Nocturnal pulse oxygen saturation dynamics at simulated high altitude: Predictive value for acute mountain sickness in healthy men born pre‐term

The physiological sequelae of pre-term birth might influence the responses of this population to hypoxia. Moreover, identifying variables associated with development of acute mountain sickness (AMS) remains a key practically significant area of altitude research. We investigated the effects of pre-term birth on nocturnal oxygen saturation ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> ) dynamics and assessed the predictive potential of nocturnal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> -related metrics for morning AMS in 12 healthy adults with gestational age < 32 weeks (pre-term) and 12 term-born control participants. Participants spent one night at a simulated altitude of ∼4200 m (normobaric hypoxia; fraction of inspired O₂= 0.141), with nocturnal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> and heart rate recorded continuously at the fingertip using pulse oximetry and with morning AMS assessed using the Lake Louise scale. Pre-term and term-born participants had similar nocturnal mean <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> (mean ± SD; 77% ± 3% vs. 77% ± 4%; P = 0.661), minimum <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> (median[IQR]; 67[4]% vs. 69[5]%; P = 0.223), relative time spent with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> < 80% (72% ± 29% vs. 70% ± 27%; P = 0.879) and mean heart rate (79 ± 12 vs. 71 ± 7 beats/min; P = 0.053). However, the increase in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> between the two halves of the night was blunted with prematurity (-0.12% ± 1.51% vs. 1.11% ± 0.78%; P = 0.021). Moreover, the cumulative relative desaturation-based hypoxic 'load' was higher with prematurity (32[26]%min/h vs. 7[25]%min/h; P = 0.039), underpinned by increased desaturation frequency (69[49] vs. 21[35] counts/h; P = 0.009). Mean <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> , minimum <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> , morning <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> and relative time spent with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> < 80% predicted AMS incidence better than a random classifier exclusively in the pre-term group, with no other variables predictive of AMS in the two groups separately or combined. Overall, pre-term birth might alter nocturnal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>S</mml:mi> <mml:mrow><mml:mi>p</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> <mml:annotation>${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$</mml:annotation></mml:semantics> </mml:math> dynamics and influence AMS prediction in severe hypoxia.