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Amann M.,University of Utah | Goodall S.,Northumbria University | Twomey R.,University of Brighton | Subudhi A.W.,Altitude Co | And 3 more authors.
Journal of Applied Physiology | Year: 2013

Amann M, Goodall S, Twomey R, Subudhi AW, Lovering AT, Roach RC. AltitudeOmics: on the consequences of high-altitude acclimatization for the development of fatigue during locomotor exercise in humans. J Appl Physiol 115: 634-642, 2013. First published June 27, 2013; doi:10.1152/japplphysiol.00606. 2013.-The development of muscle fatigue is oxygen (O2)-delivery sensitive [arterial O2 content (CaO2) × limb blood flow (QL)]. Locomotor exercise in acute hypoxia (AH) is, compared with sea level (SL), associated with reduced CaO2 and exaggerated inspiratory muscle work (Winsp), which impairs QL, both of which exacerbate fatigue individually by compromising O2 delivery. Since chronic hypoxia (CH) normalizes CaO2 but exacerbates Winsp, we investigated the consequences of a 14-day exposure to high altitude on exercise-induced locomotor muscle fatigue. Eight subjects performed the identical constant-load cycling exercise (138 ± 14 W; 11 ± 1 min) at SL (partial pressure of inspired O2, 147.1 ± 0.5 Torr), in AH (73.8 ± 0.2 Torr), and in CH (75.7 ± 0.1 Torr). Peripheral fatigue was expressed as pre- to postexercise percent reduction in electrically evoked potentiated quadriceps twitch force ( ΔQtw,pot). Central fatigue was expressed as the exercise-induced percent decrease in voluntary muscle activation (ΔVA). Resting CaO2 at SL and CH was similar, but CaO2 in AH was lower compared with SL and CH (17.3 ± 0.5, 19.3 ± 0.7, 20.3 ± 1.3 ml O2/dl, respectively). Winsp during exercise increased with acclimatization (SL: 387 ± 36, AH: 503 ± 53, CH: 608 ± 67 cmH2O·s -1·min-1; P < 0.01). Exercise at SL did not induce central or peripheral fatigue. ΔQtw,pot was significant but similar in AH and CH (21 ± 2% and 19 ± 3%; P < 0.24). ΔVA was significant in both hypoxic conditions but smaller in CH vs. AH (4 ± 1% vs. 8 ± 2%; P < 0.05). In conclusion, acclimatization to severe altitude does not attenuate the substantial impact of hypoxia on the development of peripheral fatigue. In contrast, acclimatization attenuates, but does not eliminate, the exacerbation of central fatigue associated with exercise in severe AH. Copyright © 2013 the American Physiological Society.


Schwartz K.L.,Wayne State University | Bartoces M.,Wayne State University | Campbell-Voytal K.,Wayne State University | West P.,St John Hospital Family Medicine Residency Program | And 3 more authors.
Journal of the American Board of Family Medicine | Year: 2013

Objective: Assessing health literacy during the clinical encounter is difficult. Many established instruments are lengthy and not practical for use in a busy practice setting. Our objective was to compare the performance of 3 health literacy screening questions against the Short Test of Functional Health Literacy for Adults (S-TOFHLA) in an urban, ethnically diverse primary care practice-based research network. Methods: A convenience sample of patients in clinics in the Detroit area were recruited to complete a questionnaire that included the S-TOFHLA and 3 items similar to the Chew screening questions. Area under the receiver operating characteristic (AUROC) curves compared the test characteristics of the screening questions to the S-TOFHLA. Results: The participation rate was 92% (N = 599). Most participants were women (65%) and African American (51%); 51.8% had a household annual income of <$20,000. Almost all (96.7%) had an adequate score on the S-TOFHLA. The screening question with the largest AUROC (0.83; 95% CI, 0.70-0.95) was "How often do you have someone help you read instructions, pamphlets or other written materials from your doctor or pharmacy?"; the AUROC for all 3 questions was 0.90 (95% CI, 0.85- 0.95). Conclusions: Self-administration of the 3 screening questions demonstrated high performance compared with the 36-item S-TOFHLA interview instrument. These screening questions should help providers identify patients who may need extra support to follow health prescriptions.


