Lecture 1-EXAM 4 (respiratory) Flashcards
what are the reasons why we breath? (3)
O2 goes to electron transport chain to make ATP
In a normal person, what are the volumes of tidal volume, dead space and alveolar ventilation?
- TV: 500ml
- Dead: 150 ml (no gas exchange)
- Alv: 350ml (where gas exchange happens)
What are the factors that affects gas exchange? (3)
- Surface area: alveoli has a lot of SA that is important for exchange
- Respiratory membrane
- Blood supply
Notice: There is a short diffusion distance
As we move down the resp. trees in the lungs, what happens to the diameter, cilia, goblet cells, cartilage and smooth muscle?
Going down the lung braches:
* Decreases in: Diameter (smallest being alveolar sac), cilia (for propeling dust/debris out), cartilage, goblet cells
* Increases in: Smooth muscle (the most being in bronchioles and terminal brochioles)
* Smooth muscle replaces cartilage
What is the size of bronchioles?
0.5-1mm
What muscles are for normal (eupneic) inspiration and expiration?
- Inspiration: External intercostals (elevates ribs 2-12 widen thoracic cavity) and diaphragm (descends and increases depth of thoracic cavity)
- Expiration: no muslces, just the recoil back
What muscles are for FORCED inspiration and expiration?
- Inspiration (SIPS): SCM (elevates sternum), Scalenes (fix or elevate ribs 1-2), pectoralis minor (elevates ribs 3-5), Internal internals, intercartiagionous part (aid in elevating ribs)
- Expiration: Intercostals, interosseous part (depress ribs 1-11 narrow thoracic cavity), Rectus abdominis (depresses lower ribs, pushes diaphragm upward by compressing abdominal organs), external abdominal oblique (same effects as rectus abdominis)
How do to the ribs move in expiration and inspiration?
What are the sequence of events for inspiration?
You need to increase volume to decrease pressure (think about molecules in a small and large container)
What are the sequence of events for expiration?
Increase pressure by decreasing volume
What are the three most important gases in the air? What are their percentages in air?
Nitrogen, O2, CO2
What is the pO2 and pN2?
- pO2: 760mmHg * 21%= 160mmHg
- pN2: 760mmHg * 79% =600mmHg
What are the partial pressures of Po2 and Pco2 when entering alveolar capillaries, alveoli, and leaving alveolar capillaries?
What is the way you can change the air pressures?
Altitudes:
* Higher heights: has less pressure so less Po2
* Lower: more pressure so more Po2
What is the approximate percentage for inhaled and exhaled (N2, CO2, O2, H2O) ?
Nitrogen stays the same because it comes from digestion and not from vent.
O2 decreases in exhalation
CO2: increase in exhalation
Fill in
What prevents the lung and airways to not collapse?
Negative intrapleual pressure
Pressures:
* Atmospheric:
* Intrapleual pressure:
* Intra-alveolar pressure:
* Transpulmonary pressure:
- Atmospheric: 760 mmHg (or 0mmHg)
- Intrapleual pressure: 756 mmHg (or -4 mmHg)
- Intra-alveolar pressure: 760 mmHg (or 0 mmHg)
- Transpulmonary pressure: Palv-Pip = 4 mmHg
What causes the pelural sac negative pressure?
Lungs want to recoil in and chest wall wants to recoil out therefore causing the negative intrapleural pressure (ALLOWS the chest wall and lungs to move together)
If we do not have this, then the lungs will win and cause the lungs to collapse.
What is a pneumothorax? What events lead to this?
Pneumothorax: presence of air in pleual cavity
* Thoracic wall is punctured
* Inspiration sucks air through the wound into the pleural cavity
* Potential space becomes an air-filled cavity
* Loss of negative intrapleural pressure allows lungs to recol and collapse
Atelectasis
Explain the changes in alveolar pressure move air in and out of the lungs
What is the time difference betweeen inspiratory time and expiratory time? What does this difference cause?
- The inspiratory time (TI) is 2 seconds and is less than the expiratory time (TE) of 3 seconds.
