What is characterized by PCO2 levels less than 37 mmHg?

The condition characterized by PCO2 levels less than 37 mmHg is known as hypocapnia. PCO2, or the partial pressure of carbon dioxide, is a measure of the concentration of CO2 in the blood. Normal levels typically range from 35 to 45 mmHg, so when PCO2 levels drop below 37 mmHg, it indicates a lower-than-normal concentration of carbon dioxide in the bloodstream.

Hypocapnia often results from hyperventilation, which leads to excessive expulsion of CO2 from the lungs. This can occur in situations such as anxiety, panic attacks, or certain medical conditions. The decrease in CO2 can affect blood pH by causing respiratory alkalosis, which is a condition where the blood becomes more alkaline.

In contrast, hypercapnia refers to elevated levels of carbon dioxide, typically associated with respiratory failure or hypoventilation. Respiratory acidosis is defined by elevated PCO2 levels leading to increased acidity in the blood, while metabolic acidosis is related to a decrease in blood pH due to other metabolic factors not directly involving CO2 levels. Thus, the identification of hypocapnia as a state of reduced PCO2 is consistent with the physiological understanding of gas exchange and