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Reference values for oxygen saturation from sea level to the highest human habitation in the Andes in acclimatised persons

Authors:
Jose Rojas Camayo at The University of Texas Medical Branch at Galveston
Jose Rojas Camayo
Christian R. Mejia
Christian R. Mejia
David Callacondo at Universidad Peruana Cayetano Heredia
David Callacondo
Jennifer Anne Dawson at Royal Women's Hospital in Victoria
Jennifer Anne Dawson
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Abstract

Oxygen saturation, measured by pulse oximetry (SpO2), is a vital clinical measure. Our descriptive, cross-sectional study describes SpO2 measurements from 6289 healthy subjects from age 1 to 80 years at 15 locations from sea level up to the highest permanent human habitation. Oxygen saturation measurements are illustrated as percentiles. As altitude increased, SpO2 decreased, especially at altitudes above 2500 m. The increase in altitude had a significant impact on SpO2 measurements for all age groups. Our data provide a reference range for expected SpO2 measurements in people from 1 to 80 years from sea level to the highest city in the world.
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1Thorax Month 2017 Vol 0 No 0
Figure 1 2.5th, 10th, 25th, 50th, 75th, 90th, and 97.5th SpO2 percentiles for all subjects
according to altitude. (n=6289) distributed by the following altitudes: 154 m (n=709), 562 m
(n=405), 1400 m (n=315), 2000 m (n=209), 2335 m (n=522), 2500 m (n=416), 2880 m (n=404),
3250 m (n=422), 3600 m (n=361), 3950 m (n=350), 4100 m (n=644), 4338 m (n=457), 4500 m
(n=525), 4715 m (n=251), 5100 m (n=299).
Reference values for oxygen
saturation from sea level
to the highest human
habitation in the Andes in
acclimatisedpersons
ABSTRACT
Oxygen saturation, measured by pulse
oximetry (SpO2), is a vital clinical measure. Our
descriptive, cross-sectional study describes
SpO2 measurements from 6289 healthy
subjects from age 1 to 80 years at 15 locations
from sea level up to the highest permanent
human habitation. Oxygen saturation
measurements are illustrated as percentiles. As
altitude increased, SpO2 decreased, especially
at altitudes above 2500 m. The increase in
altitude had a significant impact on SpO2
measurements for all age groups. Our data
provide a reference range for expected SpO2
measurements in people from 1 to 80 years
from sea level to the highest city in the world.
BACKGROUND
Pulse oximetry has led to a great advance-
ment in patient management offering
non-invasive estimation of arterial oxygen
saturation. It is routinely used in emergency
departments, wards, intensive care and other
medical situations. At high altitudes, physi-
ological ventilation parameters like plasma
bicarbonate are different.1 Pulse oximetry
measurements of oxygen saturation (SpO2)
are lower at altitude compared with those
at sea level. However, the expected SpO2
at a given altitude is unclear and has been
suggested as a range of values rather than a
specific number.2
METHODS
Subjects
Data were collected from 15 locations
at different altitudes from sea level to
the highest permanent human habitation
located in a remote area at 5100 m in
Puno, Peru, a city named La Rinconada.3
We recruited subjects between 1 and 80
years with a minimum of 2 months resi-
dence at the place of evaluation because
alveolar gas composition is different after
acclimatisation.4 Exclusion criteria were
based on history and clinical examination.
Subjects with a history of the following
were excluded: habitual smoker (≥1 ciga-
rette day), ongoing pregnancy, chronic
cardiorespiratory disease, anaemia, poly-
cythaemia or having received a blood
transfusion in the last 6 months and with
abnormal findings in physical examina-
tion. Children who were asleep at the
time of measurement of SpO2 and subjects
with painted nails or deformities in meas-
urement locations were also excluded.
Informed consent was obtained from all
subjects or their guardians.
