Aims-To assess the eVects of smoking during pregnancy on lung mechanics and lung volumes in the immediate neonatal period, before infants are exposed to passive smoking. Methods-Lung function tests were carried out within 72 hours of delivery in infants born to 100 non-smoking and 189 smoking mothers. Lung growth was assessed by plethysmography and lung mechanics using the single breath occlusion technique and oesophageal balloon/ pneumotachography.Antenatal maternal serum cotinine values were obtained from 133 mothers. Results-Smoking was associated with a significant reduction in birthweight (mean 256 g, 95% CI 0.164 to 0.392), and length (mean 1.26 cm, 95% CI 0.48 to 2.00). Lung volume was not reduced when related to weight. Smoking was associated with a highly significant reduction in static compliance (C rs) . This eVect remained significant after relating C rs to weight and lung volume. Regression analyses showed that the C rs association was limited to the boys. Smoking was associated with a small but significant reduction in respiratory system conductance (G rs ) (single breath occlusion technique) and total pulmonary conductance (G p ). These associations were limited to girls. Conclusions-Smoking in pregnancy reduces static compliance in boys and conductance in girls. There was no evidence that maternal smoking adversely aVected fetal lung growth. (Arch Dis Child Fetal Neonatal Ed 1999;80:F8-F14)

Natamycin, a fungicide marketed as Tymasil, is claimed to reduce house dust mite numbers and would therefore be expected to improve asthma in children with mite sensitivity. We have tested this assertion by a double-blind, placebo-controlled trial. There was no significant effect on levels of Der p I in mattress dust between active and placebo groups at the end of the spraying period. Histamine inhalation challenge PC20, clinic visit symptom scores and lung function tests reflecting either large or small airways obstruction were also unchanged. Therefore this product is not a therapeutic option for mite-allergic patients using the manufacturer's recommended dose and method of administration. Other factors influencing the Der p I levels were also investigated. Of these, only month of measurement and bedroom wall humidity showed any association.

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The effect of the instrumental dead space on breathing pattern and the values of pulmonary mechanics was evaluated because of concern about the relatively large dead space of 26 mL in a commercially available system. Sixty-three healthy newborn infants were studied with a system as commercially supplied, and with the dead space eliminated using a 2 L/min biased flow. This led to a significant reduction in mean (+/- SD) values of respiratory rate from 56.8 (+/- 11.7) to 48.2 (+/- 11.7) breath/min (P < 0.0001), tidal volume from 5.2 (+/- 1.3) to 4.9 (+/- 0.9) mL/kg (P < 0.05), minute volume from 284 (+/- 68) to 220 (+/- 63) mL/min/kg (P < 0.0001), and work of breathing from 13.7 (+/- 6.6) to 11.8 (+/- 7.6) g.cm/kg (P < 0.02). There was a significant increase in dynamic lung compliance from 5.2 (+/- 1.5) to 5.6 (+/- 1.2) mL/cm H2O (P < 0.01) but no difference for total pulmonary resistance 39.6 (+/- 22.8) and 38.8 (+/- 22.2) cm H2O/L/sec. This shows that the instrumental dead space prevents measurement of the basal breathing patterns and alters the values of pulmonary mechanics. It is, therefore, important to use equipment with low dead space or make efforts to remove it by using a biased flow system such as we describe when measuring breathing patterns and pulmonary mechanics in the newborn.