Respiraotry physiology - Exam 2 Flashcards
purpose of the respiratory system
to provide O₂ and remove CO₂
ventilation
exchange of air between atmosphere and alveoli by bulk flow
ventilation
exchange of air between atmosphere and alveoli by bulk flow
Exchange of CO₂ & O₂
- between alveolar air and blood in lung capillaries by diffusion (external respiration)
- between blood in tissue capillaries and cells in tissues by diffusion (internal respiration)
transport of O₂ and CO₂
through pulmonary and systemic circulation by bulk flow
cellular utilization of..
O₂ and production of CO₂
pleural membrane
pleura → serosa of the lung
visceral → attached to lung
parietal → attached to chest wall
serous fluid
- fluid between the lung, pleura, and ribs
- ** provides lubrication allows lung to move along the pleura and suction
Boyle’s law
PV = nRT
** Pressure is inversely proportional to the volume
understanding ventilation
- laws of diffusion (gases moving from higher concentrations to lower concentrations)
- Boyle’s law (P and V inversely related to each other)
** Quiet inspiration
active
- diaphragm contract
- external intercostals contract
- utilization of ATP through skeletal muscles
Forced inspiration
trying to create more additional space
** Quiet expiration
resting
- passive process “recoil”
- elastic properties of lung
forced expiration
active
- abdominals
- internal intercostals
alveolus
site of gas exchange
alveoli epithelial cells
type I: squamous epithelial cells, important for gas exchange
type II: make surfactant, help reduce surface tension
P suffix ip
intra pleural pressure
this needs to work in hand with changes that accommodate ventilation
transpulmonary pressure/transmural pressure
pressure differences holding lungs open (opposes inward elastic recoil of the lung)
- typically Pip < Palv
- Pip at rest = -4 mm Hg
** to accommodate inspiration Pip becomes
more negative
subatmospheric
then Ptp becomes more positive
Ptp = Palv - Pip
inspiration flow diagram
- diaphragm and inspiratory intercostals contract
- thorax: expands
- Pip becomes more subatmospheric (negative)
- ↑ transpulmonary pressure
- lungs: expand
- Palv becomes subatmospheric
- air flow into alveoli
expiration flow diagram
- diaphragm and inspiratory intercostals stop contracting
- chest wall: recoils inward
- Pip moves back toward preinspiration value
- transpulmonary pressure moves back toward preinspiration value
- lungs: recoil toward preinspiration size
- air in alveoli becomes compressed
- Palv becomes greater than Patm
airway resistance
- flow = △P(3.144)r⁴ / (8ul)
- resistance = 8ul/(3.144r⁴ ) ***
depends on the length of the airway and the viscosity of the gas and is inversely proportional to the fourth power of the radius
l = length of airway
u = viscosity of the gas
r = radius of the airway
airway resistance can also be termed as
obstruction to the airflow
which causes more resistance, upper or lower airway?
