Spirometry

Recommendations for Spirometry

Asthma

Indications for Spirometry:

1. Suspected Asthma:
   • Any patient with suspected asthma should undergo spirometry.
2. Making the Diagnosis:
   • Combine spirometric criteria with clinical findings to diagnose asthma.
   • Diagnosis cannot be made solely based on spirometry findings.
3. Confirming Past Diagnosis:
   • Use spirometry to confirm a previous diagnosis of asthma.
4. Assessing Risk of Flare-Ups:
   • Evaluate risk of asthma flare-ups using spirometry.
5. Investigating Recent Worsening:
   • Use spirometry to investigate recent worsening of asthma control.
6. Monitoring Treatment Response:
   • Assess response to changes in treatment.
7. Periodic Review:
   • Periodically review asthma control (e.g., every 1–2 years).
8. Severe Asthma or Poor Perception of Airflow Limitation:
   • Perform spirometry at every visit for patients with severe asthma or those with poor perception of airflow limitation (e.g., those who do not feel different with a 15% change in FEV1).

COPD

Indications for Spirometry:

1. Investigation of Symptoms:
   • Unexplained breathlessness.
   • Chronic cough (daily for 2 months).
   • Intermittent or unusual cough.
   • Frequent or unusual sputum production.
   • Relapsing acute infective bronchitis.
2. Case-Finding:
   • In individuals exposed to tobacco smoke or occupational dusts and chemicals.
   • In patients with a strong family history of COPD.
3. Making the Diagnosis:
   • Confirm diagnosis of COPD with spirometry.
4. Reviewing Treatment and Disease Progression:
   • Monitor treatment response and disease progression in individuals with COPD

Abbreviation	Name	Definition	Notes
FVC (litres)	Forced vital capacity	The maximum volume of air that can be expired during a single expiratory manoeuvre using maximal effort initiated following a full inspiration	Indicates lung capacity FVC compared with LLN is used to identify potential restriction
FEV1 (litres)	Forced expiratory volume in 1 second	The volume of air forcefully expired from full lungs during the first second of an expiratory manoeuvre	Indicates how quickly full lungs can be emptied, reflecting airway calibre. FEV1% predicted is used to assess severity of expiratory airflow obstruction.
FEV1/FVC (ratio)	Ratio of forced expiratory volume in 1 second to forced vital capacity	FEV1 expressed as a fraction or percentage of FVC	Indicates whether expiratory airflow obstruction is present FEV1/FVC ratio is used to identify expiratory airflow obstruction.
PEF (litres/second or litres/minute)	Peak expiratory flow	The maximal expiratoryflow achieved during themanoeuvre	Used for assessing effort

Choice of Reference Values for Spirometry

Recommended Reference Dataset:

• The Global Lung Initiative (GLI) 2012 reference dataset is recommended for use in Australia and New Zealand.
• Covers ages 3-95 years and includes relevant ethnic groups.
• For Aboriginal and/or Torres Strait Islander people, the ‘other/mixed’ category is used.

Lower Limit of Normal (LLN):

• LLN is the cut-point for the bottom 5% of the normal distribution (only 5% of the healthy population fall below this value).

Adjustments for:

1. Sex:
   • FEV1, FVC, FEF25–75%, and PEF: Higher in males than females.
   • FEV1/FVC Ratio: Slightly lower in males than females.
2. Age:
   • Gradual Decline: FEV1, FVC, FEF25–75%, and PEF decrease with age.
3. Height:
   • Increase with Height: FEV1/FVC ratio increases with standing height.
4. Ethnic Origin:
   • Caucasians: Largest FEV1 and FVC values.
   • South-East Asians, Sub-Saharan Africans, and African-Americans: Lower FEV1 and FVC values compared to Caucasians.
   • Aboriginal and Torres Strait Islander People: FEV1 and FVC values lower than Caucasians but higher than African-Americans, based on data from children and young adults aged 3-25 years.

Conditions Affecting Spirometry Results:

• Acute respiratory tract infection (e.g., cold or flu).
• Chest or abdominal pain of any cause.
• Nausea.
• Diarrhoea.
• Oral or facial pain exacerbated by a mouthpiece.
• Stress incontinence.
• Dementia.

Key Points:

• The GLI 2012 dataset is comprehensive and suitable for a wide age range and multiple ethnic groups.
• LLN is a critical cut-point for interpreting spirometry results.
• Adjustments based on sex, age, height, and ethnic origin are essential for accurate interpretation.
• Certain health conditions can affect the ability to achieve optimal or repeatable spirometry results.

