate altitude in endurance athletes were examined. In a retrospective study, red cell compartment volume (RCV) responses to 4 wk at 2,500 m were assessed in athletes with low (n = 9, ≤20 and ≤30 ng/mL for women and men, respectively) and normal (n = 10) serum ferritin levels ([Ferritin]) without iron supplementation. In a subsequent prospective study, the same responses were assessed in athletes (n = 26) with a protocol designed to provide sufficient iron before and during identical altitude exposure. The responses to a 4-wk training camp at sea level were assessed in another group of athletes (n = 13) as controls. RCV and maximal oxygen uptake (V̇o2max) were determined at sea level before and after intervention. In the retrospective study, athletes with low [Ferritin] did not increase RCV (27.0 ± 2.9 to 27.5 ± 3.8 mL/kg, mean ± SD, P = 0.65) or V̇o2max (60.2 ± 7.2 to 62.2 ± 7.5 mL·kg-1·min-1, P = 0.23) after 4 wk at altitude, whereas athletes with normal [Ferritin] increased both (RCV: 27.3 ± 3.1 to 29.8 ± 2.4 mL/kg, P = 0.002; V̇o2max: 62.0 ± 3.1 to 66.2 ± 3.7 mL·kg-1·min-1, P = 0.003). In the prospective study, iron supplementation normalized low [Ferritin] observed in athletes exposed to altitude (n = 14) and sea level (n = 6) before the altitude/sea-level camp and maintained [Ferritin] within normal range in all athletes during the camp. RCV and V̇o2max increased in the altitude group but remained unchanged in the sea-level group. Finally, the increase in RCV correlated with the increase in V̇o2max [(r = 0.368, 95% confidence interval (CI): 0.059-0.612, P = 0.022]. Thus, iron deficiency in athletes restrains erythropoiesis to altitude exposure and may preclude improvement in sea-level athletic performance.NEW & NOTEWORTHY Hypoxic exposure increases iron requirements and utilization for erythropoiesis in athletes. This study clearly demonstrates that iron deficiency in athletes inhibits accelerated erythropoiesis to a sojourn to moderate high altitude and may preclude a potential improvement in sea-level athletic performance with altitude training. Iron replacement therapy before and during altitude exposure is important to maximize performance gains after altitude training in endurance athletes.

Effects of acute exposure to moderate altitude on blood pressure and sleep breathing patterns

BackgroundAcute exposure to high altitude (>2500 m) is known to induce a rise in blood pressure (BP) and the appearance of sleep related breathing alterations, in particular central sleep apneas and periodic breathing. Little information is available on whether this is the case in humans also for acute exposure to moderate altitude (between 1500 and 2500 m). Aim of this study was to evaluate the effects of acute exposure of healthy volunteers to moderate altitude on conventional and ambulatory BP as well as on the frequency and severity of breathing alterations during sleep. MethodsForty-four healthy lowlanders underwent 24-hour ambulatory BP monitoring and nocturnal cardio-respiratory sleep study at sea level and during acute (1–2 days after arrival) exposure to moderate altitude (2035 m, Sestriere, Italy). The key variables investigated included average systolic and diastolic BP and heart rate over daytime, night-time and 24 h, the frequency of obstructive and central apneas/hypopnoeas and the behaviour of oxygen saturation during sleep. ResultsCompared to sea level, during moderate altitude exposure mean systolic/diastolic BP increased significantly during daytime (respectively from 125.6 ± 10.9 to 130.6 ± 12.3, p = 0.0032 and from 78.8 ± 6.7 to 81.8 ± 7.7 mmHg, p = 0.0048) and during night-time (respectively from 102.4 ± 12.4 to 107.4 ± 12.7, p = 0.0028, and from 62.0 ± 8.2 to 65.8 ± 8.2 mmHg, p = 0.0014), with no change in nocturnal BP dipping. BP increase was more evident in participants aged over 40 years. Apnea-hypopnea index (AHI) increased from 1.60 (0.40–2.90) to 5.4 (2.90–10.60), p < 0.0001), mainly because of increasing frequency of hypopneas and central apneas, in particular in males aged over 40 years. No association was found between size of BP changes and AHI. ConclusionOur results indicate that in healthy subjects even exposure to moderate altitude may induce significant, although mild, changes in ambulatory BP and in respiratory patterns during sleep with gender and age-related differences. Further studies are needed to explore the clinical relevance of these findings.

Mean Propulsive Velocity Is a Viable Method for Adjusting the Resistance-Training Load at Moderate Altitude.

