Lecture 4: Respiratory Flashcards
What is the difference between respiration and ventilation?
Ventilation is the movement of air in and out of the lungs.
Respiration is the exchange of gases.
What is the ventilation perfusion ratio? Where is it high and low?
It is the ratio of alveolar ventilation relative to pulmonary blood flow.
Starting from the top of the lungs, it is high, at 2.1.
In the middle, it goes to 1.
At the bottom of the lungs, it goes to 0.3.
When is the work of breathing? Inspiration or expiration?
Inspiration.
What are the two mechanisms that expand and contract our lungs?
Movement of the ribcage using the intercostal muscles.
Contraction and relaxation of the diaphragm to adjust the chest cavity volume.
What is the key limiting factor for all people in terms of exercise?
It is our cardiometabolic limits, not our lungs.
During NORMAL expiration, what occurs?
Relaxation of the diaphragm.
Elastic recoil of both the lungs and chest wall.
During HEAVY expiration, what occurs?
Relaxation of the diaphragm.
Use of abdominal & intercostal muscles.
During HEAVY inspiration, what occurs?
Contraction of the diaphragm.
Use of external intercostals, sternocleidomastoid, anterior serrati, and scaleni muscles.
What kind of pressure does inspiration generate? What pressure are our lungs at relative to the environment?
Negative pressure. Air is sucked into our lungs because the pressure INSIDE is LOWER than outside.
Inside pressure is 754mm Hg usually.
Why do people with lung disease seem more tired?
Breathing is energy intensive.
Where is the lung attached to the chest wall?
At the hilum from the mediastinum.
Which parietal surface is found directly on the lungs?
Visceral pleural surface lining.
Which pleural surface is found on the thoracic cavity?
Parietal pleural surface lining.
What maintains the suction between the two pleural surfaces?
pleural fluid, which is continually suctioned into the lymphatic channels. It helps create a seal, similar to a drop of water between two glass surfaces.
What does pleural pressure usually measure at?
Between -5 to -7.5 cm H2O.
During inspiration, what occurs to alveolar pressure?
It falls by approximately 1cm H2O.
What does the change in alveolar pressure during inspiration cause?
Negative pressure, usually sucking in 500 mL of air into the lungs, AKA our tidal volume.
During expiration, what occurs to alveolar pressure?
It increases by approximately 1cm H2O back to its original pressure.
What is trans-pulmonary pressure? How do I measure it?
Difference between alveolar pressure and pleural pressure.
What is recoil pressure?
It is a measure of the elastic forces in our lungs that collapse our lungs at the end of inspiration.
What two fibers make up the elasticity of our lung?
Elastin and Collagen.
What happens to our lung fibers as our lung expands?
They start stretching and unkinking, exerting the elastic force that makes expiration easy relative to inspiration.
What does poor lung compliance mean?
It means our lungs are stiff, so it requires more effort INSPIRING to generate the elastic force that makes expiration easy.
In other words, people with poor lung compliance have difficulty INSPIRING.
What two mechanisms determine our lung’s elastic force?
The lung fibers themselves (elastin and collagen)
Surface tension within the alveoli.
Which mechanism generates most of the elastic recoil in expiration?
Surface tension = 2/3.
The elastic force due to tissues (elastin and collagen) are responsible for only 1/3.
Why do we care that alveolar fluid interacts with air instead of more water?
The surface tension is generated when air meets water. The water has a stronger attraction for other water molecules if it meets air.
Clinical Question: What is a pneumothorax and the two kinds?
Pneumothorax: Collection of air in the chest OUTSIDE of the lung, causing lung collapse.
Primary pneumothorax: Occurs without apparent cause in the absence of lung disease.
Secondary pneumothorax: Occurs in the presence of existing lung pathology.
Special: A tension pneumothorax is created via one-way valves made from an area of damaged tissue, so the lungs slowly get squeezed. Leads to decreasing spo2 and low BP.
What makes surfactant in the lungs? What is surfactant?
Type II alveolar epithelial cells.
Surfactant is an agent that reduces the surface tension of water.
Note: laundry detergent is also a type of surfactant.
When do babies start making surfactant?
6-7 months of gestation, or 24-28 week which is when their type II alveolar epithelial cells develop.
Note: A baby’s lungs are usually fully developed around 32-36 weeks.
What is the key differences between a restrictive lung disease and an obstructive lung disease?
Restrictive lung diseases show reductions in all lung capacity measurements, such as VC, FRC, TLC, and FVC.
Obstructive lung diseases show a marked decrease in the ability to expire.
Name some restrictive lung diseases.
Idiopathic pulmonary fibrosis (IPF)
Non-specific interstitial pneumonia (NSIP)
Cryptogenic organizing pneumonia (COP)
Sarcoidosis
Acute interstitial pneumonia (AIP)
Name some common obstructive lung diseases.
