pulse oximeter

The small electronic device a nurse attaches to the end of your index finger with a plastic clip calculates how much oxygen is carried in your blood. It's based on measuring the difference between levels of the red pigment hemoglobin which carries oxygen in your blood. It turns out that oxygenated hemoglobin ("oxyhemoglobin") and nonoxygenated hemoglobin ("deoxyhemoglobin") in your blood are different colors. That thing on your finger has two light-emitting diodes - one that sends out invisible infrared light and one that sends out red light.
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The exact colors are chosen to coincide with the maximum differences in colors of light absorbed by each form of hemoglobin. The difference between the two gives a measure of what fraction of the hemoglobin in your blood is oxygenated and thus how much oxygen is being carried around inside you.
Things are not quite so simple, however, as the light must pass through your skin, there's bone in the way, etc. so there's one more trick that's used. In time with your pulse, your finger gets a little bigger and smaller depending on how engorged it is with blood, but the skin and bone remain the same. By comparing the amount of each color of light that gets through with your finger most and least full of blood it's possible to see the effects of the blood itself - and that's finally what gets you a clean oxygen reading without the need to break your skin.
Doctors find this information useful to figure out if your heart/ lungs/ blood are all working together to get oxygen delivered to all the various parts of your body. The test isn't perfect - for example, you could have poor overall blood flow and still a high level of oxygenation.
The test can also be faked out by other things that can influence blood color. For example, exposure to carbon monoxide can give an incorrect reading, but more sophisticated pulse oximeters can use other colors of light to sort out how much hemoglobin has got carbon monoxide stuck to it instead of oxygen.

Defibrillation

Defibrillation is the definitive treatment for the life-threatening cardiac arrhythmias, ventricular fibrillation and ventricular tachycardia. Defibrillation consists of delivering a therapeutic dose of electrical energy to the affected heart with a device called a defibrillator. This depolarizes a critical mass of the heart muscle, terminates the arrhythmia, and allows normal sinus rhythm to be reestablished by the body's natural pacemaker, in the sinoatrial node of the heart.
Defibrillators can be external, transvenous, or implanted, depending on the type of device used. Some external units, known as automated external defibrillators (AEDs), automate the diagnosis of treatable rhythms, meaning that lay responders or bystanders are able to use them successfully with little, or in some cases no, training.

The oxygenator

The oxygenator is main element of the heart-lung machine, which takes over the work of the lungs (adding oxygen to and removing carbon dioxide from the blood). Inside the oxygenator, blood is gently channelled along capillary membranes. The inner lumen of the fibres is streamed with oxygen or oxygen enriched air. Oxygen diffuses through the microporous membrane into the blood, while carbon dioxide diffuses out of the blood into the gas stream and is thereby removed.
Most oxygenators provide a heat exchanger in order to maintain the correct temperature of the patient’s blood. The oxygenated blood is channelled back to the patient.