Out of air with half-full tanks (http://cavediverharry.com/isolator/)

An article in a recent edition of DAN’s Alert Diver magazine warns of the perils of diving with an isolator valve you only think is open (link below). While your SPG may be telling you that you have phenomenal gas consumption, the reality is that you are sucking the right side of your doubles dry and may soon run out of air without warning. This story hit close to home for me, as I’ve witnessed this same situation twice…and experienced it once.

Each of these three situations had different root causes, and each teaches one or more lessons in its own right. Let’s take a look at each situation and what you can learn from it.

Open a partial turn?

This story goes back nearly 20 years, to what my friends call Harry’s Hogarthian Phase (i.e., the days before sidemount). Some of my fellow cave instructors were espousing an approach to diving manifolded doubles in which you opened your isolation valve just a partial turn. The idea was that, should something start to leak badly, you could isolate almost instantly and, thus, safe half your remaining air. This seemed logical to me, so I started doing it.

Everything worked fine until the Dive Rite gang and I made our first trip aboard Rick Pitts’ Ultimate Getaway. We were diving a wreck at 130 feet. I was using a set of manifolded steel 72s I’d put together just for this trip (a sweet setup if you do not need a lot of gas).

When diving manifolded doubles in caves, I’ve always made a practice of starting each dive by reaching back and confirming the position of all three valves while standing in chest-deep water. At sea, this wasn’t an option, so I did it while standing on a rocking boat deck.

Five minutes into the dive, I was marveling at my exceptional gas consumption. My SPG showed that I’d only used a couple of hundred pounds (actually a result of the tanks cooling).

Ten minutes into the dive, with my SPG not having moved past this, I decided Something Was Wrong and called the dive. In retrospect, what I was seeing should have been a clear warning of a closed isolator, and my response should have been to double check the position of all three valve turnwheels. However, being as I was a conscientious diver and had checked this prior to the dive, I assumed it had to be something else, like a faulty SPG.

Upon surfacing, I noticed that the first stage on my right post was moving rather freely. Out of curiosity, I tried detaching it from the tanks without first shutting down the valve. It came right off in my hand. This meant that, while I was fighting rough seas trying to get back on the boat, I was mere seconds from running out of gas (whoops!).

So what had happened? Apparently, prior to the dive, the boat lurched while I was checking the position of the isolator valve. As a result, I inadvertently closed the valve while thinking it was still open a partial turn.

Lessons learned: There are actually three:

·         To start, your isolator is like your other two valve turnwheels; it should be all the way open or all the way closed. In fact, except in an emergency, it should never be anything but all the way open. Yes, if need be, it will take a little longer to isolate — but it won’t put you at risk of being suddenly without air. A partially open isolator is too easily closed by accident.

·         Second, beware suspiciously good gas consumption. No, your breathing rate didn’t improve miraculously. Gas consumption that’s too good to be true actually means something isn’t right.

·         Finally, check your turnwheels. It should be the first thing you do if you don’t appear to be using any gas. Yes, we know you checked them at the surface; check them again. You may be surprised at what you find. And you may be able to save your life, if not the dive.

 

 

Make sure you fully understand your manifold before using it

These days, most cave instructors want students to have prior experience in backmounted doubles before using them in a course. This wasn’t always the case. Before tech diver training became widely available, a Cave Diver course often provided a student’s first introduction to doubles.

This was the case some years ago when I had a student in his second day of training on doubles. Prior to the first dive of the day, I had the student reach back and check all three valves, to confirm they were all the way on. He did — although his head blocked my view of exactly what he was doing when checking his isolator valve.

While exiting, the student suddenly flashed his light and gave me the out of air signal. I responded by immediately passing a second stage and switching to the other. I then reached back and checked his manifold, starting with the isolator.

You guessed it. It was fully shut, and he’d sucked one half of his doubles dry. Have you ever heard the noise a set of doubles makes when you open the isolator and equalize the pressure between tanks? It’s one you won’t forget.

So what happened? Two things:

·         Despite my having spent considerable time on manifold function and operation, the student failed to grasp the part about never shutting your isolator, except in an emergency. So, as the end of the previous day, the student dutifully shut down his outboard valve turnwheels…then did the same with the isolator. He then proceeded to attach the fill whip to the left post, leaving the entire right side of the doubles close ro empty.

·         When checking his valve turnwheels prior to the next dive, the student only check to see that the isolator turnwheel was fully turned in a direction…just not the right direction. Had he turned the valve in the opposite direction before checking to make sure it was turned all the way in one direction or the other, he would have heard the sound of gas moving rapidly through the manifold. I would have seen this, except for the fact his head was in the way.

Not only had this never happened to one of my students before, I’d never heard of it happening to anyone else’s. I’d tell you that I always made a point of checking this with students from this point one, but the fact is, after this student, I never had another student who wanted to learn in anything but sidemount.

