Why the study?
Hypoxia triggers exaggerated increases in MSNA and may disturb neurovascular regulation; the authors hypothesized it would elicit greater blood pressure variability in hypertensive individuals versus normotensive controls.
Does acute isocapnic hypoxia elicit greater blood pressure variability and disrupt sympathetic transduction more in untreated hypertensive men compared to normotensive controls?
Does acute isocapnic hypoxia elicit greater blood pressure variability and disrupt sympathetic transduction more in untreated hypertensive men compared to normotensive controls?
Acute hypoxia similarly exacerbates blood pressure variability and disrupts baroreflex function in both normotensive and untreated hypertensive men, despite exaggerated sympathetic nerve activity in the hypertensive group.
Acute hypoxia elicits similar BP variability and baroreflex impairment in both groups despite greater MSNA in hypertension; leaves open differential risk during hypoxic stress.
Background Hypoxia is a common feature of arterial hypertension that does not consistently elevate blood pressure (BP), but triggers exaggerated increases in muscle sympathetic nerve activity (MSNA) and may disturb sympathetic transduction and baroreflex sensitivity in hypertensive individuals. Elevated resting MSNA, enhanced sympathetic transduction, and reduced baroreflex sensitivity are all associated with increased blood pressure variability (BPV), a marker of target organ damage independent of absolute BP levels. We hypothesized that hypoxia would elicit greater BPV in hypertensive individuals compared to normotensive controls Methods Nine young- to middle-aged men with untreated stage 1–2 hypertension (HT) and normotensive controls (NT) were exposed to normoxia (21% O 2 ) and isocapnic hypoxia (IH, 10% O 2 ). During both conditions, oxygen saturation, beat-to-beat BP, MSNA, and end-tidal CO 2 (PetCO 2 ) were continuously monitored, with PetCO 2 clamped. BPV was quantified using standard deviation, coefficient of variation, and average real variability for systolic (SBP), diastolic (DBP), and mean BP (MBP). Sympathetic transduction was assessed using a time-domain signal averaging technique. Cardiac baroreflex sensitivity (cBRS) was evaluated using the sequence method, and sympathetic baroreflex sensitivity (sBRS) was calculated via MSNA–DBP regression Results IH induced comparable oxygen desaturation in both groups (NT: −25.7 ± 3.3% vs. HT: −21.2 ± 4.0%, p > 0.05). Although BP and PetCO 2 remained unchanged, MSNA responses were significantly greater in HT (NT: +8 ± 2 vs. HT: +12 ± 2 bursts/min, p = 0.03). IH increased all indices of BPV and sympathetic transduction, while both cBRS and sBRS were similarly impaired in the two groups. Conclusions In conclusion, IH similarly exacerbates BPV and disrupts sympathetic transduction and baroreflex function in normotensive and untreated hypertensive men, despite greater MSNA reactivity in the hypertensive group.
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Ojikutu et al. (2025) studied this question.
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