The use of pulse oximetry is advised in order to increase detection of hypoxemia considering normal SpO2 range values at higher altitudes [6, 9]. The average SpO2 value is close to 99% at sea level and appears to decrease to 97% after 1500 to 1600 m a.s.l. [16–18]. Furthermore, at 3000 m a.s.l., mean SpO2 values of 89.6%  or even 85.7% have been reported . We have found an SpO2 mean value of 94.5% (SD 1.07) at 2800 meters, similar to those reported in studies in altitudes, e. g. Rojas-Camayo et al. at 2830 m a.s.l. with an SpO2 mean value of 95% (SD 1) , or slightly higher than that reported by Lozano et al. at Bogotá-Colombia (2600 m a.s.l.) of 93.3% (SD 2.05)  or by Nicholas et al. at Colorado (2800 m a.s.l.) of 91.7% (SD 2.1) .
Pulse oximetry is the standard of care to assess hypoxemia. It is highly cost-effective and identifies between 20 and 30% more cases than clinical signs alone [22–25]. Some studies have previously used average SpO2 values − 2SD to define hypoxemia ; however, for many of them the SpO2 value distribution is negatively biased rather than normally distributed . If 2SD are added to the mean, values higher than the theoretical maximum 100% can be obtained, a circumstance observed mainly in studies at places under 2000 m a. s. l. [9, 17, 26]. This result suggests that this definition of hypoxemia might not identify the lowest 2.5% values in moderate altitude accurately . In contrast, data expression as percentile measures can show the complete range of values and allows pediatricians to accurately assess dynamic changes in SpO2 values.
In this study, no differences in SpO2 values were observed between girls and boys neither by age, as it has been previously reported [20, 27].
Unreal SpO2 values could increase hospital admissions and hospital stays with subsequent iatrogenic risks and misuse of resources [24, 25]. Without pulse oximetry, the management of pediatric patients depends on precise identification of the clinical signs of hypoxemia, which are not always easy to assess in all patients. Clinical signs alone are unreliable for the detection of hypoxemia .
Pulse oximetry is a non-invasive and low-cost assessment method able to reduce child mortality by accurately diagnosing hypoxemia, increasing the possibilities of early and effective treatment . Our results suggest a SpO2 value > 90% (> percentile 2.5th) as the cut-off point to define “normality” in “children at community settings without respiratory symptoms and not fever living at moderate altitude”.
There are some limitations to the study. 1. Measurements were carried out in children between 1 month and 12 years of age living in Quito, so the results obtained cannot apply to patients who have not adapted. 2. All patients in the sample had their medical records and physical examination taken but did not undergo laboratory testing for parameters such as serum hemoglobin, arterial blood gas testing or chest X-rays to discard other pathologies not found on clinical evaluation. 3. In this study we did not set out to compare the SpO2 results between the group that met the inclusion criteria with the excluded group; however, this comparison could provide additional information.