Influence Of High Altitude Research Articles

Influence of high altitude after a prior ascent on physical exhaustion during cardiopulmonary resuscitation: a randomised crossover alpine field experiment

BackgroundPerforming cardiopulmonary resuscitation (CPR) inevitably causes significant physical, as well as psychological stress for rescuers. Physical activity at high altitude, a hypobaric and hypoxic environment, similarly adds to the level of stress and causes multiple physiological changes. Continuous measurement of pulse rate serves as an objective measure of fatigue during CPR. We therefore aimed to investigate rescuers’ heart rates as a measure of physical strain during CPR in a high-altitude alpine environment to provide a better understanding of the physiological changes under these very special conditions.MethodsTwenty experienced mountaineers performed basic life support (BLS) on a manikin for 16 min, both at baseline altitude and at high altitude (3454 m) following a quick and exhausting ascent over 1200 m. Sequence of scenarios was randomised for analysis. Heart rate was continuously measured and compared between baseline and high altitude by absolute differences and robust confidence intervals.ResultsDuring CPR at baseline, the average heart rate increased from 87 bpm (SD 16 bpm) to 104 bpm [increase 17 bpm (95% CI 8.24–24.76)], compared to an increase from 119 bpm (SD 12 bpm) to 124 bpm [increase 5 bpm (95% CI − 1.59 to 12.19)] at high altitude [difference between two groups 32 bpm (95% CI 25–39)]. Differences between periods of chest compressions and ventilations were very similar at baseline [19 bpm (95%CI 16.98–20.27)] and at high altitude [20 bpm 95% CI 18.56–21.44)], despite starting from a much higher level at high altitude. The average heart rates of rescuers at high altitude at any point were higher than those at baseline at any other point.ConclusionPerforming BLS CPR causes exhaustion both at base level and at a high altitude. A further increase during CPR might imply a physiological reserve for adapting to additional physical exertion at high altitude. Phases of ventilation are much needed recovery-periods, but heart rates remain very high. Subjective measures of exhaustion, such as the BORG-scale, might lead to rescuers’ overestimation of their own performance.

Numerical Investigation of the Intercooler Performance of Aircraft Piston Engines Under the Influence of High Altitude and Cruise Mode

Abstract Multistage supercharging is an effective way to solve the problems of low volumetric efficiency and combustion deterioration of piston engines under high altitude conditions. As a critical component of the supercharger system, the high-altitude intercooler performance is challenged to meet the heavy heat load caused by the large boosting ratio. The purpose of this study was to add more knowledge on the high-altitude intercooler performance to the limited existing studies. The intercooler experimental tests were conducted in a high-altitude simulation system, allowing for simultaneous pressure and temperature reductions. A 3D computational fluid dynamics (CFD) model was developed and validated against experimental results to investigate the intercooler performance, including the heat exchange and pressure drop characteristics. The results indicated that the atmospheric conditions and cruising speed significantly affected the intercooler performance. For example, the weighting of the effects of the temperature difference and air density on heat exchange performance varied with altitude. The altitude of 11 km was the turning point of the heat transfer rate because it is the junction of the troposphere and stratosphere. Based on this finding, this study further investigated whether a higher cruise speed could compensate for heat transfer deterioration with increasing altitude, more consistent with actual flight conditions. The simulation results showed that the variation of cruise speed directly affected the effectiveness of the heat exchanger, resulting in a different trend with altitude. Furthermore, the heat exchange of the intercooler fluctuated less with altitude under variable speed conditions. Overall, these findings support more fundamental research on high-altitude intercoolers, which may benefit the design and optimization of high-altitude engines and turbocharged systems.

Influence of high altitude on the strength of aerated concrete.

Aerated concrete specimens were prepared at Fuzhou and Lhasa with the same processing conditions. The compressive strengths of the specimens in Lhasa were lower than that in Fuzhou. We used SEM-EDS, XRD, FT-IR and MIP to study their microstructure in order to find the reasons made for differences in strength. Furthermore, the effect of the preparation process on the material strength was analyzed. The results showed that a low ambient temperature affected the autoclave curing process of the aerated concrete. A longer time was needed to reach the desired constant temperature, resulting in an insufficient degree of hydration, a low level of tobermorite generation, poor crystallinity, high porosity, an uneven pore size distribution, more harmful pore content above 200 nm and unsatisfactory strength. Under low environmental pressure, increasing autoclave pressure can promote the better formation of tobermorite to improve the strength of aerated concrete.

