Modelo experimental de hipóxia normobárica intermitente em cavalos não treinados

Abstract

People living at high altitudes present compensatory adjustments to the hypoxic stimulation, such as physiological, morphological and functional adaptations. Humans have been submitted to intermittent hypoxic training (IHT) to achieve better athletic performance and to treat chronic diseases. The benefits related to IHT have been attributed to hematological, muscular, mitochondrial and plasmatic changes. An experimental model of altitude simulation was used on horses to assess the response of clinical, hematological and blood gas parameters to intermittent hypoxia. Seven horses were submitted to 30 one hour long hypoxia treatment sessions during 16 days (D1-D16). Heart (HR) and respiratory (RR) rates were measured on all sessions at time T0 (normoxia) and after 15, 30, 45 and 60 minutes of hypoxia. Blood samples for hematological evaluation were obtained on D0 (normoxia), D8 (O2 12%), D16 (O2 12%), while animals were in normoxia. Arterial blood gases were measured at T0 and after 30 and 60 minutes of hypoxia on D1 (O2 17%), D6 (O2 13%), D11 (O2 12%) and D16 (O2 12%). Bone marrow aspiration was performed to evaluate erythropoiesis on D0, D8, D16, D23 (post-trial normoxia) and D30 (post-trial normoxia). Untrained horses tolerated hypoxia at 17% O2. HR was lower at 14% O2 compared to 17% O2 (0, 15, 45 and 60 minutes) (p<0.001). PaO2 and SaO2 at 30 (P<0.05 and P<0.01) and 60 minutes (P<0.01 and P<0.001) decreased between 17% and 12% O2. PaCO2 increased at T0 (p<0.05) between 17% and 13% O2 and 17% and 12% O2. Myeloid:erythroid ratio decreased between D1 and D23, and RR and hematology values did not change during or along sessions. This experimental model successfully promoted cardio-circulatory adaptation in horses to hypoxia.