The Real-Time Data Every Dive Computer Should Have

Max Weinmann, an Undercurrent subscriber and a critical care specialist in Atlanta, GA, writes, "I am grateful for John Bantin's timely thoughts on computer reliability and DCS avoidance (Undercurrent March). The challenge does, indeed, go beyond the ability to achieve mathematical manipulations of algorithms, which have always been difficult to test in humans, and in particular, those of us who present ubiquitous but growing challenges; namely aging, at least in physiological terms.

"This has been clearly demonstrated recently by the increasing morbidity and mortality of older divers. Change in weight, fitness, cardiovascular and organ health, and the indignation of a growing medicine cabinet replete with blood pressure, cholesterol, prostate and hormone replacement medication, to name a few. All of which collude to alter our physiology and the nature of gas uptake and release as we dive. Since the introduction of computers, we have largely become passive travelers of a tour governed utterly by the laws espoused by these algorithms, where personalization is based upon standard deviation manipulation rather than on the increasingly complex diversity of our own body physiology."

"Hence, adhering to computer-driven dives is not a guarantee of avoiding DCS. Specifically because our physiology is a dynamic environment constantly changing from moment to moment and compensating for changes in body fluid balance, chemical intake, hormone levels, external temperature, cardiac health, vascular sufficiency, etc. This leaves many computer algorithms wanting. "Indeed, as Bantin points out, 'The problem with all of this is no algorithm writer can write one specifically tailored for you. It's all based on hypothesis and Haldane's original research from more than 100 years ago.'"

As a diver and critical care/hyperbaric physician, I've seen firsthand the vagaries of DCS and the incredulity of divers, both young and old, who have developed the condition, despite adhering religiously to a computer profile a statistically-derived calculation that is incapable of taking into account individual factors such as dehydration; previous injury; the increased work the heart must perform in the setting of high blood pressure -- these are all important determinants of gas exchange, and hence, personal DCS risk.

"Only recently has Scubapro incorporated the monitoring of health factors, which brings this dynamic personalization much closer. By monitoring heart rate and air consumption (indirect measures of body 'work,' and hence, gas uptake and consumption), the algorithm that will determine Joe Diver's underwater profile is based upon actual biologic measurement and not statistics. For the first time, the profile will be based upon dynamic real-time measures of the individual diver's physiology, and not just the average of accrued statistical data. This is highly impactful in terms of safety, especially for the over-50 age group."

"While I have no commercial interest in this device, I am invested in diver safety. I sincerely believe the future of safe diving lies in real-time monitoring of an individual diver's physiological determinants of gas handling. That requirement transcends mere statistics. Diving is itself a dynamic and highly variable experience, as is our physiologic response, both between different divers, and with different dives for the same diver. It therefore demands a similarly dynamic computer able to integrate our own unique physiology in order to avoid morbidity and mortality."

John Bantin replies: "I absolutely agree that not enough divers bother to understand how their computer works or what it is really telling them. Too many people buy one, take it out of the box and blindly use it, without even appreciating what might be displayed. I met a diver recently who wanted his computer sent back to the manufacturer because it went into 'Error Mode.' He assumed it had gone faulty because it had locked him out from using it for 24 hours. I'm not entirely sure he believed me when I told him it was telling him that he was in error mode. He must have come up faster than the prescribed ascent-rate limit and not done the added time required on the safety stop. Luckily it had not been sent into 'SOS mode' -- although I once witnessed a diver try to hide his computer after it displayed SOS."