Respiratory Ventilation Flashcards
what are the two types of respiration taking place within the body?
external respiration: which takes the gases (fresh air) from the environment and brings them into the lung
internal respiration: taking the gases from the blood and using it in the cells during cellular respiration
what is external respiration?
(another name) & what does the process include
also called ventilation
- takes environmental air into the lungs via inspiration
- removes waste product of CO2 from alveoli back to the environment via expiration
structures within the conduit (conduction portion of the airway)
& their function
structures
- nose
- pharynx
- trachea
- bronchi
- terminal bronchioles
function
- low resistance pathway allows for easy flow to lungs
- moistens the air
-nose filters
- protects against and removes FB, particles, etc.
How is the tracho-bronchial tree set up? which zones are conducting? which zones are respiratory?
tracho-bronchial tree is a dichotomous tree – each branch becomes 2
conducting zone: zones 0-16 where gas is just passing though (no gas exchange)
respiratory zone: 17-23 where gas exchange occurs –> the respiratory bronchioles, alveolar ducts and alveolar sacs
** sacs = majority of gas exchange**
what is the respiratory portion of the airway?
& whats its function
structures
- respiratory bronchioles
- alveolar ducts
- alveolar sacs
- alveoli
function
- gas exchange
cell types within the alveoli
how do they interact with the capillary at the pulmonary interface?
- type 1 pneumocyte: responsible for the exchange of gas via diffusion
- type 2 pneumocyte: responsible for creating surfactant
Pulmonary interface –> connection between the basement membrane of the T1P and the capillary
- the basement membrane fuses with the capillary (THIN) to create this surface
** as large as a tennis court**
What forces are involved in ventilation?
ventilation: the force of moving air in and out of the lungs to effective reach the pulmonary interface
- muscles of respiration
- respiratory pressure
- surfactant
explain the muscles of respiration and how they work
- diaphragm
- pulls DOWN on inhalation - external intercostal muscles
- pull OUT on inhalation
Result: collectively allows lungs to inflate as chest expands
- diaphragm
- relaxes back up - internal intercostal muscles contract
- pulls in
- lungs recoil – where they want to be
Result: chest contracts down & lungs retract in
explain the driving force (law) behind the air flow of ventilation
- volume & pressure
Boyles Law –> with all else constant
- increasing volume –> decrease pressure
- decrease volume –> increase pressure
how is air pulled into and out of the lungs?
- think pressures and changes in pressures
- air will go from high pressure to low pressure –> want to create a lower pressure inside the alveoli to pull the air from atmosphere into the lungs
what are the relative pressures during inspiration
atmospheric pressure: 760 mmHg (pressure 0)
alveolar pressure: due to the contraction of muscles and increasing of the space (increase volume) –> decrease the pressure inside the alveoli (approx. -1 mmHg)
** thus, air will flow from the atmosphere into the lungs (alveoli) **
what are the relative pressures during expiration
atmospheric pressure: still 760 mmHG (pressure 0)
once the lung volume has reaching max capacity –> then muscle trigger to relax and the lung wants to collapse –> this triggers a decrease in volume –> thus triggering an increase in pressure (approx. +1 mmHg)
air flows from the alveoli to the atmosphere outwards
explain the mechanism of intrapleural pressure during inspiration and expiration
intrapleural pressure is always negative
(in healthy pts. approx. -4)
during inspiration:
- pleural space gets pulled with contraction of the muscles (increasing the potential space) therefore decreasing the pressure –> MORE NEGATIVE (approx. -6)
during expiration:
- the muscles relax, the space decreases in volume and therefore the pressure increases back to its baseline
** can vary from -2 –> -6**
explain what FRC is and how it’s maintained
whats it like in inspiration? expiration?
FRC: functional residual capactiy
- the starting point for breathing –> point at which your breathe is not in or out
- at this point: the pressure gradient is maintained because the force of the chest wall wants to pull out while force of the lungs wants to pull in – keeping them at a constant
- at end inspiration: the FRC is +.5 L (500 mL)
- at end expiration: back to 0
describe the pressures within a pneumothroax
- ** pneumothorax = the intrapleural pressure is = to atmospheric pressure**
- thus you loose the vacuum created to breathe
- lungs cannot maintain expansion & collapse
- uniliateral redcued ventilation
Explain the concept of lung compliance
what are the factors
lung compliance factors
- how easy the lung can inflate
- the amount of surface tension within the air-water interface of the alveoli
what are clinical correlations with lung compliance?
