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Spirometry in practice

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Brief guide for the use and interpretation of spirometry.

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Spirometry in practice

  1. 1. Spirometry in Practice • A technique used to measure air flow in and out of the lungs. • A recording of lung volumes and capacities defined by the respiratory process. These recordings may be static (untimed) or dynamic (timed). • Assesses the integrated mechanical functions of lungs, chest wall and respiratory muscles. •The gold standard for diagnosis, assessment and monitoring of COPD. • Better than PEFR (which is effort dependent) for demonstrating airway obstruction in BA. • The most commonly used PFT.
  2. 2. Indications • Measure airflow obstruction to help make a definitive diagnosis of COPD • Detect airflow obstruction in smokers who may have few or no symptoms • Assess one aspect of response to therapy • Perform pre-operative assessment • Distinguish between obstruction and restriction as causes of breathlessness • Perform pre-employment screening in certain professions
  3. 3. Flow Sensitive Spirometer • Utilizes a sensor that measures air flow as the primary signal and calculates volume by integration. • Automatically calculates a wide range of ventilatory indices and draw curves, which provide an immediate feedback on quality.
  4. 4. How to DO? Before the Test 1) Exclude contraindications: • Haemoptysis of unknown origin. • Current chest infection or within in last 6 weeks. • Pneumothorax. • Recent myocardial infarction or PE (< 3 m). • Unstable angina in last 24 hours. • Recent surgery (eye, chest, abdomen) (< 3m). • Recent CVA (< 3m). • Aneurysm (cerebral, thoracic, abdominal).
  5. 5. How to DO? Before the Test 2) Stop Asthma Medications: • SABA 6h • LABA 12h • Ipratropium 6h • Tiotropium 24h Medications may be continued if the test aims to assess the patient condition on treatment.
  6. 6. How to DO? Before the Test 3) Other Precautions: • Physical and mental rest. • No coffee or smoking for 30 mins. • Empty the bladder in females or those with history of urinary incontinence.
  7. 7. How to DO? • Patient is sitting comfortably, not leaning forwards, legs not crossed, feet firm on floor. • No tight clothes or collars. • Explain the procedure to the patient. • Nasal clip is optional. During the Test
  8. 8. How to DO? • Ask the patient to do a Forced Expiratory Maneuver (FEM): - Take a maximal inspiration. - Hold the breath and seal your lips tightly around the mouth piece. - Blow as fast as possible (blast expiration) until the lungs feel completely empty (at least 6 sec., up to 12 sec in obstructive disease) During the Test • Repeat the test 3 times and record the highest reading • Continue watching, explanation and encouragement throughout the procedure.
  9. 9. • Submaximal effort o Submaximal effort o Air leak around the mouthpiece (lips not tight enough) o Air leak through nose o Incomplete inspiration before the forced expiratory maneuver (not at TLC) o Incomplete or weak expiration (lack of blast effort) o Slow start of expiration o Cough (particularly within the first second of expiration) o Glottic closure o Obstruction of the mouthpiece by the tongue o Vocalisation during the forced manoeuvre o Poor posture (leaning forwards). o Extra- breath during the blow Causes of Poor Record
  10. 10. Spirometry includes: • Lung volumes (most simple). • Lung capacities (composite of > 2 volumes) • Volume per time: as FEV1,2,3,4,5,6 • Volume / Time Curve. • Flow / Volume Loop.
  11. 11. Total Lung Capacity Tidal Volume Inspiratory Reserve Volume Expiratory Reserve Volume Residual Volume Inspiratory Capacity Vital Capacity End Normal Exp End Normal Insp End Maximal Insp End Maximal Exp Functional Residual Capacity
  12. 12. Predicted Normal Values  Age  Height  Sex  Ethnic Origin Affected by biodemographic variables:
  13. 13. Obstructive Pattern Restrictive Pattern •↓ VC •↓ FEV1 / FVC •↑ RV •↑ RV / TLC •↓ PEF • Normal FEV1 / FVC •↓ Other lung volumes, capacities
  14. 14. Normal Obstructive Restrictive
  15. 15. Volume Time Curve
  16. 16. Flow Volume Loop Expiratory flow rate L/sec Volume (L) FVC Peak expiratory flow (PEF) Inspiratory flow rate L/sec RVTLC Peak Inspiratory flow (PIF)
  17. 17. (> 0.7) (< 80%) (< 0.7) (< 80%)(< 80%) (< 80%) (< 80%)
  18. 18. Bronchodilator Reversibility Testing •FEV1 should be measured (minimum twice, within 5% or 150mls) before a bronchodilator is given Bronchodilator* Dose FEV1 before and after Salbutamol 400µg 15minutes Terbutaline 500µg 15minutes Ipratropium 160µg 45minutes
  19. 19. Bronchodilator Reversibility Testing • An increase in FEV1 that is both greater than 200 ml and 12% above the pre-bronchodilator FEV1 (baseline value) is considered significant (Up to 8% increase may occur in normal persons). • It is usually helpful to report the absolute change (in mL) as well as the % change from baseline to set the improvement in a clinical context . • The absence of reversibility does not exclude asthma because an asthmatic person’s response can vary from time to time and at times airway calibre is clearly normal and incapable of dramatic improvement.
  20. 20. 6 4 8 3 7 2 1 9 Inspiratory Capacity (IC) 5
  21. 21. Look at FEV1/FVC and FVC FEV1/FVC > 0.7 FVC > 80%P FEV1/FVC< 0.7 FVC > 80%P FEV1/FVC > 0.7 FVC < 80%P FEV1/FVC < 0.7 FVC < 80%P NORMAL OBSTRUCTIVE RESTRICTIVE MIXED or OBSTRUCTIVE + AT Provocation Test BD Reversibility Test ?Parenchymal or ExtraParenchymal BD Reversibility Test If asthma suspected Reversible Not Reversible Reversible Not Reversible BA COPD OBSTRUCTIVE + AT RV, TLC Mixed High Low
  22. 22. Parenchymal RLD Extraparenchymal RLD FVC Decreased Decreased MVV Normal Decreased DLCO Decreased Normal FVC: Forced Vital Capacity MVV: Maximum Voluntary Ventilation DLCO: Carbon Monoxide Diffusion
  23. 23. % Predicted FEV1 FVC )or TLC( Obstruction Restriction 65> -80 Mild 50> -65 Moderate >50 Severe Degree of Ventilatory Impairment
  24. 24. FVC = 50%P )< 80%P( FEV1/FVC = 0.41)< 0.7( ∴Mixed or Obstructive + AT BD Reversibility: -6% )NO( RV, TLC not provided There are 2 possibilities: 1( Mixed Ventilatory Defect 2( Obstructive + AT
  25. 25. Measured FEV1 Predicted FEV1 Measured FVC Predicted FVC FEV1/FVC FEV1 after Bronchodilator Is there obstructive hypoventilation? What evidence? Is there restrictive hypoventilation? What evidence? What is the degree of ventilatory impairment? Is there significant reversibility after bronchodilator? What evidence? Matching condition: BA/Interstitial Pulmonary Fibrosis/Emphysema/Acute rhinitis How to Present Your Analysis of Spirometry Results?

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