Limb edema had a significant negative influence on the generation
of a muscle contraction, with the inability to obtain a type 3, 4, or 5
contraction if a level 4 edema is present. Harper et al [37] observed
that, in ICU patients with limb edema, a higher intensity was needed
to obtain the same contraction. However, this high intensity is often
impossible to achieve due to the sensory discomfort [38]. In addition,
edema contributed to an increased distance between electrodes and
muscle [20], which in turn might reduce current density and impair
muscle contraction. Therefore, palpation was used in addition to the
visual inspection to minimize this type of bias.
Analysis showed that 22% of the patients with a good response
(type 4 or 5) in session 1 did not respond well (type 1-3) anymore in
session 5. This can be attributed to a change in parameters such as
development of edema or sepsis in the first days on the ICU. Because
this was not investigated in this study, this can only be assumed and
should be investigated in critically ill patients to make solid
conclusions on this result.