pulmonary Flashcards
What muscles control expiration?
Expiration is largely passive.
Simply by relaxing, the chest springs back into shape, and expiration can occur without any muscle action.
One can, however, voluntarily exhale forcefully using: external and internal intercostal muscles, the transversus thoracis and innermost intercostal muscles, external oblique, internal oblique and transversus abdominis muscles.
What is the main muscle that controls inspiration? And what are the accessory muscles?
The main muscle is the diaphragm. Contraction and downward motion of the diaphragm causes a (-) pressure in the chest, which draws in air.
The accessory muscles of inspiration: pectoralis major and minor, serratus anterior, sternocleidomastoid, scalene muscles, levatores costarum, serratus posterior superior
How doe Hgb affect gas exchange?
Oxygen is not very soluble in plasma. Most oxygen (about 97% of it) is transported via hemoglobin, which has special oxygen-binding capabilities. It binds to significant quantities of O2 at the alveolar level, even when O2 conc in the alveoli is relatively low. It also releases O2 easily at the tissue level, but in just the right amounts, since too much can cause oxygen toxicity, and too little will not provide enough for the respiratory needs of the tissue. It also releases large quantities of O2 when the tissues really need it.
But how can hemoglobin bind well to oxygen in the alveoli, yet release it easily at the peripheral tissue level?
Oxygen dissociation curve for hemoglobin.
Hgb maintains near saturation (above 90% saturated) even when alveolar O2 decreases from the normal 104mm Hg to 60mm Hg. However, when Hgb encounters the low tissue p02 of the body tissues (normally about 40 mm Hg in interstitial fluid), it readily gives up the oxygen.
How does CO2 leaves the body?
CO2 combines with H2O in RBC forming H2CO3.
The H ion from H2CO3 binds with Hgb forming HCO3.
HCO3 leaves the cell, float around the bld until it reaches the lungs.
Hgb releases the H, it combines with HCO3 to form back to H2O and CO2.
CO2 then is expelled by the lungs.
Some CO2 does combine directly to Hgb forming CARBINOHEMOGLOBIN, which releases its CO2 in the lungs
There is greater release of oxygen by Hgb when..
In terms of pO2, pCO2, pH, temp
<60mm Hg pO2, high pCO2, low pH, and high temp.
What is the rate limiting step in the cell’s oxygen utilization?
Level of ADP.
What neural factors control respiration?
Phrenic nerves (C3,4,5) innervates diaphragm and receives voluntary and involuntary message from respiratory centers (medulla and pons)
CO2 and Water forms what pH in blood?
Weak acids
A slight increase of this pressure potential stimulates the respiration.
PCO2
A moderate increase of pCO2 stimulates respiration much more than does a moderate decrease in p02. So why do we need the O2 response mechanism? Wouldn’t it suffice to just have the pCO2 control mechanism?
In severe pulmonary disease, in which there is poor exchange in both O2 and CO2, the CO2 effect is not enough. The large drop in pO2 then comes into play, having a marked effect in increasing the rate of respiration when the pO2 falls to the 30-60 mm Hg range.
Then why do we need the CO2 control mechanism? Why does it not suffice to just control respiration according to the O2 level? After all, isn’t it really the O2 that the body needs? Shouldn’t 02 levels alone provide the best feedback control?
CO2 control mechanism is actually needed more for the control of blood pH than for control of respiration. Subtle changes in the pC02 can significantly affect pH, so the body needs the fine CO2 control mechanism to control CO2 levels and thus control pH.
Breathing high-pressure oxygen (above atmospheric pressure) can markedly increase the saturation of O2 in the blood, even to toxic levels, not by increased uptake by hemoglobin, but by…
dissolving more of oxygen in plasma.
What do you need to do if you want to increase tissue oxygenation?
Increase the O2 conc in the air being breathed, the Hgb conc, or the blood flow ( as by increasing the CO). Hyperventilation is not good enough.
In diving, the alveolar pressure rises to meet the increasing atmospheric pressure that results with greater depth. The higher pressure causes more N2 to be dissolved, which may cause N2 toxicity. O2 toxicity may also occur.
On rising from a dive, it is important that the diver gradually let out air. otherwise, the lungs will continue to expand against the decreasing outside envi. pressure, thereby causing lung injury.
Normal air outside the body consists about how many percent of 02, N2, CO2 and water?
20% O2
79% N2
0.04% CO2
<1% water
At high altitude, as in low altitudes, the alveolar pressure in normal breathing cannot be more than the atmospheric pressure.
The body’s long range compensation to high altitude may occur initially through hyperventilation, and over weeks to months, through increased tissue vascularity and increased numbers of RBC.
Between CO2 and O2, which of these is more soluble in air and blood?
