Ask an Instructor - June 2007
June 2007
By Michael Ange
Q: I have adopted a breathing pattern where I inhale fully and then hold my breath for three to five seconds before exhaling in order to save air. I am very careful to use this technique only under ideal circumstances and never in shallow water because of the risk of barotrauma. Is this technique safe?
A: No, it's not safe at all. What you are describing is called skip breathing, and some divers mistakenly believe that by holding an inhaled breath they will get a more efficient use of the oxygen it contains. Unfortunately, your body doesn't work that way. Your technique only adds risk of a lung overexpansion injury, and it doesn't conserve air.
Here's why: Gas exchange takes place in a very small part of the lungs called the alveoli. Within an extremely short span of time, these capillary beds have taken on all the oxygen they can hold and given up all the waste gases they were carrying. Holding your breath past this point only backs up the system and actually leads to a higher concentration of carbon dioxide in your bloodstream, which in turn will lead to carbon dioxide poisoning or hypercapnia. You will actually use less air in the long run by developing a rhythmic deep-breathing cycle while diving. With time, it will become a reflex--just like breathing on the surface.
Q: I read your advice to practice basic drills at the end of a dive to stay proficient. I recently purchased my first weight-integrated BC. I'd like to practice donning and doffing it. Are the techniques the same now that I'm not wearing a weight belt?
A: The techniques are the same, but your BC will react differently now that your ballast weight is fixed to your gear instead of your body. If you performed this drill on the surface with your old BC, you no doubt noticed that you tended to sink and your BC tended to float when you removed it. No mystery there--it had all the positive buoyancy and you were wearing all the lead. With your new weight-integrated BC, you will find that removing the jacket may make you more buoyant (especially if you're wearing exposure protection), and the BC (as long as it's properly inflated) should maintain about the same level of buoyancy.
On the bottom, you have a bigger challenge. If there's little or no air in the bladder, your weight-integrated BC will have a tendency to remain firmly on the bottom, while you will have a tendency to float immediately toward the surface away from your regulator and tank. That's why it's critically important that you never let go of the BC once you remove it.
If you have never tried these skills with your weight-integrated system before, I strongly suggest that you practice them in a shallow-water pool before moving to deeper water. It's also a good idea to obtain the assistance of a divemaster or instructor when you try them for the first time in open water.
Q:What's the difference between limited-penetration wreck diving and full-penetration wreck diving?
A: The answer to this question is rooted in the entirely different philosophy of technical diving as compared to that of recreational diving. Recreational divers are trained to surface when something goes wrong. In technical diving, there is usually some obstacle that prevents direct ascents to the surface (e.g., a decompression obligation or an overhead environment), so technical divers are trained to deal with problems while staying submerged. Limited wreck penetration, then, is the recreational version of exploring a wreck's interior while full penetration is the technical version.
Limited-penetration dives are done in wide-open areas that are free of debris, hazards and obstacles, and are typically conducted in areas of the wreck we would call a simple swim-through. This means that you can swim in one side and directly out the other side or that you restrict your movements to the area of ambient light that enters through a single opening. In these environments, within just a few seconds, you can be back in open water, and the odds of becoming entangled or entrapped are extremely low.
The technical wreck diver, on the other hand, is trained and equipped to deal with many different eventualities in an environment where it may take him several minutes or longer to reach open water. Because this may include decompression obligations, full-penetration divers often carry larger air supplies and redundant first- and second-stage regulators. They are also trained on how to deal with other wreck diving hazards including entanglement and silt-outs.
Q:During a long dive, my throat gets very dry and scratchy--so much so that it makes me cough. What can I do to keep this from happening?
A: The problem you describe is common and is a direct result of the filtration process used to purify the air in your scuba tank. The process removes virtually all of the moisture content in the air, but breathing that bone-dry air can irritate your mouth and throat. You can reduce the impact by staying well hydrated before and after the dive. By drinking plenty of water--not coffee, tea or soft drinks--you will thin the mucus in your throat and nasal passages so they don't dry up as quickly.
