Author(s): NARANG, B., MANFERDELLI, G., MILLET, G., DEBEVEC, T., Institution: JOŽEF STEFAN INSTITUTE, Country: SLOVENIA, Abstract-ID: 731

INTRODUCTION:
Specific responses to hypoxia at rest and during exercise have been observed in healthy adults born pre-term [1]. Nocturnal pulse oxygen saturation (SpO2) recordings, together with acute mountain sickness (AMS) assessment, could offer insights into the aetiology of prematurity-related altitude (in)tolerance.
METHODS:
In this study, 12 pre-term (Mean±SD; age: 21±3 yr, BMI: 23±3 kg/m^2, gestational age: 29±2 wk) and 12 term-born (22±3 yr, 23±2 kg/m^2, 40±1 wk) male adults underwent an overnight normobaric hypoxic exposure equivalent to 4200 m. AMS was assessed using the Lake Louise scale 6 h after hypoxic room entry (9pm), and the following morning 1 h after waking (7am). Participants were classified as AMS+ if their total symptom score was ≥3, with a headache score ≥1 [2]. SpO2 was recorded continuously at 3 Hz at the fingertip. Data from 11pm to 5am were extracted, and mean SpO2 and proportion of the 6 h with SpO2<80% (TST80) were calculated. Desaturations were defined by rate (>0.1%/s), magnitude (≥2%), and total duration until re-saturation (≥10 s & ≤60 s) [2]. The cumulative desaturation areas above the curve, relative to each respective onset value, indicated the hypoxic burden (%min/h). Groups were compared using independent t-tests and Mann-Whitney U tests, and are reported as Mean±SD and Median[IQR], respectively. Receiver operating characteristic (ROC) analysis was used to indicate the predictive potential of SpO2 metrics for morning AMS incidence. The area under the ROC curve (AUC) is reported, representing the balance between true- and false-positive AMS classifications.
RESULTS:
Before sleep, 9 term-born and 7 pre-term participants were AMS+. Upon waking, 5 term-born and 6 pre-term participants were AMS+. Nocturnal mean SpO2 was similar between the pre-term and term-born groups (77±3 vs 77±4%; p=0.661), as was TST80 (72±29 vs 70±27%; p=0.879). However, mean SpO2 and TST80 predicted morning AMS considerably better in the pre-term (AUC=0.889 and 0.944, respectively) than in term-born (AUC=0.457 and 0.571, respectively) participants. Pre-term adults experienced more desaturations (413[291] vs 122[209]; p=0.008), albeit shorter in average duration (17±2 vs 21±2 s; p<0.001). Pre-term participants also experienced a significantly greater hypoxic burden (32[26] vs. 7[25] %min/h; p=0.039). However, desaturation-related metrics did not predict morning AMS incidence accurately in the two groups separately or combined (all AUC<0.743).
CONCLUSION:
These data indicate high predictive potential of composite nocturnal SpO2 metrics for AMS incidence in healthy adults born pre-term. However, while desaturations were more frequent in pre-term adults, inducing a greater hypoxic burden, they were neither predictive of AMS-related outcomes in pre-term participants, nor in their term-born counterparts.

References
[1] Narang et al (2022) Eur J Appl Physiol. 122(9), 1991-2003.
[2] Roach et al (2018) High Alt Med Biol. 19(1), 4-6.
[3] Taha et al (1997) Sleep. 20(11), 991-1001.