Measurement of SpO2
SpO2 was measured using a pulse oximeter
(Nellcor 560, Hayward, California, USA),
with sensors appropriate to the weight of the
subject. SpO2 measurements were recorded
every 10 s for a total of six measurements
and the average was used to determine
SpO2 for each study subject, as described in
previous studies.5
At the end of the study, we compared
SpO2 measurements against simultaneous
measurements of arterial oxygen satura-
tion (SaO2) by arterial blood gases in 10
hospitalised patients, at sea level. The
average of (SaO2 –SpO2) was 1.48%. This
was within the expected value of ±2%
for a range of SpO2 measurements
between 70% and 100% reported by the
manufacturer.6
To assess the reproducibility of our
data, at 5100 m, we measured SpO2
twice in 23 subjects waiting 30 min
before taking the second measurement.
For this test, we used the Fingertip Pulse
Oximeter MD300C1. The average differ-
ence between SpO2 measured by the two
devices (Nellcor-MD300C1) was −0.8%.
STATISTICAL ANALYSIS
Descriptive statistics were used to summa-
rise characteristics of the subjects.
Constructing oxygen centile charts
SpO2 data were entered into Microsoft
Excel and were analysed and charted using
Stata (Intercooled 10, Stata Corp, College
Station, Texas, USA). The SpO2 centiles
were calculated using the LMS method
of Cole and Green7 8 and fitted using
the LMSChartMaker Light V.2.3 (Insti-
tute of Child Health, London, England).
These values were then used to illustrate
the 2.5th, 10th, 25th, 50th, 75th, 90th
and 97.5th centile for SpO2 for each age
group according to residential altitude
(see online supplement).
RESULTS
We studied subjects residing at 15 specific
altitudes. We initially evaluated 6601
subjects. Three hundred and twelve met
exclusion criteria. A total of 6289 subjects
were studied: 47.2% (n=2967) males and
52.8% females (n=3322). The median
(IQR) for all SpO2 measurements at each
altitude (metre) were respectively: 99
(98–99) at 154 m; 99 (98–99) at 562 m; 98
(97–99) at 1400 m; 97 (96–98) at 2000 m;
97 (96–99) at 2335 m; 96 (95–97) at
2500 m; 95 (94–96) at 2880 m; (92–95) at
3250 m; 92 (90–93) at 3600 m; 90 (88–91)
at 3950 m; 87 (85–89) at 4100 m; 87
(85–89) at 4338 m; 87 (85–89) at 4500 m;
Research Letter
Thorax Online First, published on October 20, 2017 as 10.1136/thoraxjnl-2017-210598
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2Thorax Month 2017 Vol 0 No 0
Figure 2 2.5th, 10th, 25th, 50th, 75th, 90th, and 97.5th SpO2 percentiles for children. (A) Represents children 1–5 years (n=994) with N for specific
altitude in the same order as figure1 (n=64, 91, 69, 26, 70, 87, 95, 140, 30, 46, 91, 47, 36, 28, 74). (B) Represents children 6–17 years (n=2379)
(n=281, 144, 146, 116, 171, 234, 122, 181, 117, 202, 117, 126, 121, 133, 168). Adults 18–50 (C) (n=2195) (n=310, 120, 28, 40, 239, 70, 134, 56, 136,
45, 297, 247, 353, 68, 52) and 51–80 years (D) (n=721) (n=54, 50, 72, 27, 42, 25, 53, 45, 78, 57, 139, 37, 15, 22, 5), adults according to altitude.
Research Letter
85(83–88) at 4715 m; 81 (78–84) at 5100 m.
Oxygen saturation measurements
SpO2 measurements illustrated as percen-
tiles are shown for all subjects in figure 1,
and by age group (1–5, 6–17, 18–50 and
51–80 years) in figure 2. The figures
show that for all age groups, as altitude
increased, SpO2 decreased, especially
at altitudes above 2500 m (see online
supplement tables).
DISCUSSION
We obtained measurements from over
6000 subjects, from 1 to 80 years old,
from sea level to the highest permanent
human habitation located in Peru at
5100 m.3 This is the first study to provide
reference charts for the expected range
of SpO2 measurements by age group and
altitude using centiles by the LMS method.
