Background: The aim of this publication is to demonstrate similarities and differences in the association of risk factors with the prevalence of different manifestations of chronic venous disease (CVD), like varicose veins (VV), venous oedema (C3) and severe chronic venous insufficiency (CVI) in the population-based cross-sectional Bonn Vein Study 1 (BVS). Patients and methods: In the BVS 1 between 13.11.2000 and 15.3.2002, 3.072 participants, 1350 men and 1722 women, from a simple random sample of the general population of the city of Bonn and two rural townships aged 18-79 years were included. The overall response proportion was 59%. All participants answered a standardized questionnaire including information about socio-economic data, lifestyle, physical activity, medical history, and quality of life. Venous investigations were performed clinically and by a standardized duplex examination by trained investigators. The CEAP classification in the version of 1996 was used to classify the findings. Logistic regression models were performed for the association of possible risk factors with VV, venous edema (C3) and severe CVI (C4-C6). The predictive risk (PR) describes the association of the diseases and the possible influencing factors. Results: VV, venous oedema (C3) and severe CVI (C4-C6) have common risk factors like higher age, number of pregnancies, family history of VV and overweight or obesity. Female gender is significantly associated with VV and C3 but not with severe CVI (C4-C6). High blood pressure and urban living are only associated with C3 and C4-C6 disease whereas prolonged sitting is associated with C3 and lower social class with C4-C6 exclusively. Discussion: In many epidemiological studies risk factors were associated with chronic venous disorders in general. Our data show that VV, venous edema and severe CVI may have different risk profiles. Venous edema is more often associated with arterial hypertension and sedentary lifestyle whereas lower social class seems to be a risk factor for severe CVI including venous ulcers. Conclusions: The differences in the association of risk factors to VV, venous edema and severe CVI should be considered if prevention and treatment of chronic venous diseases are planned. As examples, compression stockings could be proposed in sitting profession to prevent oedema, VV patients with risk factors like obesity might benefit from early treatment for VV and obesity. More longitudinal evaluation of risk factors is necessary to evaluate the true risk profile of CVD.

Abstract Objective To assess the natural history of saphenous and non-saphenous varicose veins using the results of the Bonn Vein Studies and data published in literature. Methods We used the data of the Bonn Vein Studies (BVS) 1 and 2 to assess if preexisting non-saphenous varicose veins (NSVV) in persons who had no saphenous varicose veins (SVV) at baseline have an impact on the incidence of SVV during the follow-up of 6.6 years and vice versa. SVV where defined as tortuous or not-tortuous refluxing saphenous veins. The statistical evaluation was performed using SAS version 9.4 (SAS Institute, Cary, North Carolina). In addition, we performed a review of publications concerning the natural history of varicose veins (VV) using PubMed. Results In the BVS the overall incidence of SVV within the follow-up time of 6.6 years was 8.0 % (n = 133 of 1661; 95 % CI: 6.8–9.4). 7.2 % (n = 107 of 1492) without VV in BVS 1 and 19.8 % (n = 26) of patients with preexisting NSVV developed SVV. The relative risk for the development of SVV in patients with preexisting NSVV was 2.44 (95% CI: 1.64–3.64) adjusted for age and sex. The overall incidence of NSVV was markedly higher with 13.3 % (n = 226 of 1661; 95 % CI: 11.8–15.1). During follow-up 148 patients (9.9 %) without VV in BVS 1 developed NSVV. 48.5 % (n = 78) of patients with preexisting SVV developed NSVV during follow-up. The relative risk for the development of NSVV in patients with preexisting SVV was 4.10 (95% CI: 3.26–5.16), adjusted for age and sex. In published studies the development of VV is preceded by venous reflux. Initial VV may develop at any segment and the results from literature suggest that the location of VV and reflux at the time of the investigation depends on age. In younger individuals more distal location are reported with an ascending progression in the majority but also descending progression is possible. Conclusions Based on the results of the Bonn Vein Studies 1 and 2 we could demonstrate, that preexisting SVV increase the risk of developing NSVV and preexisting NSVV increase the risk of developing SVV in a similar way. Venous reflux may initially occur in any segment of the venous system and may progress in antegrade and/or retrograde fashion. In younger adults initial VV seem to be localized more often in distal parts of the legs with an antegrade progression over time.

