Compression stockings for preventing deep vein thrombosis in airline passengers

Compression stockings for preventing deep vein thrombosis in airline passengers

BACKGROUND

Air travel might increase the risk of deep vein thrombosis (DVT). It has been suggested that wearing compression stockings might reduce this risk. This is an update of the review first published in 2006.

OBJECTIVES

To assess the effects of wearing compression stockings versus not wearing them for preventing DVT in people travelling on flights lasting at least four hours.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase, CINAHL and AMED databases and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 1 April 2020. We also checked the bibliographies of relevant studies and reviews identified by the search to check for any additional trials.

SELECTION CRITERIA

Randomised trials of compression stockings versus no stockings in passengers on flights lasting at least four hours. Trials in which passengers wore a stocking on one leg but not the other, or those comparing stockings and another intervention were also eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion and extracted data. We sought additional information from trialists where necessary.

MAIN RESULTS

One new study that fulfilled the inclusion criteria was identified for this update. Twelve randomised trials (n = 2918) were included in this review: ten (n = 2833) compared wearing graduated compression stockings on both legs versus not wearing them; one trial (n = 50) compared wearing graduated compression tights versus not wearing them; and one trial (n = 35) compared wearing a graduated compression stocking on one leg for the outbound flight and on the other leg on the return flight. Eight trials included people judged to be at low or medium risk of developing DVT (n = 1598) and two included high-risk participants (n = 1273). All flights had a duration of more than five hours. Fifty of 2637 participants with follow-up data available in the trials of wearing compression stockings on both legs had a symptomless DVT; three wore stockings, 47 did not (odds ratio (OR) 0.10, 95% confidence interval (CI) 0.04 to 0.25, P < 0.001; high-certainty evidence). There were no symptomless DVTs in three trials. Sixteen of 1804 people developed superficial vein thrombosis, four wore stockings, 12 did not (OR 0.45, 95% CI 0.18 to 1.13, P = 0.09; moderate-certainty evidence). No deaths, pulmonary emboli or symptomatic DVTs were reported. Wearing stockings had a significant impact in reducing oedema (mean difference (MD) -4.72, 95% CI -4.91 to -4.52; based on six trials; low-certainty evidence). A further three trials showed reduced oedema in the stockings group but could not be included in the meta-analysis as they used different methods to measure oedema. No significant adverse effects were reported.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that airline passengers similar to those in this review can expect a substantial reduction in the incidence of symptomless DVT and low-certainty evidence that leg oedema is reduced if they wear compression stockings. The certainty of the evidence was limited by the way that oedema was measured. There is moderate-certainty evidence that superficial vein thrombosis may be reduced if passengers wear compression stockings. We cannot assess the effect of wearing stockings on death, pulmonary embolism or symptomatic DVT because no such events occurred in these trials. Randomised trials to assess these outcomes would need to include a very large number of people.

Indications for medical compression stockings in venous and lymphatic disorders: An evidence-based consensus statement

Objective Medical compression stockings are a standard, non-invasive treatment option for all venous and lymphatic diseases. The aim of this consensus document is to provide up-to-date recommendations and evidence grading on the indications for treatment, based on evidence accumulated during the past decade, under the auspices of the International Compression Club. Methods A systematic literature review was conducted and, using PRISMA guidelines, 51 relevant publications were selected for an evidence-based analysis of an initial 2407 unrefined results. Key search terms included: 'acute', CEAP', 'chronic', 'compression stockings', 'compression therapy', 'lymph', 'lymphatic disease', 'vein' and 'venous disease'. Evidence extracted from the publications was graded initially by the panel members individually and then refined at the consensus meeting. Results Based on the current evidence, 25 recommendations for chronic and acute venous disorders were made. Of these, 24 recommendations were graded as: Grade 1A (n = 4), 1B (n = 13), 1C (n = 2), 2B (n = 4) and 2C (n = 1). The panel members found moderately robust evidence for medical compression stockings in patients with venous symptoms and prevention and treatment of venous oedema. Robust evidence was found for prevention and treatment of venous leg ulcers. Recommendations for stocking-use after great saphenous vein interventions were limited to the first post-interventional week. No randomised clinical trials are available that document a prophylactic effect of medical compression stockings on the progression of chronic venous disease (CVD). In acute deep vein thrombosis, immediate compression is recommended to reduce pain and swelling. Despite conflicting results from a recent study to prevent post-thrombotic syndrome, medical compression stockings are still recommended. In thromboprophylaxis, the role of stockings in addition to anticoagulation is limited. For the maintenance phase of lymphoedema management, compression stockings are the most important intervention. Conclusion The beneficial value of applying compression stockings in the treatment of venous and lymphatic disease is supported by this document, with 19/25 recommendations rated as Grade 1 evidence. For recommendations rated with Grade 2 level of evidence, further studies are needed.

