Impulse oscillometry in the evaluation of diseases of the airways in children

Abstract

Objective: To provide an overview of impulse oscillometry and its application to the evaluation of children with diseases of the airways.

Data sources: Medline and PubMed search, limited to English language and human disease, with keywords forced oscillation, impulse oscillometry, and asthma.

Study selections: The opinions of the authors were used to select studies for inclusion in this review.

Results: Impulse oscillometry is a noninvasive and rapid technique requiring only passive cooperation by the patient. Pressure oscillations are applied at the mouth to measure pulmonary resistance and reactance. It is employed by health care professionals to help diagnose pediatric pulmonary diseases such asthma and cystic fibrosis; assess therapeutic responses; and measure airway resistance during provocation testing.

Conclusions: Impulse oscillometry provides a rapid, noninvasive measure of airway impedance. It may be easily employed in the diagnosis and management of diseases of the airways in children.

Figure 1

Components of the impulse oscillometry apparatus. A, A pressure signal generated in the loudspeaker reaching both the (terminal) resistor proximally and the pneumotachography more distally is transmitted into the airway through the mouthpiece. Pressure and flow signals from tidal breathing and pressure oscillations pass though the pneumotachograph and are measured by the transducer. B, Eight-year-old boy performing IOS. Patient is using a nose-clip, supporting the cheeks, and making a tight seal with the lips at the mouthpiece of the IOS apparatus. The results of IOS testing are graphically displayed on the computer monitor.

Figure 2

Representative graphical report of IOS testing. A and B, Composite plot developed by Goldman illustrates both resistance, R, and reactance, X, as a function of Freq (Hz) before bronchodilator (A) and postbronchodilator (B). AX is the area under the curve of reactance. C and D, The same curves displayed separately as pre and post R (C) and X (D).

Figure 3

Representative graphs of IOS and spirometry in patients with normal, obstructive, and restrictive lung disease. Tracings of lung resistance and reactance in comparison with spirometric flow-volume loop for prototypical patients with normal lung function, distal obstruction, proximal obstruction, and restrictive lung disease. Dotted lines indicate the normal tracing, whereas solid lines show pathological tracings.

Figure 4

Clinical scenarios highlight utility of IOS. A, Three-year-old boy with food allergy, eczema, and chest symptoms; unable to perform spirometry. IOS indicates significant reversible obstruction. B, Eight-year-old boy with allergic rhinoconjunctivitis, dyspnea, and wheezing on examination. Normal spirometry but abnormal findings consistent with clinical presentation shown from IOS. C, Sixteen-year-old male adolescent with recurrent pneumothoraces unable to perform spirometry. Impulse oscillometry performed without event, showing normal lung function.