Thru IndAeMed@xxxxxxxxxxxxx: -------------------------------------------- On Fri, Apr 02, 2004 at 09:42:50PM +0500, ssmhialt@xxxxxxxx wrote: > > To my mind, there is no doubt that what Dilish has described is > typical post mortem lividity .... > [ For once Mish and Bish are singing the same tune. So much of the mail has been snipped off !] > > Now comes the question of explosive G forces which will force > blood in the extremities to the digits. This is a tricky > situation, because it the limbs fly out with digits outwards, > then the inertial reaction will tend to force blood out from > the torn vessels at the proximal end, rather than digitwards. > If, on the other hand, limbs tumble and rotate somehow (quite > possible with wind drag and aerodynamic forces), then the blood > may be pushed towards the digits with considerable force and > will cause rupture of capillaties and escape of hemoglobin into > extravascular space instantaneously. In this case, it does not > have to wait for hypoxic capillary permeability changes to > occur. Ultimately, the dark coloration which was noticed has to > be due to either reduced Hb per se, or one of its oxidation > (not oxygenation) products. > The term "Explosive G forces" is perhaps a bit misleading. What happens in an explosive fragmentation is physical disintegra- tion of tissue components within fractions of a second. It is a shock wave of immense magnitude for a very short pulse, which rip through the tissues followed by an evergy void state. Depending upon the type of explosion, there may be "after- waves" of a decaying sinusiodal pressure pattern. It may be noted that because of release of high amount of energy within a very short time span, it is invariably followed by an intense thermal wave, which contributes significantly to the instantenous chemical interactions, notably, oxidation with oxygen being provided from the air. It is pure physics and chemistry out here. No physiology. The moment forces exceed the stuctural strength of tissues they fragment along the lines of least resistace, with total structural disintegration, partially modified by available clothing. There is no time for hydrostaic shifts, or G induced vascular changes. Any and every cell may be structurally damaged with the pressure pulse, so obviously things like hypoxic pemeability changes as brought out by Mish are perhaps non-issues. It is a state of oxidation and other chemical processes (depending upon the type of explosion and the immediate environment) which would govern the final chemical composition and state of the remnant tissues. This is NOT lividity as explained in Forensic texts (which is a hydrostatic force based phenomenon), rather, a state after physical and chemical disintegration, due to forces explained above. As doctors, we have a natural tendency to find explanations as per principles of physiology and pathology, but in situations like this, it is absolute basics of physics and chemistry which may provide a better explanation. Just my POV Bish ======================================================================= To send messages to the full list please send to IndAeMed@xxxxxxxxxxxxx To view the archive of messages on this list please visit: //www.freelists.org/archives/indaemed/ To add/change/remove your addresses/names please write to Anirudh Agrawal at : anirudh_a@xxxxxxxxxxx Alternate List : IndAeMed@xxxxxxxxxxxx Webpage of this List at : http://www.AvMedNet.Net ISAM Web Page at: http://www.ISAM-India.org ----------------------------------------------------------------------- -----------------------------------------------------------------------