Final answer:
Pulmonary ventilation increases at higher altitudes, which can result in fatigue of the respiratory muscles during intense exercise. Hyperpnea occurs to meet increased oxygen demand, but is not the simple result of a drop in oxygen levels, as there's a complex interplay of neural factors. Acute mountain sickness can occur with exertion at high altitudes, but the body can acclimatize over time.
Step-by-step explanation:
Pulmonary ventilation is higher at altitude than at sea level for any work rate. During exercise at high exercise intensities, this could result in fatigue of the respiratory muscles (e.g., diaphragm). A lower partial pressure of oxygen at high altitudes means there is a smaller difference in partial pressures between the alveoli and the blood, resulting in less oxygen crossing the respiratory membrane (hypoxia).
However, tissues still receive sufficient oxygen at rest due to mechanisms like increased release of oxygen from hemoglobin and increased production of BPG by erythrocytes. When exercising at high altitudes, individuals can experience acute mountain sickness (AMS), but over time, the body can acclimatize, adjusting to the lower oxygen levels.
Hyperpnea, which is an increased depth and rate of ventilation to meet oxygen demand during exercise, is driven by mechanisms beyond just the drop in oxygen levels. There is a complex interplay of factors related to the nervous system and respiratory centers of the brain, including stimulation from motor neuron activation and proprioceptors. Contrary to hyperpnea, hyperventilation is when the breathing rate increases without an increase in cellular oxygen need, which can lead to abnormally low CO2 levels and high blood pH.
Therefore, the answer to the student's question is fatigue of the respiratory muscles, as the increased demand for ventilation at high altitudes can strain these muscles, potentially leading to their fatigue during high exercise intensities.