Background: The surge in uptake of nasal continuous positive airway pressure (CPAP)\nfor respiratory support in preterm infants has occurred in the absence of an authentic\nanimal model. Such a model would allow investigation of research questions of\nphysiological and therapeutic importance. We therefore aimed to develop a preterm\nlamb model of the non-intubated very preterm infant on CPAP.\nMethods: After staged exteriorisation and instrumentation, preterm lambs were\ndelivered from anaesthetised ewes at 131 to 133 days gestation. Via a single nasal prong\n(4-mm internal diameter, 6- to 7-cm depth), positive pressure was delivered from the\noutset, with nasal intermittent positive pressure ventilation (NIPPV) used until transition\nto nasal CPAP was attempted, and periodically thereafter for hypoventilation. Caffeine\nand doxapram were used as respiratory stimulants. Gastric distension was prevented\nwith an oesophageal balloon. Cardiorespiratory parameters and results of arterial blood\ngas analyses were monitored throughout the study period, which continued for 150 min\nafter first transition to CPAP.\nResults: Ten preterm lambs were studied, at gestation 132 �± 1 days (mean �± SD)\nand birth weight 3.6 �± 0.45 kg. After stabilisation on NIPPV, transition to nasal CPAP\nwas first attempted at 28 �± 11 min. There was transient respiratory acidosis, with\ngradual resolution as spontaneous respiratory activity increased. In the final hour,\n79% �± 33% of time was spent on CPAP alone, with typical respiratory rates around\n60 breaths per minute. PaCO2 at end-experiment was 58 �± 36 mmHg.\nConclusions: Non-intubated preterm lambs can be effectively transitioned to nasal\nCPAP soon after birth. This animal model will be valuable for further research.
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