Friday, May 15, 2009

Resuscitation with Negative Pressure

I read an article on the invention of the Iron Lung and it is very interesting to note that this respirator was the leading device for resuscitation in the late 20th century. In an experimentation, Philip Drinker placed an anaesthetized cat in a sealed iron box with a neck collar, allowing the body to be within a fully-pressurized environment. Under these conditions, he was able to record accurate measurements of respiration as it was directly relative to his control of the air pressure within the sealed box. Inhalation increased the cat’s volume within the box and made the pressure rise, while exhalation produced the opposite effect. Porta-Lung Inc has conducted similar research studies on the Porta-lung at John Hopkins and other places but instead of a cat, they used a rabbit. With a ventilator like the NEV-100, more accurate measurements of respiration can be recorded with the Porta-Lung because the settings on the NEV are very precise.
The scientist wanted to test a hypothesis: if the cat could not breathe independently, then he would experiment with air pressure by increasing or decreasing the pressure in the chamber to induce respiration. Drinker injected the cat with the South American arrow-poison curare to produce an effect of extremely relaxed muscles, to the point of respiratory arrest. He then placed the cat into the sealed box and used a hand-operated piston to manually control the pressure. The experiment was successful and showed that controlled pressure in a sealed environment could induce respiration.
This is also true for humans. When a person has respiratory arrest, he or she can get into a porta-lung to be resuscitated. With the increase in air pressure, it induces respiration and gets the lungs moving. Is positive pressure a better way of resuscitation? It is faster, I agree, and in an emergency faster is better. However, I am going to be controversial and say that one could be resuscitated just as quickly in a Porta-Lung. It is only a matter how fast can you get the patient inside the chamber, fasten the collar securely and turn the machine on to breathe. When I get in the machine tonight, I am going to time this procedure and see how long it takes. To continue being controversial I am going to pose a question: Was replacing negative pressure with positive pressure as the primary means of resuscitation good for the person’s health? I will answer this controversially and say “No, in the long run it is not good for one’s health – not overall. Why? Because positive pressure can damage the lungs, but not only that, it weakens the lungs and makes them lazy. After awhile of being on positive pressure, the lungs can’t do anything and then the person begins to think, “I need this air blown into my lungs because they don’t work and there’s no way I could ever breathe on my own.” Whether one tells himself this or someone in the medical field does, it is a defeatist attitude. It is also a mistruth. The lungs can work independently if they are given a chance.

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