Why is it more difficult to start an iv on chf and copd patient?

Two reasons: Due to the nature of the illness, these patients are typically older with atherosclerotic hardened veins that may roll on insertion. Also, they tend to have a few previous hospital admissions that left many of their veins already violated and scarred.

Not necessarily: In any one with poor veins it is difficult to access. People with low BP and collapsed veins, it is even more difficult.