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Technical Aspects PFD

DISCUSSION OF TECHNICAL ASPECTS OF RESCUE LIFEVESTS (PFDs)
                                                                                              - Jim Simmons
                                                                                                ACA Instructor

At the conclusion of our initial field reviews of Rescue PFDs completed in 2004, we indicated we would discuss specific information about the current styles, function, and construction of rescue vests. Here is that report.

[Note: for interested readers, Michael Croslin, the developer of the Reach System (rope retriever) and the Strong Swimmer's Belt, has written an article about the current status and evolution of rescue lifevests (PFDs) that appears in issue #62 of Technical Rescue Magazine (December, 2011)].

Rescue vests have evolved as hybrids of type III personal flotation devices (PFDs) and are designed to provide buoyancy and freedom of movement when paddling whitewater; yet, can be employed as a rescue tool. The primary difference between a regular vest and a rescue vest is the inclusion of a Quick Release Harness Belt (QRHS). A rescuer can attach to a rescue line and be belayed by a second rescuer for a rescue application, however, the entire QRHS must release under tension to allow the rescuer to become free of the rescue line but still wearing the PFD.

The USCG approval process is conducted and audited by Underwriter Laboratories (UL). Most testing is done at a laborator in calm water. Because of intended use a rescue vest may be subjected to in river rescue applications we see a need for the approval testing to be conducted in a whitewater river environment.

Factors in PFD Construction
--Buoyancy, and minimum flotation required by the USCG is 15.5 lbs. Most of the current popular rescue vests worn principally by kayakers and canoeists have flotation ranging from about 16 lbs to less than 18 lbs buoyancy. The Lotus P-Vest (16 lbs,7oz) offers an optional implant that fits into its center pocket giving 2 lbs, 8oz additional flotation. Refer to the heading on Trends and Styles in Vest Design.

 In our PFD review we found that some of the vests had only marginal buoyancy when river swimming in turbulent water. Swift moving water is quite different than calmer, slower waters. Because of the turbulent hydraulic effects of whitewater, a swimmer will be under water for periods of time regardless of the amount of flotation.

--Buoyant materials that don't absorb water. PE and PVC have been common foams used in vests. PE is more rigid, less expensive and has been the most environmentally friendly option in foam, whereas PVC is softer, with excellent recovery properties but more expensive. Another type being used is acrylonitrile butadiene rubber (NBR) which is soft and also environmentally friendly.
--Fabric and thread that is strong enough to withstand the rigors of whitewater use.
--Adjustment straps and hardware items that resist degradation from water and sun.
--Pockets that drain, are durable and do not protrude excessively when full of items.
--Shoulder adjustments that insure a snug fit and will not slip under tension.

--Correct fit--not only should a vest be comfortable for paddling but it should not 'ride up' the torso after being adjusted. This is expecially important when aggressively swimming because vests that ride up can impede progress or block vision of the rescuer in the water.
--Impact protection--a vest should have sufficient torso and side impact protection from falling or bmping into objects during water rescues.
--Webbing sewn into the shoulder straps and vest body should be integral to the vest.

Trends and Styles in PFD Design
Whitewater kayakers, open canoeists, sit-on-top paddlers, inflatable kayaks, etc., prefer a vest that allows freedom of movement and kayak paddlers favor one that doesn't interfere with the spray skirt. For big water rivers many rafters may prefer a higher profile, longer style that has considerably more buoyancy.

--Low Profile--these styles have large armholes and the buoyant material positioned lower on the torso. Examples: Astral 300 R, Lotus P-Vest, and Extrasport Pro Creeker.

--Short Waist, High Cut Models--in these models the buoyant material is positioned higher up on the chest, but they too have large armholes for freedom of movement. Some choices are: Stohlquist X-Tract, MTI Pro Play and Patriot, Lotus Rio Pro and Kokatat ProFit.

--Higher Profile (or longer style)--these vests have increased buoyancy and come in either full length models or short waist versions. Frequently used by boaters in big water (rafters, professionals, or rescue personnel), they have 22 lbs or more of buoyancy. Some examples are Extrashort HiFloat and Fury models; MTI Patriot ; and models by Force6 of Canada.

--Universal Fit--these styles accommodate a variety of ranges mostly from sizes 30-56 and are used in big water paddling, in rescue classes (fitting a variety of participants), or by rescue personnel. Examples: Stearns Versatile Rescue 1650 and Extrasport Universal Fit.

During the field reviews we raised several questions about differences we noted in the effectiveness of the flotation of the vests. We plan to conduct more field trials to determine a more suitable minimum flotation needed for self-rescuing in bigger water, or for performing a swimming rescue of another swimmer (either tethered or not).

