11/13/24, 7\:34 PM Guide | Spirometry interpretation

Spirometry interpretation

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What is spirometry?

Spirometry is a method of assessing lung function by measuring the volume of air that the patient is able to expel from the
lungs after a maximal inspiration. It is a reliable method of di
obstructive pulmonary disease, asthma) and restrictive diseases (e.g.
Aside from being used to classify lung conditions into obstructive or restrictive patterns, it can also help to monitor disease
severity. This guide aims to provide a basic approach to spirometry interpretation.
Spirometry provides several important measures including\:
Forced expiratory volume in 1s (FEV1)\: the volume exhaled in the
similar to PEFR.
Forced vital capacity (FVC)\: the total volume of air that the patient can forcibly exhale in one breath.
FEV1/FVC\: the ratio of FEV1 to FVC expressed as a percentage.
Values of FEV1 and FVC are expressed as a percentage of the predicted normal for a person of the same sex, age and height.

Reference ranges

FEV1\: >80% predicted
FVC\: >80% predicted
FEV1/FVC ratio\: >0.7

Patient details

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Con
Name
Age
Gender
Height
Ethnicity
Age, gender, height and ethnicity are used to calculate predicted normal values for the patient.

Assess quality of results

Three consistent volume-time curves are required, of which the best two curves should be within 5% of each other.
The best of the three consistent readings of FEV1 and FVC should be used in your interpretation.
The expiratory volume-time graph should also be smooth and free from abnormalities caused by\:
Coughing during expiration
Extra breath during expiration
Slow start to forced expiration
Sub-maximal e

Obstructive spirometry pattern

Typical spirometry
Reduced FEV1 (\<80% of the predicted normal)
Reduced FVC (but to a lesser extent than FEV1)
FEV1/FVC ratio reduced (\<0.7)
Obstructive pattern - FEV1

Reversibility

It can be useful to assess reversibility with a bronchodilator if considering asthma as a cause of obstructive airway disease.
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Patients should be asked to stop bronchodilator therapy prior to spirometry, to ensure previous treatments do not a
results (if the patient has severe disease, this would not be advisable)\:
Short-acting beta-2-agonists should be stopped 6 hours prior to testing.
Long-acting beta-2-agonists should be stopped 12 hours prior to testing.
To assess reversibility, administer 400 micrograms of salbutamol and repeat spirometry after 15 minutes\:
The presence of reversibility is suggestive of a diagnosis of asthma.
The absence of reversibility suggests
(COPD).
Partial reversibility may suggest a coexisting diagnosis of asthma and another obstructive airway disease (e.g. COPD).

Aetiology of obstructive lung disease

Causes of obstructive lung disease include\:
COPD
Asthma
Emphysema
Bronchiectasis
Cystic

Restrictive spirometry pattern

Typical spirometry
Reduced FEV1 (\<80% of the predicted normal)
Reduced FVC (\<80% of the predicted normal)
FEV1/FVC ratio normal (>0.7)
Restrictive pattern - FEV1

Aetiology of restrictive lung disease

Causes of restrictive lung disease can be pulmonary or non-pulmonary in origin.
Pulmonary causes
Pulmonary causes of restrictive lung disease include\:
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Pulmonary
Pneumoconiosis
Pulmonary oedema
Lobectomy/pneumonectomy
Parenchymal lung tumours
Non-pulmonary causes
Non-pulmonary causes of restrictive lung disease include\:
Skeletal abnormalities (e.g. kyphoscoliosis)
Neuromuscular diseases (e.g. motor neuron disease, myasthenia gravis, Guillan-Barre syndrome)
Connective tissue diseases
Obesity or pregnancy

References

1. Spirometry in Practice\: A Practical Guide to Using Spirometry in Primary Care 2nd Ed (2005). British Thoracic Society COPD
Consortium. Available from\: [LINK].
2. Dr Colin Tidy. Spirometry. Patient.info. Published 2nd Dec 2016. Accessed on 12th Dec 2017. Available from\: [LINK].
Source\: geekymedics.com
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