Lung Function Assessment M.C.F.Pain

Lung Function Assessment M.C.F.Pain pain@netspace.net.au... bulk flow distribution Ventilation/blood flow relationships Alveolar-capillary diffusion Blood gas transport Tissue respirati

Lung Function Assessment

M.C.F.Pain

pain@netspace.net.au

bulk flow distribution Ventilation/blood flow relationships Alveolar-capillary diffusion

Blood gas transport

Tissue respiration

Control of breathing

Influence of dead space on alveolar ventilation

VE f VT DS VA

litres mls mls litres

5.0 10 500 150 350 x 10=3.5

5.0 20 250 150 100 x 20=2.0

Blood oxygen transport

1 gram Hb can carry 1.39 mls of oxygen

Oxygen Capacity = Hb x 1.39 + physically dissolved oxygen

normally (15 x 1.39 + 0.3=)21.15 mls/100mls Oxygen content = actual amount of oxygen

Oxygen saturation = oxygen content / oxygen capacity

(normally about 94%) Oxygen tension-oxygen content relationship expressed

In dissociation curve

Hb affinity for oxygen expressed as P50 (normally 26.6mmHg)

“Stingy haemoglobins, CO shift curve to left (low P50), chronic hypoxia shifts curve to right (high P50)

Respiratory muscle weakness

Forced expiration or inspiration against

almost occluded airway.

MIPS about 80 mmHg

MEPS about 100 mmHG

Paralysed diaphragm- postural fall in V.C.

Lung Function during exercise

Six minute walk test Simple and informative

Distance travelled -normally over 500 metres Observation of performance

Dyspnoea score (Borg scale) before and after Time to recover

Oxygen saturation (oximetry) before, during and after (fall in saturation= worsening V/Q relationships)

Formal cardiopulmonary exercise study

Monitor HR, ECG, Gas Exchange under progressively increasing work load

Fitness-aerobic-> anaerobic point VO2max

Inappropriate ventilatory response Inappropriate circulatory response

John B West on U tube

Series of lectures on respiratory physiology from UCSD.