Objective: To determine the diagnostic accuracy of the ICHD3 diagnostic criteria for vestibular migraine in a real-world clinical setting. Background: Dizziness and vertigo are common complaints of patients with migraine. The strong relation of vestibular symptoms with migraine lead to the term vestibular migraine, but it’s clinical classification is widely discussed. The Barany Society and the International Headache Society together proposed new diagnostic criteria and put them up to be tested in research as well as clinical work. Design/Methods: 130 patients with vestibular migraine were re-evaluated by telephone interview with the new ICHD 3 beta diagnostic criteria. The initial diagnosis was made during outpatient consultation in a tertiary dizziness clinic. As control group 30 patients with a clinically confirmed diagnosis of migraine with or without aura were also re-evaluated using the same questionnaire. The initial diagnosis was made in a tertiary headache center. The Mean age was 46,3 +/− 14 years and 75% of participants were women. Results: The ICHD 3 beta criteria showed a sensitivity of 76.5 % and a specificity of 72.5%. Only 50% of patients had a temporal association of headache and vestibular symptoms. Most important diagnostic factors were the total amount of endured vertigo attacks (≥ 5), presence of one of the following specific vertigo characteristics (internal, external, spontaneous, visual vertigo, positional vertigo and aggravation by head movement), the presence of headache, at least 2 out of 4 migraine criteria (unilateral location, pulsating character, moderate to severe pain intensity, aggravation by physical activity), phono-/photophobia, nausea/vomiting, and aura (visual, sensible, aphasia). Conclusions: The sensitivity and specificity of the proposed vestibular migraine diagnostic criteria were comparable to other ICHD diagnostic criteria, but may be reduced to a few key criteria. Study Supported by: N/A Disclosure: Dr. Obermann has nothing to disclose. Dr. Lippegaus has nothing to disclose. Dr. Bock has nothing to disclose. Dr. Katsarava has nothing to disclose. Dr. Holle has nothing to disclose.

Background Trigeminal neuralgia is characterized by paroxysmal facial pain attacks. Adequate prophylactic drug therapy is often limited by the lack of efficacy and intolerance due to central nervous system side effects. Subcutaneous injections of botulinum toxin type A are a promising treatment option for patients with unsatisfactory response to drug therapy or neurosurgical intervention. Its effects are expected to last for at least 3 months, so it could be a potential long-term treatment. This is the study protocol of a prospective, placebo-controlled, double blind clinical trial investigating the add-on therapy of subcutaneous administration of botulinum toxin type A injections to standard treatment in therapy-refractory classical trigeminal neuralgia. Methods and design BoTN is a prospective, double blind, placebo-controlled trial with a randomized withdrawal design in which a single blind phase is followed by a double blind phase (see also Methods and design). Eligible patients with classical trigeminal neuralgia who are otherwise refractory to medical and neurosurgical treatment will receive subcutaneous injections of botulinum toxin type A into injection sites of the affected trigeminal branch. In the first phase all patients will receive botulinum toxin type A in a single blinded intervention. Twelve weeks later therapy responders will be allocated to the verum or placebo (saline) arm in a double blind, randomized manner. These injections will be performed at the same sites as the first injections. This trial will be conducted in a tertiary outpatient clinic specialized in the treatment of headache and facial pain. There will be three investigators performing the injections who are experienced in the treatment of headache and facial pain and trained in botulinum toxin type A injections. Discussion BoTN is designed to assess the efficacy and safety of subcutaneous botulinum toxin type A injections in addition to standard prophylactic treatment in therapy-refractory trigeminal neuralgia. Trial registration number EU Clinical Trials Register: EudraCT-No: 2014-001959-24 https://www.clinicaltrialsregister.eu/ctr-search/rest/download/trial/2014-001959-24/DE Date of trial registration 26 August 2014