We have shown the expected reduc-
tion of SpO2 with altitude, an effect that
is more evident at altitudes over 2500 m.
We have also shown increased variability
in the range of SpO2 measurements at
higher altitudes. Our observation could
be explained by a genetic variability in the
hypoxic ventilatory response. It is note-
worthy that at 5100 m, the median SpO2
of 81% could correspond to a PO2 less
than 50 mm Hg according to the oxygen
dissociation curve. This is less than half of
the normal PO2 at sea level.
Pulse oximetry utility in clinical care
outside the operating theatre has been
supported by studies at sea level and at high
altitude.9 Having a reference value for SpO2
is needed in clinical management at high
altitude locations.
There are some limitations to our find-
ings and analysis. We did not enrol subjects
over 80 years or children less than 1 year.
Our study does not apply to non-acclima-
tised individuals. We did take a clinical
history and conducted a physical exami-
nation of all subjects. However, we did
not conduct further testing, such as chest
radiography, spirometry or haemoglobin
measurement, to rule out pathology not
evidenced by clinical examination. There-
fore, in evaluating patients at high altitude,
their history and clinical presentation must
be incorporated into deciding whether an
individual SpO2 measurement should raise
concern for a patient at their usual resi-
dential altitude.
All our subjects were Andean Natives and
Hispanics and care should therefore be taken
in applying these results to other ethnicities
and to other parts of the world. For example,
Tibetans have different physiological traits
for the oxygen delivery process10 and might
have different SpO2 measurements at the
same altitude as our subjects.
In conclusion, our data provide a refer-
ence range for SpO2 in people from 1 to 80
years from sea level to the highest city in the
world, contributing to global knowledge of
expected SpO2 measurements at any given
habitable altitude.
Jose Rojas-Camayo,1 Christian Richard Mejia,2
David Callacondo,3 Jennifer A Dawson,4
Margarita Posso,5 Cesar Alberto Galvan,6
Nadia Davila-Arango,7 Erick Anibal Bravo,8
Viky Yanina Loescher,9
Magaly Milagros Padilla-Deza,10
Nora Rojas-Valero,11 Gary Velasquez-Chavez,12
Jose Clemente,13 Guisela Alva-Lozada,14
Angel Quispe-Mauricio,15 Silvana Bardalez,16
Rami Subhi17
1Instituto de Investigaciones de la Altura, Universidad
Peruana Cayetano Heredia, Lima, Peru
2Escuela de Medicina Humana, Universidad Continental,
Huancayo, Peru
3School of Medicine, Faculty of Health Sciences.,
Universidad Privada de Tacna., Tacna, Peru
4The Royal Women’s Hospital, Melbourne, Australia
5Department of Epidemiology and Evaluation, Hospital
del Mar Medical Research Institute, Barcelona, Spain
6Centro de Referencia Nacional de Alergia, Asma e
Inmunologia (CERNAAI), Instituto Nacional de Salud
del Niño, Lima, Peru
7Hospital Clínico Universitario de Salamanca,
Salamanca, Spain
group.bmj.com on October 23, 2017 - Published by http://thorax.bmj.com/Downloaded from
3Thorax Month 2017 Vol 0 No 0
Research Letter
8Hospital Nacional Dos de Mayo, Institute of Clinical
Research, Lima, Peru
9Mount Sinai Medical Center, Miami, USA
10Resocentro, Lima, Peru
11Hospital Nacional Guillermo Almenara Irigoyen, Lima,
Peru
12Centro de Salud Zalfonada, Zaragoza, Spain
13Hospital Nacional Hipólito Unanue, Lima, Peru
14Hospital Nacional Edgardo Rebagliati Martins, Lima,
Peru
15Hospital Universitario Príncipe de Asturias, Madrid,
Spain
16Clinica Concebir, Lima, Peru
17Center for international Child Health, University
of Melbourne, Royal Children’s Hospital, Melbourne,
Australia
Correspondence to Dr Jose Rojas-Camayo,
Universidad Peruana Cayetano Heredia, Lima 31, Peru;
joserojas18@ hotmail. com
Contributors All authors were involved in the design
of the study and collection of clinical data. JAD, JRC
and CRM performed the data analysis. JRC, CRM, DC,
JAD, MP, VYL and RS drafted the final manuscript and
all authors reviewed and made amendments.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Ethics Committee at Hospital
Nacional Docente Madre Niño San Bartolomé, Lima-
Peru.
