W25 The Respiratory System Flashcards
What are the main functions of the respiratory system? (4)
- Ventilation (The movement of air into and out of the lungs)
- External Respiration: Exchange of oxygen (O2) and carbon dioxide (CO2) between the air in the lungs and the blood.
- Transport of O2 and CO2 in the blood
- Internal Respiration: Exchange of O2 and CO2 between the blood and the tissues
What are some other functions of the respiratory system?
- Regulation of blood pH- Altering blood CO2 levels
- Voice production- Air movement past the vocal cords
- Olfaction- Airborne molecules are drawn into the nasal cavity
- Innate immunity- Protects against certain microorganisms and other pathogens - preventing them from entering the body and by removing them from respiratory surfaces
What is the respiratory system responsible for?
What does it consist of?
It exchanges O2 and CO2 between the air and the blood.
Consists of respiratory passages and lungs
Conducting zone and respiratory zone
What are the structures of the respiratory system?
Upper respiratory tract? (3)
Lower respiratory tract? (3)
Upper respiratory tract
* Nose and nasal cavity- Air enters (also through the mouth)
* Pharynx (throat)
* Larynx
-maintains an open airway
-protects the airway during swallowing (epiglottis)
-produces the voice
Lower respiratory tract
-trachea
-bronchi
-lungs
Features of the lungs:
Where are they situated?
- Within the thoracic cavity
- 2 lungs
-Separated by the mediastinum in which the heart is situated - Each lung is divided into lobes
- Left lung – 2 lobes (upper and lower)
- Right lung – 3 lobes (upper, middle and lower)
- Heart sits within the ‘cardiac notch’ so the left lung is slightly narrower
- Each lung: Surrounded by a pleural cavity
-Formed by 2 pleural membranes- the visceral and parietal pleurae - Passages branch
- Decrease in size
- Increase in number
What are cilia?
They line the surface of the lower respiratory tract
They beat upwards and drives the debris
What structure protects the respiratory tract when you swallow?
Epiglottis
Which structures are part of the conducting zone?
- Alveoli
- Terminal bronchioles
- Respiratory bronchioles
- Primary bronchi
- Alveolar ducts
Terminal bronchioles and Primary bronchi
Which structures are part of the respiratory zones? (3)
Alveoli
Respiratory bronchioles
Alveolar ducts
What are the 2 phases of Ventilation?
What is is regulated by?
What is air flow driven by?
- Inhalation (inspiration)
- Exhalation (expiration)
- Changes in thoracic volume (drives)
-pressure changes
Air flow is driven by the pressure difference between
* the atmosphere (barometric pressure)
* inside the lungs (intrapulmonary pressure)
What are the features of the diaphragm?
- 70 % ventilation
- Dome shaped
- Contracts
- Downwards and flattens
- (increasing thoracic cavity)
- Relaxes
- Recoils upwards
- (reducing thoracic cavity)
- Only respiratory muscle working when lying flat and sleeping
What are the features of the Intercostal Muscles?
- Between ribs
- Two planes of muscular and tendinous fibres occupying each intercostal space* Internal beneath external
- The external intercostal muscles * slope downwards and forward
- Contract: ribs upwards and outward
- Elevates ribs and sternum
- The internal intercostal muscles * Opposite direction
- Contract: lower ribs
- Stability
Forced breathing (During exercise or when you are breathing more forcefully):
- Muscles contract more forcefully
- Others also contract
- Scalene muscles
- Sternocleidomastoid
- Pectoral muscles
What is inspiration?
What are the steps?
Quiet breathing (in)
* Diaphragm contracts
* External intercostals- Contract
- Signals from the respiratory centre in the medulla oblongata (brain stem)
- Contraction of the diaphragm and intercostal muscles leading to the diaphragm moving downward
- Transverse expansion of thoracic cavity
- Vertical expansion of thoracic cavity
- Lung volume increases and the intra-alveolar pressure decreases
- Air is sucked in (inhalation)
What are conducting airways/zones?
What do they consist of?
- Strictly for ventilation
- The trachea (windpipe)
-Cartilage
-Splits into: - Left and right bronchi
- When an airway divides it always divides into 2 (bifurcation)
What does the bronchial tree consist of?
