W1 - Respiratory Physiology (1-3) Flashcards
Name the 4 functions of the respiratory system
Gas exchange
Acid base balance
Protection from infection
Communication
Blood pH is regulated at what pH?
7.4
When we speak, are we inhaling, exhaling or both?
Exhale only
Provide the equation of life
Nutrients + O2 = ATP + Waste
Integration from what two things determine the ability to deliver fuel to cells and remove waste?
Integration from CVS
Integration from resp system
Name the 2 types of respiration and where they occur
Cellular/internal respiration in peripheral tissues
External respiration in lungs
Cellular/Internal respiration releases energy via which two processes?
Glycolysis
Oxidative phosphorylation
Oxidative phosphorylation requires which two things?
O2
External respiration
External respiration releases energy from what?
Glucose
Exercise causes working muscle to demand more energy. What 2 changes does it lead to in the body?
Increase rate and depth of breathing
Increase HR and force of contraction
Name the places Exchange I, II and III occur
Exchange I: between atmosphere and lung
Exchange II: between lung and blood
Exchange III: between blood and cells
In steady state, net volume of gas exchanged in lungs is equal to net volume of gas exchanged in tissues. How much ml per min?
250 ml / min of O2
200 ml / min of CO2
Describe the difference between pulmonary and systemic circulation in terms of location, CO2 and O2
Pulmonary - heart and lungs
Systemic - whole body
Pulmonary - deliver CO2 to lungs
Systemic - collect CO2 from tissues
Pulmonary - collect O2 from lungs
Systemic - deliver O2 to tissues
Which artery in the body carries deoxygenated blood and which vein carries oxygenated blood? In terms of definitions, why do these arteries/veins go against the norm?
Pulmonary artery/vein
Artery - carries blood away from heart
Vein - carries blood to heart
What is standard adult respiration rate and what is max during exercise?
12-18 breaths per min
40-45 max during exercise
Name the 7 main anatomical regions of the airways
Nose
Pharynx
Epiglottis
Trachea
Larynx
Lung
Bronchus
What is the function of the epiglottis?
Close during eating/drinking to prevent aspiration
Roughly how many times does the bronchi divide to become alveoli
Around 25x
What is the function of the larynx? What’s the lay term for larynx?
Contains vocal cords which vibrate to produce sound
Lay term is voice box
Name 2 reasons why it’s more comfortable to breathe through the nose rather than mouth. Why?
Nose warms and moistens air
Due to huge surface area to volume ratio
Where is the jugular notch and sternal angle? What’s inferior to the sternal angle?
If you run your fingers over your sternum, you find the jugular notch
About 2-3 fingers down is the sternal angle
Below is the trachea dividing into the 2 primary bronchi
Why are the lungs soft and spongy?
Thousands of tiny hollow air sacs
What 6 areas can be found in the upper respiratory tract?
Pharynx
Vocal cords
Oesophagus
Nasal cavity
Tongue
Larynx
What 3 areas can be found in the lower respiratory system? What 3 things surround them?
Trachea
Bronchi
Lungs
Surrounded by: ribs, spine, diaphragm
How many lobes, fissures and secondary bronchi do our right lung have? What about left?
Right: 3 lobes, 2 fissures, 3 secondary bronchi
Left: 2 lobes, 1 fissure, 2 secondary bronchi
What’s the name of the fissure found in both the right and left lung? What’s the name of the fissure only found on the right?
Right and left: Oblique fissure
Right only: Horizontal fissure
What 2 ways help us determine the right from left bronchus? Why is it clinically relavent?
R is wider
R has more vertical trajectory
Aspirated foreign bodies are more likely to get stuck in R
Define anatomical dead space
Air in trachea and bronchioles, where walls are too thick for gas exchange
Name the 6 anatomical regions from windpipe to terminal point in lung
Larynx
Trachea
Primary bronchus
Secondary bronchus
Bronchiole
Alveoli
Where does gas exchange occur
Alveoli in lungs
Define patency and name the feature that maintains it
Airway is open and air flows freely
Provided by semi-rigid tubes in airway, created by C-shaped rings of cartilage
The bronchiole does not have C-shaped rings of cartilage. How is patency maintained?
