Advances in infant and preschool lung function testing

Abstract

Background: Infant lung function tests are currently performed in more than 100 centres worldwide. Increasingly, centres in the AsiaPacific region are purchasing expensive and specialized equipment for this purpose. Equipment for testing preschool equipment is generally less expensive than equipment required for testing infants but assessing preschool children is tricky and requires investment in both time and human resources to get the right people for the job of working with such single-minded individuals. Pulmonary function testing in research: Infant and preschool lung function testing is being used in several research contexts. Recent studies that have used these tests have helped advance our knowledge on the early pathophysiology of diverse respiratory conditions such as cystic fibrosis, infant and preschool wheezing, childhood asthma, broncho-pulmonary dysplasia, as well as providing insights into aspects of lung growth and development. Pulmonary function testing in clinical practice: Infant and preschool lung function tests are also widely used (rightly or wrongly) for clinical evaluation. To be of benefit in clinical practice pulmonary function testing needs to be able to identify diminished lung function that may require a clinical response (this depends on good healthy control or reference data), to monitor disease status over time (depends on data on repeatability in both health and disease) and the response to therapeutic interventions (data on short-term repeatability required). Interpretation is currently limited in all these areas but general consensus is that the tests are on the cusp of being used routinely in clinical practice. Tests used in infants: The most popular tests in infants are those assessing forced expiratory flows and volumes (such as the raised volume and tidal rapid thoraco-abdominal compression techniques), plethysmography to measure functional residual capacity, and tests of ventilation inhomogeneity (such as the multiple breath inert gas washout). Limitations include the need for sedation, labour costs, lack of reference data and lack of longer-term repeatability data. Commercial equipment for each of these tests is, however, available. Tests used in preschool children: Popular tests in preschool children include those performed during tidal breathing such as the forced oscillation technique, resistance interrupter technique and multiple breath washout. Forced expiration using spirometry, with or without incentive, is also possible and widely used in preschool children. The technique of measuring the specific airways resistance is widely used in Europe and is in the process of undergoing standardization. Intervention studies and clinical trial networks: One outcome of lung function testing in infants and preschool children over the past few decades has been the insight gained into this crucial period of lung development where early insults to the developing lung architecture may have life-long effects in both chronic respiratory disorders and health. In the future, it is crucial that interventions are targeted early in life in order to prevent, rather than limit or reverse, the development of lung disease or maldevelopment of the lung. Infant and preschool lung function tests have been proposed as potential outcomes of such early intervention studies and have been used recently in this context. Multi-centre clinical trial networks are being developed for such studies that necessitate ongoing efforts to standardise the tests, develop quality assurance programs and facilitate better interchange of data between centres. Summary: Disappointingly, some of the limitations that have hindered interpretation of the results of infant (in particular), but also preschool, lung function tests over the past three decades are still to be overcome. However, advances in knowledge through research studies that have incorporated these tests, the commercial availability of several tests, the increasing number of centres gaining experience in their use and the recognition of the crucial role of early lung development in life-long lung health have served to highlight the importance of overcoming the limitations so that infant and preschool lung function tests can be used routinely in clinical practice.