Lung Function Testing

Highly experienced scientists administering breathing tests:

Complex lung function testing includes a suite of essential tests for the diagnosis and management of a broad range of respiratory conditions. Your values are compared to age, height and sex adjusted reference populations to determine whether your lungs are functioning normally or not. Tests are often repeated over time to track your progress. Spirometry, lung volumes and gas diffusion are commonly performed as part of an initial consultation.

Spirometry is the cornerstone test of lung function. During the test, you will inhale as much as possible to fill your lungs, before forcefully breathing out. The spirometer measures the volume of air expired and how quickly this occurs. It is vital to the diagnosis of both asthma and chronic obstructive pulmonary disease (COPD), as well as many other lung conditions. Spirometry is often performed serially as part of follow up to check progress over time.

Lung volumes are a measurement of the amount of air in the lungs at various stages of the breathing cycle; from gentle breathing to full inspiration and expiration. The test requires you to sit inside a comfortable, specially calibrated see-through chamber (known as the “body box”). Sensors detect changes in pressure within the lungs and within the box, which in turn deliver measurements of lung capacity.

Gas diffusion (or diffusing capacity) is a test of the ability of the lungs to transfer gas from lung alveoli to the bloodstream. You will be asked to inhale a harmless gas mixture and hold your breath for approximately 10 seconds. A computer sensor then calculates the amount of gas mixture that has been transferred. A simple finger prick blood test is often performed as part of the analysis.

This test records distance walked and oxygen saturations over a six minute walk on a flat, straight track. It is commonly used to track progress in certain lung diseases and to assess whether home oxygen may be beneficial.

Maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) measure respiratory muscle strength. You will be asked to inhale and blow out forcefully. These tests are used in the evaluation of disorders affecting the nervous system, diaphragm and lung muscles.

Bronchoprovocation is a test performed to diagnose asthma, particularly when standard tests are inconclusive. You will inhale mannitol (a natural sugar) which may provoke a response in the lungs that mimics asthma, which can be measured spirometrically. Bronchoprovocation is sometimes performed as a medical screening test for occupational reasons, or recreational pursuits (eg. diving).

Fractional exhaled nitric oxide (FeNO) measures the amount of nitric oxide in your breath. Nitric oxide is a marker of lung inflammation, and provides useful information regarding asthma control. It is a simple, quick test requiring gentle expiration into a handheld device. It is often used serially in asthma to ensure optimum treatment.

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