"Yeah, there are some very sad, dark moments and you know we talk about it a lot.
"That's the best way of dealing with some of the situations is you talk."
William juggles his role as a pilot with his royal duties and on Saturday will travel to Canada with wife Kate and their children, Prince George, aged three, and 16-month-old Princess Charlotte, for an official eight-day trip.
The Duke and the captain shared a joke, with Mr Pusey saying about his colleague: "He's very good with advice and parenthood - in terms of good tips", and William laughed and replied "Dishing out parent advice".
The documentary has been released during National Air Ambulance Week and is described as a multi-media portrait of the EAAA and its staff.
It has been produced by BBC Future, which provides in-depth coverage of science, health and technology stories.
The piece also features still photographs of the Duke at work and he is filmed refuelling a helicopter and helping to take equipment on board.
He also talks the audience through the process he and the captain follow once in the air as they work out how best to reach someone in need.
The Duke and Mr Pusey also talked about the importance of "banter" during the working day. William said: "It helps de-stress and it also brings us together.
"Because if you share the same, in some cases, sad incidents then, if you can get over it together, by being able to talk about it in the future, being a close team you come away with a collective way of dealing with it together and (it) helps you move on to whatever you've got to do next."
The Duke spoke about the value of his work with the charity - something that was different to his role supporting the Queen and his charitable interests as a member of the Royal Family.
He said: "It's rewarding when I come here to do this job and I really look forward to coming here every day, whether it's at 5.30am or going to bed at two in the morning.
"The shift work is still exciting and challenging for its variety more than anything and the fact that I love working in a team.
"And that's something that my other job doesn't necessarily do. You're more out there on your own a little bit, but I very much enjoy working with the likes of James and the team and it's good fun."
William added that when he first began the job he was worried how people at an emergency would react to him.
He said: "Fortunately they don't really care who turns up as long as they're getting the care and the help that they need.
"I have to say I was a little bit anxious of some of that when I first started, because I didn't want to bring any chaos or any sort of unhelpfulness to the scene.
"And, actually, it's worked out better than I could possibly have thought."