Oxygen and carbon dioxide monitoring during sleep

Monitoring of oxygen and carbon dioxide (CO₂) is of crucial importance during sleep-disordered breathing in order to assess the consequences of respiratory events on gas exchange. Pulse oximetry (SpO₂) is a simple and cheap method that is used routinely for the recording of oxygen levels and the diagnosis of hypoxemia. CO₂ recording is necessary for the diagnosis of alveolar hypoventilation and can be performed by means of the end-tidal (PetCO₂) or transcutaneous CO₂ (PtcCO₂). However, the monitoring of CO₂ is not performed on a routine basis due to the lack of simple, cheap and reliable CO₂ monitors. This short review summarizes some technical aspects of gas exchange recording during sleep in children before discussing the different definitions of alveolar hypoventilation and the importance of CO₂ recording.