Provenance and peer review Not commissioned;
externally peer reviewed.
© Article author(s) (or their employer(s) unless
otherwise stated in the text of the article) 2017. All
rights reserved. No commercial use is permitted unless
otherwise expressly granted.
►Additional material is published online only. To
view please visit the journal online (http:// dx. doi. org/
10. 1136/ thoraxjnl- 2017- 210598)
To cite Rojas-CamayoJ, MejiaCR, CallacondoD, etal.
Thorax Published Online First: [please include Day
Month Year]. doi:10.1136/thoraxjnl-2017-210598
Received 5 June 2017
Revised 6 September 2017
Accepted 25 September 2017
Thorax 2017;0:1–3.
doi:10.1136/thoraxjnl-2017-210598
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the Andes in acclimatised persons
sea level to the highest human habitation in
Reference values for oxygen saturation from
Alva-Lozada, Angel Quispe-Mauricio, Silvana Bardalez and Rami Subhi
Nora Rojas-Valero, Gary Velasquez-Chavez, Jose Clemente, Guisela
Padilla-Deza,Erick Anibal Bravo, Viky Yanina Loescher, Magaly Milagros
Davila-Arango,A Dawson, Margarita Posso, Cesar Alberto Galvan, Nadia
Jose Rojas-Camayo, Christian Richard Mejia, David Callacondo, Jennifer
published online October 20, 2017Thorax
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  • Feb 2025
  • PEDIATR CRIT CARE ME
Objectives We evaluated the Phoenix criteria and the Phoenix Sepsis Score in a multicenter retrospective cohort of critically ill children with a clinical diagnosis of sepsis or septic shock in Bolivia. In addition, we aimed to assess whether management in a PICU at high altitude in the Bolivian Andes was associated with the performance of the respiratory dysfunction component in the Phoenix Sepsis Score. Design Multicenter retrospective cohort study. Setting Fourteen PICUs in Bolivia. Patients Children admitted to the PICU with a clinical diagnosis of sepsis or septic shock from January 2023 to December 2023. Interventions None. Measurements and Main Results There were 273 patients with a diagnosis of sepsis in 2023, of which 257 (94.1%) met the 2024 Phoenix criteria for sepsis, and 166 (60.8%) met the systemic inflammatory response syndrome (SIRS)-based criteria for sepsis. Among the 257 patients meeting Phoenix sepsis criteria, 86 died (33.5%). Of the patients with Phoenix-based sepsis, there were 100 of 257 (38.9%) who were SIRS-negative, and 27 of 100 died (27.0%). After correcting the oxygenation indices for altitude, 149 of 273 patients (54.6%) had a lower Phoenix respiratory score and an associated mortality more consistent with the expected mortality of the newly derived subscore. Patients at higher altitudes had higher hemoglobin levels and higher estimated oxygen carrying capacity, and these data were independently associated with lower odds of mortality after controlling for altitude-corrected Phoenix score. Conclusions In this 2023, retrospective cohort of PICU patients with sepsis in Bolivia, we have found that the majority met the 2024 Phoenix sepsis criteria, but less than two-thirds met the SIRS-based criteria for diagnosis. However, the respiratory score in the Phoenix criteria overestimated the severity of respiratory dysfunction in more than half of the cohort, likely because the score does not take account of the Andean adaptation to high altitude, with higher oxygen carrying capacity.