- This difference is a result of, in part, a higher airflow resistance during expiration, as is reflected by a higher alveolar pressure (PA) change during expiration (1.2 cm H2O) than during inspiration (0.8 cm H2O
An increase in airway resistance will cause what?
decrease the inspiratory time/expiratory time ratio
T/F: Only a small pressure change between the mouth and alveoli is required for a normal tidal volume
True
What ventation values cannot be determined directly by spirometry?
Residual lung volume, FRC, and TLC (since you need RV)
What is pul. emphysema?
What happens when lung recoli forces decreases?
- Pulmonary emphysema is characterized by a destruction of elastic tissue in the lung, which causes a lower lung recoil force.
- When lung recoil forces decrease, as in emphysema, chest wall expansion forces predominate, the chest wall expands outward pulling the lung with it.
- A new equilibrium occurs at increased lung volume so what increases?
- The RV is increased in emphysema because why?
- When a person with emphysema tries to exhale completely, what happens?
- Increased FRC = _ ; Increased RV = _
- A new equilibrium occurs at increased lung volume so the FRC is increased.
- The RV is increased in emphysema because the VC is decreased because of small airway obstruction.
- When a person with emphysema tries to exhale completely, his or her bronchioles collapse, trapping air in the lungs.
- Increased FRC = hyperinflation; Increased RV = air trapping.
*
What is the minute ventilation equation?
What happens when not all of the inspired air reaches the alveloi? Give examples
not all of the inspired air reaches the alveloi will become wasted air
* Some of the air in the tidal volume does not participate in gas exchange.The volume of air in the conducting airways does not participate in gas exchange and constitutes dead space volume (VD)
* Total wasted air in the lungs is computed from the physiologic dead space volume. Dead space volume occurs in the conducting airways and in alveoli with poor capillary circulation. For A, There is no blood flow to an alveolar region. For B, There is reduced blood flow. In both cases, a portion of alveolar air does not participate in gas exchange and constitutes alveolar dead space volume.
What is the alveolar ventilation per minute equation?
How is alveolar ventilation determined?
By measuring the patient’s volume of expired CO2
If alv. ventilation is halved, the PCO2 is what? This is called what?
- If alv. vent is halved, arterial PCO2 will double (assuming a steady-state and constant carbon dioxide production)
- This decrease in alv vent below normal is called hypoventilation
What happens with PaCO2 when you increase ventilation? What is this called?
- If alv. vent is increased, arterial PCO2 will fall (assuming a steady-state and constant carbon dioxide production)
- This increase in alv vent below normal is called hyperventilation
What is the difference in hypernea and hyperventation?
- hypernea: by metabolic processes
- hyperventation: not metabolic
- What directly affects inflation and deflation of the lungs?
- What is distensibility?
- What is elatic recoil?
- Elastic recoil of lungs
- Distensibility - ease with which the lungs can be stretched or inflated.
- Elastic recoil - ability of a stretched or inflated lung to return to its resting volume (FRC).
- What does lung compliance measure? (provide equation)
- What happens with increase and decrease compliance?
How does obstructive and restrictive diseases alter lung compliance?
- Blue line: obstructive
- Doted black: restrictive
Difference in regional lung compliance causes what? Explain
Causes uneven ventilation
* look at picture to understand the difference of apex and base with ventilation
- As a result of gravity, where is ventilation higher? (when standing)
- Why?
- As a result of gravity, ventilation is higher at the base of the lung
- Alveoli are smaller at the base of the upright lung than at the apex dt the weight of the lung compressing alveoli at the base.
- When the lung is at FRC, the smaller alveoli at the base of the lung have optimal compliance and are more easily ventilated; alveoli at the apex have a high resting volume and are more difficult to ventilate due to lower compliance.
- Basal alveoli also have a larger range of volume through which they can expand during inspiration.
What does surfactant do?
Lowers surface tension and stabilizes alveoli at low lung volumes
Where is surfactant more concentrated? What happens when there is no surfactant in alveoli?
