ABSTRACT

This PhD dissertation is based on studies conducted during my employment at the Department of Pediatrics, Copenhagen University Hospital, Rigshospitalet. Respiratory diseases are a major cause of morbidity in infants; and lung function testing can provide information on the causes, pathophysiology and consequences of these diseases, as well as on effect of therapeutic intervention.

The aim of the thesis was to evaluate sensitivity, repeatability and feasibility of: measurements of tidal breathing, forced expirations by the raised volume rapid thoracic compression (RVRTC) technique, auscultation and measurements of transcutaneous oxygen ( P tc,O2 ) during a methacholine challenge test in infants.

These techniques reflect different aspects of lung function and pose considerably different resource requirements, including sedation.

P tc,O2 was the most sensitive parameter for detecting changes in lung function, followed by forced expiratory volume in 0.5 second (FEV 0,5 ) obtained by the RVRTC technique. Coefficients of variation for P tc,O2 : 4% and FEV 0.5 : 7%.

Feasibility was evaluated in terms of success rate, safety, acceptability and resource requirements. Baseline lung function was determined in 99% and 94%, and bronchial responsiveness in 87% and 88%, of the infants, by FEV 0.5 and P tc,O2 , respectively. No safety issues of concern were observed and the response of the parents was favourable. A complete test, carried out by one operator, took three hours.

In conclusion, P tc,O2 and FEV 0.5 are the most sensitive parameters for detecting changes in infant lung function. Baseline measurements of FEV 0.5 and measurements of bronchial responsiveness by P tc,O2 would improve feasibility of future studies on lung function in infancy. The requirement of sedation restricts their use to research and selected clinical cases.