Bronchial tree
* Left and right bronchi (one bronchus) or primary bronchi divide
* Secondary bronchi (in lobes of lung) - divide
* Tertiary bronchi - divide
* Bronchioles – divide (several times)
* Terminal bronchioles
- Top of tree
-Lots of cartilage some smooth muscle
-Keep airways open
Bottom of tree
-Lots of smooth muscle less cartilage
-Change diameter of airways Bronchial tree
What does the respiratory zone consist of?
- Respiratory bronchioles * (few alveoli) attached
- become alveolar ducts
- 2/3 alveolar sacs
Alveoli
* Air-filled sacs
* Membrane v elastic- Expand / contract
* Surrounded by a capillary network to provide efficient gas exchange
* The respiratory membrane
-Where gas exchange between the air and blood takes place
-Very very thin
What are the types of alveoli? (3)
- Type 1 alveolar cells (95%) form the alveolar wall
- permit gas exchange - Type 2 alveolar cells secrete surfactant
-Defence
-Role in breathing and stabilises alveoli (surface tension)
-Recoil of lungs - Alveolar macrophages
-Defence against foreign particles/infectious microorganisms that reach the alveoli
What is the respiratory pressure cycle?
Air flow and pressure changes.
- Changes in volume result in changes in pressure
* As the volume of a container increases, the pressure within the container decreases
* Same for lungs
* Respiratory muscles change the volume of the thorax - Air flows from an area of higher pressure to an area of lower pressure
* The greater the pressure difference, the greater the rate of airflow
- Intra pulmonary/alveolar pressure
- Respiratory Muscles: change the volume of the thoracic cavity
- Air flow into and out of lungs
What are the Respiratory Muscles?
- Diaphragm
- Intercostal muscles (External&Internal)
- Scalene muscles
- Sternocleidomastoid muscles
- Pectoral muscles
- Abdominal muscles
Features of the Diaphragm:
- 70 % ventilation
- Dome shaped
- Contracts- Downwards and flattens (increasing thoracic cavity)
- Relaxes- Recoils upwards(reducing thoracic cavity)
- Only respiratory muscle working when lying flat and sleeping
What are the features of the Intercostal Muscles?
Where are they situated?
Which way do the external and internal muscles face?
- Between ribs
- Two planes of muscular and tendinous fibres occupying each intercostal space
-Internal beneath external - The external intercostal muscles
-slope downwards and forward
-Contract: ribs upwards and outward
-Elevates ribs and sternum - The internal intercostal muscles
-Opposite direction
-Contract: lower ribs - Stability
What are the steps in the active process of Inspiration?
- Signals from the respiratory centre in the medulla oblongata (brain stem)
2.Contraction of the diaphragm and intercostal muscles leading to the diaphragm moving downward - Transverse expansion of thoracic cavity & Vertical expansion of thoracic cavity
- Lung volume increases and the intra-alveolar pressure decreases
- Air is sucked in (inhalation)
What is expiration?
What are the steps of muscles move in expiration?
- Quiet breathing
- Relatively passive
- Elastic tissue (lungs thorax)
- Lung recoils
- When…..
- Diaphragm relaxes
- Domes (decreases volume)
- External intercostals relax
- Downwards and inwards (decreases
volume) - Laboured exhalation
- Internal intercostals contract
- Abdominal muscles contract
End of Expiration
- Alveolar/intra-pulmonary pressure = atmospheric pressure
- No air movement
End of Expiration
- Alveolar/intra-pulmonary pressure = atmospheric pressure
- No air movement
Pleural pressure
- Pleural Pressure ( the pressure in the pleural cavity)
- Normally lower than alveolar pressure.
