In mechanical ventilation, what does consistent observation of increasing PECO2 signify in relation to alveolar ventilation?

Increasing partial pressure of end-tidal carbon dioxide (PECO2) consistently indicates that there is a decline in alveolar ventilation. This is because the partial pressure of carbon dioxide (CO2) in the exhaled air reflects the CO2 levels in the blood. When alveolar ventilation decreases, the removal of CO2 during exhalation is less effective, leading to higher levels of CO2 in the lungs and as a result, an increase in PECO2.

As alveolar ventilation declines, the body is unable to adequately exchange gases, resulting in CO2 retention, which is precisely what the monitored PECO2 levels would suggest. Therefore, consistent observation of increasing PECO2 is a critical indicator for clinicians, signaling the need for intervention to improve ventilation and optimize gas exchange, preventing further complications related to hypercapnia (excess CO2 in the bloodstream).