Transcutaneous CO₂ Monitoring in Extremely Low Birth Weight Premature Infants

Extremely low birth weight (ELBW) premature infants are particularly susceptible to hypocarbia and hypercarbia, which are associated with brain and lung morbidities. Transcutaneous CO₂ (TcCO₂) monitoring allows for continuous non-invasive CO₂ monitoring during invasive and non-invasive ventilation and is becoming more popular in the NICU. We aimed to evaluate the correlation and agreement between CO₂ levels measured by a TcCO₂ monitor and blood gas CO₂ (bgCO₂) among ELBW infants. This was a prospective observational multicenter study. All infants < 1000 g admitted to the participating NICUs during the study period were monitored by a TcCO₂ monitor, if available. For each bgCO₂ measured, a simultaneous TcCO₂ measurement was documented. In total, 1828 pairs of TcCO₂-bgCO₂ values of 94 infants were collected, with a median (IQR) gestational age of 26.4 (26.0, 28.3) weeks and birth weight of 800 (702, 900) g. A moderate correlation (Pearson: r = 0.64) and good agreement (bias (95% limits of agreement)):(2.9 [-11.8, 17.6] mmHg) were found between the TcCO₂ and bgCO₂ values in the 25-70 mmHg TcCO₂ range. The correlation between the TcCO₂ and bgCO₂ trends was moderate. CO₂ measurements by TcCO₂ are in good agreement (bias < 5 mmHg) with bgCO₂ among premature infants < 1000 g during the first week of life, regardless of day of life, ventilation mode (invasive/non-invasive), and sampling method (arterial/capillary/venous). However, wide limits of agreement and moderate correlation dictate the use of TcCO₂ as a complementary tool to blood gas sampling, to assess CO₂ levels and trends in individual patients.