Dr. Poole's Test Flashcards
What is the principle function of the lung?
- gas exchange (principle function)
- acid base regulation
- filter toxins
By what process do O2 and CO2 move between the air and blood within the lung?
diffusion (from higher to lower pressure)
Ficks law
Vgas= A/T x D (Pa- Pblood)
increased surface area
decreased thickness
CO2 is more diffusible
Change in pressure is more in favor of oxygen
What are the two zones of the lung and in which one does the most gas reside?
- conduction zone (airways that do not help with gas exchange) (150 ml)
- respiratory zone (alveoli) (2-5 L)
Respiratory zone takes up most of the volume of the lung (2-5 L)
How may airway bifurcations are found in the human lung?
23 bifurcations
First 16 in conducting zone
last 7 in the respiratory zone
Draw a graph depicting the relationship between airway generation and total airway cross sectional area
pg 5 lecture 1 and 2
What are the 3 cell types found in the alveoli an what are their functions?
- Type 1 (egg shaped) (90% of alveolar wall)
- Type 2 ( secretes surfactant lowering surface tension)
(these contribute to the high compliance and distensibility of the lung) - macrophages (engulf tiny particles too small to be filtered out upstream)
type 1 alveolar cells
egg shaped and make up 90% of the alveolar wall
type 2 alveolar cells
- secrete surfactant lowering the surface tension
- contributes to the high compliance and distensibility of the lung
macrophages
engulf tiny particles too small to be filtered out upstream
What are the two main forms of connective tissue found in the lungs?
collagen and elastin
ventilation at rest
7,500 ml/min or 7.5 L/min
tidal volume
500 ml or .5 L
respiratory frequency
15 breaths/min
alveolar gas volume
3,000 ml 3L
dead space volume
150 ml or .15 L
pulmonary capillary blood volume
70 ml
pulmonary blood flow
5000 ml/min
alveolar ventilation
5250 ml/min
functional residual capacity
volume of gas in the lung at expiratory level
total lung capacity
volume of gas in the lungs at the end of max inspiration
how much you can breathe in
residual volume
volume of gas in the lungs at the end of maximal expiration
left over air/gas
vital capacity
maximal volume that can be expired after maximal inspiration
(greatest volume of air that can be exhaled)
Explain why it is more efficient to breathe more deeply (increase tidal volume) than increase breathing frequency.
deeper breathing is more efficient
rapid shallow breathing wastes too much air in the dead space
Where in the lung does most of the inspired air go and why?
ventilation is much higher at the base of the lung due to gravity
- it is reduced when the subject lies down and reduced the vertical height of the lung
what is the only respiratory muscle active at rest?
diaphragm
Define lung compliance
pressure vs volume
(we want a big change in volume but not a big change in pressure)
we don’t breath at higher lung volumes because the lung is stiff up there
What happens to the respiratory system when some knucklehead sticks a knife into the pleural space?
pneumothorax
- pierced chest wall and intrapleural space
- the lung is trying to collapse while the chest wall is trying to spring outward
what relationship determines the shape of expiratory flow V(volume) and how is this affected by emphysema and fibrosis?
emphysema- high lung compliance, low recoil (baggy lung) (intrapleural pressure is less negative)
fibrosis- low compliance, high recoil (intrapleural pressure is more negative)
emphysema
low recoil
decreased alveolar pressure
increased Resistance
fibrosis
lungs so stiff that TLC cannot be achieved
increased alveolar pressure
no change or slight decrease in resistance
Why are peak flows so low in emphysema?
the lung is baggy and has low recoil
- alveolar pressure is decreased
- low recoil
- increased resistacne
Why is the pressure of O2 (PO2) in the alveolar space ~ 100 mmHg?
use the alveolar gas equation
alveolar gas equation
PAO2 = PIO2- (PCO2/R)
inspired air equation
PIO2 = (21/100) x (barometric pressure - 47)
At a pressure of 100 mmHg, how much O2 can be carried in the arterial blood?
use Hb equation?
Hb equation
02 ml/100 ml = ([Hb] x 1.34 x .97) + (PO2 x .003)
What are the values for arterial and venous po2 and pCO2?