- Surfactant lowers surface tension proportionately more in the smaller alveolus. As a result, pressures in the two alveoli are equal, and alveoli of different diameters can coexist
- Pressure in the smaller alveolus is greater than that in the larger alveolus, which causes air from the smaller alveolus to empty into the larger alveolus. At low lung volumes, the smaller alveoli tend to collapse, a phenomenon known as atelectasis.
What happens when you increase surfactant?
- Increased surfactant = compliance
- Increased compliance = increased volume at a given pressure
- What allows for distribution of pressure in alveoli?
- What cell reduce surface tension?
- What cell is the squamous epithelial cell?
- Alveolar pores
- Type 2
- Type 1
- The height of the column of mercury that is supported by air pressure decreases with altitude, which is a result of a fall in barometric pressure (PB).
- Because the fractional concentration of inspired O2 (FIO2) does not change with altitude, the decrease in PO2 with altitude is caused entirely by a decrease in PB.
- How does oxygen and Co2 move across the alveolar-cap membrane?
- What are the factors that are affecting gas exchange?
- Diffusion
- Factors affecting gas exchange: Surface area, Respiratory membrane, Blood supply
When is partial pressure of oxygen (PO2) is highest when and carbon dioxide (PCO2) is highest when?
Partial pressure of oxygen (PO2) is highest when it leaves the lungs, and that of carbon dioxide (PCO2) is highest when it enters the lungs
Blood hematocrit and pulmonary capillary blood volume affect what?
lung diffusing capacity for oxygen
- What is lung diffusing capacity?
- What does it not depend solely on?
- What is it affected by?
- Lung diffusing capacity (DL) is a measure of the lung’s ability to transfer gases.
- Diffusing capacity (DL) does not depend solely on the diffusion properties of the lungs
- it is also affected by blood hematocrit and pulmonary capillary blood volume.
Both the hematocrit and capillary blood volume affect lung diffusing capacity how? What is an example?
- DL in the same direction (i.e., a decrease in either the hematocrit or capillary blood volume will decrease the diffusing capacity in otherwise normal lung)
- For example, if two people have the same pulmonary diffusion properties but one is anemic (reduced hematocrit), the anemic person will have a decreased lung diffusing capacity.
An abnormally low cardiac output lowers what? What this cause in return?
An abnormally low cardiac output lowers the pulmonary capillary blood volume, which decreases the alveolar capillary surface area and will, in turn, decrease the diffusing capacity in otherwise normal lungs.
- Pulmoney blood flow increase what?
- trasnsient time is not what?
- Pulmonary blood flow increases oxygen uptake.
- Transient time is not a diffusion limiting factor for O2 or CO2 in humans, even at high CO (exercise)
Notes
- Gas transfer across the alveolar–capillary membrane is affected by what?
- The average transit time it takes blood to pass through the pulmonary capillaries is what?
- The profile for oxygen is more like that of N2O, which means oxygen transfer is limited primarily by what?
- Pulmonary capillary PO2 equilibrates with what?
- Gas transfer across the alveolar–capillary membrane is affected by pulmonary capillary blood flow
- 0.75 seconds
- The profile for oxygen is more like that of N2O, which means oxygen transfer is limited primarily by blood flow
- Pulmonary capillary PO2 equilibrates with the alveolar PO2 in about 0.25 seconds (arrow).
How is O2 transported?
- 98.5% bound to hemoglobin
- 1.5% dissolved in plasma
Arterial blood carries about _ of O2 per deciliter
20ml
What is hemoglobin?
molecule specialized for oxygen transport
Four protein (globin) portions
- What does each heme group have
- One hemoglobin molecule can carry up to how many O2? 100% vs 50% saturation?
Each with a heme group that binds one 𝑶2 to an iron atom
One hemoglobin molecule can carry up to 4 O2
* 100% saturation Hb with 4 𝑶𝟐 molecules per Hb
* 50% saturation Hb with 2 𝑶𝟐 molecules per Hb
What is oxyhemoglobin and deoxyhemoglobin?
- Oxyhemoglobin:O2 bound to hemoglobin
- Deoxyhemoglobin: hemoglobin with no O2
- Oxyhemoglobin–dissociation curve illustrates what?
- Each hemoglobin molecule can do what?