Luks A.M.,University of Washington | McIntosh S.E.,University of Utah | Grissom C.K.,University of Utah | Auerbach P.S.,Stanford University | And 4 more authors.
Wilderness and Environmental Medicine | Year: 2014

To provide guidance to clinicians about best practices, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for prevention and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. These guidelines present the main prophylactic and therapeutic modalities for each disorder and provide recommendations about their role in disease management. Recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches to prevention and management of each disorder that incorporate these recommendations. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine 2010;21(2):146-155. © 2014 Wilderness Medical Society.


Davis C.,Aurora University | Hackett P.,Altitude Co
Emergency Medicine Clinics of North America | Year: 2017

High altitude illness encompasses a spectrum of clinical entities to include: acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. These illnesses occur as a result of a hypobaric hypoxic environment. Although a mild case of acute mountain sickness may be self-limited, high altitude cerebral edema and high altitude pulmonary edema represent critical emergencies that require timely intervention. This article reviews recent advances in the prevention and treatment of high altitude illness, including new pharmacologic strategies for prophylaxis and revised treatment guidelines. © 2017 Elsevier Inc.


Keyes L.E.,University of Colorado at Denver | Paterson R.,University of Colorado at Denver | Boatright D.,University of Colorado at Denver | Browne V.,University of Colorado at Denver | And 3 more authors.
Wilderness and Environmental Medicine | Year: 2013

Objective: Increased intracranial pressure (ICP) may contribute to acute mountain sickness (AMS). Measuring optic nerve sheath diameter (ONSD) by ultrasound (US) is a noninvasive technique to detect elevated ICP, and increased ONSD has been associated with AMS. We hypothesized that ONSD would increase with acute, rapid ascent to 4300 m and that increased ONSD would be associated with symptoms of AMS. We further hypothesized that treatment with oxygen at 4300 m would reduce symptoms and ONSD. Methods: A cohort study was performed comparing US measurement of ONSD in healthy subjects at 1400 m and 18 hours after rapid ascent to 4300 m, both before and after oxygen treatment and between subjects with and without AMS (Lake Louise Score ≥3). Results: Among 57 subjects, 29 (51%) experienced AMS after rapid ascent to 4300 m. In subjects without AMS, mean ONSD did not increase at 4300 m. In subjects with AMS, mean ONSD increased at 4300 m and was higher than in those without AMS. Treatment with oxygen lowered mean ONSD in subjects with AMS but not in those without AMS. Individual responses to altitude and oxygen varied greatly within groups, and the relationship between ONSD and AMS symptoms was weak. Conclusions: In this controlled study, mean ONSD increased in subjects with AMS at high altitude. However, individual variation was high, and most ONSD values were below the clinical threshold for raised ICP. Observed differences were small, of questionable clinical importance, and within the range of precision of the US machine. Overall, our data do not support a role for increased ICP in mild to moderate AMS. © 2013 Wilderness Medical Society.


Campbell A.D.,University of Utah | McIntosh S.E.,University of Utah | Nyberg A.,University of Utah | Powell A.P.,University of Utah | And 2 more authors.
Clinical Journal of Sport Medicine | Year: 2015

High-altitude athletes and adventurers face a number of environmental and medical risks. Clinicians often advise participants or guiding agencies before or during these experiences. Preparticipation evaluation (PPE) has the potential to reduce risk of high-altitude illnesses in athletes and adventurers. Specific conditions susceptible to high-altitude exacerbation also important to evaluate include cardiovascular and lung diseases. Recommendations by which to counsel individuals before participation in altitude sports and adventures are few and of limited focus. We reviewed the literature, collected expert opinion, and augmented principles of a traditional sport PPE to accommodate the high-altitude wilderness athlete/adventurer. We present our findings with specific recommendations on risk stratification during a PPE for the high-altitude athlete/adventurer. © 2015 Wolters Kluwer Health, Inc and Wilderness Medical Society.