Economy class syndrome: what is it and who are the individuals at risk?

The term ‘economy class syndrome’ refers to the occurrence of thrombotic events during long-haul flights that mainly occur in passengers in the economy class of the aircraft. This syndrome results from several factors related to the aircraft cabin (immobilization, hypobaric hypoxia and low humidity) and the passenger (body mass index, thrombophilia, oral contraceptives or hormone replacement therapy, cancer), acting together to predispose to excessive blood coagulation, which can result in venous thromboembolism. Several risk factors, both genetic and acquired, are associated with venous thromboembolism. The most important genetic risk factors are natural anticoagulant deficiencies (antithrombin, protein C and protein S), factor V Leiden, prothrombin and fibrinogen gene mutations and non-O blood group individuals. Acquired risk factors include age, pregnancy, surgery, obesity, cancer, hormonal contraceptives and hormone replacement therapy, antiphospholipid syndrome, infections, immobilization and smoking. People who have these risk factors are predisposed to hypercoagulability and are more susceptible to suffer venous thromboembolism during air travel. For these individuals, a suitable outfit for the trip, frequent walks, calf muscle exercises, elastic compression stockings and hydration are important preventive measures. Hence, it is essential to inform about economic class syndrome in an attempt to encourage Brazilian health and transport authorities to adopt measures, in partnership with the pharmaceutical industry, to prevent venous thromboembolism.

The Saudi clinical practice guideline for the prophylaxis of venous thromboembolism in long-distance travelers

Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is a preventable disease. Long distant travelers are prone to variable degree to develop VTE. However, the low risk of developing VTE among long-distance travelers and which travelers should receive VTE prophylaxis, and what prophylactic measures should be used led us to develop these guidelines. These clinical practice guidelines are the result of an initiative of the Ministry of Health of the Kingdom of Saudi Arabia involving an expert panel led by the Saudi Association for Venous Thrombo Embolism (a subsidiary of the Saudi Thoracic Society). The McMaster University Guideline working group provided the methodological support. The expert panel identified 5 common questions related to the thromboprophylaxis in long-distance travelers. The corresponding recommendations were made following the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach.

Compression stockings for preventing deep vein thrombosis in airline passengers

BACKGROUND

Air travel might increase the risk of deep vein thrombosis (DVT). It has been suggested that wearing compression stockings might reduce this risk. This is an update of the review first published in 2006.

OBJECTIVES

To assess the effects of wearing compression stockings versus not wearing them for preventing DVT in people travelling on flights lasting at least four hours.

SEARCH METHODS

For this update the Cochrane Vascular Information Specialist (CIS) searched the Specialised Register (10 February 2016). In addition, the CIS searched the Cochrane Register of Studies (CENTRAL (2016, Issue 1)).

SELECTION CRITERIA

Randomised trials of compression stockings versus no stockings in passengers on flights lasting at least four hours. Trials in which passengers wore a stocking on one leg but not the other, or those comparing stockings and another intervention were also eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion and extracted data. We sought additional information from trialists where necessary.

MAIN RESULTS

One new study that fulfilled the inclusion criteria was identified for this update. Eleven randomised trials (n = 2906) were included in this review: nine (n = 2821) compared wearing graduated compression stockings on both legs versus not wearing them; one trial (n = 50) compared wearing graduated compression tights versus not wearing them; and one trial (n = 35) compared wearing a graduated compression stocking on one leg for the outbound flight and on the other leg on the return flight. Eight trials included people judged to be at low or medium risk of developing DVT (n = 1598) and two included high-risk participants (n = 1273). All flights had a duration of more than five hours.Fifty of 2637 participants with follow-up data available in the trials of wearing compression stockings on both legs had a symptomless DVT; three wore stockings, 47 did not (odds ratio (OR) 0.10, 95% confidence interval (CI) 0.04 to 0.25, P < 0.001; high-quality evidence). There were no symptomless DVTs in three trials. Sixteen of 1804 people developed superficial vein thrombosis, four wore stockings, 12 did not (OR 0.45, 95% CI 0.18 to 1.13, P = 0.09; moderate-quality evidence). No deaths, pulmonary emboli or symptomatic DVTs were reported. Wearing stockings had a significant impact in reducing oedema (mean difference (MD) -4.72, 95% CI -4.91 to -4.52; based on six trials; low-quality evidence). A further two trials showed reduced oedema in the stockings group but could not be included in the meta-analysis as they used different methods to measure oedema. No significant adverse effects were reported.

