SF3 Exam 2 Respiratory Mechanics Flashcards
Pleural space is filled with? It exerts what type of force?
Pleural fluid. Negative pressure making the lung stick to the chest wall.
Visceral Pleura innervation vs parietal pleura
Visceral insensitive to pain, react to stretch
Parietal pleura somatic afferent and intercostal nerves. Perceives pain
Which generations have no gas exchange?
What is this commonly called?
0-16
Dead space
What range of generations start to have alveoli?
Which ones are most heavily involved in gas exchange?
17-23
20-23
RV Residual Volume
Amount of air that you cannot get out of the lung
Cm H20 is used to refer to?
What is this at room air?
mmHg is used to refer to?
Hydrostatic pressure
0 cm H20
Gas partial pressures
Which bronchus is situated higher?
Right higher than left
Apnea?
Absence of spontaneous ventilation
Eupnea
Normal spontaneous breathing
Orthopnea
Dyspnea which occurs when lying flat, causing person to sleep propped up
How do the lungs stay inflated in your thorax?
They are placed in an area where the intraplueral space is negative, so air tends to inflate them since they have a 0 atmospheric pressure.
Elastic recoil of the chest is?
Elastic recoil of the lung?
Chest- Outwards
Lung- Inwards
Functional Residual Capacity (FRC)
Point where recoil forces (Inner recoil of lung matches outer recoil of chest wall)
What is the main contributor to lung recoil?
Surface tension
How does Surface tension play a role in the lungs?
When on the surface, there are unbalanced forces that pull molecules downward away from the side exposed to air.
Alveoli can be thought of as a circle of air surrounded by water. Explain the surface tension net effect on this
The molecules have angled effects on one another, with an overall vector of inwards towards the air. This is why the lung wants to collapse.
Explain how Laplace’s law would predict 2 alveoli to interact?
The first has r and the second is 2r Laplaces law p=2T/r
What occurs in an actual lung? Describe the relationship.
Revisit the original alveoli with this info.
1st- 2T/r
2nd- 2T/2r=T/r
- SO 1>2
1 would empty into 2, causing a shunt through the lung
Surfactant exists in the lung. It lowers surface tension.
Surfactant is inversely proportional to Surface tension.
Area 1= 4pi(r)^2
Area 2= 4pi(2r)^2
2 is 4 times bigger than 1 (Each has the SAME surfactant) so
1=y/4pi(r)^2
2=y/16pi(r)^2
Surfactant is 4X in Unit 1. Is spread over less area. Since surfactant and Surface tension are inverse, The Surface tension of Unit 2 is 4 times greater.
ACTUAL lung happening.
1=2T/r
2=2(4T)/(2r)= 4T//r
- 2>1
Who are the main players in inhalation?
Diaphragm.
External intercostal muscles lift the rib cage
What are the accessory muscles of inhalation?
When are they used?
Shoulder/neck muscles
Recruited in exercise, COPD and emphysema
What stance is commonly seen in COPD patients?
Why do they do this?
Tripod stance. Sits or stands leaning forward, supporting the upper body with hands on the knees.
This takes advantage of the accessory muscles.
What type of process is normal exhalation?
It is normally passive. The diaphragm is just relaxing back to normal.
When is the Ptm equal to the elastic recoil of the lung in inhalation? What happens throughout inhalation?
Right at the beginning and then again at the end. In the middle, transmural pressure becomes larger than recoil, so the lung expands.
What does Boyle’s law tell us about alveoli
Law is that volume is inverse to pressure, so as they fill with air, the pressure decreases in the pleural space.
Tension pneumothorax
More and more air accumulates with each breath
Non-tension pneumothorax
Air present in cavity, but not accumulating with each breath.
Atelectasis vs Pneumothorax
Atelectasis has NO air entering pleural space. The entire mediastinum shifts to the side of the collapse.
Pneumothorax the mediastinum shifts away from the collapse.
Specific Compliance
Normalize to body size of individual.
SC=Compliance/FRC
Where compliance = V/P
What is used to measure compliance.?
Spirometry
How is total compliance found? What is the relationship?
1/TC=1/lung comp+1/chest wall comp
They are in series, but add reciprocally. This is UNIQUE.
What protein is deficient in emphysema?
Alpha1-antitrypsin
What is regulated by alpha1-antitrypsin?
Elastase activity.
Without the antitrypsin, the lung tissue is destroyed
What is the tissue destruction in emphysema called?
Alveolar simplification
What effect does tissue destruction in emphysema have?
It makes the lung softer and more compliant.
Centrilobular Emphysema is caused by?
What portion of the lung is most effected?
Most common. Long standing cigarette smoking.
Begins at respiratory bronchioles and spreads peripherally. Upper lung most effected
Panacinar emphysema is caused by?
What part of the lung is mostly effected?
Destroys entire alveolus uniformly.
Lower lung most effected
Alpha1-antitrypsin deficiency Or Ritalin induced- crushed pill injected and struck in blood vessels of lungs
Which way does the curve shift for emphysema?
Fibrosis?
Why?
Emphysema- shifts left due to increased compliance from softer tissue
Fibrosis- shifts to the right due to stiffer tissue
What reasons would cause a decrease in compliance?
