Jones MH, Howard J, Davis S, Kisling J, Tepper R. Am J Respir Crit Care Med. 2003;167:1283–1286
Purpose of the Study.
To demonstrate the ability of forced expiratory flow (FEF) volume curves from increased lung volumes to discriminate among infants with differing severities of respiratory symptoms and to compare the ability of variables used to quantify the flow volume curves to detect airway obstruction.
Infants referred to a pediatric pulmonary clinic were classified into 2 groups. Group 1 patients had previous respiratory symptoms but were asymptomatic on the date of evaluation. Group 2 patients were symptomatic with current respiratory symptoms, such as coughing, rhonchi, or wheezing on the date of evaluation. A control group included 155 healthy infants.
Before spirometry, infants received 50 to 75 mg/kg chloral hydrate orally; measurements were obtained while the infants were sleeping in the supine position. Forced expiratory maneuvers were performed with the increased-volume, rapid-thoracic compression technique. Flow volume curves were quantified with forced vital capacity (FVC), FEF at 50% of FVC, FEF at 75%, forced expiratory volume in 0.5 second (FEV0.5), and FEV0.5/FVC, which were expressed as z scores.
All variables except FVC had z scores that were significantly less than 0 and distinguished groups 1 and 2 with progressively lower z scores. The mean z scores for the flow variables (FEF at 50%, FEF at 75%, and FEF at 25–75%) were more negative than the z scores for the timed expired volumes (FEV0.5 and FEV0.5/FVC) for both groups. In general, measures of flow identified a greater number of infants with abnormal lung function than did measures of timed volume; FEF at 50% had the best performance in detecting abnormal lung function.
Forced expiratory maneuvers performed with the increased-volume, rapid-compression technique could discriminate among groups of infants with respiratory symptoms of differing severity. Measures of forced expiratory flow were better than timed expiratory volumes in detecting abnormal airway function.
Because routine, standardized, spirometric measurements among infants with respiratory diseases were not readily available in the past, several investigations used the increased-volume, rapid-thoracic compression technique to assess lung function in this age group. This study extends the body of evidence obtained with this technique and highlights the importance of forced expiratory flow measurements as being better than timed expiratory volumes in detecting abnormal airway function in this age group. The challenge remains to develop this technique into a more practical procedure that can be incorporated into routine clinical practice.