Influence of high altitude on the expression of HIF-1 and on the prognosis of Ecuadorian patients with gastric adenocarcinoma.

Since the incidence of gastric adenocarcinoma (GA) is high in populations living at high altitudes, we evaluated the influence of altitude on the expression of HIF-1 and survival of Ecuadorian GA patients. Method: 155 GA cases were studied: 56 from coastal (GAC) and 99 from mountainous regions (GAM), and 74 non-GA controls (25 coast and 49 mountain). The expression of HIF-1/HER2 was analyzed by immunohistochemistry. Analyses were performed using Fisher's exact and Breslow-Day tests for homogeneity and Kaplan-Meier curves and restricted median survival time ΔRMST. Results: HIF-1 was overexpressed in normal/inflamed gastric mucosa, especially in mountainous non-GA patients (p = 0.001). There was no difference between GAC and GAM in terms of age/gender, HIF-1/HER2 expression, stage/tumor location. Median survival at 120 months was significantly higher among GAC, with a difference (ΔRMST) of 43.7 months (95% CI 29.5, 57.8) (p < 0.001) and those with positive HIF-1 expression: ΔRMST 26.6 months (95% CI 11.0, 42.1) (p < 0.001). Positive HIF-1 expression was associated with better GAM survival, with ΔRMST 33.6 months (95% CI 14.2, 52.9) (p < 0.001). Conclusion: Despite the limitations of this retrospective study, GA patients in the coastal region and those who expressed HIF-1 exhibited a better prognosis, but this factor was associated with better survival only in the mountain region.

Prolonged Sojourn at Very High Altitude Decreases Sea-Level Anaerobic Performance, Anaerobic Threshold, and Fat Mass.

Background: The influence of high altitude on an organism’s physiology depends on the length and the level of hypoxic exposure it experiences. This study aimed to determine the effect of a prolonged sojourn at very high altitudes (above 3,500m) on subsequent sea-level physical performance, body weight, body composition, and hematological parameters.Materials and Methods: Ten alpinists, nine males and one female, with a mean age of 27±4years, participated in the study. All had been on mountaineering expeditions to 7,000m peaks, where they spent 30±1days above 3,500m with their average sojourn at 4,900±60m. Their aerobic and anaerobic performance, body weight, body composition, and hematological parameters were examined at an altitude of 100m within 7days before the expeditions and 7days after they descended below 3,500m.Results: We found a significant (p<0.01) decrease in maximal anaerobic power (MAPWAnT) from 9.9±1.3 to 9.2±1.3W·kg−1, total anaerobic work from 248.1±23.8 to 228.1±20.1J·kg−1, anaerobic threshold from 39.3±8.0 to 27.8±5.6 mlO2·kg−1·min−1, body fat mass from 14.0±3.1 to 11.5±3.3%, and a significant increase (p<0.05) in maximal tidal volume from 3.2 [3.0–3.2] to 3.5 [3.3–3.9] L after their sojourn at very high attitude. We found no significant changes in maximal aerobic power, maximal oxygen uptake, body weight, fat-free mass, total body water, hemoglobin, and hematocrit.Conclusion: A month-long exposure to very high altitude led to impaired sea-level anaerobic performance and anaerobic threshold, increased maximal tidal volume, and depleted body fat mass, but had no effect on maximal aerobic power, maximal oxygen uptake, or hemoglobin and hematocrit levels.

Data study on influence of high altitude on dynamic performance of supercharged diesel engine

In this paper, the dynamic performance of turbocharged diesel engine is studied comprehensively and systematically by using a high altitude diesel engine simulation test-bed to simulate different altitudes. The influence of altitude change on the dynamic performance of turbocharged diesel engine is analyzed, which provides an important basis for further improving and enhancing the performance of turbocharged diesel engine at high altitude.

