Most Stage-IV COPD patients require more oxygen. But it can also be used if the patient notices greater shortness of breath or if the oxygen level in their blood falls below 90% on a regular pulse oximeter. Right-sided heart failure can be avoided with enough oxygen.

According to the Canadian Lung Association (CLA), carbon monoxide levels are cut in half compared to smokers after quitting smoking for eight hours. Therefore, if you stop smoking, your breathing will significantly improve within 2–7 months.

1. Mild COPD-No symptoms: During stage-I COPD, you don’t feel difficulty in breathing unless you are walking fast, hiking, or running.
2. Moderate COPD-Fewer Symptoms: During stage-II COPD, you feel breathing difficulty while walking on a ground level and you may also feel the need to stop and breathe every few minutes.
3. Severe COPD-More Symptoms: Stage-III COPD makes it difficult for you to breathe while completing everyday tasks (e.g. dressing, toileting, and grooming).
4. Extreme COPD-More Symptoms: The final and most severe stage of COPD is stage-IV. Even when resting or sitting, you may have shortness of breath in the last stages of COPD. Heart or lung failure may potentially result from COPD in stage IV.