Exam 3: 1 Apr Understanding Pulmonary Function and Mechanics Flashcards
What is the significance of PO2 in relation to dead space?
PO2 would probably be lower than what the PO2 is in dead space
Dead space refers to areas of the lungs where gas exchange does not occur.
What is the total pressure of all gases typically used for calculations?
760 mmHg
This is the standard atmospheric pressure at sea level.
What does the flow volume loop indicate during expiration?
It helps assess the effort-independent phase and airway collapse
A normal flow volume loop shows a specific shape that indicates healthy airflow.
What does a low FEV1/FVC ratio indicate?
It indicates difficulty in getting air out of the lungs
FEV1 stands for Forced Expiratory Volume in one second, and FVC stands for Forced Vital Capacity.
What is FEF25-75?
It is a measure of forced expiratory flow rate occurring during the middle part of the breath
This measurement is often used to assess small airway reactivity.
What happens to FRC when a person moves from an upright to a supine position?
FRC is reduced
FRC stands for Functional Residual Capacity.
What remains unchanged when changing from upright to supine position?
Total lung capacity
Total lung capacity may decrease slightly in certain cases, such as obesity.
What do expired gases indicate about the pulmonary system?
They provide clues about what is happening in the lungs
Expired gas analysis can help diagnose respiratory conditions.
What is observed in the first part of the expired breath?
It does not contain CO2 from inspired air
This is due to the presence of dead space in the respiratory system.
What should the end-tidal CO2 be in a healthy individual?
Approximately 40 mmHg
This is consistent with arterial blood gas measurements in healthy individuals.
What effect does adding fresh air have on alveolar PCO2?
It decreases the concentration of CO2 in the alveoli
Fresh air typically has negligible CO2 content.
What is the average alveolar PCO2 in a healthy individual?
40 mmHg
This is the typical partial pressure of CO2 in the alveoli during normal respiration.
How much air is typically in the lungs between breaths?
Approximately 3 liters
This is the volume corresponding to the Functional Residual Capacity.
What is the fractional concentration of CO2 in the lungs?
About 5%
This is derived from the ratio of the partial pressure of CO2 to the total pressure of gases.
What is the effect of breathing in 350 cc of fresh air?
It increases the total lung volume to 3.35 liters
This calculation includes the existing volume in the lungs.
What happens to the concentration of CO2 after adding fresh air?
It decreases
This is due to the dilution effect of fresh air that is low in CO2.
What is the volume of fresh air mentioned?
3.35 liters
What is the initial CO2 concentration before fresh air is inhaled?
5.263%
What is the new CO2 concentration after inhaling fresh air?
4.7%
What is the approximate PCO2 after one breath of fresh air?
35.8 mmHg
What is the average alveolar PCO2?
40 mmHg
How much does the alveolar PCO2 fluctuate on average?
±4 mmHg
What happens to CO2 concentration in the lungs over time after breathing in fresh air?
It increases due to CO2 unloading.
What does a higher V/Q ratio at the apex of the lung indicate?
More fresh air is getting to the top of the lung.
In healthy lungs, what influences the gases present in the alveoli?
A mixture from various parts of the lungs.
What are the expected CO2 concentrations at the top and base of the lung in emphysema?
Top: lower than average; Base: higher than average.
What does an inverted slope on the capnograph indicate in someone with severe emphysema?
Massive airway collapse during expiration.
What causes the delay in the capnograph readings?
Length of tubing and low flow rate.
What is the purpose of using a moisture trap in the capnograph?
To prevent clogging and inaccurate readings.
What does the end-tidal CO2 represent?
It approximates arterial blood gases.
What is alveolar dead space?
Air spaces that do not participate in gas exchange.
How can alveolar dead space be estimated?
By comparing end-tidal CO2 and arterial PCO2.
What is the Bohr equation used for?
To estimate the amount of alveolar dead space.
What are the two types of dead space?
- Anatomical dead space
- Alveolar dead space
What should the CO2 levels be in anatomical and alveolar dead spaces?
Very low or zero CO2.
What is the formula for the amount of CO2 in expired air?
It comes from ventilated and perfused alveoli.
What is the relationship between tidal volume and CO2 expelled?
CO2 expired equals tidal volume times the concentration of CO2.
What is the formula for calculating the amount of CO2 in expired air?
The amount of CO2 in expired air equals tidal volume multiplied by the fractional concentration of CO2 in the mixed expired air.
Tidal volume is typically around 500 cc’s.
What does the term ‘VA’ represent in the context of lung physiology?
VA represents the volume of alveolar air.
This is important for calculating gas exchange in the lungs.
How do you calculate the volume of alveolar air (VA)?
VA is equal to tidal volume minus dead space volume (VD).
The formula is VA = VT - VD.
What is the relationship between mixed expired CO2 and CO2 from healthy alveoli?
The amount of CO2 in the mixed expired sample must equal the amount of CO2 coming from the healthy areas of the lung.
This indicates the contribution of functional alveoli to expired gases.
What is the normal value for fractional expired CO2 in healthy individuals?