- Oxyhemoglobin–dissociation curve illustrates the effect that plasma PO2 has on the loading and unloading of oxygen from hemoglobin
- Each hemoglobin molecule can bind four O2 molecules. There is cooperative binding of O2 so that each additional O2 binds more easily, producing the sigmoidal shape of the O2 dissociation curve.
The position of the O2 dissociation curve can shift, affecting what?
affecting the ability to take up O2 at the lung and altering the amount of O2 unloaded from hemoglobin at the tissues
How is the O2 affinity of hemoglobin described?
The O2 affinity of hemoglobin is described using a P50 value (the Po2 resulting in 50% saturation).
- A left shift in the oxyhemoglobin dissociation curve causes what?
- A right shift in the oxyhemoglobin dissociation curve causes what?
- A left shift in the oxyhemoglobin dissociation curve causes hemoglobin to become saturated at lower Po2. Loading O2 into blood at the lung is easier, but it is more difficult to unload O2 at the tissues.
- A right shift in the oxyhemoglobin dissociation curve causes hemoglobin to become saturated at higher Po2. O2 loading at the lungs is reduced and the proportion of hemoglobin saturated with O2 (Sao2) may be reduced, but O2 is unloaded more readily at the tissues.
What are several factors that cause a right shift in the O2 dissociation curve?
- Increased temperature (e.g., exercise). Higher temperature increases O2 unloading in working muscle.
- Increased CO2. High levels of CO2 in metabolically active tissues indicate high O2 demand, and more O2 unloading is needed.
- Increased [H+]. Buffering of H+ by hemoglobin reduces its O2 affinity (known as the Bohr effect). For example, anaerobic metabolism produces lactic acid, indicating that more O2 delivery to tissue is needed.
- Increased concentration of 2,3-bisphosphoglycerate (BPG) in erythrocytes. BPG is an end product of metabolism in erythrocytes. Hypoxemia increases BPG formation, causing more unloading of O2 from hemoglobin.
What are the factors that would cause a left shift in O2 dis. curve?
.
- Most of the carbon dioxide in the blood is transported as what?
- What is the carbonic anhydrase (CA) reaction?
Bicarb
What are all the ways that CO2 can be transported?
Physically dissolved in the plasma (10%)
As bicarbonate ions in the plasma and in the red cells (60%)
As carbamino proteins (30%)
The uptake of CO2 favors what?
the release of O2
What is the chloride shift?
- The reaction mostly occur inside RBCs because CA is abundant there
- In RBCs, CO2 reacts with water of the cytoplasm with the presence of CA to form carbonic acid
- The carbonic acid is a weak acid, which undergoes partial dissociation to yield H+ and bicarb
- The bicarb ion then diffuses outside of the RBC in the plasma and combines with Na ions to form sodium bicarbonate
- The loss of bicarb ions from RBC causes a positive charge inside RBC which is balance by diffusion of Cl ions from the plasma into the RBC
IN SYSTEMIC GAS EXCHANGE
What is the reverse Chloride shift
happens in the pulmonary capillaries
* Oxygen entering the blood (RBC) leads to release of protons
* Increasing protons level causes HCO3- to enter the RBC and in return Cl- is removed from the RBC to maintain electrical neutrality
* HCO3- can combine with the H+ ions from O2 coming in to form Carbonic acid
* Carbonic acid is then broken into CO2 and H2O via Carbonic anhydrase
* CO2 then diffuses out of the capillary and into alv.
The conducting airways have their own what?
separate circulation
- Bronchial circulation distinct and separate from the pulmonary circulation.
Primary function of the bronchial circulation is to what?
Primary function of the bronchial circulation is to nourish the walls of the conducting airways and surrounding tissues by distributing blood to the supporting structures of the lungs
Pulmonary circulation has many secondary functions. List primary and secondary
1 - Gas exchange
2 - Filtering (thrombi), Metabolic organ (ACE), Blood source (10% of total volume)
Systemic venous blood flows through the _ _ into the alveolar capillaries and back to the heart via the _ _, to be pumped into the systemic circulation.
