Perfusion and Transport of Respiratory Gases

Perfusion happens when oxygen-rich blood moves from capillaries to body tissues.

• This requires a healthy heart and lungs for enough oxygen.

• Red blood cells are mainly responsible for carrying oxygen.

• Hemoglobin in red blood cells has a strong attraction to oxygen.

• When hemoglobin connects with oxygen, it becomes oxyhemoglobin.

• Hemoglobin also binds with carbon dioxide, creating carboxyhemoglobin during gas exchange in tissues (called internal respiration).

• Problems with blood volume or red blood cell count can affect how well oxygen gets to tissues.

Pulse oximetry is a simple method to check peripheral oxyhemoglobin levels.

• Usually measured from the finger, earlobe, forehead, or infant heels/toes.

• Important for monitoring patients on oxygen therapy to ensure their saturation level stays at 94% or higher.

• Normal readings can be 90% or more.

Capnography is another simple method that checks carbon dioxide levels when breathing out.

• Useful for confirming tube placement in mechanical ventilation or dealing with airway blockage.