Respiratory Flashcards
The lung is suitable for gas exchange because ….. & …..
- Large surface area (70 square meter, about 40 times the surface area of the body)
- Blood-gas barrier is thin (less than 0.5 micro meter)
The blood gas barrier is composed of …. , ….. & …..
alveolar epithelium, basement membrane, capillary endothelium
The conducting zone of the lung is ….., …., ….. & ….. . This is also called …..
trachea, bronchi, bronchioles & terminal bronchioles
* called anatomic dead space (volume is about 150 mL)
The respiratory zone has a volume of … , and consists of …., …. & ….
3000 mL
respiratory bronchiole, alveolar duct, alveolar sacs
There are about …… alveoli in both lungs
300 million
Alveolar sacs are ….. at the end of
blind pouches, terminal bronchiole
Air travels in the conducting zone via …. due to …..
bulk flow
small cross section
Define:
- Vt
- IRV
- ERV
- RV
- amount inspired and expired with every normal breath (about 500mL)
- The extra volume that can be inspired over the Vt
- The extra volume that can still be expired beyond Vt
- The volume remaining after maximal expiration
Define:
- TLC
- VC
- FRC
- IC
- maximum volume to which the lung can be expanded.
- is TLC - RV (max expiration after max inspiration)
- RV + ERV
- TV + IRV (the total volume that can be inhaled after normal expiration)
FRC is an important buffer because ….
prevents extreme changes in alveolar PO2 with each breath, otherwise, PO2 will be equal to that of venous blood at the end of each expiration
FRC & TLC can be measured with ……
gas dilution or plethysmography
- due to the presence of RV
- Note: RV increases with age, COPD & asthma due to air trapping
- Gas dilution is measured with helium gas. This method is used to measure RV
FEV 1 is ….
volume expelled after one second.
* a person can exhale about 80% of VC in one second
FEV 1 is reduced in ….. & ….. , however, there is a difference. What is it?
obstructive airway disease & restrictive airway disease
- In restrictive diseases (fibrosis), all volumes are reduced and the flow rate is reduced proportionately. So FEV 1 : VC is normal.
- In obstructive diseases (emphysema, asthma, chronic bronchitis etc..), FEV1 : VC is disproportionately reduced, and is a measure of the disease severity.
Minute ventilation (Vm) is ….
the volume of air entering the airway each minute (about 6 liters, 500mL x 12 breath/min)
Anatomic dead space is decreased by …. & …. . The normal volume for this space is ….
tracheostomy & pneumonectomy (removal of a lung)
150 mL
* Lobectomy is removal of lobe, not the whole lung
Alveolar ventilation (Va) is ……..
the volume of air entering the alveoli per unit time
- Va = R rate x (TV - volume of dead space)
- Va is about 350 mL for each breath
Physiologic dead space includes both ….. & …..
anatomic dead space + non functional alveolar space (due to poor ventilation)
* measure by Bohr’s equation (ratio of dead space to Vt)
Upper regions of the lung is better ventilated. T/F?
False
lower regions are better
* Because the upper parts are suspended by the trachea and are more stretched, while the lower parts are not. The upper parts are not very well ventilated because there is no room for expansion
The same goes for the blood vessels (more stretched means less perfused)
The lung extends from above …., …. ant, …. lat, & … post
clavicle, 8 rib, 10 rib, 12 rib
Blood supply to the lung is through …. & …..
bronchial, pulmonary arteries
* most of bronchial blood is returned by the pulmonary vein
The pulmonary circulation has low …..
resistance & high blood flow
* To accommodate more blood without increasing pressure through recruitment of unperfused capillaries
Hypoxia …. pulmonary vascular resistance
increases
Effortful inspiration requires ….. & …. muscles, while effortful expiration requires …… & ……
scalene & SCM muscles, trapezius & ext. intercostals
abdominal & internal intercostal muscles
Obstructive lung disease increases ……, while restrictive diseases decreases ….
resistance
compliance
Surface tension of fluid exerts …..
an inward directed forces to resist distension
Vital capacity in ….. diseases decreases below normal
restrictive
Visceral and Parietal pleura are ……
held together by surface tension of fluid
Dalton’s law is …
sum of partial pressures of all gases equals the total pressure
Pgas = Pb x Fgas
* Pb is 760 mmHg
* (note): air becomes humidified at body temp in the nose & mouth
Ph2o = 47 mmHg and must be substracted
Henry’s law is ….