Physical forces in thorax
What 2 things surround alveoli?
Elastic fibres
Network of capillaries
Does expiration need energy? What happens to alveoli?
It is passive and so does not need energy
The inspiration muscles stop contracting and energy in elastic fibres is released, squeezing alveoli to force air out
What are type 1 and type 2 alveolar cells?
Type 1 - gas exchange occurs here. More common. Capillaries are only abutted to type 1
Type 2 - secrete surfactant
What type of immune cell can be found near alveoli?
Macrophages - important since site is not sterile
Explain the relationship between airway diameter, resistance and the sympathetic nervous system
The smaller the airway, the less resistance due to a larger surface area. As airways merge, there are more particles in proportionally less space, causing resistance
Sympathetic nervous system causes bronchial smooth muscle relaxation
- Relaxation increases diameter = decreases resistance
- Contraction decreases diameter = increases resistance
Bronchial smooth muscle relaxation is caused by what binding to what receptors?
Adrenaline/noradrenaline binding to beta-2 receptors
What is the surface area of the alveoli? What value is total lung capacity?
Surface area: 80m2
Volume: 2 x 3l lungs
Most resistance to air flow happens in what areas of the lungs? What is the cross-section area?
Trachea, primary and smaller bronchi - between 0-11 divisions. They have a cross-section area of 2.5cm
In what 2 ways is residual volume beneficial?
Prevents alveoli from completely collapsing, which would require a lot of energy to “reboot”
Allows gas exchange between breaths
Define inspiratory capacity. What two values make it? What is the normal value?
Inspiratory capacity - normal air in the lungs after inspiration
Tidal volume + Inspiratory Reserve Volume = Inspiratory Capacity
Usually it’s 2.8 litres
How many litres is total lung capacity? Which two values is it made of?
6 litres
Vital capacity + residual volume = total lung capacity
Define tidal volume and give its typical value
Tidal volume is the air we breathe in and out
It’s around 500 ml
Define functional residual capacity. What two things is it made of and what’s the typical value?
Functional residual capacity is the total left in lungs after expiration
Expiratory reserve volume + residual volume = functional residual capacity
It’s 2.3 litres
Define inspiratory reserve volume and provide a value
Taking a big breath, e.g. exercise
3 litres
Define expiratory reserve volume and provide a value
Big breath out
Roughly 1 litre
Define vital capacity and the three values that make it
Deep breath in then pushing as much air out as possible
Tidal volume + Inspiratory Reserve Volume + Expiratory Reserve Volume = Vital Capcity
Define residual volume and provide a value
Air you can’t voluntarily remove
Around 1.2 litres
What is FEV1FVC?
Fraction of forced vital capacity expired in 1 second
Define dead space volume and provide a value
The volume of gas occupied by the conducting airways which is not available for exchange.
150 ml
Each lung is surrounded by a continuous pleural membrane. Name the two aspects and give their locations
Parietal membrane - stuck to ribs and diaphragm
Visceral membrane - stuck to surface of lungs including all fissures
Define hilum and its relevance for the membrane
The hilum of the lungs are where lungs connect to the major airway entering/leaving lungs, pulmonary artery and vein
It’s where the parietal membrane doubles back on itself to become the visceral membrane (or vice versa!)
Boyle’s Law
The pressure exerted by a gas is inversely proportional to its volume
P = 1/V
Dalton’s Law
The total pressure of a gas mixture is the sum of the pressures of individual gasses
Charles Law
The volume occupied by a gas is directly related to absolute temperature
v = T
Henry’s Law
The amount of gas dissolved in a liquid is determined by the pressure of the gas and its solubility in liquid
Where is intrapleural fluid? What 3 functions does it serve? How many ml is it?
