Urinary physiology and hypoxia: a pilot study of moderate-altitude trekking effects on urodynamic indexes

Abstract

Exposure to high altitude is one of the most widely used models to study the adaptive response to hypoxia in humans. However, little is known about the related effects on micturition. The present study addresses the adaptive urinary responses in four healthy adult lowlanders, comparing urodynamic indexes at Kathmandu [1,450 m above sea level (a.s.l.); K1450] and during a sojourn in Namche Bazar (3,500 m a.s.l.; NB3500). The urodynamic testing consisted of cistomanometry and bladder pressure/flow measurements. Anthropometrics, electrocardiographic, and peripheral capillary oxygen saturation data were also collected. The main findings consisted of significant reductions in bladder power at maximum urine flow by ~30%, bladder contractility index by 13%, and infused volume both at first (by 57%) and urgency sensation (by 14%) to urinate, indicating a reduced cystometric capacity, at NB3500. In addition to the urinary changes, we found that oxygen saturation, body mass index, body surface area, and median RR time were all significantly reduced at altitude. We submit that the hypoxia-related parasympathetic inhibition could be the underlying mechanism of both urodynamic and heart rate adaptive responses to high-altitude exposure. Moreover, increased diuresis and faster bladder filling at altitude may trigger the anticipation of being able to void, a common cause of urgency. We believe that the present pilot study represents an original approach to the study of urinary physiology at altitude.

Exposure to acute normobaric hypoxia results in adaptions of both the macro- and microcirculatory system

“…Since hypoxaemia, defined as a decrease in arterial oxygen tension 8 , is also a predominant feature of the high-altitude environment, research on the pathophysiologic processes behind hypoxia was significantly facilitated with the advent of altitude simulation tests 9 . On the cellular level, hypoxic stress initiates a transcriptional response by hypoxia inducible factors (HIF; during intermittent hypoxia predominately HIF-1α [10][11][12], which leads to a reduction of cellular energy consumption, a secretion of pro-angiogenic and survival factors 10 , and qualitative changes in mitochondrial function 13 , which in turn results in alterations of the cardiovascular, haematological and even urinary physiology 14,15 . Among the observed physiological alterations in response to hypoxia, the effects on the human macrocirculatory system have been subject to several extensive scientific investigations in the past.…”

The “ON-OFF” Switching Response of Reactive Oxygen Species in Acute Normobaric Hypoxia: Preliminary Outcome

“…A growing body of evidence indicates that hypoxia decreases both the activity and effectiveness of the antioxidant system, as well as causing increased ROS production with a consequent increase in oxidative damage [ 3 ] to lipids [ 4 , 5 , 6 ], proteins and the DNA [ 5 , 7 ] of cellular compartments [ 8 , 9 , 10 ]. Most studies on the effects of hypoxia have been carried out at high altitude [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. However, under such conditions, several factors other than hypoxia could induce oxidative damage; UV radiation, intense physical activity and cold may in fact produce an imbalance between ROS generation and antioxidant protection [ 17 , 18 ].…”

Ethnic Differences on Cardiac Rhythms and Autonomic Nervous System Responses During a High-Altitude Trek: A Pilot Study Comparing Italian Trekkers to Nepalese Porters

“…Indeed, the recent development of non-linear metrics allowed to extend the methodological rationale of HRV, e.g., Gomes and colleagues (Gomes et al, 2017 ) reported physical exercise to acutely reduce the chaotic behavior of heart rate dynamics, through the complex Higuchi Fractal Dimension (HFD) analysis. Indeed, alternative approaches to the typical HRV investigation may add novel interpretation levels to the non-uniform alterations in the several HRV domains observed in response to altitude exposure (Verratti et al, 2019 ). Dhar et al ( 2018 ) reported higher mean RR, LF (low frequency) power ms 2 , LF (normalized units: nu), and LF/HF ratio values, with lower RMSSD (root mean square of successive RR interval differences), NN50, pNN50 (percentage of successive RR intervals that differ by more than 50 ms), SD1 (Poincaré plot standard deviation perpendicular the line of identity), HF (high frequency) power ms 2 and HF (nu) values, in acclimatized lowlanders (15–18 months residence at >3,500 m asl) compared to HAs native and sea-level residents never exposed to HAs.…”