Does change in barometric pressure per given time at high altitude influence symptoms of acute mountain sickness on Mount Fuji? A pilot study

BackgroundAcute mountain sickness (AMS) is a common, transient condition characterized primarily by headaches, and it can also be associated with fatigue, dizziness, and nausea with vomiting. The symptoms of AMS are most pronounced after the first night spent at a new altitude. At sea level, changes in barometric pressure per given time have been associated with migraine headaches. We sought to investigate whether changes in barometric pressure, subjective sleep quality index, and other candidates contributed to the risk of developing AMS on Mount Fuji in Japan.MethodWe surveyed 353 trekkers who stayed overnight at a mountain lodge before summitting Mount Fuji. We collected information regarding sex, age, sleeping altitude at the hut, and perceived sleep quality index including sleep time. AMS was assessed with the Lake Louise Scoring system. Barometric pressure and ambient temperature were collected at the 5th station (2305 m) and at the summit (3776 m).ResultThe overall prevalence of AMS in our cohort was 41.4% (Lake Louise Score ≥ 3 with headache, n=146). Using logistic regression, three factors were combined to generate a robust model for determining the risk of AMS (with or without AMS). These included (1) Δ barometric pressure during ascent per hour, (2) sleepiness on rising, and (3) sleep refreshment assessed by perceived sleep quality index.ConclusionThese results suggest that climbers who stay overnight at the lodge should keep a better physical condition of sleep, and would pay attention to information of barometric pressure condition to decrease their risk of AMS at the summit of Mount Fuji. Our observatory data indicated that an overnight staying in half way up to the summit does not necessarily reduce the AMS risk in both sexes and irrespective of age, at least, until 3776 m elevation.

Assessing Hydrological Vulnerability to Future Droughts in a Mediterranean Watershed: Combined Indices-Based and Distributed Modeling Approaches

Understanding the spatiotemporal distribution of future droughts is essential for effective water resource management, especially in the Mediterranean region where water resources are expected to be scarcer in the future. In this study, we combined meteorological and hydrological drought indices with the Soil and Water Assessment Tool (SWAT) model to predict future dry years during two periods (2035–2050and 2085–2100) in a typical Mediterranean watershed in Northern Morocco, namely, Bouregreg watershed. The developed methodology was then used to evaluate drought impact on annual water yields and to identify the most vulnerable sub-basins within the study watershed. Two emission scenarios (RCP4.5 and RCP8.5) of a downscaled global circulation model were used to force the calibrated SWAT model. Results indicated that Bouregreg watershed will experience several dry years with higher frequency especially at the end of current century. Significant decreases of annual water yields were simulated during dry years, ranging from −45.6% to −76.7% under RCP4.5, and from −66.7% to −95.6% under RCP8.5, compared to baseline. Overall, hydrologic systems in sub-basins under the ocean or high-altitude influence appear to be more resilient to drought. The combination of drought indices and the semi-distributed model offer a comprehensive tool to understand potential future droughts in Bouregreg watershed.

Influence of high altitude on competition demands of the professional tennis on hard and clay surface

Tennis is played over different surfaces and under different conditions of humidity, altitude, air pressure, etc. Therefore, analyzing competition statistics is considered a key factor since it can help to shape the training in order to get a better performance of the tennis player. The aim of this study was to know the differences in match statistics of ATP 250 tournaments disputed over different court surfaces (clay and hard-court) and under different conditions of the location (sea level and altitude). 122 single male matches were analyzed (62 played in altitude and 60 at sea level). Variables related to match, serve and return were analyzed. Overall, the results showed significant differences in many variables between matches played at sea level and at altitude. The altitude situation seems to affect positively in the variables related to the service, getting the players greater number of aces and points won with first and second serve. On the contrary, the variables related to the rest seem to be affected to a greater extent in hard court than in clay. Altitude and surface conditions influence the competition statistics of professional tennis, in a way that conditions the performance of the professional player.

Different neurocognitive patterns of conflict control in Tibetans living above and below 4,000 m

BackgroundThe existence of a particular threshold of hypoxia severity, beyond which neuropsychological functioning is compromised, is unclear. We investigated the neurocognitive profile related to conflict control in healthy young Tibetans born and living at three different altitudes (2,700 m, 3,700 m, and 4,500 m) in Tibet to investigate the existence of this threshold.MethodsUsing event-related potentials (ERPs), the conflict control functions of individuals in the three altitude groups were investigated by means of a flanker task, using congruent and incongruent stimuli. The data were analyzed using mixed-model analyses of variance.ResultsAlthough effect of altitude was not significant at a behavioral level (p > 0.05), the ERPs showed cognitive conflict modulation. The N2 difference wave (for incongruent minus congruent conditions) was smaller in the 4,500-m group than in the groups living below 4,000 m (p < 0.05). The study’s findings suggest that the influence of high altitude in the conflict monitoring stage becomes significant above 4,000 m. Thus, the altitude threshold for impairment of cognition may be 4,000 m.