Lessons learned: Four things here:

·         Leave the isolator valve all the way open, all the time (except, of course, in an emergency).

·         When filling doubles, check to make sure that both sides are being filled.

·         When checking turnwheel position prior to a dive, back off slightly on each valve before turning it all the way in the right direction.

·         And, finally, practice manipulating your manifold turnwheels until you are totally clear on which direction is clockwise (off) and counter- or anti-clockwise (on).

Complacency kills

It’s not easy admitting that you’ve screwed up or, worse, allowed a student to screw up. I can, however, take solace in the fact I’m not alone.

This story took place in 2000. It involves a regular dive buddy, Gareth, and another friend whom I’ll save embarrassment and simply refer to as “Herschel.” Herschel is a vastly more knowledgable and experienced cave diving educator than I am — and there are not a lot of people who can say that. Nevertheless, even the best among us can have a bad day.

On this particular day, Herschel had invited Gareth and me to accompany him on a dive in a system that, even now, not many people have seen. We were nearly 2,000 feet back, enjoying what, for us, was an entirely new cave, when we hear a voice behind us go, “Thit! Thummavabith!” We then heard the distinctive sound of gas rapidly rushing from one side of a set of doubles to the other, followed by a flashing of light and a thumbs-up signal, calling the dive early.

So what happened? It seems Herschel had made the same mistake my student had just a few years earlier; he’d filled his doubles with the isolator closed. And, in this case, he couldn’t claim that I hadn’t taught him about that.

Lessons learned: No one is bulletproof. Everyone makes mistakes. They say that, for the first 50 dives, most new cave divers are filled with trepidation, given the graphic images of death and destruction with which their instructors have filled their imaginations. Then, having survived their first 50 or more dives, they start to get complacent. They cut corners. They stop believing it can happen to them. This is when the most fatalities occur.

A friend once said that, if you are very lucky, you will get to make one big mistake…and survive. Whether or not you continue to survive depends on whether you learn from the experience or blow it off. Who knows? You might get lucky. But you probably won’t.

So what have we learned?

Perhaps we can best sum it up this way:

·         Isolators are like any other valve. Other than in an emergency, they need to be turned all the way on.

·         Don’t fill your doubles until you first check to make sure the isolator is turned all the way on.

·         Check to make sure all three turnwheels are all the way on at the start of the dive — but don’t assume that guarantees anything.

·         No, your gas consumption will not improve dramatically over the course of just one dive. If your SPG fails to drop more than just a couple hundred pounds within the first ten minutes, stop and check valve position. Fix any problems you find and call the dive if necessary.

·         You are not bulletproof — no matter how much experience you have. Never forget the cave is trying its damnest to kill you dead. Don’t let complacency help it along.

Diver’s air consumption appeared unbelievably good!

Diver’s air consumption appeared unbelievably good!

Buddies share air on ascent when one of them mistakenly thought he was running out of air.

REPORTED STORY:

The day started out as usual for a diving day; my buddy and I assembled our gear and everything went as normal. I dive with double 12 liter (~95 cu ft) tanks with a back plate. We used drysuits since this is cold water diving and we planned the first dive to a wreck at a maximum depth of 30 msw (98 fsw). Since my air supply is almost double that of my buddy, I tend not to check too often. I check my submersible pressure gauge (SPG) just once in a while as I know my buddy will run out of air much sooner than I would anyway. When I eventually checked my SPG it had just moved slightly (about 20-30 bars, ~300-400 psi). I thought this was very strange, but I knew my air consumption was starting to become quite good lately. Still, I thought this was way too little air consumed. At the safety stop, I tapped my SPG just to see if anything happened, but no, it still showed around 180 bars (~2600 psi) left.

When we came up, we started discussing this and we both wondered what could cause this extremely low consumption. We also put on my buddy's regulator and SPG just to see if the pressure was same, and it was. I thought that maybe since a guy at my club had filled my tanks, he may have accidentally put 300 bars (4350 psi) in my tanks and that I was a bit sloppy when I read the gauge before entering the water. I could remember that it was just above the major marker and I asked myself, was it just above 200 bars or 300 bars (3000 or 4000 psi)? To me this might explain such apparently low consumption.

We completed our surface interval and kitted up again; the pressure in my tank was 180 bars (2600 psi) and that was more than enough for a second dive. We planned the second dive to a max depth of 18 msw (59 fsw). An open water diver asked to join us which was, of course, no problem. The plan was that I would stay in front as I wanted to do some photography, the new diver would stay in the middle, and my buddy who is an instructor would stay in the back. The dive was uneventful for about 25 minutes when suddenly, I felt resistance when I was breathing.