Some reviewers reported they felt the short waist, high cut styles provided the most effective flotation when swimming aggressively. Because a man's center of gravity is higher up on the body as contrasted to a lower center in women, we want to learn more definitive information about different style vests and the flotation the provide, for both men and women paddlers.

A few companies make regular vests that specifically fit the female profile but of the rescue vests we've reviewed, only the Astral Buoyancy Company makes one for women, the WonderPro ($185). We also want to learn if low profile styles provide more effective flotation for women than other styles when swimming aggressively or self-rescuing. We'll report on what we learned at a later time.

How Vests Are Sized
Rescue vests are usually sized in three different ways. Regular sizes (S,M,L,SL, and XXL). Overlapping sizing is uaually S/M, L/XL, etc. and Universal Fit (one size fits all) usually ranges from sizes 30-56. It's important that the strap adjustment system not permit the vest to creep up the torso when swimming, when the vest is under tension, or after releasing the QRHS and while still swimming. Adjustment straps should also prevent gaps/spaces at the waist and chest areas to prevent water collecting when river swimming. A properly fitting vest will also minimize heat loss when paddling in cold environments.

The PFD field review indicated that regular sizes tended to fit more snugly without having gaps or spaces where water could collect. Overlapping sizes accommodate a wider range of sizes but have disadvantages. A smaller paddler wearing an overlapped size vest (such as 42-54) may not be able to adjust the straps well enough to prevent it riding up the torso. In addition, the excess length of the straps after adjustment may present a snagging risk. Universal sized, because of a wider range of sizes, may be even harder to fit with paddlers in the low end of a sizing range. When a larger size wearer adjusts the straps to the maximum size side panel (rib area) torso protection may then be lacking.

SAFETY CONSIDERATIONS
A rescue vest is a multi-purpose rescue tool that has limitations and requires training and consistent practice. Intricate knowledge of the workings of a rescue vest can make the difference between a successful rescue and a possible accident or injury.

--The Quick Release Harness System (QRHS) consists of several components: a tri-glide stainless steel buckle, a black cam buckle, and a red toggle with cord attached for releasing the harness belt system. A steel 'O' ring in back allows rescuers to be connected to a rescue line. For some models the harness belt is sewn in, on others it can be removed and used as a type II PFD without the harness belt.

--An auxiliary self-tether (also called cow tail, pig tail, or swiftwater tow tether), allows rescuer to self-connect to a rescue line. It must be safely stowed to prevent entanglement when not in use because tethers that hang excessively create a snagging potential. One or two models have a side pouch for safely stowing the tether when not used.

--A harness belt passing through the tri-glide buckle may jam/stick because the rescuer did not pull the toggle straight out on release (perpendicular to belt); because of too much excess belt tail, or because the end was not left flat when the belt was shortened.

--Manufacturers recommend that 25 lbs of force is needed to make the harness system release reliably under a load. With less force the belt releases either slowly or not at all. Rescuers must be practiced in inserting the thumbs into the cam buckle/tri-glide assembly to purposely make the belt release if needed.
*refer to the section on QRHS and testing the release point with commercial scales.

 --A locking carabiner should be used when attaching a rescue line to the 'O" ring, or to the self-tether. A non'locking carabiner might inadvertently clilp into some other part of the rescue vest, thereby nullifying the ability for the rescuer to release from the rescue line. In swiftwater rescue classes pre-determined signals are established to pendulum a rescuer to shore in case of emergency.

--A locking carabiner can be used in place of a lost 'O' ring, or else a rescue line can be tied directly into the 'O' ring with an appropriate secure knot (if not using a carabiner).

To insure a light load releasing properly (like towing an upright empty kayak), one choice is to pass the harness belt through just one of the slots in the tri-glide and then through the cam buckle, or just through the cam buckle only. ALWAYS be certain to thread the QRHS as the manufacturer requires when executing tethered lowers or 'live bait' techniques with a rescuer on the line.

BODY AND TORSO IMPACT PROTECTION
Many personal injuries that occur in both live rescues and rescue workshops are caused by tripping and falling along the riverbank. For protection against impact a vest should have sufficient cushioning in the upper and lower torso and in the sidej panels. Some companies are now including side impact panels to protect the rib area of the torso, which also adds additional flotation.

 Upper torso cushioning is a main drawback of low profile style vests. Most all current models also lack impact protection in the clavicle or shoulder area because of the necessity for freedom of movement when paddling. One brand had wider padded shoulder straps that provided some protection to this area. More study is needed to determine ways to have this protection without compromising paddling freedom or swimming movements.

DAY AND NIGHT VISIBILITY
Although manufacturers use a variety of colors for rescue vests we believe the brighter colors (red, yellow, orange and mango) provide better contrast in daytime functions. Some lighter green and blue colors as well as black, blend too much with the color of the river water and are not as visible. Rescuers should be clearly visible to to one another when working on rescue functions especially in dim light. Most vests include reflective tape/piping on both the front and back panels for night visibility and a few provide excellent night visibility. Some lack any reflective tape over the shoulders.