AUTHORS' CONCLUSIONS

There is high-quality evidence that airline passengers similar to those in this review can expect a substantial reduction in the incidence of symptomless DVT and low-quality evidence that leg oedema is reduced if they wear compression stockings. Quality was limited by the way that oedema was measured. There is moderate-quality evidence that superficial vein thrombosis may be reduced if passengers wear compression stockings. We cannot assess the effect of wearing stockings on death, pulmonary embolism or symptomatic DVT because no such events occurred in these trials. Randomised trials to assess these outcomes would need to include a very large number of people.

Risk of symptomatic venous thromboembolism associated with flying in the early postoperative period following elective total hip and knee arthroplasty

Air travel and total joint arthroplasty (TJA) are both risk factors for venous thromboembolism (VTE). Patients are counseled against flying after surgery, however the basis for this recommendation has not been investigated and may be unfounded. A retrospective cohort of 1465 consecutive TJA patients was divided into a study population of 220 patients (15.0%) who flew home at a mean of 2.9 days after surgery (range, 1-10 days) and a control population of 1245 patients (85.0%) who did not fly. We found no differences in the rate of deep vein thrombosis, pulmonary embolism, or overall VTE between the groups, and incidence of all events was low in both groups and comparable with published data. Allowing air travel after TJA appears to be a safe practice.

Compression stockings for the initial treatment of varicose veins in patients without venous ulceration

BACKGROUND

Compression hosiery or stockings are often the first line of treatment for varicose veins in people without either healed or active venous ulceration. Evidence is required to determine whether the use of compression stockings can effectively manage and treat varicose veins in the early stages. This is an update of a review first published in 2011.

OBJECTIVES

To assess the effectiveness of compression stockings for the only and initial treatment of varicose veins in patients without healed or active venous ulceration.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched August 2013) and CENTRAL (2013, Issue 5).

SELECTION CRITERIA

Randomised controlled trials (RCTs) were included if they involved participants diagnosed with primary trunk varicose veins without healed or active venous ulceration (Clinical, Etiology, Anatomy, Pathophysiology (CEAP) classification C2 to C4). Included trials assessed compression stockings versus no treatment, compression versus placebo stockings, or compression stockings plus drug intervention versus drug intervention alone. Trials comparing different lengths and pressures of stockings were also included. Trials involving other types of treatment for varicose veins (either as a comparator to stockings or as an initial non-randomised treatment), including sclerotherapy and surgery, were excluded.

DATA COLLECTION AND ANALYSIS

Two authors assessed the trials for inclusion and quality (SS and LR). SS extracted the data, which were checked by LR. Attempts were made to contact trial authors where missing or unclear data were present.

MAIN RESULTS

Seven studies involving 356 participants with varicose veins without healed or active venous ulceration were included. Different levels of pressure were exerted by the stockings in the studies, ranging from 10 to 50 mmHg. One study assessed compression hosiery versus no compression hosiery. The other six compared different types or pressures of stockings. The methodological quality of all included trials was unclear, mainly because of inadequate reporting.The symptoms subjectively improved with the wearing of stockings across trials that assessed this outcome, but these assessments were not made by comparing one randomised arm of a trial with a control arm and are therefore subject to bias.Meta-analyses were not undertaken due to inadequate reporting and actual or suspected high levels of heterogeneity.

AUTHORS' CONCLUSIONS

There is insufficient, high quality evidence to determine whether or not compression stockings are effective as the sole and initial treatment of varicose veins in people without healed or active venous ulceration, or whether any type of stocking is superior to any other type. Future research should consist of a large RCT of participants with trunk varices either wearing or not wearing compression stockings to assess the efficacy of this intervention. If compression stockings are found to be beneficial, further studies assessing which length and pressure is the most efficacious could then take place.