Influence of high altitude on C-reactive protein levels in adults with abdominal visceral adiposity

Objetivo: Evaluar la influencia de la altura en los niveles de proteina C reactiva (PCR) en adultos con adiposidad visceral abdominal. Materiales y metodos: Se realizo un estudio cuantitativo con diseno cuasi-experimental, que incluyo veinticuatro estudiantes de medicina de la Universidad Nacional de Trujillo, sexo masculino, seleccionados de manera no probabilistica por conveniencia y sujeto participante, que fueron evaluados a 0 y 4386 m s. n. m. y clasificados de acuerdo al grado de adiposidad visceral abdominal: normal (G1) y elevada (G2). Resultados: El nivel de PCR de G1 en relacion a G2 no tuvo diferencia significativa. Respecto a los niveles de PCR de G2 se empleo la prueba no parametrica de Wilcoxon y para G1 se uso la prueba T-student, evidenciandose una significancia en ambos casos. Conclusiones: Las variaciones de los niveles de PCR en altura con respecto al basal de ambos grupos fueron significativos.

Influence of high altitude on the burning behaviour of typical combustibles and the related responses of smoke detectors in compartments.

The effect of altitude on typical combustible burning and related smoke detector response signals was investigated by comparison experiments at altitudes of 40 m and 3650 m based on EN54 standard tests. Point-type light scattering photoelectric smoke detectors and ionization smoke detectors were used for four kinds of EN54 fire tests, including two kinds of smouldering fires with wood (test fire no. 2 in EN54 standard or TF2) and cotton (TF3), and two kinds of flaming fires with polyurethane (TF4) and n-heptane (TF5). First, the influence of altitude or ambient pressure on mass loss for smouldering combustion (TF2 or TF3) was insignificant, while a significant decrease in the mass burning rate was found for flaming tests (TF4 and TF5) as reported in our previous studies. Second, for photoelectric smoke detectors in flaming fire tests, the effect of altitude was similar to that of the burning rate, whereas for the ionization smoke detectors, the response signal at high altitudes was shown to be ‘enhanced’ by the detection principle of the ionization chamber, leading to an even larger value than at normal altitude for smouldering conditions. Third, to provide a reference for smoke detector design in high-altitude areas, the differences between signal speed in rising and peak values at two locations are discussed. Also, relationship between ion chamber signals and smoke optical densities are presented by utilization of an ionization smoke detector and smoke concentration meter. Moreover, a hierarchical diagram is illustrated to provide a better understanding of the effects of altitude on combustible burning behaviour and the mechanisms of detector response.

The influence of high altitude on the anticipated childhood growth Taif city - Saudi Arabia 2018 :a cross sectional study

Optimal child growth is a crucial goal that should be pursued to guarantee a healthy life for the individuals in a population with a good quality of life. For this purpose, any risk factors that may disturb or affect the normal growth pattern should be recognized. Living at a high altitude is suggested to be one of these factors. In this study, we aimed to explore if there is a relationship between living in high altitude cities like Taif' and children's growth. Our population was randomly selected from children whose ages range from 5 to 18 years old and who live in Taif city. A total of 277 children were included in this study. Information about their anthropometric measurements were collected and compared to the Saudi national growth standard. Results showed that both weight and height of boys were significantly higher than the Saudi national growth standard. And for girls, the weight was significantly higher while the height did not differ significantly from the Saudi national growth standard. These findings do not support the hypothesis that living in high altitude cities like Taif can affect child's growth negatively in terms of height and weight.

Experimental study of high altitude effect on heat release rates of pool fires using calorimeters

With the aid of same configured calorimeters as dimensions of 40% of that in ISO 9705 in Hefei (24 m, 100.8 kPa) and Lhasa (3650 m, 64 kPa), the influence of high altitude on heat release rate and combustion efficiency were investigated. Two groups of liquid pool fires of moderate sizes (D = 0.15, 0.25 m) with fuel level maintaining system were tested at two sites, respectively. Typical fuels with different sooting levels, i.e., N-heptane and Jet-A, were selected. The ambient air pressure effects were introduced by modifying the standard calculation method of heat release rate in ISO 9705. Experimental results indicated that the dimensionless burning intensity in the quasi-steady stage for both fuels could be accorded to pressure modeling with acceptable accuracy. And it could be correlated with radiation modeling well for Jet-A, while that of n-heptane failed and this may be explained by the flame convection feedback which could not be neglected for moderate sooty fuel of moderate sizes. The combustion efficiency at high altitude is slightly higher than that at atmospheric pressure, and it will gradually increase with the decreasing pool dimension regardless of the ambient pressure.