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TcPO2 changes are more pronounced than SpO2 changes during simulated altitude changes in a hypobaric oxygen chamber: a nonrandomized controlled trial
Article
  • Jun 2024
Background Hypoxia is a significant risk factor of hypertension. However, no studies have used transcutaneous tissue partial pressure of oxygen (TcPO 2 ) and partial pressure of carbon dioxide (TcPCO 2 ) monitors to measure the respective partial pressures in healthy individuals. Oxygen saturation (SpO 2 ) is often used for traditional monitoring of vital signs. This study investigated the changes in TcPO 2 and SpO 2 values during rapid changes in altitude. The trial was registered at ClinicalTrials.gov (registration no. NCT06076057). Methods Healthy adult volunteers were instructed to sit vertically in a hypobaric oxygen chamber, which ascended from 0 m to 2500 m at a uniform speed within 10 min. The Danish Radiometer TCM4 was used to measure TcPO 2 and TcPCO 2 with the ventral side of the upper arm as the measurement site. The Shenzhen Kerokan P0D-1 W pulse oximeter was used to measure heart rate and SpO 2 , with values recorded once every 500 m. Results Altogether, 49 healthy volunteers were recruited between March 2023 and August 2023. With increasing altitude, TcPO 2 and SpO 2 decreased significantly ( P < 0.01). During the ascent from 0 m, TcPO 2 began to change statistically at 500 m ( P < 0.05), whereas SpO 2 began to change statistically at 1000 m ( P < 0.05). At the same altitude, the difference in TcPO 2 was greater than the difference in SpO 2 . At 1000 m, there were statistically significant changes in TcPO 2 and SpO 2 ( P < 0.001). At altitudes >500 m, statistical significance was identified between TcPO 2 in both sexes ( P < 0.05). Statistical significance in TcPCO 2 and heart rate was observed at the different elevations ( P < 0.05). Conclusion In acutely changing low-pressure hypoxic environments, TcPO 2 changed more dramatically than SpO 2 .
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Bicarbonate Values for Healthy Residents Living in Cities Above 1500 Meters of Altitude: A Theoretical Model and Systematic Review
Article
Full-text available
  • Apr 2016
  • HIGH ALT MED BIOL
Ramirez-Sandoval, Juan C., Maria F. Castilla-Peón, José Gotés-Palazuelos, Juan C. Vázquez-García, Michael P. Wagner, Carlos A. Merelo-Arias, Olynka Vega-Vega, Rodolfo Rincón-Pedrero, and Ricardo Correa-Rotter. Bicarbonate values for healthy residents living in cities above 1500 m of altitude: a theoretical model and systematic review. High Alt Med Biol 00:000-000, 2016-Plasma bicarbonate (HCO3(-)) concentration is the main value used to assess the metabolic component of the acid-base status. There is limited information regarding plasma HCO3(-) values adjusted for altitude for people living in cities at high altitude defined as 1500 m (4921 ft) or more above sea level. Our aim was to estimate the plasma HCO3(-) concentration in residents of cities at these altitudes using a theoretical model and compare these values with HCO3(-) values found on a systematic review, and with those venous CO2 values obtained in a sample of 633 healthy individuals living at an altitude of 2240 m (7350 ft). We calculated the PCO2 using linear regression models and calculated plasma HCO3(-) according to the Henderson-Hasselbalch equation. Results show that HCO3(-) concentration falls as the altitude of the cities increase. For each 1000 m of altitude above sea level, HCO3(-) decreases to 0.55 and 1.5 mEq/L in subjects living at sea level with acute exposure to altitude and in subjects acclimatized to altitude, respectively. Estimated HCO3(-) values from the theoretical model were not different to HCO3(-) values found in publications of a systematic review or with venous total CO2 measurements in our sample. Altitude has to be taken into consideration in the calculation of HCO3(-) concentrations in cities above 1500 m to avoid an overdiagnosis of acid-base disorders in a given individual.
