When I’m teaching communication in a crisis to my Perioperative/OR nurses, I often recount the story of what happened during one particular child’s recovery years ago. This case, involving a 2 year old child who developed respiratory depression in the recovery room, demonstrates how good communication in a crisis, including the ability to challenge an authority figure, can improve patient safety and allow collaborative teamwork in a crisis management situation. Continue reading
Alveolar gas exchange depends not only on ventilation of the alveoli but also on circulation of blood through the alveolar capillaries. In other words it depends both on ventilation and perfusion. This makes sense. You need both oxygen in the alveoli, and adequate blood flow past alveoli to pick up oxygen, other wise oxygen cannot be delivered. When the proper balance is lost between ventilated alveoli and good blood flow through the lungs, ventilation perfusion mismatch is said to exist.
The ventilation/perfusion ratio is often abbreviated V/Q. V/Q mismatch is common and often effects our patient’s ventilation and oxygenation. There are 2 types of mismatch: dead space and shunt.
This article will describe how dead space is different from shunt. It will help you understand how you can use these concepts to care for your patient. Continue reading
I often find that my students sometimes confuse oxygenation and ventilation as the same process. In reality they are really very different. Ventilation exchanges air between the lungs and the atmosphere so that oxygen can be absorbed and carbon dioxide can be eliminated. Oxygenation is simply the addition of oxygen to the body. You must understand the difference to understand how hypoventilation causes hypoxia.
If you hyperventilate with room air, you will lower your arterial carbon dioxide content (PaCO2) significantly, but your oxygen levels won’t change much at all. On the other hand, if you breathe a high concentration of oxygen, but don’t increase or decrease your respiratory rate, your arterial oxygen content (PaO2) will greatly increase, but your PaCO2 won’t change.
Ventilation changes PaCO2. Oxygenation changes PaO2.
Why do we need to understand this? Let’s look at some common examples. Along the way we will painlessly use the Alveolar Gas Equation to explain two common scenarios:
- how hypoventilation causes hypoxia,
- why abruptly taking all supplemental oxygen away from a carbon dioxide retainer will hurt them.