CGA FAQ: Physiological Cost Index
Dear CGA members

I was wondering which labs out there are measuring Physiological
Cost Index (PCI) using heart rate monitors in CP asessment. In
particular which protocols are being used in terms of distance of
circuit, type of circuit, number of circuits walked etc.

Please can you copy replies to my personal email address as well as
to CGA because my receipt of postings from cga appears unreliable.

Thanks in advance.

Jeremy Linskell
Manager, Gait Analysis Laboratory
Co-Ordinator, Electronic Assistive Tehcnology Service
Dundee Limb Fitting Centre
Dundee, DD5 1AG, Scotland
tel +1382-730104, fax +1382-480194

 Dear Jeremy and CGA readers,

First the technical points:
I use a POLAR Vantage NV heart rate monitor (beat-to-beat HR) and the
POLAR Advantage Interface to measure heart rate. I have both types of
transmitters. The new one is too rigid for small children and I always
lost contact so I bought the old type sensor which I stick on the chest
(aligned with the electrical axis of the heart) with two EMG electrodes.
I always ask the parents if the child has ever had any heart problems,
because potentially a pacemaker can use similar signals to that of the
HR monitor. In such case I would not do PCI. (I also checked how strong
the signal is and what the effective range is, because our gait lab sits
in the middle of cardiology.)

I test PCI at the end of the gait analysis session. I explain and
demonstrate the child the exercise because I found that the resting HR's
were higher if they didn't know what to expect. I give the child at
least 5 minutes rest before measuring the resting heart rate. (I use
that time to check the kinematics, kinetics and EMG.) I also double
check the resting heart rate after the test. I have a 6 m long walkway
marked on the carpet and I get them to walk at constant speed around in
"circles" by walking up on the left side (of a 2 m wide carpet), turning
around an obstacle and coming back on the right side. They walk for
about a minute so that they reach a steady state HR and then I measure
usually 6 lengths (36 m) but that depends on how well the child can
walk. I measure the time taken with a stopwatch. I upload the data to a
PC through the interface and take the average of the HR during the 36 m
walk (after the 1 minute mark). A small program works out the PCI. The
same is repeated with AFO's/walkers.

The limitations are that they don't walk in proper circles and so the
walking speed is not constant, and their resting heart rate is affected
by being nervous. Sometimes parents can be a problem joking with them
etc. which may also have an effect on HR. They may be tired towards the
end of a gait analysis, but at the beginning they would be nervous. I
don't let them drink Coke, tea before the PCI test (coffein,

My sources for the protocol are various, mostly based on the literature
(I can dig out some refs) and advice from others, spiced with

Dr Gabor Barton MD         
Manager, Gait Analysis Laboratory    UIN (ICQ): 2625928
Alder Hey Children's Hospital        tel: +44 (0)151 252 5949
Eaton Road, Liverpool, L12 2AP, UK   fax: +44 (0)151 252 5846

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