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Pulse Oximetry at High Altitude
Article
Full-text available
  • Jun 2011
  • HIGH ALT MED BIOL
Pulse oximetry is a valuable, noninvasive, diagnostic tool for the evaluation of ill individuals at high altitude and is also being increasingly used to monitor the well-being of individuals traveling on high altitude expeditions. Although the devices are simple to use, data output may be inaccurate or hard to interpret in certain situations, which could lead to inappropriate clinical decisions. The purpose of this review is to consider such issues in greater detail. After examining the operating principles of pulse oximetry, we describe the available devices and the potential uses of oximetry at high altitude. We then consider the pitfalls of pulse oximetry in this environment and provide recommendations about how to deal with these issues. Device users should recognize that oxygen saturation changes rapidly in response to small changes in oxygen tensions at high altitude and that device accuracy declines with arterial oxygen saturations of less than 80%. The normal oxygen saturation at a given elevation may not be known with certainty and should be viewed as a range of values, rather than a specific number. For these reasons, clinical decisions should not be based on small differences in saturation over time or among individuals. Effort should also be made to minimize factors that cause measurement errors, including cold extremities, excess ambient light, and ill-fitting oximeter probes. Attention to these and other issues will help the users of these devices to apply them in appropriate situations and to minimize erroneous clinical decisions.
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Two Routes to Functional Adaptation: Tibetan and Andean High-Altitude Natives
Article
Full-text available
  • Jun 2007
Populations native to the Tibetan and Andean Plateaus are descended from colonizers who arrived perhaps 25,000 and 11,000 years ago, respectively. Both have been exposed to the opportunity for natural selection for traits that offset the unavoidable environmental stress of severe lifelong high-altitude hypoxia. This paper presents evidence that Tibetan and Andean high-altitude natives have adapted differently, as indicated by large quantitative differences in numerous physiological traits comprising the oxygen delivery process. These findings suggest the hypothesis that evolutionary processes have tinkered differently on the two founding populations and their descendents, with the result that the two followed different routes to the same functional outcome of successful oxygen delivery, long-term persistence and high function. Assessed on the basis of basal and maximal oxygen consumption, both populations avail themselves of essentially the full range of oxygen-using metabolism as populations at sea level, in contrast with the curtailed range available to visitors at high altitudes. Efforts to identify the genetic bases of these traits have included quantitative genetics, genetic admixture, and candidate gene approaches. These reveal generally more genetic variance in the Tibetan population and more potential for natural selection. There is evidence that natural selection is ongoing in the Tibetan population, where women estimated to have genotypes for high oxygen saturation of hemoglobin (and less physiological stress) have higher offspring survival. Identifying the genetic bases of these traits is crucial to discovering the steps along the Tibetan and Andean routes to functional adaptation.
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Fitting Smoothed Centile Curves to Reference Data
Article
  • Jan 1988
A general method is described for fitting smooth centile curves to reference data, based on the power transformation family of Box and Cox. The data are defined by values or ranges of values of the independent variable t, and best fitting powers λ^i\hat\lambda_i assuming normality are estimated for each group i. Corresponding estimates for the generalized mean and coefficient of variation μ^i\hat\mu_i and σ^i\hat\sigma_i are also obtained. The λ^i,μ^i\hat\lambda_i, \hat\mu_i and σ^i\hat\sigma_i plotted against ti are fitted by smooth curves L(t), M(t) and S(t) respectively, which together define a smooth curve for the 100αth centile given by C100α(t) = M(t)[ 1 + L(t)S(t)zα]1/L(t), where zα is the normal equivalent deviate for tail area α. The method is validated by comparison with published growth standards and illustrated on weight and height data in children. A section describing the practical details of the method is also included.
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Smoothing Reference Centile Curves: The LMS Method and Penalized Likelihood
Article
  • Jul 1992
Refence centile curves show the distribution of a measurement as it changes according to some covariate, often age. The LMS method summarizes the changing distribution by three curves representing the median, coefficient of variation and skewness, the latter expressed as a Box-Cox power. Using penalized likelihood the three curves can be fitted as cubic splines by non-linear regression, and the extent of smoothing required can be expressed in terms of smoothing parameters or equivalent degrees of freedom. The method is illustrated with data on triceps skinfold in Gambian girls and women, and body weight in U.S.A. girls.
