Author Archives: Jackie Aim

Occupational Asthma Testing

Peak flow diary and meter

Peak flow diary and meter

Diagnosis is based on :

  • Good history taking, to find any relationship to work exposure and symptoms. The history can be more useful in excluding Occupational asthma.
  • Any current medical problems.
  • Current medication.

Initial screening for Occupational asthma involves the use of Peak flow and peak flow diary recording over an extended period of time. For more information please see the Peak flow section on this website.

Peak flow diary may show dips in peak flow readings from morning to mid day when at work then again at night when at home. If your symptoms are reduced at weekends or when you have days off this should show on your peak flow diary.

Testing of occupational asthma is not routinely done in all hospitals and may require a referral to a specialist centre. This test involves the patient carrying out their usual work activity involving either chemicals, or fumes that provoke symptoms.

Occupational and work aggravated asthma

Baker

Timber worker

Chemicals

Spray painter

  • 1 in 6 people of working age who develop asthma have work related asthma.
  • This includes new onset asthma or a re-occurrence of pre existing disease.
  • This is the commonest occupational lung disease in westernised countries.
  • The incidence is dependent on the job environment and the hazards there is exposure to.
  • There may be clusters of people in some occupations who have asthma which can be due to their work environment.

Mannitol Challenge Test

Mannitol challenge test

Mannitol challenge test

For the mannitol challenge test:

  • You will have resting Spirometry measured before starting the challenge.
  • You will be asked to breathe in powder from an inhaler, and asked to hold your breath for 5 seconds before breathing out.
  • The Spirometry test will be repeated after 1 minute.
  • This is repeated with the amount of powder you breathe in being doubled each time. Spirometry is repeated after each increased dose to check how the airways are working.
  • Once the maximum dose has been given or there is a deterioration in your breathing, the test will be stopped.
  • If your breathing  is worse before the maximum dose has been reached, a nebuliser will be given to relieve any symptoms. You will be supervised by a physiologist during and after this test.

The Histamine/Methacholine Challenge Test

Female patient using a nebuliser

Nebuliser

During the Histamine/Methacoline test:

  • You will have resting Spirometry taken before starting the challenge test.
  • You will be asked to breathe in a small amount of the irritant for 2 minutes through a nebuliser.
  • You will have Spirometry repeated within 90 seconds after the nebuliser stops.
  • This is then repeated, gradually increasing the strength of histamine/methacoline to check how your airways react to this irritant.
  • This continues until maximum strength has been used or a reaction happens.

This test will show how reactive the airways are to irritant that may be causing your symptoms.

  • At this point, a nebuliser of reliever will be given to you to relieve any symptoms and relax your airways so that your breathing will return to normal resting levels.

You will be closely supervised by a physiologist during and after this test.

Histamine/Methacholine/Mannitol Challenge Test – Why is this test done?

Female patient breathing into a spirometry tube, wearing nose clips

This test is done to show how your lungs respond to irritation and exercise at the same time. You are carefully monitored during the test by a physiologist. It will help your respiratory specialists to plan the most effective treatment for you.

The challenge test involves breathing in an irritant that may cause the airways to go into spasm and narrow in controlled conditions.

The three different methods use different types of ingredients that can cause irritation:

  • Histamine/ Methacholine cause inflammation of the airways causing symptoms.
  • Mannitol has a drying effect on the airways also causing usual symptoms.

Exercise Spirometry

Treadmill and exercise cycle

Treadmill and exercise cycle

Some people will have Spirometry tested after a period of exercise.

  • This test involves either running or walking briskly on a treadmill or cycling on a static bicycle.
  • The tests begins with the person having Spirometry measurements taken after a period of inactivity.
  • The person then starts exercising, increasing intensity until maximum effort is reached, while the heart rate and breathing rate are monitored, for approximately 8 minutes.
  • The test then measures Spirometry which is repeated at 2 minute intervals for 15 minutes. This monitors any changes or deterioration in lung function. This demonstrates the degree of irritation in the airways which is caused by exercise.

Why measure lung volumes?

Whole body plethysmography

Whole body plethysmography

Whole Body Plethysmography:

  • This test involves being enclosed inside a glass chamber, where the volumes and pressure of the chamber are known.
  • Starting with normal breathing through a mouthpiece, the breathing rate is increased to a pant of more than 1 breath a second.
  • While panting continues, a shutter closes the mouthpiece for a few seconds.
  • This test measures the total amount of air in the thoracic area (rib cage) This being made up mostly of the lungs.

If you would like to see a video of what this test involves, visit the Association for Respiratory Technology and Physiology website.

Most common methods of measuring lung volumes

Nitrogen washout

Nitrogen washout

Nitrogen washout, breathing Oxygen:

  • This test involves normal breathing through a mouthpiece with 100% oxygen for a few minutes.
  • The amount of nitrogen which is in the air will always be the same as the nitrogen inside your lungs. As you breathe 100% oxygen, the nitrogen is flushed out of your lungs and measured as it is washed out by the oxygen.
  • Once nitrogen returns to your previous level the test is over.
  • This test measures the total lung capacity, all of the volume of the lungs.

 

 

Lung Volumes

Whole body plethysmography

Whole body plethysmography

This test measures the total size of the lungs including the areas inside the lung which cannot be emptied.
There are different ways of measuring lung volumes.

  • One breathing oxygen.
  • One involves being enclosed in a glass box where pressure changes in the lungs are measured.
  • One involves breathing Helium, this method is now less common.