The determination of oscillatory resistance (oscillatory airway resistance) is a diagnostic procedure in pulmonology (lung medicine), which can be used to determine airway resistance, among other things, for therapy control in bronchial asthma. Using the oscillatory method, resistance can be determined more easily and significantly less expensively than using a complex bodyplethysmograph (device for measuring respiratory physiological variables that are not directly accessible to direct measurement).
Indications (areas of application)
- Assessment of obstructive pulmonary diseases – determination of oscillatory resistance is indicated in mild to moderate obstructive pulmonary diseases. Diseases that are indications for the examination include bronchial asthma, chronic obstructive pulmonary disease (COPD), and emphysema (irreversible hyperinflation of the smallest air-filled structures (alveoli, alveoli) of the lungs). With the help of the procedure, an accurate determination can be made about the airway resistance and thus an assessment about the severity of the disease.
- Detection of positive bronchospasmolysis (drug-induced relaxation of the “cramped” bronchial smooth muscle) – The aim of detecting positive bronchospasmolysis by determining the oscillatory resistance is to check the extent to which the symptomatology of an obstructive disease can be influenced by medication. If the lung function values improve by at least 20% after taking a drug, this is referred to as a positive bronchospasmolysis test. While bronchial asthma often shows significant improvement with corticosteroid therapy, COPD typically shows little improvement. This test may only be performed in a stable and infection-free state to achieve a constant significance and to avoid endangering the patient.
- Progress monitoring under drug therapy – oscillatory resistance can be used to assess disease progression.
Contraindications
There are no contraindications when the indication for performing the procedure is present.
Before the examination
Before the examination, the physician or technical staff must explain to the patient how to perform the diagnostic method. Care should be taken to ensure that the pharynx (throat) is not constricted so that no erroneous measurement is taken. There should be a few minutes of resting breathing until the measurement is taken.
The procedure
Analogous to the classical methods for determining airway obstruction, the calculation of oscillatory resistance is also based on two physical parameters: pressure (alveolar pressure) and flow (respiratory flow). By measuring the two parameters, the resistance (Resistance) can be calculated. In the case of oscillatory resistance, a precisely defined alternating flow is generated by the measuring device, via which an oscillatory pressure is caused in the airways. The course of the oscillatory pressure and the alternating flow are measured in parallel. From this, the impedance (alternating current resistance), the phase shift and the resistance are calculated. It should be noted that the oscillatory resistance is directly dependent on the breathing position.
After the study
Following the examination, the evaluation is performed with comparison to the relevant standard values.
Possible complications
Because the procedure is a noninvasive measurement method, no complications are expected.
