Modification of the CO-rebreathing method to determine haemoglobin mass and blood volume in patients suffering from chronic mountain sickness.

NEW FINDINGS: What is the central question of this study? Is it necessary to modify the CO-rebreathing method to acquire reliable measurements of haemoglobin mass in patients with chronic mountain sickness? What is the main finding and its importance? The CO-rebreathing method must be modified because of the prolonged CO-mixing time in patients with chronic mountain sickness. After adaptation of the blood sampling method, reliable and valid results were attained. With this modification, it is possible to quantify the extent of polycythaemia and to distinguish between a haemoconcentration and an exclusive enhancement of erythrocyte volume. ABSTRACT: Patients suffering from chronic mountain sickness (CMS) exhibit extremely high haemoglobin concentrations. Their haemoglobin mass (Hbmass), however, has rarely been investigated. The CO-rebreathing protocol for Hbmass determination in those patients might need to be modified because of restricted peripheral perfusion. The aim of this study was to evaluate the CO uptake and carboxyhaemoglobin-mixing time in the blood of CMS patients and to adapt the CO-rebreathing method for this group. Twenty-five male CMS patients living at elevations between 3600 and 4100 m above sea level were compared with ethnically matched healthy control subjects from identical elevations (n = 11) and near sea level (n = 9) and with a Caucasian group from sea level (n = 6). CO rebreathing was performed for 2 min, and blood samples were taken for the subsequent 30 min. After the method was modified, its reliability was evaluated in test-retest experiments (n = 28), and validity was investigated by measuring the Hbmass before and after the phlebotomy of 500 ml (n = 4). CO uptake was not affected by CMS. The carboxyhaemoglobin mixing was completed after 8 min in the Caucasian group but after 14 min in the groups living at altitude. When blood was sampled 14-20 min after inhalation, the typical error of the method was 1.6% (confidence limits 1.2-2.5%). After phlebotomy, Hbmass decreased from 1779 ± 123 to 1650 ± 129 g, and no difference was found between the measured and calculated Hbmass (1666 ± 122 g). When the time of blood sampling was adapted to accommodate a prolonged carboxyhaemoglobin-mixing time, the CO-rebreathing method became a reliable and valid tool to determine Hbmass in CMS patients.

Divergent physiological responses in laboratory rats and mice raised at high altitude.

Ecological studies show that mice can be found at high altitude (HA - up to 4000 m) while rats are absent at these altitudes, and there are no data to explain this discrepancy. We used adult laboratory rats and mice that have been raised for more than 30 generations in La Paz, Bolivia (3600 m), and compared their hematocrit levels, right ventricular hypertrophy (index of pulmonary hypertension) and alveolar surface area in the lungs. We also used whole-body plethysmography, indirect calorimetry and pulse oxymetry to measure ventilation, metabolic rate (O2 consumption and CO2 production), heart rate and pulse oxymetry oxygen saturation (pO2 ,sat) under ambient conditions, and in response to exposure to sea level PO2 (32% O2=160 mmHg for 10 min) and hypoxia (18% and 15% O2=90 and 75 mmHg for 10 min each). The variables used for comparisons between species were corrected for body mass using standard allometric equations, and are termed mass-corrected variables. Under baseline, compared with rats, adult mice had similar levels of pO2 ,sat, but lower hematocrit and hemoglobin levels, reduced right ventricular hypertrophy and higher mass-corrected alveolar surface area, tidal volume and metabolic rate. In response to sea level PO2 and hypoxia, mice and rats had similar changes of ventilation, but metabolic rate decreased much more in hypoxia in mice, while pO2 ,sat remained higher in mice. We conclude that laboratory mice and rats that have been raised at HA for >30 generations have different physiological responses to altitude. These differences might explain the different altitude distribution observed in wild rats and mice.

Graduated effects of high-altitude hypoxia and highland ancestry on birth size.

