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