Occurrence, Risk Factors, Prognosis and Prevention of Swimming-Induced Pulmonary Oedema: a Systematic Review

Background: Swimming-induced pulmonary oedema (SIPE) can affect people with no underlying health problems,but may be life threatening and is poorly understood. The aim of this systematic review was to synthesise the evidence on SIPE incidence, prevalence, risk factors, short- and long-term outcomes, recurrence and effectiveness of interventions to prevent recurrences. Methods: We carried out a literature search using bibliographic databases and reference lists. Risk of bias was assessed by adapting existing quality assessment tools including those developed by the National Heart Lung and Blood Institute. Results: Nine studies met the inclusion criteria. Quantitative synthesis was not possible because of study heterogeneity. Five studies, which differed from each other in case definition, swimming environment, population characteristics and denominators, reported an incidence of 0.01% of UK triathlons raced over 5 years in unspecified swimming environments(one study, not fully reported, of men and women of unspecified age); 0.5% of river races swum over 3 days in Sweden(one study,of men and women up to the age of 70);and 1.8–26.7% of time trials in the sea around Israel (three studies of male teenage military trainees). One study reported that 1.4% of triathletes in the USA had experienced SIPE. One study found that hypertension, female sex, fish oil use, long course distance and another lower initial lung volumes and flows were risk factors for SIPE. A third study reported that higher mean pulmonary artery pressures and pulmonary artery wedge pressures, and lower tidal volumes were associated with SIPE. Three studies suggested that SIPE symptoms usually resolve within 24 h, although a restrictive deficit in lung function persisted for a week in one small study. We found no studies that reported deaths from SIPE. The single small study of longer-term outcomes reported no difference between affected and unaffected swimmers. Two studies suggested that around 30% of people report recurrences of SIPE. Two very small uncontrolled studies of the effect of sildenafil for recurrence prevention were inconclusive. Conclusions: SIPE may be an important public health problem affecting the growing number of recreational open water swimmers. Further research should clarify the frequency of SIPE among recreational open water swimmers, confirm reported risk factors and explore others, explore long-term consequences and test interventions to prevent recurrence

Development and association of new metrics of dose and image quality for comparing and optimizing protocols in CT imaging

International audienceIntroduction. Nowadays, though Computed Tomography (CT) examinations only correspond to a small portion of medical imaging procedures (typically 10 % in France in 2012), they are credited with about 70 % of the total imaging collective dose. Reducing the dose due to CT examinations is therefore a major issue worldwide but cannot be achieved at the expense of the image quality (IQ) needed to ensure a correct diagnosis.Therefore, CT imaging needs to be described simultaneously using reliable metrics for delivered dose and IQ. However, such metrics are still lacking, especially for IQ. In this study, we developed and combined new metrics of IQ and patient dose in order to compare CT protocols.Methods. For IQ evaluation, the mathematical model observer (MO) Non Pre-Whitening Eyefilter (Burgess, 1994) was implemented to estimate a detectability index linked to clinical tasks such as lesion detection or discrimination. The index was calculated on CT images of a home-made dedicated phantom acquired for various irradiation and reconstruction conditions. It was then validated in the framework of a clinical study involving a dozen of experienced radiologists, on the large set on images presented in two Alternative Forced Choice (2-AFC) experiments for both tasks. After rescaling on their responses, the MO provided a Percentage of Correct answers (PC) depending on the acquisition parameters, the task and the insert size.For dose estimation, a complete Monte Carlo model of the GE Discovery CT750 HD scanner was developed with the PENELOPE code. All the components of the scanner were estimated by physical measurements. The modelling was validated with measurements in CTDI and anthropomorphic phantoms using ion chambers and Optically Stimulated Luminescence dosimeters. Once validated, dose levels were calculated in the home-made torso-shaped phantom for every acquisition parameter used in the clinical study. Curves linking PC values calculated by the MO with the simulated dose in the phantom were then built for both detection and discrimination tasks. They thus enabled to represent the influence of irradiation or reconstruction parameters, such as voltage or reconstruction slice thickness.Results. Values from several CT scanner standard abdominal protocols were placed on the curves after logarithmic regression and compared from the double point of view of dose and IQ. We could then deduce the better protocols in terms of reduced dose while keeping a close PC value. We showed for instance that, according to the clinical task, the patient dose could be reduced by a factor of two keeping a similar probability of correct answers by using a dual-energy protocol with adapted parameters.Conclusions. This method paves the way for a standardized methodology enabling clinical physicists and radiologists to optimize protocols for defined clinical tasks while keeping the dose as low as possible