The concentration of gas that dissolves in a liquid is proportional to its partial pressure and solubility coefficient
[O2]blood = Po2 x Ks
* Kco2 is 30 times more than that of O2, and has about 1/3 more molecular weight, so it dissolves more in plasma
Fick’s law is …..
the rate of diffusion of a gas is proportional to partial pressure gradient, surface area of diffusion & diffusion constant, and inversely to the thickness of barrier
- V = A/T x D (P1-P2)
- D = gas solubility / square root of m.w
A:T ratio for the lung is …..
very high
- A is the surface area (75 square meter)
- T is thickness (0.5 micrometer)
Why diffusion capacity is measured by CO?
because its transfer to the blood is limited by diffusion, not by pulmonary blood flow
Diffusion capacity can decrease due to …., …. & …..
- Increase thickness of blood-gas barrier
- Decrease surface area of the barrier (emphysema, lesions etc…)
- Decrease in ability of O2 to bind to Hb (occlusion of blood flow, anemia etc…)
Pulmonary arteries travel ……., while the veins are …..
with the bronchi through the centers of primary lobules
course between the lobules
The pressure gradient in the systemic circulation is ….. than the pulmonary circulation. The blood flow is …..
higher
the same
* The flow rate are identical because the two circulation are in series
Vascular resistance is high in the systemic circulation because of ….., while the pulmonary circulation …..
arterioles
has very little vascular musculature & low resistance
When pulmonary arterial pressure rise, vascular resistance …..
decrease
* same response for pulmonary veins, but to a lesser extent
Pulmonary vascular resistance increases in ………. lung volume
high and low
* minimum is at intermediate values
The alveolar sac is located at …..
the end of the terminal bronchiole
Bulk flow is ….
the movement of gas driven by pressure difference
Decreased Po2 or increased Pco2 leads to increased pulmonary vascular resistance, why?
To divert blood away from the poorly ventilated area.
* This response is in contrast to the response of the systemic vascular smooth muscles to the same stimuli
Factors causing pulmonary vascular constriction are …., …. & ….
low pH (hypoxia), sympathetic discharge, drugs * isoproterenol is an inotropic (similar to epinephrine)
Rate of displacement of O2 by CO2 in the alveoli depends on …
the metabolic rate
Flow rate in the lower lung is higher than the upper because of ….
increased hydrostatic pressure due to gravity
* Alveolar ventilation also increases in the same direction
Alveolar space is maintained free of fluid because of ….
low capillary pressure with high osmolarity
* In pulmonary hypertension, fluid may accumulate
Interstitial edema is …. , while alveolar edema is ……
accumulation of fluid in perivascular and peribronchial spaces
is accumulation of fluid in alveolar spaces preventing ventilation
The main cause of hypoventilation are …..
- drugs that suppress the respiratory center in the medulla (barbiturates, opiates, anesthesia etc..)
- Airway obstruction & COPD
- respiratory muscles paralysis
- Guillain Barre, multiple sclerosis
Alveolar - arterial Po2 is at equilibrium. T/F
False
there is always a gradient, and it increases with exercises, increase barrier thickness, low O2 inspired etc…
* This mismatch between ventilation - perfusion is the most common cause of low O2
If the A - a oxygen gradient is greater than the normal (10 - 20 mmHg), this means that ….
