Dr MIchael Bennett
Come on. Who among us hasn’t spat in their face mask, given it a wipe and pretended they were Mike Nelson from Sea Hunt (some of Lloyd Bridges’ finest work)? Or thrilled to the underwater shenanigans in the Bond films when 007 gets his oxygen pipe sliced by the villain and is left to a watery death until he’s ably assisted by a bikini-clad villain-turned-friend?
This is where divers watching Bond films have to suspend their disbelief. When you’re being chased underwater by a knife-carrying baddie with gold teeth (am I mixing my Bond villains?) it’s tempting to rise to the surface with a certain urgency. But lucky it’s just a film, because the speed with which these guys are ascending means they would all no doubt be diagnosed with varying degrees of decompression illness, or the bends, as it’s more commonly known.
This is where Dr Michael Bennett is here to help. Bennett is a diver who’s been deep underwater hundreds of times, so as a “divers’ doctor” he knows what divers need, he knows the risks they take sensibly and the ones they shouldn’t. He speaks their language and knows what can go wrong.
“They have a lot more confidence being treated by a fellow diver who understands that no one’s perfect and you do get low on air, and there is something wrong with your equipment that you should have known about but it crept up on you,” he says.
“We’re very careful not to abuse divers unless they really deserve it. And occasionally we still see people who have done the most stupid things you can imagine.
“A good example is a relatively experienced diver diving with his relatively inexperienced buddy and they plan a reasonable dive on the surface, but they see something interesting underwater and the more experienced buddy goes deeper and longer than planned and suddenly there’s a crisis because his less-experienced buddy has run out of air.”
Inexperienced divers breathe a lot faster, he says. “So one always has to be careful to monitor each other’s air consumption … So when we see someone who runs out of air at 35 metres, has trouble trapping his buddy’s attention, perhaps rockets to the surface, perhaps grabs hold of the partner and rips the air away from him and they both get into trouble and end up here.”
“Here” is Prince Henry’s Hospital in Sydney, where Bennett is academic head of anaesthesia, diving and hyperbaric medicine. He was instrumental in the introduction of, and oversees, the world’s largest square hyperbaric chamber, an eight-month-old facility that helped make Australia a world leader in hyperbaric engineering.
Experts in the field – many from the US – travel to Sydney to see it, and to hear about its extraordinary capacities in healing all sort of conditions, including the bends. One of the nastiest manifestations of the bends is paraplegia or quadriplegia caused by “bubbles” in the spine.
Bennett tells me of a couple of men he helped just avoid becoming paraplegics from rising to the surface too quickly. He sees no more than two or three cases a year of a severe form of decompression illness.
“We got them under pressure pretty quickly after they came out of the water, within two or three hours,” he says of the divers. “And when they went into the chamber they had rising weakness and numbness in their legs, clearly progressing to a level where they would be unable to move their legs and, if untreated, would almost certainly be permanently disabled, completely paralysed or very weak.
“Once they were in the chamber those signs rapidly improved. When they came out of the chamber they had an essentially normal examination.”
One diver was in particular danger. What were his chances of being a paraplegic for life? “I think worse than 50:50. He was very lucky: where he was diving, how well he was retrieved. The whole system worked well.
“He hadn’t gone that deep, about 35 metres. He surfaced too quickly. He was brought here as a matter of high urgency and seen very quickly in emergency.”
Four weeks later, Bennett followed up and the patient was completely well. Is he diving still? “We have advised him that that’s probably not a good idea. He took the point about his susceptibility to more injury. We take the view that a serious episode of decompression illness is likely to leave the spine – in his case – with small scars and less reserve, and if he was to have the same injury again it may not get the same result.
“People with serious neurological injury are generally advised that diving’s probably not the best for them and they should do something safer like sky-diving or hang-gliding.”
Turns out this is a moment of dark humour. How dangerous is diving? “Diving is actually a very safe sport. In Sydney we see around 50 divers a year with decompression illness or the bends. When I started in the early ’90s, that was closer to 100. Something’s improved, and I think it’s probably the use of diving computers to provide information to divers in real time about their risks.”
There are well over 500,000 dives a year in New South Wales. Nationally, he estimates it’s “in the millions”.
So, most divers are doing the right thing. But if they don’t, chances of surviving permanent crippling injury are much better now, and Michael Bennett has a lot to do with that.
Bennett is unassuming, gentle, softly spoken. His modesty is typical of the confidence those at the top of their fields exhibit. Bennett’s “baby” is a worldwide showpiece.