BACKGROUND: We present a cohort of ca. 25,000 birth records from Bolivia of men and women who are currently adults. We used this cohort to test the hypothesis that high altitude reduces birth weight and that highland ancestry confers graduated protection against this effect. METHODS: Birth records were obtained from obstetric clinics and hospitals in La Paz (3,600 m) and Santa Cruz (420 m). Only singleton, healthy term (>37 wk) pregnancies of nonsmoking mothers were included. Andean, Mestizo, or European ancestry was determined by validated analysis of parental surnames. RESULTS: High altitude reduced body weight (3,396 ± 3 vs. 3,090 ± 6 g) and length (50.8 ± 0 vs. 48.7 ± 0 cm) at birth (P < 0.001). Highland ancestry partially protected against the effects of high altitude on birth weight (Andean = 3,148 ± 15 g; Mestizo = 3,081 ± 6 g; and European = 2,957 ± 32 g; trend P < 0.001) but not on birth length. The effects of high-altitude pregnancy on birth size were similar for male and female babies. CONCLUSION: High altitude reduces birth weight and highland native ancestry confers graduated protection. Given previous studies linking reduced birth weight with increased risk of cardiovascular disease, further study is warranted to test whether adults from high-altitude pregnancy are at increased risk of developing cardiovascular disease.

Predicting sickness during a 2-week soccer camp at 3600 m (ISA3600).

OBJECTIVES: To examine the time course of changes in wellness and health status markers before and after episodes of sickness in young soccer players during a high-altitude training camp (La Paz, 3600 m). METHODS: Wellness and fatigue were assessed daily on awakening using specifically-designed questionnaires and resting measures of heart rate and heart rate variability. The rating of perceived exertion and heart rate responses to a submaximal run (9 km/h) were also collected during each training session. Players who missed the morning screening for at least two consecutive days were considered as sick. RESULTS: Four players met the inclusion criteria. With the exception of submaximal exercise heart rate, which showed an almost certain and large increase before the day of sickness (4%; 90% confidence interval 3 to 6), there was no clear change in any of the other psychometric or physiological variables. There was a very likely moderate increase (79%, 22 to 64) in self-reported training load the day before the heart rate increase in sick players (4 of the 4 players, 100%). In contrast, training load was likely and slightly decreased (-24%, -78 to -11) in players who also showed an increased heart rate but remained healthy. CONCLUSIONS: A >4% increased heart rate during submaximal exercise in response to a moderate increase in perceived training load the previous day may be an indicator of sickness the next day. All other variables, that is, resting heart rate, heart rate variability and psychometric questionnaires may be less powerful at predicting sickness.

Wellness, fatigue and physical performance acclimatisation to a 2-week soccer camp at 3600 m (ISA3600).

OBJECTIVES: To examine the time course of wellness, fatigue and performance during an altitude training camp (La Paz, 3600 m) in two groups of either sea-level (Australian) or altitude (Bolivian) native young soccer players. METHODS: Wellness and fatigue were assessed using questionnaires and resting heart rate (HR) and HR variability. Physical performance was assessed using HR responses to a submaximal run, a Yo-Yo Intermittent recovery test level 1 (Yo-YoIR1) and a 20 m sprint. Most measures were performed daily, with the exception of Yo-YoIR1 and 20 m sprints, which were performed near sea level and on days 3 and 10 at altitude. RESULTS: Compared with near sea level, Australians had moderate-to-large impairments in wellness and Yo-YoIR1 relative to the Bolivians on arrival at altitude. The acclimatisation of most measures to altitude was substantially slower in Australians than Bolivians, with only Bolivians reaching near sea-level baseline high-intensity running by the end of the camp. Both teams had moderately impaired 20 m sprinting at the end of the camp. Exercise HR had large associations (r>0.5-0.7) with changes in Yo-YoIR1 in both groups. CONCLUSIONS: Despite partial physiological and perceptual acclimatisation, 2 weeks is insufficient for restoration of physical performance in young sea-level native soccer players. Because of the possible decrement in 20 m sprint time, a greater emphasis on speed training may be required during and after altitude training. The specific time course of restoration for each variable suggests that they measure different aspects of acclimatisation to 3600 m; they should therefore be used in combination to assess adaptation to altitude.

