Week 1 Flashcards
How do central resp centres change breathing?
Central chemoreceptors (respond to H+ in CSF)
How do peripheral resp centres change breathing?
peripheral chemoreceptors (tension of O2 and CO2 and H+ in blood)
Examples of peripheral respiratory chemoreceptors
Stretch receptors
- Hering breur reflex to prevent hyperinflation
J receptors
- Stim by pulm capillary coingestion and pulm oedema and emboli
Joint receptors
Barorecptors
- Incr vent rate in resp to decor blood pressure (physiological shock response)
How does hypoxic drive of respiration occur?
By peripheral chemoreceptors, not rel in normal respiration, e.g. at high altitude, CO2 retainers
How do ext intercostals work?
lifts ribs and moves out sternum (lifts bucket handle up)
Muscles of active expiration
Internal intercostals, abdo muscles
What factors can affect the ventilatory pump of respiration?
Affected by NM weakness, disorders of chets wall, loss of transmural pressure, incr airway pressure
Kyphoscoliosis, asthma, pneumothorax
Describe intraalveolar pressures
Within alveoli, 760mmHg, equilibrated with atmospheric
Decr in inspiration, incr in expiration (above atmospheric pressure)
Describe intrapleural pressures
Plural sac, 756 mmHg, les than atmospheric
Decr in inspiration, incr in expiration
How would lung pressures change if there was hole in chest wall?
Hole in chest wall, spontaneous pneumothorax cause incr in intrapleural pressure and result in collapsed lung
What is dynamic airway compression?
Pressure is applied to aveoli to push air out rather than airway as it would be compressed
- only becomes a problem in obstructions e.g. asthma or a physical obstruction
- decr in airway pressure downstream and incr in pleural pressure during active resp, more likely to collapse
Describe O2 partial pressure
From alveoli to blood
60mmHg
Describe CO2 partial pressure
Frm blood to alveoli
6mmHg (diffusion coeff is 20x that of O2, means that equal amounts of each are transferred across membrane)
WHat is lung compliance?
Measure of effort that has to go into stretching or distending the lungs
Less compliant lungs mean more work is required to produce a degree of inflation
- decr compliance e.g pulmonary fibrosis, oedema, pneumonia, lung collapse, absence of surfactant
When is work of breathing increased?
Decr pulm compliance
Restricted chets expansion
Incr airway resistance
Decr elastic recoil
Need for incr ventilation
Which 4 factors affect rate of gas transfer at alevoli
Partial pressure gradients of O2 and CO2 (e.g. PE causing decr perfusion)
Surface area of alveolar membrane (e.g. emphysema and lung collapse)
Thickness of barrier separating air and blood across alveolar membrane (e.g. PF, oedema, pneumonia)
Diffusion coefficient
Gas abnormalities affect resp centre in brain
How do intrinsic mechs affect cardiac ouput?
changes in diastolic length of myocardial fibres
Physio changes in HF
Shifts frank starling curve to right, decr stroke vol and preload
How does HF cause SOB?
Stims J receptors, impaired gas exchange, decr compliance
- orthopnoea, PND
How does anaemia cause SOB?
Anaemia impairs the O2 carrying capacity of blood
Tissue hypoxia
Inability to sustain aerobic respiration esp with exertion
Causes incr in h+ due to anaerobic resp
Clin pres of type 2 resp failure
Confusion, reduced consc, asterixis, bounding pulse
- signs of incr CO2 + causative condition
Diff diagnoses of type 2 resp failure
Incr resistance e.g. COPD asthma
Reduced breathing effort e.g. opiates, brainstem
decr in lung vol e.g. chronic bronchitis
NM problems e.g. GBS, MND
Deformity e.g. ank spond, flail chest
How does panic attack cause SOB and tingling extremities?
Resp alkalosis
Incr central and autonomic arousal due to hyperventilation and CO2 loss
Tingling caused by calcium having incr binding to albumin, relative hypocalcaemia, icnr excitability of nerve and muscle fibres
No drop in PO2
What effect does low PO2 have on pulm vessels?
Pulm vasoconstriction
So blood moves more slowly so there is more time for gas exchange t occur in tiny little capillaries