- Suction effect - fluid removal by the lymphatic system
- Negative pressure difference (lower pleural pressure
than alveolar pressure) keeps the alveoli expanded - Pulls the pleura away from the outside of the alveoli
- Pressure on the alveoli is lower
- Expansion is opposed by the tendency of the lungs to
recoil
Pneumothorax : Pleura pierced
- Air introduced
- Pleural pressure is not low enough to overcome lung recoil
- Alveoli collapse
Air flow and pressure changes
End of Expiration
* Alveolar/ intra pulmonary pressure =
atmospheric pressure
* No air movement
- Inspiration
- Increased thoracic volume →
- Increased alveolar volume
- Decreased alveolar pressure
- Atmospheric pressure > alveolar
pressure - Air moves into lungs
End of Inspiration
* Alveolar pressure = atmospheric
pressure
* No air movement
Expiration
* Decreased thoracic volume
* Decreased alveolar volume
* Increased alveolar/intrapulmonary pressure
* Alveolar pressure > atmospheric pressure
* Air moves out of the lungs
Exhalation
Passive process (elastic potential energy)
- A passive event due to elastic recoil of the
lungs - Relaxation of diaphragm and external
intercostal muscles - During forced expiration, ONLY there is
contraction of abdominal, internal
intercostal (accessory muscles)
Respiratory Muscles
- No inherent rhythm
- Generate tension due to rhythmic pattern of neuron-induced action potentials activating them
- Muscles attempt to overcome the resistance to airflow within the airways
- When at rest, the thorax assumes the FRC (Functional Residual capacity) position
Respiratory Function: measurement
- Spirometry is the process of measuring volumes of air that move into and out of the respiratory system
- Measurements of the respiratory volumes can provide information about the health of the lungs
- Peak Flow
- Many more
- Static Lung Volumes
- Volumes/capacities
- Dynamic Lung Volumes
- How quickly air can be inspired/expired
Volumes and Capacities
- Respiratory volumes:
- Measures of the amount of air movement during different portions of ventilation,
- Respiratory capacities
- Sums of two or more respiratory
volumes. - The total volume of air contained in the respiratory system ranges from 4 to 6 L
What is Tidal Volume (TV)?
- The volume of gas expired/inspired in one breathing cycle
- Also known as ‘resting’ or ‘quiet’ breathing
- Around 500ml (info)
What is Inspiratory reserve volume?
- Inspiratory reserve volume is the amount of air that can be inspired forcefully beyond the resting tidal volume
What is Expiratory reserve volume?
- Expiratory reserve volume is the amount of air that can be expired forcefully BEYOND the resting tidal volume.
What is Residual volume?
- Residual volume is the volume of air still remaining in the respiratory passages and lungs after maximum expiration (you cant breathe it out)
- Without a residual volume, the lungs would completely collapse and the pressure required to generate inflation would be high
What is Total lung capacity (TLC)?
- The volume of gas in the lungs and airways at a position of full inspiration –therefore we are measuring how much air the lungs can
actually hold - Lung expansion is limited at a point which defines TLC
- Consists of IRV + TV + ERV + RV
What is Vital Capacity (VC)?
- The total volume of gas that can be expired from the lungs from a position of full inspiration/ the total volume of gas that can be inspired
from a position of residual volume - This is similar to an FVC manoeuver except it is not forced
- Consists of IRV + TV + ERV
What is the Inspiratory capacity?
- The tidal volume plus the inspiratory reserve volume
- The amount of air a person can inspire maximally after a normal expiration
- Consists of IRV + TV
What is Functional Residual Capacity?
- The volume of gas in the lungs and airways at the end of a tidal breath
- This is the point at which the inward pull of the lungs and the outward pull of the chest wall are in equilibrium
- Consists of ERV and RV
What is an obstructive lung disease?
A condition that makes it hard to exhale all the air in the lungs.
Dec (small) ERV, TV and IRV
Inc (big) residual volume
What is a restrictive lung disorder
A condition that makes it hard to inhale all the air in the lungs.
Dec in IRV TV ERV and RV
What are the Limits of Spirometry?
Cannot measure Total lung capacity (TLC), Forced Residual Capacity (FRC) and Residual Volume (RV)
Dynamic Lung Volumes: Rate at which air moved
What is Peak flow?
What is it used for?
Peak expiratory flow (PEF): a measure of how quickly you can blow air out of your lungs.
- Measured in litres/minute (l/min)
- “Normal” will depend on age, height and gender
- Record in a peak flow diary and compare against “best”
- Can be used for diagnosis of asthma or to predict oncoming asthma attack
For diagnosis of asthma:
Measure for 2-4 weeks
More than 20% variability regarded as positive test
What is Forced (Expiratory) Vital Capacity? (FEV)
What measures FEV?
- Rate at which lung volume changes during direct measurement of the vital capacity.
- FEV1 forced expiratory volume amount of air you can force from your lungs in one second
- It is a simple and clinically important pulmonary test.
- The individual inspires maximally and then exhales maximally as rapidly as
possible into a spirometer. - The spirometer records the volume of air expired per second.
