What would most likely occur after 24 hours of continuous hyperventilation in a normal subject?

After 24 hours of continuous hyperventilation, a normal subject would exhibit a significant decrease in arterial carbon dioxide levels (PaCO2) due to the excessive breathing rate. This reduction in CO2 leads to a process known as respiratory alkalosis, where the pH of the cerebrospinal fluid (CSF) becomes more alkaline, although it may not necessarily reflect in a normal pH reading if the alkalosis is pronounced.

In this context, it is essential to understand that hyperventilation increases the expulsion of CO2, which directly lowers PaCO2. The body requires some time to adjust, particularly concerning CSF pH levels. While hyperventilation is ongoing, normal physiological mechanisms are often insufficient to return the CSF pH back to baseline levels, but it will typically show a lower than normal PaCO2.

A further implication is that the cerebral blood flow may decrease as CO2 levels drop, leading to vasoconstriction of cerebral blood vessels due to decreased CO2 (a known vasodilator). However, in this scenario, the emphasis is on the relationship between CSF pH and PaCO2, where the low PaCO2 accompanies a CSF environment that may not yet fully equilibrate to compensate