2.4 Ventilation/Perfusion
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Questions and Answers

What is the consequence of having high ventilation but low perfusion in the lung?

  • Increased gas exchange efficiency
  • No impact on gas exchange
  • Increased dead space (correct)
  • Increased shunt

    • Which of the following describes a reason for nonuniform ventilation of the alveoli?

  • High V/Q ratio throughout the lung
  • Different metabolic demands in different lung regions (correct)
  • Equal distribution of inspired gas
  • Uniform pulmonary blood flow

    • What is the purpose of the shunt equation in understanding pulmonary physiology?

  • To assess airway resistance
  • To calculate cardiac output
  • To quantify the amount of blood bypassing the lungs (correct)
  • To determine oxygen saturation

    • How does physiologic dead space affect gas exchange in the lungs?

    <p>It decreases alveolar ventilation</p> Signup and view all the answers

    Which statement accurately summarizes regional differences in ventilation and perfusion?

    <p>V/Q ratios vary across different lung regions</p> Signup and view all the answers

    How do V/Q ratios relate to gravity in the lungs?

    <p>V/Q ratios are highest at the lung's apex due to gravity</p> Signup and view all the answers

    What influences mixed venous blood to bring CO2 into the lungs and take up alveolar O2?

    <p>Both neural and humoral/chemical regulation</p> Signup and view all the answers

    Which of the following is a pulmonary vasoconstrictor that increases pulmonary vascular resistance (PVR)?

    <p>Histamine</p> Signup and view all the answers

    What effect does sympathetic innervation have on pulmonary vascular resistance (PVR)?

    <p>Increases PVR</p> Signup and view all the answers

    Which chemical is known to produce vasodilation in the pulmonary vasculature?

    <p>Acetylcholine</p> Signup and view all the answers

    What intrinsic autoregulation mechanism produces vasoconstriction in the pulmonary vasculature?

    <p>Hypoxic pulmonary vasoconstriction</p> Signup and view all the answers

    How does parasympathetic innervation affect the pulmonary vasculature?

    <p>Causes vasodilation</p> Signup and view all the answers

    What is the impact on the V/Q ratio when the airway is occluded, preventing ventilation?

    <p>V/Q = 0</p> Signup and view all the answers

    What does a shunt in the context of gas exchange refer to?

    <p>Allows blood to reach the arterial system without passing through ventilated lung regions</p> Signup and view all the answers

    How does a pulmonary embolus affect the V/Q ratio?

    <p>V/Q increases</p> Signup and view all the answers

    What happens if there is matched ventilation and perfusion at the alveolar-capillary unit?

    <p>Optimal gas exchange</p> Signup and view all the answers

    What is the impact of an intrapulmonary shunt on alveoli?

    <p>Alveoli are underventilated or overperfused</p> Signup and view all the answers

    How are small shunts typically identified?

    <p>By measuring partial pressures during 100% inspired oxygen</p> Signup and view all the answers

    What can cause nonuniform ventilation of the alveoli?

    <p>Bronchoconstriction</p> Signup and view all the answers

    What is one cause of nonuniform ventilation due to obstruction according to the text?

    <p>Decreased lumen</p> Signup and view all the answers

    How can one assess the distribution of inspired gas in the lungs?

    <p>Lung scans after IV administration of dissolved Xe</p> Signup and view all the answers

    What may lead to nonuniform compliance in different lung regions?

    <p>Regional variations in surfactant production</p> Signup and view all the answers

    What is the physiological shunt equal to?

    <p>Physiological dead space</p> Signup and view all the answers

    What does a pathological right-to-left intracardiac shunt involve?

    <p>An abnormal passage between the right and left sides of the heart</p> Signup and view all the answers

    What is the equation to calculate venous admixture in the context of shunting?

    <p>Shunt equation</p> Signup and view all the answers

    Supplemental oxygen will not improve which type of shunt?

    <p>Absolute intrapulmonary shunt</p> Signup and view all the answers

    Intrapulmonary shunts are associated with which of the following?

    <p>Collapsed alveoli</p> Signup and view all the answers

    What does increased arterial-alveolar CO2 difference indicate?

    <p>An increase in physiological dead space</p> Signup and view all the answers

    What is the primary cause of a normal (A-a) DO2?

    <p>Ventilation-perfusion mismatch</p> Signup and view all the answers

    Which regions of the lung have high VA/Q ratios?

    <p>&quot;Apical regions&quot;</p> Signup and view all the answers

    Absolute intrapulmonary shunts are also known as 'true shunts' and can be improved with supplemental oxygen.

    <p>False</p> Signup and view all the answers

    Physiological shunt corresponds to anatomic dead space in the lungs.

    <p>False</p> Signup and view all the answers

    Anatomic shunts include venous blood from bronchial, thebesian, and pleural veins entering the left ventricle without passing through pulmonary capillaries.

    <p>True</p> Signup and view all the answers

    Absolute intrapulmonary shunts are associated with well-ventilated alveoli.

    <p>False</p> Signup and view all the answers

    What is the key feature of an anatomic shunt?

    <p>Blood from pleural veins entering the left ventricle without passing through pulmonary capillaries</p> Signup and view all the answers

    How do absolute intrapulmonary shunts differ from shunt-like states?

    <p>Absolute shunts cannot be improved with supplemental oxygen, while shunt-like states can</p> Signup and view all the answers

    What does the shunt equation conceptually divide all alveolar-capillary units into?

    <p>Well-ventilated and poorly ventilated units</p> Signup and view all the answers

    Which is a pathologic characteristic of the pulmonary vasculature that may contribute to nonuniform ventilation of the alveoli?

    <p>Compression by tumors causing regional compliance issues</p> Signup and view all the answers

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