Nocturnal end-tidal PCO2 to detect apnoeas and hypopnoeas in sleep-disordered breathing

In this study, the end-tidal PCO2 (PETCO2) during the night was measured. The PETCO2 signal was obtained by introducing a cannula through the nose into the nasopharyngeal cavity. The usefulness of this method to identify nocturnal hypoventilation was studied in 29 patients with chronic obstructive pulmonary disease (COPD) with and without oxygen supplementation. The results showed that 27 patients with COPD developed 67 nocturnal oxygen desaturations which were all accompanied by raised PETCO2. During oxygen therapy in all COPD patients nocturnal episodes with increased PETCO2 occurred. Furthermore, the detection of nocturnal apnoeas and hypopnoeas was assessed in 19 subjects who were referred to the sleep laboratory for snoring and daytime sleepiness. In this group episodes of disordered breathing could easily be assessed. The PETCO2 signal was especially useful to identify hypopnoeas that were accompanied by only small dips in SaO2 (< 3%). It is concluded that PETCO2 measurement is useful in the detection of hypoventilation during sleep in COPD patients, especially when they receive supplemental oxygen. PETCO2 recording detects obstructive apnoeas and hypopnoeas and is especially helpful to identify hypopnoeas which are accompanied by only small dips in oxygen saturation.