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1. Low birth weight (LBW) is associated with an increased risk of cardiovascular disease. Preterm birth is a major determinant of LBW and has been shown to result in elevated arterial pressure (AP) in humans, but few studies have investigated the effects of preterm birth in the absence of potentially confounding factors. Our aim was to determine whether moderately preterm birth per se alters the postnatal development of AP in lambs. 2. Preterm lambs were delivered approximately 14 days before term (i.e. approximately 133 days of gestation); controls were born at term (approximately 147 days). Mean arterial pressure (MAP), heart rate (HR), blood composition and indices of growth were measured at 4 and 8 weeks post term-equivalent age (PTEA). We also studied a separate cohort of preterm and term sheep as young adults (approximately 1.1 years). 3. Preterm lambs had significantly lower birth weights than term lambs, but bodyweights were not significantly different by Day 12 PTEA. In addition, MAP, HR and most blood variables did not differ between term and preterm lambs at 4 or 8 weeks PTEA. Preterm birth per se did not alter MAP or HR in young adult sheep. 4. Low birth weight due to preterm birth does not result in an altered AP during early postnatal life or at maturity. Moderate intrauterine growth restriction (IUGR) due to twinning, which further reduces birth weight, does not affect MAP in preterm lambs. Other factors, such as the degree of prematurity or IUGR, exposure to corticosteroids or postnatal nutrition, may be important in the later development of elevated AP.

Background: Guidelines recommend neonatal resuscitation without controlling tidal volume or positive end-expiratory pressure (PEEP). However, these may improve gas exchange, lung volume and outcome., Aim: To investigate resuscitation of very premature lambs with a Laerdal bag without PEEP versus volume guarantee ventilation with PEEP., Methods: Anaesthetized lambs (n=20) delivered at 125 d gestation were randomized to three groups receiving 15 min resuscitation: (1) Laerdal bag and no PEEP; (2) ventilation with a tidal volume of 5 ml/kg and 8 cm H(2)O PEEP; (3) ventilation with 10 ml/kg and 8 cm H(2)O PEEP. They were then all ventilated for 2 h with tidal volumes of 5 or 10 ml/kg, and 8 cm H(2)O PEEP. Ventilation parameters and blood gases were recorded., Results: Different tidal volumes affected PaCO(2) within minutes, with 10 ml/kg causing severe hypocarbia. PEEP had little effect on PaCO(2). Oxygenation improved significantly with PEEP of 8 cm H(2)O, irrespective of tidal volume., Conclusion: Very premature lambs can be resuscitated effectively using volume-guarantee ventilation and PEEP. Tidal volumes affected PaCO(2) within minutes but had little effect on oxygenation. PEEP halved the oxygen requirement compared with no PEEP. Resuscitating premature babies with controlled tidal volumes and PEEP might improve their outcome.