Objective To determine the incidence of hypo- and hyper-capnia in a European cohort of ventilated newborn infants.

Design and setting Two-point cross-sectional prospective study in 173 European neonatal intensive care units.

Patients and methods Patient characteristics, ventilator settings and measurements, and blood gas analyses were collected for endotracheally ventilated newborn infants on two separate dates.

Results A total of 1569 blood gas analyses were performed in 508 included patients with a mean±SD Pco₂ of 48±12 mm Hg or 6.4±1.6 kPa (range 17–104 mm Hg or 2.3–13.9 kPa). Hypocapnia (Pco₂<30 mm Hg or 4 kPa) and hypercapnia (Pco₂>52 mm Hg or 7 kPa) was present in, respectively, 69 (4%) and 492 (31%) of the blood gases. Hypocapnia was most common in the first 3 days of life (7.3%) and hypercapnia after the first week of life (42.6%). Pco₂ was significantly higher in preterm infants (49 mm Hg or 6.5 kPa) than term infants (43 mm Hg or 5.7 kPa) and significantly lower during pressure-limited ventilation (47 mm Hg or 6.3±1.6 kPa) compared with volume-targeted ventilation (51 mm Hg or 6.8±1.7 kPa) and high-frequency ventilation (50 mm Hg or 6.7±1.7 kPa).

Conclusions This study shows that hypocapnia is a relatively uncommon finding during neonatal ventilation. The higher incidence of hypercapnia may suggest that permissive hypercapnia has found its way into daily clinical practice.