Module #2: Ventilation Flashcards
What is the difference between Ventilation and respiration?
Ventilation = mechanical process of bringing air into lungs
Respiration = gas exchange that occurs in lungs (@ alveoli) and throughout the body (target tissues/capillaries)
Ventilation Rate
breaths per min
approx. 12/min
Minute Ventilation
volume of air inspired/expired per minute
@ rest = ~6 L/min
minute ventilation = (alveolar ventilation + dead space ventilation) x Respiratory Rate (RR)
Alveolar Ventilation
volume of air that reaches alveoli per minute
Dead Space Ventilation
Volume of air that DOES NOT reach alveoli per minute
What areas of the bran stem are involved in respiratory control?
Medulla and pons
What is the respiratory center controlling?
respiratory muscle contraction and relaxation
What are the respiratory groups in the medulla?
Dorsal Respiratory Group
Ventral Respiratory Group
Describe the Dorsal Respiratory Group (DRG) in the Medulla:
Which respiratory action is it working on?
What is its function?
Wo is it receiving inputs from?
works on inspiratory actions
sets AUTOMATIC rhythm of breathing
receives input from respiratory receptors (peripheral and central chemoreceptors/lung receptors); mechanism for blood CO2 and O2 levels to influence rate of ventilation
Describe the Ventral Respiratory Group (VRG) in the Medulla
Which respiratory action is it working on?
What is its function?
works on both inspiratory and expiratory actions
active when increased ventilation is required (quiet during rest)
What are the respiratory regions in the pons?
Pneumotaxic Center
Apneustic Center
What is the function of the Pneumotaxic and Apneustic Centers?
modify depth and rate of inspiration that has been set by medullary centers (DRG and VRG)
What other parts of the CNS can override or influence automatic ventilation?
motor cortex (voluntary movement)
hypothalamus
limbic system (stress/emotion)
Which Respiratory center do lung receptors send impulses to?
DRG to influence rate of ventilation
Describe Irritant Receptors
Location, stimuli, Action
Locatedin epithelium of conducting airways (mostly larger proximal airways)
Stimulated by noxious gases, particles, etc
Action: cough reflex, initiate bronchoconstriction of airway, increase ventilation rate via DRG
Describe Stretch Receptors
Location, stimuli, Action
Located in smooth muscle of conducting airways
Stimulated by stretch (takes a lot to activate in adults) primary in newborns
Decreases ventilation rate and volume via DRG
Protective mechanism
Hering-Breuer Expiratory Reflex
strech receptor reflex in newborns
helps maintain ventilation
Describe Juxtapulmonary Capillary (J) Receptors
Location, stimuli, Action
located near alveolar septum of capillaries
stimulated by elevated pulmonary capillary pressure
results in rapid, shallow breathing (also influences cardiovascular system; decrease HR, decrease BP)
What do central and peripheral chemoreceptors monitor?
pH
PaCO2
PaO2
Describe Central Chemoreceptors
Location, stimuli, Action
located in brainstem close to respiratory centers
Stimulus: monitor pH of CSF which indirectly monitors CO2 levels of arterial blood; are activated by pH decreases (means PaCO2 is increasing)
Action: stimulate respiratory centers to increase ventilation rate and depth –> blow off CO2
Misc: plays important role in acid-base compensation
Describe relationship between pH of CSF and CO2 in blood
CO2 can DIRECTLY cross BBB; H+ CAN NOT
CO2 in brain will combine w/ H2O –> carbonic acid which then dissociates into H+ + bicarbonate
when you INCREASE H+ you DECREASE pH
Describe Peripheral Chemoreceptors
Location, stimuli, Action
located in carotid body (where CCA splits into ICA and ECA) and aortic body (arch of aorta)
Stimulated by changes in PaO2; respond to hypoxic conditions
Action: increase ventilation via DRG
Misc: plays important role in acclimatization to altitude (chronic hypoxia)
what is the relationship between central and peripheral receptors in healthy individuals?
central chemoreceptors more sensitive than peripheral; more sensitive to PaCO2 levels
what is the relationship between central and peripheral receptors in individuals suffering from pulmonary disease state?
chronic hypoventilation causes central chemoreceptors to become less sensitive
peripheral receptors take over role of regulating ventilation
What muscles are involved in respiration during rest?
diaphragm
external intercostal muscles
What accessory muscles are involved in respiration during exercise/disease?
SCM/scalenes
What muscles are involved in expiration during rest?
No major muscles are involved
diaphragm relaxes and elastic recoil of lungs dominate
What accessory muscles are involved in expiration during exercise/disease?
abdominals
internal intercostals
What is the purpose of surfactant?
lowers surface tension in alveoli –> allows alveoli to expand
What is the consequence of increased surface tension in alveoli?
it makes it more difficult for alveoli to expand
Describe the relationship of surfactant and alveoli diameter
small radius –> surfactant makes it easier for alveoli to expand
large radius –> surfactant makes it harder to expand
What is the consequences of inadequate surfactant?
surface tension increases –> alveoli collapse
decreased lung expansion
increase work of breathing
poor gas exchange
What is the lung disease that effects premature infants?
Infant Respiratory Distress Syndrome (IRDS)
they have inadequate surfactant production; hard for them to breath
How much is the Work of Breathing in a healthy individual?
