What is the most sensitive indicator of hypoventilation?

The most sensitive indicator of hypoventilation is ETCO2 monitoring. This method measures the concentration of carbon dioxide in exhaled air and provides real-time feedback about a patient's respiratory function. When a person hypoventilates, carbon dioxide is not effectively eliminated from the body, leading to an increase in end-tidal carbon dioxide levels. This change occurs rapidly and reflects even slight deviations in ventilation much earlier than other parameters.

In contrast, clinical observation, while useful, relies on subjective assessment and may miss subtle signs of hypoventilation until they become pronounced. Pulse oximetry is valuable for assessing oxygen saturation but does not provide information about carbon dioxide levels. Respiratory rate can indicate ventilation status but is not reliably sensitive when it comes to detecting hypoventilation, as some patients may maintain an adequate respiratory rate while still becoming hypercapnic due to ineffective ventilation. Therefore, ETCO2 monitoring is the most effective and sensitive tool to identify hypoventilation promptly.