Between visceral and parietal membranes
- Allow membranes to glide over each other
- stops separation which allows for lung expansion during isnpiration
- prevents recoil of lungs and too much chest wall expansion during expiration
3ml in each lung
Relate Boyle’s law of the mechanics of breathing, inspiration and exparation
Breathing occurs because the thoracic cavity changes volume
Based on Boyle’s law:
Increased volume = decreased pressure
Decreased volume = increased pressure
Gasses always move from high pressure to low pressure
Which muscles do we use during inspiration, heavy inspiration, expiration and heavy expiration?
Normal Inspiration: External intercostal muscles, diaphragm
Heavy Inspiration: Scalene Muscles, Sternocleidomastoid muscles (and above)
Normal Expiration: None - its passive
Heavy Expiration: Internal intercostal, abdominal muscles
Describe the action of the diaphragm, thoracic volume and airways during inspiration and expiration
Inspiration: Diaphragm contracts, thoracic volume increases, airways are pulled open
Expiration: Diaphragm relaxes, thoracic volume decreases, airways are compressed
What 2 metaphors are used to describe the action of the ribs during breathing?
Pump handle motion - increases anterior-posterior dimension of the rib cage
Bucket handle motion - increases lateral dimension of rib cage
Name the 3 pressures in the thoracic cavity and whether they’re positive or negative in healthy lungs compared to atmospheric pressure
Intrathoracic pressure - pressure in thoracic cavity. Positive/negative
Intrapleural pressure - pressure in pleural cavity. Negative
Transpulmonary pressure - alveolar pressure minus intrapleural pressure. Negative
Explain why intrapleural pressure is always less than alveolar pressure
Intrapleural pressure is less than atmospheric pressure and becomes more negative during inspiration, due to expansion between the parietal and visceral pleura. If intrapleural pressure were higher than alveolar pressure, inspiration would be difficult or the lung could collapse.
What 4 mechanical factors affect respiratory minute volume?
Airflow between atmosphere and alveoli: Proportional to pressure difference (Patm - PA) and inversely proportional to airway resistance (F = (Patm- PA)/R)
End of unforced expiration: Stable lung and thoracic cage dimensions with opposing elastic forces.
Lung’s attempt to recoil vs. chest wall’s attempt to move outward creates subatmospheric intrapleural pressure and transpulmonary pressure.
Airway resistance majorly determined by airway radii, impacting airflow at varying pressure differences.
What makes surfactant?
What is it? Is it more effective in smaller or bigger alveoli?
What 4 functions does it have?
Type II alveolar cells
Detergent-like fluid
More effective in small alveoli as surfactant molecules come closer together so are more concentrated
Functions:
-Reduces surface tension, reducing tendency of alveoli to collapse
-Increases lung compliance
-Reduces lung’s tendency to recoil
-Makes work of breathing easier
In the foetus, when does surfactant production occur? What 2 hormones stimulate it? What may premies suffer due to a lack of surfactant?
25-36 weeks in utero
Thyroid and cortisol
Infant Respiratory Distress Syndrome (IRDS)
What is the Law of LaPlace?
Pressure = 2 x surface tension / radius
Pressure is greater in smaller alveoli. Surfactant reduces surface tension. Pressure is equalised in larger and smaller alveoli
Define compliance
Change in volume relative to change in pressure, i.e. how much does volume change for any given change in pressure. It’s stretchability or distensibility (not elasticity. People with emphysema have compliant but not elastic lungs)
Define high compliance and low compliance
High compliance - large increase in lung volume for small decrease in ip pressure. It’s good if accompanied by high elasticity
Low compliance - small increase in lung volume for large decrease in ip pressure. You have to work hard to get air into lungs. Can be caused by fibrosis
What 3 factors affect compliance?
Age - as we get older compliance decreases
Fibrosis
Surfactant - surfactant reduces surface tension which reduces likelihood of alveolar collapse
Define ventilation, pulmonary ventilation and alveolar ventilation
Ventilation - movement of air in and out of lungs
Pulmonary ventilation - total air movement into/out of lungs
Alveolar ventilation - fresh air getting to alveoli, therefore available for gas exhange
In what unit are pulmonary ventilation and alveolar ventilation measured?