Assessing and presenting summaries of evidence in Cochrane Reviews

Cochrane Reviews are intended to help providers, practitioners and patients make informed decisions about health care. The goal of the Cochrane Applicability and Recommendation Methods Group (ARMG) is to develop approaches, strategies and guidance that facilitate the uptake of information from Cochrane Reviews and their use by a wide audience with specific focus on developers of recommendations and on healthcare decision makers. This paper is part of a series highlighting developments in systematic review methodology in the 20 years since the establishment of The Cochrane Collaboration, and its aim is to present current work and highlight future developments in assessing and presenting summaries of evidence, with special focus on Summary of Findings (SoF) tables and Plain Language Summaries.A SoF table provides a concise and transparent summary of the key findings of a review in a tabular format. Several studies have shown that SoF tables improve accessibility and understanding of Cochrane Reviews.The ARMG and GRADE Working Group are working on further development of the SoF tables, for example by evaluating the degree of acceptable flexibility beyond standard presentation of SoF tables, developing SoF tables for diagnostic test accuracy reviews and interactive SoF tables (iSoF).The plain language summary (PLS) is the other main building block for dissemination of review results to end-users. The PLS aims to summarize the results of a review in such a way that health care consumers can readily understand them. Current efforts include the development of a standardized language to describe statistical results, based on effect size and quality of supporting evidence.Producing high quality PLS and SoF tables and making them compatible and linked would make it easier to produce dissemination products targeting different audiences (for example, providers, health policy makers, guideline developers).Current issues of debate include optimal presentation formats of SoF tables, the training required to produce SoF tables, and the extent to which the authors of Cochrane Reviews should provide explicit guidance to target audiences of patients, clinicians and policy-makers.

Knee length versus thigh length graduated compression stockings for prevention of deep vein thrombosis in postoperative surgical patients

BACKGROUND

Graduated compression stockings (GCS) are a valuable means of thromboprophylaxis in hospitalised postoperative surgical patients. But it is still unclear whether knee length graduated compression stockings (KL) or thigh length (TL) stockings are more effective.

OBJECTIVES

The aim of this review was to systematically analyse the randomised, controlled trials that have evaluated the effectiveness of KL versus TL GCS as a thromboprophylaxis tool in hospitalised patients undergoing various types of surgery.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched February 2012) and CENTRAL (2012, Issue 1). The authors searched MEDLINE and EMBASE (until 27 February 2012) and they also searched the reference lists of relevant articles to identify additional trials.

SELECTION CRITERIA

Randomised controlled trials published in any language on KL versus TL GCS used as a thromboprophylaxis tool in hospitalised patients of any age and either gender.

DATA COLLECTION AND ANALYSIS

Data extraction was undertaken independently by two review authors using data extraction sheets and confirmed by the third review author.

MAIN RESULTS

Three studies, with a combined total of 496 patients, matched the inclusion criteria for this review. All three included studies evaluated the role of KL and TL in thromboprophylaxis among a group of postoperative patients. These studies showed no significant difference in the ability of the two modalities of leg compression to reduce the incidence of deep vein thrombosis in postoperative patients. In both the fixed-effect model (odds ratio (OR) 1.55, 95% confidence interval (CI) 0.78 to 3.07, P = 0.21) and random-effects model (OR 1.32, 95% CI 0.43 to 4.06, P = 0.63) KL graduated compression stockings were as effective as TL stockings in thromboprophylaxis. However, there was significant heterogeneity (Tau(2) = 0.50; Chi(2) = 4.12, df = 2 (P = 0.13); I(2) = 51%) among trials. Results of this review may be considered weak because there was significant heterogeneity among included trials resulting from inadequate randomisation techniques, allocation concealment, power calculations and the absence of intention-to-treat analysis.

AUTHORS' CONCLUSIONS

This review found that there is insufficient high quality evidence to determine whether or not KL and TL GCS differ in their effectiveness in terms of reducing the incidence of deep vein thrombosis (DVT) in hospitalised patients.  A major multicentre RCT is required to address this issue. In the meantime, the decision on which type of stocking to use in clinical practice is likely to be influenced by factors such as patient compliance, ease of use and cost implications.

Knee-length graduated compression stockings for thromboprophylaxis in air travellers: A meta-analysis

OBJECTIVE

To systematically review the randomized controlled trials that have evaluated the efficacy of knee-length (KL) compression stockings for thromboprophylaxis in air travellers.

METHOD

After an electronic database search, the randomized controlled trials that studied passengers on long-haul flights were selected and analyzed to generate summative data.

