Types of Decompression Sickness (DCS)
Decompression sickness (DCS) is caused by inert gases leaving solution inside the body and forming bubbles. If allowed to grow sufficiently large, those bubbles present signs and symptoms, which allow DCS to be diagnosed. There are several different types of decompression sickness, depending upon the symptoms observed and the nature of the dive undertaken.
What are the five types of decompression sickness?
Type 1 DCS: Minor
Symptoms: Localized pain, skin itching (Pruritis) and skin rash (Cutis marmorata)
Type 1 DCS symptoms can arise within 10 minutes of surfacing from the dive and grow in severity over time. Pain is typically focused on a joint, often resulting from a bubble/s impinging on a nerve, but that is not always the case. The skin rash is distinguishable because it is sub-dermal; bubbles are causing damage in the minor capilleries beneath the skin; with close inspection it does not look like a contact rash on the surface of the skin.
These symptoms must always be treated as a medical emergency because, whilst seemingly minor, they can potentially progress into life-threatening Type 2 DCS.
Type 2 DCS: Cardiovascular/Pulmonary and Neurological
Symptoms: Severe pain, organ failure, decreasing levels of consciousness, cognitive ability, communication, mobility, dexterity, sensation and bodily control (including; breathing, bladder and bowel control).
Type 2 DCS is more severe. In these cases, bubbles are causing damage within the brain and central nervous system and/or impeding the function of organs. The effect within different organs will cause different symptoms; for instance an acculmulation of bubbles within the lungs will cause “chokes”; the diver will cough involuntarily as though they have a foreign object in their lungs.
Type 3 DCS: Vestibular
Symptoms: severe vertigo, nausea and localized ear/head pain.
Type 3 DCS is a bubble on inert gas, typically helium, within the inner-ear. This is caused due to Isobaric Counter-Diffusion if a technical trimix diver switches from a helium-rich gas mixture to a rich oxygen mixture during their ascent. Type 3 DCS has no been observed in dives shallower than 70m. Gas selection techniques are taught on full trimix courses to avoid this risk.
Non-emergency types of decompression sickness
Type 4 DCS: Osteopathic
Symptoms: long-term degeneration of the bones
Dysbaric Osteo-Necrosis (DON); is a long-term condition where frequent and repeated exposure to hyperbaric conditions (increased pressure) and variation(pressure changes) causes necrosis (death/brittleness) of the skeletal bones.
Sub-Clinical DCS: Decompression stress
Symptoms: post-dive lethargy, reduced vitality, somnolence/sleepiness, general malaise
Sub-clinical DCS, aka decompression stress, is the physiological effect of excessive micro-bubbles within the body after diving. As these symptoms do not consitute an injury or medical emergency, this level of DCS is disregarded medically and rarely included within the types of decompression sickness.
It is proven that micro-bubbles always do occur in our bodies on the ascent from scuba dives. We can also accept that those bubbles may not grow to sufficient size to cause immediate physical harm and present diagnoseable/clinical symptoms of decompression sickness.
Medically, the frequency of stable (not growing) micro-bubbles is largely irrelevant to diagnosing decompression sickness. Unless they are able to accumulate and ‘merge’ to form larger bubbles, those micro-bubbles will not cause a sufficiently intense problem to register on the victim.
Sub-clinical DCS may be suspected if the diver observes otherwise inexplainable symptoms after their dives. It can only be confirmed through ultra-sound measurement of micro-bubble size and number.
About The Author
Andy Davis is a RAID, PADI TecRec, ANDI, BSAC, and SSI-qualified independent technical diving instructor who specializes in teaching sidemount, trimix, and advanced wreck diving courses.
Currently residing in Subic Bay, Philippines; he has amassed more than 10,000 open-circuit and CCR dives over three decades of challenging diving across the globe.
Andy has published numerous diving magazine articles and designed advanced certification courses for several dive training agencies, He regularly tests and reviews new dive gear for scuba equipment manufacturers. Andy is currently writing a series of advanced diving books and creating a range of tech diving clothing and accessories.
Prior to becoming a professional technical diving educator in 2006, Andy was a commissioned officer in the Royal Air Force and has served in Iraq, Afghanistan, Belize, and Cyprus.
Originally posted 2018-11-05 06:10:48.