L20: Respiratory Failure Flashcards
What is type 1 respiratory failure
Failure of oxygenation
Pa02 less than 8kpa
Paco2 normal or low
Ph is normal
What is type 2 respiratory failure
Failure of ventialtion
Pa02 less than 8kpa
Paco2 higher than 6.7kpa
Ph is less than 7.35- exception is chronic type 2 respiratory failure where kidneys can compensate
What are the causes of type 1 respiratory failure
Alveolar hyperventilation
Low oxygen levels e.g high altitude
Lung damage and diffusion deficts e.g pulmonary fibrosis, pneumonia and ARDS
Shunts
V/q mismatch e.g pulmonary embolus (reduced perfusion but normal ventilation)
What are the causes of type 2 respiratory failure
Failure of alveolar ventilation :
Copd
Alveolar hypoventialtion
If there is a respiratory cause what compensates
Kidney (metabolic)
If there is a metabolic cause what compensates
Lungs (respiratory compensation)
What does a reduction in alveolar ventilation cause to hydrogen ion
Increass due to decreased co2 reacting with water
What does a increase in alveolar hyperventilation cause to hydrogen ion
Decrease in hydrogen ions due to increased carbon dioxide
How quick are kidneys at compensating
Not quick, compensation will occur when its chronic
What are the steps to interpreting abg
- Is the patient hypoxic
- What is the ph- acidotic or alkalotic
- Check pac02- is it a respiratory cause
- Check the bicarbonate - is it a metabolic cuase
What are the causes of alveolar hypoventilation
Central nerbvous system disorders: depressant intoxcants
Disorders of respiratory muscles: myasthenia gravis, gullian barre syndrome
Defects of chest wall or funtinonal disorders
Airway obstruction: tongue, foreign body aspriation, copd
What should be the expected pao2 is someone is one oxygen
Less than 10 e.g 50% should be 40kpa
What is the base excess of less than -2mmol/ suggest
Metabolic compensation for respiratory alkalosis
What does a base excess of more than 2mmol/l suggest
Metabolic compensation for respiratory acidosis
What is base excess a measure of
Excess acid or base
What does a negative base excess indicate
More acid in the blood
What causes paraesthesia in people with anxiety (respiratory alkalosis)
Alkalosis causes Hypocalcaemia. This occurs when alkalosis causes hydrogen ions from the albumin to dissociate and takes up free calcium in the serum that leads to Hypocalcaemia.
What is a patient presenting with diarrhoea likely to present with on an ABG
Metabolic acidosis
How does diarrhoea cause metabolic acidosis
Bicarbonate is lost from the git in the diarrhoea
What is sepsis likely to present as on a ABG
Metabolic acidosis
How does sepsis cause metabolic acidosis on a ABG
Due to increase in lactic acid
What is dka likely to present as on a ABG
Metabolic acidosis
How does dka cause metabolic acidosis
Production of ketone bodies can cause acidosis
How can we further investigate dka (other test?)
Capillary glucose test - high
Urinalysis- ketones and glucose present
What is vomiting likely to present as on a ABG
Metabolic alkalosis
How does vomiting cause metabolic alkalosis
- HCl is lost from the stomach when the person vomits
- Blood volume is also depleted which activates the RAAS that causes an increased bicarbonate absorption from the kidney
