The Mannitol Challenge test is used to identify airway hyperresponsiveness to assist in the diagnosis of asthma. Mannitol increases osmolarity in the airways which can cause the airways to constrict, especially in patients with asthma and exercise induced asthma.
The test involves performing a baseline spirometry measurement of the amount of air a patient can blow out. This involves having a nose peg on to block air flow from the nose while breathing through the mouth. You will be instructed to breathe normally through the mouthpiece, then to take a big breath in to fill your lungs, then blast it out hard and fast to empty.
Increasing cumulative doses of Mannitol are then inhaled through the dispenser and the spirometry measured after each dose. If the spirometry shows a significant decrease in the amount of air that can be blown out after any dose, then the test is stopped and a bronchodilator is given to reverse the effects of the Mannitol. Please advise staff if you cannot take Salbutamol.
What are the risks?
Mannitol is used to challenge the airways and measure any response under the close supervision of trained staff. It has the potential to cause bronchospasm. An acute bronchospasm can be managed with bronchodilator medications and oxygen which is available throughout the test. A doctor is available if there is a severe response.
The inhalation of the powdered Mannitol sugar can often trigger coughing. Unfortunately you will not be able to drink once the test has started and the technician will encourage you to persist with taking the cumulative doses of Mannitol to ensure the test is done in a timely manner to ensure accuracy.
Spirometry is generally a safe and non-invasive procedure. However it does require maximal effort, co-operation and some co-ordination. It is not unusual for spirometry to result in temporary breathlessness, oxygen desaturation, sensation of fainting, chest pain, cough and induced bronchospasm in patients with poorly controlled asthma. Spirometry can generate a high pressures in the chest which can be transmitted to vascular, abdominal and other body compartments, so there are circumstances when Mannitol testing should be delayed as listed below.
The minimum patient age for this test is 16 years. There are some other contraindications associated with a Spirometry test which the CRS team will discuss with you before your test.
What happens next?
Upon completion of the procedure, the test results will be formulated and sent to your referring doctor and any additional doctor specified by you. You will need to arrange a follow up appointment with your referring doctor to discuss the results.