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Respiratory Physiology – more than just spirometry

Explore the intricate details of respiratory physiology beyond spirometry, including gas exchange, lung stress, airflow patterns, and more. Learn how to interpret spirometry results accurately and identify normal and abnormal lung function. Discover the significance of measurements like DLco and FeNO in evaluating respiratory health. Enhance your knowledge to better manage and treat respiratory conditions effectively. This comprehensive guide provides insights into testing and diagnosing respiratory abnormalities for improved patient care.

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Respiratory Physiology – more than just spirometry

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  1. Respiratory Physiology – more than just spirometry Philip Lawrence Senior Respiratory Physiologist

  2. The Lungs ?Stress the lungs Airflow (in and out) Heart Gas Exchange (O2 and CO2) Tissue and lining (inflammation?) Volumes Musculature Pressure Blood supply

  3. Respiratory Physiology Can we test this organ and identify patterns of normality or abnormality? Can we use this to guide our management? Does the physiology change? Physiology is just a snapshot of the lungs at that moment in time Added with clinical history, patient observations – we can better understand and treat a patient.

  4. Spirometry

  5. “Spirometry is invaluable as a screening test of general respiratory health in the same way that blood pressure provides important information about general cardiovascular health.” ATS/ERS Standardisation of Spirometry (2005)

  6. Spirometry Airflow in the lungs - Normal - Obstructive • Restrictive Simple for patients and operator Mixed

  7. Spirometry – Do’s Equipment should be calibrate daily Patients should be seated, with a nose clip on Full > BLAST > Empty Use the correct reference values for normality (GLI, 2012) Ensure results are valid and reliable Clean and Disinfect equipment

  8. Spirometry – Don’ts

  9. PEF FEF75 Spirometry – Interpretation FEF50 ULN Pred LLN FEF25 FVC RV TLC FEV1 PIF

  10. Sharp peak in flow • Triangular shape in expiration flow • Rounded shape in inspiratory flow • Flow steadily falls until zero flow • All indices above LLN Normal Lung Function

  11. Sharp peak in flow (large airways empty) • Loop is concave – “Scooping” • Flow is reduced compared to expectation • FEV1 and FEV1/FVC ratio below LLN and FVC above LLN Obstructive Ventilatory Defect

  12. Sharp peak in flow (large airways empty) • Triangular shape in expiratory flow • Flow is reduced compared to expectation • FEV1 and FVC below LLN, but FEV1/FVC ratio above LLN Restrictive Ventilatory Defect

  13. Sharp peak in flow (large airways empty) • Scooping (concave) • Flow is reduced compared to expectation • FEV1,FVC and FEV1/FVC ratio all below LLN Mixed Ventilatory Defect

  14. Easy and simple Can identify Normal, Obstruction and Restriction Cheap and quick Reference values and widely used Spirometry – the good

  15. Airflow is not the whole story… Volume? Gas Exchange? Stress the Lungs? Airway inflammation? Unnatural test FEV1 = only first 8 generations of the lungs (disease occurs in the small airways) Spirometry – the bad

  16. Spirometry – the bad Black – Normal Lung Function Red – Reduced FVC due to hyperinflation Blue – Reduced FVC due to restriction

  17. Resp Exercise Challenge • 6MWT • CPET Exercise Nitric Oxide Full PFT’s Travel • FeNO • Nasal NO • HCT • Spirometry • DLco • Whole Body Plethysmography

  18. Resp Exercise Challenge • 6MWT • CPET Exercise Nitric Oxide Full PFT’s Travel • FeNO • Nasal NO • HCT • Spirometry • DLco • Whole Body Plethysmography

  19. Whole Body Plethysmography

  20. Whole Body Plethysmography Spirometry measures Vital Capacity (FVC) Unable to measure whole lung volumes – or divisions - Unable to identify restriction WBP allows understanding of this Pressure and volume change Aims to measure FRC VC manoeuvre – Lung Divisions

  21. Whole Body Plethysmography Crieeet al., (2011) Resp Medicine, 105; 959-971

  22. Whole Body Plethysmography Confirm the patient is Restricted (either Physical or Muscular Defect) Confirm the patient has Gas Trapping – indication of airways closing off and trapping air - ?breathlessness Confirm hyperinflation. If FRC is high (normal breathing) patients are breathing away from Respiratory Zone toward Conducting Zone.