We examined the viability of using mean propulsive velocity (MPV) to adjust the load in the countermovement jump (CMJ) at moderate altitude. Twenty-four volunteers were assigned to a 4-week power-oriented resistance training (RT) program in either normoxia (N, 690 m) or intermittent hypobaric hypoxia (IH, 2,320 m). The load was adjusted to maintain execution velocity of CMJ at 1m·s−1 of MPV. Relative peak power output (Prel), and percentage of velocity loss throughout the sets (VL) were determined for each session. The internal load was measured by the rating of perceived exertion (RPE). The absolute load lifted was higher in IH compared to N (75.6 ± 8.4 vs. 58.5 ± 12.3 kg P < 0.001). However, similar relative increases for both groups were found when comparing the final values (IH: 8.2%, P = 0.007; N: 9.8%, P = 0.03) with no changes in VL between groups (P = 0.36). Post-study Prel improved significantly only in IH (+7% W·kg−1, P = 0.002). Mean RPE was greater in IH vs. N (6.8 ± 1.5 vs. 5.6 ± 2, P < 0.001). The MPV seems to be a viable method for adjusting external load during RT at moderate altitude. However, given that RT at moderate altitude increases RPE, it is prudent to monitor internal load when using the MPV to best determine the actual physiological stress of the session.

Prevalence, clinical outcomes and rainfall association of acute respiratory infection by human metapneumovirus in children in Bogot\xe1, Colombia

BackgroundAcute respiratory infections (ARIs) are one of the main causes of morbidity and mortality in children. Viruses are the main etiological agents, and their behavior tends to be seasonal and vary by geographical location. Human metapneumovirus (HMPV) has recently been described as a cause of severe acute respiratory infection and its prevalence and clinical behavior in children at moderate altitudes is unknown.MethodsA cross-sectional study was carried out on patients seen at a university hospital in Bogotá, Colombia between October 2015 and December 2017 in a city at a moderate altitude above sea level. Children with acute respiratory infections who had had a multiplex RT-PCR assay were selected. The prevalence of HMPV infection, its clinical outcomes and its relationship to rainfall were evaluated.ResultsOut of a total of 14,760 discharged patients, multiplex RT-PCR was performed on 502 and a virus was detected in 420 children with acute respiratory infection (ARI). The study group had a median age of 21 months (IQR 7–60), with similar proportion of males and females (56.4 and 43.6% respectively) and 5.2% (CI 95 3.3–7.8%) prevalence of HMPV infection. The group with HMPV infection showed a greater frequency of viral coinfection (22.7% vs 14% P = 0.03) compared with ARI caused by other viruses. The rate of bacterial coinfection (P = 0.31), presence of comorbidities (p = 0.75), length of hospital stay (P = 0.42), need for mechanical ventilation (P = 0.75) and mortality (P = 0.22) were similar for HMPV and other viral infections. A moderate correlation was established between HMPV infection and rainfall peaks (Spearman’s Rho 0.44 p = 0.02).ConclusionsHuman metapneumovirus was the fifth most frequently isolated virus in children with ARI, had similar clinical behavior and severity to other viruses but a higher rate of viral coinfection. Its peaks seem to correlate to rainy seasons.

LYMPHOCYTE TRAFFICKING FOLLOWING ACUTE STRESS AND ALTITUDE HYPOXIA IN LOW AND HIGH HEMATOCRIT SHEEP

The object of the present study was to investigate small and large lymphocytestrafficking in sheep with low and high hematocrit values following shearing,exposure to moderate altitude and transport to low altitude. Twenty out of 101 Ilede France ewes (1-7 years old) were used in the present experiment. All ewes ofthe flock were artificially inseminated in May 2015 following estrussynchronization. The animals were allocated into two groups following threefoldmeasurements of hematocrit in all ewes as follows: I- low hematocrit group (n=10)and II - high hematocrit group (n=10). The ewes were transported to the PetrohanPass (1440 m above sea level) in June 2015 immediately after shearing, conductedat the experimental farm of the Institute of Animal Science, Kostinbrod (500 mabove sea level). Blood samples were collected before shearing, immediately aftershearing, 3 h after shearing, at 14 d following exposure to moderate altitude,immediately after transport to low altitude and following 7d of stay at low altitude.All leukocyte subpopulations were counted microscopically. In the current studywe presented the percentage of lymphocytes only, including small and large(reactive) lymphocytes. High and low hematocrit ewes had different percentage ofsmall lymphocytes when exposed to various acute and chronic stress stimuli. Therewere significant differences in the percentage of large (reactive) lymphocytesbetween low and high hematocrit ewes following blood collection and immediatelyafter shearing. The observed difference in small lymphocyte dynamics among thegroups in response to different stress stimuli was attributed to hematocrit relateddifferences in the time course and magnitude of lymphocyte distribution at earlyand late phases of stress. The results were interpreted to mean that the differencesin lymphocyte trafficking between the two groups of sheep in response to stresswere related to possible difference in the share of aerobic and glycolytic pathwaysfor energy supply.

