Topic Progress:

The second problem is the PaCO2. The nurse just draw an ABG and the results show the following:

pH 7.32       PaCO2 62mmHg       HCO3  29mmol/L

[az_toggle_section] [toggle title=”You conclude that he has acute respiratory acidosis. What can you do to correct it?” id=”tgl-1″] Carbon dioxide removal is dependent on alveolar ventilation

Alveolar ventilation = respiratory rate x (tidal volume – dead space)

So you need to increase the alveolar ventilation.

Walk through the break-down tree to figure out how!





[az_accordion_section] [accordion title=”Dead Space” id=”acc-1″] 1. Dead space is the volume of gas in each breath that does not take part in gas exchange

2. Physiologic or total dead space = anatomical dead space + alveolar dead space

§ Anatomical dead space is the gas within the trachea, bronchus, bronchioles and terminal bronchioles

§ In normal adults it is approximately 150mL

§ Alveolar dead space is the amount of gas in alveoli that are not being perfused

§ Occurs in PE, pulmonary haemorrhage and hypotension

3. Circuit dead space contributes to anatomical dead space in ventilated patients

§ Includes gas in ETT, catheter mounts, Y connectors, HMEs and closed suction systems

§ This can become significant in paediatric patients or patients with low tidal volumes [/accordion] [/az_accordion_section]


[/toggle] [toggle title=”Which one(s) of these options will you chose for your patient?” id=”tgl-2″] Increasing RR seems easy and a logical physiologic response since your patient was breathing faster when he started breathing on his own earlier. However you remember to be prudent since increasing RR will reduce time for expiration and might put your patient in whom you just diagnosed a component of bronchoreactviity at risk of air trapping.

Increasing TV (or Pinsp if you were in PC-AC) once again not that interesting. You know that high volumes and high pressures can cause additional damage to an already injured lung and your patient is already at 500mL of TV which corresponds to almost 7cc/kg of ideal body weight. You decide to try avoiding an increase in TV.

What about dead space? Impossible for you to alter anatomical or alveolar dead space other than avoiding hypotension. However, when needed, you might consider shortening the suction systems and circuitry. We sometimes even take out the HME and shorten the ETT…

In summary, you chose to start by simply increasing RR to 18/min (instead of 12/min). This is usually enough to correct the acidosis. You order a gas to be drawn in 30 min. to evaluate if your ventilator setting adjustment was efficient. [/toggle] [/az_toggle_section]



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