Very low
How much is the work of breathing in an individual suffering from respiratory disease?
significantly increased
lead to chronic adaptation w/ hypertrophied accessory muscles (SCM/Scalenes)
What is the Atmospheric pressure (barometric pressure)?
760 mmHg @ sea level
will decrease w/ elevation
What is Partial Pressure?
pressure of individual gases w/in total air pressure
PaX = % concentration X x Total pressure of gas
What is the partial pressure of O2 in atmospheric air? (PaO2)
159 mmHg
PaO2 = .209 (percentage of O2 in atmospheric air) x 760 mmHg (total atmospheric pressure)
What is the partial pressure of CO2 in atmospheric air?
.23 mmHg
PaCO2 = .0003 (percentage of CO2 in atmospheric air) x 760 mmHg (total atmospheric pressure)
How is gas exchange drive in the lungs?
driven by pressure gradients
How is the air pressure different in the respiratory system as compared to atmospheric air?
the air pressure in the lungs is LESS than the atmospheric air
total pressure decreased when air is warmed/humidified in upper respiratory tract
How is the PaO2 different in alveoli vs pulmonary capillaries and what does that mean?
PaO2 is higher in alveoli than pulmonary capillaries
means O2 will diffuse from alveoli into pulmonary capillaries
How is PaCO2 different in alveoli vs pulmonary capillaries and what does that mean?
PaCO2 is lower in alveoli than pulmonary capillaries
means CO2 will diffuse from pulmonary capillaries into alveoli
What is the total pressure in respiratory tract?
713 mmHg
PaH2O vapor in respiratory tract = 47 mmHg
760 mmHg - 47 mmHg = 713 mmHg
What are the partial pressures of O2 and CO2 in trachea?
PaO2 = 149 mmHg
PaO2 = .209 (% of O2 in air in trachea) x 713 mmHg (total pressure of air in trachea)
PaCO2 = .21 mmHg
PaCO2 = .0003 (% CO2 in air in trachea) x 713 mmHg (total pressure of air in trachea)
What are the partial pressures of O2 and CO2 in alveoli?
PaO2 = 103 mmHg
PaO2 = .145 (% O2 in air in alveoli) x 713 mmHg (total pressure of air in alveoli)
PaCO2 = 39 mmHg
PaCO2 = .055 (% CO2 in air in alveoli) x 713 mmHg (total pressure of air in alveoli)
Tidal Volume (TV)
Volume of air inspired or expired w/ each normal breath
500 mL
Inspiratory Reserve Volume (IRV)
Volume of air that can be inspired over and above tidal volume
3000 - 3300 mL
Expiratory Reserve Volume (ERV)
volume of air that be expired after expiration @ total volume
1000 - 1200 mL
Reserve Volume (aka Residual Lung Volume) (RV)
Volume of air that remains in lungs after max expiration
1200 mL
CAN’T be measured by spirometry
Forced Vital Capacity (FVC)
Volume of air that can be forcibly expired after max inspiration
TV + IRV + ERV = (F?)VC
4500 - 5000 mL
Total Lung Capacity (TLC)
sum of all 4 lung volumes
VC + RV = TLC
5700 - 6000 mL
CAN’T BE MEASURED by spirometry
FEV1 = Forced Expiratory Volume
Volume of air that is measured during first second expiration
FEV1:FVC ratio
% of FVC that can be expired in 1 second
Normal = 70 - 90%
Average = 85%
FEV1:FVC in obstructive disease
decreases (<70%)
FEV1:FVC in restrictive disease
increases (>90% or no change)
Minute Ventilation (Ve)
volume of air expired in 1 minute
Respiratory Rate (RR) x Tidal Volume (TV)
@ Rest = 6 L/min
12 breaths/min x 500 mL
How can you increase Minute Ventilation?
Increase RR or Increase TV
Maximum minute Ventilation (Max Ve)
max volume of air moved in/out of lungs during max exercise
measured during stress test
will be 60-70% of Max Voluntary Ventilation (MVV)
Maximum Voluntary Ventilation (MVV)
max volume of air that can be moved in and out of lungs in 60 seconds
measure for 15 s then x 4
usually higher than Max Ve
How would you expect MVV to change in a pt that has an obstructive disease
will be 40% of expected normal for their size/weight/sex
Is ventilation a limited factor of exercise?
No, Max Voluntary Ventilation is 25% higher than exercise ventilation
Forced Expiratory Flow Rate (FEF25-75%) aka max midexpiratory flow rate (MMEFR)
middle portion of FEV
What is the relationship between exercise and lung volumes/capacities?
measures of lung volumes/capacities are a poor predictor of athletic performance/fitness
but is useful in predicting disease/dysfunction
What population will benefit more from exercise?
people w/ pulmonary diseases will see beneficial effect on static/dynamic lung volumes
Clinically what will a change in FVC suggest?
reduced FVC suggests restrictive disease
Clincially what will change in FEV1:FVC ratio suggest?
< normal value suggests obstructive disease
> normal value suggests restrictive disease
Clinically what will a change in FEV25-75% suggest?
< normal can be early indicator of obstructive disease
low w/ normal FEV1 associated w/ asthma severity in kids
Clnically what will a change in TLC suggest?
> normal suggests obstructive disease
< normal suggests restrictive disease
Clinically what will a change in MVV suggest?
suggested to represent “strength”