Soccer activity profile of altitude versus sea-level natives during acclimatisation to 3600 m (ISA3600).

OBJECTIVES: We investigated the effect of high altitude on the match activity profile of elite youth high altitude and sea level residents. METHODS: Twenty Sea Level (Australian) and 19 Altitude-resident (Bolivian) soccer players played five games, two near sea level (430 m) and three in La Paz (3600 m). Match activity profile was quantified via global positioning system with the peak 5 min period for distance ((D5(peak)) and high velocity running (>4.17 m/s, HIVR5(peak)); as well as the 5 min period immediately subsequent to the peak for both distance (D5(sub)) and high-velocity running (HIVR5(sub)) identified using a rolling 5 min epoch. The games at 3600 m were compared with the average of the two near sea-level games. RESULTS: The total distance per minute was reduced by a small magnitude in the first match at altitude in both teams, without any change in low-velocity running. There were variable changes in HiVR, D5(peak) and HiVR5(peak) from match to match for each team. There were within-team reductions in D5(peak) in each game at altitude compared with those at near sea level, and this reduction was greater by a small magnitude in Australians than Bolivians in game 4. The effect of altitude on HiVR5(peak) was moderately lower in Australians compared with Bolivians in game 3. There was no clear difference in the effect of altitude on maximal accelerations between teams. CONCLUSIONS: High altitude reduces the distance covered by elite youth soccer players during matches. Neither 13 days of acclimatisation nor lifelong residence at high altitude protects against detrimental effects of altitude on match activity profile.

The sleep of elite athletes at sea level and high altitude: a comparison of sea-level natives and high-altitude natives (ISA3600).

BACKGROUND: Altitude exposure causes acute sleep disruption in non-athletes, but little is known about its effects in elite athletes. The aim of this study was to examine the effects of altitude on two groups of elite athletes, that is, sea-level natives and high-altitude natives. METHODS: Sea-level natives were members of the Australian under-17 soccer team (n=14). High-altitude natives were members of a Bolivian under-20 club team (n=12). Teams participated in an 18-day (19 nights) training camp in Bolivia, with 6 nights at near sea level in Santa Cruz (430 m) and 13 nights at high altitude in La Paz (3600 m). Sleep was assessed on every day/night using activity monitors. RESULTS: The Australians' sleep was shorter, and of poorer quality, on the first night at altitude compared with sea level. Sleep quality returned to normal by the end of the first week at altitude, but sleep quantity had still not stabilised at its normal level after 2 weeks. The quantity and quality of sleep obtained by the Bolivians was similar, or greater, on all nights at altitude compared with sea level. The Australians tended to obtain more sleep than the Bolivians at sea level and altitude, but the quality of the Bolivians' sleep tended to be better than that of the Australians at altitude. CONCLUSIONS: Exposure to high altitude causes acute and chronic disruption to the sleep of elite athletes who are sea-level natives, but it does not affect the sleep of elite athletes who are high-altitude natives.

Methods of the international study on soccer at altitude 3600 m (ISA3600).