- help identify conditions where vital capacity might not be affected but the
expiratory flow rate is reduced - Asthma - contraction of the smooth muscle in the bronchioles increases the resistance
to airflow - Emphysema - changes in the lung tissue result in the destruction of the alveolar walls, the collapse of the bronchioles, and decreased elasticity of the lung tissue.
- increase the resistance to airflow
What is FEV1?
Forced Exhaled Volume in 1 Second
✓Amount of air exhaled in 1 second
✓Affected by airway diameter
✓Predict ‘healthy’ values by age, gender and height
What is FVC?
Forced Vital Capacity
✓The total amount of air that can be exhaled (after a maximal inhalation)
✓FVC + Residual Volume = Lung Capacity
✓Predict ‘healthy’ values by age, gender and height
FEV1 / FVC ratio
✓Does not require tables, FEV1 values adjusted to FVC
✓Ratio <0.7 indicates airway obstruction
Basic gas exchange
- Ventilation –we need to be able to get air to the alveoli for gases to exchange
- Perfusion –the circulatory system needs to ensure blood gets to the
alveolar
Where does gas exchange occur?
- Between air and blood occurs at the respiratory membranes
- Alveoli
- Some in the respiratory bronchioles and alveolar ducts
- Not in conducting zone - the bronchioles, bronchi, and trachea.
- The volume of these = anatomical dead space
- Pathology such as emphysema can increase this
What factors is Gas exchange dependent on?
- Thickness of the membrane
- O2 exchange affected before CO2
- O2 diffuses through the respiratory membrane less easily than does CO2
- Total surface area of the respiratory membrane
- Reducing reduces gas exchange
- Partial pressure of gases across the membrane
- Pressure exerted by a specific gas in a mixture of gases
- PO2, PCO2
- Gases in the air dissolve in the liquid
- Until partial pressure in liquid = to the partial pressure in air
- Gases in liquid and air diffuse from areas of higher partial pressure toward areas of lower partial pressure until equal
What is Fick’s law?
Law of diffusion.
V gas = kA/t x (P1-P2)
Diffusion is proportional to difference between the conc of gas on both sides
Inversely proportional to the thickness of the respiratory membrane
What is the process of gas exchange?
- Blood from tissues has a lower
Po2 and a higher Pco2 compared to
alveolar air
* O2 diffuses from the alveoli into
the pulmonary capillaries
* Po2 in the alveoli > in the pulmonary
capillaries
* CO2 diffuses from pulmonary
capillaries into the alveoli
* Pco2 pulmonary capillaries > alveoli - Venous ends of the capillaries:
* Pressures equal because of diffusion
* The blood carries O2 away by bulk flow
to the tissues where O2 is required - Mixing with deoxygenated blood =
lower PO2 than in capillaries - Oxygen diffuses out of the blood and
into the interstitial fluid then into cells
* Po2 in interstitial fluid < capillary
* Po2 in cells < than interstitial fluid
* Carbon dioxide diffuses from cells into
the interstitial fluid and from the
interstitial fluid into the blood
- Equilibrium
Oxygen is stored in the body in four forms: What are they?
- As a gas in the lungs
- Dissolved in tissue fluids
- As oxyhaemoglobin in blood
- As oxymyoglobin in muscle
Features of Haemoglobin Structure:
- Consists of 4 myoglobin units joined
together- Each has one polypeptide chain and
one haem group - Haem contains central Iron (Fe2+ )atom
- Iron atom binds to one oxygen as blood
travels between lungs and tissues - one Hb molecule can bind 4 O2
molecules
What is the Oxyhaemoglobin
Dissociation Curve?
*Ability of haemoglobin to bind to O2
depends on the Po2
*oxy-Hb dissociation curve
*High Po2, haemoglobin binds to
O2
*Low Po2, hemoglobin releases
O2
*Lungs, Po2 normally high
* haemoglobin holds as much O2 as it
can
*In the tissues, Po2 is lower
* haemoglobin releases O2
The amount of O2 released from
oxyhaemoglobin (reduced affinity) is
increased by what?
*low Po2,
*high Pco2
*low pH
*high temperature
*Physical Exercise
Carbon dioxide diffuses from cells into the blood.
How is it transported?
