Management of Mild or Marginal Decompression Illness in Remote ...

Data Cleaning in DIRF 2001 "Doubt, No Doubt" and DIRF 1998-2002
The problems outlined above are familiar to any analyst of retrospective data, and the
best solution is to study the issue prospectively with a predetermined series of questions
using a well thought out experimental design. Even when the questions were not
thought out in advance, contacting the subject and interviewing him a second time can
often obtain critical data. This technique was used to in two instances described previously
to re-study latency in cases of paralysis (DARF 1990-1997) and motor weakness
(DIRF 1998-2002). The DIRF 1998-2002 was also examined for the effect of treatment
delay on mild cases.
When repeating an interview is not possible, analytical problems can be confronted retrospectively
by applying filters to the dataset that categorize the cases by severity and
earmark the diagnostically ambiguous ones. This technique was used in the DIRF 2001
"Doubt, no doubt" dataset. Although this process can introduce bias through the filter
design, if the criteria are clearly defined, consistently adhered to and appropriately
applied, then the analysis will be meaningful. A more detailed discussion of the analysis
of effect of delay to treatment in mild cases in these data sets follows.
Effect of Delay to Recompression Treatment on the DIRF 2001 "Doubt, No Doubt" Data
The "Doubt, no doubt" data set was an attempt to retrospectively deal with the question
of diagnostic ambiguity. For the DCI diagnosis symposium held at Duke
University in April 2003, DAN developed a series of criteria to sort DCI cases in the
injury databases by severity and diagnostic confidence.
The best data available were the 522 cases collected using the DIRF during the calendar
year 2001 (20). All cases had received recompression; therefore, the response to treatment
was known. Because the DIRF has a field that allows the reporting physician to
list his final diagnosis, the opinion of the reporting physician was used as the primary
screen for diagnostic confidence. All cases still listed as DCS, AGE or DCI by the
reporting physician were classified as no doubt. Cases listed as "ambiguous," "lung
barotrauma without AGE," "other," or "unrelated to pressure" were classified as doubtful
(doubt).
Dr. Petar Denoble of DAN Research applied additional filtering to the dataset. He
reclassified the remaining no doubt cases during a detailed chart review by reclassifying
as doubtful cases that did not have the following criteria:
• For AGE, symptom onset greater than 15 minutes post dive, cases without at least
one cerebral symptom, and cases with symptom duration of less than 15 minutes.
• For DCS, single dives to less than 30 fsw, symptom onset more than 48 hours after the
dive unless there was an intervening altitude exposure, and symptoms that persisted
less than 20 minutes with O2 or less than 60 minutes without O2.
To better understand severity at the time of presentation, the cases were hierarchically
categorized into the following bins according to the most severe symptoms: (1) motor
weakness or paralysis; (2) mental status changes or involvement of coordination or the
Management of Mild or Marginal Decompression Illness in Remote Locations Workshop Proceedings
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