Browsing by Subject "Altitude"

Now showing 1 - 3 of 3
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    Abdominal Pain at an Altitude
    (Elsevier, 2022-04) Russ, Jason; Kara, Areeba; Medicine, School of Medicine
    A 29-year-old man presented for evaluation to the Emergency Department with 3 days of worsening abdominal pain. The pain was described as severe and was located in the left lower quadrant without radiation. It improved with assuming the supine position and was exacerbated by movement. On the day of presentation, he developed nausea, vomiting, and diarrhea. He was traveling in Peru when the pain began and thought it was related to something he ate, so he did not initially seek medical attention. Upon returning to the United States, he sought evaluation as his symptoms escalated. He had no known chronic medical problems and was not taking any prescription medications.
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    Physiology-Enhanced Data Analytics to Evaluate the Effect of Altitude on Intraocular Pressure and Ocular Hemodynamics
    (MDPI, 2022) Verticchio Vercellin, Alice; Harris, Alon; Belamkar, Aditya; Zukerman, Ryan; Carichino, Lucia; Szopos, Marcela; Siesky, Brent; Quaranta, Luciano; Bruttini, Carlo; Oddone, Francesco; Riva, Ivano; Guidoboni, Giovanna; Ophthalmology, School of Medicine
    Altitude affects intraocular pressure (IOP); however, the underlying mechanisms involved and its relationship with ocular hemodynamics remain unknown. Herein, a validated mathematical modeling approach was used for a physiology-enhanced (pe-) analysis of the Mont Blanc study (MBS), estimating the effects of altitude on IOP, blood pressure (BP), and retinal hemodynamics. In the MBS, IOP and BP were measured in 33 healthy volunteers at 77 and 3466 m above sea level. Pe-retinal hemodynamics analysis predicted a statistically significant increase (p < 0.001) in the model predicted blood flow and pressure within the retinal vasculature following increases in systemic BP with altitude measured in the MBS. Decreased IOP with altitude led to a non-monotonic behavior of the model predicted retinal vascular resistances, with significant decreases in the resistance of the central retinal artery (p < 0.001) and retinal venules (p = 0.003) and a non-significant increase in the resistance in the central retinal vein (p = 0.253). Pe-aqueous humor analysis showed that a decrease in osmotic pressure difference (OPD) may underlie the difference in IOP measured at different altitudes in the MBS. Our analysis suggests that venules bear the significant portion of the IOP pressure load within the ocular vasculature, and that OPD plays an important role in regulating IOP with changes in altitude.
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    Ventilatory Responsiveness during Exercise and Performance Impairment in Acute Hypoxia
    (Wolters Kluwer, 2021-02-01) Constantini, Keren; Bouillet, Anna C.; Wiggins, Chad C.; Martin, Bruce J.; Chapman, Robert F.; Medicine, School of Medicine
    Introduction: An adequate increase in minute ventilation to defend arterial oxyhemoglobin saturation (SpO2) during hypoxic exercise is commonly viewed as an important factor contributing to large inter-individual variations in the degree of exercise performance impairment in hypoxia. Although the hypoxic ventilatory response (HVR) could provide insight into the underpinnings of such impairments, it is typically measured at rest under isocapnic conditions. Thus, we aimed to determine whether 1) HVR at rest and during exercise are similar and 2) exercise HVR is related to the degree of impairment in cycling time trial (TT) performance from normoxia to acute hypoxia (∆TT). Methods: Sixteen endurance-trained men (V˙O2peak, 62.5 ± 5.8 mL·kg-1·min-1) performed two poikilocapnic HVR tests: one during seated rest (HVRREST) and another during submaximal cycling (HVREX). On two separate visits, subjects (n = 12) performed a 10-km cycling TT while breathing either room air (FiO2 = 0.21) or hypoxic gas mixture (FiO2 = 0.16) in a randomized order. Results: HVREX was significantly (P < 0.001) greater than HVRREST (1.52 ± 0.47 and 0.22 ± 0.13 L·min-1·%SpO2-1, respectively), and these measures were not correlated (r = -0.16, P = 0.57). ∆TT was not correlated with HVRREST (P = 0.70) or HVREX (P = 0.54), but differences in ventilation and end-tidal CO2 between hypoxic and normoxic TT and the ventilatory equivalent for CO2 during normoxic TT explained ~85% of the variance in performance impairment in acute hypoxia (P < 0.01). Conclusion: We conclude that 1) HVR is not an appropriate measure to predict the exercise ventilatory response or performance impairments in acute hypoxia and 2) an adequate and metabolically matched increase in exercise ventilation, but not the gain in the ventilatory response to hypoxia, is essential for mitigating hypoxia-induced impairments in endurance cycling performance.