"You should never give oxygen to a patient with Chronic Obstructive Pulmonary Disease (COPD)". It's an age-old myth and more than anything it is wrong and endangering the lives of patients everyday.
When I was a Student Nurse I explicitly remember being told by many, many Nurses, that putting oxygen onto a patient with COPD will cause them to retain carbon dioxide (CO2), remove their hypoxic drive and promptly send them into irreversible type 2 respiratory failure. This is partly true, but it is missing several pieces of information.
Let me start by saying, that not all COPD patients are CO2 retainers and chronic CO2 retention only stands at around 20% of patients with a chronic respiratory disease. Even then only a marginal PC02 increase can be detected with know retainers on 100% O2 for 20 minutes (Wilson, 2012). Acute CO2 retention is a possibility for ALL patients not just those with COPD.
I cannot stress to you enough - If your patient has low saturations - give them oxygen! In an emergency situation when your patient is acutely unwell, and/or their oxygen saturations are below any specified values for that individual patient, start at 15L via a non-rebreathable mask and titrate downwards as able, the saturations you are aiming for should be specified by a medic. You should never withhold oxygen from any patient when they urgently need it, as emergency Patient Group Directives (PGD's) are in place to implement this treatment, and guide your patient/oxygen management with support from the Resuscitation Council guidelines. You should ensure medics are made aware ASAP and an arterial blood gas (ABG) is completed, this is to assess for adequate oxygen saturation and to monitor for hypercapnia.
Ultimately it falls down to this - low oxygen saturations are going to cause multi-organ damage and cardiac arrest through hypoxic damage much, much faster than CO2 retention. Plus CO2 retention is, in most cases, reversible.
"You can reverse hypercapnia, you can't reverse death" is something that should be taught to Nurses and Students around the world in order to prevent unnecessary deaths. A fantastic fact sheet about COPD and CO2 retention can be found here.