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INTERNAL. EXTERNAL. SPINE. RIBCAGE. SPINE. Outside pressure. Inside pressure. P = atmospheric pressure. P . P. P = 0. P = 0. P = 0. P = 0. P = -5. NORMAL. PNEUMOTHORAX. flat thoracic wall spring. flat thoracic wall spring. coiled lung spring. coiled lung spring.
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INTERNAL EXTERNAL SPINE
RIBCAGE SPINE
Outside pressure Inside pressure
P = 0 P = 0 P = 0 P = 0 P = -5 NORMAL PNEUMOTHORAX
flat thoracic wall spring flat thoracic wall spring coiled lung spring coiled lung spring minimum volume V1 FRC NORMAL PNEUMOTHORAX
VOLUME 100 100 % TLC % VC 75 50 50 25 lung 0 pump 0 -40 -20 0 cm H2O INTRAPLEURAL PRESSURE
P varies with T T varies inversely with r So P varies inversely with r Surfactant reduces T more if r ↓ r Fluid lining So T now does not vary with r and neither does P P T ↓ T r ↑ Surface tension
200 150 100 50 0 0 5 10 15 20 SALINE VOLUME ml AIR INFLATION PRESSURE cm H2O
VOLUME 100 100 % TLC 75 V1 50 50 25 lung 0 pump 0 -20 0 20 cm H2O INTRAPLEURAL PRESSURE
V1 Inspiratory muscles FRC Volume Min Vol -’ve Intrapleural Pressure
100 100 % TLC % VC 75 V1 50 50 FRC 25 0 0 -20 0 20 cm H2O
100 100 % TLC % VC 75 V1 50 50 FRC FRC 25 0 0 -20 0 20 cm H2O
Laminar Flow Turbulent Flow Airway Flow
TLC 16 12 glottis CROSS-SECTIONAL AREA (square cm) 8 4 RV 0 0 12 24 36 42 80 DISTANCE FROM MOUTH (cm)
52 48 pressure to overcome elastic recoil 44 40 36 32 pressure to overcome tissue movement resistance pressure to overcome airway resistance INSPIRATION thorax wall lung % VC -10 -8 -6 -4 -2 0 Intrapleural Pressure cm H2O
52 48 recoil pressure 44 40 pressure to overcome airway resistance 36 pressure to overcome tissue movement resistance 32 pressure to overcome persistent inspiratory muscle activity EXPIRATION thorax wall lung % VC -10 -8 -6 -4 -2 0 Intrapleural Pressure cm H2O
52 Work done by the inspiratory muscles overcoming airway resistance lost as heat 48 44 40 36 32 INSPIRATION % VC thorax wall lung Work done by the inspiratory muscles overcoming tissue movement resistance lost as heat Work done by the inspiratory muscles overcoming system compliance stored as potential energy in the lung compliance Potential energy yielded by the thoracic wall compliance stored as potential energy in the lung compliance -10 -8 -6 -4 -2 0 Intrapleural Pressure cm H2O
52 48 44 40 36 32 EXPIRATION % VC Work done by the stored potential energy overcoming airway resistance lost as heat thorax wall lung Work done by the lung compliance stored potential energy overcoming tissue movement resistance lost as heat Work done by the lung compliance stored potential energy overcoming the persistent activity of the inspiratory muscles Potential energy yielded by the lung compliance stored as potential energy in the thoracic wall compliance -8 -6 -4 -2 0 Intrapleural Pressure cm H2O
total work of breathing resistive work against airway & tissue movement resistance WORK OF BREATHING elastic work against compliance BREATHING FREQUENCY (breaths/minute)
0 52 48 44 40 36 32 % VC End Expiration thorax wall lung 0 Airway opening pressure = 5 PI = -5 PA = 0 5 5 -5 -10 -8 -6 -4 -2 0 PM = 0 Intrapleural Pressure cm H2O
0 52 48 44 40 36 32 % VC During Inspiration thorax wall lung -1 Airway opening pressure = 7 PI = -8 PM PA = -2 6 4-1=3 -3 -10 -8 -6 -4 -2 0 PM = 5 Intrapleural Pressure cm H2O
0 52 48 44 40 36 32 % VC End Inspiration thorax wall lung 0 PM Airway opening pressure = 7 PI = -7 PA = 0 7 3 -7 -3 -10 -8 -6 -4 -2 0 PM = 4 Intrapleural Pressure cm H2O
0 52 48 44 40 36 32 % VC During Expiration thorax wall lung 0.5 Airway opening pressure = 5.5 PI = -5 PA = 1 6 4+1=5 -5 -10 -8 -6 -4 -2 0 PM = 0 Intrapleural Pressure cm H2O
Airway closing pressure = 10 % VC 52 thorax wall lung 48 44 40 36 32 -5 -10 -8 -6 -4 -2 0 Intrapleural Pressure cm H2O During Forced Expiration 0 16 PI = 26 PA = 32 6 4 PM = 30