7: Resp Failure and Support Flashcards
What is normal tidal volume?
10-20ml/kg
What should mmHg PaO2 be?
80-100
What should mmHg PaCO2?
35-45
What happens to the O2 dissociation curve in sick animals?
Moves right so small O2 changes cause large saturation change
What is type 1 resp failure?
Hypoxic - either from decreased oxygen percentage like altitude or anaesthetic machine failure, OR from pulmonary disease like a shunt, V:Q mismatch or perfusion impairment
What is type 2 resp failure?
Hypoventilation/hypercapnia - from metabolic rate increase or failure to remove CO2 like low resp rate, low tidal volume or too much dead space
What happens in hypoxic pulmonary vasoconstriction?
Blood redirected to well-ventilated areas of lungs
What reduces the effect of hypoxic pulmonary vasoconstriction?
Inhalational anaesthetic, systemic vasodilator, lung trauma or injury e.g. sepsis
How do intrapulmonary shunts respond to oxygen therapy?
Don’t
What determines saturation in intrapulmonary shunts?
The shunt fraction
How long does cyanosis take to occur?
A long time
What does cyanosis depend on?
The amount of Hb
Which sample is definitive for hypoxaemia?
Arterial blood gas
What clinical signs do you see in low O2?
Orthopnoeic stance and tachypnoea
How do you treat hypoxaemia?
De-stress, increase oxygen until sats at 90%, treat cause
What are clinical signs or type 2 resp failure?
Mouth breathing, abducted elbows, no cyanosis, tachycardia as high CO2 is sympathomimetic, bounding pulses, hypertension
How do you treat type 2 resp failure?
Remove cause, ventilate if cannot relieve failure, or tracheostomy
What is type 3 resp failure?
Subtype of 1 with components of 2 - it is atelectasis from increased abdominal pressure or inadequate analgesia for thoracic surgery
What kind of oxygen sats does type 3 resp failure cause?
Low when breathing room air
What are some examples of type I resp failure?
Pneumonia, pulmonary fibrosis, asthma
What are some examples of type II resp failure?
Obstruction, decreased resp muscle, anaesthesia, NM disease
What is an example of type III resp failure?
Atelectasis
How do you treat type III resp failure?
Preventatively - if prolonged op, obese, high intra-abdominal pressure - must ventilate, keep head up, consider bronchodilator
What is the “recruitment manoever”?
To treat type III resp failure - give a high pressure inspiration to cut off venous circulation for 30-45s so alveoli can re-expand
After how long does 100% oxygen cause toxicity, inflammation and eventual fibrosis?
3-4 hours
Above what % O2 do you need a delivery system?
Over 50%
After how long do you see epithelial changes if you don’t use a humidifer?
2-3 hours (atelectasis and tracheitis)
What are some problems with heat-moisture exchange (HME) devices?
Increase deadspace, increase resistance, can disconnect, only useful if intubated
What’s the problem with using a humidifier?
Potential source of infection
How often should you nebulise?
0.9% NaCl for 30-45 mins 2-4 times a day
What does coupage do?
percussing chest wall loosen secretions and stimulates coughing
What is type 4 resp failure?
Cardiovascular impairment to oxygen delivery like a thrombus or cardiac disease, or reduced carrying capacity like anaemia