M58 LINKING VARIABILITY IN GUT MICROBIOME AND LARGE-SCALE BRAIN NETWORK CONNECTIVITY

Exclosures are established with the objective of rehabilitating degraded lands and restoring of woody vegetation. Various studies have been conducted to evaluate the success of exclosure on restoring woody species diversity. However, works focusing on the effect of topographic factors on woody species diversity are scarce. Understanding the factors that determine woody species diversity is important for management purposes. Therefore, this paper analyzes the effect of altitude, slope, and aspect as topographic variables on woody species diversity in Dawsura exclosure in northern Ethiopia. Data on species identity, abundance, slope, elevation and aspect were recorded from 58 sampling plots. Different diversity indices were used to analyze the data and one-way ANOVA and linear regression was conducted. There were a total of 34 woody species represented 15 families, of which 62% and 38% were trees and shrubs respectively. Altitude (r2 = 0.63, p = 0.000 and r = 0.794, p < 0.01) and slope (r2 = 0.57, p = 0.002 and r = 0.68, p < 0.01) correlated significantly and positively with Shannon diversity, whereas aspect (r2 = 0.12, p = 0.378 and r = 0.27, p > 0.05) did not correlate significantly with Shannon diversity. Woody species diversity at moderate (1.44) and high (1.85) altitudes was significantly different from that of low (0.86) altitude areas (p = 0.0013). Furthermore, significantly higher woody species diversity was recorded at steep slope (1.88) and moderately steep slope (1.62) areas as compared to the gentle slope (0.95) areas. No significant variation was observed in woody species diversity among the aspect categories (p > 0.05). The study concludes that woody species diversity is largely regulated by slope and altitude than aspect in the exclosure. We suggest other environmental and anthropogenic variables should be taken into consideration in future studies on woody species diversity.

Revised threshold values for neonatal oxygen saturation at mild and moderate altitudes.

The aim of this study was to determine reference values for oxygen saturation (SpO2 ) in neonates at mild and moderate altitudes. Our study included 41097 consecutively born, asymptomatic neonates from 35 hospitals, located in Yunnan, China, with altitudes ranging from 267 to 2202m. Pre-and post-ductal SpO2 of each neonate was measured at 24hours of age and before hospital discharge. All study participants, according to the altitude of birth, were categorised into three groups: low (0-500m), mild (500-1500m) and moderate altitude (1500-2500m). Every 1000-m increase in altitude was associated with a 1.54 per cent decrease in mean SpO2 . The means of pre-ductal SpO2 at low, mild and moderate groups were 97.9%, 96.4% and 95.5%, respectively. We used the 2.5th percentile of SpO2 distribution as the cut-off for neonatal SpO2 screening and defined new cut-off values of ≤93% for mild altitudes, ≤92% for moderate altitudes and no adjustment for low altitudes. We recommend revised cut-off values for neonatal SpO2 at mild and moderate altitudes and provide new values for paediatricians to refer to when screening neonates for severe congenital heart or lung diseases.

Abstract P194: Endothelin as a Persistent Biomarker of Hypoxia

Rationale: Hypoxic symptoms at moderate altitude are not well characterized. Hypoxia can cause cognitive impairment, temporarily affecting the performance of aircrew, ground soldiers or other critical workers. Therefore, there is a need to determine if an individual has experienced asymptomatic hypoxemia after exposure to high altitude. Goal: To identify reliable blood biomarkers that are quickly modified by hypoxia which correlate with blood gases and cardiac-hemodynamic parameters. Plasma endothelin-1 [ET-1]p was initially investigated as a potential biomarker due to its upregulation by hypoxia. Methods: Mean arterial pressure (MAP), heart rate (HR) and electrocardiogram (ECG) were wirelessly recorded in conscious rats during exposure. Blood was obtained from rats exposed to normoxia (21% O 2 ) or hypoxia (12% O 2 ) after 0.5, 1, 6, or 24 hours. [ET-1] p level was assessed by ELISA. Results: MAP and HR increased after 6 hrs of hypoxia. PR interval of the ECG progressively increased in hypoxic rats correlating with the decrease in HR. Low frequency/high frequency (LF/HF) component of HR variability (HRV) decreased only after 30 min of hypoxia suggesting early parasympathetic effects. [ET-1] p increased after 1-24 hrs of hypoxia. [ET-1] p negatively correlated with Pa O2 , Pa CO2 , HCO 3 - , MAP and HR, but positively with LF (baroreceptor band) and HF (respiratory band). These results suggest hypoxia rapidly increases [ET-1] p , which may contribute to restoration of MAP. Conclusions: Our data suggest that ET-1 is a reliable hypoxia biomarker. Future studies will determine other potential biomarkers and for how long ET-1 remains elevated after returning to normoxia.