Mechanics of Breathing, Pressures and Work Flashcards
What does ventilation mean?
- movement of air in and out of the lungs
What does respiration mean?
- gas exchange - respiratory and circulatory systems working together
What is external respiration?
- gas exchange outside of the lungs - mouth for example
What is cellular respiration?
- gas exchange at a cellular level - capillaries for example
What is lung compliance?
- the ability of the lungs to stretch - aim is to increase lung volume
What is elastic recoil?
- the resistance of the lungs to stretch - aim to passively force air out of lungs
Are the lungs more elastic of compliant?
- roughly equal
What is the formula for compliance?
- 🔼 volume / 🔼 pressure
What is the relationship between compliance and volume and pressure?
- direct relationship between volume + compression - indirect relationship between pressure + compression
What is the formula for elasticity?
- 🔼 pressure / 🔼 volume
What is the relationship between elasticity and volume and pressure?
- direct relationship between pressure + elasticity - indirect relationship between volume + elasticity
What is pulmonary fibrosis?
- parenchymal tissue replaced by stiff fibrous tissue
What does pulmonary fibrosis do to compliance and elasticity?
- ⬇️ in compliance - ⬆️ in elasticity - difficult to get air in so restrictive disease
What may neuronmuscular disorders do to the respiratory tract?
- lack of innervation to diaphragm and/or intercostal muscles - ⬇️ in compliance - ⬆️ in elasticity
Cystic fibrosis and bronchitis causes a build up in mucus in the lungs making it difficult to get air out of the lungs, meaning they are obstructive diseases, what do these conditions do to compliance and elasticity of the lungs?
- ⬆️ in compliance - ⬇️ in elasticity - air can enter but not leave
In children born prematurely, a lack of surfactant secretion in the lungs can cause the lungs to collapse, this is called infant respiratory syndrome. What does this do to compliance and elasticity of the lungs?
- ⬇️ in compliance - ⬆️ in elasticity - difficult to get air in
What is transpulmonary pressure?
- difference in pressure between alveoli and intrapleural pressure in the pleural cavity
What is transthoracic pressure?
- difference in pressure between the intrapleural pressure in the pleural cavity and the pressure at the body surface
What does transthoracic pressure represent in breathing?
- total pressure required to expand or contract the lungs and chest wall
What happens to the diaphragm during inspiration and exhalation?
- inspiration = diaphragm flattens ⬆️ volume in lungs - expiration = diaphragm curves ⬇️ volume in lungs
What happens to the abdominal muscles during inspiration and exhalation?
- inspiration = relax ⬆️ volume in lungs - expiration = contract ⬇️ volume in lungs
What are the main muscles involves in inspiration?
- diaphragm (75% change in the volume) - external intercostals (bucket handle) - accessory muscles (forced inspiration)
What are the 2 main accessory muscle used during forced inspiration?
- sternomastoid - scalenus
Where are the sternomastoid muscles used during forced inspiration?
- insert at the mastoid of cranium (near ear)
- origin at munubrium of sternum and medial clavicle
Where are the scalenus muscles used during forced inspiration?
- scalenus = greek for ladder
- 3 muscles (anterior, medial, posterior)
- attach at C4-C6 and ribs 1 and 2
What does Boyles law say in relation to pressure and volume?
- if pressure ⬆️ then volume ⬇️
- if volume ⬆️ then pressure ⬇️
What is intrapulmonary pressure?
- the pressure within the pleural cavity - essentially the lungs
What is intrapleural pressure?
- the pressure within the pleural space - between visceral and parietal pleura
What is atmospheric measure?
- pressure at sea level
As we inhale and increase the volume in the lungs, what happens to the intrapleural pressure?
- volume in lungs ⬆️
- intrapleural pressure ⬇️
- Boyles law = ⬆️ volume = ⬇️ pressure
What is the calculation for transpulmonary pressure?
- intrapulmonary pressure (in lungs)
- intrapleural pressure (in pleural space)
- 760mmHg - 756mmHg = 4mmHg during normal breathing
What is the calculation for transthoracic pressure?
- intrapleural pressure (pleural space) - atmospheric pressure
- 756mmHg - 760mmHg = -4mmHg during normal breathing
Generally, intrapleural pressure is always negative, how does the lung elasticity contribute towards this?
- wants to shrink and pull the lungs inwards - parietal pleura wants to pull out - ⬆️ volume = ⬇️ pressure - ⬇️ volume and ⬆️ pressure
Generally, intrapleural pressure is always negative, how does the lung surface tension contribute towards this?
- wants to shrink and pull the lungs inwards - ⬇️ volume and ⬆️ pressure
Generally, intrapleural pressure is always negative, how does the elasticity of the thoracic wall contribute towards this?
- wants to move outwards increasing pleural space and lung volume - ⬆️ volume and ⬇️ pressure
What will happen if there is too much fluid in the parietal space?
- it will increase intrapleural space - places pressure on lungs
How do the lungs maintain fluid in the parietal space?
- mesoethial cells secrete fluid - lymphatic capillaries drain fluid
What are the normal pressures we would expect during inspiration in the atmospheric, intrapulmonary and intrapleural space?
- atmospheric pressure = 760mmHg
- intrapulmonary pressure - 759mmHg
- intrapleural pressure = 756mmHg
What stops the pleural space and thoracic wall friction?
- visceral pleura
How can airway radius affect inspiration and expiration?
- large airways = lower resistance and breathing is fine - small airway = high resistance and difficulty breathing
What happens to the radius of airways during allergic reactions?
- airways become inflamed and swollen - radius ⬇️ and resistance ⬆️ = ⬇️ gas flow
What does the force required for inspiration need to overcome?