How does this effect the lung?
Fibrosis
Loss of surfactant
Removal of one lobe
Obesity
Pulmonary Vascular congestion (washes off surfactant)
This makes the lung stiffer and shift to the right.
What reasons would cause an increase in compliance?
How does this effect the lung? What about the curve?
Emphysema and Age
Lung is softer
The curve shifts to the left
Explain how compliance adds in the lungs and chest wall versus within lungs.
Chest wall and lungs add reciprocally
Lungs add straight together
What does Poiseullie Equation tell us?
Laminar flow Resistance is sensitive to radius
(sensitive to radius to the 4th power)
What are the airways arrangement?
Which type has the lower resistance? The highest?
They are arranged in parallel, so you add reciprocally for resistance.
Smaller airways have much lower resistance.
Larger airways have much higher resistance.
How does the velocity in airways work (large v small)?
Also how does resistance work in these vessels (large v small)?
Large airways have high velocity and high resistance
Smaller airways have low velocity and low resistance
Ex) 4 lanes merging into 2 and cars going faster
Explain passive exhalation
Relax diaphragm
Negative intrapleural pressure
Positive alveolar that gets less positive as it goes toward the mouth.
Negative intrapleural pressure holds open airway entire time.
Explain Forced Exhalation. Where is this an issue?
What explains this?
You force an exhale, muscles push against the diaphragm
Pleural pressure becomes POSITIVE
Alveolar pressure is POSITIVE
The airway has a spot where outside pressure is greater than in it, so DYNAMIC COMPRESSION occurs.
Normally C cartilage keeps airway open but in emphysema this is a major issue.
What explains why dynamic compression happens?
Bernoulli Effect- airflow is faster (less pressure) on top of wing
Glottis is closed.
Uniform P1 everywhere.
Open glottis, airflow is faster in the airway, making pressure lower there. When people forcefully exhale, they are increasing velocity even more in the airway, making a lower pressure there. This is more susceptible to dynamic collapse.
What do alveoli tend to do in the lung?
When are they likely to not present this way?
Tether together to neighbors.
Emphysema causes a loss of tethering. If not connected, they can collapse easier.
Tidal Volume
Volume inspired or expired with each breath
Dead Space Volume
1st 17 gen NOT used in gas exchange (nose,pharynx, trachea)
Residual Volume
Amount of air in lungs that can’t be exhaled/pushed out
Total Lung capacity
Volume of air in lungs after a maximal inspiration effort
Forced Vital Capacity (FVC)
Amount of air that can be exhaled quickly during a forced exhalation.
How do you measure FRC in a normal person?
A person with emphysema?
Helium dilution technique
Body box plehysmography
What influences FRC? (5 things)
Body position
- Upright- increased FRC
- Supine- decreased FRC (guts on diaphragm)
Age -Increase of compliance leads to more air in lung which means increased FRC
Obesity/Pregnancy -decrease FRC (push on diaphragm)
Lobe of Lung removed -decreased FRC (less volume)
Emphysema -Higher FRC due to air pockets in lungs (barrel chest)
Functional Residual Capacity (FRC)
Volume of air in lung when chest wall and lung have equal recoil
What are the obstructive diseases?
What are these characterized by?
- Emphysema
- Asthma
- Bronchitis
- Cystic Fibrosis
- COPD
High airway resistance
What are the restrictive diseases?
What are these characterized by?
- Pulmonary Fibrosis
- Sarcoidosis Silicosis
- Asbestosis Wegner’s
- Granulomatosis
Stiff lung, high lung recoil
What is FEV1? What does this correspond to?
The amount of air exhaled in 1 second of forced exhalation. This is typically >80% of FVC.
If this number is abnormally low, it is indicative of an obstructive pulmonary disease. This shows the person has a high airway resistance.
How do we normalize FEV1 values? What do they indicate?
FEV/FVC
Lower value, Obstructive.
Higher value, Restrictive.
How does the volume/flow graph change with emphysema?
The volume flow loop shifts to the left, which is toward larger volumes.
Flow rate is much smaller and has a curved inward line.
Obstructive
How does a restrictive disease effect volume//flow loops?
The loop shifts to the right, a smaller volume bc of a stiffer lung.
Compare obstructive vs Restrictive disease appearances on a flow volume graph. Give an example of each disease.
Obstructive have a curved inward slope
Restrictive diseases have a pointed appearance with a steep slope.
Obstructive- emphysema
Restrictive- Sarcoidosis
What does a tumor of the lower trachea effect? (Variable intrathoracic)
It effects expiration.
The graph will have a peak point in the upper flow volume loop
What does a fat deposit/ vocal chord paralysis effect? (Variable extrathoracic)
Inhalation.
The graph is flat on the bottom half of the. Inspiration portion.
How does a fixed tumor or tracheal stenosis in a central airway effect flow volume loops? (Fixed intra or extrathoracic lesion)
It effects both inhalation and exhalation and causes them to be plateaued
How is the methacholine test used?
You do 5 test intervals with increasing metacholine dosage. If the test drops to 20% lower than the original number during the intervals and below 8 mg/mL, the person has hyper reactive airways
What should be similar in the methacholine test?
Baseline and control
