Indicadores de carga física de trabajo en exposición intermitente crónica a gran altura / Indicators of physical work load in chronic intermittent exposure at high altitude

Se han establecido regulaciones para la exposición ocupacional a cargas físicas del trabajo, y a hipoxia intermitente crónica (HIC). También se ha indicado incorporar los riesgos asociados a HIC a un sistema de gestión de seguridad y salud en el trabajo. Dado que las cargas físicas de trabajo (CFT) en HIC pueden condicionar riesgos de trabajo pesado y fatiga física, se considera oportuno revisar el efecto de la CFT a gran altitud, entre 3000 y 5500 m de altura, sobre el riesgo de trabajo pesado, por lo cual se procede a recopilar estudios de campo de la capacidad aeróbica, mediciones de los signos que permiten evaluar el % de Carga Cardiovascular (%CCV) ocupado a gran altura. El %CCV se calcula mediante las frecuencias cardíacas (FC) de reposo, la máxima y la de trabajo. El monitoreo continuo de la FC y mediciones directas de la capacidad aeróbica máxima muestran que en HIC se modifican las tres FC de %CCV, también se muestra que cuando la FC de trabajo en altitud está por sobre 110 latidos/minuto hay mayor riesgo de fatiga y trabajo pesado. Adicionalmente se encontró que la capacidad aeróbica, VO2máx, medido a nivel del mar se reduce en trabajadores aclimatados a HIC con una reducción del 7% de la FC máxima. Este efecto, entendido como frenación fisiológica protectora, se puede perder durante una desaclimatación a nivel de mar por más de 10 días. En vista de una mayor probabilidad de trabajo pesado en HIC se proponen intervenciones para prevenir, controlar y mitigar riesgos de fatiga, cansancio y trabajo pesado que afecten la salud, conducta segura y productividad. En conclusión, en faenas a gran altitud, la CFT se puede evaluar mediante medición del %CCV basada en registros de la FC de reposo, máxima y de trabajo, en cada cota donde se ejecuta la actividad laboral, porque la hipoxia hipobárica modifica los tres componentes de esa ecuación.

Regulations have been established for the occupational exposition to physical loads from work, and chronic intermittent hypoxia (HIC). Also, it has been indicated to include the associated HIC risks to a security and health management system at work. Since physical workload (CFT) in HIC can condition risks of hard work and physical fatigue, it is considered appropriate to review the CFT effect at high altitude, between 3000 and 5500m of altitude, over the risks of hard work, which is why is proceeding to compile field studies about the aerobic capacity, measures of signs that allows assessing the % of Cardiovascular load (%CCV) used at great altitudes. The % CCV is estimated by cardiac frequencies (FC) at rest, maximum, and from work. The FC continuous monitoring and direct measures of the maximum aerobic capacity displays that the three FC of %CCV are modified in HIC is also displayed that when the work FC in altitude is over 110 heartbeats/minute there is major fatigue and hard work risk. Moreover, it was determined that aerobic capacity, VO2 max, measured at sea level is reduced in acclimated workers to HIC with a 7% reduction of maximum FC. This effect, known as physiological protective restrain, can be lost during a deacclimation at sea level for more than 10 days. At the sight of a greater probability of hard work in HIC, interventions are proposed to prevent, control, and reduce fatigue risks, tiredness, and hard work that affects health, safe-conduct, and productivity. In conclusion, in chores at high altitudes, CFT can be assessed by measuring the %CCV based on date from the FC in rest, maximum and from work, in each height where work activities are performed, because the hypobaric hypoxia modifies the three components of that equation.

Cortisol, resposta glicêmica e secreção de insulina em equinos clinicamente sadios submetidos a sessões de hipóxia normobárica / Serum cortisol, glycemic response and insulin secretion in healthy horses exposed to normobaric hypoxia sessions

Os níveis séricos de cortisol, resposta glicêmica e secreção de insulina foram avaliados em equinos não exercitados submetidos a sessões de hipóxia normobárica. Cavalos adultos sadios (n=8) foram selecionados após exame físico e submetidos ao teste de tolerância à glicose intravenosa (0,5g kg-1) (TTGIV). Amostras de sangue (n=11) foram coletadas entre 0 e 180 minutos após a administração de glicose para avaliar a resposta glicêmica e a secreção de insulina. Os animais foram então expostos a sessões de uma hora de hipóxia duas vezes ao dia, totalizando 43 sessões, com concentração decrescente de O2 de 17 a 12 por cento. A frequência cardíaca e as amostras sanguíneas para a determinação do cortisol sérico foram coletadas antes e a cada 15 minutos durante as sessões 1, 4, 6, 8, 10, 14, 22 e 43. A TTGIV foi repetida ao final do estudo. Os níveis de cortisol sérico foram maiores na sessão 1 (S1) (17 por cento O2) quando comparados aos níveis da S10 (13 por cento O2) e da S43 (12 por cento O2)(P<0,05). A curva glicêmica de equinos clinicamente sadios não submetidos a exercício não é alterada pela exposição a 43 sessões de hipóxia normobárica. O aumento na secreção de insulina, acompanhada de diminuição da frequência cardíaca e cortisol sérico sugerem uma adaptação dos cavalos ao modelo de hipóxia utilizado.

The cortisol levels, glycemic response and insulin secretion were evaluated in non-exercised horses submitted to sessions of normobaric hypoxia. Healthy adult horses (n=8) were selected after physical examination and underwent an intravenous glucose tolerance test (0.5g kg-1) (IVGTT). Blood samples (n=11) were collected between 0 and 180 minutes after glucose administration to evaluate glycemic response and insulin secretion. Then, they were exposed to 1-hour hypoxia sessions twice a day, reaching a total of 43 hypoxia sessions, with [O2] decreasing from 17 to 12 percent. Heart rate and serum samples to measure cortisol were collected before and every 15 minutes during the sessions 1, 4, 6, 8, 10, 14, 22 and 43. The IVGTT was repeated at the end of the study. The serum cortisol levels were higher in session 1 (S1) (17 percent O2) when compared to the levels of S10 (13 percent O2) and S43 (12 percent O2) (P<0.05). The glycemic curve in resting healthy horses is not altered by exposure to 43 normobaric hypoxia sessions. The increase in insulin secretion, followed by decreased heart rate and serum cortisol suggest an adaptation of the horses to the hypoxia model used.