I asked myself, "What is happening now?" Almost at that same time, I was suddenly unable to take a breath. Quickly, I turned around to find my buddy who was just 1-2 meters (3-6 feet) behind me. I gave the out-of-air signal and he grabbed for his octopus. It felt like forever, but the time from when I gave the signal to when I got my first breath from his backup could not have been long. For the first few breaths, it felt like his 1st stage did not deliver enough air; but when I managed to calm down more, breathing became easier. Even though I think we both reacted calmly and did not panic, I felt stressed until I was sure I could get air from my buddy's backup.

We signaled to the third diver that we would start the ascent to the safety stop. We did that and on the way I was starting to think about my backup around my neck. I purged it and there was still air coming from that. So at the safety stop, I switched to my backup and let go my buddy's octopus. We finished the safety stop and ended the dive.

At the surface, we started talking about what happened. My buddy thought, at first, that I was just "testing" him because I started using my backup in the safety stop. But when we started to look at my gear we found out what was wrong.

The isolator valve on the manifold was closed so I breathed the tank on my right side till it was empty and the amount of air that was used on my SPG was just the air I had inflated my drysuit with from the tank on my left side.

When I thought about it later, all the signs should have been enough to understand what was happening, but we still overlooked the real issue. Thanks to our practice of staying close together when we do cold water diving where the visibility is sometimes very poor, my buddy was not far away this time to help me out. We have talked about it several times after and we think we reacted in a good way when the situation became real. It shows that if you keep calm and don't panic then it is much easier to solve the problem you are presented with. The open water diver told us when we came up, he thought it was just a drill and not a real incident. What I have learned though is to always check everything and don't assume that things are as you left it.

COMMENT:

No-one expects to run out of gas but sadly, every year a number of divers panic when it happens unexpectedly even if their buddy is nearby. This diver signaled his buddy and secured an alternate air source before commencing his ascent. Later, he realized the cause of his apparent ‘out-of-gas' incident. No doubt when he opened his isolator valve a fraction then he would have heard the air moving from his left tank into his right tank until they were at equal pressure.

This is not an uncommon problem with isolator valves in manifolded doubles and a common method to prevent this problem is to perform shut-down drills before descending. Known as S-drills, this is where each diver reaches behind the head to shut down then fully re-open each valve. In this particular case it appears the divers did not check all their valves and inflating the drysuit, (plus possibly cooling of the tanks), caused the pressure in the left tank to fall slightly during the dives, further masking the problem.

When wearing a set of manifolded doubles, divers might remember this advice: if your air consumption appears too good to be true, then check your isolator valve because it probably is.

~ Peter Buzzacott, MPH, PhD

Overweight divers put themselves and others at risk

By Patrick Roward

It’s been one year since your last vacation. You’ve worked hard and now you can’t wait to arrive in Key West and dive the USS Vandenberg. You’re on the dive boat heading out for the dive when you’re asked to buddy up with a guy who is 5 feet 10 inches tall and weighs 250 pounds. You think to yourself, If something goes wrong and this guy goes into cardiac arrest at depth, will I be physically able to help him? Or worse: If something goes wrong with my dive, will this person be physically able to help me?

Obesity is defined as an excessive amount of body fat greater than 25 percent in men and 35 percent in women. Another measurement to determine body composition is called a Body Mass Index, or BMI. A BMI is used to assess weight relative to height, and can help determine whether an individual is obese, overweight or underweight.

A DAN study, “Classification of DAN Recreational Diver Fatalities by BMI from 2002, 2003 and 2004,” showed that at its worst, divers with a BMI of 30 or greater — which is considered obese — made up 53 percent of the dive-related deaths, whereas divers with a normal or healthy BMI of 18.5 to 24.9 made up only 13 percent of these deaths. Still, the issue isn’t just about being obese, but the health-related problems that obesity can cause and how these health issues can affect divers. It has been documented that obesity places a person at a significantly increased risk for hypertension (high blood pressure), Type II diabetes, excess levels of serum cholesterol, stroke and cardiovascular disease.

“Prudent dieting and regular exercise should go hand-in-hand for divers,” according to a 1999 DAN report, “Cardiovascular Fitness and Diving.” “Older individuals who take part in recreational diving and have a family history of heart attack, especially at an early age, should receive appropriate evaluations to detect early signs of coronary artery disease.” In DAN’s “Diabetes and Diving — Update 2005,” it’s written that “individuals with Type II diabetes have generally been excluded from scuba diving because a possible loss of consciousness might pose a significant risk, affecting the diver’s ability to take care of himself/herself or his/her dive partner.”

What does all of this tell us? It tells us that, normally, scuba diving is a fun and relaxing activity, but that on occasion catastrophic events can and do take place. When these events happen, every diver should be able to take care of himself and his dive partner.

I believe it’s the responsibility of every diver to keep as healthy as possible. By allowing yourself to gain excess body fat and fall into poor health, you’re not only placing yourself in danger, but also your dive buddy and every diver who chooses to come to your aid if a problem should occur. If you choose to let your weight get out of control, then you also have to decide whether a day in the water is really worth your life or the life of other divers.