OBJECTIVE: To determine the efficacy of multimodal therapy for the treatment of chronic vertigo and dizziness. BACKGROUND: The treatment options of chronic vestibular disorders depend on the underlying syndrome and often include vestibular rehabilitation physiotherapy, as well as cognitive behavioral therapy for psychogenic causes. In many patients vestibular and psychological symptoms coexist. DESIGN/METHODS: 234 patients with vertigo or dizziness were recruited prospectively from a tertiary dizziness center between March 2010 and April 2011. Most common diagnoses were somatoform vertigo, unilateral and bilateral vestibulopathy and central vestibular disorders. Patients were treated in the medical day care unit over five consecutive days and were encouraged to continue with their physiotherapy and psychological exercises at home. Different surveys were obtained (Dizziness Handicap Inventory (DHI), Quality of Life Questionnaire (SF-12), General Depression Scale (ADS), Stait-Trait Anxiety-Index (STAI), Whitely-Index and a custom health related questionnaire. These surveys were assessed again by qualified medical students during a personal telephone interview after two years. RESULTS: Primary outcome variable was the DHI Score at 2-years follow-up. DHI decreased by 18.7 ± 21.5 points after two years. Days with vertigo or dizziness decreased by 10.7 ± 12.5 days after two years compared to baseline. Depression, anxiety, and stress scores significantly decreased as well, while quality of life score increased at two year follow-up. Patients with somatoform vertigo seemed to benefit the most from this treatment regimen. CONCLUSIONS: Multimodal therapy is highly effective for the treatment of chronic vertigo and dizziness disorders. The decrease in DHI not only poses a statistically significant outcome, but is considered clinically significant as well. The consequent and systematic combination of physiotherapy and psychological intervention might be the best treatment approach in this highly disabled, heterogeneous and comorbid patient population. Study Supported by: None Disclosure: Dr. Obermann has received personal compensation for activities with Biogen Idec, Novartis, Sanofi-Aventis Pharmaceuticals, Pfizer Inc., and Teva Neuroscience. Dr. Bock has nothing to disclose. Dr. Sabev has nothing to disclose. Dr. Lehmann has nothing to disclose. Dr. Diener has nothing to disclose.

To investigate the long-term outcome of interdisciplinary treatment in a tertiary care neuro-otology institution after 2 years as part of the Dizziness and Vertigo Registry study. Risk factors associated with unfavourable outcome were assessed. 3113 consecutive patients with disorders of vertigo and dizziness were recruited prospectively between March 2010 and February 2012. Patients were clinically assessed and treated according to their diagnosis. Standardized instruments were used at baseline and at 2-year follow-up [Dizziness Handicap Inventory (DHI), Quality of Life Questionnaire, General Depression Scale, Stait-Trait Anxiety Index], as well as a custom health-related questionnaire. The primary outcome variable of this observational study was the change in DHI after 2 years. Patients suffered from phobic postural vertigo (23%), benign peripheral paroxysmal vertigo (14.4%), unilateral vestibulopathy (10.5%), central vestibular disorders (8%), Menière's disease (9.8%), vestibular migraine (6.9%), bilateral vestibulopathy (5.5%), and vestibular paroxysmia (3.1%). Mean disease duration was 4.6 ± 6.3 years. 1272 patients were available for follow-up, 1159 completed the DHI score. 72.1% of patients improved in DHI score from baseline to 2 years follow-up. Mean reduction in DHI score was 14 points (p = 0.02). Long-term outcome following diagnosis and treatment in a specialized tertiary care centre is good and persistent after 2 years. Risk factors for an unfavourable outcome were advanced age, severe disability, constant vertigo or dizziness, and concomitant back pain, while depression and anxiety did not contribute to this risk considerably.

