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