  23. Whole Body Plethysmography

  24. Gas Transfer (DLco)

  25. Gas Transfer (DLco) Spirometry measures airflow, but tells us nothing about the ability to take up O2 and release CO2 Able to test this and the surface area for gas transfer using DLco Uses 2 gases • Carbon Monoxide (CO)* • Methane (CH4) *in very small amounts!

  26. Gas Transfer (DLco) CO = Kco CH4 = VA Kco x VA = DLco Taken from: http://bronchiectasis.com.au/bronchiectasis/diagnosis-2/lung-function

  27. Gas Transfer (DLco) • - High KCO, Low VA = Lack of lung expansion or loss of units • - Normal KCO, Low VA = Compensation for low alveolar volume (mild alveolar damage) • - Low KCO, Low VA = Moderate to severe alveolar damage

  28. Fractional Exhaled Nitric Oxide (FeNO)

  29. Fractional Exhaled Nitric Oxide (FeNO) • Asthma is a inflammatory disease • Treatments given often tackle the inflammation • Treatments are often detrimental to the body • So can we test and identify patients who would benefit from treatments?

  30. Fractional Exhaled Nitric Oxide (FeNO) • The driving force of the inflammation is eosinophils • One biomarker of this in the lungs is Nitric Oxide • Measurethe Nitric Oxide exhaled in parts per billion (ppb) • Easy to perform Berkman et al., (2005) Thorax 60; 383-388

  31. The National Institute for Health and Care Excellence (NICE) (2014). Measuring fractional exhaled nitric oxide concentration in asthma: NIOX MINO, NIOX VERO and NObreath

  32. Fractional Exhaled Nitric Oxide (FeNO) Taken from: https://www.niox.com/en/feno-asthma/interpreting-feno/

  33. 12 year old, Female. Difficult to manage Asthma Flutiform 125/5 (2 puffs BD) Salbutamol (PRN) Prednisolone 12.5mg Azithromycin 500mg (x3) FEV1 70% Pred 13 year old, Female. Difficult to manage Asthma Seretide 250 (2 puffs BD) Salbutamol (PRN) Azithromycin 500mg (x3) FEV199% Pred “undertake PE and swimming…best she has ever been” In patient (3 weeks) “beginning to deteriorate…” MTX TRI OZM

  34. Patient recovery Prediction of exacerbation Treatments not successful Treatments successful MTX TRI

  35. Respiratory Exercise Challenge

  36. Respiratory Exercise Challenge • Asthma is often a reversible condition • When a patient presents to clinic can we test the severity of their asthma by bronchostriction? • Many methods • Direct (Methacholine, Histamine) • Indirect (Dry air, Exercise)

  37. Respiratory Exercise Challenge Can be used to answer other questions: - SOB due to fitness or bronchostriction? (Off treatment) - Asthma control - does their medication work? (On treatment)

  38. Respiratory Exercise Challenge • Baseline spirometry • Exercise on treadmill • Warm up - 6mins exercise at 80% HR max • Spirometry 5, 10 and 15min post exercise • >10% drop in FEV1 significant drop • Salbutamol given - spirometry 20mins to test reversibility • Easy to perform, however not direct.

  39. Resp Exercise Challenge • 6MWT • CPET Exercise Nitric Oxide Full PFT’s Travel • FeNO • Nasal NO • HCT • Spirometry • DLco • Whole Body Plethysmography

  40. Thank you – Any Questions? philip.lawrence@alderhey.nhs.uk

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