What ETCO2 value would you expect to see in the presence of hyperventilation?

In cases of hyperventilation, the body experiences a decrease in carbon dioxide levels due to excessive exhalation. This process leads to a reduction in the partial pressure of carbon dioxide in the bloodstream, which can be measured by the expired carbon dioxide (ETCO2) readings. Typically, normal ETCO2 values range from 35 to 45 mmHg, with 40 mmHg being the average.

When hyperventilation occurs, the body’s metabolic rate remains unchanged, but the increased respiration rate causes the removal of CO2 to outpace its production, resulting in lower ETCO2 values. Therefore, during hyperventilation, one would expect to see an ETCO2 value lower than the normal range.

A value of 30 mmHg reflects the expected decline in CO2 levels in hyperventilation, with lower readings indicating more significant degrees of hyperventilation. While the choice indicated as correct (35 mmHg) might seem plausible, it is on the higher end of the expected range for hyperventilating patients. The more accurate expectation for a hyperventilation situation typically reflects values closer to or below 30 mmHg, highlighting the respiratory alkalosis often seen in this condition.