From owner-biophysics@net.bio.net Mon Feb 23 22:00:00 1998 Path: biosci!agate!logbridge.uoregon.edu!Cabal.CESspool!bofh.vszbr.cz!lyra.csx.cam.ac.uk!hgmp.mrc.ac.uk!guardian.dcs.warwick.ac.uk!warwick!leicester!usenet From: "Dr E. Buxbaum" Newsgroups: bionet.biophysics Subject: Re: Water Pressure and Human Body Date: Tue, 24 Feb 1998 13:33:28 -0800 Organization: University of Leicester (PCFS User) Lines: 38 Message-ID: <34F33CA8.3465@le.ac.uk> References: <34ee45c4.26064252@news.telepac.pt> NNTP-Posting-Host: pc47.msb.le.ac.uk Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01 (Win16; I) Ricardo V. Oliveira wrote: > > Can anyone answer these questions? > > What really happens when someone goes deep > under the water? > What is the maximum depth that a man can go under water? > What are the effects of the water pressure on the human body? Water pressure itself actually has little effect on the human body. There are a couple of problems related to pressure, which have to be dealt with. If you free dive, then the pressure difference between the water and your lungs make breathing through a snorchel more and more difficult and finaly impossible. You will need compressed air and a valve, which feeds you the air at the same pressure as the surounding water, so that you neither suffocate nor get blown up like a balloon. The next problem, as you get deeper, is nitrogen and oxygen toxicity. The higher partial pressure of nitrogen and oxygen in the compressed air force more of these gases to dissolve in your blood. These higher concentrations have first an euphoric, later narcotic effect on your nervous system. For greater depth, you therefore need to replace compressed air with a mixture of oxygen and helium, with the concentration of oxygen decreasing as you go deeper (so that the partial pressure of oxygen stays constant). Additionally, when you go up after a dive, dissolved gasses will be released from your blood stream. If you go up faster than these gases can be breathed out, bubbles will form in your blood vessels (like in an opend bottle of soda water), a very painfull and potentially fatal condition known as "the bends" (because victims assume a characteristic body posture to minimise the pain). You will therefore have to make frequent stops at different depths for pressure adjustment. If you go up very fast (faster than the air bubbles around you raise), the pressure in your lungs will exceed the water pressure, and your lungs might burst. This is a quite real possibility in diver who panic under water. .