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Lung Function Testing

Spirometry

A diagnostic tool for the evaluation of lung disease, this test looks at how fast and how much air a patient is able to blow in the 1st second, and how much they can blow out in total.
 
  • Patient breathes into a mouthpiece with a nose peg blocking the nose, and has to breathe out and then inhale as fast as possible.
  • Test takes less than 30 seconds for each attempt and must be repeated at least three times.

If patient has completed peak flows, they will have an idea what to expect. 

 
Lung volumes

Measures all lung volumes (air that is breathed in and out, and how much is left in the lungs). Also looks at whether there is any resistance to airflow in the airways.
 
  • Patient sits in a glass cubicle with the door closed.
  • They breathe the air in the room on a mouthpiece with a nose peg on, keeping lips tightly sealed.
  • Test starts with normal breathing, then the patient ‘pants’ (shallow, controlled breathing) as well as taking a big breath in and exhaling fully.
  • Each test takes a minute and is repeated at least 3 times. 

DLCO (Diffusing capacity of the Lung for Carbon Monoxide) 

Looks at how well oxygen is dispersing from the lungs into the blood and the rest of the body (oxygen diffusion).
 
  • Patients inhale a small amount of carbon monoxide which is not harmful to the body.
IMPORTANT: Cannot be performed on patients who are pregnant or breastfeeding.
 

Tidal breathing 

Used to test for Hyperventilation Syndrome.
 
  • Patient breathes normally into a mouthpiece for 1.5 minutes with a nose peg on.
  • Patient breathes normally on a different mouthpiece for 3 minutes while oxygen and carbon dioxide levels are measured.

FeNo (Fractional Exhaled Nitric Oxide)

A non-invasive test that detects lung inflammation (such as asthma), and checks the potential efficacy of anti-inflammatory treatment. Also used to detect those who may not respond to treatment.

Patient holds a handle with a filtered mouthpiece attached and breathes in and out in a controlled manner.
Test takes 30 seconds and is sometimes repeated twice.
 

Static mouth pressures

Used to assess the strength of the respiratory and expiratory muscles.
 
  • Patient breathes room air through a mouthpiece with a nose peg on, breathing either in or out against a resistance.
  • Test takes 30 seconds and is repeated at least 3 times.

Bronchodilators

Examines whether Ventolin makes a difference to lung-function values and is performed after Spirometry and/or Lung Volume testing (see tabs above).
 
  • Patient performs pre-Ventolin testing then is given 4 puffs of Ventolin using a spacer. 
  • Patient waits 15 minutes then spirometry and lung volumes are measured again.

Arterial blood gas

Measures oxygen levels in the blood.
 
  • Doctor or physiologist takes a blood sample from artery in the wrist for processing in lab.

Exercise assessment – Treadmill

Used to determine the cause of shortness of breath, asses the lungs’ ability to cope with surgery or to measure an athlete’s performance.
 
  • Patient is set up with 10 sticky dots applied to the chest to monitor heart rate and rhythm.
  • An oximeter probe is attached to a finger to monitor heart rate and oxygen saturation.
  • A snorkel-like mouthpiece monitors breathing and measures oxygen and carbon dioxide levels.
  • Treadmill starts at slow speed on the flat. Every minute the speed or the gradient increases. 
  • The technologist notifies the patient in good time before this happens.
  • Patient is encouraged to walk for as long as possible.
  • Patients usually walk for between 5 and 15 minutes.
 
Exercise assessment - Bike 

Used to determine the cause of shortness of breath, asses the lungs’ ability to cope with surgery or to measure an athlete’s performance.
 
  • Patient is set up with 10 sticky dots applies to the chest to monitor heart rate and rhythm.
  • An oximeter probe is attached to a finger to monitor heart rate and oxygen saturation.
  • A snorkel-like mouthpiece monitors breathing and measures oxygen and carbon dioxide levels.
  • Patient cycles at a constant, comfortable speed. Every minute, the work load (watts) increases. The patient is to keep cycling at same speed.
  • Patient is encouraged to cycle for as long as possible.
  • Patients usually cycle for between 5 and 15 minutes.
 
6-minute walk test 

Used to assess the distance a patient can walk in 6 minutes. Measures the response to medical interventions in patients with moderate to severe heart or lung disease. Also provides an index of the patient’s ability to perform daily activities. 
 
  • Patient walks continuously for 6 minutes around a track in the corridor with the aim of covering as much distance as possible.
  • Physiologist will explain the route of the walk prior to the test.
  • Oxygen saturation and heart rate are measured throughout the test.
  • The first time it is conducted, the test is repeated twice with a 60-minute rest in between.