RESULTS

Nine trials studying participants using KL stockings were analyzed. Forty-six of 1261 participants randomly assigned to the control group developed deep vein thrombosis (DVT), compared with two of 1237 participants (0.16%) in the KL stockings group. The weighted risk difference was -0.034, which indicated that the absolute difference was 3.4% in the incidence of DVT, in favour of KL stockings. The number needed to treat with KL stockings to avoid one case of DVT was 29.4. However, there was significant heterogeneity among trials. The RR for DVT was 0.08 in high-risk participants and 0.14 in low- to medium-risk participants.

CONCLUSION

KL stockings are effective for thromboprophylaxis in air travellers at low, medium and high risk of DVT. The use of KL stockings should form an important part of air traveller education on lowering the burden of DVT. The results of the present meta-analysis can be used to advise travellers on their risk of DVT and preventive strategies.

Prevention of VTE in nonsurgical patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

This guideline addressed VTE prevention in hospitalized medical patients, outpatients with cancer, the chronically immobilized, long-distance travelers, and those with asymptomatic thrombophilia.

METHODS

This guideline follows methods described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

For acutely ill hospitalized medical patients at increased risk of thrombosis, we recommend anticoagulant thromboprophylaxis with low-molecular-weight heparin (LMWH), low-dose unfractionated heparin (LDUH) bid, LDUH tid, or fondaparinux (Grade 1B) and suggest against extending the duration of thromboprophylaxis beyond the period of patient immobilization or acute hospital stay (Grade 2B). For acutely ill hospitalized medical patients at low risk of thrombosis, we recommend against the use of pharmacologic prophylaxis or mechanical prophylaxis (Grade 1B). For acutely ill hospitalized medical patients at increased risk of thrombosis who are bleeding or are at high risk for major bleeding, we suggest mechanical thromboprophylaxis with graduated compression stockings (GCS) (Grade 2C) or intermittent pneumatic compression (IPC) (Grade 2C). For critically ill patients, we suggest using LMWH or LDUH thromboprophylaxis (Grade 2C). For critically ill patients who are bleeding or are at high risk for major bleeding, we suggest mechanical thromboprophylaxis with GCS and/or IPC at least until the bleeding risk decreases (Grade 2C). In outpatients with cancer who have no additional risk factors for VTE we suggest against routine prophylaxis with LMWH or LDUH (Grade 2B) and recommend against the prophylactic use of vitamin K antagonists (Grade 1B).

CONCLUSIONS

Decisions regarding prophylaxis in nonsurgical patients should be made after consideration of risk factors for both thrombosis and bleeding, clinical context, and patients' values and preferences.

Compression stockings for the initial treatment of varicose veins in patients without venous ulceration

BACKGROUND

Compression hosiery or stockings are often the first line of treatment for varicose veins in people without either healed or active venous ulceration. Evidence is required to determine whether the use of compression stockings can effectively manage and treat varicose veins in the early stages.

OBJECTIVES

To assess the effectiveness of compression stockings for the initial treatment of varicose veins in patients without healed or active venous ulceration.

SEARCH METHODS

The Cochrane Peripheral Vascular Disease Group searched their Specialised Register (last searched 31 May 2011) and CENTRAL (2011, Issue 2). In addition, the reference lists of relevant articles were searched. Authors of ongoing and current trials were contacted. There were no language restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) were included if they involved participants diagnosed with primary trunk varicose veins without healed or active venous ulceration (Clinical, Etiology, Anatomy, Pathophysiology (CEAP) classification C2 to C4). Included trials assessed compression stockings versus no treatment, compression versus placebo stockings, or compression stockings + drug intervention versus drug intervention alone. Trials comparing different lengths and pressures of stockings were also included. Trials involving other types of treatment for varicose veins (either as a comparator to stockings or as an initial non-randomised treatment), including sclerotherapy and surgery, were excluded.

DATA COLLECTION AND ANALYSIS

Two authors assessed the trials for inclusion and quality (SS and LR). SS extracted the data, which were checked by LR. Attempts were made to contact trial authors where missing or unclear data were present.

