Background: The aim of the study was to evaluate the feasibility of lung function measurements by the raised volume rapid thoracoabdominal compression (RVRTC) technique during bronchial methacholine challenge in young infants.
Method: Four hundred two healthy infants were tested at 1 month of age with RVRTC during repeated methacholine challenges with quadrupling doses from 0.037 to 16.674 μmol.
Results: Measurement of baseline lung function was successful in 99% and the provocative dose (PD) was achieved in 79% of infants by forced expiratory volume in 0.5 s (FEV0.5). Additionally, the PD was successfully measured in 87% by transcutaneous oxygen pressure. No serious adverse events were observed during testing or after discharge from the clinic. The methacholine dose range was appropriate as PD could be determined in the majority of infants. FEV0.5 values in 21% of infants dropped > 40% during the test. Short-lasting, self-limiting episodes of hypoxemia of < 80% occurred in 1% of infants and bradycardia < 90 beats/min in 19% of infants. The most common observations by parents were changes in the patterns of sleeping (95%), eating (57%), and behavior (58%) of the infant after hospital discharge. The mean acceptability rating among parents was 8 on a scale from 1 to 10, with 13% rating ≤ 5. It took one operator 3 h to complete the test, with the actual lung function testing accounting for half the time.
Conclusion: This very comprehensive experience with standardized measurements of lung function by RVRTC during methacholine challenge in young infants in a single center leads us to conclude that the test is feasible and safe to perform in asymptomatic young infants.