J. Stocks

Airway function at one year: association with premorbid airway function, wheezing, and maternal smoking

BACKGROUND Impaired growth and development of the respiratory system during fetal and early postnatal life may have important implications for lung development and later lung health. The aim of this study was to examine the association of diminished premorbid airway function, prior wheezing, and maternal smoking with airway function at 1 year of age. METHODS Respiratory function was measured at the end of the first year in 100 of 108 healthy term infants (93%) in whom similar measurements had been undertaken prior to any respiratory illness at 8 weeks. Physician diagnosed wheezing episodes were identified retrospectively from medical records. RESULTS At 1 year specific airway conductance during end expiration (sGawee; /s/kPa) was significantly diminished in those infants with prior wheezing (95% CI wheeze/no wheeze –0.76 to –0.14), mothers who smoked (95% CI smoke/no smoke –0.81 to –0.27), a family history of asthma (95% CI family history/no family history –0.62 to 0.00), or diminished premorbid sGawee (95% CI –0.13 to –0.43/s/kPa per unit reduction sGawee at 8 weeks). In a multivariate model only maternal smoking and diminished premorbid sGaweewere independently associated with diminished sGawee at 1 year. CONCLUSIONS Diminished airway function at the end of the first year appears to be mediated by impaired airway development during early life as well as by exposure to maternal smoking. These findings are consistent with the hypothesis that, at a population level, diminished premorbid airway function provides the link between wheezing lower respiratory illness and diminished airway function at 1 year. Maternal smoking remains an important and avoidable cause of impaired airway development and function in infancy.

A new microtransducer catheter for measuring esophageal pressure in infants

Measurement of esophageal pressure, as a reflection of pleural pressure, is essential for assessment of dynamic lung mechanics in neonates and infants. Conventionally, an esophageal balloon or a fluid‐filled catheter is used, but considerable skill is required to obtain accurate results. Both devices have problems, and failure to achieve valid occlusion tests have been reported, particularly in small infants with lung disease. Recently, a flexible #3 French gauge (FG) microtransducer catheter (MTC®, Dräger Netherlands) has become available for medical monitoring. We have assessed the accuracy and feasibility of using this device for measuring lung mechanics in 51 spontaneously breathing infants and small children aged 1 day to 24 months (weight 1.35 to 12.0 kg), 9 of whom were healthy neonates, the remainder suffering from a variety of cardio‐respiratory diseases, and in 18 sick ventilated infants (weight 0.6 to 4.0 kg). Positioning of the catheter was well tolerated by all infants. The ratio of esophageal to airway opening pressure changes (ΔPes:ΔPao) ranged from 0.94 to 1.09 [mean (SD) 1.013 (0.03)] for the spontaneously breathing infants and from 0.98 to 1.06 [mean (SD) 1.003 (0.02)] in the ventilated infants with no significant difference in this ratio between the two groups (p = 0.16). This new generation of catheter tip pressure transducers may provide a simpler and more reliable tool for assessing transpulmonary pressure changes in infants than has previously been available. Pediatr Pulmonol. 1996; 22:117–124.

Influence of jacket placement on respiratory compliance during raised lung volume measurements in infants

Summary. Recent introduction of the raised lung volume rapid thoraco‐abdominal compression (RVRTC) technique for measuring forced expiratory maneuvers in infants provides the potential opportunity to assess respiratory mechanics simultaneously by using multiple linear regression (MLR) of the relaxed breaths preceding jacket inflation to force expiration. This study was undertaken to investigate whether data obtained from raised lung volume are influenced by placement of the rapid thoraco‐abdominal compression (RTC) squeeze jacket. Paired measurements of tidal volume (VT) and respiratory rate (RR) during tidal breathing, and of inflation volume (Vinf), respiratory system compliance (Crs), and resistance (Rrs) during passive lung inflations were made in 60 (30 male) healthy term infants with and without a fastened, but uninflated RTC jacket in place.

Urinary antimony in infancy

OBJECTIVE To determine whether antimony may be detected in the urine during infancy and early childhood and its association with passive exposure to tobacco smoke, as assessed by urinary cotinine. DESIGN Analysis of spare aliquots of urine collected from infants participating in studies of respiratory function and passive smoking. Urinary antimony was assayed using inductively coupled plasma mass spectroscopy in 201 urine specimens collected at different ages throughout the first two years of life from 122 term and 26 preterm infants. Urinary cotinine was measured using gas liquid chromatography. MAIN OUTCOME MEASURE Urinary antimony concentrations. RESULTS Absolute antimony concentrations varied widely between infants, being below the laboratory detection limit of 0.02 μg/l in 7% of samples, below 0.5 μg/l in 90.5%, and above the reference value of 1 μg/l reported for non-occupationally exposed UK populations in 4%. Creatinine standardised antimony values were unrelated to postnatal age or urinary cotinine concentrations and were highest in urine collected from preterm infants within 24 hours of birth (geometric mean (95% confidence interval): 2.3 ng/mg (1.5 to 3.4)). CONCLUSION Although antimony is present at very low concentrations in urine during infancy and early childhood, the relevance to health is uncertain. The higher levels found in preterm infants may reflect prematurity or fetal assimilation of antimony. Tobacco is unlikely to be an important source of environmental exposure to antimony during infancy and early childhood.

Applications and Future Directions of Infant Pulmonary Function Testing

During the past 20 years there has been enormous progress in the field of infant lung function testing, with respect to the range of tests and equipment now available, their applications in research and clinical studies, and the degree of national and international collaboration. The major role for lung function testing in infants remains firmly within the research arena,where it has been extensively used to examine the early determinants of airway function and to investigate underlying pathophysiology and response to therapeutic interventions in a variety of respiratory diseases during early life. During recent years there has been increasing emphasis on developing techniques that can be used in unsedated infants and for those requiring ventilatory support. Future strategies need to encompass a multicenter, multidisciplinary, collaborative approach, with results from infant pulmonary function tests being integrated with those from other disciplines, including imaging, genetics, inflammation and immunology. The aims of this chapter are to (1) provide an overview of the extent to which infant lung function tests have been used in clinical and epidemiological research in the past, (2) describe some of the recently developed techniques that may have increasing application in future years and (3) consider potential future contributions of infant pulmonary function testing in the management of respiratory disease during infancy.