- elastic recoil
In the conducting zone, what is secreted on to the epithelial cells that can add resistance to the airway passing through?
- mucosa causes friction
What is airway resistance?
- difference in pressure between alveoli and mouth
- difference in pressure is then divided by flow
When calculating airway resistance, but you do not have flow, but you have resistance and pressure differences, what is the formula to calculate flow?
- flow = 🔼 pressure / resistance
What is the relationship between gas flow and pressure?
- direct association - if pressure ⬆️ = ⬆️ in flow - if pressure ⬇️ = ⬇️ in flow
What is the relationship between gas flow and resistance?
- inverse association - if resistance ⬆️ = ⬇️ in flow - if resistance ⬇️ = ⬆️ in flow
What is a generation in the respiratory tract?
- a division of the respiratory tract
- carina divides into left and right bronchi is a generation
On average, how many generations are in the respiratory tract?
- 23
What are the 2 terms used to describe different airflow through the respiratory tract?
- laminar (fluid and low resistance)
- turbulent (disrupted and increased resistance)
What is laminar flow in the respiratory tract?
- smooth flow with no resistance - proportional to the radius
What is turbulent flow in the respiratory tract?
- irregular flow with resistance - increased resistance
What is surface tension in the alveoli?
- H2O creates attractive forces (hydrogen bonds)
- strongest forces pull H20 molecules down
- at air/water interface water retreats downwards
Why are the bonds to the side and below H2O molecules stronger than those at the top of the H2O?
- H2O cannot bind with air
- makes bonds below and to the side stronger
- thus increasing surface tension
In instances where the surface tension is high in the alveoli, what does that do to the alveoli?
- H2O retracts pulling down towards the alveoli
- alveoli shrink and recoil into smallest possible size
- this increases the collapsing pressure of the alveoli
- poor gas exchange/perfusion takes place
What is the formula for calculating pressure in relation to surface tension and radius?
- P = pressure T = surface tension r = radius - P = 2T/r
What is the relationship between pressure and radius?
- inverse relationship - ⬆️ pressure = ⬇️ radius - ⬇️ pressure = ⬆️ radius
If surface tension is reduced, what happens to the pressure?
- ⬇️ in surface tension = ⬇️ in pressure - this reduces the risk of alveoli collapse
If surface tension increases, what happens to the pressure?
- ⬆️ in surface tension = ⬆️ in pressure - this increases the risk of alveoli collapse
What is surfactant?
- fatty acids and proteins
- dipalmitoyl phosphatidycholine (DPPC)
- dipalmitoyl = 2 (di) palmitic acid groups for tails
- phosphatidycholine = phosphate, choline, glycerole head
How does surfactant interact with H2O?
- surfactant is amphipathic (H20 loving and hating)
- dipalmitoyl tails are hydrophobic
- phosphatidycholine head is hydrophillic
How does surfactant reduce surface tension?
- head interacts with water at surface
- tails try to pull away from the water
- pulling away from water raises the water and reduces surface tension
In small and large alveoli, is the surfactant evenly distributed?
- no - small = yes - larger = surfactant is spread throughout
If the surfactant is not evenly distributed throughout, due to the differing sizes of the alveoli, the surface tension may be lower in small alveoli compared to larger alveoli. Why is this a good thing?
- helps maintain overall homeostasis of the lungs - balanced surface tension throughout
If the radius of the alveoli is small with limited surfactant, what does that mean for the pressure in the alveoli?
- ⬇️ radius = ⬆️ pressure
If the radius of the alveoli is small with sufficient surfactant, what does that mean for the pressure in the alveoli?
- ⬇️ radius + surfactant = ⬇️ pressure
What are the 2 main contributors to keeping alveoli open?
- transmural pressure gradient (intrapulmonary/intrapleural)
- pulmonary surfactant
What are the 2 main contributors that promote the collapse of the alveoli?
- elastic recoil of pulmonary tissue (alveoli)
- increased alveolar surface tension
What is Consideration of Work of Breathing?
- energy required to stretch elastic tissues of chest and lungs
- energy required to move air and non-elastic tissues through tubes
What is Consideration of Work of Breathing measured in?
- joules/litre
What are the 3 elastic work aspects of Consideration of Work of Breathing (energy required for breathing) measured in?
1 - respiratory muscles 2 - length/tension relationships 3 - fatigue
What are the 2 non-elastic work aspects of Consideration of Work of Breathing measured in?
1 - viscous resistance 2 - airway resistance
Using the 2 terms used to describe different airflow, turbulent and laminar, through the respiratory tract, what flow would patients with respiratory tract disease have?
- turbulent flow - rapid respiratory rate
What can happen in relation to Consideration of Work of Breathing (energy needed to breathe) in respiratory disease, which require a lot of energy to breathe?
- consideration in lungs is increased due ⬆️ repiratory rate
- increased elastic recoil also increases consideration
- increased consideration increases fatigue
- some patients may need a ventilator
What is tidal volume?
- what we inspire and expire at rest - aprox 500ml
What is inspiratory reserve volume?
- forced/maximal inspiration above tidal volume
- aprox 3000ml
What is expiratory reserve volume?
- forced expiration below tidal volume
- aprox 800-1200ml
What is residual volume?
- air remaining in lungs following forced expiration
- almost impossible to exhale all air
What is inspiration capacity?
- total inspiration capacity of lungs
- tidal volume + inspiratory reserve volume
What is functional residual volume?
- total expiration capacity of the lungs
- expiratory reserve volume + residual volume
What is vital capacity?
- total air that can be inhaled and expelled
- inspiratory reserve volume + expiratory reserve volume + tidal volume