- 7% is transported as CO2 dissolved in the plasma
- 23% is transported bound to blood proteins, primarily haemoglobin
- 70% as bicarbonate ions (carbonic acid= CO2 dissolved in H2O)
Gas exchange in Tissues:
CO2 diffuses into plasma and RBC
* Forms carbonic acid catalysed by carbonic anhydrase found inside RBC and on the capillary epithelium
* Carbonic anhydrase increases the rate at which carbonic acid generated in tissue capillaries
* promotes the uptake of CO2 by red blood cells.
CO2 + H2O = H2CO3 = H+ + HCO3
Gas Exchange in Lungs
Capillaries of the lungs
* the process is reversed
* CO2 diffuses from RBC to alveoli
* HCO3−dissociates to produce H2CO3
* Carbonic anhydrase catalyses formation
of CO2 and H20 from H2CO3
* The CO2 diffuses into the alveoli and is
expired
pH: Importance of carbon dioxide
- Carbon dioxide has an important effect on the pH of the blood
- As CO2 levels increase, the blood pH decreases (becomes more acidic) because CO2 reacts with H2O to form H2CO3 (carbonic acid)
- The H+ that results from the dissociation of H2CO3 is responsible for
the decrease in pH. - Conversely, as blood levels of CO2 decline, the blood pH increases
(becomes less acidic, or more basic)
Anatomical dead space refers to what? ….
Conducting zone
Control of Respiration
- Normal rate of breathing in adults
- Between 12 and 20 breaths per minute
- rate of breathing determined by the number of times respiratory muscles are
stimulated - Breathing is spontaneously initiated within the central nervous system (CNS)
- Medulla oblongata (brainstem)
- An increased depth of breathing results from
- stronger contractions of the respiratory muscles caused by recruitment of muscle
fibres - increased frequency of stimulation of muscle fibres
Rhythmic Breathing
The integration of stimuli that start and stop inspiration
1. Starting inspiration.
* Neurons in the medullary respiratory center that promote inspiration - continuously active
* stimulation from
* blood gas levels, movements of muscles and joints, voluntary respiratory movements
* When the inputs reach a threshold level
* somatic nervous system neurons stimulate respiratory muscles ( via action potentials)
* inspiration starts
2. Increasing inspiration.
* Once inspiration begins, more and more neurons are activated
* Progressively stronger stimulation of the respiratory muscles, lasts for approximately 2 seconds
3. Stopping inspiration.
* Neurons stimulating muscles of inspiratory muscles also stimulate medullary neurons that stop inspiration
* These also receive input from the pontine respiratory neurons
* Stretch receptors in the lungs
* When the inputs to these neurons exceed a threshold level,
* they cause the neurons stimulating respiratory muscles to be inhibited.
* Relaxation of respiratory muscles leads to in expiration (3 s).
* Next inspiration step 1
The system must perform three key functions:
The system must perform three key functions:
- Maintain, through involuntary controls, a regular rhythmic breathing
pattern - Adjust the tidal volume (VT) and breathing frequency (fb) such that
alveolar ventilation is sufficient to meet the demands for gas exchange at
cellular level - Adjust the breathing pattern to be consistent with other activities using
the same muscles, such as speech
* Some conscious control
Respiratory control system
Consists of:
What Sensors?
What elements of the Central control system?
Sensors- Chemoreceptors, lungs and other receptors (input to CCS)
Central Control System- Pons, medulla, and other parts of the brain (Output to effectors)
Effectors- Respiratory muscles
Respiratory control centres
The major groups of neurons in respiratory centre which control respiration:
Pons
* Pontine respiratory group
* Controls switches between inspiration and expiration
Medulla
* Dorsal respiratory group (DRG)
* Diaphragm (inspiratory)
* Ventral respiratory group (VRG)
* Intercostals
* Abdominals
* Inspiratory and expiratory
Nervous Control of Breathing
- Some voluntary control
- Most autonomic
- Several reflexes, such as sneeze and cough reflexes, can
modify breathing - The Hering- Breuer reflex
- limits the extent of inspiration
- As the muscles of inspiration contract the lungs fill with air
- Sensory stretch receptors located in the lungs are stimulated
- Action potentials sent to the medulla oblongata
- Here they inhibit the respiratory centre neurons and cause
expiration - In infants important role in regulating the basic rhythm of
breathing and over inflation - In adults when the tidal volume is large - during heavy exercise
Chemical control of Breathing
- Level of CO2 (not O2), in the blood is the major driving force
- Even a small increase in the CO2 level (hypercapnia) results in a powerful urge
to breathe - Breathing is controlled so finely that the PaO2 and PaCO2 are kept within
normal limits - To achieve this, the system has three control pathways –
- The PCO2 is the principle pathway, controlling the rate and depth of
breathing on a breath-by-breath basis - Under certain circumstances, such as acclimatization to altitude, the PO2
pathway (the second pathway) can override the PCO2 pathway. - A third pathway is required to allow all other actions such as talking,
swallowing and coughing to break through the normal pattern of breathing
and try to match breathing to the expected voluntary or behavioural activity
Central chemoreceptors
An increase CO2 causes an inc in H+ ions which increases ventilation and vice versa as follows:
- PaCO2 rises causing a rapid increase in H+ ions
- This causes pH to fall (increase acidity)
- This causes the central chemoreceptors to transmit a signal to
increase ventilation - In doing so, PaCO2 and CO2 decrease and when balance is restored, ventilation
will decrease
Where are Chemoreceptors located?
