V/Q Ratio "Normal" V/Q = 0.8 V = alveolar ventilation Q = pulmonary blood flow (perfusion) "Normal" V/Q depends on "normal" respiratory rate, tidal volume, and cardiac output PaO2 = 100 mm Hg PaCO2 = 40 mm Hg Ventilation/perfusion matching is essential for ideal gas exchange of O2 and CO2 "ideal" V/Q = 1.0 exercise → ↑ cardiac output → vasodilation of apical arteries V/Q approaches 1.0 Distribution of V/Q in Lung Ventilation and perfusion are nonuniformly distributed in normal, upright lung Zone 1 apex of lung decreased ventilation and decreased perfusion V/Q is highest (= 3.0) because of relatively greater decrease in perfusion wasted ventilation PaO2 is highest and PaCO2 is lowest organisms that thrive in high O2 (e.g., TB) flourish in apex of lung Zone 3 base of lung V/Q is lowest (= 0.6) wasted perfusion PaO2 is lowest and PaCO2 is highest V/Q Defects Dead Space (V/Q → ∞) e.g., pulmonary embolism (blood flow obstruction) ventilation of lung regions that are not perfused wasted ventilation physiologic dead space no gas exchange occurs PAO2 has same composition as humidified, inspired air (= 150 mm Hg) PACO2 = 0 mm Hg 100% O2 improves PaO2 Shunt (V/Q = 0) e.g., airway obstruction, dependent portion of lung in ARDS can act as "shunt" perfusion of lung regions that are not ventilated wasted perfusion no gas exchange pulmonary capillary blood has same composition as venous blood 100% O2 does not improve PaO2
QUESTIONS 1 of 4 1 2 3 4 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.PL.13.27) In which of the following pathological states would the oxygen content of the trachea resemble the oxygen content in the affected alveoli? QID: 100830 Type & Select Correct Answer 1 Emphysema 16% (17/107) 2 Pulmonary fibrosis 12% (13/107) 3 Pulmonary embolism 48% (51/107) 4 Foreign body obstruction distal to the trachea 11% (12/107) 5 Exercise 13% (14/107) M 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (M1.PL.13.15) A child accidentally aspirates a small pebble that lodges in the lower portion of the right inferior lobe. A radiograph is shown in Figure A. What changes are expected to occur in the arterial blood supply for this portion of the lung? QID: 100818 FIGURES: A Type & Select Correct Answer 1 Increased, secondary to arterial vasodilation 4% (6/137) 2 Increased, secondary to active hyperemia 2% (3/137) 3 No change, due to autoregulation 4% (5/137) 4 Decreased, secondary to arterial vasoconstriction 88% (120/137) 5 Decreased, secondary to a decrease in surfactant synthesis 0% (0/137) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic
All Videos (1) Login to View Community Videos Login to View Community Videos V/Q Mismatch explained Keshav Mudgal Respiratory - V/Q Mismatch D 11/3/2015 198 views 4.2 (4) Respiratory | V/Q Mismatch Respiratory - V/Q Mismatch Listen Now 11:59 min 3/1/2022 18 plays 3.0 (1)