Lung Function Assessment M.C.F.Pain

Lung Function Assessment M.C.F.Pain pain@netspace.net.au Ventilation 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 litres VT mls DS mls VA litres 5.0 10 500 150 350 x 10=3.5 5.0 20 250 150 100 x 20=2.0 Blood oxygen transport 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  ... 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