upper
decrease in lung volume results in an __ in resistance
increase
compliance of lungs
determined by elastic forces
elastic forces
- lung tissue
- surface tension
surface tension
- attraction of water molecules at the air-water interface
- will result in collapse of alveoli
- prevented by surfactant
*** vital capacity is the combination of
ERV = amount of air in excess of tidal expiration that can be exhaled with maximum effort
TV = amount of air inhaled and exhaled in one breath
IRV = amount of air in excess of tidal inspiration that can be inhaled with maximum effort
** amount of air that can be exhaled with max effort after max inspiration; used to assess the strength of thoracic muscles as well as pulmonary function
RV
residual volume
amount of air remaining in the lungs after max expiration; keeps alveoli inflated between breaths and mixes with fresh air on next inspiration
anatomical dead space
- part of the respiratory system where gas exchange does no take place
- 150 mL
- conducting airways
physiological dead space
- depends on ventilation-perfusion ratio
minute ventilation
total amount of air moves into and out of the respiratory system per minute
alveolar frequency
how much air per minute enters parts of the respiratory system in which gas exchange takes place
minute respiratory volume
TV x RR
alveolar ventilation
(TV- dead space) x RR
the bottom portion of the lung has a __ blood flow compared to the top of the lung at REST
higher
*** pulmonary pressures
pulmonary artery pressures
- systolic 25 mmHg (quarter)
- diastolic 8 mmHg (almost a dime)
- mean 15 mmHg (dime + nickel)
- capillary 7 mmHg (dime + 2 pennies)
Hypoxic vasoconstriction
less ventilated alveolus has a vasoconstricted pulm capillary
inward forces
d/t plasma proteins causing plasma osmotic pressure that pulls the water into the pulmonary capillary
plasma osmotic pressure 28 mmHg
outward forces
force of the fluid trying to go out of the capillary into the interstitial space
pulmonary capillary pressure 7 mmHg
interstitial osmotic pressure 14 mmHg
negative interstitial pressure 8 mmHg
total = 29 mmHg
net filtration pressure
1 mmHg
*** __ Interstitial pressure keeps alveoli dry
negative
pulmonary edema
fluid accumulation in pulmonary interstitial space
pulmonary edema causes:
- increase in pulmonary venous and capillary pressure (left-sided HF, mitral valve stenosis); ↑ outward force
- increased capillary membrane permeability (damage to associated with infections, noxious gases (chlorine, sulfur dioxide)
- decrease in plasma oncotic pressure (liver failure); ↓ inward force
*** pulmonary edema safety factor
protection against edema until pulmonary capillary pressure ( 7 mmHg) equals capillary osmotic pressure (28 mmHg)
pleural effusion
excess fluid accumulation in the pleural space
pleural effusion causes:
- lymphatic obstruction (tumor)
- HF
- reduced plasma osmotic pressure
- infection/inflammation of capillary membranes causing increased permeability
- fluid production > drainage
components of respiratory unit
- terminal bronchiole
- respiratory bronchiole
- alveolar ducts
- alveolar sacs
alveolar walls - very __ walls to aid in gas exchange
thin
300 million alveoli in 2 lungs
gas exchange occurs where?
alveolar sacs
barriers for diffusion are:
surfactant/fluid
alveolar epithelium
epithelial basement membrane
interstitial space
capillary basement membrane
capillary endothelium
layers that create a barrier for diffusion of O2 and CO2
diffusion in response to
concentration gradient
pressure proportional to
concentration
gas contributes to total pressure in direct __ proportion to concentration
direct
CO₂ __ times as soluble as O₂
20
diffusion depends on __ __ of gas
partial pressure
air is humidifed yielding a vapor pressure of __ mmHg
47
ventilation/perfusion
- the relationship between adequate ventilation and adequate flow
- defined as V/Q
- V/Q (4L/min) / (5L /min) = 0.8
alveolar PO₂ and PCO₂
determined by the ratio between ventilation and blood flow: V/Q
PO₂ and PCO₂ are __ related through alveolar ventilation
inversely
increasing V/Q produces
higher PAO₂ and lower PACO₂
hyperventilation defined as PACO₂ < 40
decreasing V/Q produces
lower PAO₂ and higher PaCO₂
hypoventilation is defined as PACO₂ > 40
V/Q if inadequate ventilation
- less V ↓↓
- 0/Q = 0
- V/Q = 0
- smaller value or nothing when there is inadequate ventilation
V/Q if inadeqaute perfusion
- block in the flow of blood so there can still be good ventilation but perfusion ↓
- anything over 0 is infinity
- V/Q = ∞
- higher value when there is inadequate perfusion
physiologic shunt
- V/Q < normal
- low ventilation
physiologic dead space
- V/Q > normal
- wasted ventilation
abnormalities with V/Q
- upper lung V/Q 3 x normal
- lower lung V/Q .5 x normal
