Respiratory failure Flashcards
what is the consequences of oxidising the atmosphere
- Some anaerobes sought anaerobic microenvironments
- Organisms developed defences against oxygen and free radicals
- Animal kingdom developed aerobic metabolism - required mitochondria
how do you work out inspired gas
- Concentration of oxygen in air = 20.94%
- Barometric pressure = 101.3 kPa
- 0.2094 x 101.3 = 21.2
- PO2 of dry air at sea level is 21.2 kPa
why does the partial pressure of oxygen drop when you go up a mountain
- Get PaO2 if you multiply the concentration of oxygen in air x barometric pressure
- When you go up high the barometric pressure drops this is why the partial pressure of oxygen decreases as the oxygen parital pressure remains the same
what causes the PO2 to decrease in tracheal gas
• = PO2 decreases after humidification
how do you work out tracheal gas
- Fractional concentration of oxygen in the dry gas phase x (barometric pressure - SVP)
- FiO2 x (PB - SVP)
- Quantity in parentheses = dry barometric pressure = 95 kPa
- = 0.2094 x (101.3 – 6.3)
- = 19.9 kPa
what factors affect alveolar PO2
- Ventilation
- Oxygen consumption/carbon dioxide production
how do you work out alveolar PO2
- PAO2 = dry barometric pressure x (FiO2-VO2 / VA)
- PAO2 = PiO2 – (PaCO2 / R)
- VO2 – oxygen consumption 3.5ml per kilo per minute
- Pa CO2 – arterial partial pressure
- R – respiratory equation
How do you work out arterial PO2
- The alveolar to arterial PO2 difference is determined by shunting
- The normal A-a O2 difference is not normally greater than 2 kPa
- Normal PaO2 = 13.6 – (0.044 x age in yrs) kPa
- e.g. most of us will have 12.7 kPa 20 yrs, 10.7 kPa 66 yrs
what is a pulmonary shunt
A pulmonary shunt is a pathological condition which results when the alveoli of the lungs are perfused with blood as normal, but ventilation (the supply of air) fails to supply the perfused region
what is the normal range of potassium in the body
the normal range of potassium in the body is 3.5-5.3
how does potassium link to the partial pressure of oxygen and venous blood
the normal range of potassium in the body is 3.5-5.3
10kpa is 94% then you start to desaturate very quickly after than
P50 – this is the parital pressure of oxygen at which haemoglobin is 50% saturated, this is 3.5 KPa
If take venous blood Sv02 this is 5.3
- this is the same reference of potassium
what does oxygen delivery depend on
- oxygen saturation
- haemoglobin concentration
- cardiac output
what is the equation of oxygen delivery
- oxygen delivery = haemoglobin x oxygen saturated of Hb x 1.34x10 x cardiac output
what are the signs of respiratory compensation
- Tachypnoea
- Use of accessory muscles
- Nasal flaring
- Intercostal or suprasternal recession
what are the signs of increased sympathetic tone
- Tachycardia
- Hypertension
- Sweating
what are the signs of respiratory failure
End-organ hypoxia • Altered mental status • Bradycardia and hypotension (late) Haemoglobin desaturation • Cyanosis – don’t go blue until 8Kpa on the partial pressure of oxygen CO2 Retention • Flap • Bounding pulse
what is the definition of type I respiratory failure
– Hypoxaemia only – type I respiratory failure is only type I
– PaO2 < 8 kPa
what is the definition of type II respiratory failure
– Hypoxaemia and hypercapnia
– PaO2 < 8 kPa
– PaCO2 >6.5 kPa
what are the examples of type I respiratory failure
- Pneumonia
- Pulmonary oedema
- Asthma / COPD
- Pulmonary embolism
- Pneumothorax
- Obesity
- Atelectasis
- Collapse
- Pulmonary contusion
what are examples of respiratory failure type II
• Type I with fatigue
• Hypoventilation
Commesnt cause of type II respiratory failure is type I with fatigue
what are types of type II respiratory failure
Causes of hypoventilation (type II respiratory failure) • Brainstem • Metabolic encephalopathy • Depressant drugs • Spinal cord • Nerve root injury • Nerve trauma • Neuropathy • Neuromuscular junction • Respiratory muscles • Airway obstruction • Decreased lung or chest wall compliance
what is treatment of respiratory failure
- oxygen
what is a Hudson mask
- Breath to breath, respiratory rate, tidal volume
- Person to person
- Size of mask, type of mask, vents in mask, fit of mask
the sicker the patient when using the Hudson mask..
the less oxygen they are getting
how can you give oxygen
Oxygen masks (Hudson mask), nasal cannulae
• Patient with normal vital signs (post-op)
Face mask with reservoir bag
• Higher O2 concentration needed (asthma attack, pneumonia, sepsis)
Venturi mask
• Controlled treatment in long-term respiratory failure (COPD)
• Also called fixed performance systems
what are the venturi colour and the flow rate and the oxygen delivered
- blue
- white
- yellow
- red
- green
- blue - 2 l/min 24 oxygen delivered
- white - 4l/min 28 oxygen delivered
- yellow 6 l/min 35 oxygen delivered
- red 8 l/min 40 oxygen delivered
- green - 12 l/min 60 oxygen delivered
what is the critical saturation of oxygen threshold
• A pulse oximetry saturation (SpO2) ~94% is a critical threshold. Below this level a small fall in PaO2 produces a sharp fall in SpO2
what does pulse oximetry tell us about
• Pulse oximetry only tells us about oxygenation NOT ventilation
what are the sources of error of pulse oximetry
- Poor peripheral perfusion
- Dark skin (oximeter over-reads slightly)
- False nails or nail varnish
- Lipaemia / hyperlipidaemia / propofol infusion
- Bright ambient light
- Poorly adherent probe
- Excessive motion
- Carboxyhaemoglobin (SpO2 > SaO2)
if the SpO2 is greater than 94% then the PaO2 is…
• If the SpO2 is >94% the the PaO2 should be >10kPa
what do high concentration of oxygen do
• High concentrations of oxygen produce free radicals that can damage the body
why does carbon dioxide decrease in type 1 respiratory failure
In type I respiratory failure the carbon dioxide goes down as your trying to get rid of the carbon dioxide
what is the COPD retainer type of patient
• Only 10% of all COPD Patients
If uncertain if CO2 retainer and acutely unwell
• Start high flow oxygen.
• Monitor for drowsiness / signs of CO2 retention.
• Check ABGs after 30 minutes
• They relie on the hypoxia to drive there breathing
• So if you give them oxygen and there no longer hypoxic then they stop breathing
• Therefore they are given the venturi masks
how do you treat at COPD patient normally
- Controlled mask
- Titrate - use lowest O2 possible
- Aim for sats 90% - 92% (may need 85%+)
- Measure ABGs ASAP
- Repeat ABGs after 30 mins of O2 change
- Requiring 60% oxygen to maintain sats
- Severe tachypnoea (e.g. > 30 bpm)
- Confusion / LOC
- pH < 7.20
- pCO2 > 8kPa
when is ventilation used
- Not for hypoxia
- Used for hypercapnea
- i.e. give oxygen in hypoxia and ventilate in hypercapnea (= hypoventilation)
