The forced oscillation technique in clinical practice: methodology, recommendations and future developments. E. Oostveen, D. MacLeod, H. Lorino, R. Farre´ , Z. Hantos, K. Desager, F. Marchal, on behalf of the ERS Task Force on Respiratory Impedance Measurements. #ERS Journals Ltd 2003. ABSTRACT: The forced oscillation technique (FOT) is a noninvasivemethod with which to measure respiratory mechanics. FOT employs small-amplitude pressure oscillations superimposed on the normal breathing and therefore has the advantage over conventional lung function techniques that it does not require the performance of respiratory manoeuvres. The present European Respiratory Society Task Force Report describes the basic prin- ciple of the technique and gives guidelines for the application and interpretation of FOT as a routine lung function test in the clinical setting, for both adult and paediatric populations. FOT data, especially those measured at the lower frequencies, are sensitive to airway obstruction, but do not discriminate between obstructive and restrictive lung disorders. There is no consensus regarding the sensitivity of FOT for bronchodilation testing in adults. Values of respiratory resistance have proved sensitive to bronchodilation in children, although the reported cutoff levels remain to be cone rmed in future studies. Forced oscillation technique is a reliable method in the assessment of bronchial hyper- responsiveness in adults and children. Moreover, in contrast with spirometry where a deep inspiration is needed,forced oscillation techniquedoes not modifytheairway smooth muscle tone. Forced oscillation technique has been shown to be as sensitive as spirometry in detecting impairments of lung function due to smoking or exposure to occupational hazards. Together with the minimalrequirement for the subject 9s cooperation, this makes forced oscillation technique an ideal lung function test for epidemiological and e eld studies. Novel applications of forced oscillation technique in the clinical setting include the monitoring of respiratory mechanics during mechanical ventilation and sleep.

https://erj.ersjournals.com/content/erj/22/6/1026.full.pdf

The forced oscillation technique in clinical practice: methodology, recommendations and future developments

Nicole Beydon, Stephanie D. Davis, Enrico Lombardi, Julian L. Allen, Hubertus G. M. Arets, Paul Aurora, Hans Bisgaard, G. Michael Davis, Francine M. Ducharme, Howard Eigen, Monika Gappa, Claude Gaultier, Per M. Gustafsson, Graham L. Hall, Zoltán Hantos, Michael J. R. Healy, Marcus H. Jones, Bent Klug, Karin C. Lødrup Carlsen, Sheila A. McKenzie, François Marchal, Oscar H. Mayer, Peter J. F. M. Merkus, Mohy G. Morris, Ellie Oostveen, J. Jane Pillow, Paul C. Seddon, Michael Silverman, Peter D. Sly, Janet Stocks, Robert S. Tepper, Daphna Vilozni, and Nicola M. Wilson, on behalf of the American Thoracic Society/ European Respiratory Society Working Group on Infant and Young Children Pulmonary Function Testing

An official American Thoracic Society/European Respiratory Society statement: pulmonary function testing in preschool children.

In a prospective study of 124 infants enrolled as newborns, we assessed the relation between initial lung function and the subsequent incidence of lower respiratory tract illness during the first year of life. The risk of having a wheezing illness was 3.7 times higher (95 percent confidence interval, 0.9 to 15.5; P = 0.06) among infants whose values for total respiratory conductance (the reciprocal of the resistance to air flow of the entire respiratory system) were in the lowest third, as compared with infants with values in the upper two thirds of the range of values for the group. Boys with initial values in the lowest third for an indirect index of airway conductance had a 10-fold increase (95 percent confidence interval, 2.2 to 44.2; P = 0.001) in the risk of having a wheezing illness. A 16-fold increase (95 percent confidence interval, 1.7 to 147.1; P = 0.002) in the risk of having a wheezing illness was found among girls whose initial values for lung volume at the end of tidal expiration were in the lowest third. We conclude that diminished lung function is a predisposing factor for the development of a first wheezing illness in infants.

