Ventilation-perfusion relationships

Ventilation-perfusion relationships - Ventilation

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entilation erfusion in health & Ventilation perfusion in health & disease rjun inivasan Arjun Srinivasan
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Where was the beginning ?
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istribution of ventilation Distribution of ventilation Spatial & anatomical variation ate of alveolar filling Rate of alveolar filling Rate of alveolar emptying
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entilation distribution C Ventilation distribution RC t f s a s t l o w 100 0 75 R=1 R=2 % of final ) 25 50 R=1 1 C=.5 t = .5 C=1 t =2 olume ( % 0 C=1 t = 1 v 0 1 2 3 sekundy sekundy seconds
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linical relevance Clinical relevance Perfusion is poor & pulsatile at apex roportionately increases from top to P a & P v proportionately increases from top to bottom P A changes minimally with gravity Pressures are max at bottom Pulm edema starts at bottom edistribution of blood flow to apex ntler’s Redistribution of blood flow to apex – antler’s horn
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s not just gravity! Its not just gravity! Lung perfusion in zero gravity situations is more uniform but by no means equally distributed Nunn’s Applied respiratory physiology, 6 th edition
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nderstanding V/Q relationships Understanding V/Q relationships Consider lung as single unit Relationships between P A O 2 , P A CO 2 , alveolar ventilation & pulmonary blood flow Alveolar gas equation Consider lung as multiple units of varying V/Q Clinical consequences in health & disease
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lveolar PO nd PCO Alveolar PO 2 and PCO 2 Determined by the ratio between ventilation and blood flow: V/Q PO 2 and PCO 2 are inversely related through alveolar ventilation Increasing V/Q produces higher P A O 2 and lower P A CO 2 Decreasing V/Q produces lower P A O 2 and higher P A 2
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as Composition in the Alveolar Space Gas Composition in the Alveolar Space PiO2 = (barometric pressure H2O vapor pressure) xFiO2 = (760 – 47) x 0.21 =150 mmHg
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lveolar Gas Equation Alveolar Gas Equation PAO 2 = (PiO 2 ) – (PaCO 2 /R) PaCO 2
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This note was uploaded on 12/03/2011 for the course MEDICINE 350 taught by Professor Dr.aslam during the Winter '07 term at Medical College.

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Ventilation-perfusion relationships - Ventilation

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