Image copyright St John Ambulance Service Image caption Mr Knowles has been a first aider at his church for more than 40 years 
 
 A retired nurse talked his trainees through saving his own life when he suffered heart failure during a CPR lecture. 
 
 David Knowles was delivering a first aid course to members of his Exeter church group when he started feeling unwell. 
 
 The 77-year-old said he felt dizzy and weak, and had to lie down. 
 
 He then instructed his trainees, who thought he was role playing, on what to do before he passed out. 
 
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 "I had just started my lecture and we were talking about cardiopulmonary resuscitation," Mr Knowles said. 
 
 "The more senior members of the group had asked for a demonstration...she thought I was role playing, but I told her it was real and that I was going to lose consciousness." 
 
 'I woke up weeks later' 
 
 Mr Knowles, a St John Ambulance volunteer, went into cardiac arrest, but his trainees called 999 and gave him CPR until an ambulance crew arrived. 
 
 "I'm told I came to, briefly, and was talking to the paramedics about my condition, but the next thing I remember is waking up in hospital, two and a half weeks later," he said. 
 
 Mr Knowles was alone setting up his lecture in the church rooms on 16 February for between 10 and 20 minutes before his students arrived. 
 
 St John Ambulance said if he had gone into cardiac arrest during that period, with no-one on hand to revive him, he would almost certainly have died. 
 
 At the Royal Devon and Exeter Hospital, Mr Knowles suffered a further cardiac arrest and a pulmonary embolism. 
 
 He was hospitalised for five weeks, and left hospital in mid-March. 
 
 Doctors feared he might have suffered brain damage, that his internal organs could have been affected by his ordeal and predicted he would need months of rehabilitation. 
 
 But medics say he is making excellent progress, is mentally alert and can walk unaided as he continues to recover at home in Newtown, Exeter. ||||| This was not a drill. 
 
 David Knowles had just begun a CPR training class in his local church when he suddenly felt quite awful. 
 
 Read: 13-Year-Old Certified to Perform First Aid and CPR Saves Little Boy Choking on Piece of Candy 
 
 He puddled to the floor, but managed to take his own pulse. 
 
 "Are you all right?" a student asked. 
 
 “I’m not feeling all right at all,” Knowles, 77, told his pupil. The former nurse was having a heart attack on the first day of his emergency training course. 
 
 First, he had to let the class know this was not a demonstration. And before he passed out, or died, he had to tell them how to help. 
 
 “The whole group was up on its feet, looking like they weren’t doing very well, either,” Knowles told InsideEdition.com Thursday during a phone interview from his home in Exeter, England. 
 
 Karol Chew, a fellow parishioner and also a former nurse, was taking Knowles’ class as a refresher course. 
 
 Knowles told Chew to call an ambulance. He said he was about to experience cardiac arrest and might not survive. He asked for his wife, Nova, to be notified, but stressed that she was not to hurry. 
 
 “She’d just had her gallbladder out and wasn’t supposed to run,” he said. 
 
 He asked Karol to remove his false teeth and put them somewhere safe. “I was beginning to get a bit foggy,” he said. 
 
 But he knew he had to try to stay awake. “I couldn’t really get stirred up about it,” he said, because he had to help Karol help him. 
 
 From that point on, he doesn’t remember much. 
 
 Read: Unconscious Woman Receives CPR from Bride in Her Wedding Gown: 'My Nursing Instincts Kicked In' 
 
 “I woke up two and half weeks later,” he said. He had been in a medically induced coma because the damage to his heart was serious, he said. “It was quite severe. I was more dead than alive when they got me into hospital.” 
 
 That was four months ago, and Knowles says he continues to improve. He exercises and keeps a close eye on himself. 
 
 He said Karol performed CPR after he stopped breathing. Without her, he doesn’t know if he’d still be alive. 
 
 “It really got bizarre, the whole thing,” Knowles said. 
 
 Doctors say he is in good health, and he is helping St. John Ambulance, where he volunteers, celebrate its 140th anniversary. 
 
 “I feel a lot better,” he said. 
 
 Watch: Coach Saves Man's Life by Doing CPR to 'Stayin' Alive' ||||| A group of first aid trainees thought their instructor was role-playing during a class on how to perform life-saving CPR as he had a heart attack during a lecture. 
 
 David Knowles, 77, began to lose consciousness as he told his students how to resuscitate people at his local church in Exeter. 
 
 Some of the group thought Mr Knowles was giving a demonstration as he lay on the floor feeling faint and unwell. 
 
 They managed to save the St John Ambulance volunteer's life after he told them what to do just before he passed out. 
 
 He told the BBC: "I had just started my lecture and we were talking about cardiopulmonary resuscitation. 
 
 "The more senior members of the group had asked for a demonstration...she thought I was role playing, but I told her it was real and that I was going to lose consciousness." 
 
 Mr Knowles suffered a cardiac arrest but survived because his trainees dialled 999 and performed CPR until paramedics rushed to the scene. 
 
 British Red Cross guide to basic first aid 
 
 The pensioner fell into a coma and had another heart attack after he was taken to the Royal Devon and Exeter Hospital. 
 
 He would have died at the scene if nobody was there to help him. 
 
 Mr Knowles said: "I'm told I came to, briefly, and was talking to the paramedics about my condition, but the next thing I remember is waking up in hospital, two and a half weeks later." 
 
 The retired nurse left hospital after five weeks and has since made "excellent progress" at his home in Newtown, Exeter, according to the BBC. 
 
 He could have suffered brain damage, but is said to be mentally alert and able to walk unaided.
– David Knowles was leading a class on CPR when he suddenly felt weak and dizzy. As the retired UK nurse lay on the floor, he realized he had little time to tell his students what to do before he passed out, the BBC reports. The group "had asked for a demonstration," Knowles says, and they thought they were getting one. When they learned this was no drill, "the whole group was up on its feet, looking like they weren't doing very well, either," Knowles tells Inside Edition. As the 77-year-old, who took his own pulse during the incident, started to "get a bit foggy," he instructed student Karol Chew to call an ambulance and take out his false teeth. Knowles knew he was having a heart attack and had to stay awake but, he adds, "I couldn't really get stirred up about it." Chew—a former nurse who was taking the class to brush up on her skills—began performing CPR after her teacher stopped breathing. "It really got bizarre, the whole thing," Knowles says. He came to briefly when the paramedics arrived, "but the next thing I remember is waking up in [the] hospital, two and a half weeks later," Knowles tells the BBC. He fell into a coma and later suffered another heart attack, per the Independent. The incident in front of his students took place in February. The local ambulance service for which Knowles volunteers says that if he'd been stricken before his students had arrived, he likely would have died. After five weeks in the hospital, Knowles was sent home to his wife, Nova, and doctors say he's making excellent progress. "I feel a lot better," he tells Inside Edition. (Did workplace bullying trigger a fatal heart attack?)