Emphysema
Asthma
Chronic bronchitis
Note: COPD refers to most of the obstructive diseases. Also, these are all NON-reversable.
What disease do I commonly see barrel chest in?
Emphysema
What is the average tidal volume? (In terms of what we learned class-wise)
500 mL
What do capacity measurements include that reserve volumes do not for lung measurements?
Any reserve volume measurement does NOT include tidal volume.
Any capacity is a combination of 2 or more things.
Example: Functional vital capacity is the addition of Inspiratory reserve volume (IRV) + Tidal Volume (TV) + Expiratory reserve volume (ERV)
What is minute ventilation? The normal average?
The volume of air we breathe in one minute.
It is normally 6L, which is 12 breaths/min X 500 mL/breath. AKA breathing rate x tidal volume.
How much dead space is in our tidal volume?
150mL
What two things make up dead space?
Anatomic dead space and physiologic dead space.
Anatomic dead space = trachea and the parts of the airway that are not alveoli.
Physiologic dead space = the parts of the alveoli that do not get air every breath.
What is the main disadvantage with shallow breathing relative to minute ventilation?
Overventilation of the dead space.
Shallow breathing with high respiratory rate commonly does not exceed the dead space, since our tidal volume is decreased per breath.
What are the main disadvantages with deep breathing in regards to minute ventilation?
Tiring of the intercostal muscles.
Inadequate exhalation of CO2.
How do we measure alveolar minute ventilation?
It is the difference between our total minute ventilation and our dead space minute ventilation.
Clinical: How do we check if someone has an obstructive lung disease? What do we measure, and at what point is it clinically significant?
We measure FEV1/FVC, which is the forced expiratory volume in 1 second divided by the functional vital capacity. In other words, it is how much I can exhale in a single second relative to my total lung capacity - the dead space in my lungs.
Example: My Predicted FEV1 is 4L. My actual FEV1 is 3L. I would say that I am at 75% of predicted.
Ideally, we want 80%, but if you go down to 60%, then we consider that concerning.
Note: Asthma is one of the few reversible lung diseases, whereas chronic ones are not.
What kind of rings does my trachea have? Why?
Cartilage, to help prevent collapse.
What is a key difference between my bronchi and trachea?
My bronchi have LESS cartilage, therefore they can expand and contract more.
What keeps my bronchioles expanded?
Rigidity of their walls + transplumonary pressure. This is the same pressure that also keeps alveoli expanded.
Why are bronchi and bronchioles the site of narrowing in obstructive lung diseases?
They are mainly made of smooth muscle, which contracts. The obstructive lung diseases can cause excessive contraction.
When does the conducting zone end?
After the 16th division within the bronchioles.
When does the respiratory zone begin?
At the 17th division within the bronchioles, where alveoli start appearing on the bronchioles.
Clinical: What is significant about the respiratory zone in regards to particulates?
Air moves very slowly in this zone, so particulates tend to just settle here and stay. This is the reason things like coal dust or asbestos can cause gradual lung symptoms.
Where is the resistance to air flow the greatest?
Large bronchioles and bronchi.
What contributes to air flow resistance the most when we are diseased?
Smaller bronchioles contribute the most because they are easily occluded by muscle contractions in their wall or edema in their walls or mucus in their lumens.
What does sympathetic stimulation of the lungs cause? Main NT responsible?
Bronchial dilation via both NE and epi but MAINLY epi.
Note: Epi has greater stimulation of BETA adrenergic receptors. In case it gets confusing, we use epi pens when someone has anaphylaxis, not norepi. Epi will dilate our lungs, whereas norepi will not.
What does parasympathetic stimulation of the lungs cause? Main NT responsible?
Bronchial constriction via Ach, which cause mild to moderate constriction, but if someone has constriction already, it can worsen it.
Note: We use atropine to block Ach in these sorts of cases.
What kind of cells line our airways that are involved in inflammation? What do they release and when?
Mast cells.
Releases histamine and SRS-A (slow reacting substance of anaphylaxis, aka a trio of leukotrienes!)
They release these in allergies, pollen, allergic asthma, sudden cooling/drying of the airways.
What is the pulmonary circulation that contains oxygenated blood?
It is the high pressure, low flow circulation originating from the aorta. Supplies the lungs with blood via the bronchial arteries off the thoracic aorta.
Note: Less pressure than aortic pressure.
How does blood from the lungs reenter the heart? Where does it reenter?
Blood from the lungs to the heart via the pulmonary veins, which enter at the left atrium.
What is the pulmonary circulation that contains deoxygenated blood?
It is the low pressure, high flow circulation originating from the pulmonary artery heading to the lungs. Deoxygenated blood goes via the pulmonary artery to the arterial branches to the alveolar capillaries, where CO2 is removed and O2 is added. It then goes to the pulmonary veins back to the left atrium.
Describe the location of the pulmonary artery.
5cm beyond the base of the RV, sitting under the arch of the aorta.
