respiratory failure

What is type 1 resp failure
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Terms in this set (41)
What is type 1 resp failure
Hypoxic
What is type 2 resp failure
Hypoxic and HYPERCAPNIC

Aka. hypoventilation
5 causes of hypoxaemia
1) Ventilation-perfusion mismatch
2) Impaired Diffusion
3) Alveolar Hypoventilation
4) Low FiO2
5) Anatomical R to L shunt
What is anatomical ventilation perfusion mismatch?
It is normal.
The apex of the lung has better ventilation than the base, but the base has better perfusion.
The body tries to redirect blood to different parts of the lungs, so that low ventilation is matched with lower perfusion
When does inefficient gas exchange occur?
when VA/Q<1 OR >1
What are to causes of ventilation-perfusion mismatch?
1) Shunt
2) Dead Space
What is shunt?
Where there are areas of the lungs with no ventilation, an so the blood passing here is not oxygenated- causes hypoxaemia
What is dead space?
Where there is ventilation but no perfusion
What is PaCO2 inversely proportional to?
VA (alveolar ventilation)
What is minute ventilation?
volume of air breathed in and out in one minute, minus the dead space ventilation (trachea, main bronchi etc where there is volume but no gas exchange)
What 3 problems can lead to hypoventilation and hence hypercapnia?1) Reduced neural respiratory drive 2) Reduction in respiratory muscle capacity 3) Increased Respiratory LoadWhat could cause reduced respiratory drive?NEUROPATHY: polio, MND, spinal cord injuries, Gullain-Barré syndrome etc. Opiates and encephalitis affect the central nervous system Drugs such as Gentomycin (an AB) affect peripheral nervous system (Neuromuscular junctions)Causes of reduced muscle capacityMYOPATHIES / MUSCULAR DYSTROPHIES: e.g Duchenne, Becker's MD etc. Neuropathy: polio, NMD, GBS etc.Causes of increased respiratory loadChest wall disease: kyphscoliosis and post-TB (increased chest wall and lung compliance- reduced elastic recoil) Obesity COPD- adds airways resistance and reduced elastic recoil so increased PEEP and dead-space ventilation.List some symptoms of hypoxia and hypercapnia- Dyspnoea - Cyanosis - Somnolence / drowsiness - ConfusionIn severe hypoxia, how can the level of breathlessness sometimes be mild?If there is no hypercapnia Our desire to breath is mainly led by the concentration of CO2 in our blood, and less by concentration of O2.What does ABCDE stand for?Airways Breathing Circulation Disability ExposureWhat SpO2 do we generally class as hypoxia?<92%What does PaO2 actually measure and why is it not that accurate for measuring hypoxia?PaO2 measures the O2 in the liquid phase of the blood. However, mot of the O2 in the blood is attached to Hb in RBCsHow can we get a better idea of wether someone is hypoxic?ABG- Arterial Blood GasesWhy might high levels of O2 not be helpful in stoke or MI if the patient is not hypoxic themselves?Because stroke and MI occur because of ischaemia, not low concentration of O2 in the blood. Therefore, increasing O2 conc. can actually just lead to vasoconstriction and reduce Oxygen delivery even further.Is Oxygen the same as ventilation?NO Oxygen only corrects hypoxia- it won't correct for any alveolar ventilationIn what circumstance might you give high levels of oxygen even when the patient is not hypoxic?Pneumothorax - to try and increase the amount of O2 in the pleural space to increase resorptionWhat is a benefit of Venturi masks?They allow you to predict the FiO2 being delivered to a patientWhat are 3 situations in which you should use NIV?1) Hypercapnic Resp Failure 2) Decompensated resp. acidosis 3) Failed Standard Therapy: including treating the underlying cause of resp. failure.What are the two most common situations in which we use NIV?COPD Obesity related Resp. failureIn what situation might you not be able to ventilate a patient?If the X-ray shows a lot of white / are very opaque- this suggests their lungs will be stiff. These patients would need very high O2 (can be toxic: can cause retinopathy if consistent) and high partial pressures (can cause lung damage too)In a patient in which ventilation may not be appropriate, what is an alternative way of treating their hyPoxia?ECMOWhat is ECMO?Extracorporeal Membrane OxygenationWhat does extracorporeal mean?Happening outside the bodyWhat is VV circulation?Blood is taken out of a vein in the right side of the circulation and is passed through a membrane oxygenator and CO2 removed in a machine and then returned to a vein in the left side of the circulation.What is the main risk associated with ECMO?ECMO patients must be on anti-coagulants and so the main risks are associated with bleeding- particularly haemorrhagic strokeHow can we assess respiratory muscle strength?SpirometryIn what circumstance might a patient have hypercapnia without hypoxia?In patients with respiratory muscle weakness, such as NMD, with normal lungs. (In COPD, it is very rare to see hypercapnia without the hypoxia)Do you need an ABG more to diagnose type 1 or 2 resp failure?Type 2- to look at CO2 concentrations.What does LTOT stand for?Long term oxygen therapyWhat is OSA?Obstructive Sleep ApnoeaWhat is obesity hypoventilation syndrome?Syndrome characterised by obesity, sleep disordered breathing (OSA in 95% of patients) and daytime hypercapnia (CO2>6KPa)Obesity Hypoventilation syndrome is a diagnosis of exclusion, what does this mean?They can't have any other pathology explaining their hypoventilation. - Presence cannot be established with complete confidence from history, examination or testing.What happens to people with NMD when submerged in water?Their FVC falls and their RR goes upWhat is the SNIP test?Sniff Nasal Inspiratory Pressure: measure the strength generated at the nostril during a sniff manoeuvre- this strongly correlated with diaphragm function