Introduction We studied the association between stress intensity and headache frequency for tension-type headache (TTH), migraine and migraine with coexisting TTH (MigTTH). Method We studied a population-based sample of 5159 participants (21–71 years) who were asked quarterly between March 2010 and April 2012 about headache and stress. Log-linear regression in the framework of generalized estimating equations was used to estimate regression coefficients presented as percent changes to describe the association between stress intensity (modified visual analog scale (VAS) from 0 to 100) and headache frequency (days/month) stratified by headache subtypes and age groups and adjusted for sex, age, frequent intake of acute pain drugs, drinking, smoking, BMI and education. Results TTH was reported in 31% participants (48.1 ± 12.5years, 51.5% women, 2.2 ± 3.9 mean headache days/month, 52.3 ± 26.7 mean stress), migraine in 14% (44.8 ± 11.3years, 73.3%, 4.5 ± 5.2 days/month, 62.4 ± 23.3), MigTTH in 10.6% (43.5 ± 11.5 years, 61.0%, 3.6 ± 4.8 days/month, 58.6 ± 24.1), 23.6% were unclassifiable, and 20.8% had no headache. In participants with TTH an increase of 10 points on VAS was associated with an increase of headaches days/month of 6.0% (adjusted). Higher effects were observed in younger age groups (21–30/31–40/41–50/51–60/61–71 years: 9.8/10.2/7.0/6.5/3.5%). Slightly lower effects were observed for migraine (4.3%, 8.1/5.1/3.4/6.3/0.3%) and MigTTH (4.2%, 5.5/6.8/6.9/5.8/–0.7%). Conclusion Our study provides evidence for an association between stress intensity and headache frequency.

OBJECTIVE: To assess the prevalence of various diagnostic groups amongst patients with vertigo and dizziness presenting to a specialized tertiary care centre. To determine clinical features and demographic factors characteristic of specific diagnoses and their specific subjective burden. BACKGROUND: Vertigo is a common complaint in the general population with a prevalence between 20 and 30 [percnt]. The Schwindelzentrum Essen, Germany, is a specialized, outpatient clinic which provides multidisciplinary care for patients with chronic vertigo. From March 2010 till December 2013 6182 patients, who presented to the clinic for the first time took part in a standardized survey. DESIGN/METHODS: Prospective, observational study in tertiary care centre. RESULTS: 8182 patients (5659 female = 69,2[percnt]; 2523 male =30,8[percnt]) presented to the clinic: The five most common diagnoses were phobic postural vertigo (n=1162; 18.26[percnt]), benign paroxysmal positional vertigo (n=10003; 15,69[percnt]), unilateral vestibulopathy / vestibular neuritis (n=712; 9,06[percnt]), psychogenic vertigo (n=682; 9,6[percnt]) and Meniere’s disease (632; 9,62[percnt]). The average age was 56,3 years (range 10 to 96 years, SD=17,64) with a considerable variation between diagnoses. Symptom severity scores showed significant impairment in the patients abilities (DHI: Mean 47,1 ; Range 0-100; SD 22,3; VSS: Mean 33,63; Range 0 - 131; SD 19,6). CONCLUSIONS: This large dataset is helpful to provide a more accurate picture of specific vestibular disorders and their clinical presentation. Furthermore it allows insightful correlations to demographics and personal burden. Disclosure: Dr. Burmeister has nothing to disclose. Dr. Bock has nothing to disclose. Dr. Gerwig has nothing to disclose. Dr. Frings has nothing to disclose. Dr. Arweiler-Harbeck has nothing to disclose. Dr. Diener has received research support from Merck, Pharm-Allergan GmbH, ElectroCore, Amgen, and Novartis. Dr. Obermann has received personal compensation for activities with Biogen Idec, Novartis, Sanofi-Aventis Pharmaceuticals, Pfizer Inc., and Teva Neuroscience.