Systemic venous blood flows through the pulmonary arteries into the alveolar capillaries and back to the heart via the pulmonary veins, to be pumped into the systemic circulation.
- Pulmonary circulation is what?
- Pulmonary capillaries are like what?
- Pulmonary circulation is high-flow, low-pressure, low-resistance system, high-compliance, low-smooth muscle.
- Pulmonary capillaries are like sheets over alveoli
Pulmonary vascular resistance falls with what?
Pulmonary vascular resistance falls with increased cardiac output (⬇️Pul R = ⬆️CO)
Pulmonary circulation is characterized as normally _ , whereas the systemic circulation is characterized as normally _
Pulmonary circulation is characterized as normally dilated, whereas the systemic circulation is characterized as normally constricted
- Pulmonary circulation can decrease resistance when?
- When cardiac output increases, what rises and what does that result in?
- Pulmonary circulation can decrease resistance when pulmonary arterial pressure rises.
- Cardiac output increases, pulmonary pressure rises, resulting in a marked decrease in pulmonary vascular resistance.
Two local mechanisms in the pulmonary circulation are responsible for decreases pul vascular resistance:
capillary recruitment and capillary distention.
What happens when there is an increase in CO?
What are the three benefits of decreased resistance?
- Opposes the tendency of blood velocity to speed up with increased flow rate, maintaining adequate time for pulmonary capillary blood to take up oxygen and dispose of carbon dioxide.
- Results in an increase in capillary surface area, which enhances the diffusion of oxygen into and carbon dioxide out of the pulmonary capillary blood.
- Decreases risks of pulmonary edema
What happens with capillary recruitment and capillary distention?
- Capillary recruitment (the opening up of previously closed vessels) results in the perfusion of an increased number of vessels with a concomitant decrease in resistance
- Capillary distention (an increase in the caliber of vessels) resulting from high vessel compliance also results in a lower resistance and higher blood flow.
Pulmonary vascular resistance increases when? Explain
at high and low lung volumes
At low lung volumes, pulmonary vascular resistance increases, as a result of what?
result of more positive pleural pressure, which compresses the extra-alveolar vessels
At high lung volumes alveolar vessels are what? What does this cause?
are compressed, causing a rise in pulmonary vascular resistance.
Fluid movement in and out of capillaries depends on what?
depends on the net difference between hydrostatic and colloidal osmotic pressures. In the lung, two additional factors (alveolar surface tension and pressure) are involved in fluid exchange
Alveolar surface tension enhances _ , whereas alveolar pressure opposes _
Alveolar surface tension enhances filtration, whereas alveolar pressure opposes filtration.
What helps keep the alveoli dry?
The relatively low pulmonary capillary hydrostatic pressure helps keep the alveoli “dry” and prevents pulmonary edema
Surface tension affects fluid exchange
- Pulmonary edema occurs when?
- Increased capillary hydrostatic pressure is the most frequent casue of what?
- The second major cause of pulmonary edema is what?
- Pulmonary edema occurs when excess fluid accumulates in the lung interstitial spaces and alveoli and usually results when capillary filtration exceeds fluid removal.
- Increased capillary hydrostatic pressure is the most frequent cause of pulmonary edema and is often the result of an abnormally high pulmonary venous pressure
- The second major cause of pulmonary edema is noncardiogenic and is due to increased alveolar surface tension and/or increased permeability of the alveolar–capillary membrane
What does gravity causes lungs to be?
Gravity causes lungs to be underperfused at the apex and overperfused at the base.
Zone 3 of lungs?
Arterial and venous pressures both exceed alveolar pressure. Perfusion pressure is the arterial-to-venous pressure difference. Zone 3 represents the areas of the lung with the largest rate of blood flow (i.e., the base of the upright lung).
Zone 2 of lungs?
Alveolar pressure is between arterial and venous pressure. The perfusion pressure in zone 2 is the difference between arterial and alveolar pressure. Vessels are partially constricted, and blood flow is more limited.
Zone 1 of lungs?
Arterial and venous pressures are both less than alveolar pressure, resulting in compression of the pulmonary capillaries and no perfusion. Zone 1 is alveolar dead space, which is ventilated but not perfused.