Arterial PaO2= 100 mmHg
Venous PvO2= 40 mmHg
Arterial PaCO2 = 40 mmHg
Venous PvCO2 = 46 mmHg
Draw a graph depicting the change in PO2 of red blood cell as it traverses the pulmonary capillary
pg 14 Lecture 5
Why is the alveolar PO2 (PAO2) 100 mmHg whereas that in dry inspired air is 159 mmHg?
use PIO2 = (21/100) x (barometric pressure - 47)
plug that into PAO2= PIO2 - (PCO2/R)
takes into account the water vapor
in what region of the brain are the inspiratory and expiratory neurons located?
pons and medulla
medulla
pattern generator
produces stimulus
has CN X and IX
respiratory rythmicity
CN X
vagus nerve (from lungs) has pulmonary stretch receptors
CN IX
glossopharyngeal nerve (from the carotid bodies)
pons
fine tunes and modulates the stimulus
off switch that terminates respiration
what is the main regulated variable?
PCO2= 40 mmHg
what stimulates the central chemoreceptors?
transduced through cerebrospinal fluid (ECF)
-increased ventilation in response to: increased PCO2
what stimulates carotid bodies (peripheral chemoreceptors)?
increased ventilation in response to :
decreased PaO2
decreased pH
increased PaCO2
true or false: central chemoreceptors are behind the blood brain barrier so H+ of HCO3- doesn’t affect them
True. H+ and HCO3- does not affect the central chemoreceptors.
ONLY PCO2 affects the central chemoreceptors
What is the mechanism by which a systemic lactic acidosis causes hyperventilation?
drives pH down and hits the peripheral chemoreceptors or carotid bodies
due to decreased pH (more acidic)
hyperventilation
lowering of arteriole carbon dioxide
Why is pulmonary artery pressure much lower than systemic arterial pressure?
the pulmonary arteriole walls are very very thin because they do not have to push blood out to the body
if the pulmonary arteriol pressure was high the blood gas barrier would have to be thicker causing a problem for blood oxygenation and CO2 removal
explain why pulmonary vascular resistance increases at higher lung volume, high pulmonary artery pressures?
at high high lung volumes the capillaries are being stretched increasing resistance?
give reasons you don’t want to breathe at higher lung volumes
- high vascular resistance making the right side of the heart work harder
- takes more work
what are the 2 processes by which pulmonary vascular resistance decreases during exercise?
recruitment and distension
Fick equation: calculate VO2 if cardiac output is 30,000 ml/min and O2 content falls from 20ml/100ml in arterial blood to 3 ml/100ml in venous blood?
use VO2= Q (CaO2 - CvO2/100)
3,000 ml x (20ml-3ml/100) = 5.1 L
Ficks equation
VO2 = Q ( CaO2 - CvO2/100)
How does pulmonary blood flow change as we move down the lung?
the lung is more perfused at the base of the lung
- blood flow is greatest at base
- ventilation is greatest at base
How does the ventilation to perfusion ratio change as we move up the lung?
ventilation to perfusion ratio increases as you go up the lung
- you blow off more CO2 allowing for more room at the apex for O2
Draw an O2 dissociation curve and label the points
pg 24 Lecture 9 and 10
calculate arterial O2 content at Hb 15 10 and 5
use the Hb equation O2 ml/100ml = (Hb x 1.34 x .97) + (PO2 x .003)
Hb equation
O2 ml/100ml = (Hb x 1.34 x .97) + PO2 x .003)
how much does arterial O2 content increase when a person breathes 100% O2?
slightly increases
arterial blood is 97% saturated at rest so if a person breathes 100% its only increases that 3%
what three properties of exercising muscle helps shift the O2 dissociation curve to the right? How does this affect O2?
- increase in temp
- increase in PCO2
- decrease in pH
O2 comes off much easier
O2 binds less tight
in what three forms is CO2 carried in the blood? Which is the most important for carrying Co2 from the muscles to the lungs?
- Bicarbonate (60%)
- proteins / carbomino compounds (30%) (Hb)
- dissolved (10%)
What are the solubility of O2 and CO2?
O2 = .003 (change in pressure is more in favor of O2)
CO2= .067
CO2 has a greater solubility and dissolves easier across the membrane
