1.2 Improvement of lung function
A retrospective study of pulmonary function in preterm infants found that preterm infants born at less than 32 weeks may have significantly reduced airflow during childhood and adolescence and that impairment of pulmonary function was partially associated with the degree of BPD29. Young people with very low birth weight with combined BPD have significantly reduced lung ventilation, as evidenced by a low expiratory volume on exertion and reduced expiratory volume/exertional lung volume in one second on exertion30.Caffeine improves lung function by increasing lung volume and airway compliance, decreases airway resistance, improves respiratory muscle strength, and helps wean premature infants from mechanical ventilation31. A clinical study on the effect of caffeine treatment on pulmonary function in preterm infants (birth weight <1500 g and gestational age <31 weeks) showed that early caffeine treatment significantly increased forced vital capacity(FVC) and forced expiratory volume(FEV) by five-fold in preterm infants without BPD, while this trend remained in preterm infants with BPD 32. Doyle et al.demonstrated a significant effect of caffeine on expiratory flow ;a group of patients who weighed less than 1250 g at birth, and did not receive early caffeine treatment ,had a lower of expiratory forced expired volume in 1 second (FEV1), FVC, and the forced expired flow from 25% to 75% of the FVC (FEF25-75%) at 11 years of age33. Another study found that caffeine treatment resulted in a sustained rapid increase in diaphragmatic activity and tidal volume (VT) in preterm infants and that caffeine did not always affect end-expiratory lung volume (EELV), respiratory rate, or inspiratory and expiratory times34.
Caffeine treatment has also been shown to improve lung function by increasing lung volume, total lung volume, and by improving lung elasticity and compliance in a rabbit model35. In a preliminary study, carried out in baboons, early caffeine treatment, combined with prophylactic surfactant treatment, was found to improve lung function over 24 hours by significantly reducing airway resistance and increasing lung compliance36.