1. Breathlessness-a physiological basis for discussion M.C.F.Pain

2. Breathless Heart aches, Lungs pant, The dry air Sorry, scant. Legs lift And why at all? Loose drift, Heavy fall. Prod the snow, Its easiest way: A flat step Is holiday ********** One step One heart-beat Stone no nearer Dragging feet. Heart aches, Lungs pant The dry air Sorry, scant Wilfrid Noyce, written at 21,100 feet on May 23 rd.

3. Breathlessness is a group of sensations with multiple qualitative descriptors described in terms of “how it is felt” unconscious patient cannot be breathless An all-embracing definition is difficult and usually involves a mechanistic approach “Breathlessness arises when there is a recognition by the subject of an inappropriate relationship between respiratory work and total body work”

4. Four key words Recognition Inappropriate Respiratory work Total body work

5. Recognition Some form of detector mechanism within the respiratory system which rises to a conscious level Perception-some similarity to other sensory modalities pain,sound,light Area of psychophysics 2 questions Is it there? How big is it? Psychophysical experiments show a spectrum of perceptive ability in a normal population for most modalities.

6. Inappropriate implies a bank of experience in which “appropriate” information is stored. “We get used to things” “inappropriate”, if a chronic state, becomes “acceptably” appropriate. temporal adaptation (nasal fatigue)

7. Respiratory work = ventilatory work normally mostly inspiratory ventilation = breath size x frequency breath size= inspiratory flow x duty cycle = V T /T i x T i /T tot stretching work - Elastic airflow work - Resistive

8. frequency work ER V E =K

9. LoadDrive Work Ventilation Gas exchange PO 2 PCO 2 pH

10. LoadDrive Work Higher centres (limbic system) Mechanoreceptors Irritant receptors Chemoreceptors Baroreceptors Temperature Stiff lungs Narrow airways Chest wall Diaphragm Threshold for work perception range in normals modified by time drug modification

11. Carbon dioxide tension Ventilation 1.5l/min/mmHg 40 60 80 10 20 30 L/min mmHg Ventilatory response to carbon dioxide

13. A clinical analysis of breathlessness implies seeking answers to; 1. Clinical evidence of load or drive abnormality? 2. Appropriate investigations to confirm this 3. An explanation in terms of causation

14. A warning! “A clinical physiologist offering a unifying hypothesis for breathlessness should be viewed with the same suspicion as a tattooed archbishop offering a free ticket to heaven”. E.J.M.C