L/min
Describe the impact of dead space on alveolar ventilation
Breathing is only around 70% efficient - the rest of the air is stuck in dead space and can’t participate in gas exchange
If we reduce TV and keep dead space the same, dead space is a bigger proportion of lung space. So for someone anxious, breathing is around 50% efficient.
If we increase TV and keep dead space the same, dead space is a smaller proportion of lung space. So for someone chill, breathing is around 80% efficient.
Is someone anxious likely to be hypoventilating or hyperventilating? What about someone chilled out? Which is more efficient? Which is more common in a clinical setting?
Anxious - hypoventilating
Chilled - hyperventilating
(contrary to popular belief)
Hyperventilation is more efficient
Hypoventilation is more common than hyperventilation as hyperventilation requires consciously overcoming the brain telling you there’s no CO2 to get rid of
Air is roughly what % nitrogen, oxygen and CO2?
79% nitrogen
21% oxygen
0.03% carbon dioxide
Define partial pressure. Whose law does it derive from?
The pressure of a gas in a mix of gases is equivalent to the % of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture
From Dalton’s Law
What are the PO2 and PCO2 values in mmHg and kPa for the ideal man?
PO2
100 mmHg
13.3 kPa
PCO2
40 mmHg
5.3 kPa
Does the ideal PO2 and PCO2 rise or fall if hypoventilating (anxious)? How about chilled (hyperventilating)?
Hypoventilating
PO2 falls
PCO2 rises
Hyperventilating
PO2 rises
PCO2 falls
Describe how pressure-volume varies between apex and base of lung. How would this differ for a patient lying down?
At base, the volume change is greater for a given change in pressure
Alveolar ventilation is greater at the base and lower at the apex
Compliance is lower at apex due to more inflation at FRC. At base lungs are slightly compressed by diaphragm so more compliant on inspiration
Small changes in intrapleural pressure brings about large change in volume at base compared with apex
If patient is lying down, they’ll have more compliance and ventilation at the back of the lung compared to the front
Define the following abbreviations used to describe partial pressure of gasses in alveoli, systemic arteries and veins
A
a
ṽ
P
PaO2
PACO2
A - alveolar
a - arterial blood
ṽ - mixed venous blood (pulmonary artery or large veins in body)
P - partial pressure
PaO2 - partial pressure of oxygen in arterial blood
PACO2 - partial pressure of CO2 in alveolar air
What do the pulmonary artery and vein carry?
Pulmonary artery - carries deoxygenated blood to lungs
Pulmonary vein - carries oxygenated blood away from lungs
What do bronchial arteries carry? What % of left heart output is it? Where and via what does blood drain to?
Bronchial arteries carry oxygenated blood to lung tissues from systemic circulation. Comprises 2% of left heart output. Blood drains to left atrium via pulmonary veins
How does pulmonary circulation work for gas exchange?
L & R pulmonary arteries from right ventricle. Entire cardiac output from RV. Supplies the dense capillary network surrounding alveoli and returns oxygenated blood to left atrium via pulmonary vein. It’s a high flow, low pressure system: (24/10mmHg vs 120/80mmHg)
What 5 factors affect the rate of diffusion across a membrane?
- Partial pressure gradient (directly proportional)
- Gas solubility since CO2 is more soluble in water than O2 (directly proportional)
- Available surface area (directly proportional)
- Thickness of membrane (inversely proportional)
- Distance as it’s most rapid over short distances
Define obstructive and restrictive lung disease
Obstructive - obstruction of air flow, especially on expiration
Restrictive - restriction of lung expansion leading to loss of lung compliance
Describe why the line showing inspiration and line showing expiration are not super-imposed on a pressure-volume relationship and compliance graph
Inspiration requires a greater change in pressure (from FRC) to reach a particular lung volume.
During expiration, volume is maintained. This is because:
- Overcome lung inertia during inspiration
- Overcome surface tension during inspiration
- During expiration compression of the airways means more pressure is required for air to flow along them
