Should COPD patients eat low/ high protein, carbs, fat diets? And why for each? Also, what nutrients are beneficial to them? Thanks dr.!

Studies have shown.. A high fat, moderate protein, low carbohydrate diet may improve lung function. Fruits and whole grains may also help. As for nutrients, vitamin c, vitamin e, ?-carotene, and selenium intake may be beneficial due to being antioxidants.
Emphysema. A balanced diet is important. I don't think there are any vitamins that have been shown to benefit lung function specifically. Obesity makes shortness of breath more pronounced although it doesn't directly worsen lung function. Typically as emphysema worsens people have problems maintaining weight and i encourage them to increase intake giving consideration to their other medical problems.