An exercise physiologist, Patrick Roward has more than 20 years working in the field of health and fitness, with the majority of his experience in cardiac rehabilitation, strength and conditioning of athletes, and health promotion.

It’s not a matter of weight, it’s a matter of fitness

By Marc Weiss

**** I love to scuba dive and have ever since I received my Open Water certification in 1995. Since that time, I’ve done 1,500-plus dives in some of the best diving destinations around the world. I am also 6 feet tall and weigh 265 lbs. By standard definitions I’m an overweight diver.

For several years I’ve worked out routinely with a personal trainer, focusing on strength training, and have had great improvements in strength and endurance — along with weight loss — from those efforts. On my off-training days I try to spend time on the treadmill working on my cardio, while watching some of my diving videos, but I must admit I don’t get that in as often as I should. Scuba diving is a major motivator for my workouts.

I might be an overweight diver, but I am certainly not an unfit diver. My trainer uses upcoming dive trips to motivate me during workouts. For example, when I told him I was going to Bonaire and planned to do many shore dives, we concentrated more on leg workouts to make it easier for me to do the entries and exits in my full gear, which includes lugging along my underwater video system.

I believe all divers need to dive within their training, experience, skill, comfort and fitness levels. I always consider these elements myself when I plan my dives. I also focus on this when I’m teaching any diving student.

I’ve seen many divers — both overweight and “normal” weight — who appear to be unfit to dive based on the above criteria. From my experience, it’s very difficult to tell from looking at the divers whether they are fit enough to dive.

During my two most recent trips aboard Aggressor live-aboards, I encountered examples of both types of divers. On one trip there were a couple of overweight divers (we’re easy to identify on the dive boats!) who had some of the best buoyancy skills I’ve ever seen, incredibly good air consumption and were great at finding all kinds of cool things on the dives. During our surface intervals, I learned they both had rigorous workout routines yet struggled with their weight, something I could certainly relate to.

On another trip there were several “normal” weight people who needed assistance getting their equipment to and from the dive platform due to a variety of knee, back and hip problems. In the water they were great divers, and out of the water very fun people to spend a week aboard a live-aboard.

I recently had a student who was barely able to pass his swim and treading water test, but he did complete the requirements with great difficulty. This student was also able to barely master other skills required to complete his confined water training. I recommended the student work with a trainer to improve endurance and overall strength for diving. No, this student wasn’t overweight, but he was unfit for diving.

From my experience, it doesn’t matter how much you weigh. What matters is whether you are fit to dive.

Marc Weiss is a PADI IDC Staff Instructor, U.S. Coast Guard Master Captain and award-winning underwater videographer.

Nylon-braided regulator hose diving emergency by Andy Davis

http://scubatechphilippines.com/scuba_blog/regulator-hose-diving-emergency/

Recreational scuba diving, patent foramen ovale and their associated risks

http://www.frogkick.dk/library/medicine/smw-09706.pdf

The Impacts Of Smoking On Diving By Art Ranz, DDS

Cigarette smoking is one of the largest preventable health and death risks in the United States. It receives enormous amounts of negative media attention and yet millions of people start smoking every year. Unfortunately, it is frequently difficult to have a prudent, scientific discussion about the risks of smoking with someone who is addicted to nicotine. The addiction leads smokers to rationalize or deny the risks of smoking. However, this `head in the sand` response allows them to ignore the obvious impact that smoking has upon their bodies and the more subtle ways it effects many aspects of their lives, such as scuba diving.
The effects of smoking are especially significant for persons who participate in scuba diving. A review of scientific literature about the body's reaction to smoking and nicotine addiction illustrates how smoking can effect diving performance. While the diving and health limitations imposed by tobacco use vary according to the degree of use, tobacco always has some impact on individual health.
The most extensive, long-term, prospective study on smoking and other health issues is the Framingham study. This ongoing study has followed 5,000 people for more than 34 years, providing a wide range of statistical information. For instance, the 30-year-old who smokes 15 cigarettes a day - or less than one pack - shortens his life by five years. Smokers experience a 20-fold increase in lung cancer and greatly increased cancer rates in other organs, including skin, bladder, pancreas, mouth and throat. Smokers have twice the risk of cardiovascular disease, 2.2 times the number of strokes and 3.5 times more intermittent claudication expressed as leg cramping due to a lack of circulation. At any given age, the risk of dying for any reason is twice that of a non-smoker. Smokers have seven times the normal incidence of airway damage and respiratory distress. Children who smoke beginning at age 14 only develop 92 percent of the lung function, on average, that a non-smoking child does. This loss of function is permanent. Obviously, efficient lung function is essential to managing stressful situations and promoting efficient inert gas removal from a diver's blood. Poor circulatory efficiency can have dangerous impacts on inert gas elimination and oxygen delivery to needy muscles, greatly effecting a diver's personal safety. Atherosclerotic plaques in blood vessels form twice as fast when smoking is added to a high fat diet.
There are great increases in the LDL (`bad cholesterol`) that reduces circulatory efficiency and complicates inert gas removal. Inert gas (especially nitrogen) appears to lodge in fatty deposits, creating likely sites for bubble congregation and growth. Furthermore, 90 percent of patients with infections after spinal surgery are smokers and bone marrow density in men is decreased almost 20 percent and in women 25-30 percent, while the incidence of back pain from a work related injury increases from one in five to one in two for smokers. Hyperbaric bone damage (osteonecrosis) has gained increasing concern among medical professionals as researchers strive to demonstrate the cause of occasional bone degradation. To be sure, reduced bone density due to smoking aggravates the problem and some researchers are suggesting a more careful analysis of the relationship between hyperbaric damage and tobacco smoking.