CO2
What is the normal arterial pO2 level?
95mm Hg
What is the normal arterial pCO2?
40mm Hg
Normal pO2 in peripheral intracellular level
23mm Hg. But not to worry, the cell needs a pO2 of only about 2mm Hg for adequate functioning
It is the amt of air normally inhaled or exhaled with each average breath like the steady tides going in and out.
Tidal volume
What is normal amt of TV?
500 ml
It is the extra amt you could have inhaled after breathing in normally.
Inspiratory reserve volume.
It is the extra amt you could have exhaled after exhaling normally.
Expiratory reserve volume
It is the residual left in the lungs after the strongest expiration.
Residual volume.
If you didn’t have a RV, there would be marked fluctuations in CO2 and O2 content of blood passing thru the lungs during respirations.
It is the amt of air exchanged from the maximal intake to the most forceful expiration.
Vital capacity
VC = ERV + TV + IRV
It is the increase in chest volume with each degree of increase of alveolar pressure.
Compliance.
The greater the increase in lung volume with a given increase in alveolar pressure, the greater the compliance
It refers to the tendency of the respiratory system to spring back to its original shape after expansion. It it simple the reciprocal of compliance.
Elastance.
The greater the elastance, the greater tendency to rebound, the greater the rise in pressure that results from an increase in lung volume.
Functional residual capacity (FRC) = RV + ERV
Inspiratory capacity (IC) = TV + IRV
For the lung, elastance is partly due to elastic tissues in the lungs, but mainly due to…
Surface tension produced by the fluid coating the alveoli (surfactant) which tends to release the resist expansion. Surface tension is normally kept at a reduced level by surfactant
It is the total amount if air in the lung after a forceful inspiration.
Total lung capacity.
TLC = VC + RV
VC and rate of expulsion is (high, low) in restrictive lung disease and airway obstructive disease.
What is an important distinction between these two?
RV is low in restrictive lung disease while it is high in airway obstructive disease.
Another difference is the FRC, wherein it is low in restrictive lung disease, and high in airway obstructive disease.
Which is more difficult (inspiration or expiration) in airway obstructive disease (eg. Asthma, bronchitis, emphysema)?
Expiration. The positive pressure of expiration collapses the respiratory passages.
Which is more difficult (inspiration or expiration) in fixed airway obstruction?
Both
Which is more difficult (inspiration or expiration) in upper airway ( extrapulmo) obstruction?
Inspiration. The negative pressure of inspiration is transmitted thru bronchi and trachea to cause constriction of areas higher up
Oxygen therapy (e.g. using an oxygen tent, face mask or nasal cannula) may be useful in hypoxia secondary to poor atmosphere oxygenation or to poor pulmonary gas exchange from lung disease.
Oxygen administration may help, though, in carbon monoxide poisoning. Carbon monoxide (CO) binds more strongly than does O2 to the same site on the hemoglobin molecule, in effect reducing the number of available RBCs.
When the patient cannot breathe or the effort of breathing becomes too much for the patient, it may be necessary to use a mechanical ventilator. Te ventilator is a positive pressure device.
Normally, inspiration occurs because the chest expansion creates a negative pressure in the alveoli, which results in the influx of air from the atmosphere outside the patient, where the pressure is greater.
Normal quiet breathing is accomplished almost entirely by movement of the diaphragm.
During heavy breathing, extra force is needed achieved mainly by contraction of abdominal muscles, which pushes the abdominal contents upward against the diaphragm, thereby compressing the lungs.
Muscles for inspiration
Diaphragm Scalene muscles Sternocleidomastoid External intercostalis Serrated anterior
Muscles of expiration
Internal intercostalis
Rectus a dominos
It is the pressure of the fluid in the thin space between the lung pleura and the chest wall pleura.
Pleural pressure.
Pleural pressure at the beginning of inspiration
-5 cm H2O
Pleural pressure during inspiration
-7.5cm H2O
It is the pressure of the air inside the lung alveoli.
Alveolar pressure.
If there is no pulmo respiration, the alveolar pressure is zero references pressure in the airways, that is, 0 cm H2O. How about during inspiration?
-1 cm H2O
Alveolar pressure during expiration
+2 cm H2O
It is the pressure difference between the alveolar pressure and the pleural pressure and it is the measure of recoil pressure.
Transpulmonary pressure
It is the elastic forces in the lungs that tends to collapse the lungs at each instant of respiration, or it is the pressure generated at a given lung volume.
Elastic recoil pressure
It is the extent to which he lungs will expand for each unit increase in transpulmonary pressure.
Lung compliance
The normal lung compliance
200ml / cm H2O
True or false: the tissue elastic forces tending to cause collapse of the air-filled lung represent two-thirds of the total lung elasticity, whereas the fluid-air surface tension forces in the alveoli represent about one-third.
