2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
THE UK NATIONAL IMMERSION INCIDENT SURVEY: UPDATED
Elizabeth McCormack, Howard Oakley 1 , Peter Tikuisis 2 , David Salt 3 , Michael Tipton
Department of Sport & Exercise Science, Institute of Biomedical & Biomolecular Sciences,
University of Portsmouth, UK.
1 Institute of Naval Medicine, Gosport, Hants, UK.
2 DRDC, Toronto, Canada.
3 Department of Mathematics, University of Portsmouth, UK.
Contact person: elizabeth.mccormack@port.ac.uk
INTRODUCTION
The UK National Immersion Incident Survey (UKNIIS) was launched in 1991. It is a survey
designed for completion by the UK Coastguard when a person is rescued from accidental
immersion in water. The survey was initiated in part to help predict survival times in water,
and thereby assist the Coastguard in determining when a search should be terminated. In
1997 a report was produced by Oakley and Pethybridge on the statistical analysis of a dataset
containing information on 930 cases. A logistic regression of the odds ratio of death was
fitted to the data, and comprised the independent variables: duration of immersion, water
temperature and buoyancy device.
The survey has continued to be completed, with an additional 600 cases reported since 1997.
This paper provides a summary of the results of a re-analysis of the combined data set. A
comparison between the original and the newer, larger data set has been undertaken to check
the consistency of the reporting of information.
METHODS
The survey was undertaken to gather information on duration of immersion, condition of the
water and characteristics of the victim. The cases of victims found dead days after the initial
immersion have been excluded as they provide no assistance in predicting survival time. The
Defence Services Lifesaving (DSL) Committee approved the questionnaire and it was
distributed to HM Coastguard, the RNLI, and other members of the DSL Committee, and in
order to ensure consistency of the reported information, guidance notes were provided. They
were sent out with the request for the completed questionnaires to be returned to the Institute
of Naval Medicine, UK.
The new data (comprising of an extra 663 cases) were combined with the original data and
recorded on a single spreadsheet. An advanced system of coding was developed to clarify the
analysis. A number of different statistical analyses were performed. These included logistic
regression, as this was the method of choice used in the original report by Oakley &
Pethybridge (1997). Other analyses performed included classification and regression trees
and factor analysis.
RESULTS
The re-analyses of the UKNIIS data is ongoing and this paper contains the preliminary
findings.
The total data set of 1593 cases includes information on 160 deaths (Tables 1 and 2). The
standard of questionnaire completion was very good, with little missing critical data.
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