Diminished lung function as a predisposing factor for wheezing respiratory illness in infants.

Measurement of the effects of drugs, mediators and infectious agents on various models of lung disease, as well as assessment of lung function in the intact mouse has the potential for significantly advancing our knowledge of lung disease. However, the small size of the mouse presents significant challenges for the assessment of lung function. Because of compromises made between precision and noninvasiveness, data obtained may have an uncertain bearing on the mechanical response of the lung. Nevertheless, considerable recent progress has been made in developing valid and useful measures of mouse lung function. These advances, resulting in our current ability to measure sophisticated indices of lung function in laboratory animals, are likely to lead to important insights into the mechanisms of lung disease.

/pdf/measuring-the-lung-function-in-the-mouse-the-challenge-of-4apyonw89e.pdf

Measuring the lung function in the mouse: the challenge of size.

Conventional methods of lung function testing provide measurements obtained during specific respiratory actions of the subject In contrast, the forced oscillation technique (FOT) determines breathing mechanics by superimposing small external pressure signals on the spontaneous breathing of the subject FOT is indicated as a diagnostic method
to obtain reliable differentiated tidal breathing analysis Because FOT is performed without closure of a valve connected to the mouthpiece, and without maximal or forced respiratory manoeuvres, it is unlikely that FOT itself will alter airways smooth muscle tone
FOT utilises the external applied pressure signals and their resultant flows to determine lung mechanical parameters These pressure–flow relationships are largely distinct from the natural pattern of individual respiratory flows, so that measured FOT results are, for the most part, independent of the underlying respiratory pattern Therefore, oscillometry minimises demands on the patient and requires only passive cooperation of the subject: maintenance of an airtight seal of the lips around a mouthpiece and breathing normally
through the measuring system with a nose-clip occluding the nares Potential
applications of oscillometry include paediatric, adult and geriatric populations, comprising diagnostic clinical testing, monitoring of therapeutic regimens, and epidemiological evaluations, independent of severity of lung disease Oscillometry is also applicable to veterinary medicine
The last two main sections Relevance of oscillometry in clinical practice and
Oscillometry in the clinical pulmonary laboratory emphasise clinical aspects of
application and interpretation of FOT rather than methodological details and
technological solutions, which are discussed in the two sections that follow immediately below Clinical application of FOT does not require mastery of the mathematical infrastructure of the technical methodology, and readers interested in the clinical use of
FOT may find it more useful to begin with these clinical sections and refer subsequently to methodological and technological details

Forced oscillation technique and impulse oscillometry

The sections in this article are:


1
Modeling the Respiratory System as a Linear System
1.1
Models

1.2
Elemental Equations

1.3
Sinusoidal Forcing and Complex Impedance

1.4
Continuity and Compatibility Conditions

1.5
General Formulation of System Models

1.6
System Functions

1.7
Equivalent Circuits

1.8
Distributed-Parameter Models




2
History

3
Experimental Methods
3.1
Equipment

3.2
Inputs and Data Processing

3.3
Upper Airway Variability and Shunt




4
Frequency Responses Below 100 HZ
4.1
Total Respiratory System

4.2
Input Impedance Forcing at the Airway Opening

4.3
Transfer Impedance Forcing at the Chest

4.4
Transfer Impedance Forcing at the Mouth

4.5
Pressure and Flow Transfer Functions

4.6
Lung Impedance

4.7
Chest Wall Impedance

4.8
Airway Impedance




5
Frequency Responses Above 100 HZ
5.1
Wave Propagation in the Airways

5.2
Input Impedance Forcing at the Airway Opening

5.3
Pressure Transfer Functions

5.4
Airway Area by Acoustic Reflections




6
Clinical Applications
6.1
Pulmonary Function in Children

6.2
Obstructive Lung Diseases

6.3
Restrictive Lung Diseases

6.4
Miscellaneous Lung Diseases

Jeffrey J. Fredberg

Papers

Oscillation Mechanics of the Respiratory System