Gas Exchange Unit
● The purpose of the heart is to drive the hemoglobin to the cell
● The purpose of the lungs is to oxygenate and ventilate the hemoglobin
● To oxygen and ventilate hemoglobin, the brain, muscles of respiration, & the alveolar
capillary membrane must work well
● Brain controls the rate, character of respiration, & muscles of respiration
● Diaphragm promotes ventilation
● Alveolar capillary membrane is where gas exchange occurs
○ Oxygen molecules pass through the alveolar capillary membrane to the plasma as
a dissolved free molecule
○ Most of the oxygen molecules enter to the RBCs to bind to hemoglobin
○ CO2 diffuses from higher to lower concentration gradient
○ O2 diffuses from higher to lower concentration gradient
● Type 1 and type 2 cells in alveoli
○ Type 1- squamous cells that are responsible for gas exchange
■ The alveoli are single cell layer thick in line with squamous cells that
facilitate the diffusion of CO2 & O2 for gas exchange
○ Type 2- help produce surfactant
■ Prevent alveoli from collapsing
■ Atelectasis- alveoli collapse
V/Q Matching
● V- ventilation → gas in the alveolar sac
● Q- perfusion → blood in the capillary associated with the alveoli
● The goal is to have gas in the alveoli and blood in the capillary bed so that ventilation &
perfusion match
● A- Absolute shunt → pus/fluids in the lungs diverts oxygen
○ Pneumonia, pulmonary edema, ARDS
● C- matching
● E- Deadspace → no perfusion due to obstruction of the pulmonary capillary
○ Pulmonary embolism
● SpO2/SaO2- oxygen saturated in hemoglobin
● PaO2- partial oxygen dissolved in plasma not bound to hemoglobin
● Hypoxia- decreased oxygenation at the tissue level
, ● Hypoxemia- decreased oxygenation within arterial blood
O2-Hemoglobin Disassociation Curve
● Demonstrates the relationship of oxygen to hemoglobin
● Shows the affinity between Hgb and O2, how much is bound, and how much is freely
available
● Curve takes on sigmoidal shape
○ Hgb has an increased affinity for oxygen as the number of oxygen molecules
bound goes up
● Normal PaO2
○ 80-100
● Minimum oxygen concentration to provide enough oxygen to prevent ischemia is 90%
○ PaO2 also drops as fewer and fewer O2 are bound to Hgb
● PaO2 values are much slower than O2 saturation values
● Factors shifting the curve to the right (release/decreased affinity)
○ More O2 available so that tissues/cells can benefit from it
○ High hydrogen ions, low pH (respiratory acidosis)
○ High CO2
○ Increased temperature (fever)
○ Increased 2,3-BPG
■ Hyperthyroidism
■ Anemia
■ Chronic hypoxemia
● High altitude
● Congenital heart disease
○ Some congenital hemoglobinopathies
● Factors shifting the curve to the left (lock/increased affinity)
○ O2 and Hgb don’t want to let go, less O2 dropped off to the tissues
○ Low hydrogen ions, high pH (respiratory alkalosis)
○ Low CO2 (hyperventilation)
○ Low temperature (hypothermic)
■ Pulse ox may say 100%, but the patient is not getting the O2 at the tissues
because the Hgb and O2 are not letting go
○ Decreased 2,3-BPG
, ■ Byphospoglyceric acid
■ Chemical produced by RBCs that helps facilitate the release of O2 to the
tissues
■ Hypothyroidism
■ Bank blood → PRBCs don’t have 2,3-BPG
○ Some congenital hemoglobinopathies
○ Carboxyhemoglobin
■ Hemoglobin is more attracted to carbon monoxide than oxygen
Rapid Sequence Intubation (RSI)
● Rapid, concurrent administration of both sedative & paralytic agents to decrease the risk
of aspiration & injury to the patient (sedation first then paralytic)
● Not indicated for patients in cardiac arrest because they are already unresponsive
● Preparation
○ IV
