Q. What are the ‘Simanei Gosses” or signs of imminent death in our days? Blood Pressure? Heart beating?
A. The Remoh (E. H. 121, 7 and H. M 211,) identifies the symptoms of Gesisah as the bringing up of secretions of the throat, caused by chest and breathing difficulties and strain. Some maintain that the term “Goses” refers to the sounds of heavy respiration at that time (Oruch ).
Chukei Chaim (p.150) quotes a difference of opinion between Divrei Malchiel and Tzemach Tzedek as to what are the Simanei Goses on one drowning in water.
There is a debate between contemporary Poiskim as to whether these symptoms are essential for the state of Gessisah to begin or just the closeness to death creates it. (Igrois Moishe ibid – Treatment of the Terminally Ill, Tradition 30:3 (1996) p. 63).
Biur Halocho (329) mentions that one found with the skull ‘Merutzas’ or fatally fractured is a Gosses, and even if he is certainly to die, we desecrate Shabbos to extend it as much as possible.

Horav Shlomo Miller’s Shlita opinion is that Simanei Gosses in our days depend on the case and may indeed be difficult to determine. Competent Medical advise is necessary.

However in general, they are based mainly on the respiration of the patient.

Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a