resp 3- ventialtion and pressure changes Flashcards
what are static properties of the lung
mechanical properties when no air is flowing
why are static properties of the lung necessary
necessary to maintain lung and chest wall at a certain volume
what are the 4 static properties
intrapleural pressure (PIP) transpulmonary pressure (PTP) static lung compliance surface tension of lung
what are dynamic properties of the lung
mechanical properties when the lungs are changing volume and air is flowing in and out
why is dynamic lung properties necessary
necessary to permit airflow
3 dynamic properties of the lung
alvoelar pressure (PALV)
dynamic lung compliance
airway and tissue resistance
what is bulk flow
exchange of air between the atmosphere and the alveoli due to gas moving from high to low pressure
what is boyles law
pressure and volume are inversly proportional at contrant T
p1v1=p2v2
which direction does air flow when alveolar pressure is LARGER than atmospheric pressure
air flow out
expiration
which direction does air flow when alveolar pressure is SMALLER than atmospheric pressure
air flow in
inspiration
bulk flow formula
(alv.press. - atm.press)/resistance
change in pressure/ resistance
what are the pleurae
2 types
thin double-layered envelope
parietal and visceral
parietal pleura
covers thoracic wall (inside of rib cage)
visceral pleura
covers the external surface of the lungs
what does intrapleural fluid do
reduces friction of lungs against thoracic wall during breathing
what is lung elastic recoil (what does it do)
lung have a tendency to collapse
what determines lung volume
the interaction between the lungs and the thoracic cage
what is chest wall elastic recoil
pull thoracic cage outward
how does elastic recoil equilibriate
inward elastic recoil of lungs balances outward elastic recoil of chest wall
what is PIP (definition)
the pressure within the pleural cavity
what is PIP like
a vaccuum because it is always subatmospheric (negative pressure)
what would happen if PIP=PALV
lungs would collapse
what is PALV
the pressure of air inside the alveoli
what is PALVs role
directly producing air flow, it is dynamic
it governs the gas exchange between lungs and atmosphere
maintain lung expansion in thorax
what is PTP
force responsible for keeping the alveoli open
the pressure graident across the alveolar wall
PTP formula
PTP=PAVL-PIP
what does PTP determine
lung volume
is PTP static or dynamic
static, it does not cause airflow
determines lung volume
is PALV static or dynamic
dynamic, determines air flow
flow formula
change in pressure/resistance
what are the resistive forces in the airway
inertia (negligible)
friction
how does friction affect the airway
lung tissue past itself during expansion
lung&chest wall tissue surface gliding past eachother (interpleural fluid significantly reduces friciton tho)
flow of air through the airways (80%!)
when is airflow resistance more sensitive to changes in radius
when its not laminar
what are the three different types of airflow
laminar, transitional, turbulent
what is laminar airflow
little airflow resistance
what is transitional airflow
resistance increases, extra energy to produce vertices
where is most transitional airflow
bronchial tree
where is most laminal airflow
small airways that are distal to terminal bronchioles
what is turbulent airflow
where the effective resistance to airflow is the highest
where is most turbulent airflow
in large airways (trachea, larynx, pharynx)
large radius
large linear air velocities
what kind of airflow in small airways
laminar
what kind of flow in trachea, larynx and pharynx
turbulent
what kind of airflow in bronchial tree
transitional
which kind of airflow does poiseuilles law
laminar flow
what is poiseuilles law
R=viscocity x length / radius^4
what is resistance to airflow most sensitive to (poiseuille)
change in radius
what is the total airway resistance in healthy subjects usually
1.5cm H2O/(L/s)
why is the resistance lower with bronchioles aligned rather than a few large ariways
because resistance in less in parallel than in a series
where does COPD have a dramatic increase in resistance (or other diseases)
in the smalllll airways (<2mm diameter)
why is there more resistance in small than large airways in disease states
smooth muscles contraction in walls
edema in walls of alveoli and bronchioles
mucus in bronchioles
