What do I mean by this statement ? As divers, we have many areas that can cause us to have equipment squeezes. But one of the main areas that affect most of us as divers is the squeeze that occurs from our face mask.
Unequalized air spaces can create problems. As mention the mask squeeze is common and occurs on very rapid descents when the diver neglects to equalize the mask.
Increasing hydrostatic pressure forces tissues surrounding the eye to swell into the uncompensated air spaces to fill the reduced air volume.
This swelling damages the capillaries, bruising the skin around the eyes and cheeks. Mask squeeze looks dramatic and severe, and the diver may not know it happened until they look in the mirror. This squeeze clears without complications, but the victim may want to consult an MD.
Other squeeze that may occur is when a diver uses a dry suit. If the diver forgets to add air to the suit and ignores the pinching, and continues to descend, may cause welts and injury.
During ascents the diver must remember to release the air from the suit, or risk a possible runaway ascent.
Sunday, May 17, 2009
Sunday, May 10, 2009
The Difference Between DCS and DCI
Most divers do not know there is a difference between Decompression Sickness (DCS) and Decompression Illness (DCI). There is a large difference.
First we must define what we mean by DCS. There is an overall term called Decompression Illness (DCI) which most divers get confused and call decompression sickness (DCS), the same. No it is not the same. DCI is the over all term that has 2 subjects below it: 1) DCS and 2) Lung Over expansion Injuries.
DCS refers to the conditions caused by inert nitrogen gas coming out of solution within the body. Lung Over expansion Injuries refer to those injuries that are caused by holding your breath on ascent.
There are basically 2 types of DCS: Type I deal with skin and pain only which would include the sub type a) Cutaneous DCS and b) Joint and limb pain DCS. While Type II covers the more life-threatening which are the c) neurological DCS and d) Pulmonary DCS.
A) CUTANEOUS DECOMPRESSION SICKNESS
Bubbles coming out of solution in skin capillaries can cause this type.
B) JOINT AND LIMB PAIN DECOMPRESSION SICKNESS
Bubbles growing around and inside the tendons, ligaments and related muscles are the immediate cause. Symptoms may be found in one place on the same limb or bilateral symptoms. This type may be serious because it can lead to a mores serious problem.
C) NEUROLOGICAL DECOMPRESSION SICKNESS
Effects on the nervous system produce some of the more serious cases in DCS. Bubbles in the nervous tissue may block blood flow "backing up" the system and reduce arterial flow in the affected areas. This affects the spinal cord most often often causing numbness and paralysis in the lower legs. It tend creeps upwards to affect from the neck down.
D) PULMONARY DECOMPRESSION SICKNESS
This is DCS that manifesting itself in the lung capillaries resulting in the onset of life-threatening symptoms. Silent bubbles reach the pulmonary capilaries defusing into the alveoli. In some cases, bubbles accumulate faster than they diffuse and can block and back up blood flow to the lungs. With less blood flowing to the lungs, the left side of the heart gets less blood, causing the heart rate to rise and a drop in blood pressure. With no treatment, the circulatory system may fail.
There are four type of Lung Overexpansion Injuries
A) AIR EMBOLISM
This is if air enters the bloodstream through a ruptured alveoli into the pulmonary capillaries.
B) PNEUMOTHORAX
If lung over pressurized tears at the surface, the expanding air leaks between the lung and the peural lining.
C) MEDIASTINAL EMPHYSEMA
This is where air accumulates in the mediastinum.
D) SUBCUTANEOUS EMPHYSEMA
Follows that of Mediastinal Emphysema as air seeks its way from the mediastinum, foloowing the path of least resistance into the soft tissues at the base of the neck.
First we must define what we mean by DCS. There is an overall term called Decompression Illness (DCI) which most divers get confused and call decompression sickness (DCS), the same. No it is not the same. DCI is the over all term that has 2 subjects below it: 1) DCS and 2) Lung Over expansion Injuries.
DCS refers to the conditions caused by inert nitrogen gas coming out of solution within the body. Lung Over expansion Injuries refer to those injuries that are caused by holding your breath on ascent.
There are basically 2 types of DCS: Type I deal with skin and pain only which would include the sub type a) Cutaneous DCS and b) Joint and limb pain DCS. While Type II covers the more life-threatening which are the c) neurological DCS and d) Pulmonary DCS.
A) CUTANEOUS DECOMPRESSION SICKNESS
Bubbles coming out of solution in skin capillaries can cause this type.
B) JOINT AND LIMB PAIN DECOMPRESSION SICKNESS
Bubbles growing around and inside the tendons, ligaments and related muscles are the immediate cause. Symptoms may be found in one place on the same limb or bilateral symptoms. This type may be serious because it can lead to a mores serious problem.
C) NEUROLOGICAL DECOMPRESSION SICKNESS
Effects on the nervous system produce some of the more serious cases in DCS. Bubbles in the nervous tissue may block blood flow "backing up" the system and reduce arterial flow in the affected areas. This affects the spinal cord most often often causing numbness and paralysis in the lower legs. It tend creeps upwards to affect from the neck down.
