3 Respiratory Flashcards
What is the tidal volume?
Tidal volume is the amount of air inhaled or exhaled during a normal breath, AT REST
What is the inspiratory reserve volume? (IRV)
The maximum amount of air a person can inhale after taking a normal breath.
It represents the extra capacity of the lungs for deep inhalation beyond the typical tidal volume,
What is the expiratory reserve volume?
The maximum amount of air a person can exhale after completing a normal exhalation.
It represents the additional air that can be forcefully expelled from the lungs
What is the inspiratory capacity?
The maximum amount of air a person can inhale after a normal exhalation.
It is the sum of tidal volume and inspiratory reserve volume
TV + IRV = IC
What is the vital capacity?
The maximum amount of air a person can exhale after taking a deep breath in.
It is the sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume.
What is the functional residual capacity?
The amount of air remaining in the lungs after a normal exhalation.
It is the sum of expiratory reserve volume and residual volume
ERV + RV = FRC
What is the residual volume
The amount of air remaining in the lungs after a forceful exhalation.
It prevents lung collapse by maintaining air pressure within the lungs. This volume cannot be exhaled and is important for evaluating lung health and function in respiratory tests.
What is the total lung capacity?
The maximum amount of air the lungs can hold. It is the sum of all lung volumes: tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume.
TLC provides a comprehensive measure of lung size
Why, under moderate sedation, do children have a higher risk of becoming hypoxic?
Slower breathing rate = pO2 may drop and pCO2 may increase
Ventilation may be less
Children have smaller residual volumes than adults and a faster metabolic rate
So they use up oxygen more quickly, leading to hypoxia
What is the main difference between men and women’s ventilation volumes?
Main different is inspiratory reserve volume (IRV) = meaning they have a naturally larger lung capacity
How does tidal volume change depending on the activity?
During exercise, tidal volume recruits other lung volumes = IRV & ERV
Name 2 other factors affecting ventilation
Airway resistance
Lung compliance
What causes an increase in airway resistance?
Decrease in airway diameter
What happens when airway resistance increases?
Decreased airflow to lungs
What is the relationship between airflow and airway resistance?
Inversely correlated
When airway resistance is high = low air flow
When airway resistance is low = high air flow
What are some things that cause an increase in airway resistance?
Airway constriction (asthma)
External compression
Obstruction = mucus
Describe what happens to airways when there is an allergic reaction
Release of histamine occurs
Causes smooth muscle contraction of airway walls
Constriction of bronchioles
Increases resistance, decreasing airflow to restrict breathing
What is released to decrease airway resistance?
EPINEPHRINE released by adrenal medulla
Causes smooth muscle of airways to relax
This dilates bronchioles = reducing resistance
Increase to airflow = promotes gas exchange
Define lung compliance
Lung compliance refers to the ability of the lungs to expand and stretch when air is inhaled.
High compliance means the lungs can expand easily, while low compliance means they are stiff and harder to expand.
What factors does lung compliance depend on?
Extent elastic fibres can stretch
Surface tension within the alveoli
Mobility of thoracic cage
What affect do surfactants have on surface tension within alveolus?
Prevent alveoli collapsing
Thus, promoting lung expansion + increasing lung compliance
What can affect the mobility of the thoracic cage?
Arthritis
What does change in lung volume affect?
Change in airway pressure
What is the equation for respiratory minute ventilation?
Volume of air moved per minute = breaths/min x tidal volume
What is the equation for alveolar ventilation?
Alveolar ventilation = breaths/min x (tidal volume - dead space)
What is the difference between respiratory minute ventilation and alveolar ventilation?
Same equation but alveolar ventilation takes into account DEAD SPACE
What can cause changes in tidal volume and dead space?
Disease
If some part of alveoli cannot participate in gas exchange because of disease = they become dead space
If there is poor lung compliance = tidal volume decreases (because airway resistance increases)
Define dead space and give examples
Dead space does not participate in gas exchange
Bronchioles & trachae
It includes anatomical dead space (airways) and physiological dead space (areas with poor or no blood flow). Increased dead space reduces the efficiency of breathing.
What compensates for changes in dead space and tidal volume?
Breathing rate (breaths/min)
As per the equations of minute ventilation and alveolar ventilation
Except for when under influence of sedatives, alcohol, etc
Why is ventilation-perfusion coupling important?
Only occurs in lungs, pulmonary capillaries
If ventilation is high, but perfusion is low, or vice versa, gas exchange becomes inefficient.
This process optimizes oxygen delivery and carbon dioxide removal.
What two factors are regulated to control ventilation-perfusion coupling?
Airway diameter (bronchioles)
Pulmonary arterioles
What mechanism regulates bronchiole diameters in ventilation-perfusion coupling?