■ Two large bore
● The purpose of the heart is to drive the hemoglobin to the cell
● The purpose of the lungs is to oxygenate and ventilate the hemoglobin
● To oxygen and ventilate hemoglobin, the brain, muscles of respiration, & the alveolar
capillary membrane must work well
● Brain controls the rate, character of respiration, & muscles of respiration
● Diaphragm promotes ventilation
● Alveolar capillary membrane is where gas exchange occurs
○ Oxygen molecules pass through the alveolar capillary membrane to the plasma as
a dissolved free molecule
○ Most of the oxygen molecules enter to the RBCs to bind to hemoglobin
○ CO2 diffuses from higher to lower concentration gradient
○ O2 diffuses from higher to lower concentration gradient
● Type 1 and type 2 cells in alveoli
○ Type 1- squamous cells that are responsible for gas exchange
■ The alveoli are single cell layer thick in line with squamous cells that
facilitate the diffusion of CO2 & O2 for gas exchange
○ Type 2- help produce surfactant
■ Prevent alveoli from collapsing
■ Atelectasis- alveoli collapse
V/Q Matching
● V- ventilation → gas in the alveolar sac
● Q- perfusion → blood in the capillary associated with the alveoli
● The goal is to have gas in the alveoli and blood in the capillary bed so that ventilation &
perfusion match
● A- Absolute shunt → pus/fluids in the lungs diverts oxygen
○ Pneumonia, pulmonary edema, ARDS
● C- matching
● E- Deadspace → no perfusion due to obstruction of the pulmonary capillary
○ Pulmonary embolism
● SpO2/SaO2- oxygen saturated in hemoglobin
● PaO2- partial oxygen dissolved in plasma not bound to hemoglobin
● Hypoxia- decreased oxygenation at the tissue level
, ● Hypoxemia- decreased oxygenation within arterial blood
O2-Hemoglobin Disassociation Curve
● Demonstrates the relationship of oxygen to hemoglobin
● Shows the affinity between Hgb and O2, how much is bound, and how much is freely
available
● Curve takes on sigmoidal shape
○ Hgb has an increased affinity for oxygen as the number of oxygen molecules
bound goes up
● Normal PaO2
○ 80-100
● Minimum oxygen concentration to provide enough oxygen to prevent ischemia is 90%
○ PaO2 also drops as fewer and fewer O2 are bound to Hgb
● PaO2 values are much slower than O2 saturation values
● Factors shifting the curve to the right (release/decreased affinity)
○ More O2 available so that tissues/cells can benefit from it
○ High hydrogen ions, low pH (respiratory acidosis)
○ High CO2
○ Increased temperature (fever)
○ Increased 2,3-BPG
■ Hyperthyroidism
■ Anemia
■ Chronic hypoxemia
● High altitude
● Congenital heart disease
○ Some congenital hemoglobinopathies
● Factors shifting the curve to the left (lock/increased affinity)
○ O2 and Hgb don’t want to let go, less O2 dropped off to the tissues
○ Low hydrogen ions, high pH (respiratory alkalosis)
○ Low CO2 (hyperventilation)
○ Low temperature (hypothermic)
■ Pulse ox may say 100%, but the patient is not getting the O2 at the tissues
because the Hgb and O2 are not letting go
○ Decreased 2,3-BPG
, ■ Byphospoglyceric acid
■ Chemical produced by RBCs that helps facilitate the release of O2 to the
tissues
■ Hypothyroidism
■ Bank blood → PRBCs don’t have 2,3-BPG
○ Some congenital hemoglobinopathies
○ Carboxyhemoglobin
■ Hemoglobin is more attracted to carbon monoxide than oxygen
Rapid Sequence Intubation (RSI)
● Rapid, concurrent administration of both sedative & paralytic agents to decrease the risk
of aspiration & injury to the patient (sedation first then paralytic)
● Not indicated for patients in cardiac arrest because they are already unresponsive
● Preparation
○ IV
■ Two large bore