False. the tissue elastic forces tending to cause collapse of the air-filled lung represent only about ONE-THIRD of the total lung elasticity, whereas the fluid-air surface tension forces in the alveoli represent about TWO-THIRDS.
A phenomenon where in water surface is attempting to contract. This results in an attempt to force air out of the alveoli thru the bronchi and, in doing so, causes the alveoli to try to collapse.
Surface tension
What is the effect of surfactant on surface tension?
Surfactant is a surface active agent in water, which means that it greatly reduces surface tension. It is secreted by type2 alveolar epith cells which are granular.
What component of surfactant is responsible for reducing the surface tension
Dipalmitoylphosphatidylcholine
True or false: A positive pressure in the alveoli attempts to push the air out.
True.
Surfactants are normally begin to be secreted into the alveoli between what months of gestation?
6-7 mos
What is the compliance of the combine lung-thorax system?
110 ml / cm H2O.
Spirometers is a simple method for studying pulmonary ventilation by recording the volume movement of air into and out of the lungs. What lung vol and capacity can the spirometer measure? And cannot?
Spirometry measures TV, IRV, ERV, IC and VC.
It can’t measure RV, FRC and TLC (because pt can’t expire all the air in his/her lungs)
It is the volume of air inspired or expired with each normal breath
Tidal volume
What is the normal amt of TV?
500ml
It is the extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force.
Inspiratory reserve volume
What is the usual Amt of IRV?
3000ml
It is the maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration.
Expiratory reserve volume
What is the usual amt of ERV?
1100ml
It is the volume of air remaining in the lungs after the most forceful expiration.
Residual volume
What it the usual amt of RV?
1200ml
This is the amount of air (about 3500 milliliters) a person can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount.
Inspiratory capacity. The inspiratory capacity equals the tidal volume plus the inspiratory reserve volume.
This is the amount of air that remains in the lungs at the end of normal expiration (about 2300 milliliters).
Functional residual capacity. It is equals the expiratory reserve volume plus the residual volume.
This is the maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent (about 4600 milliliters).
The vital capacity equals the inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume.
It is the maximum volume to which the lungs can be expanded with the greatest possible effort (about 5800 milliliters); it is equal to the vital capacity plus the residual volume.
Total lung capacity
It is the total amount of new air moved into the respiratory passages each minute; this is equal to the tidal volume times the respiratory rate per minute.
Minute respiratory volume.
What is the normal MRV?
MRV = RR x TV; 12beats x 500ml = 6L/min
A person can live for a short period with a minute respiratory volume as low as ____ L/min and a respiratory rate of only ____ breaths per minute.
as low as 1.5 L/min and a respiratory rate of only 2 to 4 breaths per minute.
The ultimate importance of pulmonary ventilation is …
to continually renew the air in the gas exchange areas of the lungs, where air is in proximity to the pulmonary blood.
True or false: On expiration, the air in the dead space is expired first, before any of the air from the alveoli reaches the atmosphere.
True. Therefore, the dead space is very disadvantageous for removing the expiratory gases from the lungs.
Normal dead space volume.
150ml. This increases slightly with Age.
Rate of alveolar ventilation
12 beats/min x 500ml TV x 150ml dead space = 4200ml/min
True or false: cartilage rings are already gone in later generations of bronchi.
False. They are gone in the bronchioles.
What is the effect of sympathetic release of norepinephrine and epinephrine on the lungs?
Dilation of bronchial tree
What is the effect of parasympathetic release of acetylcholine on the lungs?
Constriction of bronchioles
Local secretory factories that often cause bronchiolar constriction.
Histamine and slow reactive substance of anaphylaxis. Both of these are released in lung tissue by mast cells during allergic reactions.
The direction of the power stroke of cilia in respiratory passageways is always…
Towards the pharynx. That is, the cilia in the lungs beat upward, whereas those in the nose beat downward.
The difference between cough reflex and sneeze reflex.
The initiating stimulus of sneeze reflex is irritation in nasal passageways while cough reflex is in bronchi and trachea.
The afferent impulses of sneeze reflex pass in 5th cranial nerve to medulla, while cough reflex impulse pass in vagus nerve.
The automatic sequence events of sneeze and cough reflex is triggered by the neuronal circuits of the medulla, causing the following effect:
- Up to 2.5 L of air is rapidly inspired
- Epiglottis closes and vocal cords shut tightly to entrap air within the lungs
- Expiratory muscles contract forcefully, thus pressure in lungs rises rapidly to as much as 100mm Hg
- Vocal cords and epiglottis suddenly open widely, causing air in lungs to explode outward.