In regions with high airflow compared to local blood supply = decreased pCO2
Bronchioles constrict = reducing airflow so it’s proportional to blood flow
In regions with restricted airflow: increased pCO2 = bronchioles dilate
Increase in airflow enhances CO2 elimination from ALVEOLI, preventing build-up
What mechanism regulates pulmonary arterioles in ventilation-perfusion coupling?
In regions with high airflow compared to blood supply: increased pO2, causing local arterioles to dilate
More blood is made available for O2 to be picked up
In regions with restricted airflow: low pO2, causes pulmonary arterioles to constrict
Blood is re-channeled to alveoli w higher airflow and pO2, allowing more available O2 to be picked up
What part of brain controls ventilation?
Respiratory centres located within brainstems
Name the inspiratory neurones
Dorsal respiratory group
What is the average breathing rate?
12-20 breaths per minute
What is the role of the ventral respiratory group?
Function only during forced breathing
During normal, quiet breathing (eupnoea), expiration is typically a passive process that occurs as the inspiratory muscles relax, allowing the lungs to recoil. However, during active or forced expiration (such as when exercising or coughing), the VRG is involved in generating the necessary muscle contractions for active exhalation
How does ventral respiratory group control breathing?
Innervates lower motor neurones controlling accessory respiratory muscles
Increase in dorsal respiratory group (DRG) activity stimulates VRG neurones
What signals does the DRG integrate?
DRG integrates signals from VRG and pons
What is the role of pons in breathing?
Pons sends signals to DRG and VRG to modify respiratory rate and allow smooth transition between inspiration and expiration
What do central chemoreceptors sense, and what is the outcome?
They monitor pH that is dependent on CO2 levels in the brain
Send signals directly to respiratory centers to regulate ventialtion
Where are central chemoreceptors located?
Medulla
What do peripheral chemoreceptors sense, and what is the outcome?
Monitor pO2 mainly but also pH and pCO2 in the ARTERIAL BLOOD
Signal to respiratory centre via glossopharyngeal and vagus nerves
Where are peripheral chemoreceptors located?
Carotid bodies and aortic bodies
How is CO2 indicative of pH levels?
CO2 readily diffuses from blood into brain to combine with water = carbonic acid
Acid dissociates into H+ and HCO3- ions
H+ stimulates central chemoreceptors = sending nerve impulses to respiratory centres
How come the H+ is specific to pCO2 and not also affected by metabolic regions?
H+ cannot cross the BBB
Explain respiratory and metabolic ACIDOSIS
Resp system fails to remove CO2 (H+) normally generated by tissues (e.g decreased ventilation)
Tissues generate excess acid or kidneys fail to get rid of acid
Explain respiratory and metabolic ALKALOSIS
Resp system removes too much CO2(H+)
Maybe because of inappropriately increased ventilation
Body has lost acid or gained excess alkali from other systems
What causes depression of respiratory control centres?
Sedatives
Narcotic (opiod) drugs
Alcohol
Anaesthetics
How does voluntary control affect ventilation?
Act through cerebral cortex
Consciously control respiratory muscles to regulate breathing patterns
Can be overridden by chemoreceptor input to respiratory centres
What is CO2 narcosis?
When carbon dioxide (CO2) levels in the blood become excessively high, leading to respiratory acidosis.
Depresses CNS and ventilation even further
How do pain and emotions affect ventilation?
Act through hypothalamus
Stimulates or inhibits respiratory centres
ANS may also play a role = sympathetic stimulation can cause bronchodilation and increases respiratory rate through anticipation or fear
How do pulmonary irritants affect ventilation?
May stimulate receptors in the airways = initiate protective reflexes to remve irritants
Example = coughing and sneezing that involves apnea
Forced closing of glottis with full lungs and sudden contraction of internal intercostal and abdominal muscles
How does lung hyperinflation affect ventilation?
During deep inhalation, stretch receptors send inhibitory signals to inspiratory neurones at DRG
While stimulating expiratory centre of VRG to stop inspiration, begin expiration, and prevent over-stretching of lungs
Where are stretch receptors found to stop lung hyperinflation?
Visceral pleura
Smooth mucles around bronchioles
Large airways
How does deflation reflex affect ventilation?
During forced exhalation, receptors in alveolar wall of alveolar capillary network, sense decreasing lung volume
Respond by inhibiting expiratory centres and stimulating inspiratory centres = stop expiration and begin inspiration
Is ventilation during exercise, dependent on pO2 and pCO2?
No it is often independent
Other factors lead to increase in ventilation during exericse
Name 5 factors that lead to increase in ventilation during exercise
Anticipatory learned response
Signals from motor cortex
Proprioceptors in muscle and joints
Hormones such as epinephrine and norepinephrine
Lactic acid
