Alterations in acid–base balance and high-intensity exercise performance after short-term and long-term exposure to acute normobaric hypoxic conditions

Abstract

This investigation assessed the course of renal compensation of hypoxia-induced respiratory alkalosis by elimination of bicarbonate ions and impairments in anaerobic exercise after different durations of hypoxic exposure. Study A: 16 participants underwent a resting 12-h exposure to normobaric hypoxia (3,000 m). Blood gas analysis was assessed hourly. While blood pH was significantly increased, po 2 , PCO 2 , and SaO 2 were decreased within the first hour of hypoxia, and changes remained consistent. A substantial reduction in [HCO 3 − ] levels was observed after 12 h of hypoxic exposure (− 1.35 ± 0.29 mmol/L, p ≤ 0.05). Study B: 24 participants performed in a randomized, cross-over trial portable tethered sprint running (PTSR) tests under normoxia and after either 1 h (n = 12) or 12 h (n = 12) of normobaric hypoxia (3,000 m). No differences occurred for PTSR-related performance parameters, but the reduction in blood lactate levels was greater after 12 h compared with 1 h (− 1.9 ± 2.2 vs 0.0 ± 2.3 mmol/L, p ≤ 0.05). These results indicate uncompensated respiratory alkalosis after 12 h of hypoxia and similar impairment of high-intensity exercise after 1 and 12 h of hypoxic exposure, despite a greater reduction in blood lactate responses after 12 h compared with 1 h of hypoxic exposure. Hypoxia has a profound influence on acid-base balance whenever unacclimatized people ascend to high altitudes. Barometric pressure decreases with increasing altitude and, therefore, oxygen pressure in the ambient and inspired air (P I O 2) falls 1. A reduced P I O 2 leads to a decrease in arterial oxygen partial pressure (PO 2) and to hypoxemia, which stimulates the peripheral chemoreceptors to evoke carbon dioxide (CO 2) washout 2-4. Concurrently, hyperventilation occurs as an hypoxic ventilatory response during acclimatization to high altitude, CO 2 partial pressure (PCO 2) falls, and arterial pH increases according to the Henderson-Hasselbalch equation 2, 5, 6. This respiratory alkalosis is subsequently compensated by increased renal elimination of bicarbonate ions (HCO 3 −), which results in a decrease in blood bicarbonate concentration [HCO 3 − ] and arterial pH returns to normal 2, 3, 5. Metabolic compensation of respiratory alkalosis occurs after 6 h of altitude exposure and is completed after 24 h at low to moderate altitude 2, 7. This compensation is further suggested to remain incomplete after 24 h of exposure to high altitude, but is then completed after several days 1, 2, 4, 7. In contrast, lowlanders show persistent alkalosis even after 9 weeks at 5,260 m 8. Nonetheless, to the best of our knowledge, information on values of pH and [HCO 3 − ] during the first 24 h of altitude exposure is still insufficient. [HCO 3 − ] is an essential blood buffer for metabolic acids. During maximal workloads with blood lactate levels up to 15 mmol/L, there is a corresponding decrease in plasma [HCO 3 − ] levels 9. Therefore, the resulting decline in [HCO 3 − ] and blood buffer capacity in the course of adaption to altitude might signific...

Alcalosis respiratoria, Revisión bibliográfica

“…Ahora bien, esto ocurre por la disminución de la presión de dióxido de carbono (PaCO2) en la sangre inferior a 35 mmHg. (Limmer et al, 2020;Sánchez-Díaz et al, 2017) De forma compensadora disminuirá la concentración de bicarbonato plasmático (HCO3 -) o sin ella, y por lo tanto hay una elevación del pH > 7.45 en el plasma sanguíneo, en consecuencia, a una hiperventilación alveolar. Cabe destacar que la alcalosis respiratoria se clasifica en agudo acompañado de un cuadro clínico característico de mareo, confusión, sincope, parestesias y espasmo muscular; mientras que la crónica tiende a ser asintomática.…”

“…En ciertos casos suele ser leve, sin embargo, requiere de tratamiento cuando el pH se encuentra por encima de 7,6 o la PCO2 está por debajo de 20mmHg, como también se debe considerar el tratamiento cuando el paciente presenta arritmias cardiacas, convulsiones, etc. (Limmer et al, 2020;Sánchez-Díaz et al, 2017)…”

Numero Completo

“…Ahora bien, esto ocurre por la disminución de la presión de dióxido de carbono (PaCO2) en la sangre inferior a 35 mmHg. (Limmer et al, 2020;Sánchez-Díaz et al, 2017) De forma compensadora disminuirá la concentración de bicarbonato plasmático tratamiento cuando el paciente presenta arritmias cardiacas, convulsiones, etc. (Limmer et al, 2020;Sánchez-Díaz et al, 2017)…”

“…(Limmer et al, 2020;Sánchez-Díaz et al, 2017) De forma compensadora disminuirá la concentración de bicarbonato plasmático tratamiento cuando el paciente presenta arritmias cardiacas, convulsiones, etc. (Limmer et al, 2020;Sánchez-Díaz et al, 2017)…”

Suplementação de bicarbonato de sódio e desempenho em exercício intermitentede alta intensidade: consistência dos efeitos e estratégias de otimização

“…O organismo desencadeia várias respostas ao tentar permanecer em homeostase, primeira reação que ocorre é a hiperventilação para aumentar a pressão parcial de O2 (PO2) (Gore et al 2007). Dentro da primeira hora em hipóxia há aumento do pH sanguíneo e queda da PO2, PCO2 e saturação de O2 (SaO2) (Limmer et al 2020), gerando uma alcalose ventilatória descompensada, que resulta em excreção de bicarbonato pelos rins (Gore et al 2007), somente após 12 horas há queda significativa do bicarbonato sanguíneo (Limmer et al 2020).…”