Impact of extreme exercise at high altitude on oxidative stress in humans.

Exercise and oxidative stress research continues to grow as a physiological subdiscipline. The influence of high altitude on exercise and oxidative stress is among the recent topics of intense study in this area. Early findings indicate that exercise at high altitude has an independent influence on free radical generation and the resultant oxidative stress. This review provides a detailed summary of oxidative stress biochemistry as gleaned mainly from studies of humans exercising at high altitude. Understanding of the human response to exercise at altitude is largely derived from field-based research at altitudes above 3000m in addition to laboratory studies which employ normobaric hypoxia. The implications of oxidative stress incurred during high altitude exercise appear to be a transient increase in oxidative damage followed by redox-sensitive adaptations in multiple tissues. These outcomes are consistent for lowland natives, high altitude acclimated sojourners and highland natives, although the latter group exhibits a more robust adaptive response. To date there is no evidence that altitude-induced oxidative stress is deleterious to normal training or recovery scenarios. Limited evidence suggests that deleterious outcomes related to oxidative stress are limited to instances where individuals are exposed to extreme elevations for extended durations. However, confirmation of this tentative conclusion requires further investigation. More applicably, altitude-induced hypoxia may have an independent influence on redox-sensitive adaptive responses to exercise and exercise recovery. If correct, these findings may hold important implications for athletes, mountaineers, and soldiers working at high altitude. These points are raised within the confines of published research on the topic of oxidative stress during exercise at altitude.

MORBIDITY AND MORTALITY FROM CARDIOVASCULAR DISEASES ACCORDING TO THE SEA-LEVEL RELATED ALTITUDE OF A REGION

It is known that the common risk factors (RF) of cardiovascular diseases (CVD) do exist and do influence all people the same. Among them are arterial hypertension, smoking, total cholesterol, obesity etc. However there are specifics of RF realization connected to climatogeographic specifics, i.e. high mountain altitudes. The review is concerned on the influence of the high altitude influence on RF of CVD. Some papers show that in high altitudes inhabitants the RF of CVD were prognostically malevolent, but the level of total and coronary mortality was lower in mountain inhabitants that can be explained by more intensive physical exertion with the background moderate hypoxia. There is an opinion that lower mortality in higher altitudes can be explained as connected with physiological adaptation to altitude and/or specifics of the climate (i.e. with UV-rays exposure, those become more intensive by 10% every 300 m). Lipidogramm are supposedly linked to moderate hypoxia and lowering of temperature, also the diet specifics might influence. However there is no stabile relation of mortality and the parameters studied. So the results collected in different trials are still controversial. But if long-term living in higher altitudes, secondarily, by the activation of adaptation capacities of the body, diet specifics and physical exertion, leads to the decrease of morbidity and mortality from CVD, short-term visiting of the mountains might be harmful for some persons and this requires individualized approach to recommendations of prevention.

Influence of high altitude on cerebral blood flow and fuel utilization during exercise and recovery.

We examined the hypotheses that: (1) during incremental exercise and recovery following 4-6 days at high altitude (HA) global cerebral blood flow (gCBF) increases to preserve cerebral oxygen delivery (CDO2) in excess of that required by an increasing cerebral metabolic rate of oxygen ( CM RO2); (2) the trans-cerebral exchange of oxygen vs. carbohydrates (OCI; carbohydrates = glucose + ½lactate) would be similar during exercise and recovery at HA and sea level (SL). Global CBF, intra-cranial arterial blood velocities, extra-cranial blood flows, and arterial-jugular venous substrate differences were measured during progressive steady-state exercise (20, 40, 60, 80, 100% maximum workload (Wmax)) and through 30 min of recovery. Measurements (n = 8) were made at SL and following partial acclimatization to 5050 m. At HA, absolute Wmax was reduced by ∼50%. During submaximal exercise workloads (20-60% Wmax), despite an elevated absolute gCBF (∼20%, P < 0.05) the relative increases in gCBF were not different at HA and SL. In contrast, gCBF was elevated at HA compared with SL during 80 and 100% Wmax and recovery. Notwithstanding a maintained CDO2 and elevated absolute CM RO2 at HA compared with SL, the relative increase in CM RO2 was similar during 20-80% Wmax but half that of the SL response (i.e. 17 vs. 27%; P < 0.05 vs. SL) at 100% Wmax. The OCI was reduced at HA compared with SL during 20, 40, and 60% Wmax but comparable at 80 and 100% Wmax. At HA, OCI returned almost immediately to baseline values during recovery, whereas at SL it remained below baseline. In conclusion, the elevations in gCBF during exercise and recovery at HA serve to maintain CDO2. Despite adequate CDO2 at HA the brain appears to increase non-oxidative metabolism during exercise and recovery.

