Gas Exchange Flashcards
(35 cards)
What is pulmonary ventilation?
The volume of air breathed in and out per minute
PV = Tidal volume x Respiratory rate
What is alveolar ventilation?
The volume of air exchanged between the atmosphere and alveoli per minute
What does anatomical dead space refer to?
The inspired air that remains in the airways
Why is alveolar ventilation less than pulmonary ventilation
Anatomical dead space
To increase pulmonary ventilation both ____ and ____ must increase
Depth / Tidal Volume
Respiratory rate
Is it more advantageous to increase the depth of breathing or respiratory rate in terms of increasing pulmonary ventilation; and why?
Depth
Because of dead space
What is ventilation?
The rate at which gas is passing through the lungs
What is perfusion?
The rate at which blood is passing through the lungs
Does ventilation or blood flow vary from the top to the bottom of the lung?
Both
What is the effect of variation in ventilation and blood from from the top to the bottom of the lung?
Partial arterial and alveolar pressure of oxygen are not the same (only significant difference in disease)
Ventilated airways that are not adequately perfused are considered _____?
Dead space
Do perfusion and ventilation always match?
No
What are the mechanisms of ventilation perfusion matching?
Local controls that act on smooth muscles of airways and arterioles to match ventilation and perfusion
What ventilation perfusion match response is initiated by increased CO2 levels in the alveoli?
Decreased airway resistance leading to increased airflow and subsequent increase in alveoli –> pulmonary vasodilation –> increased blood flow
What is the physiological response to perfusion > ventilation in terms of blood flow?
Increased CO2 –> relaxation of smooth muscle in airway –> Dilation of local airways –> Decreased airway resistance –> increased airflow
What is the physiological response to perfusion > ventilation in terms of small airflow?
Decreased oxygen –> increased contraction –> constriction of local blood vessel (vasoconstriction) / systemic arteriole vasodilation–> increased vascular resistance –> decreased blood flow
What is the physiological response to perfusion < ventilation in terms of large airflow?
Decreased CO” –> contraction of smooth muscle in local airway –> constriction of local airways –> increased airway resistance –> decreased airflow
What is the physiological response to perfusion < ventilation in terms of small blood flow?
Increased O2 –> relaxation of local pulmonary arteriolar smooth muscle –> vasodilation of local blood vessels / vasoconstriction of systemic arterioles –> decreased vascular resistance –> increased blood flow
Which four factors influence the rate of gas exchange across the alveolar membrane?
- Partial pressure of a gas
- Surface area of alveolar membrane
- Membrane Thickness
- Diffusion coefficient
What is the partial pressure of a gas?
The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature
What is Dalton’s Law of Partial Pressures?
Total pressure exerted by a gaseous mix is the sum of the partial pressure
How do you calculate the partial pressure of oxygen in alveolar air (PAO2) when oxygen is continuously diffuses from alveoli into the blood?
PAO2 = PiO2 - [PaCO2/0.8]
What is the respiratory exchange ratio?
0.8
What is PAO2?
Partial pressure of oxygen in alveolar air