Many divers also find relief by switching regulators. Models such as the Sherwood Oasis have moisture-retaining metal fins built into the second-stage case in order to alleviate this very problem. Exhaled moisture condenses on the metal and helps humidify the incoming air when you inhale. Regulators with an all-metal second-stage body will also have this effect, but the Oasis design puts the fins directly in the air flow and provides the maximum advantage.
Q: My next dive trip is to a destination that's notorious for lost luggage. I don't want to miss a day of diving--any tips?
A: In my experience, very little luggage is ever truly lost forever, but I am familiar with a number of dive destinations where, due to the logistics of numerous connecting flights, bags may be delayed by a day or two. The best way to prevent any lost dive time while you wait for wayward bags to arrive is to plan for the possibility and make the best use of your carry-on luggage. I always travel with my regulator, computer, mask, a bathing suit, a spare pair of shorts and a couple of T-shirts in my carry-on bag. If my bags are delayed, I can always get by with a rented BC, wetsuit and fins. You can usually beg, buy or borrow soap, shampoo, toothpaste, etc., but now that the Transportation Security Administration has relaxed the liquids and gels restrictions, you can also pack a quart-sized freezer bag filled with travel-sized toiletries. It's a good idea to pack any prescription medications and eyewear in your carry-on bags, too.
A strategy to help ensure you and your bags arrive on the same plane is to avoid tight connections between flights. If you are running through the airport to catch the next plane, that means that someone else has to be running across the tarmac with your bags, and that's not usually going to happen. For layovers in larger airports, I always look for at least a one- or two-hour time window between flights.
If your bags are delayed, you can speed their progress to your doorstep with a simple duct-tape label. Clearly print your first and last name, the resort destination and the phone number of the resort. Finally, pack a good attitude. Stuff happens, so go with the flow and don't let it ruin your vacation.
Got a question you need answered?
E-mail it to edit@scubadiving.com, or write to Ask An Instructor, 6600 Abercorn St., Suite 208, Savannah, GA 31405.
June 2007
By Michael Ange
Q: I have adopted a breathing pattern where I inhale fully and then hold my breath for three to five seconds before exhaling in order to save air. I am very careful to use this technique only under ideal circumstances and never in shallow water because of the risk of barotrauma. Is this technique safe?
A: No, it's not safe at all. What you are describing is called skip breathing, and some divers mistakenly believe that by holding an inhaled breath they will get a more efficient use of the oxygen it contains. Unfortunately, your body doesn't work that way. Your technique only adds risk of a lung overexpansion injury, and it doesn't conserve air.
Here's why: Gas exchange takes place in a very small part of the lungs called the alveoli. Within an extremely short span of time, these capillary beds have taken on all the oxygen they can hold and given up all the waste gases they were carrying. Holding your breath past this point only backs up the system and actually leads to a higher concentration of carbon dioxide in your bloodstream, which in turn will lead to carbon dioxide poisoning or hypercapnia. You will actually use less air in the long run by developing a rhythmic deep-breathing cycle while diving. With time, it will become a reflex--just like breathing on the surface.
Q: I read your advice to practice basic drills at the end of a dive to stay proficient. I recently purchased my first weight-integrated BC. I'd like to practice donning and doffing it. Are the techniques the same now that I'm not wearing a weight belt?
A: The techniques are the same, but your BC will react differently now that your ballast weight is fixed to your gear instead of your body. If you performed this drill on the surface with your old BC, you no doubt noticed that you tended to sink and your BC tended to float when you removed it. No mystery there--it had all the positive buoyancy and you were wearing all the lead. With your new weight-integrated BC, you will find that removing the jacket may make you more buoyant (especially if you're wearing exposure protection), and the BC (as long as it's properly inflated) should maintain about the same level of buoyancy.
On the bottom, you have a bigger challenge. If there's little or no air in the bladder, your weight-integrated BC will have a tendency to remain firmly on the bottom, while you will have a tendency to float immediately toward the surface away from your regulator and tank. That's why it's critically important that you never let go of the BC once you remove it.