ATTACHMENT CAPABILITY AND STORAGE POCKETS
Maintaining a streamlined profile is important when carrying items in pockets or attaching things to the outside of the vest. Protruding items present a snagging risk to a swimmer or rescuer working in the water.
--Pocket or storage space should be adquate for such rescue items as carabiners, prusick loops, webbing (rescue sling), fire starter, CPR pocket mask or other items. Pockets must close securely, drain well, not collect water and should be easily accessible. Some of the current low profile models have only a center pocket and when full it could protrude quite a bit, which might impede swimming progress or self-rescuing over a strainer.
--Some models have carrying capacity in the back panel for a rope or other rescue items that leave the hands free for swimming. Other brands allow the attachment of additional pockets to increase storage space or for adding water bladders.
--At the conclusion of the PFD review we suggested having attachment points for knife, whistle, etc., that have breakaway capability to lessen the snagging potential.

QUICK RELEASE HARNESS SYSTEM (QRHS)
One important function of a rescue vest is for tethered rescuer lowers in strong river current, a technique that substantially increases risk to rescuers. Because rescuers can withstand only so much pressure acting on the body, the force of the current (class of rapids) becomes a limiting factor in deciding to employ a tethered rescue technique.

More than twenty years ago, Raymond Row and Graham Wardle of the British Canoe Union published a small booklet discussing the positioning of the harness belt and 'O' ring on the back of the vest. They stated, "that the point of attachment (of the rescue line to the 'O' ring) be in exactly the correct spot, that is, about mid-point between the shoulder blades." This point of attachment was intended to float the rescue swimmer almost horizontally in a 'planing' posture when performing rescue lowers (with the feet close to the surface and the head remaining above water). When performing tethered lowers rescuers can lessen the force of the water pressure on the body by arching the back during the lower, allowing the water flow to pass more underneath the body.

Information about the 'O' ring attachmentj point is virtually unchanged in recent years. Booklets published by some manufacturers have similar statements to the Row/Wardle booklet--"the attachment point for the rescue line is positioned to hold the rescuer's head above water, and the harness should be across the chest position." Slim Ray's Swiftwater Rescue Handbook also explains--"the attachment point should be positioned to hold the head above water in swift current (normally...between the shoulder blades)".

Older models some of us had experience with (these were made by Extrasport and Stohlquist) did locate the attachment point up close between the shoulder blades with the harness belt crossing mid-stermun. These were higher cut styles with smaller armholes that fit higher up on the torso. During the tethered rescuer of the recent field reviews, we noted significant differences in the attachment point and position of the harness belt on the various vests. One short waist, high cut brand that was especially stressful to rescuers on lowers, angled the harness belt upward from the front torso to the back attachment point. This vest also lacked any side torso cushioning. We plan to conduct river trials and specifically compare different style vests relative to how the 'O' ring and harness belt are located, and which are the most comfortable when performing lowers.

Testing with a set of commerical scales revealed a range in the amount of the force necessary to make the harness system release under a load. Results varied from 12 lbs to 48 lbs on all vests tested. Any harness belt should release consistently and easily. Friction depends on several factors; the number of loops the belt feeds through, the position of the belt across the front torso, and excess tail of the belt end. Through practice a rescuer swill learn exactly what to expect from the harness system on a rescue vest. It is a good idea to frequently check the harness felt for fraying edges.

SUMMARY
As with boat designs, trends and styles in rescue vests continue to evolve. Whitewater boaters desire and need a vest that strokes a balance between sufficient buoyancy for self-rescuing in turbulent water, freedom of movement for paddling comfort, and performance capability for rescue functions. As we have said throughout this report we feel there are compelling reasons for rescue vests to have more flotation and added cushioning for torso and side protection.

 Some short waist, higher cut models have 22--26.5 lbs of buoyancy that provide excellent flotation, but are somewhat cumbersome and bulky for whitewater kayaking (as reported in our field reviews). Certian low profile designs are very comfortable, provide exxcellent freedom of padlding movement, have good rescue design ideas, but need for buoyancy for swimming in heavier turbulent current.

As research and experience continue to provide answers to questions, hopefully manufacturers will be able to supply rescue vests with a suitable combination of buoyancy with safety and rescue features. The perfect vest, like the perfect boat, may never be made but they continue to improve.

We encourage boaters to participate in swiftwater rescue training and become familiar with the strengths and limitations of rescue vests. They are a valuable rescue option but require consistent practice to realize their performance capabilities.

 December, 2005--Jim Simmons. Other instructors/paddlers who assisted in compiling this report were Vernon Seaman, Jim Jones, Don Harwood, and Tim Jones.

 

 

 

 

 

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