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15 Cards in this Set
- Front
- Back
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What is normal PaO2 for breathing room air? How much of blood oxygen content is dissolved oxygen? |
80 - 120 mmHg PaO2. Normally, 98.5% oxygen carried on haemoglobin. |
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What does a pulse-oximeter measure? |
Peripheral haemoglobin saturation (SpO2). Correlates with SaO2 well (usually). Usually correlates with total blood oxygen content, except in an anaemic patient. Also measures Hb sat with CO, not just O2. |
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What is a normal pulse-ox reading? |
On room air, >95% acceptable. On 100% oxygen, >98% acceptable. Under 90% is severe hypoxia (= PaO2 of 60mmHg). |
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How does PO2 correlate with SaO2? |
Haemoglobin binds more easily to additional oxygen when some binding sites already filled, so PO2 and SaO2 don't relate in a linear way. Above PaO2 of 60mmHg, binding sites are mostly filled. Below 60mmHg, haemoglobin starts to desaturate rapidly. P50 is about 26mmHg. |
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What causes a "right shift" in the oxygen-haemoglobin dissociation curve? What does this signify? |
Right shift caused by CO2, acidosis, 2,3-DPG, exercise, temperature. Haemoglobin has a lower oxygen affinity/releases it more readily in these environments. |
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Is the fetal oxygen-haemoglobin dissociation curve shifted to the left or the right compared to the adult one? |
Left - their haemoglobin has a really high oxygen affinity. |
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What does oxygen delivery depend on? What is the usual oxygen extraction (VO2) by tissues? |
Oxygen delivery = CO (HR x SV) x oxygen content (Haemoglobin + dissolved oxygen) Oxygen uptake usually 25 - 50% |
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What things commonly cause an inspiratory dyspnoea? |
1. Extra-thoracic obstruction (esp if stertor). 2. Pleural effusion (may have decreased lung sounds ventrally) or other restrictive diseases. |
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What steps for a cat in respiratory difficulty? |
1. Oxygen/rads/thoracocentesis to start. 2. Top 3 ddx are heart or pleural space disease or asthma. 3. Can give ONE dose of dex and ONE of frusemide relatively safely, if dx not yet clear. |
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What determines whether cyanosis is observed? |
1. Severe desaturation 2. At least 5g/L of haemoglobin present (or patient will just look white) |
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Outline a practical clinical plan for a stable but coughing cat, and a frugal owner? |
1. Rad to rule out neoplasia, foreign body, CHF (rare to cause a cough in cats), etc. 2. Treat for lungworm empirically 3. Doxycycline course empirically 4. Treatment trial for asthma 5. Push for BAL if no answers so far |
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How can an owner determine if a cat is coughing/gagging, or vomiting? |
Low head position/snaky neck for cough. Bringing up food/bile/hair for vomit (however cats can cough until they vomit). Gagging/gulping vs harsh noises. Tell them to take a damn video. |
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How much pleural fluid to cause dyspnea in cats? What is common respiratory pattern for severe chronic pleural effusion? |
> 100 ml Inspiratory with no stertor/stridor |
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Respiratory pattern commonly seen with urt obstruction? |
Dynamic (eg larpar), inspiratory w stertor or stridor Fixed, mixed pattern |
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What two parameters needed to see cyanosis? |
Haemoglobin conc over 50 g/L (I.e PCV > very approx 15 in dogs or 20 in cats) and Haemoglobin sat < 70 (pulse ox < 40) |
