Unit 2, L3 Lung Mechanics B Flashcards
What is the volume of tidal breathing
About 500 mL
What is the volume of inspiratory reserve volum
3 liters
What is the volume of the expiratory reserve volume
1.2 liters
What is the volume of the residual volume
1.2 liters
What is the inspiratory reserve volume?
Everything that is left at the end of tidal inhale
What is the expiratory reserve volume
Everything you didn’t exhale at the end of a tidal breathing
What is residual volume?
When you exhale out as hard as you can, whatever is left (as you can’t breathe all the air out) is the residual volume
What is the volume of total lung capacity?
5.8 liters
What is the volume for vital capacity?
4.6 liters
What is the volume of functional residual capacity?
2.4 liters
What is the equation for inspiratory capacity?
Inspiratory capacity (IC) = Inspiratory reserve volume (IRV) + tidal volume (Vt) = 3.5 liters
What is the equation for functional residual capacity?
FRC = Expiratory reserve volume (ERV) + residual volume (RV) = 2.4 liters
What is the equation for vital capacity/
VC = Inspiratory reserve volume (IRV) + tidal volume (Vt) + Expiratory reserve volume (ERV) = 4.6 liters
What is the equation for total lung capacity?
TLC = inspiratory reserve volume (IRV) + tidal volume (Vt) + expiratory reserve volume (ERV) + residual volume (RV) = 5.8 liters
What volumes cannot be measured with a spirometer?
RV, FRC, and TLC
During exercise, which of the following statements is true? A) IRV and ERV are increased B) IRV is increased; ERV is decreased C) IRV is decreased; ERV is increased D) IRV and ERV are decreased
D, IRV and ERV are both decreased, as tidal breathing gets bigger in both directions, so will push into both reserve volumes
How does the helium dilution method work
Patient has no helium in lungs to begin, and there is a container with a known concentration of helium within in, and the volume of the container is known. So when the patient breaths in the helium, it will go to equilibrium with the lungs, and can use the equation C1 * V1 = C2*(V1+V2) and solve for V2
How does body plethysmograph work?
A person is sitting in a tank, which is sealed tight, and you know the initial pressure and volume within the tank. Patient is breathing against a fixed tube, so there is no air flow going in but the chest can still expand. Can measure the pressure at the mouth, as that will match pressure in the alveoli, then use the equation P1V1=P2V2, where V1 is initial lung volume (VL), V2 is VL + delta VL, P1 is the initial pressure, and P2 is P-delta P, so we can measure everything except for VL, which we can solve for
The helium method starts to fail in what type of diseases
Obstructive respiratory diseases, as the airways begin to close
Lung compliance definition
Measure of the elastic properties of the lung, defined as the change in lung volume per change in pressure
What is elastic recoil
The tendency to deflate following inflation, result of elastic fibers and surface tension
What is hysteresis
Non-recoverable work required to inflate, proportional to delta between inflation and deflation
The pressure volume loop shown in class has 5 steps. Explain them.
1) Starting at residual volume, pleural pressure is at 0 mmHg, and volume is low (so starting at 0 on x-axis and very low on y-axis)
2) Pleural pressure starts to decrease, volume will slowly start to increase but its a small change, as there is low compliance, until reaching the critical opening pressure (PCo)
3) Once past PCo, slope becomes more linear, as there is high compliance, meaning a larger increase in volume of the lungs, until approaching TLC
4) After hitting TLC, the lungs begin to deflate (exhale), so pleural pressure is becoming less negative/more positive, and the lungs begin to return to residual volume
5) However, there is a gap between the two lines (inhale and exhale) because there is hysteresis, which is non-recoverable work required to inflate the lungs
What happens to the pressure-volume loop if you remove the air water interface (saline inflation)?
There is no critical opening pressure, its easy to put the fluid in, no energy needed to pop stuff open. Small changes in pressure will lead to large changes in volume, and this is the elastic recoil of the tissue. There is very little delta and hysteresis, nearly all the energy to expand the lungs is recovered during deflation. Shows that surface tension is the primary driver of the hysteresis
What happens to the pressure volume loops if you wash out the surfactant but re-establish the air water interface?
Will have max surface tension, gives a major shift in the PCO, takes more and more energy and pressure to pop open the airways. The slope also changes, showing that surfactant was helping open the airways earlier AND was helping compliance. There is a lower TLC, cannot open the lungs to where we were before, and there is massiv ehysteresis
Air flow at a given pressure gradient is determined by
Pattern of air flow and resistance to air flow by airways
Reynold’s number equation
Re = (2*(radius)(velocity)(density))/viscosity
Most of the conducting zone will be (turbulent, transitional, or laminar)
Turbulent and transitional
Most of the lungs that are experiencing air flow will be (turbulent, transitional, or laminar)
Laminar
Is airway resistance calculated in a series or in parallel?
