The stimulation of which of the following causes hyperventilation at high altitude

The composition of air stays the same, but the total barometric pressure falls with increasing altitude. Therefore, the PO2 also falls. At 3000 m (approximately 10,000 ft) above sea level, the alveolar PO2 is about 60 mm Hg and there is enough hypoxic stimulation of the peripheral chemoreceptors to definitely increase ventilation. As one ascends higher, the alveolar PO2 falls less rapidly and the alveolar PCO2 declines somewhat because of the hyperventilation. The resulting fall in aerial PCO2 produces respiratory alkaloids.Ref: Ganong review of medical physiology 23rd edition Page no: 617