MAIN RESULTS

Seven studies involving 356 participants with varicose veins without healed or active venous ulceration were included. Different levels of pressure were exerted by the stockings in the studies, ranging from 10 to 50 mmHg. One study assessed compression hosiery versus no compression hosiery. The other six compared different types or pressures of stockings. The methodological quality of all included trials was unclear, mainly because of inadequate reporting.The symptoms subjectively improved with the wearing of stockings across trials that assessed this outcome, but these assessments were not made by comparing one randomised arm of a trial with a control arm and are therefore subject to bias.Meta-analyses were not undertaken due to inadequate reporting and actual or suspected high levels of heterogeneity.

AUTHORS' CONCLUSIONS

There is insufficient, high quality evidence to determine whether or not compression stockings are effective as the sole and initial treatment of varicose veins in people without healed or active venous ulceration, or whether any type of stocking is superior to any other type. Future research should consist of a large RCT of participants with trunk varices either wearing or not wearing compression stockings to assess the efficacy of this intervention. If compression stockings are found to be beneficial, further studies assessing which length and pressure is the most efficacious could then take place.

Traveller's thrombosis: airlines still not giving passengers the WRIGHT advice!

INTRODUCTION

This study has examined the impact of the World Health Organization's Research into Global Hazards of Travel (WRIGHT) Project's phase 1 report on the information given by airlines to their passengers regarding traveller's thrombosis.

METHODS

Official websites of all airlines flying from Heathrow (UK) and John F Kennedy (USA) were located through links on the websites of these two busy international airports. In June 2007, each site was scrutinized by three independent researchers to identify if traveller's thrombosis and its risk factors were discussed and what methods of prevention were advised. This exercise was repeated a year after the publication of the WRIGHT report.

RESULTS

One hundred and nineteen international airlines were listed in 2007 (12 were excluded from analysis). A quarter (27/107) of airlines warned of the risk of traveller's thrombosis. A year later, five airlines were no longer operational and there had been no increase in the discussion of traveller's thrombosis (23/102). Additional risk factors discussed in June 2007 versus September 2008: previous venous thromboembolism (16%, 15%); thrombophilia (14%, 15%); family history (11%, 9%); malignancy (12%, 14%); recent surgery (19%, 16%); pregnancy (17%, 16%) and obesity (11%, 12%). Prophylaxis advice given in June 2007 versus September 2008: in-flight exercise (34%, 42%); Hydration (30%, 34%); medical consultation prior to flying (20%, 18%); graduated compression stockings (13%, 12%); aspirin (<1%, <1%) and heparin (5%, 7%).

CONCLUSIONS

The majority of world airlines continue to fail to warn of the risk of traveller's thrombosis or offer appropriate advice. Alerting passengers at risk gives them an opportunity to seek medical advice before flying.

Effect of walking on pressure variations that occur at the interface between elastic stockings and the skin

The aim of this work was to dynamically study pressure variations exerted by elastic compression stockings during walking. While study participants walked, the pressure variations at the interface between elastic stockings and the skin were measured dynamically. Three healthy individuals wearing 10/20 and 20/30 elastic compression stockings manufactured by Sigvaris((R)) (Jundiai, São Paulo-Brazil) were requested to walk along a course for ten times at a constant speed. For every event, an apparatus specifically developed for the study and programmed to take readings at half-second intervals was used to measure the pressure exerted by the elastic stockings. The pressure exerted by the 10/20 stockings varied between 5 and 32 mmHg and for the 20/30 stockings it varied from 10 to 52 mmHg. Elastic stockings with larger pressures generate larger pressure variations during muscle activity (P-value < 0.001). In conclusion, muscle movements during walking cause the pressure exerted by elastic stockings on the leg to vary; thus, the pressure is not constant but has peaks and troughs according to the type of muscle movement and the gradient of the stockings.

The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration

Systematic reviews and meta-analyses are essential to summarize evidence relating to efficacy and safety of health care interventions accurately and reliably. The clarity and transparency of these reports, however, is not optimal. Poor reporting of systematic reviews diminishes their value to clinicians, policy makers, and other users.Since the development of the QUOROM (QUality Of Reporting Of Meta-analysis) Statement--a reporting guideline published in 1999--there have been several conceptual, methodological, and practical advances regarding the conduct and reporting of systematic reviews and meta-analyses. Also, reviews of published systematic reviews have found that key information about these studies is often poorly reported. Realizing these issues, an international group that included experienced authors and methodologists developed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) as an evolution of the original QUOROM guideline for systematic reviews and meta-analyses of evaluations of health care interventions.The PRISMA Statement consists of a 27-item checklist and a four-phase flow diagram. The checklist includes items deemed essential for transparent reporting of a systematic review. In this Explanation and Elaboration document, we explain the meaning and rationale for each checklist item. For each item, we include an example of good reporting and, where possible, references to relevant empirical studies and methodological literature. The PRISMA Statement, this document, and the associated Web site (http://www.prisma-statement.org/) should be helpful resources to improve reporting of systematic reviews and meta-analyses.