BACKGROUND: We describe here the 3-year process underpinning a multinational collaboration to investigate soccer played at high altitude--La Paz, Bolivia (3600 m). There were two main aims: first, to quantify the extent to which running performance would be altered at 3600 m compared with near sea level; and second, to characterise the time course of acclimatisation of running performance and underlying physiology to training and playing at 3600 m. In addition, this project was able to measure the physiological changes and the effect on running performance of altitude-adapted soccer players from 3600 m playing at low altitude. METHODS: A U20 Bolivian team ('The Strongest' from La Paz, n=19) played a series of five games against a U17 team from sea level in Australia (The Joeys, n=20). 2 games were played near sea level (Santa Cruz 430 m) over 5 days and then three games were played in La Paz over the next 12 days. Measures were (1) game and training running performance--including global positioning system (GPS) data on distance travelled and velocity of movement; (2) blood--including haemoglobin mass, blood volume, blood gases and acid-base status; (3) acclimatisation--including resting heart rate variability, perceived altitude sickness, as well as heart rate and perceived exertion responses to a submaximal running test; and (4) sleep patterns. CONCLUSIONS: Pivotal to the success of the project were the strong professional networks of the collaborators, with most exceeding 10 years, the links of several of the researchers to soccer federations, as well as the interest and support of the two head coaches.

The impact of altitude on the sleep of young elite soccer players (ISA3600).

BACKGROUND: Altitude training is used by elite athletes to improve sports performance, but it may also disrupt sleep. The aim of this study was to examine the effects of 2 weeks at high altitude on the sleep of young elite athletes. METHODS: Participants (n=10) were members of the Australian under-17 soccer team on an 18-day (19-night) training camp in Bolivia, with six nights at near sea level in Santa Cruz (430 m) and 13 nights at high altitude in La Paz (3600 m). Sleep was monitored using polysomnography during a baseline night at 430 m and three nights at 3600 m (immediately after ascent, 1 week after ascent and 2 weeks after ascent). Data were analysed using effect size statistics. RESULTS: All results are reported as comparisons with baseline. Rapid eye movement (REM) sleep was likely lower immediately upon ascent to altitude, possibly lower after 1 week and similar after 2 weeks. On all three nights at altitude, hypopneas and desaturations were almost certainly higher; oxygen saturation was almost certainly lower; and central apnoeas, respiratory arousals and periodic breathing were very likely higher. The effects on REM sleep were common to all but one participant, but the effects on breathing were specific to only half the participants. CONCLUSIONS: The immediate effects of terrestrial altitude of 3600 m are to reduce the amount of REM sleep obtained by young elite athletes, and to cause 50% of them to have impaired breathing during sleep. REM sleep returns to normal after 2 weeks at altitude, but impaired breathing does not improve.

Possible strategies to reduce altitude-related excessive polycythemia.

We sought to determine the effects of three treatments on hemoglobin (Hb) levels in patients with chronic mountain sickness (CMS): 1) descent to lower altitude, 2) nocturnal O2 supply, 3) administration of acetazolamide. Nineteen patients with CMS living at an altitude of 3,940 ± 130 m participated in the study, which consisted of a 3-wk intervention phase and a 4-wk postintervention phase. Six patients spent 3 wk at an altitude of 1,050 m (low altitude group, LAG), six received supplemental oxygen for 12 h overnight (oxygen group, OXG), and seven received 250 mg of acetazolamide daily (acetazolamide group, ACZG). Hemoglobin mass (Hbmass) was determined using an adapted carbon monoxide (CO) rebreathing method before, weekly during, and 4 wk postintervention. Hbmass decreased by 245 ± 116 g (P < 0.01) in the LAG and by 100 ± 38 g in OXG, and 99 ± 64 g in ACZG (P < 0.05, each), respectively. In LAG, hemoglobin concentration ([Hb]) decreased by 2.1 ± 0.8 g/dL and hematocrit by 7.4 ± 2.9% (both P < 0.01), whereas OXG and ACZG only trended toward lower values. Erythropoietin concentration ([EPO]) decreased between 81 ± 12% and 73 ± 21% in LAG at low altitude (P < 0.01) and increased by 161 ± 118% 5 days after return (P < 0.01). In OXG and ACZG, the [EPO] decrease was ∼75% and ∼50%, respectively, during the intervention (P < 0.01). Descent to low altitude (from 3,940 m to 1,050 m) is a fast-acting measure for the treatment of excessive erythrocytosis in patients with CMS, reducing Hbmass by 16% within 3 wk. Nighttime oxygen supplementation and daily acetazolamide administration are also effective, but reduce Hbmass by only 6%.NEW & NOTEWORTHY To our knowledge, this is the first study examining the effect of three different treatments [descending to lower altitude (from 3,900 m to 1,050 m), nocturnal oxygen supply, and administration of acetazolamide] on changes in hemoglobin mass in patients experiencing chronic mountain sickness (CMS). We report that descent to low altitude is a fast-acting measure for the treatment of excessive erythrocytosis in patients with CMS, reducing Hbmass by 16% within 3 wk. Nighttime oxygen supplementation and daily acetazolamide administration are also effective, but reduce Hbmass by only 6%. In all three treatments, the underlying mechanism is a reduction in plasma erythropoietin concentration due to higher oxygen availability.

