Spirometry Interpretation Acceptability *minimum of 3 acceptable manoeuvres *good start and satisfactory effort *no artefacts induced by coughing or glottic closure in 1st second, or equipment problems *minimum of 6 seconds exhalation and/or plateau in the volume time curve *Maximal inspiration prior to blow
Artefacts a)No artefact b)Cough within 1 st second of forced exhalation c)Incomplete exhalation/early termination (glottic closure) d)Slow start/submaximal forced effort at start of blow e)Hesitant start
Reproducibility *two largest FVC within 0.150 L (150ml) of each other *two largest FEV1 within 0.150 L (150ml) of each other *must meet criteria for acceptability If the reproducibility criteria is not met after a total of 8 tests, stop testing.
Disease Patterns Obstructive pattern A disproportionate reduction of maximal airflow from the lung in relation to the maximal volume Restrictive pattern Characterised by a normal FEV 1 /VC ratio and reduction in FVC below the 5th percentile of the predicted Mixed pattern Characterised by the coexistence of obstruction and restriction, and is defined physiologically when both FEV 1 /FVC and FVC are below 5th percentiles of the predicted value
Spirometric overlap between Asthma and COPD *COPD has been described as a disease characterized by fixed airflow obstruction because in many patients FEV1 values improve little after bronchodilator challenge. *Current guidelines on diagnosis and management describe COPD as a condition that is partially reversible because some patients exhibit substantial improvements in FEV1 (despite an FEV1-FVC ratio that remains below 0.70) that compares in magnitude to what is observed in some asthma patients. *Tashkin et al (2008) have shown that about 54% of a large COPD cohort (N = 5756) exhibited an improvement in FEV1 values > 12% and 200 mL, while about 65% of patients had FEV1 increases > 15%. *This substantial overlap in FEV1 reversibility between asthma and COPD underscores an important limitation of using this measurement to distinguish between asthma and COPD. Can Fam Physician. Oct 2011; 57(10): 1148–1152.
Reversible Obstruction The lungs and spirogram show a pattern of airway obstruction (black), with the spirogram showing a marked improvement after the administration of a bronchodilator (red) Vitalograph Ltd 1986 &2000
Age: 29; Gender: Female; Height: 162 cm; Weight: 98.6 kg; BMI: 37.57 Spirometry measurePre bronchodilator best Post bronchodilator best % improvementReferenceRef ± CI FVC, L 2.223.51 58 3.75 3.1 – 4.4 FEV1, L 1.49 2.68 80 3.18 2.6 – 3.8 FEV1/FVC, % 67 76 74.9 – 94.4
Irreversible Obstruction The lungs and spirogram show a pattern of airflow obstruction, with the spirogram showing little or no improvement after the administration of a bronchodilator Vitalograph Ltd 1986 &2000
Response to ß2-agonist ß2-agonist bronchodilator *Dose: 4 puffs of ß2-agonist delivered through a spacer device *Wait 15-20 minutes before repeating spirometry *Significant response defined as >12% and more than 200mL increase in either the FEV1 or FVC.
Severity classification Degree of severityFEV1 % predicted Mild>70 Moderate60-69 Moderately severe50-59 Severe35-49 Very severe<35 Severity of any spirometric abnormality based on the forced expiratory volume in one second (FEV1) ATS/ERS Task Force: Standardisation of lung function testing. Interpretative strategies for lung function tests. Eur Respir J 2005; 26: 948
Interpretation algorithm National Asthma Council Australia: www.nationalasthma.org.au Yes No
Spirometry interpretation algorithm: Primary Care Respiratory Alliance of Canada Asthma vs COPD (history)Consistent with asthma Refer to specialist FEV1, 12% and 200mL Restrictive disorder Reduced < LLNNormal (not COPD) FVC ≥ 80% predicted FEV1 and FVC ß2-agonist Reduced < LLNNormal > LLN Pre ß2-agonist FEV1/FVC ratio Modified from Primary Health Care Alliance of Canada spirometry interpretation algorithm 2011
https://www.youtube.com/watch?v=yNDKD_xI684 Spirometry Education Pulmonary Function Tests (PFT): Lesson 2 - Spirometry Published on Feb 3, 2014 A discussion of FEV1, FVC, FEV1/FVC ratio, and the flow volume loop, including how these are used in the diagnosis of various lung diseases, with a particular focus on the distinction between obstructive and restrictive lung disease. A summary of flow volume loop patterns in upper airway obstruction is covered as well.