Spirometry vs Peak expiratory flow rate

Pulmonary Function Tests_PFT
Spirometer

1. Spirometry vs. Peak Expiratory Flow Rate Pulmonary Function Tests

2. What is Spirometry? Is the most important diagnostic test for COPD & asthma. It measures the volume of air inhaled, the volume exhaled and the rate at which the patient exhale. May be used periodically to assess effectiveness of medications. Most important variables: FVC: “forced vital capacity”-the total exhaled volume FEV₁: “forced expiratory volume in one second” FEV₁/FVC ration: their ratio The slow vital capacity can be measured which collect data for at least 30 seconds. Useful when FVC is reduced & airway obstruction is present. Values expressed as L/sec

3. Factors A ffecting Results : Age: Lung function generally increases with age up to ~25yrs, then declines with increasing age afterwards. Sex: Pre-pubescent males & females have same lung function Post-puberty, growth of thorax is greater in males Height: The taller the person, the bigger the lungs. Weight: Increasing weight causes increasing lung function until obesity is reached. Ethnic origin Smoking: Cause a more rapid decline in lung function.

4. Peak Expiratory Flow Rate : Is the maximal(how fast & hard) rate at which a person can exhale after full inspiration. Is affected by the fullness of: Fullness of the preceding inspiration Caliber of the large airways Expiratory muscle strength Voluntary effort Predominantly assesses large airway caliber & can underestimate the effects of asthma in the small airways. Validity dependent on maximal effort. Normal value: 10L/s (600mL/min) in healthy adult. Device used is called a Peak Flow Meter. Values expressed as L/min

5. Steps in Measuring PEFR: Step 1 : Move marker to 0 Step 2 : Patient to stand or sit up straight Chin slightly elevated & look straight ahead Step 3 : Empty lungs (as much as possible) Step 4 : Breathe in (deeply) Step 5 : Put mouthpiece between lips Between teeth & close lips tightly. Do NOT PUT TONGUE ON MOUTHPIECE Step 6 : Blow out Step 7 : Look at meter Step 8: Measure peak flow three times Record highest number reached Called “Personal best peak flow”.

6. PEFR Meter SPIROMETER

7. Obstructive Disorders : Characterised by airflow limitation; There is a decreased airway caliber through either: Smooth muscle contraction Inflammation Mucus plugging Airway collapse in emphysema Characterised by: Reduced FEV₁ Normal (or reduced) VC Normal (or reduced) FVC Reduced FEV ₁/FVC ratio Concave flow-volume loop

8. Restrictive Disorders : Characterised by a loss in lung volume and are much rarer Occurs in: Pulmonary fibrosis Pleural disease Chest wall disorders (kyphoscoliosis) Neuromuscular disorders Pulmonary edema & Obesity (to name a few) Characterised by: Reduced FVC Normal to high FEV₁/FVC ratio Normal looking shape on spirometry trace Possibly a relatively high PEF.