Background Trigeminal neuralgia (TN) is a chronic disorder characterized by paroxysmal facial pain. Adequate prophylactic drug therapy is often limited by the lack of efficacy and intolerance due to central nervous system side effects. Subcutaneous injections of botuinum toxin type A (BT-A) are a promising treatment option for patients with insatisfactory response to drug therapy or neurosurgical intervention. This is the study protocoll of a prospective, placebocontrolled, double blind clinical trial investigating the add-on therapy of subcutaneous of BT-A injections to standard treatment.

Methods The German Headache Consortium studied a populationbased sample of 5,159 participants (21-71years) who were asked every three months between March 2010 and April 2012 about headache and stress. Log-linear regression in the framework of Generalized Estimating Equations was used to estimate regression coefficients presented as percent changes to describe the association between stress intensity (visual analogue scale [VAS] from 0-100) and headache frequency (days/month) stratified by headache subtypes and age groups. Percent changes were adjusted for sex, age, frequent intake of acute pain drugs, drinking, smoking, body mass index and education.

OBJECTIVE: We evaluated the association between stress intensity and headache frequency for tension type headache (TTH), migraine and migraine with coexisting TTH. BACKGROUND: It is supposed that stress can be a predisposing factor contributing to the onset of headache disorders, that it accelerates the progression to chronic headache, provokes and exacerbates headache episodes and that the headache experience itself can serve as a stressor. METHODS: We analyzed data of the population-based German Headache Consortium Study, which included 5,159 participants aged 21-71 years. The participants were screened quarterly from 2010-2012, using validated questionnaires. Headache subtypes were defined according to the criteria of the International Headache Society. Poisson log-linear regression in the framework of Generalized Estimating Equations was used to estimate the effects of stress intensity on headache frequency (days/month) for different headache subtypes, using a visual analogue scale (VAS) from 0-100. Percent changes with 95% confidence intervals (95%CI) were adjusted for sex, age, frequent intake of acute pain drugs, drinking, smoking, body mass index and education. RESULTS: TTH was reported in 1,598 (31%) participants (48.1±12.5 years, 51.5% women, 2.2±3.9 mean headache days/month, 52.3±26.7 mean stress), migraine in 14.0% (44.8±11.3, 73.3%, 4.5±5.2, 62.4±23.3), migraine with coexisting TTH in 10.6% (43.5±11.5, 61%, 3.6±4.8, 58.6±24.1), unclassifiable headache in 17.3%. Participants experienced an increase in headache frequency with increasing stress intensity independent of headache subtype. The highest effects were observed in participants with TTH: increase of 10 points on the VAS in stress intensity was associated with a 6.3% (95%CI: 4.3-8.3%) increase in headache days/month, migraine 4.3% (2.4-6.2%), migraine with coexisting TTH 4.0% (1.8-6.3%). CONCLUSIONS: This large prospective population-based cohort study provides evidence for an association between stress intensity and headache frequency. Our findings are of importance for stress management approaches in headache patients. Disclosure: Dr. Schramm has nothing to disclose. Dr. Moebus has nothing to disclose. Dr. Lehmann has nothing to disclose. Dr. Galli has nothing to disclose. Dr. Obermann has received personal compensation for activities with Biogen Idec, Novartis, Sanofi-Aventis Pharmaceuticals Inc., Pfizer Inc., and Teva Neuroscience. Dr. Obermann has received research support from the German Federal Ministry of Education and Research, and Allergan Inc. Dr. Bock has nothing to disclose. Dr. Yoon has nothing to disclose. Dr. Diener has received personal compensation for activities with Merck & Co., Inc. Allergan, Inc., Electrocore, Amgen Inc., and Novartis. Dr. Diener has received research support from Merck & Co., Inc., Allergan, Inc., Weber & Weber, and Electrocore. Dr. Katsarava has received personal compensation for activities with Allergan Inc., Bayer Pharmaceuticals Corp., Biogen Idec, and Merck & Co. Inc. Dr. Katsarave has received research support from Allergan Inc., Bayer Pharmaceuticals Corp., Biogen Idec, and Merck & Co. Inc.

