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23 Cards in this Set
- Front
- Back
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How do you convert from mmHg to kPa and vice versa? |
1 kPa = 7.5mmHg |
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Where is the most common place to take an ABG? |
Radial artery |
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Give the normal ranges of the variables you would measure in an ABG |
- pH 7.35 - 7.45 - PaO2 11.0 - 13.0 mmHg - PaCO2 4.5 - 6.0 mmHg - SaO2 95 - 98 % - Bicarbonate 22 - 26 mM |
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What is the P50 of an oxyhaemoglobin dissociation curve? |
The partial pressure of oxygen that corresponds to a 50% saturation, is 27mmHg |
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What is PvO2 and SvO2? |
The partial pressure and saturation of oxygen in venous blood, typically 40mmHg and 75% |
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Describe the features of an ABG of someone who was suffering acute hypoventilation |
- Low pH - high PaCO2 - low PaO2 - low SaO2 - normal bicarbonate |
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Give 3 types of cause of acute hypoventilation |
Drugs Neurological Respiratory |
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What drugs can cause acute hypoventilation? |
Opiates, eg heroin Benzodiazepines Muscle relaxants |
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What Neurological pathologies can cause acute hypoventilation? |
Severe head injury Massive stroke |
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What respiratory pathologies can cause acute hypoventilation? |
Infective exacerbation of COPD Severe pneumonia |
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Draw a graph relating ventilation rate to PaO2 and PaCO2 |
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What is type 1 respiratory failure also known as? What is characteristic of this type of failure? |
Gas exchange failure, marked by an elevated AaDO2 |
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What is type 2 respiratory failure also known as? |
Hypoventilation |
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What is the alveolar gas equation? |
PAO2 = PIO2 - (PACO2/R) |
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Why can PACO2 and PaCO2 be taken as equivalent? |
Because the CO2 dissociation curve is linear, alveolar CO2 and arterial CO2 are almost always the same |
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What is R in the Alveolar gas equation? |
Respiratory quotient, usually 0.8 |
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Give an example ABG for someone suffering chronic hypoventilation |
- Normal pH - high PaCO2 - low PaO2 - low SaO2 - high bicarbonate |
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Why is pH normal during chronic hypoventilation? |
Because the Bicarbonate level is raised to combat the acidosis |
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What is NIV? |
Non-invasive ventilation, it aids breathing during sleep by slightly increasing inflation pressures on inspiration |
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What might cause chronic hypoventilation? |
Weakness of breathing muscles Obesity and COPD |
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Give an example ABG of someone suffering VQ mismatch |
- high pH - low CO2 - normal O2 - normal SaO2 - low bicarb |
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What are the main causes of VQ mismatch? |
Lung fibrosis Heart failure Pneumonia Inhaled foreign body Large pulmonary embolus |
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How can you tell from the ABG that a patient will have a high AaDO2? |
If they have a low PaCO2 without a correspondingly high PaO2, |