The air conditioning functions of the nose
Air is warmed, humidified and filtered
What are the obstructing vanes that the air hits causing removal of particles by turbulent precipitation?
Conchae (Turbinates), septum and pharyngeal wall
Size of particles entrapped in nose.
6 micrometer
Size of particles entrapped in smaller bronchioles
1-5 micrometers
Size of particles suspended in alveolar air and are expelled by expiration.
0.5 micrometer. For instance, the particles of cigarette smoke is 0.3 micrometer.
3 major organs of articulation
Lips, tongue and soft palate
3 Organs that are resonators
Mouth, nose and asso nasal sinuses, and pharynx
The pulmonary artery extends only about how many cm beyond the apex of R ventricle and then divides into L and R main branches that supply blood to 2 respective lungs.
5cm
True or false: pulmonary artery has low compliance.
False. It has large compliance which allows the pulmonary arteries to accommodate the stroke volume output of the R ventricle
True or false: the bronchial arterial tree is oxygenated blood.
True. It supplies the supporting tissues of the lungs, including the ct, septa and large and small bronchi. It empties to pulmonary veins and enters the L atrium rather than passing back to R atrium.
Blood volume of the lungs
450 ml, about 9% of the total bld vol of the entire circulatory system.
Lungs is considered as a blood reservoir. Under various physiological and pathological conditions, the quantity of blood in the lungs can vary from as little as one half normal up to twice normal.
For instance, when a person blows out air so hard that high pressure is built up in the lungs— such as when blowing a trumpet—as much as 250 ml of blood can be expelled from the pulmonary circulatory system into the systemic circulation. Also, loss of blood from the systemic circulation by hemorrhage can be partly compensated for by the automatic shift of blood from the lungs into the systemic vessels.
What is the effect if diminished alveolar oxygen on local alveolar blood flow?
When the conc of O2 in the air of alveoli decreases below normal, the adjacent bld vessels constrict (opposite to the effect observed in systemic vessels, which dilates in response to low O2)
The effect of low oxygen on pulmonary vascular resistance (bv constriction) has an important function…
To distribute blood flow where it is most effective.
That is, if some alveoli are poorly ventilated so that their O2 conc becomes low, the local vessels constrict. This causes the blood to flow through other areas of the lungs that are better aerated, thus providing an automatic control system for distributing blood flow to the pulmonary areas in proportion to their alveolar oxygen pressures.
True or false: any time the lung alveolar air pressure becomes greater than the capillary blood pressure, the capillaries close and there is no blood flow.
True
Under different normal and pathological lung conditions, one may find any one of three possible zones of pulmonary blood flow.
It is the zone where in the local alveolar capillary pressure in that area of the lung never rises higher than the alveolar air pressure during any part of the cardiac cycle
Zone 1: no blood flow during all portions of the cardiac cycle
It is the zone where the pulmonary arterial pressure peaks because the systolic pressure is then greater than the alveolar air pressure, but the diastolic pressure is less than the alveolar air pressure
Zone 2: intermittent blood flow
It is the zone where in the alveolar capillary pressure remains greater than alveolar air pressure during the entire cardiac cycle
Zone 3: continuous blood flow
Normally, the lungs have only zones 2 and 3 blood flow. Zone 2 in the apices and zone 3 in all lower areas.
Zone 1 blood flow occurs only under abnormal conditions.
The mean left atrial pressure
2mm Hg
Mean pulmonary arterial pressure
15mm Hg
Mean pulmonary capillary pressure
7mm Hg. In contrast to the peripheral capillary pressure of about 17mm Hg.
the interstitial fluid pressure in the lung is slightly more negative that that in the peripheral subcutaneous tissue.
The pulmonary capillaries are relatively leaky to protein molecules, so that the colloid osmotic pressure of pulmonary interstitial fluid is 14mm Hg
Forces tending to cause the movement of fluid outward form the capillaries and into the pulmonary interstitium:
Capillary pressure: 7
Interstitial fluid colloid osmotic pressure: 14
Negative interstitial fluid pressure: 8
TOTAL OUTWARD FORCE: 29mm Hg
Forces tending to cause absorption of fluid into the capillaries
Plasma colloid osmotic pressure: 28
TOTAL INWARD FORCE: 28mm Hg
Why alveoli do not normally fill with fluid?
The pulmonary capillaries and the pulmonary lymphatic system normally maintain a slight negative pressure in the interstitial spaces, it is clear that whenever extra fluid appears in the alveoli, it will simply be sucked mechanically into the lung interstitium through the small openings between the alveolar epithelial cells. Then the excess fluid is either carried away through the pulmonary lymphatics or absorbed into the pulmonary capillaries.
