Respiratory Flashcards
What are the non-respiratory functions of the system?
- Traps and dissolves blood clots
- Defends against microbes
- Ventilation through airways contributes to heat loss and water loss
- important resorvoir for blood
- Phonation
- Metabolic functions
What is partial pressure?
It is the pressure exerted by a gas
How are the trachea and bronchi protected from collapsing?
They have rings of cartilage
What is dead space?
The volume of gas within the respiratory system where no gas exchange takes place. Anatmoical dead space is 150ml
Dead space occurs when there is no effective airflow and no blood flow
What is tidal volume?
Volume of air breathed in and out in one breath (Normally 500ml)
What is the respiratory frequency?
Number of breaths per min (12 breaths)
What is minute ventilation (VE)?
Tidal volume x respiratory frequency
500 x 12 = 6000 ml / min
What is dead space ventilation?
Volume of dead space x respiratory frequency
150ml x 12 = 1800 ml / min
What is alveolar ventilation (VA)
Minute vent - dead space vent
6000 - 1800 = 4200 ml / min
What is FRC?
The amount of air left in the lung at the end of expiration (approx 2.5 L at rest).
What is transmural pressure?
Pressure difference across a wall
What is pneumothroax?
When the balance is lost (lung pulled in and chest wall pushed out). This is by a hole in the chest wall so air goes into these spaces
What is Boyle’s Law?
The pressure exerted by a constant number of gas molecules in a container is inversely proportional to the volume of the container. Increasing the size of the container decreases pressure and decreasing the size of the container increases pressure.
What are the inspiratory muscles?
External intercostals and sternocleidomastoid and scalenes
What are the expiratory muscles?
External oblique, internal oblique and internal intercostals
What happens during inspiration?
- Thoracic cavity enlarges
- Due to pleural membranes, lungs move out with thorax
- Lungs expand (volume increases)
- Alveolar pressure less than pressure outside
- AIR MOVES IN
What happens during expiration?
- Chest wall moves inward
- Volume of thorax decreases
- Lungs recoil
- Alveolar pressure greater than pressure outside
- AIR MOVES OUT
Define Inspiratory Reserve Volume
The maximal amount of additional air that can be expired from the lungs by determined effort after normal expiration
Define Expiratory Reserve Volume
The additional amount that can be expired from the lungs by determined effort after normal expiration
Define Residual Volume
The volume of air still remaining in the lungs after the most forcible expiration possible
What are the functions of surfactant?
- Lowers surface tension of the water layer at alveolar surface - this increases compliance
- Keeps lung dry
- Aids alveolar stability
What would happen if the lungs had no surfactant?
- Compliance of lung would decrease
- Air will flow from small to large alveoli
What are the 4 factors which rate of airflow is dependent upon?
- Density and viscosity of air
- Driving pressure
- Type of airflow
- Resistance of air flow
What are the types of airflow
- Laminar flow
- Turbulent flow
- Transitional flow
What 3 things is the PO2 of alveolar gases determined by?
- PO2 in the atmospheric air
- Rate of replenishment of O2 by ventilation
- Rate of removal of O2 by pulmonary capillary blood
What 2 things is PCO2 determined by?
- Rate of eliminartion of CO2 by ventilation
- Rate of delivery of CO2 from lungs to tissues
Explain the Bohr Shift.
Respiring more, means that tissues are producing more CO2 , forming more carbonic acid which thus forms more hydrogen ions. This lowers the pH of blood.
Haemoglobin has a decreased affinity for oxygen as oxygen unloads more easily to tissue. Haemoglobin is therefore less saturated
How is carbon dioxide carried in the blood?
- Physical solution (dissolved in the blood)
- Carbamino compounds (combined to proteins)
- As bicarbonate (carbonic acid)
What are the sensing receptors for respiration?
- Mechanoreceptors
- Peripheral chemoreceptors
- Central chemoreceptors
Where are the peripheral chemoreceptors located in the body?
The carotid bodies and the aortic arch
Where are the central chemoreceptors located?
In the ventrolateral medulla
What are the main areas of the CNS involved in breathing?
- PONS
- Medulla
What are the medullary respiratory centres and what neurons do they contain?
- Dorsal respiratory group (DRG) - contains inspiratory neurons
- Ventral respiratory group (VRG) - contains inspiratory and expiratory neurons
- Botzinger complex - drives expiration
What drives inspiration during quiet breathing?
- DRG: self excitable neurons generating action potentials to cause inspiration. These neurons sends information to the spinal cord. Activity comes out of the phrenic nerve and the diaphragm will contract.
What causes expiration?
DRG stops sending action potentials
What happens when the demand for ventilation increases during inspiration?
- Sensory info sent to the NTS
- NTS then sends signals to the DRG which causes the neurons there to become more active
- NTS also sends signals to the VRG causing the neurons there to become active through the thoracic spinal cord
- DRG causes the diaphragm to contract and the VRG causes the other inspiratory muscles to contract
- This allows for more forceful respiration
What happens when the demand for the ventilation increases during expiration?
- Sensory info sent to the NTS
- NTS sends signals to the DRG which causes the DRG to stop firing action potentials which causes the diaphagm to relax
- Bozinger complex inhibits inspiration so we can drive expiration
- Shuts off inspiratory neurons
- VRG expiratory neurons activated and expiratory muscles contract.
What does the pontine group do (PRG)?
Influences the switching between inspiration and expiration
What are the types of respiratory failure?
Type 1 = Hypoxia
Type 2 = Hypoxia and Hypercapnia
What is the treatment of COPD?
Bronchodilaters
- Beta 2 agonists
- Muscarinic antagonists
- Methylxanthines
What are the long action Beta 2 agonists?
Formaterol and salmeterol
What are the short acting Beta 2 agonists?
Salbutamol and Terbutaline
What is the muscarinic antagonist used in COPD?
Ipatropium
What is the methylxanthines used in COPD?
Theophylline
What is the regular preventer therapy in asthma?
Inhaled corticosteroids
What is the add on therapy used with inhaled steroids?
Inhaled long action beta 2 agonists (salmaterol and formoterol).
If patient has poor control of asthma even when on inhaled steroid and add on therapy, what is the best treatment option?
- Continue with LABA and Increase dose of ICS
- Continue LABA and ICS but add on a long acting muscarinic LAMA or a leukotriene receptor antagonist (LTRA)
If patient is not controlled at all with high dose therapy for asthma, what is the best treatment option?
- Use daily steroid tablets in the lowest dose.
What are the signs and symtoms of COPD?
- Respiratory distress: Tachypnoea, breathlessness
- Abnormal posture: leans forward
- Drowsiness, flapping tremor and mental confusion
- being overweight, ankle oedemam cyanosis, hyperinflation of the chest
What are the stages of COPD?
Stage 1: FEV1 80% +
Stage 2: FEV1 50-79%
Stage 3: FEV1 30-49%
Stage 4: FEV1 Below 30%
What is the maintenance therapy of COPD?
FEV1 50%+ = Either a LABA or a LAMA
FEV1 <50% = Either a LABA with ICS or LAMA
Offer LAMA in addition to LABA and ICS to people who remain breathless despite taking LABA and ICS
