Abstract
Harness hang syncope (HHS) is a risk that specifically affects safety of harness users in mountain climbing.Aims: To evaluate individual patterns of breathing resulting from deranged cardiovascular reflexes triggering a syncopal event when a mismatch between cerebral O2 demand and supply is present.Results: Forty healthy participants [aged 39.1 (8.2) years] were enrolled in a motionless suspension test while hanging in harness. Respiratory gas exchange values were analyzed to assess the pattern of breathing (EpInWel, respiratory elastic power) and cardiovascular parameters were monitored (BP, blood pressure). Four participants experienced HHS after 30.0 (7.6) minutes, with an early manifestation of loss of control of both a sustainable EpInWel and BP, starting after 10–12 minutes. Among the other participants, two different reactions were observed during suspension: (1) group G1 tolerated 32.7 (11.4) minutes of suspension by a favorable adaptation of the EpInWel and BP parameters and (2) group G2 showed significantly shorter time of suspension 24.0 (10.4) minutes with unfavorable increase in EpInWel and BP.Conclusions: Greater resistance to HHS occurs in people developing less marked fluctuations of both respiratory and cardiovascular reflex responses. Conversely, wider fluctuations both in control of EpInWel and BP were observed in the event of decreased suspension tolerance or in syncopal events.
Highlights
Awide knowledge gap exists regarding the risks of hanging motionless in harness, even among experienced users
The most evident effect reported in this study is the existence of a critical amount of cerebral deoxygenation, as ascertained by a brain near-infrared spectroscopy investigation: cerebral deoxygenation eventually inhibits the cardiovascular reflexes while abruptly triggering syncopal event
In G2, V_E increased as in G1 when suspension started, it remained high during all the suspension test (ST) that were terminated when systolic blood pressure (SBP) reached values over 160 mmHg and/or one or more of the following signs were indicated: trembling, sweating, nausea, headache, and light-headedness
Summary
Awide knowledge gap exists regarding the risks of hanging motionless in harness, even among experienced users. The most distinctive effect is commonly known as suspension trauma, or more properly referred to as harness hang syncope (HHS). If prompt adjustment of posture/condition is not performed, a lethal multivisceral hypoxia arises even in the absence of a specific trauma leading to HHS (Seddon, 2002; Van Lieshout et al, 2003). Our recent study on the pathophysiology of HHS suggests that the condition that may jeopardize cerebral hypo-oxygenation develops within a few minutes after suspension (Lanfranconi et al, 2017b). The most evident effect reported in this study is the existence of a critical amount of cerebral deoxygenation, as ascertained by a brain near-infrared spectroscopy investigation: cerebral deoxygenation eventually inhibits the cardiovascular reflexes while abruptly triggering syncopal event. Death due to syncope while hanging in harness could be the unwanted, predictable consequence of a delayed rescue in HHS
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