['We hypothesised that short-term application of bi-level nasal continuous positive airway pressure CPAP (SiPAP) compared with conventional nasal CPAP (nCPAP) at the same mean airway pressure in infants with persistent oxygen need recovering from respiratory distress syndrome would improve CO2 removal with no change in oxygen requirement.', 'Non-blinded, randomised, observational four-period crossover study.', 'Level III NICU; low-birthweight infants requiring CPAP and oxygen while recovering from respiratory distress syndrome.', 'Infants requiring nasal CPAP for >24\u2005h prior to study enrolment, and fraction of inspired oxygen requirement (FiO2) of 0.25-0.5, were randomised to either nCPAP or SiPAP. A crossover design with four 1 h treatment periods was used such that each infant received both treatments twice. Oxygen saturations (SaO2), transcutaneous CO2 (tcCO2) and vital signs were monitored continuously. Polysomnographic recordings were analysed for apnoea, bradycardia and oxygen desaturation.', 'Twenty low-birthweight infants receiving 0.3±0.04% supplemental oxygen on CPAP of 6 cm H2O were studied at an average of 33\u2005days of age (±23\u2005days, SD). There were no differences in tcCO2 or other physiological parameters except mean blood pressure, which was lower during nCPAP (52.3±8.3 vs 54.4±9.1\u2005mm\u2005Hg; ±SD; p<0.01). No differences in short or prolonged apnoea, bradycardia or significant desaturation events were observed.'] Does bi-level CPAP improve gas exchange when compared with conventional CPAP for the treatment of neonates recovering from respiratory distress syndrome?