Flashcards in Respiratory Failure Deck (17):
inhalation occurs against what forces?
elastic and resistive
function of theupper airway
stay open to allow inhalation
what does surfactant do?
improves compliance by reducing surface tension of fluid lining alveoli.
prevents alveoli collapse
why does gas exchange occur?
difference between partial pressures of O2 and CO2 between alveoli and pulmonary capillary across the A-C membrane. normally very efficitent
normal arterial blood gas values
O2 sat = >95%
what is the A-a gradient adn what would cause an elevation in it?
it is the difference in partial pressures of oxygen between the arteriole (A) and the alveoli (a)
elevation of the gradient indicates impaired gas exchange
calculation for A-a gradient?
=(150-1.25xPaCo2) - PaO2
what is respiratory failure?
impairment of gas exchange between air and circulating blood leading to the inability to maintain arterial blood gas concentrations either by impairing exchange in the alveoli or inability to bring air in or out of the lungs
what is type 1 respiratory failure?
impaired gas exchange leading to hypoxaemia paO2<60mmHg
what is type 2 respiratory failure?
impaired ventilation leading to hypercapnia PaCO2>50mmHg
causes of hypoxaemia
1. reduced inspired O2
2. VQ mismatch (pneumonia, PE)
3. impaired diffusion (COPD, fibrosis)
4. shunt (total VQ mismatch, incluides where blood bypasses lungs altogether)
5. reduced ventilation
what could cause hypercapnoea
1. respiratory depression
2. blocked airways
3. respiratory pump failure
4. muscle fatigue
signs of respiratory failure
accessory muscle use
altered state of consicousness/drowsiness
increased resp rate (or decreased in severe)
low O2 saturation
investigations for suspected respiratory failure
arterial blood gases
investigations into cause eg CXR, bloods, CTPA, VQ scan, lung function/spirometry
management principles of respiratory failure
1. maintain O2 delivery (not too high in blue bloaters)
2. reduce work of breathing
3. maintain pH, electrolytes
4. target the cause
5. analgesia (dont cause depression tho)
what is acute respiratory distress syndrome?
mass release of inflammatory mediators increases pulmonary capillary permeability leading to edema and diffusion impairment leading to impaired gas exchange and increased work of breathing