How does tobacco cause such dangerous repercussions?

There are four groups of dangerous substances present in cigarette smoke:

1. Carcinogens and co-carcinogens are mostly polycyclic aromatic alcohols that directly initiate cancer formation. These affect areas in direct contact with the smoke and also distant organs through absorption into the bloodstream.
2. Irritants cause immediate coughing and broncoconstriction, inhibit cilliary action in the lung and stimulate mucus secretion.
3. Chronic exposure to nicotine induces an increase in the number of nicotinic cholinergic receptors in the brain, causing structural and functional changes in the brain and nervous system. It induces tolerance and physical and psychological changes upon withdrawal. These are classic developments from an addictive drug.
4. Toxic gases are inhaled, including carbon monoxide, hydrogen sulfide and hydrogen cyanide.

Smoking related cancer is tragic, costly and largely preventable, but the direct impact to diving is often less obvious. By way of illustration, the irritants present within smoke induce a chronic inflammation of the alveoli causing the body to produce proteolytic enzymes that eat away at the alveolar wall. Cilia are microscopic hairs that fan and carry harmful particles out of the lung. The irritants present in smoke impede these cilliary actions. With the addition of increased secretions, the lung has now lost a significant part of its defenses from outside agents. Chronic bronchitis develops, making smokers more susceptible to emphysema, viral and bacterial infections. As this process continues over the years and more alveolar damage occurs, there is a loss of capillaries in the walls which causes `ventilation-perfusion abnormalities.`
This damaging chain of events leads to a reduction in the area of alveolar membrane available for gas exchange and also to perfusion of unventilated areas and ventilation of unperfused areas. In simple terms, gas exchange is compromised and air (or other gases) is not reaching the blood for exchange. General lung function is often severely compromised in the smoking population as is evidenced by several clinical measurements in the lung. The standard measure of lung function is the forced expiratory volume in one second or FEV1. This is the amount of air that can be exhaled in one second.
The Framingham study showed the FEV1 to be decreased to 80 percent of expected values in smokers. This decrement in lung function creates less efficient ventilation on exertion and decreases the force of the cough (a vital protective mechanism for the lung) and may indicate a general degradation of lung health. The forced vital capacity (FVC) is another common measure of lung function and measures the amount of air one can expel from a full inhale to a full exhale. On average, smoking reduces FVC by 10 percent in moderate smokers. A 10 percent reduction in vital capacity is a significant indication of lung dysfunction and an obvious deterrent to pulmonary exchange in decompression.
Nicotine is not only a powerfully addictive drug, but a potent pharmacological agent. Nicotine promotes platelet aggregation and fibrinogen formation, which are precursors to the clots that obstruct small blood vessels. An obstruction initiates negative repercussions that increases the risk of diving and decompression. The heart rate increases, elevating oxygen consumption and the shrinking of small blood vessels increases total peripheral resistance. The resistance, in turn, causes more problems such as increased blood pressure and poor circulation in the periphery of the body. Peripheral circulation involves the miles of very small blood vessels all over the body. The vessels are problematic in efficient inert gas elimination. For example, the extremities contain numerous areas of reduced circulatory efficiency such as the joints (responsible for the majority of decompression sickness). When divers begin to get chilled, a natural reduction in blood circulation to the peripheral system occurs to maintain a reasonable core temperature. Smoking exacerbates this problem as studies show that the circulation in small blood vessels is reduced 19 percent after just two cigarettes. Poor gas exchange and increased risk of decompression sickness results.