increased compliance: emphysema
- you have an increased ability to maintain an open airway because you’ve lost the elastic fibers of the connective tissue – but that becomes an issue because you cannot expell the air out
- alveoli walls are being destroyed so you additionally have a collapse of the alveoli & decreased gas exchange
decreased compliance: pulmonary fiberosis
- the walls of the alveoli are becoming more rigid and less elastic leading to the inability to inflate
how does surfactant work? what is its role in lung compliance
surfactant is a lipoprotein coating the internal alveoli surface (made by T2P)
decreases the surface tension within the alveoli
** surface tension arises because of the cohesive bonds between liquid molecules & their desire to contract**
too much contraction of the alveoli will collapse them –> surfactant works to ensure that they stay open (small)
stabilize the alveoli (keep small open and keep large from overinflating)
explain how increased fluid in the alveol will impact surface tension
increasing fluid within the alveoli (like pneumonia or CHF) will increase surface tension (between the air-water molecules) therefore causing the molecules to want to contract –> making it more difficult to breath
** would need pressures of -20 to -30 inside to drive respiration without surfactant**
surfactant and infants
- surfactant produced at the 7 1/2 month mark –> premi babies need ventilation to assist
- respiratory distress syndrome of the newborn will require artificial ventilation
what are the reliatve resistances to air flow by strucutre within the respiratory passage
(as percentages for each area of the respiratory tract)
nose: 50%
pharynx and larynx: 25%
chest airways: 25%
what physiological properties will impact the resistance to airflow
- MOST IMPORTANT: diameter of the conduit (think about asthma)
- length of the airway (longer = more resistance)
- smooth muscle tone (contracted = harder)
- gas property
what are some pathological changes that can happen to body that will increase resistance to airflow
- inflammation of the airway
- constriction of the airway
- buildup of mucus within the airway (or other substances)
how does asthma influence the resistance to airflow
- inflammatory state –> triggers mucus secretion in excess
- hyperresponsiveness of the airway –> smooth muscle contraction triggers decrease diameter of the airway
how is ventilation distrubted throughout the lungs
majority of ventiliation occurs at the base of the lung
- because of gravity, lung hanging in cavity, etc.
- maximal gas exchange occurrs here
as more ventilation is needed, upper lobes are recruited
explain the relationship between volumes and capacity
volume: amount of air (single quantity)
capacity: multiple volumes together
define tidal volume
the volume of air inspired in a normal breath
should be approx. 500 mL in healthly indivdual
define inspiratory reserve volume
the amount of air you can inspire (take in) after you have already inhaled regularly
the max amount of air inhaled possible
approx. 3100mL (3L)
define expiratory reserve volume
the amount of air you can breath out after you have already exhaled
the max amount you can exhale
approx. 2100 mL
define residual volume
the amount of air that will remain in the lungs after you have breathed everything out
it cannot be forced out
approx. 1200 mL
define vital capacity
capacitiy – added up volumes
vital — what you are able to do while living!!
tidal volume + inspiratory reserve volume + expiratory reserve volume = VC
define inspiratory capacity
the maximum amount of volume you can take in
tidal volume + inspiratory reserve volume = IC
define functional residual capactiy
the total amount of exhale (able to be exhaled or not)
expiratory reserve volume + residual volume
define total lung capactiy
sum of all volumes
tidal volume + inspiratory reserve + expiratory reserve + residual = 6000mL
when is pulmonary function testing conducted?
for lung diseases…
- obstructive diseases
- restrictive diseases
- mixed diseases
** in attempts to quantify the decrease in pulmonary function and ventilation**
what categorizes diseases as obstructive respiratory diseases
examples
- restriction in the air flow due to resistance
examples
- asthma (resistance from mucus, inflammation & decreased diameter)
- chronic bronchitis (increased mucus)
- cystic fibrosis (increase mucus)
- COPD ( CB and asthma)
- emphysema (airway collapse resulting in air trapping at low pressures)
what categorizes restrictive respiratory diseases
examples
decrease in pulmonary compliance (ability to inflate)
** so they require a greater force to ventilate**
examples
- respiratory distress syndrome (need more pressure)
- pulmonary fiberosis (fiberous tissue doesnt expand)
- scoliosis (need more force to move the bones)
when doing a pulmonary function test, what are the most important measurements to note
FVC: forced vital capacity (total amount of air expelled during the test)
** affected by age, gender and body height**
FEV1 = forced expiratory volume in 1 second
** should be a % of the FVC – normal is 70%**
in obstructed diseases FEV1 is 20-30%
the ration of FEV1/FVC is useful for obstructive disease measurements
what is the difference between anatomical and physiological dead space
anatomical: no gas exchange occurrs here (like the conducting spaces of the airway)
physiological: anatomical dead space but also areas where the surface has been damanged and can no longer exchange gas
what is minute alveolar ventilation (MAV)?
equation?
amount of air that reaches the alveoli per minute
MAV = RR x (TV - physiologic dead space)
normal MAV = 4.5 L
