What did actor John David Carson die of?

Famous TV host and comedian, Johnny Carson, died in Los Angeles on January 23, 2005 of respiratory failure from emphysema. He was 79 years old. In 1999 he suffered a heart attack and in 2002 he revealed he had emphysema. There was no public memorial service, but many people paid tribute to Carson, including late night hosts Jay Leno and David Letterman.