Lesson 4: Respiratory Mechanics Flashcards
the interrelationship among pressure between what is important in ventilation?
interrelationships among pressure inside and outside the lungs are important in ventilation
what are the four different pressure considerations important in ventilation?
- atmospheric (barometric) pressure
- alveolar pressure
- pleural pressure
- transpulmonary pressure
what drives air in and out of the lungs, ad also drives gas exchange?
the difference in pressures and the changes in the pressures that changes lung volume
what is respiratory mechanics by definition?
interrelationships among pressures inside and outside the lungs that are critical to generate ventilation or movement of air
what is atmospheric pressure?
the pressure pushing down on us just in the room
- roughly 760millometres of mercury at sea level (mmHg)
*** as we climb a mountain, does atmospheric pressure go up or down?
it goes down
what is alveolar pressure?
the pressure inside the alveoli
- the pressure changes depending on what part of respiration you are on
what is pleural pressure?
the pressure in the pleural space
when we take a little breath in to relax, what is the pleural pressure like compared to the atmosphere?
it is lower
- negative pressure because we are pulling it open
what is pleural pressure generally considered?
the intrathoracic pressure representing the pressure in the thoracic cavity (they are typically very close in pressures)
what is transpulmonary pressure?
the difference between the alveolar and pleural pressure
- the pressure across the visceral pleura
when we take a little breath in to relax, what is the transpulmonary pressure like compared to the atmosphere?
gets bigger
what is another name for the transpulmonary pressure?
the recoil pressure
what do we have to create when we want to move something like air or fluid?
a pressure gradients
the larger the gradient in pressure, the ________ the air is going to move in and out
faster
atmospheric pressure diminishes with ____________ altitude as the layer of air above Earth’s surface decreases in thickness
increasing
when we talk about pressures, what are we talking about it in relation to?
atmospheric pressure
(ex. We can 0 atmospheric pressure so pleural is -2 from atmospheric) ( used to say pleaural is 758 when atmosphere is 760)
what is another name for alveolar pressure?
intrapulmonary pressure
when there is no pressure gradient to move along, is there still air flow?
no there is not
- we depend on pressure to move air in and out
what is cmH20 a unit of?
pressure
how can we measure pleural pressure considering we cannot stick a prob without rupture?
we can estimate by looking at other metrics such as the esophagus because pleural pressure closely approximates the intrathoracic pressure
what does transmural pressure mean?
pressure across something
what are the two types of transmural pressures?
- transpulmonary: the difference across the lung wall
- trans wall pressure: the difference across the chest wall
- we only care about #1
what is the equation for the transpulmonary pressure?
alveolar pressure - pleural pressure = transpulmonary pressure
what does transpulmonary pressure represent?
the recoil of the lung
our alveoli want to collapse but what avoids it?
the pleural pressure
when we take a breath in, what happens to our pleural pressure? what about alveolar pressure?
pleural pressure = drops heavily
alveolar pressure = drops to a lesser extent
transpulmonary pressure = large increase
what determines pressure in regards to air?
1 is key when we are talking about respiratory
- volume (size of “container”)
- temperature: constant for breathing
- number of molecules
what does Boyle’s Law state?
P1V1=P2V2
(pressure and volume)
- pressure and volume are highly dependent
what do we need to do in order to make air move?
pressures need to change
what do ventilators do?
they take air and push air in. they create the pressure gradient from the outside
what is Poiseuilles Law of Flow?
the magnitude of flow is dependent on the change in pressure as a function o the resistance of the system
F = delta P/R
essentially: if I want flow, I need a pressure gradient
negative flow means?
air is moving into the lung (inspiration)
which pressure, during inspiration, pulls the alveoli open such that the alveolar pressure drops a bit?
when we create a negative pleural pressure
we change the intrathoracic pressure in inspiration such that?
it drops the alveolar pressure to pull air in
review changes in lung volume and alveolar and pleural pressures during inspiration and expiration
wed january 15 lecture