Centrally
* Medulla oblongata
Peripherally
* Carotid bodies
* Aortic bodies
Chemical control
- pH that accompanies an increase in
CO2 levels - Chemoreceptors
- Medulla oblongata
- chemoreceptors H+ concentration
- pH CO2
- If blood CO2 levels decrease, pH increase
→medullary chemoreceptors signal a
decreased breathing rate →retains CO2 in
the blood - More CO2 in the blood causes H+ levels to
increase, →blood pH to decrease to
normal levels - Carotid and Aortic bodies:
- pH, Co2, O2
- Increased breathing
Global Innervation
Parasympathetic NS is dominant in the lungs
Airways
* Innervated by the vagus nerve –Parasympathetic
* Dominant
* Bronchoconstriction
* Innervated by the Sympathetic nerve chain
Respiratory Muscles
* Innervated by the intercostal (motor) nerves
* Phrenic nerve innervates the diaphragm
Autonomic Nervous System Physiology
Parasympathetic nervous system
Neurotransmitter (effector) –Acetylcholine (Ach)
* Receptors –muscarinic / cholinergic receptors
* M1 to M5
* Airways: M1 M2 M3 present. M3 most important
* Muscarinic receptors
* Stimulation causes the contraction of bronchial smooth muscle
* Muscarinic receptors located in many glands help to stimulate secretion
e.g. mucus and saliva
Autonomic Nervous System Physiology
Sympathetic nervous system
Neurotransmitter (effector) –Noradrenaline (NA)
* Receptors –adrenergic receptors
* alpha, beta1 and beta2
* Beta1 receptors –heart
* Stimulation increases rate and force e.g.
adrenaline/epinephrine
* Beta2 receptors –smooth muscle of bronchioles
* Stimulation (Agonist) causes relaxation e.g. salbutamol
What is the difference between static and dynamic lung volumes
Static- not forced
Dynamic- forced and measured over time
What are examples of Respiratory Pathologies?
- Chronic Obstructive Pulmonary Disease (COPD)
- Asthma (obstructive)
- Congenital and genetic lung conditions e.g. Cystic Fibrosis (obstructive)
- Obstructive sleep apnoea
- Restrictive lung disease e.g. occupational lung disease
- Lung cancer (restrictive)
- Respiratory muscle disorders e.g. ALS (Restrictive)
What is lung capacity?
-How much air can be inhaled
-Reduced by RESTRICTIVE airway disease
What is air flow?
-How quickly air can be moved out or into the lung
-Air flow reduced by OBSTRUCTIVE airway disease
What is Obstructive lung disease?
More difficult for air to flow out of the lungs due to increased airway resistance, causing a decreased flow of air in and out of the lungs
This may be due to:
* Partial occlusion of the lumen due to excessive secretions (e.g. chronic bronchitis)
* Contraction of smooth muscle of the bronchi (e.g. asthma)
* Hypertrophy of mucous glands (e.g. chronic bronchitis)
* Inflammation and oedema of airway wall (e.g. bronchitis and asthma)
* Loss of radial traction (e.g. emphysema)
What is Asthma?
- A chronic inflammatory disorder of the airways with reversible airway obstruction and increased airway responsiveness to a variety of stimuli
- Variable airflow limitation that normalises with treatment or spontaneously
What are the symptoms of Asthma?