If you have never tried these skills with your weight-integrated system before, I strongly suggest that you practice them in a shallow-water pool before moving to deeper water. It's also a good idea to obtain the assistance of a divemaster or instructor when you try them for the first time in open water.
Q:What's the difference between limited-penetration wreck diving and full-penetration wreck diving?
A: The answer to this question is rooted in the entirely different philosophy of technical diving as compared to that of recreational diving. Recreational divers are trained to surface when something goes wrong. In technical diving, there is usually some obstacle that prevents direct ascents to the surface (e.g., a decompression obligation or an overhead environment), so technical divers are trained to deal with problems while staying submerged. Limited wreck penetration, then, is the recreational version of exploring a wreck's interior while full penetration is the technical version.
Limited-penetration dives are done in wide-open areas that are free of debris, hazards and obstacles, and are typically conducted in areas of the wreck we would call a simple swim-through. This means that you can swim in one side and directly out the other side or that you restrict your movements to the area of ambient light that enters through a single opening. In these environments, within just a few seconds, you can be back in open water, and the odds of becoming entangled or entrapped are extremely low.
The technical wreck diver, on the other hand, is trained and equipped to deal with many different eventualities in an environment where it may take him several minutes or longer to reach open water. Because this may include decompression obligations, full-penetration divers often carry larger air supplies and redundant first- and second-stage regulators. They are also trained on how to deal with other wreck diving hazards including entanglement and silt-outs.
Q:During a long dive, my throat gets very dry and scratchy--so much so that it makes me cough. What can I do to keep this from happening?
A: The problem you describe is common and is a direct result of the filtration process used to purify the air in your scuba tank. The process removes virtually all of the moisture content in the air, but breathing that bone-dry air can irritate your mouth and throat. You can reduce the impact by staying well hydrated before and after the dive. By drinking plenty of water--not coffee, tea or soft drinks--you will thin the mucus in your throat and nasal passages so they don't dry up as quickly.
Many divers also find relief by switching regulators. Models such as the Sherwood Oasis have moisture-retaining metal fins built into the second-stage case in order to alleviate this very problem. Exhaled moisture condenses on the metal and helps humidify the incoming air when you inhale. Regulators with an all-metal second-stage body will also have this effect, but the Oasis design puts the fins directly in the air flow and provides the maximum advantage.
Q: My next dive trip is to a destination that's notorious for lost luggage. I don't want to miss a day of diving--any tips?
A: In my experience, very little luggage is ever truly lost forever, but I am familiar with a number of dive destinations where, due to the logistics of numerous connecting flights, bags may be delayed by a day or two. The best way to prevent any lost dive time while you wait for wayward bags to arrive is to plan for the possibility and make the best use of your carry-on luggage. I always travel with my regulator, computer, mask, a bathing suit, a spare pair of shorts and a couple of T-shirts in my carry-on bag. If my bags are delayed, I can always get by with a rented BC, wetsuit and fins. You can usually beg, buy or borrow soap, shampoo, toothpaste, etc., but now that the Transportation Security Administration has relaxed the liquids and gels restrictions, you can also pack a quart-sized freezer bag filled with travel-sized toiletries. It's a good idea to pack any prescription medications and eyewear in your carry-on bags, too.
A strategy to help ensure you and your bags arrive on the same plane is to avoid tight connections between flights. If you are running through the airport to catch the next plane, that means that someone else has to be running across the tarmac with your bags, and that's not usually going to happen. For layovers in larger airports, I always look for at least a one- or two-hour time window between flights.
If your bags are delayed, you can speed their progress to your doorstep with a simple duct-tape label. Clearly print your first and last name, the resort destination and the phone number of the resort. Finally, pack a good attitude. Stuff happens, so go with the flow and don't let it ruin your vacation.
Got a question you need answered?
E-mail it to edit@scubadiving.com, or write to Ask An Instructor, 6600 Abercorn St., Suite 208, Savannah, GA 31405.
