Capnography in spontaneously breathing preterm and term infants

To investigate sidestream EtCO2 wave patterns as related to prematurity.

The EtCO2 wave pattern was analyzed longitudinally in 20 sequential preterm, 32-37 weeks of gestation and 39 fullterm controls. Infants with a cardiorespiratory disease, neurological deficit or a metabolic disorder were not included in the study. Sidestream EtCO2 was employed. Wave patterns were identified and baseline expiratory/inspiratory length and wave amplitude were measured.

Two predominant (about 75%) wave patterns were identified: (i) (with plateau) significantly more prevalent among infants born at term as compared with preterm infants across their postconceptional ages (PCA) (P=0.005-0.04), (ii) (plateau free) significantly more prevalent among the youngest preterm infants as compared with the fullterm controls. Expiratory length was significantly correlated with respiratory rate (RR) across ages (P=0.01-0.001) whereas inspiratory length was correlated with RR among the two youngest groups of infants only (P=0.002 and 0.004). Wave patterns were not found to be affected by environmental temperatures, blood pressure, body weight, haemoglobin level, aminophylline or O2 supplementation.

These findings suggest that EtCO2 wave pattern distribution among preterm infants is distinctly different from that of term controls, regardless of PCA, while inspiration is related to the degree of maturity. Alveolar pathology could probably be missed by sidestream capnography.