Flow limitation in normal infants: a new method for forced expiratory maneuvers from raised lung volumes

Abstract

Forced expiratory maneuvers generated by rapid thoracic compression have been used to assess airway function in infants. It remains unclear whether flow limitation can be achieved in healthy infants because low pressure transmission across the chest wall and inspiratory effort may limit the maximum transpulmonary pressure developed during the maneuver. We have found that several rapid inflations to a lung volume set at an airway pressure of 30 cmH2O (V80) briefly inhibit respiratory effort and allow forced expiration to proceed from V80 to residual volume. We used a water-filled esophageal catheter to measure isovolume pressure-flow curves in seven healthy infants (3-88 mo). Forced vital capacity (FVC) was defined as the volume between V80 and residual volume. Pressure transmission between the compression jacket and the esophagus decreased with decreasing lung volume and averaged 60 and 37% at 50 and 75% of expired FVC, respectively. Subjects demonstrated plateaus in their isovolume pressure-flow curves at 50% of expired FVC and lower lung volumes. We conclude that this new methodology enables forced expiratory maneuvers to achieve flow limitation in healthy infants over at least the lower portion of their lung volume.

An Official American Thoracic Society Clinical Practice Guideline: Classification, Evaluation, and Management of Childhood Interstitial Lung Disease in Infancy

“…PFT. Using the raised-volume rapid thoracic compression (RVRTC) method, spirometry and plethysmographic lung volumes can be performed in sedated infants (52,53), including those requiring supplemental oxygen therapy. The technique is now performed at a large number of pediatric centers in the United States and Canada.…”

Infant lung function testing: available and useful methods

“…A pressure of 2.6-4.0 kPa (20-30 cmH 2 O) [1,[12][13][14] is then applied to the airway opening, elevating the infant's lung volume passively to near total lung capacity. When the positive pressure is removed, the infant exhales spontaneously, and this is repeated 4-5 times.…”

Assessment of exhaled nitric oxide kinetics in healthy infants

“…A modification of our previously described methodology for obtaining forced expiratory flows with the raised volume rapid thoracic compression technique was used (see Fig. 1A) (5,11). Infants breathed through a two-compartment face mask into a circuit that had an adjustable bias flow from a Sechrist infant ventilator (model IV-100B) connected to NO-free compressed air.…”

“…We describe an adaptation of our raised lung volume technique (5,11) to measure FE NO in normal infants. In addition, we report, for the first time, flow-independent NO diffusion parameters in healthy infants.…”