The Problem with Carbon Monoxide

It is important to understand the Oxygen Dissociation Curve when reviewing the impact of smoking on oxygen transport mechanisms. This curve illustrates the assimilation of oxygen in large amounts even with low oxygen pressures in the lungs. Hemoglobin picks up the oxygen from the lungs and transports it to the tissues where it is released. Several factors control how easily the oxygen is released from its hemoglobin carrier. Higher concentrations of carbon dioxide in the blood cause the body to react as if there is poor ventilation and a greater need for oxygen. This environment initiates the release of more oxygen to the tissues. Under these conditions the hemoglobin affinity for oxygen is reduced, making it easier for oxygen to be released. In reference to the Dissociation Curve, this condition is sometimes referred to as a `shift to the right` and results in a greater supply of oxygen to the tissues. However, a `shift to the left` prevents oxygen from being released to the tissues. This condition is prominent with the carbon monoxide accumulation that results from smoking.
The primary mechanism behind the risk of carbon monoxide impact is twofold. First it binds to hemoglobin 250 times better than oxygen, making a compound called carboxyhemoglobin. This compound replaces the oxygen in the hemoglobin molecule and prevents the leftward shift of the Oxyhemoglobin Dissociation Curve. The increased affinity of hemoglobin for oxygen results in a decrease in oxygen carrying capacity and impaired release of the oxygen once it reaches the tissues. Non-smokers have about one percent carboxyhemoglobin while smokers have close to 15 percent. To illustrate the severely harmful effects of CO in the blood, imagine that an individual has 50 percent of their hemoglobin bound to CO. Compare this individual with another person who has lost half of their hemoglobin (due to severely bleeding ulcers, chronic gastrointestinal bleeding or massive injuries, for instance).The individual who has 50 percent of their hemoglobin bound with CO will die. But, the person who has a 50 percent loss of hemoglobin will still not experience hypoxia while in a resting state.
Furthermore, chronic hypoxia (reduced oxygen) results from the smoking induced impairment of oxygen transport and causes the production of more red blood cells. The red blood cells are the containing mechanism for oxygen transport in the hemoglobin. The Framingham study has shown that smokers have a significant increase in the percentage of red blood cells in the blood (increased hematocrit). Normally the red blood cells are about 35-40 percent of the blood by volume. Smoking can cause this to increase by 20 percent, making the blood much more viscous, inducing obvious complications to efficient circulation. This problem is further aggravated by the pressures found below the surface and causes sludging of the red blood cells in the small capillaries, damaging the cells lining the blood vessels (endothelium).
The transport of hydrogen cyanide to the lungs during smoking creates additional decrements to health and diving safety. This noxious gas directly prevents use of oxygen by the cells by interfering with the cellular engine- the mitochondria. Even small amounts of hydrogen cyanide are deadly. The presence of this toxic substance causes direct injury to the lung by interfering with the alveolar enzymes normally responsible for maintaining the integrity of the alveolar membranes. Hydrogen sulfide is another dangerous substance in cigarette smoke and is a direct toxin to most all cell life, especially to tissues it directly contacts such as the lungs. The numerous impediments to a healthy circulatory and respiratory system establish an insidious cycle of unacceptable risk to safe diving practices.
For instance, when increasing environmental demands require the delivery of more oxygen, the smoker is at a serious disadvantage. An increased supply of oxygen in the inspired air does not help delivery of more oxygen to the tissues where it is needed. There are two ways to increase oxygen delivery with increased demand: increasing blood flow through the tissue and raising the coefficient of oxygen usage. The former is compromised by the inferior cardiovascular condition of the smoker (consider the number of serious atheletes who smoke). The latter is increased by two things that happen automatically: greater partial pressure of oxygen between blood and tissue (resulting from the increase in oxygen consumption in the tissues) and the rise in carbon dioxide as a byproduct of increased metabolism. This increase in carbon dioxide causes the hemoglobin curve to shift to the right and allow more release of oxygen. This typically beneficial reaction is countered by the smoker's CO poisoning and the shift back to the left. The really adverse effect of smoking is the 20-30 percent rise in peripheral resistance (closing or restriction of small blood vessels) caused by the presence of nicotine. Small blood vessels are where the exchange of gases takes place and a reduction of circulatory efficiency in this area may be significant. Reduced blood flow and impeded oxygen release prevent efficient oxygenation especially when it is needed most. Therefore, the simple act of smoking initiates circulatory reactions that place divers in harm's way. Whether from decompression illness risk or ineffectual response to stressful environments, the smoker intentionally places himself and his team at greater risk.