Due to its rectangular shape – the traditional hyperbaric chamber is cylindrical or spherical – this facility can fit 36 people at once, delivering hyperbaric oxygen as a medicine.
“The purpose of the chamber is to help cure people from a whole variety of diseases by the application of high-pressure oxygen,” he explains. As we sit in his room we are breathing 21 per cent oxygen but it’s easy to give people 100 per cent oxygen with a mask.
“In the chamber when we close the doors – it’s airtight inside – and we pump air in slowly, so the pressure slowly rises. Very similar to what a diver experiences underwater except the patient’s not underwater but the pressure is increasing as if they were.
“We generally take people to about 2½ times the normal air pressure until we give them 100 per cent oxygen. That results in them breathing 2½ times the normal atmospheric pressure that we normally breathe, and it’s all oxygen. This is a tremendously increased dose of oxygen and allows us to use some of the pharmacological properties that you just can’t get at normal doses that you’re used to seeing in hospitals or rescue situations.”
The process treats a wide range of conditions. “We’re constantly working to try and define the boundaries,” he says. “We treat divers with the bends, but much more commonly can treat people with bad or non-healing ulcers, usually in the legs due to diabetes or radiation treatment, or small blood vessel disease.
On injury: “… they should do something safer like sky-diving or hang-gliding.”
“We treat a lot of people with radiation damage all over their bodies. Radiation therapy is a common form of treatment for cancer, for a whole range of tumours, many in the head, neck and pelvis. The cure rate is constantly increasing as radiotherapists refine their treatments.
“That leaves us with a high number of people who have had quite a high dose of radiation and their cancer is cured but unfortunately in a small proportion – probably less than 10 per cent for most cancers – the normal tissues are so damaged, over time they break down and form ulcers and don’t heal because the tissue has lost the capacity to heal, being too damaged by the radiation.
“We’ve got tremendous potential for not only delivery of health care to a much larger number of people but to do research,” he says.
“The chamber is divided into four compartments. Unless we are overwhelmed with patients, it means chambers are free to work on experiments with equipment, sometimes with small animals.”
Bennett says rats and guinea pigs have been used to perform a series of experiments to help validate diving decompression schedules and to test how well divers’ computers protect them from decompression illness.
“We’ve done some work looking at whether young animals with immature bones have bone growth affected by being given hyperbaric oxygen, because that has been a question that has arisen relating to whether children should be scuba diving.”
Medical experts from around the world fly in to see it. “It’s a real drawcard,” he says. “Within the world hyperbaric medicine community, the Australian-designed and built square chambers are clearly the market leaders.”
It has generated a lot of interest, particularly from the US. “It’s certainly seen generally as the way of the future.”
Bennett first dived in 1976 in Long Bay, Sydney, as a 20-year-old medical student. A stint living in Britain curtailed his diving but on return home in 1989, he took it up again with a passion. He now dives 30 to 40 times a year.
I ask him what he loves about it. “On a purely physical level, the sense of weightlessness, in clear water … it’s like flying,” he says. “You can see the ground below and the sky above and you know you’re free to move up and down and left and right. It’s a very liberating feeling.
“Then there’s the life you can see down there. There are several sites where it’s common to go down in groups in search of sharks, non-dangerous ones. Grey nurses are very shark-like sharks; they look very impressive. There are pods of them relatively accessible, but we divers would say there are not as many as there used to be.”
Bennett is also the president of the Australian organisation that covers diving medicine, the South Pacific Underwater Medicine Society whose annual conference draws people from around the world. He recently attended the body’s annual event in New Guinea where he gave a keynote address on how deeper and more effective treatments for very bad decompression illness could be activated.
After the conference he spent a week diving. “It was magnificent. Warm water, lots of fish life, schools of barracuda, very large barracuda, very impressive.”
He says three-quarters of the staff in this unit are divers ... “which is what drew them to the unit in the first place”.
Bennett and his wife, Susan, often dive together. “I have to admit I twisted her arm into it the first couple of times. She didn’t find her learning day in the swimming pool all that exciting … But once she got out into the ocean for the rest of her course she was as taken as I was.”
He leaves us with a story that makes me want to take up hang-gliding.
“I have been on shark dives in the South Pacific where you dive with a high concentration of reef sharks. They are non-aggressive but you have to keep an eye on their behaviour. Once a four- to five-metre tiger shark appeared out of the blue and joined the smaller sharks. It gave us all something to think about. We retreated gracefully.”
But they didn’t race to the surface. “That’s dangerous, probably more dangerous than the shark.”