Hemoglobin Mass and Blood Volume in Patients With Altitude-Related Polycythemia.

Patients with chronic mountain sickness (CMS) have a high hemoglobin concentration [Hb] due to increased hemoglobin mass (Hbmass) and possibly reduced plasma volume (PV). The values of Hbmass, PV and blood volume (BV) have been described differently, and the relationships between [Hb] and Hbmass or PV are poorly understood. This study obtained representative Hbmass, PV and BV data from healthy, high-altitude residents and CMS patients and quantified the dependency of [Hb] on Hbmass and PV. METHODS: Eighty-seven subjects born at high altitude (∼3,900 m) were enrolled. Thirty-four had CMS (CMS), 11 had polycythemia without CMS (intermediate, IM), 20 were healthy highlanders (HH), and 22 living near sea level (SL, 420 m) served as the sea level (SL) control group. Hbmass, PV and BV were determined using a CO-rebreathing method modified for assessing polycythemia patients. Furthermore, [Hb], hematocrit (Hct), plasma erythropoietin concentration [EPO] and blood gas and acid-base status were determined. RESULTS: In the HH group, Hbmass was 27% higher (940 ± 105 g) than in the SL group (740 ± 112 g) and 72% (1,617 ± 265 g) lower than in the CMS group. The PV in the HH group was similar to that in the SL group (-6%) and 15% higher than that in the CMS group (p < 0.001). In the HH group, the BV (5,936 ± 673 ml) did not differ from that in the SL group and was 28% lower than in the CMS group (7,606 ± 1075 ml, p < 0.001). Log [EPO] was slightly increased in the CMS group relative to the HH group (p < 0.01). All values in the IM group were between those in the HH and CMS groups. Hbmass and BV were positively correlated, and PV was negatively correlated with peripheral O2 saturation. Increased Hbmass and decreased PV contributed approximately 65 and 35%, respectively, to the difference in [Hb] between the HH (17.1 ± 0.8 g/dl) and CMS (22.1 ± 1.0 g/dl) groups. CONCLUSIONS: In CMS patients, the decrease in PV only partially compensated for the substantial increase in Hbmass, but it did not prevent an increase in BV; the decrease in PV contributed to an excessively high [Hb].

Seasonal and circadian variation in salivary testosterone in rural Bolivian men.