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Prevalence and prediction of hypoxemia in children with respiratory infections in the Peruvian Andes
Article
  • Jan 1992
  • J Pediatr
To determine the effect of respiratory infections on oxyhemoglobin saturation in a high-altitude population, we recorded clinical signs, oxyhemoglobin saturation determined by pulse oximetry, and findings on radiographs of the chest of 423 children with acute respiratory infections; the children were living at an altitude of 3750 m in the Peruvian Andes. We defined hypoxemia as an oxyhemoglobin saturation value greater than 2 SD below the mean value for 153 well children in this population. Eighty-three percent of children with clinical bronchopneumonia, but only 10% of children with upper respiratory tract infection, had hypoxemia (p less than 0.001). Compared with previous studies of children living at lower altitudes, the presence of tachypnea was relatively nonspecific as a predictor of radiographically determined pneumonia or of hypoxemia, especially in infants. A history of rapid breathing was 74% sensitive and 64% specific in the prediction of hypoxemia, and performed as well as a standard World Health Organization case management algorithm in the prediction of radiographic pneumonia or hypoxemia. Radiographic pneumonia was not a sensitive predictor of hypoxemia or clinically severe illness. In contrast, the presence of hypoxemia was a useful predictor of radiographic pneumonia, with both sensitivity and specificity of 75% in infants. We conclude that acute lower respiratory tract infection in children living at high altitude is frequently associated with hypoxemia, and that oxygen should be administered to children with a diagnosis of pneumonia in these regions. Case management algorithms developed in low-altitude regions may have to be modified for high-altitude settings. In this setting, pulse oximetry is a good predictor of pneumonia. Because pulse oximetry is more objective and cheaper than radiography, its role as a clinical and investigative tool merits further exploration.
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Percent of oxygen saturation of arterial hemoglobin among Bolivian Aymara at 3,900-4,000 m
Article
  • Jan 1999
A range of variation in percent of oxygen saturation of arterial hemoglobin (SaO2) among healthy individuals at a given high altitude indicates differences in physiological hypoxemia despite uniform ambient hypoxic stress. In populations native to the Tibetan plateau, a significant portion of the variance is attributable to additive genetic factors, and there is a major gene influencing SaO2. To determine whether there is genetic variance in other high-altitude populations, we designed a study to test the hypothesis that additive genetic factors contribute to phenotypic variation in SaO2 among Aymara natives of the Andean plateau, a population geographically distant from the Tibetan plateau and with a long, separate history of high-altitude residence. The average SaO2 of 381 Aymara at 3,900-4,000 m was 92+/-0.15% (SEM) with a range of 84-99%. The average was 2.6% higher than the average SaO2 of a sample of Tibetans at 3,800-4,065 m measured with the same techniques. Quantitative genetic analyses of the Aymara sample detected no significant variance attributable to genetic factors. The presence of genetic variance in SaO2 in the Tibetan sample and its absence in the Aymara sample indicate there is potential for natural selection on this trait in the Tibetan but not the Aymara population.
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Highest Permanent Human Habitation
Article
  • Feb 2002
The aim of this analysis was to determine the altitude of the highest permanent human habitation in the hope that this will throw some light on what determines the highest altitude that a community can tolerate indefinitely. A number of places where people have lived at very high altitudes for long periods of time are reviewed. Individuals have lived for as long as 2 yr at an altitude of 5950 m, and there was a miner's camp at 5300 m for several years. The highest permanently inhabited town in the world at the present time appears to be La Rinconada, a mining village of over 7000 people in southern Peru at an altitude of up to 5100 m, which has been in existence for over 40 yr. The altitude of the highest permanent human habitation is determined partly by economic factors, rather than solely by human tolerance to hypoxia.
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Operator's Manual. OxiMax N-560
  • Covidien
Covidien. Operator's Manual. OxiMax N-560. pulse oximeter. http://www. medtronic. com/ content/ dam/ covidien/ library/ us/ en/ product/ pulse-oximetry/ N560_