VCPD could be employed for pain prediction in
laboring women as VCPD correlated much more strongly with pain compared to PD
as rated with the NRS.
The sympathetic and parasympathetic systems lead to permanent pupillary
fluctuations. These fluctuations are different from pupillary diameter
variations (PD) that increases proportionally with pain intensity. The
pupillary fluctuations are measured using the variation coefficient of PD
(VCPD). David J.Charier et al. and his colleagues conducted a prospective study
based on finding the correlation between PD, the increase of PD during a contraction, and VCPD with pain and
then undertook a comparative analysis among such associations. The pain was
rated using a numeric rating scale (NRS) during obstetrical labor.
The study included 40 patients and 160 simultaneous ratings (NRS, PD, and
VCPD). Among these 160 concurrent scores, 40 were in the presence of uterine contractions
and 40 were in the absence of such contractions, before and 20 minutes after
epidural analgesia. The results indicated that there occurs a strong
correlation between VCPD (r = .77) and
pain rated using an NRS as compared to PD increase (r = .42). The potential of
VCPD to predict the occurrence of NRS scores ≥4 during obstetrical labor is .97
(confidence interval, .93–1.0). VCPD
correlates more strongly than PD, and it increases with pain rated using the NRS
when measured over 10 seconds during contraction. This stronger correlation
enables to assess antinociception-nociception balance easily.
It is concluded that VCPD allows for an objective assessment of pain in
laboring women. It is helpful in evaluating pain in noncommunicating patients:
newborns or very old patients, patients with acute psychological conditions,
assessment during the immediate postoperative period, or in intensive care
units.
The Journal of Pain
A new pupillary measure to assess pain: a prospective study
David J.Charier et al.
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