There's no such law in CA, and in fact, the better rule is "no good deed goes unpunished." You're right, that tribal law isn't CA law.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
I'll expand just a bit on the previous answer and the quote that no good deed goes unpunished. There is typically no duty to rescue someone in distress; however, once someone elects to rescue someone, they are typically under a duty to use due care.
California has a limited "Good Samaritan" law located at Health and Safety Code section 1799.102. A 2008 Supreme court decision (Van Horn v. Torti) gave this section a very narrow reading. It was amended in August 2009 in an attempt to broaden it and it now purports to protect Good Samaritans unless they commit an act of gross negligence or willful or wanton misconduct. I am not aware of any litigation concerning the new version of the statute.
Some questions your facts still leave open -- is the situation you describe an "emergency" under the definition of HS 1799.102 and is supplying oxygen when you are not certified an act of gross negligence or willful or wanton misconduct?
The above answer does not constitute legal advice and does not create an attorney-client relationship. Every legal situation is different and you should consult with an attorney concerning the specifics of your matter.