Chronic obstructive pulmonary disease (COPD) represents one of the leading causes of morbidity and mortality worldwide. According to the World Health Organization, an estimated 3 million deaths are attributable to COPD every year across the world. Tidal breathing analysis with Impulse Oscillometry (IOS) has demonstrated to be informative and differentiated in the early detection and follow up of pulmonary diseases like asthma, COPD and idiopathic pulmonary fibrosis. IOS is almost independent of patient cooperation and can test a larger patient range than spirometry alone, from children to adult to geriatric patients.
Detecting lung diseases with sound waves.
Hospital scientists are using sound waves to detect airway changes in patients with severe lung conditions.
Impulse oscillometry (IOS) was introduced at Birmingham's Queen Elizabeth Hospital to tackle problems associated with conditions like chronic obstructive pulmonary disease (COPD) and asthma.
Computer-aided IOS enables clinicians to detect subtle changes in a patients airway function earlier than when using conventional and more expensive techniques.
As the patient breathes through a pneumo-tachograph, a sound wave generated by a loudspeaker is superimposed over their breathing. The patients airflow and sound wave response is transmitted to the apparatus and used to calculate the various components of resistance to breathing.
Currently, this innovative technique has produced excellent results in clinical services both for patients who have received lung transplants and for those with severe airways disease.
The procedure's benefits include:
- Nothing more than quiet breathing is required from the patient - compared to other methods which can be invasive and unpleasant to the patient.
- Categorising the severity of a condition without the need for complex or expensive procedures requiring scans, invasive tests or radioisotope markers.
- Potential for developing the technique for use either in the GP surgery or even the patients home.
- Objective lung function measurements are routinely used to diagnose and manage asthma, but their utility for young children has not been defined.
In one American study, Bronchodilator responses were measured using impulse oscillometry (IOS) and compared with conventional spirometry to determine the value of lung function measures in 4-year-old asthma-prone children.
The study participants were in the Childhood Asthma Prevention Study (National Institute of Health/National Institute of Allergy and Infectious Diseases) and at risk for asthma. At age 4 years, concurrent asthma was determined by using a previously validated modified American Thoracic Society questionnaire. Children performed IOS and spirometry before and after albuterol administration and underwent skin prick testing to 13 common allergens to assess atopy.
IOS bronchodilator responses are remarkably abnormal in 4-year-old children, who are most likely to have persistent asthma. IOS is a useful diagnostic tool in early asthma development and might be a helpful objective outcome measure of early interventions. (J Allergy Clin Immunol 2003;112:317-22.)
Pulmonary Function Tests
(This functionality will vary with different devices)
Spirometry
- Single button activation, Independent selection of best inspiratory and expiratory maneuver, Partial flow/volume loops
Lung Volumes by Nitrogen Washout
- No nitrogen analyzer (no pumps, needle valves, oil changes, or noise), Automated leak detection, Lung clearance index, Washout pattern - "Shape Profile", interpretation (slow/fast emptying), Closing volumes (SBO2)
Diffusing Capacity, Single Breath
- Real-time gas measurement to ATS/ERS recommended standards, Adjustment of discard and sample volumes, Integrated airway pressure monitoring during breath-hold, Lung Volumes determination, Test more patients - Testing capability for patients with low lung volumes.
Diffusing Capacity, Intra-breath (NON-BREATH HOLDING)
- Alternative for dyspneic patient who can't hold their breath for 10 seconds, Exercise diffusion testing, Non-Invasive Cardiac Output (NICO) measurement*
Distribution
- Closing Volumes and Delta N2, Anatomical Dead Space
Plethysmography
- Thoracic Gas Volume, panting or quiet breathing, Airways Resistance, panting or quiet breathing, Display individual and composite tracing, Adjustable quiet-breathing compensation
Compression Free F/V Loops
- Easily differentiate upper airway obstruction from poor patient effort, Monitor compression volume shifts
Bronchial Challenge
- Complete user-defined protocols, Pre, Baseline plus 16 levels per protocol
Respiratory Mechanics Test
Inspiratory and Expiratory Pressures
- View pressures at various lung volumes, Trans-diaphragmatic pressures, Compliance, Work of breathing.
Impulse oscillometry in idiopathic pulmonary fibrosis
Idiopathic pulmonary fibrosis (IPF) is a condition where scar tissue (called fibrosis) builds up in the lungs. It usually gets worse over time. Fibrosis causes the lungs to become stiff and reduces the amount of oxygen that the lungs can take up. People with IPF complain of worsening breathlessness, which limits their day-to-day activities. Lung function tests are breathing tests that measure how well your lungs are working and are used by doctors to decide whether to start or stop medicines in people with IPF. However, people with IPF say that lung function tests require a lot of effort, can make them cough, and feel very short of breath. About 1 in 5 people with IPF are unable to perform lung function results accurately. This might lead to some people with IPF not receiving the right medications, or for their medications to be stopped too soon.
Impulse oscillometry (IOS) uses sound waves to measure the stiffness of the lung. The test is very quick (30 seconds), does not require any effort from the patient, and only requires a patient to breathe in their usual way. IOS has been used successfully in children who are unable to perform normal lung function tests. The new IOS tests are quicker and more comfortable to perform for patients than current lung function tests. Being able to assess the severity and outcomes accurately in more people with IPF will help the development of new medicines.
Conclusion
Impulse Oscillometry is an ideal complement to conventional lung function testing such as spirometry, body plethysmography and diffusion. It shows a comparatively high sensitivity in displaying peripheral obstructions of the respiratory tract (small airways) and detects instabilities in the bronchial system (trapped air), which supports early detection of lung disease.
Sources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5704804/
https://intl.vyaire.com/products/ios-impulse-oscillometry
https://fundingawards.nihr.ac.uk/award/NIHR300566
