Intubation & Ventilation Scenario 1

      
   

 

      
      A 22 year old male found collapsed in the street, pinpoint pupils, respiratory rate of 5 and a PCO2 of 70 mmHg, PO2 60mmHg.

  1. Is it ventilatory failure or oxygenation failure (is the PCO2 > 50mmHg, is the PO2 <50mmHg). Remember that a low O2 is much more significant than a high PCO2, but is frequently easier to treat.
  2. If it is ventilatory failure, where is the injury – in the brain (the medulla), in the spinal cord, in the peripheral nerves, at the neuromuscular junction, in the muscle itself or in the chest cage?
  3. If the problem is oxygenation failure, where is the injury: is it in the blood supply, at the alveolar-capillary interface or in the upper, middle or lower airways?
        
     

Main Problem Associated Problem Associated Problem

 

Solution

This man has ventilatory failure, as you can see from his high CO2. He is also somewhat hypoxemic, which is not surprising, as CO2 will displace O2 from the alveolus when it builds up (we know this from the alveolar gas equation: PAO2 = PiO2 – PaCO2/R). The combination of meiosis and bradypnea immediately suggests narcosis, which can be reversed, at least temporarily, with naloxone. The mechanism of his respiratory failure is thus loss of respiratory drive due to opioids reducing the sensitivity of the respiratory center to carbon dioxide.