Respiratory Phys: Ventilation and Mechanisms of Breathing Flashcards
Define ventilation
the volume of air moving into or out of the lungs
*usually expressed as a rate
What are the 5 steps of respiration?
- ventilation
- exchange of O2 and CO2 btwn alveolar air and capillaries by diffusion
- Transport of O2 and CO2 thru pulm and systemic circulation
- Exchange of O2 and CO2 btwn blood in tissue capillaries and cells in tissues by diffusion
- Cellular utilization of O2 and production of CO2
Define TLC
total lung capacity
-Max expiration volume + residual volume
Define TV
Tidal Volume
-volume of a normal breath
Define FRC
Functional Residual Capacity
-volume of air left in lungs after normal expiration
Define RV
Residual Volume
-volume of air left after max expiration
Define VC
Vital capacity
-volume of max expiration
Define FVC
Forced vital capacity
-volume of air that is exhaled during a forceful expiration
Define FEV1
Forced Expiratory Volume in 1 second (with max inspiration)
-normal ~80%
lung DZ in which air cannot get out
obstructive lung disease
-asthma, emphysema
lung DZ in which air cannot get in
restrictive lung disease
-obesity, pulmonary fibrosis
How is FEV1:FVC ratio affected in obstructive lung disease? Restrictive?
obstructive: the ratio decreases because expiration is blocked
Restrictive: normal (both FEV1 and FVC decrease proportionally bc less it able to be inhaled)
What are 3 factors for determining lung volumes?
gender, weight, age
What is the anatomical dead space?
volume of air in the conducting pathways that is not available for gas exchange
What is alveolar dead space?
volume of alveolar space not available for gas exchange due to lack of blood supply. Always pathologic!!
What is physiologic dead space?
sum of anatomical dead space and alveolar dead space
What is the difference between minute ventilation and alveolar ventilation?
minute = amount of air moved in and out of lung (aka total ventilation) per min
alveolar = amount of air moved in and out of lung - dead space per min
What type of breathing is more effective for increasing alveolar ventilation? Why?
slow deep breaths that will increase in TV with dec RR
Alveolar ventilation = (TV x RR) - (dead space volume x RR)
What is the driving force that moves air into and out of the lungs?
the pressure difference between the alveoli and the mouth ( aka atmosphere)
What is the trans-respiratory system pressure?
pressure difference between the alveoli and the atmosphere (i.e. what determines the flow of air)
Prs = Palv - Patm
What is the transpulmonary pressure (aka transmural pressure)?
pressure diff between the alveoli and the intra pleural pressure
Ptp = Palv = Pip
Compliance relates:
the change in volume of a closed system to the change in pressure distending it
Compliance formula
(change in lung volume) / (change in transpulm pressure)
Surface tension (increases/decreases) compliance
decreases
Restrictive lung disease causes (increased/decreased) compliance.
How does this affect lung volume/capacity?
decreased
decreases (can’t get air in)
Obstructive ventilatory defect causes (increased/decreased) compliance.
How does this affect lung volume/capacity?
increased
Increases FRC, TLC, RV (**cannot get air out)
Nml/decreased FVC
Decreased FEV1
Measure of elastic properties of lung tissue; normalized by dividing by:
specific compliance
FRC
____ = lung compliance / unit lung vol
specific compliance
depends on total vol of system
How does COPD affect lungs?
increases compliance due to loss of elastic fibers; large airways collapse due to loss of elastic recoil
(loss of elastic recoil decreases alveolar pressure and airway pressure)
How does emphysema affect flow (formula)?
decreases by decreasing transpulmonary pressure
flow = Ptp / R
How do asthma/bronchitis affect flow (formula)?
decrease by increasing resistance
flow = Ptp / R
2 major factors determining lung compliance
tissue properties
surface forces
How do the properties of lung tissue improve its ability to expand?
