Mike the only advice I have-if someone hasn't' already mentioned it-is to be sure the oxygen machine has a humidifier in it, otherwise you tend to dry out quickly and cough like crazy.
Usually supplied separately. Less than $10 for bottle and short adapter hose.
https://www.amazon.com/s?k=concentrator+humidifier+bottle&crid=O2GDK9TW932H&sprefix=concentrator+humidifier%2Caps%2C147&ref=nb_sb_ss_ts-doa-p_1_23
https://www.amazon.com/Salter-Labs-Humidifier-Connector-Concentrator/dp/B06XH3VYP2/ref=sr_1_8?crid=O2GDK9TW932H&keywords=concentrator+humidifier+bottle&qid=1669561590&sprefix=concentrator+humidifier%2Caps%2C147&sr=8-8