D) PULMONARY DECOMPRESSION SICKNESS
This is DCS that manifesting itself in the lung capillaries resulting in the onset of life-threatening symptoms. Silent bubbles reach the pulmonary capilaries defusing into the alveoli. In some cases, bubbles accumulate faster than they diffuse and can block and back up blood flow to the lungs. With less blood flowing to the lungs, the left side of the heart gets less blood, causing the heart rate to rise and a drop in blood pressure. With no treatment, the circulatory system may fail.
There are four type of Lung Overexpansion Injuries
A) AIR EMBOLISM
This is if air enters the bloodstream through a ruptured alveoli into the pulmonary capillaries.
B) PNEUMOTHORAX
If lung over pressurized tears at the surface, the expanding air leaks between the lung and the peural lining.
C) MEDIASTINAL EMPHYSEMA
This is where air accumulates in the mediastinum.
D) SUBCUTANEOUS EMPHYSEMA
Follows that of Mediastinal Emphysema as air seeks its way from the mediastinum, foloowing the path of least resistance into the soft tissues at the base of the neck.
Sunday, May 3, 2009
What is the Difference between
Steel and Aluminum Tanks ?
During this blog I am going to explain the differences between a steel tank and an aluminum tank.
There are many pros and cons concerning which tank you dive with, I will try to highlight those differences do when you do decide on buying a set of tanks, you will be better informed. Of course, as always, consult you local dive shop so you can see and touch the tanks you are considering buying. They will be able to fill in the blanks for you concerning which to buy and why. I hope that this information is helpful. Now let's get on with it.
The vast majority of tanks today are either steel or aluminum.
STEEL
Most are made from chrome-molybdenum steel. Steel cylinders are hard and therefore resistant to external damage. The draw back for steel, without proper care, they may rust (A chemical reaction that forms iron oxide), not only on the outside, but inside as well. One reason to have your tanks visually inspected every year. Highly recommended.
ALUMINUM
Softer than steel, ie can become damaged for external forces. Because of this, the walls are thicker. This makes them larger, heavier, and more positively buoyant than steel. Like steel aluminum also corrodes forming aluminum oxide. Unlike the iron oxide, it actually inhibits further corrosion.
SIZE AND WEIGHT
Aluminum weighs less than steel. Because they are not as strong, tend to be larger and heavier than steel. This can concern the smaller diver.
BUOYANCY
Because aluminum is larger they displace more water and often times more buoyant. As such divers will need more weight in their belt for a diver. At the end of the dive they tend to be more positively buoyant. Where as steel is negatively buoyant after a dive. The total difference can be 4-8 pounds.
VALVE TYPES
Most steel tanks are considered high pressure tanks, which mean that they may have the plus sign after the tank allowed pressure. This as you remember means that you can fill it up to 10 % higher than what is listed. Most steel tanks have what you call a DIN valve, where the first stage of your regulator screws into the tank. This tends to get a more secure fit. While the aluminum tanks have a K valve, where the first stage just rest against the tank stem, and is held in place by sir pressure.
COST
Steel tanks cost considerably more than aluminum.
There are many pros and cons concerning which tank you dive with, I will try to highlight those differences do when you do decide on buying a set of tanks, you will be better informed. Of course, as always, consult you local dive shop so you can see and touch the tanks you are considering buying. They will be able to fill in the blanks for you concerning which to buy and why. I hope that this information is helpful. Now let's get on with it.
The vast majority of tanks today are either steel or aluminum.
STEEL
Most are made from chrome-molybdenum steel. Steel cylinders are hard and therefore resistant to external damage. The draw back for steel, without proper care, they may rust (A chemical reaction that forms iron oxide), not only on the outside, but inside as well. One reason to have your tanks visually inspected every year. Highly recommended.
ALUMINUM
Softer than steel, ie can become damaged for external forces. Because of this, the walls are thicker. This makes them larger, heavier, and more positively buoyant than steel. Like steel aluminum also corrodes forming aluminum oxide. Unlike the iron oxide, it actually inhibits further corrosion.
SIZE AND WEIGHT
Aluminum weighs less than steel. Because they are not as strong, tend to be larger and heavier than steel. This can concern the smaller diver.
BUOYANCY
Because aluminum is larger they displace more water and often times more buoyant. As such divers will need more weight in their belt for a diver. At the end of the dive they tend to be more positively buoyant. Where as steel is negatively buoyant after a dive. The total difference can be 4-8 pounds.
VALVE TYPES
Most steel tanks are considered high pressure tanks, which mean that they may have the plus sign after the tank allowed pressure. This as you remember means that you can fill it up to 10 % higher than what is listed. Most steel tanks have what you call a DIN valve, where the first stage of your regulator screws into the tank. This tends to get a more secure fit. While the aluminum tanks have a K valve, where the first stage just rest against the tank stem, and is held in place by sir pressure.
COST
Steel tanks cost considerably more than aluminum.
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