Testosterone (T) plays a key role in the increase and maintenance of muscle mass and bone density in adult men. Life history theory predicts that environmental stress may prompt a reallocation of such investments to those functions critical to survival. We tested this hypothesis in two studies of rural Bolivian adult men by comparing free T levels and circadian rhythms during late winter, which is especially severe, to those in less arduous seasons. For each pair of salivary T(AM)/T(PM) samples (collected in a approximately 12-h period), circadian rhythm was considered classic (C(CLASSIC)) if T(AM) > 110%T(PM), reverse (C(REVERSE)) if T(PM) > 110%T(AM), and flat (C(FLAT)) otherwise. We tested the hypotheses that mean T(AM) > mean T(PM) and that mean T(LW) < mean T(OTHER) (LW = late winter, OTHER = other seasons). In Study A, of 115 T(PM)-T(AM) pairs, 51% = C(CLASSIC), 39% = C(REVERSE), 10% = C(FLAT); in Study B, of 184 T(AM)-T(PM) pairs, 55% = C(CLASSIC), 33% = C(REVERSE), 12% = C(FLAT). Based on fitting linear mixed models, in both studies T(OTHER-AM) > T(OTHER-PM) (A: P = 0.035, B: P = 0.0005) and T(OTHER-AM) > T(LW-AM) (A: P = 0.054, B: P = 0.007); T(PM) did not vary seasonally, and T diurnality was not significant during late winter. T diurnality varied substantially between days within an individual, between individuals and between seasons, but neither T levels nor diurnality varied with age. These patterns may reflect the seasonally varying but unscheduled, life-long, strenuous physical labor that typifies many non-industrialized economies. These results also suggest that single morning samples may substantially underestimate peak circulating T for an individual and, most importantly, that exogenous signals may moderate diurnality and the trajectory of age-related change in the male gonadal axis.

Developmental, genetic, and environmental components of lung volumes at high altitude.

Vital capacity and residual lung volume (in terms of 1/min or ml/m2 of body surface area) of 357 subjects (205 males, 152 females) was evaluated in La Paz, Bolivia, situated at 3,750 m. The sample included: (1) 37 high altitude rural natives (all male), (2) 125 high altitude urban natives (69 male, 58 female), (3) 85 Bolivians of foreign ancestry acclimatized to high altitude since birth (40 male, 45 female), (4) 63 Bolivians of foreign ancestry acclimatized to high altitude during growth (30 male, 33 female), and (5) 47 non-Bolivians of either European or North American ancestry acclimatized to high altitude during adulthood (24 male, 23 female). Results indicate that (1) all samples studied, irrespective of origin or acclimatization status, have larger lung volumes than those predicted from sea level norms; (2) the high altitude rural natives have significantly greater lung volumes (vital capacity and residual lung volume) than the high altitude urban natives and all the non-native high altitude samples; (3) males acclimatized to high altitude since birth or during growth attain similar lung volumes as high altitude urban natives and higher residual lung volumes than subjects acclimatized to high altitude during adulthood but lower than the high altitude rural natives; (4) females acclimatized to high altitude since birth or during growth attain similar lung volumes as subjects acclimatized to high altitude during adulthood; (5) age at arrival to high altitude is inversely related to residual lung volume but not vital capacity; (6) among subjects acclimatized to high altitude during growth, approximately 20-25% of the variability in residual lung volume can be explained by developmental factors; (7) among high altitude rural and urban natives, it appears that approximately 20-25% of the variability in residual lung volume at high altitude can be explained by genetic traits associated with skin reflectance and genetic traits shared by siblings; and (8) vital capacity, but not the residual lung volume, is inversely related to occupational activity level. Together these data suggest that the attainment of vital capacity at high altitude is influenced more by environmental factors, such as occupational activity level, and body composition than developmental acclimatization. On the other hand, the attainment of an enlarged residual volume is related to both developmental acclimatization and genetic factors. Am. J. Hum. Biol. 9:191-203, 1997. © 1997 Wiley-Liss, Inc.

Effect of developmental and ancestral high altitude exposure on chest morphology and pulmonary function in Andean and European/North American natives.