Julian C.G.,Altitude Co | Subudhi A.W.,Altitude Co | Subudhi A.W.,University of Colorado at Colorado Springs | Wilson M.J.,Altitude Co | And 3 more authors.
Journal of Applied Physiology | Year: 2011

The pathophysiology of acute mountain sickness (AMS) is unknown. One hypothesis is that hypoxia induces biochemical changes that disrupt the blood-brain barrier (BBB) and, subsequently, lead to the development of cerebral edema and the defining symptoms of AMS. This study explores the relationship between AMS and biomarkers thought to protect against or contribute to BBB disruption. Twenty healthy volunteers participated in a series of hypobaric hypoxia trials distinguished by pretreatment with placebo, acetazolamide (250 mg), or dexamethasone (4 mg), administered using a randomized, doubleblind, placebo-controlled, crossover design. Each trial included peripheral blood sampling and AMS assessment before (-15 and 0 h) and during (0.5, 4, and 9 h) a 10-h hypoxic exposure (barometric pressure = 425 mmHg). Anti-inflammatory and/or anti-permeability [interleukin (IL)-1 receptor agonist (IL-1RA), heat shock protein (HSP)-70, and adrenomedullin], proinflammatory (IL-6, IL-8, IL-2, IL-1β, and substance P), angiogenic, or chemotactic biomarkers (macrophage inflammatory protein-1β, VEGF, TNF-α, monocyte chemotactic protein-1, and matrix metalloproteinase-9) were assessed. AMS-resistant subjects had higher IL-1RA (4 and 9 h and overall), HSP-70 (0 h and overall), and adrenomedullin (overall) compared with AMS-susceptible subjects. Acetazolamide raised IL-1RA and HSP-70 compared with placebo in AMS-susceptible subjects. Dexamethasone also increased HSP-70 and adrenomedullin in AMSsusceptible subjects. Macrophage inflammatory protein-1β was higher in AMS-susceptible than AMS-resistant subjects after 4 h of hypoxia; dexamethasone minimized this difference. Other biomarkers were unrelated to AMS. Resistance to AMS was accompanied by a marked anti-inflammatory and/or anti-permeability response that may have prevented downstream pathophysiological events leading to AMS. Conversely, AMS susceptibility does not appear to be related to an exaggerated inflammatory response. Copyright © 2011 the American Physiological Society.


Patent
Altitude Co | Date: 2015-05-15

A system and method for wirelessly monitoring and recognizing people and things is disclosed. An entity monitoring and recognition (EMAR) unit at a site detects the presence of the entity, and in response the unit recognizes the entity and triggers an action, wherein the detection and recognition comprises the EMAR unit wirelessly communicating with a device associated with the entity without any action on the part of the entity. A site is a physical location, including a budding. The system also stores detection and recognition events and associates them with the entity, the time of the detection and recognition, and a touchpoint within the site at which the detection and recognition occurred.


Olin J.T.,Altitude Co | Olin J.T.,Aurora University | Dimmen A.C.,Altitude Co | Subudhi A.W.,Altitude Co | And 2 more authors.
Respiratory Physiology and Neurobiology | Year: 2011

During exercise, as end-tidal carbon dioxide (PETCO2) drops after the respiratory compensation point (RCP), so does cerebral blood flow velocity (CBFv) and cerebral oxygenation. This low-flow, low-oxygenation state may limit work capacity. We hypothesized that by preventing the fall in PETCO2 at peak work capacity (Wmax) with a newly designed high-flow, low-resistance rebreathing circuit, we would improve CBFv, cerebral oxygenation, and Wmax. Ten cyclists performed two incremental exercise tests, one as control and one with PETCO2 constant (clamped) after the RCP. We analyzed , middle cerebral artery CBFv, cerebral oxygenation, and cardiopulmonary measures. At Wmax, when we clamped PETCO2 (39.7±5.2mmHg vs. 29.6±4.7mmHg, P<0.001), CBFv increased (92.6±15.9cm/s vs. 73.6±12.5cm/s, P<0.001). However, cerebral oxygenation was unchanged (ΔTSI -21.3±13.1% vs. -24.3±8.1%, P=0.33), and Wmax decreased (380.9±20.4W vs. 405.7±26.8W, P<0.001). At Wmax, clamping PETCO2 increases CBFv, but this does not appear to improve Wmax. © 2010 Elsevier B.V.


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