airway passages and ventilation Flashcards
what are the sections of the airway
- trachea
- bronchi
- bronchioles
- alveolar ducts
- alveolar sacs
what is the role of the condicting airway
- movement of air by bulk flow
- warming
- humidification
- immune defence
- filtration
- sound production
- assist olfaction
what are the main factors affecting airflow
- ability to establish/ maintain a sufficient pressure gradient
- resistance to airflow
what is darcy’s law
flow is proportional to the pressure over the radius
how does air move into the lungs
- contraction of diaphragm and intercostals
- increase intrathoracic volume
- transient increase in pleural cavity volume decreases Pip
- increase Ptp, overcomes lung elastic recoil force
- increase lung volume, decrease Pa
what happens to lung function is diaphragmatic dysfunction
- contraction can’t happen
- pressure gradient for inspiration has stopped
- nerves wont send a message
- pradoxial breathing
what are the causes of pneumothorax
- open injury
- damage tissue allowing airflow into pleura
- spontaneous
what effect does pneumothorax have on breathing
- intrapleural pressure increases to atmospheric pressure
- transpulmonary pressure decreases
- can’t overcome elastic recoil
- lung collapses
what is flail chest
- loss of anatomical integrity of the rib cage
- affects ability to change thorax volume
what is compliance of respiratory system
property of a material undergoing elastic deformation when subject to an applied force
what is the function of compliance in the respiratory system
- compliance of the alveoli and lung tissue
- compliance of thoracic wall
- needed for pressure maintenance
what is infant respiratory distress syndrome
- unable to produce surfactant so reduced surface tension and collapse
- poor lung compliance
what lung factors can alter compliance
- interstitial lung disease
- pulmonary hypertension
- aspiration
- pleural disease
what chest wall factors can alter compliance
- extensive scarring
- sever scoliosis
- ossification of coastal cartilage
- obesity
- position
- neuromuscular changes to intercostal muscles
what affects does increased airway resistance have
- reduced rate of inflation
- decreased tidal volume
- increased PaCO2 and decreased PaO2
what affect does patency have on airways
- needed for sufficient airflow
- lack of patency increases resistance to airflow
what are changes in children’s airways in chocking management
- narrower airways
- larger tongue and adenoids
- larger occiput
- high metabolic rate and small FRC = fast hypoxia
how do abdominal thrust work
- rapid decrease in volume of the thoracic cavity and lungs
- sharp increase in pressure in the lungs
- increase speed of airflow, turbulent airflow
- increase partial pressure helps dislodge
what is laryngospasm
sustain colures of the larynx by contraction of the intrinsic laryngeal muscles resulting in complete or partial obstruction
what mediates larngospasm
peri-glottic stimulus by mechanoreceptors
how does sleeping affect airway patency
- intraluminal pressure in upper airway decreases
- risk of collapse and obstructive sleep apnea
how does autonomic signalling affect resistance
- ach binds to M3 ach receptors on bronchial smooth muscle so bronchoconstriction
- slow and sustained bronchorelaxation
- afferent fibres - constrict
how does inflammation affect airway patency
obstruction from hyperactivity and hypersensitivity reduces expiratory flow
what are additional factors that increase airflow resistance
- increased mucus production
- inflammation and oedema in airways
- head and neck masses
- neck trauma
- obesity
how is airway resistance inversely correlated to lung volume
- reduction in lung volume causes a reduction in the radius of airways increasing resistance
- increase lung volume increases airway radius which reduces resistance
what is the result of alveolar walls being destroyed
- prone to collapse and small diameter and total resistance is higher
how to calculate transmural pressure
PTM = airway pressure - intracranial pressure
what is the spirometry results in restrictive disorders
- FVC reduced
- FEV reduced
- FEV/FVC ratio is within normal range
what are the effects of a supine position for ventilation
- reduced functional residual capacity
- diaphragm elongated so more ability to contract
- increased resistance to airflow
what does the ventral respiratory group do
- activation of accessory inspiration and expiratory motor neurones
- upper airway dilator function
what does dorsal respiratory group
- activation of inspiratory motor neurones
- close to nucleus tractus solitarius
- regulates timing of respiratory cycle
what is the pons function in respiration
- influences the medulla to fine tune respiratory cycle
what are the excitatory neurones of the central pattern generator
glutamate
what are the inhibitory neurones of the central pattern generator
glycine and GABA
what is the purpose of ventilatory support
alveolar ventilation is too low to maintain adequate PAO2 and PACO2
what does negative pressure do in ventilation
helps the body to increase the alveoli
what does positive pressure do in ventilation
increase the amount of air that enters
examples of non-invasive positive pressure ventilation
- BVM
- CPAP
- other ventilators
how does CPAP work
- air supplied at continuous pressure
- positive end expiratory flow
- prevents airway collapse
how does mechanical ventilation increase dead space
increased lung volume > increases radial traction on airways > enhances anatomical deadspace
what are the spirometry results in obstructive disorders
- FVC in expected range
- FEV is reduced
- FEV/FVC is reduced