Chest depth, chest width, forced vital capacity (FVC), and forced expiratory volume (FEV1) were measured in 170 adult males differing by ancestral (genetic) and developmental exposure to high altitude (HA). A complete migrant study design was used to study HA natives (Aymara/Quechua ancestry, n = 88) and low altitude (LA) natives (European/North American ancestry, n = 82) at both altitude (La Paz, Bolivia, 3,600 m) and near sea level (Santa Cruz, Bolivia, 420 m). HAN and LAN migrant groups were classified as: N(th) generation migrants, born and raised in a non-native environment; child migrants who migrated during the period of growth and maturation (0-18 yrs); and adult migrants who migrated after 18 years of age. Chest depth, FVC, and FEV1 measures were larger with increasing developmental exposure in both HAN migrants at LA and LAN migrants at HA. Developmental responses were similar between HAN and LAN groups. FVC and FEV1 measures were larger in HANs vs LANs born and raised at HA to suggest a genetic effect, but were similar in HANs and LANs born and raised at LA. The similarity of HAN and LAN groups at LA suggests that the genetic potential for larger lung volumes at HA depends upon developmental exposure to HA. Additional data for females (HANs at HA, n = 20, and LAN adult migrants to HA, n = 17) show similar differences as those shown between male HAN and LAN groups. Am. J. Hum. Biol. 11:383-395, 1999. Copyright 1999 Wiley-Liss, Inc.

Fútbol en la altura en Bolivia / football at altitude in Bolivia

El presente trabajo se realizó en razón del tercer veto emitido por la FIFA, de jugar partidos eliminatorios para Copas Mundiales de Fútbol en alturas por encima de los 2500 m. Los objetivos del estudio se basaron en las preocupaciones de la FIFA por la preservación de la salud de los jugadores de fútbol y por la garantía de oportunidades iguales respecto al rendimiento físico cuando se juega a gran altura. En consecuencia se hizo un estudio comparativo entre un equipo de fútbol aclimatado a la altura de la Paz (3600 m) (equipo HAT; 10 jugadores) y otro equipo que vivía y entrenaba en una altura cercana a nivel del mar (60 m) (equipo LAT; 10 jugadores). Ambos equipos fueron estudiados en los laboratorios del Instituto Boliviano de Biología de Altura (IBBA) y en altura cercana al nivel del mar (Hotel América; Santa Cruz, 420m). La salud fue evaluada aplicando el cuestionario de Lake Louise para establecer la presencia de Enfermedad Aguda de Altura (EAA), así como mediante pruebas funcionales respiratorias y estimación de la presión arterial pulmonar sistólica(PAPs) mediante Eco Doppler. El rendimiento físico fue evaluado mediante prueba de esfuerzo máximo en rampa conmedición del consumo máximo de oxígeno (VO2max) y parámetros relacionados. Los resultados mostraron valores delVO2max algo mayores en la altura en HAT que en LAT. PAPs fue significativamente mayor a gran altura en ambos equipos. Proponemos un tiempo de aclimatación de 72 horas previa a los partidos de fútbol en La Paz en base a las estadísticas elaboradas que toman en cuenta el resultado de los partidos en relación con el tiempo de estadía en La Paz.

The present study was conducted as response to the third veto by FIFA against playing eliminatory football games forFIFA World Cups at altitudes above 2500 m. The aim of the study took into account FIFA ́s preoccupations with regard tothe health of the football players and concerning igual opportunities for physical performance when playing at high altitude. Consequently, a comparative study was conducted of two football teams, one acclimatized to the altitude of La Paz (3600m) (HAT, 10 players), and the second one living and training at an altitude close to sealevel (60 m) (LAT, 10 players). Bothteams were examined in the laboratories of he Instituto Boliviano de Biología de Altura (IBBA) and at an altitude close tosealevel (Hotel América, Santa Cruz, 420 m). Health was assessed applying the Lake Louise scoring system for AcuteAltitude Sickness as well as by measuring pulmonary function and by assessing systolic pulmonary artery pressure (PAPs)using theEcho Doppler technique. The physical capacity was measured by a progressive maximal exercise test on atreadmillwith determination of the maximal oxygen uptake (VO2max) andrelated parmeters. The results I howed a VO2max somwht higher at high altitude in HAT than in LAT. PAPs was significantly higher at high than at low altitude in bothteams. Wepropose an acclimatization time of 72 hours previous to football games in La Paz based on statistics that tookinto account the results of the games in relation to the time of the stay in La Paz.