Ch. 5 Flashcards
What is the equation for Ve?
Vt x F
Definition of Ve?
Volume of air during normal RR inspired and expired over 1 min. OR rate of respirations per min.
How long do you measure Ve?
15 secs
Inc. rate usually reflects changes in ______ ?
Vent status
Inc. rate =
Hypoxia
Hypercapnia
Inc. temp
Dec. rate =
• CNS depression
• CO2 narcosis (hyper-oxygenation or O2 toxicity)
• Neuromuscular disease involving vent disorders
What is the respiratory exchange ratio (RER)?
The ratio between the volume of CO2 produced (VCO2) divided by the volume of O2 consumed (VO2).
Fun fact
The ratio of the body’s CO2 output to the uptake of CO2 indirectly shows the muscles oxidative capacity to get energy.
RER must be calculated….?
If the inspiratory volumes are used (machine does this).
What is the formula for RER?
VCO2/VO2
What is the normal for RER?
80%
RER ______ as CO2 production ______ ?
Increases ; increases
How do you measure RER?
• RIP- uses transducers to measure pulmonary ventilation by measuring the movement of the chest and abdominal wall.
• Volume displacement spirometer (water seal spirometer).
• Flow sensing spirometer
• O2 & CO2 analyzer
What are some calculations used for RER?
Vt = Ve/F
Ve = Vt x F
What is the usual range for Vt?
400-700 mls in a healthy adult
Ve must be calculated with _____ values to determine adequacy of the vent?
Blood gas (ABG)
What is normal Ve?
5-10 L/min in healthy adult
Hyperventilation means what?
Body is trying to compensate
Ve does not determine ________ or ________?
Hypoventilation; hyperventilation
Body will compensate for _______ ?
Decreased CO2
What is hypoventilation?
PCO2 > 45 pH < 7.35
What is hyperventilation?
PCO2 < 35 pH > 7.45
What are the 2 types of dead space?
Anatomic & alevolar
together they add up to physiological dead space
What is dead space usually dependent on?
BTPS or LPM
What is anatomic dead space?
Air in the upper airways that do not participate in gas exchange.
What is alveolar dead space?
Lung volumes that are ventilated but not perfused by capillary blood flow. Air is trapped in the small airways (alveoli) that cannot participate in gas exchange.
How to measure Vd?
Exhaled gas is collected over specified interval and measured. Blood gases are taken at the same time to measure PaCO2.
info is added to Bohr equation
What is the formula for Vd?
PaCO2 -PeCo2 / PaCO2
PaCO2 = arterial
PeCO2 = end tidal
How can anatomic Vd be calculated?
By IBW 1mL/lb or 2mL/kg
How to calculate alveolar dead space?
Calculated during measurements of volumes RV/TLC ratio.
Physiological Vd can be important because it takes into account both _____ & ______ Vd?
Anatomic; alveolar
What is alveolar ventilation?
Part of the ventilation that participates in gas exchange at the alveolar level.
What is the formula for alveolar ventilation?
VA = F (Vt -Vd)
Vd is considered equal to _______?
Anatomic Vd (1mL/lb or 2mL/kg of IBW)
What are some techniques to measure ventilator response?
Open circuit and closed circuit
What are some techniques used to measure CO2 & O2?
Open circuit
Closed circuit
CO2 scrubber
What is P100?
The pressure generated at the mouth during first 100 milliseconds of an inspiratory effort against an occluded airway.
this is what drives ventilation
Changes in P100 are directly related to changes in ….?
Body position and contractile properties of the respiratory muscles.
What is the normal range for P100?
1.5-5 cmH20
P100 is increased in?
Hypercapnia and hypoxia
P100 is helpful in?
Determining effects of tx in pts with abnormal ventilation responses measured with closed circuit.
What does a pneumotachometer measure?
The volume of airflow in lungs
