BGYC33/CC4 Respiratory System Study Guide, Lectures 11-12 (2011)
Lecture 11: Alveolar Ventilation and Blood Gases
The Inert Gas Technique Reviewed
Minute Ventilation (VI)
Breathing Frequency (fR )
Tidal Volume (V T )
Alveolar Ventilation (VA)
Dead Space Ventilation (DSV)
Increasing Breathing Frequency and Tidal Volume
Calculating Alveolar Ventilation
The Assumptions and Approximations
Measuring Alveolar Ventilation using Exhaled and Arterial CO 2evels
Partial Pressure of Gases
Composition of Air; Atmospheric Pressure; Relative Humidity
Partial Pressures of Gases throughout the Circulatory System
Perfusion Limitation of O2Uptake and CO E2cretion
Eupnea; Hyperpnea; Apnea; Dyspnea
Normoxia; Hyperoxia; Hypoxia
Normocapnia; Hypercapnia; Hypocapnia
Daily Oxygen Consumption
Calculating Daily Oxygen Consumption
Concluding that Dissolved Oxygen can’t Meet Daily Oxygen Demands
1) Which of the following is a reason for using the following equation to measure alveolar
V A = (VCO 2 K) / P aCO 2
a) Anatomical dead space volume (K) is relatively easy to estimate.
b) PACO =2P aCO 2
c) Arterial pCO2is easily calculated from the Henderson-Hasselbach equation once arterial pH is
measured (which is easy to do)
d) PaO2is easy to measure. 2
2) How many of the following 6 statements are false?
1) PCO 2 in blood entering the systemic veins is less than or equal to tCO 2in the tissue cells.
2) PO 2in blood leaving the pulmonary capillaries is equal to theO2 in blood entering the systemic
3) PO 2in the tissue cells is slightly less than (or at most equal toO 2in blood leaving the
4) PCO 2 in blood entering the pulmonary capillaries is equal to thCOP2in the alveoli.
5) PO2 in mixed venous blood is equal to PCO 2in arterial blood in the systemic arteries.
6) PO2 in the atmosphere (at sea level) is equal to alveolaO2.
3) Blood with an arterial PCO2of 45 Torr and an arterial PO2of 90 Torr is referred to as:
a) Hyperoxic hypercapnic
b) Hyperoxic hypocapnic
c) Hypoxic hypercapnic
d) Hypoxic hypocapni