Lecture 9 2/1/24 Flashcards
Which processes are involved with delivering gases within the body?
-ventilation
-circulation
-perfusion
-diffusion
What is ventilation?
movement of gas into and out of the lung
What is minute ventilation?
total volume of air breathed per minute
What is tidal volume?
the volume of each breath
What is respiratory frequency?
the number of breaths per minute
What are the characteristics of pulmonary circulation?
-receives total output of right ventricle
-low pressure and low resistance
-involved in gas exchange
What is perfusion?
delivery of blood in capillaries surrounding the alveolar space in the lungs
What is a V/Q ratio?
comparison of ventilation to perfusion
What is diffusion?
flow of particles from a region of high pressure to a region of low pressure
Where does gas movement take place?
-within alveoli: air to air
-across alveoli into blood: air to liquid
-from blood into tissues: liquid to tissues
What are the general characteristics of conducting airways?
-conduits to get air to alveoli
-no gas exchange occurs
Which spaces comprise anatomic dead space?
-nasal cavity
-pharynx
-larynx
-trachea
-bronchi
-bronchioles
What are the characteristics of alveolar dead space?
-caused by poor perfusion of alveoli
-prevents gas exchange
-blood flow is disrupted/absent while alveolus is ventilated
What is physiologic dead space?
alveolar dead space + anatomic dead space
Why is it important to minimize the amount of plastic tubing when ventilating a patient?
decrease the amount of dead space contributed by the tubing
What is the importance of calculating the tidal volume minus the dead space volume?
it represents the actual volume of gas available for gas exchange
What are the characteristics of minute ventilation?
-amount of fresh gas entering lungs per minute
-estimated by resp. rate x tidal vol. in simplest form
What is alveolar ventilation?
amount of fresh gas reaching the alveoli per minute
How can alveolar ventilation be increased?
-increase tidal volume
-increase respiratory rate
Why is it possible to measure alveolar ventilation?
-no gas exchange occurs in the anatomic dead space, thus all CO2 must come from alveolar gas
-measuring CO2 in clinic can provide a measure of alveolar ventilation
What are the characteristics of the dead space/tidal volume ratio?
-identifies the fraction of each breath that ventilates dead space
-can change with disease and exercise
-changes tend to reflect alveolar/physiologic dead space changes