Zusammenfassung Hintergrund: Obwohl die Therapie mit Kompressionsstrümpfen (MKS) ein sehr häufiges Therapieprinzip ist, gab es in der Vergangenheit nur wenige Daten zur Frage der Verordnungshäufigkeit und den Erfahrungen der Patienten mit dieser Therapie. Patienten und Methodik: In der Bonner Venenstudie 1 wurden 3 072 Probanden im Alter zwischen 18 und 79 Jahren (1 350 Männer/1 722 Frauen) aus der Durchschnittsbevölkerung eingeschlossen. 2007 und 2008 wurde das Kollektiv zu einer Nachfolgeuntersuchung eingeladen (Bonner Venenstudie 2). Insgesamt konnten 1 978 Probanden der Bonner Venenstudie 1 nachuntersucht werden. Die vorliegende Arbeit verknüpft die Ergebnisse beider Untersuchungen. Ergebnisse: 14,6 Prozent gaben in der Bonner Venenstudie 1 an, in der Vergangenheit MKS getragen zu haben (7,5 % der Männer, 20,3 % der Frauen). Im Mittel gaben 71,3 % der Befragten an, dass sich unter der MKS-Therapie die zugrundeliegende Erkrankung gebessert hätte. Die Verordnung von MKS nahm im Nachbeobachtungszeitraum (Bonner Venenstudie 2) in den höheren klinischen Stadien der chronischen Venenkrankheiten zu: C2 12,2 %, C3 19,1 % und C4–C6 27,0 %. Bei Probanden mit fortgeschrittenen Venenkrankheiten (von Hautveränderungen bis zum Ulcus cruris) wurden bei ca. 60 % in den zurückliegenden 6,6 Jahren keine Kompressionsstrümpfe oder Kompressionsverbände verordnet. Schlussfolgerungen: Die vorgelegten Ergebnisse zeigen, dass MKS die häufigste venöse Therapie in Deutschland sind. Gleichzeitig besteht eine eklatante Unterversorgung mit diesem Basistherapeutikum für chronische Venenkrankheiten.

Background: According to the WHO headache disorders are a public-health concern given the large amount of associated disability and financial costs to society. Headache disorders result in personal and societal burdens of pain, disability, damaged quality of life and high financial costs. However, evidence based knowledge about headache triggering factors is lacking. Especially studies are missing, evaluating the effect of stress on headache frequency with regard to subtypes of headaches. Therefore we studied the effect of stress intensity on headache frequency for the main headache subtypes tension type headache (TTH), migraine and migraine with coexisting TTH using data of a prospective population-based cohort study. Methods: We analysed data of the German Headache Consortium Study including 5,159 participants aged 21 – 71 years, screened quarterly from 2010 – 2012, using validated questionnaires. Headache subtypes were defined according to the criteria of the International Headache Society. Poisson log-linear regression in the framework of Generalized Estimating Equations was used to investigate the effect of stress intensity (visual analogue scale from 0 – 100%) and headache frequency (0 – 30/31 days/month) on different headache subtypes by estimating percent change with 95% confidence intervals (95% CI), adjusting for gender, age and frequent intake of acute pain drugs, drinking, smoking and body mass index. Results: At baseline, TTH was observed in 1,598 (31%) participants (aged 48.1 ± 12.5 years, 51.5% women) with self-reported 2.2 ± 3.9 mean headache days/month, and a mean stress intensity of 52.3%± 26.7%. Participants with migraine (14.0%) were on average younger (44.8 ± 11.3 years), more often women (73.3%) and reported a higher frequency of headaches (4.5 ± 5.2 days/month) and a higher stress intensity (62.4%± 23.3%). Similar results could be observed for those with migraine with coexisting TTH (10.6%, 43.5 ± 11.5 years, 61% women), however with a lower frequency of headaches (3.6 ± 4.8 days), and stress intensity (58.6%± 24.1%) in 19.9% of the participants the headache type was not classifiable. During follow up, participants experienced an increase of headache frequency with increasing stress intensity independently of headache subtype. Notably, highest effects were observed in participants with TTH: a 10% increase of stress intensity resulted in a 6.2% (95% CI: 4.2 – 8.1%) increase of headache days/month. In participants with migraine and in participants with migraine with coexisting TTH the increase was identical with an increase of resp. 3.9% (2.0 – 5.8%) and 4.0% (1.8 – 6.2%). Conclusion: This is the first prospective population-based cohort study which shows that increasing stress resulted in increasing headache days, which was particularly pronounced in participants with TTH. Consideration of these findings is of importance for tailored anti-stress treatment approaches in headache patients with different subtypes of headaches.

