spirometry

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Dr. Maha YousifDr. Maha Yousif

Assist. Lecturer of Chest Diseases Minufiya University, Egypt

E-mail: drmahayousif@gmail.com

Oct. 2008

Basics of spirometryBasics of spirometry

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Contraindications to spirometry

• No absolute contraindications.• FVC manoeuvre raise intra-cranial, intra-thoracic and intra-

abdominal pressures so, Relative contraindications may be:

◆ Recent eye, thoracic or abdominal surgery ◆ Recent myocardial infarction, uncontrolled hypertension or pulmonary

embolism ◆ Recent cerebrovascular haemorrhage or known cerebral or

abdominal aneurysm ◆ Pneumothorax ◆ Haemoptysis of unknown origin (FVC maneuver may aggravate

underlying condition.) ◆ Acute disorders affecting test performance (e.g. vomiting, nausea,

vertigo)

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Patient preparation

Before the test ◘ Avoid: • Acohol 4h • Large meal 2h• Smoking 1h• Vigorous exercise 30min

◘ Wear loose , comfortable clothing.

◘ relaxed, and have time to visit the toilet.

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• For bronchodilator reversibility testing withhold bronchodilators prior to the test:

◘ Short-acting inhaled β2 agonists for 2–4h.

◘ Short-acting inhaled anticholinergics for 4–6 h.

◘ Long-acting inhaled or oral β2 agonists for 12–24 h

◘ Long-acting inhaled anticholinergics for 24–36 h.

◘ Theophyllines for 12 h.

◘ Sustained release theophyllines for 24 h.

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Calibration

• To ensure accurate recording of the tested lung volumes.

• Daily routine.• A spirometer that is transported from one location to

another and exposed to changes in temperature should be re-calibration before use.

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Performing the test

• Explain the procedure.• Check any contraindications,complied instructions as

withholding bronchodilators, not smoking,……• Accurately measure height, standing (without shoes)• If patients are unable to stand, or have a severe spinal

deformity such as a scoliosis, height can be estimated by measuring arm span.

• Enter the patient data to the software.N.B: 1. False teeth, unless they are very ill-fitting and loose, should be left in.2. Record any deviations from the ideal so that subsequent tests can

be carried out under the same conditions

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Correct position of head and body

• Seating Position:(The standing position is not advised), The test position should be noted on the report.

• Upright position:

• Position of the head :upright or slightly leaned back. (If the neck is flexed forward the upper airways are narrowing.

• No leaning forward during the test.

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Slow expiratory vital capacity( SVC,EVC).

Should be tested before any forced maneuvres

SVC Maneuvre• 1) Breath normally (Facultative)• 2) Execute a maximal slow inspiration• 3) Execute a maximal slow expiration• 4) Breath at rest

Wait a minute or so before attempting another recording

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Slow Vital Capacity (SVC)

Main parameters measured are:• EVC: Slow expiratory vital capacity( SVC).• IVC : Inspiratory Vital cpacity• ERV: Expiratory reserve volume• IRV: Inspiratory reserve volumeOthers are: • VE: Expired Volume per minute• Vt : Tidal Volume• Rf: Respiratory Frequency• Ttot: Duration of a complete respiratory cycle• Ti/Ttot, Vt/Ti

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Forced Vital Capacity

FVC Manoeuvre• 1) Breath normally (Facultative)• 2) Execute a Forced Maximal inspiration• 3) Execute a Forced maximal expiration• 4) Execute a maximal inspiration (Facultative)• 5) Breath at restWait at least 1 minute before attempting another recordingN.BNormally, the SVC and FVC are nearly equal. But in airway

obstruction SVC > FVC.

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Forced Vital Capacity

The Main Measured Parameters are:• FVC Forced Expiratory Vital Capacity.• FEV1 Forced Expired Volume after one second.• FEV1/FVC% Percentage of FEV1 against the FVC.• PEF Expiratory Peak flow.• MEF 25-75% (FEF 25-75% )Mean Forced expiratory

flow.The representative graphs are:• The flow-volume curve (loop).• The volume-time curve.

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Flow / volume curve Volume / time curve

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The volume/time curve

• A normal volume/time curve has a typical shape. There is a rapid rise to the trace as three-quarters of the air is expired in the first second

• The trace plateaus between 4 and 6 seconds

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A normal flow/volume curve has a typical shape

◘ Rises almost vertically to PEF

◘ The trace merges smoothly with the horizontal axis of the graph at FVC

The flow/volume curve

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Mid-expiratory flow rates (MEF25, MEF50, MEF75)

• MEF25: ‘The maximum flow achievable when 75% of the FVC has been expired’ (when 25% of the FVC remains in the lungs).

MEF75: refers to the maximum flow achievable when 75% of the FVC remains in the lungs and the MEF50 is the maximum flow rate achievable when the lungs are half-empty

• a sign of early airflow obstruction (small airway disease).

• Some spirometers use the equivalent of MEF: the forced expiratory flow (FEF25, FEF50 and FEF75).

