Manferdelli, Giorgio, Benjamin J. Narang, Mathias Poussel, Damjan Osredkar, Grégoire P. Millet, and Tadej Debevec. Long-term effects of prematurity on resting ventilatory response to hypercapnia. High Alt Med Biol. 22:420-425, 2021. Background: This study investigated the resting ventilatory response to hypercapnia in prematurely born adults. Materials and Methods: Seventeen preterm and fourteen full-term adults were exposed to normoxic hypercapnia (two 5-minute periods at 3% and 6% carbon dioxide [CO ₂ ] interspersed by 5-minute in normoxia). Pulmonary ventilation ([Formula: see text]) and end-tidal partial pressure of CO ₂ (Petco ₂ ) were measured continuously. Results: No difference in lung function was observed between preterm and full-term adults. Petco ₂ was lower in preterm than in full-term adults (p < 0.05) during normoxia. During exposure to 3% CO ₂ , both [Formula: see text] and Petco ₂ increased in a similar way in preterm and full-term adults. However, at the end of the 6% CO ₂ period, there was a significantly higher [Formula: see text] in preterm compared with full-term adults (30.2 ± 7.5 vs. 23.7 ± 4.5 L/min, p < 0.0001), whereas no difference was observed for Petco ₂ (46.9 ± 2.1 vs. 50.6 ± 2.1 L/min, p = 0.99). Breath frequency was higher in preterm than in full-term adults (17.9 ± 4.0 vs. 12.8 ± 3.5 b/min, p < 0.01) during 6% CO ₂ exposure. Conclusions: Although data suggest that prematurity results in resting hypocapnia, the exact underlying mechanisms remain to be elucidated. Moreover, preterm adults seem to have increased chemosensitivity to hypercapnia.