There are circumstances under which a person should not recite the Shema: if they are in the presence of naked people, if they are themselves undressed, if there is nearby fecal matter, if they need to defecate, etc. (This site provides a list of Talmudic sources that discuss these issues.) And yet, there is also the widespread custom of reciting the Shema prior to one's death, but none of us can choose the circumstances under which we die.
My gut instinct is that if one were close to death but in a situation or an environment that would normally preclude reciting the Shema they should say it anyway - but is that correct? Are there any sources that discuss this, or that provide a logical (meta-halakhic) reason as to why it is the case? Furthermore, if it is the case, are there any other non-fatal circumstances to which this principle can be extrapolated?
(Obviously, if the purpose of reciting the Shema at the time of one's death - or not even the purpose, if the effect - is one of providing comfort, one might be able to waive whatever the halakha happens to be in pursuit of that aim. But that would also be to suggest that the bare halakha is not to recite it under those circumstances, and it's the halakha that I'm asking about - not about what people think that somebody should be able to do.)