O2 transfer in the lung is impaired and is the cause of hypoxemia
* Normal PaO2 is (80 - 100 mmHg). Patient is hypoxemic if it falls below 50 mmHg
If V/Q ratio is zero, it means ……
If V/Q ratio is infinity , then it means…..
zero ventilation (airway obstruction, PaO2 & PaCO2 is the same as the venous blood) blood vessel is occluded and flow is zero (PaO2 & PaCO2 is the same as the inspired air)
O2 is not found in plasma because ….
it has low solubility coefficient
Each Hb molecule can reversibly bind up to ….. O2 depending on O2 partial pressure
4 molecules
Explain positive cooperativity of O2
The binding of an O2 molecule to one heme group will increase O2 affinity to other groups
Normal Hb concentration in blood is ……
15 g/dL
- Each gram can combine with 1.36 mL O2
- Each dL can carry 20 mL O2
if V/Q mismatch is high (low perfusion), hypoxemia can be reversed by ….
O2 administration
P50 is the O2 pressure ….
at which half the Hb sites are occupied
- PO2 is about 27 mmHg
- At PO2 40, 75% of the Hb sites are occupied (venous blood)
Hb loses one O2 on its way from …….
lungs to tissues
What factors affect the Hb saturation curve and how?
- pH: low pH shifts the curve to the right (Bohr effect is demonstrated at the beginning of the alveolar capillary as it has high PCO2)
- CO2: right shift
- Temp: high temp and CO2 causes right shifting, favoring O2 release from Hb to tissues
Normal Hb saturation curve shows …. O2 is binding than the …… for the same PO2
more
right shifted curve
Increased blood concentration of 2,3 DPG shifts the curve to ….
to the right
What is 2,3 DPG?
it is an allosteric activator for RBCs to release O2 near tissues
- It is formed from glycolysis (1,3 bisphosphoglycerate mutase catalyzes the reaction to form 2,3 bisphosphoglycerate) when O2 demand is increased by tissues
- It can be reconverted to 3-phosphoglycerate by phosphatase to continue glycolysis
- This is a delicate balance between the need for ATP or O2
- 2,3 DPG formation is inhibited by low pH
CO2 is about ….. times more soluble than O2 in plasma
20
* about 95% is dissolved in plasma
HbF (fetal) has higher affinity than the regular, why?
to favor extraction of maternal O2
Fetal Hb and CO shifts the curve to
the left
- CO prevents O2 release from Hb, causing tissue hypoxia, although it increases O2 affinity to Hb
- CO has about 230 times the affinity of O2 to Hb
- CO + Hb —-> carboxyhemoglobin
The enzyme ….. accelerates the combination of CO2 & H2O to form ….
Carbonic anhydrase
HCO3
* 65% of CO2 taken from tissues is converted to HCO3 in the RBC
Once formed in the RBC, HCO3 is cotransported against …. to enter the plasma, this is known as the …..
(antiported) against Cl
Cl shift
* Cl shift promotes further CO2 uptake by RBCs
Dissolved CO2 can combine with aminoacids to form …. . This can occur in the RBCs to form ….
carbamino compounds
carbaminohemoglobin
* Hydrogen ions are released from this reaction and from the formation of HCO3, this H is buffered by RBCs
* O2 and CO bind to Fe+2 , not to NH2 like CO2
Adults Hb has more affinity to O2 than HbF. T/F??
True
but the formation of 2,3 DPG (which is absent in the fetal state) reduces this affinity
Myoglobin is …..
the iron & oxygen binding protein, found in muscle tissue.
- CO binds more to myoglobin than O2, causing hypotension & reduced cardiac output
- Myoglobin gives the red color to meat
The Halden effect means ……
Oxygenated blood has reduced capacity for CO2, while deoxygenated blood has more CO2 carrying capacity
The respiratory control center controls ….. . It is located in the ….. & ….
the rate of respiration, and hence alveolar ventilation to meet the body O2 demand
Located in the reticular formation of the medulla and the pons
see p.453
Medullary centers control the rhythmicity of respiration via …..