- comprised of large amounts of collagen and elastin (responsible for 1/3 of lung elasticity)
- interdependence of alveoli
because alveoli have many connections and are surrounded by one another, expanding forces of surrounding alveoli counteract collapse of one alveolus
Expansion of the lung must must overcome: (2)
forces of elastic tissues
surface tension
Why is surface tension pretty bad for yo lungs?
surface tension causes closure of alveoli (as a result of H-bond attraction between water molecules)
What is the function of pulmonary surfactant?
What is it composed of?
reduce surface tension
phospholipids, cholesterol, proteins produced by type II alveolar epithelial cells
Where are the components of pulm surfactant stored?
lamellar bodies
What stimulates production of pulmonary surfactant?
deep breath (large expansion fo lungs), which stretches type II alveolar epithelial cells
What causes respiratory distress syndrome?
(in newborns) little or no surfactant production makes the lungs difficult to inflate (i.e. decreased compliance) and causes atelectasis (unstable alveoli that collapse on expiration)
What does surfactant prevent, on the level of alveoli?
prevents smaller alveoli from collapsing into larger alveoli
Formula: (FYI)
P = 2T/r
transmural pressure needed to keep open an average sized alveolus
4 factors affecting airway resistance
- anatomic (radius and lateral traction)
- lung vol
- contraction of bronchial smooth muscle
- density and viscosity of inhaled gas
Mouth resistance is (>/<) nasal resistance
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The most important factor in determining the resistance of a given segment is:
tube radius
Major resistance is in the (upper/lower) airways.
Why?
upper, due to branching (which increases the overall cross-sectional area)
Ar flow is dependent on:
pressure difference
resistance to flow (inversely proportional)
How does lateral traction affect airway resistance?
elastic CT fibers attach to exterior of airway and pull outwards, which keeps airway open
How does lung vol affect airway resistance?
as vol increases, the airway diameters increase–this decreases resistance
How do asthmatics overcome high airway resistance? (this is just a practical application)
increase their lung vol (“breath at high lung vol”) to maintain larger diameters, which decreases resistance
How does smooth muscle drive conditions like asthma and bronchitis?
smooth muscle in the airway contracts strongly, with dramatically increases resistance
**sorry, I know this wording is off
What determine air flow? What determines the inflation of the lung?
air flow is determined by the pressure gradient between the alveoli and the atmosphere/mouth (trans-respiratory system pressure)
lung inflation is determined by the pressure gradient between the alveoli and the intrapleural space (transpulmonary/mural pressure)
What muscles are involved in quiet inspiration?
forceful inspiration/exercise?
diaphragm (some external intercostal muscle contraction to elevate ribs)
diaphragm, scalenes, sternocleidomastoid, external intercostal muscles
What muscles are involved in quiet expiration? Forceful expiration/exercise?
COMPLETELY PASSIVE!! (diaphragm relaxes)
rectus abdominus, internal and external obliques, transverse abdominus, internal intercostal muscles contract (diaphragm relaxes)
Describe the process of inspiration.
The diaphragm contracts, causing the volume of the thorax to increase. As lung volume increases, the pressure in the lungs must decrease. (Boyle’s law) Alveolar pressure falls below atmospheric pressure during lung expansion and this pressure gradient between the atmosphere and the alveoli drives airflow into the lung (Trans-respiratory system pressure). When alveolar pressure is once again equal to atmospheric pressure; the pressure gradient between the atmosphere and the alveoli is 0 and airflow into the lungs stops.
Describe the process of expiration.
Diaphrsgm relaxes and the chest wal recoils/decreases in volume. Alveolar pressure becomes positive (higher than atmospheric pressure) because the elastic forces of the lungs compress the greater volume of air in the alveoli. When alveolar pressure increases above atmospheric pressure, air flows out of the lungs and the volume in the lungs returns to FRC
Do we need to know the exact pressures throughout the respiratory cycle?
bc the values on the slide do not match the ones in costanza
What is a pneumothorax? How is the respiratory cycle disrupted?
the chest wall becomes pierced and the intrapleural pressure becomes atmospheric. The increased pressure causes the alveoli/lung to collapse
