Lung Function Testing

Get a clearer picture of how your lungs and breathing are working.

If you have a persistent cough, wheezing, shortness of breath, frequent chest infections, reduced exercise tolerance or other breathing concerns, talk to your GP about whether a referral to one of our Respiratory Specialists is appropriate.

👨‍⚕️ How does respiratory testing work?

You do not need to decide which test you need yourself. Your GP or another appropriate healthcare professional can refer you for specialist assessment.

Your Respiratory Specialist will then decide which investigations are most appropriate based on your symptoms, medical history and clinical needs.

The right test can provide valuable answers

Breathlessness, cough and wheezing can have many possible causes. Respiratory testing gives your specialist objective information about how your lungs, airways, breathing muscles and cardiovascular system respond.

You may need one test or a combination of tests. The aim is to provide useful information that helps your specialist understand your breathing and decide what should happen next.

Your respiratory testing journey

Which respiratory test might I have?

This is a general guide only. Your specialist will decide which investigations are appropriate for you.

🫁 Spirometry

A simple breathing test to measure how well air moves in and out of your lungs.

Spirometry measures how much air you can breathe out and how quickly you can do so. It is commonly used when assessing conditions such as asthma, COPD and other respiratory problems.

What happens?

• You wear a soft nose clip.
• You breathe through a mouthpiece connected to the testing equipment.
• You take a deep breath in.
• You blow out as hard and as fast as you can.
• The manoeuvre is repeated several times for reliable measurements.

📦 Lung volumes

Measure the total amount of air your lungs can hold.

Lung volume testing provides information about the size and capacity of your lungs and can add information that spirometry alone may not provide.

What happens?

• You sit inside a clear, enclosed testing booth.
• You wear a nose clip and breathe through a mouthpiece.
• You begin with relaxed breathing.
• You perform a series of guided breathing manoeuvres.
• Measurements may be repeated to ensure reliability.

🌬️ DLCO — Diffusing Capacity

Assess how effectively gases move from your lungs into your bloodstream.

DLCO testing assesses the gas-transfer function of your lungs. It provides information about how effectively gas passes across the lungs and into the bloodstream.

What happens?

• You wear a soft nose clip.
• You breathe through a mouthpiece.
• You take a deep breath containing a very small amount of test gas.
• You briefly hold your breath.
• You breathe out into the equipment for analysis.

🔬 FeNO — Fractional Exhaled Nitric Oxide

A quick, non-invasive test that provides information about airway inflammation.

FeNO measures nitric oxide in your exhaled breath. It can provide useful information about certain types of airway inflammation and may form part of an assessment for asthma alongside your symptoms and other investigations.

What happens?

• You use a handheld device with a mouthpiece.
• You take a deep breath in.
• You breathe out slowly and steadily through the device.
• The reading may be repeated if required.

✅ Quick    ✅ Painless    ✅ Non-invasive

💪 Static mouth pressures

Measure the strength of the muscles you use to breathe.

Your breathing depends on a coordinated group of muscles. Static mouth pressure testing measures the strength of the muscles involved in breathing in and out.

What happens?

• You breathe through a mouthpiece while wearing a nose clip.
• You breathe in or out forcefully against a resistance.
• Each effort lasts only a few seconds.
• The measurements are repeated for accuracy.

💨 Bronchodilator testing

See whether an inhaled bronchodilator changes your lung function.

This assessment compares your lung function before and after an inhaled bronchodilator and may form part of an assessment for asthma or airflow limitation.

What happens?

1. You complete your baseline breathing tests.
2. You may be given 4 puffs of Ventolin (salbutamol) through a spacer, according to the testing protocol.
3. You wait approximately 15 minutes.
4. The breathing tests are repeated.
5. The measurements are compared.

Medication note: Do not stop or change prescribed medication unless your clinician or testing team specifically instructs you to do so.

🩸 Arterial blood gas (ABG)

Measure oxygen and carbon dioxide levels in your arterial blood.

An ABG provides information about oxygenation, carbon dioxide and acid-base balance in the blood.

What happens?

• A small blood sample is taken from an artery, usually at the wrist.
• The sample is analysed promptly.
• Your specialist can use the result alongside your other clinical information.

🏃 Exercise assessment — Treadmill CPET

Understand how your heart, lungs and muscles work together during exercise.

A Cardiopulmonary Exercise Test (CPET) measures your body's response to exercise and can be useful when investigating breathlessness, assessing exercise capacity or supporting surgical assessment.

What happens?

• Heart monitoring sensors are placed on your chest.
• Oxygen levels are monitored.
• You breathe through a specialised mouthpiece.
• You begin walking slowly on a treadmill.
• The workload gradually increases.
• Your response is monitored throughout.

⏱ Typical exercise time: around 5–15 minutes, although this varies between individuals.

🚴 Exercise assessment — Bike CPET

A detailed exercise assessment using an exercise bike.

The bike-based CPET measures how your heart, lungs and muscles respond as exercise resistance gradually increases.