the antagonistic action of the inspiratory & expiratory motor neurons
- Both these have alpha fibers extending to their effector respiratory muscles
- The expiratory center only functions during forceful expiration
The apneustic center is located in ….., its function is to ….. . It is inhibited by ……
- lower pons
- initiate respiration by activating the inspiratory center in the medulla
- Lung inflation receptors
- it is most active when the person is awake
The apneustic center is controlled by ….. , which is in turn activated by the ……
Peumotaxic center (upper pons)
medullary inspiratory center
* The pneumotaxic center, when active, inhibits the the apneustic center
The apneustic center is activated by ……, and inhibited by …..
chemoreceptor
lung inflation receptors
During inspiration, the apneustic center is inhbited by …. & ….
pneumotaxic center & inflation receptors
The Hering-Breuer reflex is …..
activation of stretch receptors during inspiration to inhibit the apneustic center.
- Inhibition builds gradually until the start of expiration. These receptors are less active in adults
- Similar receptors are present for expiration, in the trachea and bronchi
- Signal transmitted via vagus to tractus solitarius
Dust receptors are activated by …., with the result being ….. & …..
dust particles
hyperpnea & bronchoconstriction
* normally inactive
Juxtacapillary (J receptors) are activated by ….., leading to …… , …….
pulmonary edema
tachypnea & hyperpnea with shallow breathing
Gamma receptors are found in ….. & ….. with the function of ….
diaphragm & intercostal muscles
adjusting the respiratory muscle to the load against which they contract
Peripheral receptors respond to …. & …. to adjust the respiratory rate. These receptors are the only ones to respond to …….
Low PO2 & high PCO2
hypoxia (central receptors do not)
* carotid receptors transmits signals via IX, aortic receptors transmits signals via X
* PCO2 receptors are not as important as the PO2 ones
Central chemoreceptors are composed of …… and located on …. . They are sensitive to ……
four localized groups on the ventral surface of the medulla (near the exit of IX & X)
They are sensitive low pH (high PCO2)
* They are surrounded by CSF and are separated from the blood
* Efferents reach the apneustic center, stimulating breathing
* They don’t respond to low PO2
Decreased pH stimulates chemoreceptors. T/F?
True
carotid body chemoreceptors respond to regardless of PCO2 levels
Patients with COPD are adjusted to ….. . So the main drive for respiration is ….
High PCO2
arterial hypoxia detected by peripheral chemoreceptors
* Low pH is abolished by renal compensation, so pH has no role in ventilation in this case
O2 supply is contraindicated for patients with COPD. Why?
because hypoxia is the sole stimulus for respiration (since they are used to high blood PCO2)
What are the muscles involved in respiration??
- Inspiration: external intercostals & diaphragm
2. Expiration: (only forceful) internal intercostals & abdominal muscles
The lung and the chest wall have ……. The intrapleural pressure is …. . They are at equilibrium at ….
opposing natural relaxation states
-5 cm H2O
FRC
* Airway pressure at FRC is atmospheric (760mm Hg), alveolar is zero, intrapleural is < FRC
* Muscle contraction is needed to ↑ or ↓ lung volume from FRC.
During inspiration, the interpleural pressure becomes ….., while during forceful expiration it becomes ….
-8 cm H2O
+1 cm H2O
Lung compliance is …
the static change in volume per unit change in pressure (delta V/delta P)
* P is in cm H2O
* Lung is distensible at low volume & stiffer at high volumes
see p. 456
Atelectasis is ….
collapse of lung units after a period of non functioning
Compliance is increased in ……. & decreased in ……
- Age, emphysema
2. increased pulmonary venous pressure, atelectasis, fibrosis
On the pressure volume curve, hysteresis means …..
lung volume is greater at given pressure during deflation than during inflation
Compliance of the lung is due to ….. & …..
elasticity & surface tension
Laplace law is ….
P = 2 x T x t / r * P: pressure required to keep the alveoli patent T: surface tension t: wall thickness r: radius of alveoli
Surfactant is secreted by …. , and it consists mostly of ….