The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration

Systematic reviews and meta-analyses are essential to summarise evidence relating to efficacy and safety of healthcare interventions accurately and reliably. The clarity and transparency of these reports, however, are not optimal. Poor reporting of systematic reviews diminishes their value to clinicians, policy makers, and other users. Since the development of the QUOROM (quality of reporting of meta-analysis) statement-a reporting guideline published in 1999-there have been several conceptual, methodological, and practical advances regarding the conduct and reporting of systematic reviews and meta-analyses. Also, reviews of published systematic reviews have found that key information about these studies is often poorly reported. Realising these issues, an international group that included experienced authors and methodologists developed PRISMA (preferred reporting items for systematic reviews and meta-analyses) as an evolution of the original QUOROM guideline for systematic reviews and meta-analyses of evaluations of health care interventions. The PRISMA statement consists of a 27-item checklist and a four-phase flow diagram. The checklist includes items deemed essential for transparent reporting of a systematic review. In this explanation and elaboration document, we explain the meaning and rationale for each checklist item. For each item, we include an example of good reporting and, where possible, references to relevant empirical studies and methodological literature. The PRISMA statement, this document, and the associated website (www.prisma-statement.org/) should be helpful resources to improve reporting of systematic reviews and meta-analyses.

Medical issues associated with commercial flights

Almost 2 billion people travel aboard commercial airlines every year. Health-care providers and travellers need to be aware of the potential health risks associated with air travel. Environmental and physiological changes that occur during routine commercial flights lead to mild hypoxia and gas expansion, which can exacerbate chronic medical conditions or incite acute in-flight medical events. The association between venous thromboembolism and long-haul flights, cosmic-radiation exposure, jet lag, and cabin-air quality are growing health-care issues associated with air travel. In-flight medical events are increasingly frequent because a growing number of individuals with pre-existing medical conditions travel by air. Resources including basic and advanced medical kits, automated external defibrillators, and telemedical ground support are available onboard to assist flight crew and volunteering physicians in the management of in-flight medical emergencies.

[The GRADE System. An international approach to standardize the graduation of evidence and recommendations in guidelines]

Clinical practice guidelines have become an important source of information to support clinicians in the management of individual patients. However, current guideline methods have limitations that include the lack of separating the quality of evidence from the strength of recommendations. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) working group, an international collaboration of guideline developers, methodologists, and clinicians have developed a system that addresses these shortcomings. Core elements include transparent methodology for grading the quality of evidence, the distinction between quality of the evidence and strength of a recommendation, an explicit balancing of benefits and harms of health care interventions, an explicit recognition of the values and preferences that underlie recommendations. The GRADE system has been piloted in various practice settings to ensure that it captures the complexity involved in evidence assessment and grading recommendations while maintaining simplicity and practicality. Many guideline organizations and medical societies have endorsed the system and adopted it for their guideline processes.

Fundamental questions about genes, inactivity, and chronic diseases

Currently our society is faced with the challenge of understanding the biological basis for the epidemics of obesity and many chronic diseases, including Type 2 diabetes. Physical inactivity increases the relative risk of coronary artery disease by 45%, stroke by 60%, hypertension by 30%, and osteoporosis by 59%. Moreover, physical inactivity is cited as an actual cause of chronic disease by the US Centers of Disease Control. Physical activity was obligatory for survival for the Homo genus for hundreds of thousands of years. This review will present evidence that suggests that metabolic pathways selected during the evolution of the human genome are inevitably linked to physical activity. Furthermore, as with many other environmental interactions, cycles of physical activity and inactivity interact with genes resulting in a functional outcome appropriate for the environment. However, as humans are less physically active, there is a maladaptive response that leads to metabolic dysfunction and many chronic diseases. How and why these interactions occur are fundamental questions in biology. Finally, a perspective to future research in physical inactivity-gene interaction is presented. This information is necessary to provide the molecular evidence required to further promote the primary prevention of chronic diseases through physical activity, identify those molecules that will allow early disease detection, and provide society with the molecular information needed to counter the current strategy of adding physical inactivity into our lives.