50-year-old former Australian cricketer Ryan Campbell has been in a coma since Sunday after suffering a heart attack while at a playground with his children.

"Cambo is currently in intensive care in a London hospital after suffering a heart attack on Sunday," his friend and former colleague Gareth Parker said on Perth radio station 6PR on Tuesday morning.

"As of 45 minutes ago, he was still unresponsive and in a coma - though he has, under the care of his doctors, made some attempts, successfully, to breathe on his own."

Having to lay down after having trouble breathing, it was the work of a passerby, who gave aid and completed a course of CPR, that helped Campbell until the ambulance arrived.

"Ryan had a pulse when paramedics arrived about 15 minutes later, he has been in hospital since," Parker said.

"He has begun partially breathing on his own, his blood pressure is good, so those are good signs - doctors don't believe there's damage to the heart but they haven't been able to figure out exactly what's going on just yet."

Playing in the golden era of Australian cricket, Campbell was stuck behind Adam Gilchrist for the Australian wicket keeping job, playing only two ODI matches for Australia in 2002.

One of the first to use the now-famous 'ramp shot', Campbell floated around as a batting coach post-career. Currently, he is the head coach of the Netherlands national cricket team.

The heart attack comes as a surprise for those who knew the 50-year-old father.

"I saw him last week, and he looked fit as a fiddle," Parker said.

Spending one more night in an induced coma, doctors will attempt to bring Campbell out on Wednesday morning (AEST) according to reports.