In this episode, we begin exploring how the body adapts to prolonged hypoxia. Key topics include renal compensation for respiratory alkalosis, increased ventilation, and early changes in red blood cell production. We highlight the role of erythropoietin (EPO) in stimulating new red blood cells, and how increased hemoglobin concentration improves oxygen transport. However, polycythemia (increased red blood cell count) also raises blood viscosity, increasing cardiovascular strain.