Module #2: Ventilation Flashcards by Suzanne Zick

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)

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Ventilation Rate

breaths per min

approx. 12/min

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Minute Ventilation

volume of air inspired/expired per minute

@ rest = ~6 L/min

minute ventilation = (alveolar ventilation + dead space ventilation) x Respiratory Rate (RR)

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Alveolar Ventilation

volume of air that reaches alveoli per minute

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Dead Space Ventilation

Volume of air that DOES NOT reach alveoli per minute

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What areas of the bran stem are involved in respiratory control?

Medulla and pons

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What is the respiratory center controlling?

respiratory muscle contraction and relaxation

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What are the respiratory groups in the medulla?

Dorsal Respiratory Group

Ventral Respiratory Group

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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

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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)

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What are the respiratory regions in the pons?

Pneumotaxic Center

Apneustic Center

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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)

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What other parts of the CNS can override or influence automatic ventilation?

motor cortex (voluntary movement)

hypothalamus

limbic system (stress/emotion)

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Which Respiratory center do lung receptors send impulses to?

DRG to influence rate of ventilation

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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

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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

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Hering-Breuer Expiratory Reflex

strech receptor reflex in newborns

helps maintain ventilation

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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)

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What do central and peripheral chemoreceptors monitor?

PaCO2

PaO2

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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

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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

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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)

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what is the relationship between central and peripheral receptors in healthy individuals?

central chemoreceptors more sensitive than peripheral; more sensitive to PaCO2 levels

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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

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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"