Parallel, which explains why resistance drops as we move down, as this spreads out total resistance across the system
Airway cross-sectional area and air velocity (or airway resistance) are (inversely or proportional)
Inversely proportional, so if one increases, the other will decrease
As the individual airweays are getting smaller, the aggregate cross sectional area is _______, and what will this do to resistance
The cross sectional area is increasing dramatically, which will reduce resistance
What will increase radius and decrease airway resistance
Increasing lung volume, smooth muscle relaxation, and sympathetic stimulation
What will decrease radius and increase airway resistance
Mucus, edema, smooth muscle contraction, and vagal stimulation
What will increasing lung volume do to the radius and airway resistance?
It will increase the radius and decrease airway resistance
What will smooth muscle relaxation to do the radius and the airway resistance?
It will increase the radius and decrease airway resistance
What will sympathetic stimulation do to the radius and the airway resistance?
It will increase the radius and decrease airway resistance
What will mucus and edema do to the radius and airway resistance?
It will decrease radius and increase airway resistance
What will smooth muscle contraction to do radius and airway resistance?
It will decrease radius and increase airway resistance
What will vagal stimulation do to the radius and airway resistance?
It will decrease radius and increase airway resistance
What measurement is reduced in obstructive pulmonary disease?
FEV1
What measurement is reduced in restrictive pulmonary diseases?
FVC
FEV1 is what?
Forced expiratory volume in 1 second
What is the normal value for FEV1/FVC
Above 75%
PEFR is what
Peak expiratory flow rate
PIFR is what
Peak inspiratory flow rate
Usual value of PEFR and PIFR
About 10 liters per second
At higher lung volumes, is expiratory flow rates effort dependent or effort independnet?
Effort dependnet
At lower lung volumes, is expiratory flow rates effort dependent or independent?
Independent
What is going on with the pressures in dynamic airway compression?
Pressure outside the airways is greater than pressure inside the airways
The bronchiolar wall tends to collapse in response to changes in intrapleural or airway pressure, why?
Because it doesn’t have cartilage, so there is little support
What is friction loss
As a result of airflow resistance, pressure that is generated in the alveoli drops along the airways during expiration
What is the equal pressure point (EPP)?
When airway pressure has dropped to a level where it equals intrapleural pressure during force expiration
At the EPP, airways without cartilage will ______
Collapse
In healthy lungs, the EPP will be reached in cartilaginous airways as a result of
Sufficient alveolar driving pressure and only a gradual drop in pressure due to minimal airway resistance
What is the equal pressure point
Airflow becomes independent of total driving pressure
Airflow resistance is greater during exhalation than inhalation
In a normal lung, equal pressure point in airways with cartilage
Moves downward (towards alveoli) with smaller lung volume
At low lung volumes, will increased effort help with expiratory flow?
No, at low volumes, increased effort will not help because increased effort is increased pressure on the airways, resulting in airway compression
Restrictive pulmonary diseases
Anything that makes the lungs difficult to inflate, could reduce FRC, vital capacity, and TLC
Associated with a decrease in compliance, so a decrease in surfactant, an increase in fibrosis, or pleural effusion (increased fluid in pleural space)
Obstructive pulmonary disease
Collectively anything that increases airway resistance (reduction in FEV1)
Examples of obstructive pulmonary diseases
Infection, so build up of mucus in airways
Asthma, smooth muscle constriction of airways
COPD
What is reduced in an obstructive lung disease
FEV1
What is reduced in a restrictive lung disease
FVC
For obstructive disorders, what changes happen with the FEV1/FVC, FEV1, FVC, TLC, and RV
FEV1/FVC: Decreased FEV1: Decreased FVC: Decreased or normal TLC: Normal or increased RV: Normal or increased
For restrictive disorders, what happens with the FEV1/FVC, FEV1, FVC, TLC, and RV
FEV1/FVC: Normal or increased FEV1: Decreased, normal, or increased FVC: Decreased TLC: Decreased RV: Decreased
What are the two main components of respiratory work (oxygen consumption)
Elastic work: work to overcome lung elastic recoil, work to expand the thoracic cage, work to displace abdominal organs, and is proportional to tidal volume
Non-elastic work: Flow restrictive, work to overcome air flow resistance, proportional to breathing frequency
Normal lungs are _______ compliant (high or low)
Highly compliant
Work required for breathing is increased when
Pulmonary compliance is reduced
Airway resistance is increased
Exercise
Restrictive diseases will do what to elastic work for breathing
Increase the elastic work, breathing becomes more shallow and rapid
Obstructive diseases will do what for the flow-resistive work for breathing
Increase flow-resistive work, so breathing becomes slow and deep