The fractional expired CO2 should be lower than 5%.
This is typically around 27 mmHg for mixed expired CO2.
What does ‘VD’ stand for in respiratory physiology?
VD stands for the volume of dead space.
This includes both anatomical and physiological dead space.
What is the significance of the Bohr equation in respiratory physiology?
The Bohr equation allows for the calculation of physiological dead space based on the differences in CO2 fractions.
It helps estimate the efficiency of ventilation.
True or False: Alveolar CO2 is typically around 40 mmHg in healthy individuals.
True.
This is a standard reference point for normal alveolar gas exchange.
What happens to the total pressure in the equation when calculating fractional concentrations?
The total pressure cancels out of the equation when it is present in all terms.
This simplifies calculations for fractional concentrations.
What is the estimated physiologic dead space for a healthy 20-year-old?
The estimated physiologic dead space is about 150 cc’s.
This can increase with age or certain medical conditions.
Fill in the blank: The formula for calculating the volume of dead space divided by tidal volume is equal to the difference in the fractional alveolar concentration of CO2 minus the _______.
mixed expired fractional concentration of CO2.
This relationship is crucial for understanding ventilation efficiency.
What does ‘F’ represent in the context of gas concentrations?
F represents the fractional concentration of a gas.
This is often expressed as a decimal.
What is the clinical relevance of calculating alveolar dead space?
Calculating alveolar dead space helps assess ventilation efficiency and guide ventilatory support.
High alveolar dead space indicates poor gas exchange.
What is the equation used to solve for total dead space?
Physiologic dead space is calculated using the equation involving VD, CO2 and subtracting anatomical dead space from VT CO2.
VD = Physiologic dead space, VT = Tidal volume, CO2 = Carbon dioxide concentration.
How is compliance defined in terms of the pulmonary system?
Compliance reflects how easy it is to get fresh air into the lungs and how easy it is to get air out of the lungs.
What are the two main barriers to air entering the lungs?
- Elastic recoil of the lungs
- Chest wall compliance
What does the elastic recoil of the lung want to do?
The elastic recoil of the lung wants to be as empty as possible.
What happens to chest wall compliance when a patient is lying on their back?
Chest wall compliance is reduced due to extra weight on the chest.
What is the effect of losing lung elastic recoil on the chest wall?
If lung elastic recoil decreases, the chest wall may protrude outward, leading to increased lung volume.
What is the relationship between lung volume and pleural pressure in emphysema?
In emphysema, lung volumes are greater even with a less negative pleural pressure.
What is the formula for calculating compliance?
Compliance = ΔV / ΔP.
What is the normal pulmonary compliance at functional residual capacity (FRC)?
Normal pulmonary compliance is about 0.2 liters per centimeter of water.
In terms of compliance, how do individual components of the respiratory system relate to the overall system?
The system compliance is less than the compliance of either individual component.
True or False: The compliance of a series system is greater than the compliance of its individual parts.
False.
Fill in the blank: The total resistance in a series system is calculated as _______.
R1 + R2.
What happens to pleural pressure if lung elastic recoil decreases?
Pleural pressure may become more positive.
How does the chest wall behave when the lung’s elastic recoil is lost?
The chest wall tends to protrude outward.
What is resistance in the context of current flow?
Resistance is how hard it is to push current through a system.
How do you calculate total resistance in a series circuit?
Total resistance is the sum of the individual resistances: R_total = R1 + R2.
What happens to total resistance in a parallel circuit?
Total resistance is lower than each individual resistance.
What is the formula for total resistance in a parallel circuit?
1/R_total = 1/R1 + 1/R2.
If R1 and R2 are both 2 ohms in a parallel circuit, what is the total resistance?
Total resistance is 1 ohm.
What does compliance measure in the pulmonary system?
Compliance measures how easy it is to put air into the lungs using a given amount of pressure.
How does resistance relate to compliance?
Resistance indicates how hard it is to move air, while compliance indicates how easy it is.
If the compliance of the chest wall is 0.2 L/cm H2O, what is the compliance of the lung?
The compliance of the lung is also 0.2 L/cm H2O.
What is the formula for total compliance in a series arrangement?
Total compliance is lower than either of the individual compliances.
What happens to lung inflation if the chest wall integrity is compromised?
The lung will deflate and be difficult to inflate.
What is pneumothorax?
Pneumothorax is an opening for air that fills the pleural space, making it hard to inflate the lung.
What generates negative pleural pressure?
Negative pleural pressure is generated by the opposing recoil of the chest wall and lung.
Fill in the blank: The total resistance in a series circuit is equal to _______.
R1 + R2
True or False: In a parallel circuit, increasing the number of pathways increases total resistance.
False
What will happen if blood fills the pleural space?
It will make it difficult to ventilate the lung.
What is the compliance of the system if both chest wall and lung compliance are 0.2 L/cm H2O?
The compliance of the system will be 0.1 L/cm H2O.
What is the relationship between the chest wall and lung in terms of their arrangement for airflow?
The chest wall and lung are arranged in series.