Understanding Smoking's Short Term Impact on Diving

Smokers and those who choose to dive with them should consider not only the long-term health impacts, but the immediate implications of smoking and diving. Consider the increase in sudden cardiac death, the reduced ability to absorb and deliver oxygen to the cells, the obvious cognitive impairment, the likely increased risks of decompression illness, the increased likelihood of lung overpressurization injuries and the many other dangerous effects of smoking and diving. With all of the damage and risk associated with smoking and diving, what possible justification (save addiction) can there be to continue? Individuals with drug addictions, which is clearly what smoking is, must be encouraged to seek assistance and be freed from this damaging habit.
Consider that many `diving deaths` are thought to be cardiovascular in nature: cardiac arrhythmias, myocardial infarcts and strokes just to name a few. The smoker's incidence of these maladies is much higher. With this in mind, can a smoker be a responsible diving buddy? Can they help other divers out of trouble or are they merely likely to create problems? With increased anxiety, the heart beats faster and the breathing rate increases. Increased heart rate is the number one cause of increased oxygen use by the heart muscle and the heart of a smoker has a reduced ability to deal with the increased demand for oxygen. As a result, pulmonary exchange is poorer and utilization of breathed gases is compromised, leading to greater gas consumption and reduced ability to assist other divers. All dives are decompression dives. The list is long on how smoking causes decreased gas exchange and potential for decompression sickness. The ability of the lungs to filter bubbles is a major reason that every dive does not result in clinical decompression injury. The lungs are directly damaged by smoking. Ventilation, monitored by FEV1, is decreased, and the Forced Vital Capacity, or FVC, is decrease by at least 10%. With decreased pulmonary function, the lungs' function as a big bubble trap is compromised and the risk of decompression illness is increased.
Nicotine causes significant peripheral constriction, further compromising elimination of gas in the areas most difficult to get the inert gases out the small vessels and the area they perfuse. It causes increased platelet aggregation and fibrinogen production which only gives the body a head start on the same process that bubbles produce in occluding vessels and damaging vessel walls. One prominent theory of decompression illness suggests that bubbles in the bloodstream cause damage to the endothelium, the lining of the blood vessel walls, setting off a cascade of body reactions to repair itself. With nicotine in the body this process is aggravated and accelerated, causing platelets and blood clots to clog the small blood vessels. This reduces the body's ability to get rid of inert gasses. Nicotine gives the body a head start on the bad things that happen with bubble formation. The smoker has increased numbers of red blood cells per volume, or increased hematocrit, which sounds good, but actually makes the blood `thicker.` Increased atmospheric pressure from diving causes sludging of red blood cells in small vessels and the clogging of these vessels is aggravated by the increased hematocrit of the smoker. This is more bad news for perfusing the small vessels in the decompression part of the dive. Increased hematocrit may be directly involved with the endothelial damage which has been implicated in DCS. Carbon monoxide inhibits the transportation of oxygen mostly in its effect upon the hemoglobin and the hemoglobin disassociation curve. Smoking directly reduces pulmonary blood volume and the number of open capillaries in the lung, causing a ventilation to perfusion impairment with the obvious impairment of gas transfer at a time when every little bit is vital.
Acute nicotine withdrawal causes severe performance degradation, memory impairment, confusion, impulsiveness and slowed reaction time, just to name a few. Any of these are serious problems when simple decisions become life or death decisions under water. In a recent study of `undeserved hits` (a dive where supposedly all decompression limits are met and ascent rates are appropriate, but the diver still suffers from decompression illness), smoking and lung damage from smoking seemed to play a key role. Two groups emerged, those with intra-cardiac shunts and those without. Those with shunts had more brain symptoms and none smoked, while those without shunts, 50 percent smoked, a remarkable number. These divers experienced mostly spinal neurological sequelae and had deficits identical to divers with rapid ascents and pulmonary barotrauma. This implies that the smokers had occult lung disease that precipitated the pulmonary barotrauma giving more evidence of hindrance on the body's bubble filter. This makes perfect sense when considering the damage caused by smoking on the small airways and the alveolar walls which allow bubble to pass though the system instead of being filtered. Please think about these facts before picking up that next cigarette or diving with someone who smokes. If you smoke, see your doctor for help with overcoming the addiction. Make your diving safe and fun.