General Instructions before Spiro

avoid::

•  smoking (including the use of electronic cigarettes or water pipe) for at least 1 hour before the test, to prevent acute bronchoconstriction
• consuming alcohol or other intoxicants for at least 8 hours before the test, to prevent problems with coordination, physical performance or comprehension
• exercising vigorously for at least 1 hour before the test, to prevent potential exercise-induced bronchoconstriction.

inhaled bronchodilators should be withheld before  the test

• Strong effort by the patient is important for obtaining accurate values used in diagnosis and monitoring of respiratory diseases. 
• In a person with obstructive lung disease, poor effort could lead to an overestimate of FEV1

 

Relative contraindications for spirometry

Common faults

Common faults include:

• Incomplete inhalation before starting
• forced exhalation
• Sluggish initial start to blow
• Premature termination of blow
• Tongue occlusion
• Biting the mouthpiece
• Glottic closure
• Cough – especially during the first second
• Vocalisation during the blow
• Poor posture (e.g. leaning forward too much)
• Leak (e.g. lips not sealed around mouthpiece)

Dotted lines in the flow–volume curves represent the expected tracing without the fault.

Repeatability of Manoeuvres (Blows)

Curves and Acceptability

• Curves meeting both acceptability and repeatability criteria match closely when superimposed.
• Unacceptable efforts show variation in the shape of the curves and calculated values.

Criteria for Adults and Children Older Than 6 Years

• FEV1: The two largest values from acceptable manoeuvres should be within 150 mL of each other.
• FVC: The two largest values from acceptable manoeuvres should be within 150 mL of each other.

Criteria for Children Aged 6 Years or Younger

• FEV1: The two largest values from acceptable manoeuvres should be within 100 mL or 10% of each other, whichever is greater.
• FVC: The two largest values from acceptable manoeuvres should be within 100 mL or 10% of each other, whichever is greater.

Performing Baseline and Post-Bronchodilator Spirometry

1. Bronchodilator Administration:
   • Administer a bronchodilator dose.
   • Suggested protocol: Four separate doses of salbutamol 100 micrograms/actuation via a pressurised metered-dose inhaler and spacer, with a 30-second interval between each actuation.
2. Waiting Period:
   • Wait 10-15 minutes (minimum of 10 minutes) to allow for maximal response.
3. Post-Bronchodilator Test:
   • Perform a complete spirometry test.

Definition of Positive Bronchodilator Response

For Adults and Adolescents (≥12 years):

• A positive response is recorded if post-bronchodilator FEV1 (or FVC) increases by at least 12% and the absolute increase is at least 200 mL.

For Children (up to 11 years):

• A positive response is recorded if post-bronchodilator FEV1 (or FVC) increases by at least 12%.

Obstructive lung disease	Restrictive lung disease
Reduce in FEV1 more than FVC Therefore FEV1/FVC <70% of predicted value Criteria FEV1/ FVC Ratio <0.7 (70%) or <LLN or for children<85% of predicted)  AND Normal FVC or FVC response to Bronchodilator Severity of Obstruction FEV1 >70% Predicted: Mild FEV1 50 – 69% : Moderate FEV1 <50%: Severe Assess Bronchodilator response: Bronchodilator response with FEV1 or FVC increased >12% at any age (or >200 ml in adults) Consistent with reversible Obstructive Lung Disease (Asthma) Inadequate Bronchodilator response =Consistent with irreversible Obstructive Lung Disease (COPD)	Both FEV1 and FVC < 80%  BUT the FEV1/FVC ratio is normal or high Criteria FEV1 to FVC Ratio >0.7 (or >LLN or for children>85% of predicted) AND FVC < LLN (or for age 5 to 18 years old, <80% of predicted) Assess Severity FVC >80%: Normal FVC >60%: Mild Restrictive FVC >40-50%: Moderate Restrictive  FVC <50%: Severe Restrictive  Additional testing Diffusing lung capacity for Carbon Monoxide (DLCO) DLCO to alveolar volume ratio Expiratory Reserve Volume Precaution Note that mixed obstructive-Restrictive Lung Disease can also occur If spirometry suggests a restrictive ventilatory defect or restrictive component (eg. mixed defect),then further evaluation with static lung volumes is needed to confirm restriction Diffusion capacity helps distinguish parenchymal from extraparenchymal disease.
Chronic obstructive pulmonary disease (COPD)  Asthma  Bronchiectasis Cystic fibrosis  Bronchiolitis  α1 – antitrypsin deficiency	Pulmonary fibrosis Neuromuscular disorders Congestive cardiac failure Sarcoidosis Obesity

Obstruction

Definition:

• Expiratory airflow obstruction means the person is unable to exhale quickly.
• It implies narrowed airways due to factors such as excess mucus, thickening of airway walls, inflammation, contraction of bronchial wall smooth muscle, or collapse of airways.