Gravity causes a mismatch of what?
regional ventilation and blood flow at the base and apex of the lungs
Where is vent/perfusion matching the best matched in lungs?
At the base
Low oxygen tension in the lung causes what?
pulmonary vasoconstriction
- Previously learned that hypoxemia causes what in systemic vessel?
- What is different about pulmonary vessels? What is this called?
- Previously learned that hypoxemia causes vasodilation in systemic vessels.
- However, in pulmonary vessels, hypoxemia or alveolar hypoxia causes vasoconstriction of small pulmonary arteries.
* This unique phenomenon is called hypoxia-induced pulmonary vasoconstriction
- hypoxia-induced pulmonary vasoconstriction is accentuated by what?
- What is the exact mechanism? What can hypoxia stimulate?
- Accentuated by high carbon dioxide and low blood pH
- The exact mechanism is not known, but hypoxia can directly stimulate pulmonary vascular smooth muscle cells, independent of any agonist or neurotransmitter released by hypoxia
What is Regional hypoxia? What does it cause?
Regional hypoxia is vasoconstriction localized to a specific region of the lungs. Diverts blood away from a poorly ventilated region. Often caused by bronchial obstruction. Has little effect on pulmonary arterial pressure, or resistance, and when alveolar hypoxia no longer exists, the vessels dilate and blood flow is restored.
What is generalized hypoxia?
, on the other hand, causes vasoconstriction throughout both lungs, leading to a significant rise in resistance and pulmonary artery pressure
How is ventilation adjusted to changes in perfusion?
How is perfusion adjusted to changes in ventilation?
What is wasted air and blood?
- All of the inspired air does not participate in gas exchange, resulting in some “wasted air.”
- All of the blood entering the lung is not fully oxygenated, leading to some “wasted blood.”
.” The total amount of wasted air constitutes what? What about wasted blood?
The total amount of wasted air constitutes physiologic dead space, and the total amount of wasted blood (venous admixture) constitutes physiologic shunt
Any deviation from the ideal ratio (0.8) impairs what?
gas exchange and lowers oxygen tension in the arterial blood
What are example of wasted blood?
Airway obstruction causes a low regional ventilation/perfusion ratio. A partially blocked airway causes this region to be underventilated relative to blood flow. Note the alveolar gas composition. A low regional ratio causes venous admixture and will increase the physiologic shunt.
What are examples of wasted air?
A partially obstructed pulmonary arteriole (right panel) will cause an abnormally high ratio in a lung region. Restricted blood flow causes this region to be overventilated relative to blood flow, which leads to an increase in physiologic dead space
The respiratory centers are located within what?
pons and medulla
The basic rhythm of breathing is controlled by what?
The medullary center has what?
- The basic rhythm of breathing is controlled by groups of neurons in the medulla.
- The medullary center has a dorsal respiratory group (DRG) of neurons in the nucleus of the tractus solitarius and a ventral respiratory group (VRG) in the nucleus ambiguus and nucleus retroambiguus.
somatic motor neurons= diaphragm with phrenic nerve
The DRG is thought to be what?
The VRG is what?
The DRG is thought to be the main integrator of sensory information and to have primarily inspiratory neurons.
The VRG is larger and has primarily motor neurons that mediate both inspiration and active expiration.
What are J receptors? What are they activated by?
- “juxtaposed” to the pulmonary capillaries
- Activated by physical engorgement of the pulmonary capillaries
Central and peripheral chemoreceptors respond to changes in what?
in arterial blood gases and hydrogen ion concentration
Ventilatory responses to what?
to increasing alveolar CO2 tension are shown with the line, representing the response when alveolar PO2 (PAO2) is held at ≥100 mm Hg to essentially eliminate O2-dependent activity of the chemoreceptors.
The blood–brain barrier is impermeable to what?
to blood H+ and HCO3−.
Because the blood–brain barrier is permeable to CO2 and not to H+ and HCO3−, the acid–base status of the chemoreceptors can be what?
can be quickly changed only by changing PaCO2.
