If your body fights against it, it's dyspnoea. The terms are often used interchangably but technically they are different things. Dyspnoeic people are heavy smokers with COPD, people with fluid on their lungs, or with other lung disease..
It's a technicality though really, hah. You can get dyspnoeic on opioids if you take too much, but equally you can be calmly hypoventilating and not even realise/pass out..