Influence of high altitude on cerebrovascular and ventilatory responsiveness to CO2

An altered acid-base balance following ascent to high altitude has been well established. Such changes in pH buffering could potentially account for the observed increase in ventilatory CO(2) sensitivity at high altitude. Likewise, if [H(+)] is the main determinant of cerebrovascular tone, then an alteration in pH buffering may also enhance the cerebral blood flow (CBF) responsiveness to CO(2) (termed cerebrovascular CO(2) reactivity). However, the effect altered acid-base balance associated with high altitude ascent on cerebrovascular and ventilatory responsiveness to CO(2) remains unclear. We measured ventilation , middle cerebral artery velocity (MCAv; index of CBF) and arterial blood gases at sea level and following ascent to 5050 m in 17 healthy participants during modified hyperoxic rebreathing. At 5050 m, resting , MCAv and pH were higher (P < 0.01), while bicarbonate concentration and partial pressures of arterial O(2) and CO(2) were lower (P < 0.01) compared to sea level. Ascent to 5050 m also increased the hypercapnic MCAv CO(2) reactivity (2.9 +/- 1.1 vs. 4.8 +/- 1.4% mmHg(1); P < 0.01) and CO(2) sensitivity (3.6 +/- 2.3 vs. 5.1 +/- 1.7 l min(1) mmHg(1); P < 0.01). Likewise, the hypocapnic MCAv CO(2) reactivity was increased at 5050 m (4.2 +/- 1.0 vs. 2.0 +/- 0.6% mmHg(1); P < 0.01). The hypercapnic MCAv CO(2) reactivity correlated with resting pH at high altitude (R(2) = 0.4; P < 0.01) while the central chemoreflex threshold correlated with bicarbonate concentration (R(2) = 0.7; P < 0.01). These findings indicate that (1) ascent to high altitude increases the ventilatory CO(2) sensitivity and elevates the cerebrovascular responsiveness to hypercapnia and hypocapnia, and (2) alterations in cerebrovascular CO(2) reactivity and central chemoreflex may be partly attributed to an acid-base balance associated with high altitude ascent. Collectively, our findings provide new insights into the influence of high altitude on cerebrovascular function and highlight the potential role of alterations in acid-base balance in the regulation in CBF and ventilatory control.

Protein composition, plasmin activity and cheesemaking properties of cows' milk produced at two altitudes from hay of lowland and high-alpine origins

The influence of high altitude, alpine origin of the forage and roughage-only diets on milk protein content and composition, plasmin activity and cheesemaking properties was investigated. There were four treatment groups, each consisting of six dairy cows in early to mid-lactation. Two groups were fed only with hay ad libitum either at 2000 m or at 400 m a.s.l. One group, kept in the lowlands, was pair-fed to the alpine-site group and another group received a mixed diet of silages, hay and concentrates. Two hay types, harvested either at the alpine site or in the lowlands, were offered to all cows fed with hay alone, following a change-over design in three periods each of 3 weeks. In the respective third week, milk was sampled at every milking. Hay of alpine origin significantly reduced milk protein, in particular whey proteins, which is why the casein number increased. kappa-Casein proportion in total casein was reduced and its glycosylation was increased by the alpine hay. The apparent plasminogen-derived activity was reduced when alpine hay was given, but apparent plasmin activity and rennet coagulation properties of the milk were not affected by hay type. Independent of hay type, the high altitude group showed a significantly reduced milk protein content, lower glycosylation of kappa-casein and impaired rennet coagulation properties. For several of the traits, the trend was the same in the pair-fed group. There was no effect of altitude on apparent plasmin activity. Hay-alone v. the mixed diet resulted initially in marked declines in milk protein content but did not impair cheesemaking properties. Thus the extensive diet without concentrates, typical of high-alpine conditions, contributed less to the overall effect of extensive alpine v. intensive lowland feeding systems than hay quality and altitude did. In conclusion, certain positive influences of the alpine sojourn of cows on cheese processing quality are overruled by the major adverse impact of lower milk protein content.

Influence of high altitudes on myocardial perfusion

Influence of high altitudes on myocardial perfusion