In an asthma or COPD patient, what is the expected progression of CO2 levels in a respiratory crisis?

In patients with asthma or COPD during a respiratory crisis, the expected progression of CO2 levels begins with respiratory alkalosis and can culminate in respiratory acidosis. Initially, when a patient experiences an acute exacerbation of asthma or COPD, they may hyperventilate due to a sensation of shortness of breath or fear. This hyperventilation leads to increased exhalation of carbon dioxide (CO2), resulting in lower levels of CO2 in the blood, causing respiratory alkalosis.

As the crisis progresses, the airway obstruction may worsen, reducing the ability to maintain effective ventilation, which can lead to hypoventilation. This diminished ventilation then causes CO2 levels to rise, leading to hypercapnia, which subsequently results in respiratory acidosis. Therefore, this progression from respiratory alkalosis due to hyperventilation to respiratory acidosis due to hypoventilation accurately reflects the typical changes in CO2 levels during an acute exacerbation in asthma or COPD.