Invacare FDX Tilt/Elevate with Compact Vent Tray

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Every so often, I'll post something I know won't be relevant to the vast majority of members but could prove to be extremely useful to a few individuals with very specific needs. Such is the case with this Invacare FDX equipped with a Formula CG tilt/elevate system, LNX power center mount legrests, and Motion Concepts Compact Vent Tray.



The FDX is one of our "ALS powerchairs" and was prescribed a little over a year ago for someone who needed an elevating seat so he could stand to transfer or walk for short distances. Unfortunately, he needed a both ventilator and supplemental oxygen. At the time, this combination was a "show stopper" because no manufacturer offered a powerbase equipped with a tilt/elevate system, compact vent tray, and an oxygen carrier. The main technical barrier preventing this was the instability created by the weight of a vent and O2 cylinder on a power elevating seat. Our Home Oxygen program came through by providing a lighter Helios Companion liquid O2 system.

The FDX was equipped with a Richardson PowerTech Vent Center which is a 24 volt to 12 volt DC power converter that allows the LTV 1150 Compact Ventilator to be powered off of the FDX's Group 34 batteries. Much of the vent circuit fits neatly between the vent tray and the 22" Contoura back pan. To ensure the distal part of the circuit is secure and positioned in a good orientation to connect comfortably at the trach site, I used the bolt-on push handle receiver designed for the backrest rigidizer bar on an Invacare rigid frame manual wheelchair along with a couple of 1" J-hook drain pipe hangers I found in the plumbing section of my local Lowe's. They are perfectly designed for securing the corrugated vent circuit tubing with minimal risk of damage...



On previous ventilator-equipped powerchairs, the hard part had always been routing the vent circuit. While the Helios Companion Liquid Oxygen Dispenser seemed to be an easy solution, it turned out to be more of a challenge than I expected. I discovered that any liquid O2 system that compatible with an LTV vent will be positional--meaning it must be vertical at all times in order to function properly. That meant I had to come up with a way to allow the Helios to hang freely enough to stay upright while the seat was being tilted, yet stay in a secure position whenever the chair seat was upright and the powerchair was in motion. Eventually, I arrived at a system consisting of an ABS hook on the push handle to hang the strap combined with a support on the vent tray to prevent unintended movement...



Without both components, the Helios unit would swing back and forth or bump into the ventilator when the chair was moving. It took many trials of tilting the seat back and forth before I was confident it would work consistently.

At 46.5" long, the FDX is fairly compact for a powerchair equipped with a ventilator and met all the the requirements for its intended end user. The elevating seat allowed him to transfer without a lift or walk into his otherwise inaccessible bathroom. While the original end user has since passed away, this chair continues to be used today by another end user with ALS who had similar needs.

Liquid O2 systems are preferable for someone who doesn't need a vent since they are less likely to interfere with power seating functions and may last longer than standard oxygen cylinders. There are commercially available systems which will allow a liquid O2 system to articulate.

Knowing what I know now about liquid O2 systems, however, I wouldn't combine one with a ventilator in the future. I would opt for a traditional oxygen cylinder used in conjunction with a compact vent tray. This combination is possible on an FDX with a Formula CG tilt only system. Specifying a medium or high STF height (17.5 or 18.5") could be a cost-effective alternative to the power elevating seat. Permobil also developed this type of system for their Corpus 3G seating system. They do offer a power elevating seat but require their Enhanced Steering Performance to be selected with their vent tray option.

Lessons learned. Knowledge shared. While most will not, I suspect a few people out there will find this information to be helpful.