Type II pneumocytes
dipalmitoyllecithin (dipalmitoyl phosphatidylcholine)
In the absence of surfactant, high pressure is need to keep the deflated alveoli open, why??
because of the small radius of the alveoli. With surfactant, the alveoli remain patent at lower pressure of deflation
Surface tension is greater for the same surface area undergoing inflation than it is for deflation. T/F??
true (hysteresis)
* the higher the pressure the greater the surface tension
The surfactant prevents …… & …..
alveolar collapse & H2O accumulation in the alveoli (by preventing the surface tension from pulling H2O from the capillaries)
Surface tension …… recoil forces & ….. compliance
increases , decreases
* Surfactant is needed to reduce the pressure needed to prevent collapse
Mixed laminar and turbulent flow occurs at ….
trachea and bronchi
The maximum expiratory flow volume curve can be exceeded. T/F??
False
it can not be exceeded at any condition
Transmural pressure means …..
the difference between alveolar and intrapleural pressure that drives respiration
* Negative in inspiration, positive in expiration
Why expiratory flow is effort independent?
because of the transmural pressure
Dynamic compression is ….. and it occurs in …..
collapse of the airway during forced expiration
patients with increased compliance (emphysema)
- may occur in normal expiration in patients with emphysema, not only forced
Hypoxic hypoxia means …..
decrease arterial O2 due to high altitude or lung disease
Anemic hypoxia means …..
decrease O2 carrying capacity like in anemia or CO poisoning
Circulatory hypoxia means ….
diminshed blood flow to tissues (PaO2 is normal)
Histotoxic hypoxia means ….
tissues can not utilize O2 (eg. cyanide)
* Cyanide inhibits cytochrome C oxidase in the ETC by binding to Fe (prevents transport of electrons from cytochrome c oxidase to oxygen)
The failing of the central respiratory drive is called ……
central apnea (the patient must actively control breathing) * Ondine curse is an extreme case
Obstructive sleep apnea is treated by …. & …..
dental appliance (forcing the lower jaw & tongue forward)
CPAP (continuous positive airway pressure)
* factors contributing to sleep apnea are
1. obesity
2. small jaw
3. large tongue/tonsils
4. defective muscles
Chronic low PaO2 causes …..
- Hyperemia
- increased cardiac load & hypertension
- premature death
- cardiac arrhythmia
Ventilation is more closely related to CO2 exhaled than O2 inhaled. T/F??
True..
That is why ventilation increases some time after the start of exercise
The non chemical inputs for respiration during exercise include …
- cortical input
- joint proprioceptors
- respiratory muscle spindle regulation
Increased O2 uptake is proportional to workload. T/F??
True
there is a limit, after which O2 consumption levels off and lactate accumulates
CO2 retention is called …..
hypercapnea
* It is a hallmark of type II respiratory failure
Methemoglobin is ….. and is caused by …..
the oxidation of an Fe in the Hb molecule forming ferric instead of ferrous (while the other three remain in ferrous). Has high O2 affinity, causing reduced ability to release O2 to tissues
* caused by deficiency of methemoglobin reductase, or sulfonamides (antibiotics)
Each RBC has about …… Hb molecules
300 million
CO2 narcosis is ….
a condition of confusion, tremors, convulsions and coma, caused by chronically elevated CO2
What is the effect of CO2 levels in blood on the cerebral circulation??
High CO2 causes vasodilation, low CO2 causes vasoconstriction
What is the cause of hyperventilation in shock??
caused by chemoreceptor stimulation (secondary to ↓ PO2 (hypoxia) and ↑ H+ (acidosis)) because of local stagnation of blood flow.
What is the cause for the symptoms (dizziness, blurred vision, chest tightness …) during anxiety???
The cause is hyperventilation, which leads to cerebral vessels vasoconstriction
Carotid/Aortic bodies are ……
chemoreceptors
* Carotid/Aortic sinuses are baroreceptors
Hyperapnea is …..
abnormal deep and quick breathing
- Kussmaul breathing is hyperapnea due to metabolic acidosis
- Tachypnea, unlike hyperapnea, is shallow breathing