Background: Despite the frequent use of medical compression stockings (MCS), reliable data are lacking on the frequency of MCS use and experience of patients with the treatment.Patients and methods: The Bonn Vein Study included 3,072 participants from the general population aged 18 to 79 years (1,350 men/1,722 women). Between 2007 and 2008 (Bonn Vein Study 2) 1,978 participants from the Bonn Vein Study 1 were reinvestigated. This paper combines the results of both investigations.Results: 14.6 % (7.5 % men, 20.3 % women) reported having previously undergone treatment with compression stockings. A mean of 71.3 % reported an improvement in their venous disease as a result of MCS treatment. During the 6.6 years of follow-up (Bonn Vein Study 2), significantly more prescriptions of MCS were given to patients in higher CEAP clinical stages. 12.2 % of the population in C2 was treated with MCS as were 19.1 % in C3 and 27.0 % in C4-C6. Among participants with chronic venous insufficiency (CVI) (skin changes up to venous ulcers), about 60 % were not treated by MCS or bandages in the past years.Conclusions: These results show that MCS is the most common treatment of venous disorders in the German population. At the same time, these figures also demonstrate severely lacking treatment with MCS in CVI.

BACKGROUND:In a prospective randomized trial the effect of prone positioning on the duration of mechanical ventilation was evaluated in multiple trauma patients and was compared with patients ventilated in supine position. METHOD:Multiple trauma patients of the intensive care units of two university hospitals were considered eligible if they met the criteria for acute lung injury or the acute respiratory distress syndrome. Patients in the prone group (N = 21) were kept prone for at least eight hours and a maximum of 23 hours per day. Prone positioning was continued until a PaO2:FiO2 ratio of more than 300 was present in prone as well as supine position over a period of 48 hours. Patients in the supine group (N = 19) were positioned according to standard care guidelines. RESULTS:The duration of ventilatory support did not differ significantly (30 +/- 17 days in the prone group and 33 +/- 23 days in the supine group). Worst case analysis (death and deterioration of gas exchange) displayed ventilatory support for 41 +/- 29 days in the prone group and 61 +/- 35 days in the supine group (p = 0.06). The PaO2:FiO2 ratio increased significantly more in the prone group in the first four days (p = 0.03). The prevalence of Acute Respiratory Distress Syndrome (ARDS) following acute lung injury (p = 0.03) and the prevalence of pneumonia (p = 0.048) were reduced also. One patient in the prone and three patients in the supine group died due to multi organ failure (p = 0.27). CONCLUSIONS:Intermittent prone positioning was not able to reduce the duration of mechanical ventilation in this limited number of patients. However the oxygenation improved significantly over the first four days of treatment, and the prevalence of ARDS and pneumonia were reduced.