Causes:

• Diseases: Asthma, chronic bronchitis, COPD, bronchiectasis, cystic fibrosis.
• Other Conditions: Foreign bodies or tumours.
• Transient Causes: Severe acute respiratory tract infections.

Characteristics of Obstructive Ventilatory Pattern

• FEV1/FVC Ratio: Low (less than the lower limit of normal, LLN).
• Flow-Volume Curve: Concave shape.

Interpretation Considerations

• Decreased FEV1 and FVC with Normal or Near-Normal FEV1/FVC Ratio:
  • Commonly due to incomplete inhalation or exhalation by the patient.
  • Other possible reasons:
    • Slow airflow preventing complete lung emptying to residual volume.
    • Early patchy collapse of small airways, likely increasing residual volume.

Classification and Clinical Significance

• FEV1% Predicted: Used to classify severity of expiratory airflow obstruction.
• Context-Dependent Significance: Clinical implications vary based on the patient’s condition and context (e.g., emergency department assessment vs. diagnostic investigation).

Bronchodilator Response

• Determination: Assesses if expiratory airflow obstruction is responsive (reversible) or non-responsive (non-reversible).
• Responsive (Reversible) Obstruction:
  • Characteristic of asthma, where bronchospasm is relieved by rapid-acting bronchodilators.
  • Note: Lack of responsiveness does not exclude asthma; presence of responsiveness does not confirm asthma. Symptoms and clinical features must also be considered.
• Persistent (Fixed) Airway Narrowing:
  • Characteristic of COPD, where airways become permanently narrowed.
  • Some bronchodilator response may still be seen.

Key Points

• Accurate interpretation of spirometry results requires careful consideration of patient effort and potential underlying conditions.
• Clinical context and individual patient conditions play a crucial role in the significance and management of expiratory airflow obstruction.

Restriction

Definition:

• Reflects small lung volume without airflow obstruction.

Characteristics:

• FVC: Low (less than the lower limit of normal, LLN).
• FEV1/FVC Ratio: Normal or high.
• Flow-Volume Curve: Shows small volume.

Note:

• Reduced FVC alone does not confirm true restriction.

Further Testing:

• Required to make a specific clinical diagnosis if a restrictive pattern is identified.

True Restriction:

• Indicates reduced total lung capacity compared with normal.
• Causes:
  • Pulmonary fibrosis
  • Pulmonary oedema
  • Interstitial lung disease
  • Pleural/chest wall disease
  • Weak respiratory muscles
  • Rib deformity
  • Neuromuscular diseases affecting respiratory muscles
  • Pleural effusion
  • Obesity

Mixed Ventilatory Pattern

Definition:

• Reflects reduced lung capacity with expiratory airflow obstruction.

Characteristics:

• FEV1/FVC Ratio: Low (less than LLN).
• FVC: Low (less than LLN).
• FEV1% Predicted: Reduced.
• Flow-Volume Curve: Concave shape with small volume.

Examples:

• Seen in conditions like cystic fibrosis.

Note:

• Mixed ventilatory defects are relatively uncommon compared to obstructive or restrictive patterns alone.
• Requires further assessment by a specialist respiratory facility.

Key Points

• Restrictive Pattern:
  • Requires further tests to confirm true restriction.
  • True restriction involves reduced total lung capacity.
• Mixed Pattern:
  • Involves both obstructive and restrictive features.
  • Indicates the need for specialist respiratory assessment.

 

MEASURING GAS EXCHANGE: DLCO

Transfer of CO from alveoli to blood is diffusion limited:

• CO binds hemoglobin 210 times more efficiently than O2 and normally very low concentration in blood
• Thus, limited by surface area, membrane thickness & blood flow/Hb

Use of DLCO

• Restrictive Disease
  • Low- intrinsic disease (parenchymal lung disease)
  • Normal- extraparenchymal causes of restriction (obesity, neuromuscular disease, chest wall limitations)
• Obstructive Disease
  • Low- emphysema
  • Normal- asthma
• • Isolated reduction in DLCO–> raises possibility of
• pulmonary vascular disease