Methacholine challenge

Used to assess the level of non-specific bronchial hyper-responsiveness (asthma). Methacholine is a drug that has been shown to cause a reaction in the airways of people with asthma.
 
  • Patient inhales methacholine as a fine mist through a mouthpiece.
  • Baseline spirometry is performed at the start of the test.
  • Patient will perform Spirometry 30 seconds and 90 seconds after each dose to monitor their lung function.
  • Patient will breathe methacholine in increasing doses to assess whether it causes a change in their pulmonary function test results
  • There are six does including saline (salty water) which is the ‘control’ dose.
  • Patient will need to wait in the clinic for 15 minutes after the test is finished to ensure there is no delayed response to the Methacholine.
  • If lung function drops 20% or more, the test is stopped and Ventolin is given to reverse the effects of
IMPORTANT: Cannot be performed on patients who are pregnant or breastfeeding.
 

Hypertonic saline challenge

Used to assess the level of non-specific bronchial hyper-responsiveness (asthma).
 
  • Baseline spirometry is performed at the start of the test (see ‘Spirometry’ tab).
  • Patient will breathe in a fine mist of saline (salty water) via a nebulizer and a snorkel-like mouthpiece for different periods of time for each level.
  • Dose durations are: 1st level – 30 seconds; 2nd level – 1 minute; 3rd level – 2 minutes; 4th level – 4 minutes; 5th level – as required. Can be around 8 minutes.
  • Spirometry is performed 90 seconds after each dose to monitor patient’s lung function.
  • If lung function drops 15% or more, test is stopped and Ventolin is given to reverse the effects of saline.
 
Mannitol challenge (Aridol)

An innovative lung-function test used to diagnose and manage asthma by detecting active airway inflammation through measuring airway hyper-responsiveness. Aridol is a sugar-base powder.
 
  • Baseline spirometry is performed at the start of the test (see ‘Spirometry’ tab).
  • Patients inhale Aridol through a simple, hand-held device in increasing doses. There are 9 levels in all. 
  • Spirometry is performed 1 minute after each dose to monitor patient’s lung function.
  • Patient will need to wait at the clinic for 15 minutes after the test is finished to ensure there is no delayed response to the Mannitol.

Exercise-induced asthma challenge (EIA)

A test used to assess if there is any indication of exercise-induced hyper-responsiveness (asthma).
 
  • An oximeter probe is attached to a finger to monitor heart rate and oxygen saturation.
  • Patient warms up for 2 minutes, then starts running until there is shortness of breath and they want to stop. 
  • Breathing is monitored post the test by performing 5 spirometry tests (see Spirometry tab) over a 20-minute period. 
 
Hypoxic challenge

Used to assess a person’s fitness to fly and if supplemental oxygen would be required during the flight. If necessary, test can be performed whilst patient is on oxygen.
 
  • A baseline blood gas sample is taken by the doctor.
  • Patient breathes 15% oxygen-gas mixture for 15 minutes while sitting down. This emulates sitting on a plane breathing pressurised gas. 
  • A second blood gas sample may be required while the patient is breathing the 15% oxygen-gas mixture.
  • Oxygen saturation and heart rate are both monitored.
 
Induced sputum 

The gold standard for evaluating patients with asthma which requires a hypertonic saline challenge (see tab above), followed by the extraction of sputum and the immediate centrifuge and staining of cells for clinical assessment. This allows an accurate treatment to be determined.

 
Tuberculosis

Usually requested for immigration medicals.
 
  • Patient inhales nebulized hypertonic saline for a maximum of 30 minutes. Saline helps patients to cough out sputum. 
  • Sputum sample is collected into specimen pot and immediately sent to diagnostic laboratory.

IMPORTANT: Staff will be wearing protective gowns and masks during testing. Results, which can take up to six weeks and will be sent to the referring GP or specialist.

 
Airways Assessment
 
  • Baseline spirometry is performed at the start of the test (see ‘Spirometry’ tab).
  • Patient will breathe in a fine mist of saline (salty water) via a nebulizer and a snorkel-like mouthpiece for different periods of time for each level. 
  • Dose durations are: 1st level – 30 seconds; 2nd level – 1 minute; 3rd level – 2 minutes; 4th level – 4 minutes; 5th level – 4 minutes. 6th level – 4 minutes.
  • Patient inhales nebulized hypertonic saline for a maximum of 30 minutes. Saline helps patients to cough out sputum. 
  • Sputum ample is collected into specimen pot and immediately sent to diagnostic laboratory.
  • Spirometry is performed 1 minute after each dose to monitor patient’s lung function.
  • If lung function drops 10- 15% or more, test is stopped and Ventolin is given to reverse the effects of saline.

 
 

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referrals@nzrsi.health.nz

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