Dr. Karen Parejo, President of the Colombian Association of Sleep Medicine, Dr. Santiago Ucrós, Dr. Claudia Granados, M. Sc., Dr. Fernando Guillén, Dr. Fausto Ortega, Dr. Sonia Restrepo, Fabián Gil, M. Sc. and fellow Miriam Guillén, presented important research titled: “Oxygen saturation, periodic breathing and apnea during sleep in infants 1 to 4 month old living at 2,560 meters above sea level.” Research recently published in the Arch Argent Pediatr 2015;113(4): 341-344.
There are few data in the literature related to polysomnography in infants in altitudes from 2,200 m to 2,800 m. The main objective of this investigation was to describe oxygen saturation (SpO2) levels during sleep in infants aged between 1 and 4 months living at an altitude of 2,560 m. The secondary objectives were the description of periodic breathing (PB) and apnea indexes. Polysomnography was performed in 35 healthy infants aged 1-4 months in Cuenca (Ecuador) at 2,560 m. The median for SpO2 was 92% and 4.9% for PB. The median for the central apnea
index was 23.7/hour and 15.4/hour when related to PB. No correlation was found between PB and SpO2. Conclusion: SpO2 was lower than the values at sea level and PB and central apnea indices
were higher. When apneas associated with PB were not considered, the central apnea index was similar to that found at sea level.
The research team used the Neurovirtual BW2 PSG and Sleepvirtual sensors to compile the data for this study. The Neurovirtual development team actively participated in aiding the research
team when required. A listing of the research parties are listed below:
a. Department of Pediatrics. Fundación Santa Fe de Bogotá.
b. Departments of Pediatrics and Clinical Epidemiology and Biostatistics.Pontificia Universidad Javeriana.
c. Department of Neurology and Sleep Lab. Fundación Clínica Shaio. Bogotá, Colombia.
d. Department of Pediatrics. Hospital del Río. Universidad del Azuay. Cuenca, Ecuador.
e. Department of Pediatrics. Hospital Luis Fernando Martínez. Cañar, Ecuador.
f. Departments of Pediatrics. Hospital de La Misericordia, Fundación Santa Fe de Bogotá, Universidad de los Andes.
g. Biostatistician. Department of ClinicalEpidemiology and Biostatistics. Pontificia Universidad Javeriana. Bogotá, Colombia.
h. Medical Student. Universidad del Azuay. Cuenca, Ecuador.
In this study we present the description of the SpO2 and other respiratory polysomnography parameters in infants 1-4 months of age, at 2,560 meters above sea level. The SpO2 we found wasclearly lower than values described at sea level by Schlüter et al., who for children aged 1-4 months, reported a median of 98.1% (p5, 95% – p95, 99.5%). PB, on the other hand, was significantly higher than data recorded at sea level by Kelly et al., which was lower than 1% in infants 2-4 months old, and by Schlüter et al., who found PB below 0.5% in children aged 1-4 months.The fact that PB increases with altitude has physiological bases and has been previously reported in infants. In our study, PB was significantly higher during REM sleep compared with NREM sleep; this finding is recognized since 1977.
The data on CAI that we have found is higher than that reported by Schlüter et al., who recorded a median at sea level of 5-10/hour for infants aged 1-4 months. However, in our data, when central apneas associated with PB were discounted, the CAI median was close to the value reported by these authors. These results indicate that the discrimination between isolated apneas and PB-associated apneas becomes important in high altitude conditions in this age group. If ignored, the CAI values will be largely a reflection of the PB percentage. An increase in central apneas associated with PB was reported by Parkins et al., with findings similar to ours. These authors analyzed the breathing pattern in 34 children with a mean age of 3.1 months exposed to oxygen at 15% (equivalent to a barometric pressure of 582 mm Hg), and found that apneas associated with PB increased 3.5 times with the simulated altitude, whereas the increment of isolated apneas was only of 0.15.
Recently, a study similar to ours at an altitude of 8,600 ft was published. The results agree in relation to SpO2, but CAI and PB were higher in our results. The authors report an important number of obstructive apneas that was not found by us.
The absence of correlation between PB and SpO2 represented by the SSR suggests that low SpO2 is attributable to the decreased inspiratory SpO2 characteristic of high altitudes, and not to the increase in PB. In consequence, the clinical decision to provide supplementary oxygen should be based on the SpO2 data and not with the intention of changing the PB or CAI parameters. The obstructive sleep apnea index and the mixed apnea index were 0 in all the infants taking part in this study. Values approaching 0 for these parameters have been previously reported at sea level, by Schlüter in Germany and by Kato in Belgium. The SpO2 difference between the 5th to 25th percentiles were the same as that observed between the 25th and 95th percentiles, showing a relevant difference in the physiological behavior of this parameter during sleep in about 25% of the babies. The reason why this happens, and whether there are any consequences, should be evaluated in further investigations. It could be hypothesized that some babies have a higher level of pulmonary vascular reactivity in response to the hypobaric hypoxia.
Considering the haemoglobin dissociation curve, the data obtained for SpO2 in this study can be useful as an approximation to what happens in a range of ± 1000 ft around 8200 ft of altitude, where large populations live, including cities like México DF with 21 million inhabitants, Bogotá (Colombia) with 8 million, Addis Ababa (Ethiopia) with 2.7 million, Sana’a (Yemen) with 2.5 million, Quito (Ecuador) with 2.3 million, Arequipa (Peru) and Toluca (México) with 0.8 million, and Cochabamba (Bolivia), Quetzaltenango (Guatemala) and Asmara (Eritrea) with 0.6 million.
The SpO2, RP, and IAC were all lower than the values at sea level, and the RP and the IAC are lower. When apneas associated with RP were discounted, the IAC was similar to sea level.