References

1. Freund Karen MD et al. The health risks of smoking, The Framingham study: 34 years of follow-up AEP Vol. 3, No. 4 July 1993 417-424
2. American Heart Association. Environmental Tobacco Smoke, Heart and Stoke Guide 1998
3. American Lung Association. Smoking Fact Sheet 1998
4. Sorle Paul. Influence of cigarette smoking on lung function at baseline and follow-up in 14 years: The Framingham study J. Chron Dis Vol. 40, No. 9 pp. 849-856 1987
5. Olofson J. Mortality related to smoking habits, respiratory symptoms and lung function. Eur J Respir Dis (1987) 71, 69-76
6. Wolf Philip MD. Cigarette smoking as a risk factor for stroke: The Framingham Study. JAMA Feb. 19, 1988-Vol 259, No. 7
7. Tager Ira B. Effect of cigarette smoking on the pulmonary function of children and adolescents. Am Rev Respir Dis 1985 131:752-759
8. Beck Gerald Smoking and lung function Am Rev Respir Dis. 1981 Feb;123(2):149-55.
9. Castelli William P. MD Diet, smoking, and alcohol: Influence on coronary heart disease risk. American Journal of Kidney Diseases, Vol. XVI, No. 4 Suppl 1 (October) 1990: pp 41-46
10. Kwiathkowski, Timothy C. Cigarette smoking and its orthopedic consequences. Amer J Orthop 1996 Sept 25(9) 590-
11. Slolnick, ET Exposure to environmental tobacco smoke and the risk of adverse respiratory events in children receiving general anesthesia. Anesthesiology 1998 May:88(5):1144-53
12. Anderson HR Passive smoking and sudden infant death syndrome: review of the epidemiological evidence. Thorax 1997 Nov;52(11):1003-9
13. Valkonen M, Passice smoking induces atherogenic changes in low-density lipoprotein. Circulation 1998 May 26;97(20):2012-6
14. Chan D Cigarette smoking and age related macular degeneration Optom Vis Sci 1998 July;75(7):476-84
15. Solberg Y The association between cigarette smoking and ocular diseases. Surv Opthalmol 1998 May-Jun;42960:535-47
16. American Lung Association Fact Sheet: Second Hand Smoke 1998
17. Hackshaw AK Lung cancer and passive smoking Stat Methods Med Res 1998 Jun;7(20):119-36
18. Armin Ernst, MD Carbon Monoxide Poisoning NEJM Vol. 339, No. 22, Nov. 26, 1998 pp. 1603-8
19. Timisjarvi J et. al. Effect of smoking on the central circulation at rest and during exercise as studied by radiocardiograpy. Mukliarmedizin 1980;19(50:239-43
20. Sommese Teresa MD et al. Acute effects of cigarette smoking withdrawal: Review of the literature. Aviation, space and Environmental Medicine Feb. 1995 pp. 164-7
21. West Robert Ph.D. What happened to anxiety levels on giving up smoking? Am J Psychiatry 154:11 Nov. 1997 1589-92
22. Wilmshurst P Role of cardio-respiratory abnormalities, smoking and dive characteristics on the manifestations of neurological decompression illness. Clin Sci 1994 Mar;86(3):297-303
23. Brodbeck John R. et al. Best and Taylor's Physiological Basic of Medical Practice Ninth Edition Williams and Wilkins Company. 1973

The Quarter Turn That Kills

At least one diver won’t be spending the holidays with family and friends this year, thanks to the dangerous practice of opening a scuba tank valve all the way, only to close it back a quarter turn. According to an article in the Daytona Beach News-Journal, an Edgewater, Florida, diver perished October 9 with more than 140 bar/2,000 psi remaining in his tank. His valve, however, was only open one-quarter turn.

The same thing happened to cave-diving pioneer Sheck Exley over four decades ago. Exley was descending, head-first, into a narrow crack in what is now Wes Skiles Peacock Springs State Park. Exley had accidentally closed his tank valve all the way, then opened it a partial turn, as he was taught. His regulator still breathed fine at the surface but, upside down at 20 m/65 ft, Exley found himself starved for air.

Exley ended up surviving what had been a very close call, and made it a standard of practice in cave diver training to either open valves all the way or fully close them. This has become a standard of practice in tech diver training as well. For reasons passing understanding, however, it has not become a standard of practice in recreational diving.

Where Does This Come From?

It’s common in industries ranging from welding to HVAC to never fully open a cylinder valve. The concern is that, if you try to force open a valve that is already open, you may damage the valve. Well, guess what? If your acetylene valve is only partially open, you may not be able to weld. If your scuba tank is only partially open, you may very well die.

In shallow water, a partially open valve may still be capable of delivering sufficient gas. At depth, however, the same valve setting can leave a diver starved for air.

Forcing a tank valve past its normal stopping point in either direction is a bad idea — even though modern scuba valves are a lot harder to damage than people realize. Curiously, you never hear dive instructors say, “Close your valve all the way and then open it a partial turn.”

In the final analysis, valve damage beats being dead.

So What Should You be Doing?

So that you live to enjoy another holiday:

• Open and close scuba tank valves only by turning them very gently. Stop as soon as you feel resistance. A valve turnwheel that does not turn easily requires service.

• Make sure your valves are either all the way open, or all the way closed.

• Be wary of well-meaning buddies and even dive boat crew checking your valve position for you. Even divemasters have been known to accidentally close a valve all the way, then open it a partial turn. Because this can work in shallow water, divers may not realize they are at risk until it is too late.

• To help ensure your valve is open all the way, take several deep breaths from your regulator while looking at your pressure gauge. The needle or reading should hold rock steady. If it drops with each breath, your valve is closed. If it fluctuates with each breath, your valve is only partially open. Do not dive until the valve is open all the way.

The next time you run into an instructor teaching this archaic and dangerous practice, set him straight. Better to ruffle some feathers than to bury a dead student.