- Shortness of breath
- Chest tightness or pain
- Wheezing during exhalation
- Coughing or wheezing attacks that are worsened by a respiratory virus
- Chronic cough
- Significantly variable breathlessness
- Night-time wakening with breathlessness and/or wheezing
- Significant diurnal or day-to-day variability of symptoms
What is Laminar flow?
What is Turbulent velocity?
What is Turbulent airflow?
Low-velocity and narrow tubes
High velocity & Irregular walls
The pressure difference required to maintain airflow need to be increase
Respiratory muscles need to work harder to expand and contract the lungs
What are the causes of asthma?
Host factors and environmental exposures
Genetic factors: Cytokine response profiles
Environment: Allergens, Pollutants, Infection, Stress
Age
What are the environmental/modifiable factors for triggering asthma?
Allergens
* House dust mite
* Pets
* Fungal spores
* Pollens
Infections
* E.g. LRTI
Others
* Smoking
* Pollution
* Occupational hazards (e.g. flour, chemicals)
* Stress
* Exercise
* Cold air
Airflow obstruction and increased airway
resistance
- Induced by airway inflammation
- Bronchoconstriction
- AHR – exaggerated bronchoconstricting
response to stimuli - Airway oedema – as disease becomes more persistent and progressive
AHR= Airway Hyper responsiveness
What is bronchoconstriction?
Bronchial smooth muscle contraction that narrows the airways in response to stimuli
Narrowing the airway makes it harder to breath- increased resistance
* Increased mucous decreases airway diameter
* Smooth muscle contraction narrows airway
= Causes asthma attack
What is Mucous plugging and hyperinflation?
Turbulent airflow around blockage causes characteristic wheezing
Asthma Summary
- Asthma exacerbation
- Airways already narrowed
-mucosal inflammation
-smooth muscle hypertrophy - Airways further constricted due to increased smooth muscle tone
- Decrease the diameter of the airways
- Causing resistance to airflow to become very high
- Combined with hyperinflation
- Patient must work harder to overcome the increased resistance
- This can lead to turbulent flow
- Causes characteristic wheeze of an asthma attack
How to go about Choosing inhalers:
- All patients to receive a preventer inhaler in addition to their reliever.
- Choice of device based on patient preference and technique.
- Where possible, use an inhaler with low global warming potential.
- If more than one inhaler given, give the same type
What are the different types of inhaler?
(P)MDI- Pressured metred dose inhaler
e.g. Saprobec, Clenil Modulate
Dry powder inhaler
e.g. Budesonide, Salbutamol, Terbutaline
How to use a spacer:
What is Peak expiratory flow (PEF)?
A measure of how quickly you can blow air out of your lungs.
* Measured in litres/minute (l/min)
* “Normal” will depend on age, height
and gender
* Record in a peak flow diary and
compare against “best”
* Can be used for diagnosis of asthma or
to predict oncoming asthma attack
How to measure a peak flow?
Step-by-step how to use equipment.
- Pull the counter (the red arrow) back as far as it will go to the top near the mouthpiece.
- Stand or sit upright – choose what’s most comfortable for you and always do it that way.
- Take the deepest breath you can.
- Make sure your mouth makes a tight seal around the mouthpiece.
- Blow as hard and as fast as you possibly can into the meter.
- Write down your score (the number next to the pointer).
- Do this three times in a row so you get three scores (all three scores should be roughly the same).
- Use the highest of these scores to fill in your peak flow diary.
How can you use peak flow to diagnose asthma?
Or what about individuals who already have asthma, what is seen as normal?
What is not normal?
- Measure for 2-4 weeks
- More than 20% variability regarded as positive test
- Up to 20% lower than best is considered normal
- 20-50% lower than normal means action needs to be taken
- Medical help
- Action plan
What cant spirometers measure?
Residual volume-the volume of air remaining in the lungs after maximum forceful expiration.
What structure protects the respiratory tract when you swallow?
Epiglottis which is part of the larynx
Protects the airway when swallowing
When might diameter of bronchi/bronchioles change?
Is asthma an obstructive/restrictive disease?
Obstructive
What is a restrictive lung disease?
A decrease in the total volume of air that the lungs arr able to hold
What is a restrictive lung disease?
A decrease in the total volume of air that the lungs arr able to hold
Why does breathing become difficult during an asthma attack?
Bronchioles are constricted and the airway passages become narrow (lined with mucus). You cannot breathe the full amount of air in one breath, so your breathing is short and low volume
What is a restrictive lung disorder