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• Peak expiratory flow: the highest flow achieved from a maximal forced expiratory manoeuvre started without hesitation from a position of maximal lung inflation’

• occurs very early in a forced expiration – within the first tenth of a second

• airflow from the larger airways

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Common errors

Coughing

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• Failure to expire to FVC: The volume/time trace will fail to plateau

The flow/volume trace will not merge with the horizontal axis and will ‘drop off’

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• Slow start to the forced expiratory manoeuvre:• Will give an ‘S’ shape to the start of the volume/time trace,

The flow/volume trace will have a sloping, rather than vertical start

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• Air leak:

The volume/time trace will ‘dip’ downwards, rather than rise steadily to a plateau

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Technical acceptability

• Maximum effort for the forced manoeuvre• Immediate exhalation from the position of maximal

inspiration• No coughing• Complete exhalation.• Traces are smooth and free of irregularity• The volume/time trace should plateau for at least 1

second and there should not be an ‘S’ shape to the beginning of the trace

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• The flow/volume trace should rise almost vertically to a peak and the trace should merge smoothly with the horizontal axis at the end of the blow

• At least three technically acceptable manoeuvres should be obtained, ideally with less than 0.2 L (5%) variability for FEV1 (and FVC) between the highest and second highest result. Quote the largest value.

• If the difference is > 5% this means Sub-maximal effort. (repeat the test)

• Reductions in PEF and FEV1 have been shown when inspiration is slow and/or there is a 4–6 s pause at total lung capacity (TLC) before beginning exhalation

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Spirometry interpretation

• Spirometry parameters are considered to be within the normal range if:

• The FEV1, FVC and VC are between 80% and 120% of the reference value for someone of that age, gender, height and ethnic group

• The FEV1/FVC is about 75% (0.75) or over 80% of the reference value for someone of that age, gender, height and ethnic group

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Obstructive abnormality

• Spirometry parameters compatible with airflow obstruction are:

◘ A reduced FEV1/FVC, or FEV1/VC. Values of less than 70% and/or less than 80% of the reference value

◘ An FEV1 of less than 80% of the reference valueN.B: When the slow vital capacity is higher than the FVC,

the FEV1/VC should be calculated◘ Once the diagnosis of obstructive abnormality is made,

comment on: Severity of obstruction. Reversibility of obstruction

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Severity of obstruction

• The severity of reductions in the FEV1% pred can be characterized by the following scheme:

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Reversibility test

• Response to β agonist is assessed after 10-15 min after inhalation of (100 mcg each, 400 mcg total dose) albuterol administered through a valved spacer device. When concern about tremor or heart rate exists, lower doses may be used. Response to an anticholinergic drug may be assessed 30 minutes after 4 inhalations (40 mcg each, 160 mcg total dose) of ipratropium bromide.

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Reversibility test

• FVC before and after bronchodilator

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Restrictive abnormality

• Spirometry parameters compatible with a restrictive abnormality are:

◘ An FEV1, FVC and VC reduced to less than 80% of their reference value

◘ A normal or high FEV1/FVC, or FEV1/VC (about 75%). The FEV1/FVC will be over 80% of the reference value

◘ The severity of restriction is based on the degree of reduction in FVC % Pred.the same classification as obstructive abnormality.

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Mixed abnormality

• Reduced FVC & a low FEV1/FVC% ratio.• Means: a combination of both obstruction and

restriction, or airflow obstruction with gas trapping. It is necessary to measure the patient's total lung capacity to distinguish between these two possibilities.

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Examples of lesions of the major airway detected with the flow-volume loop

1. Variable extrathoracic lesions  ◘ Vocal cord paralysis

  ◘ Subglottic stenosis  ◘  Hypopharyngeal or tracheal tumour

   ◘ Goiter

2. Variable intrathoracic lesions   ◘ Tumor of lower trachea (below sternal notch)    ◘ Tracheomalacia    ◘ Strictures    ◘ Wegener's granulomatosis or relapsing polychondritis

3. Fixed lesions   ◘ Fixed neoplasm in central airway (at any level)    ◘ Vocal cord paralysis with fixed stenosis    ◘ Fibrotic stricture

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Maximum Voluntary Ventilation (MVV)

• Normally, the MVV is approximately = FEV1×40. If the FEV1 is 3.0 L, the MVV should be approximately 120 L/min.

• MVV/(40×FEV1)< 0.80 indicates that the MVV is low relative to the FEV1, means:

◘ a major airway obstruction◘ neuromuscular diseases (amyotrophic lateral sclerosis,

myasthenia gravis, polymyositis).◘ Poor patient performance due to weakness, lack of

coordination,◘ the subject is massively obese? The MVV tends to

decrease before the FEV1 does.

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Maximum Voluntary Ventilation (MVV)

MVV Manoeuvre• Breath in and out deeply and rapidly for 12 second.

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Obstructive abnormality: very severe, Restrictive abnormality: moderate (mixed).

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Obstructive abnormality: very severe, Restrictive abnormality: severe (mixed).

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Obstructive abnormality: severe, Restrictive abnormality: mild (mixed).

42Moderate restrictive abnormality

43Normal spirometry

44Mild restrictive abnormality

45Restrictive abnormality: moderatey severe

46Obstructive abnormality: moderately severe.

The EndThe End