What happens?

• Heart monitoring sensors are attached.
• Oxygen levels are monitored.
• You breathe through a specialised mouthpiece.
• You begin pedalling comfortably.
• The resistance gradually increases.
• Your response is monitored throughout.

🚶 6-Minute Walk Test

A practical measure of functional exercise capacity.

The 6-Minute Walk Test measures how far you can walk in six minutes and how your body responds to this activity.

What happens?

• You walk along a marked course for six minutes.
• The goal is to walk as far as you comfortably can.
• Your oxygen levels and heart rate may be monitored.
• You can slow down or rest if necessary.

🌫️ Hypertonic saline challenge

Assess whether your airways are unusually sensitive.

This test examines how your airways respond to inhaled hypertonic saline and may provide useful information when your specialist is investigating airway sensitivity or possible asthma.

What happens?

• The test starts with baseline spirometry.
• You breathe in saline mist through a nebuliser.
• The inhalation periods gradually increase.
• Spirometry is repeated between stages.

🏃 Exercise-induced asthma challenge

Find out whether exercise may be triggering changes in your airways.

If coughing, wheezing, chest tightness or shortness of breath occurs during or after exercise, an exercise challenge may provide useful information about how your airways respond to activity.

What happens?

• You begin with a short warm-up.
• You exercise on a treadmill according to the testing protocol.
• Your heart rate and oxygen levels are monitored.
• Spirometry is repeated after exercise.

What does it feel like? You will become breathless as you exercise. This is expected because the test is assessing your response to physical activity.

✈️ Hypoxic challenge

Assess whether you may need additional oxygen when flying.

A hypoxic challenge simulates a lower-oxygen environment associated with commercial air travel. It may be requested when your specialist needs more information about your oxygen levels during a flight.

What happens?

• A baseline blood sample may be taken.
• You breathe a specially prepared gas mixture containing approximately 15% oxygen.
• Your oxygen levels and heart rate are monitored.
• The simulated exposure lasts approximately 15 minutes under the relevant testing protocol.
• A further blood sample may be taken when clinically required.

🔬 Induced sputum

Examine cells in airway mucus to provide additional information about airway inflammation.

Induced sputum testing involves breathing in hypertonic saline to help loosen mucus from the airways. If a suitable sample is produced, it can be analysed for inflammatory cells.

What happens?

1. You complete baseline respiratory testing.
2. You inhale hypertonic saline mist.
3. The saline helps loosen mucus.
4. You are asked to cough up a sputum sample.
5. The sample is processed for analysis.

🌬️ Airways Assessment

A more detailed assessment of airway sensitivity and inflammation.

An Airways Assessment combines respiratory testing with hypertonic saline to assess airway responsiveness and, where possible, obtain a sputum sample for laboratory analysis.

What happens?

• The assessment starts with spirometry.
• You inhale progressively increasing doses of hypertonic saline.
• Spirometry is repeated throughout the assessment.
• Any sputum produced is collected for analysis.
• Your lung function is monitored closely throughout.

Testing time: the assessment may take up to approximately 30 minutes, depending on the testing protocol and your response.

What can you expect?

Before your appointment

Preparation varies depending on the respiratory test you have been booked for.

Frequently asked questions

Do I need a referral?

Please speak with your GP or another appropriate healthcare professional about your symptoms and whether a referral to a Respiratory Specialist is appropriate.

Will I need every test on this page?

No. Your specialist will select the tests that are appropriate for your symptoms, medical history and clinical situation.

Are respiratory tests painful?

Most respiratory tests are non-invasive and painless. Some breathing tests can feel demanding for a few seconds, exercise tests deliberately make you breathe harder, and an arterial blood gas involves a small arterial blood sample.

What if I am nervous about the test?

Please tell our team. Your respiratory physiologist will explain what will happen and guide you throughout the assessment.

Can I take my usual medication?

Medication instructions differ depending on the investigation. Continue your medication unless your clinician or testing team has specifically instructed you otherwise.

How long will testing take?

There is no single time for all respiratory testing. Some investigations are very quick, while more complex assessments take longer. Your appointment information will advise you of the expected duration.

Ready to take the next step?

If you are experiencing ongoing respiratory symptoms, start by talking with your GP. A specialist assessment can help determine whether respiratory testing is appropriate for you.

Not sure whether you need to see a Respiratory Specialist?
Contact our team and we will be happy to answer your questions about referrals and respiratory testing.

CONTACT OUR TEAM CALL US

Questions about respiratory testing?

Complete the contact form below and our team will be happy to assist.

Please note: The information on this page is provided for general educational purposes and does not replace medical advice or an individual clinical assessment. Your Respiratory Specialist will determine which tests are appropriate for you.

Urgent symptoms: If you are experiencing severe or rapidly worsening difficulty breathing, severe chest pain, blue or grey lips, severe confusion or another medical emergency, seek urgent medical attention or call 111 in New Zealand.

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NZRSI's expert team will get back to you as soon as possible.