Between 1991 and 2000 a total of 263 patients from other hospitals were transferred to our ICU for specialized treatment for ARDS: 187 (71%) patients survived and were discharged from the ICU, and 76 (29%) died during their ICU stay (Figure ). Of these 187 survivors the contact address was not available in 55 cases, and three patients were found to have died after discharge after follow-up with family members. Of the remaining 129 patients (69%), 64 (49.6%) did not provide feedback, and 65 (50,4%) returned the completed questionnaires and gave written informed consent (Figure ). In the investigated patients the follow-up occurred at an average of 57 ± 32 months after discharge from the ICU (Table ). Their demographic and clinical characteristics are presented in Table . There were no significant differences between investigated patients and patients who were lost to follow-up apart from the period between discharge from the ICU and entry into the study. The demographic and clinical details of these non-participating patients were as follows (mean ± SD): age, 32.9 ± 15 years; gender, 60% male; duration of mechanical ventilation, 40 ± 30 days; cause of ARDS, sepsis 10%, pneumonia 47%, multiple trauma 31%, other 14%; severity of ARDS by lung injury score, 3.2 ± 0.3; and severity of illness by APACHE II score, 17 ± 6. Only one significant difference emerged: the mean period between discharge from ICU and attempted follow-up for the purposes of the study was considerably shorter in investigated patients (57 ± 32 months) than in those who did not participate (72 ± 36 months; t = - 2.9; p < 0.0005).
Demographic and clinical characteristics of patients studied
Post-traumatic stress disorder
At the time of this study, 18 patients (29%; 8 male, 10 female) were identified as being at increased risk for PTSD according to PTSS-10. Consequently we divided the entire study population into two subgroups: 'high-scoring patients' at increased risk of developing PTSD, and 'low-scoring patients'. PTSS-10 scores were significantly different between 'high-scoring patients' with increased risk for developing PTSD and 'low-scoring patients' (t = - 3.7; p < 0.0001; Table ). Demographic data for all participating patients and the two subgroups are presented in Table . There were no significant differences between the subgroups in relation to age, gender, period between discharge from ICU and entry into study, duration of mechanical ventilation, cause of ARDS, the severity of ARDS as measured by means of lung injury score, or severity of illness by APACHE II score. Requirements for extracorporeal membrane oxygenation were also comparable between groups. In relation to length of stay (t = - 1.95; p < 0.056) and employment status (χ2(3) = 8.2; p < 0.084) we observed a trend towards a difference between groups. 'High-scoring patients' tended to be disabled more frequently and to stay longer on the ICU (Table ).
A significant positive correlation between the number of traumatic memories and the severity of PTSD was revealed (Spearman r = 0.522; p < 0.0001; Table ). In particular, a significant positive relationship between the experience of anxiety in the ICU and an increased risk of developing PTSD was demonstrated (χ2(1) = 7.59; p < 0.01; Table ). 'High-scoring patients' at an increased risk of developing PTSD showed a tendency to recall experiences of pain more often. The whole patient group recalled nightmares or difficulties in breathing more frequently than anxiety or pain. Only experiences of anxiety differed significantly between the subgroups (Table ).
Effect of number of traumatic memories on symptoms of post-traumatic stress disorder
Effect of several traumatic memories on post-traumatic stress disorder
Health-related quality of life
HRQoL measured by SF-36 in all patients with ARDS investigated was significantly reduced in all dimensions, physical as well as mental, in comparison with age- and gender-matched healthy controls (Figure ). Using MANOVA we detected a significant difference between 'high-scoring patients', 'low-scoring patients' and healthy controls, and verified a significant effect between subject factor 'group' in both main dimensions (physical and mental component summary) and in all subdimensions of HRQoL. Post-hoct tests revealed a significant difference between 'high-scoring patients' and 'low-scoring patients' in the mental component summary as well as in all subdimensions of mental health (Table ). In contrast, 'low-scoring patients' were not different from healthy controls in the mental component summary (Figure ) and the subdimension mental health (Table ). With regard to the physical component summary, post-hoc tests revealed a significant difference between healthy controls, and 'high-scoring patients' and 'low-scoring patients' suffering from ARDS as well as in the subdimensions physical function, physical role function, bodily pain and general health (Table ). In contrast, there was no significant difference in the physical component score (Figure ), bodily pain and physical role function between 'high-scoring patients' and 'low-scoring patients' (Table ).
Figure 2 Subdimensions of health-related quality of life. Subdimensions of health-related quality of life were measured with the Medical Outcomes Study 36-Item Short Form (SF-36; physical function, physical role function, bodily pain, general health, vitality, (more ...)
Health-related quality of life
Figure 3 Difference in mental and physical component summary between groups. The mental and physical component summary of health-related quality of life was measured with the Medical Outcomes Study 36-Item Short Form (SF-36), comparing between 'high-scoring patients' (more ...)
Psychological problems measured by the Symptom Checklist-90-R were significantly more intense for 'high-scoring patients' than for 'low-scoring patients' in all dimensions (t values more than 1 SD over the mean for all scales (mean 50, SD 10); Table ).
Perceived social support, measured by using the total score from the Questionnaire for Social Support, was significantly higher for 'low-scoring patients' than for the 'high-scoring patients' (t = 2.90; p < 0.01). Using the F-Sozu, we demonstrated a significantly higher subdimension score for perception of emotional support (t = 2.24; p < 0.05) and social integrity for 'low-scoring patients' (t = 3.53; p < 0.01; Table ). The perceived social support correlated negatively with the value of the PTSD score (Pearson correlation r = - 0.31; p < 0.05; Figure ).
Figure 4 Correlation of perceived social support and posttraumatic stress. The total sum score of questionnaire F-Sozu and post-traumatic stress disorder (PTSD) score is shown. Severity of PTSD was verified with the Post-Traumatic Stress Syndrome 10-Questions (more ...)
Period between discharge from intensive care unit and study
Testing the period between discharge from ICU and study as a covariable, a MANOVA could not detect any influence on PTSD scores, severity of PTSD, distribution of percentages of patients suffering from recollections, psychological impairments, perceived social support and HRQoL with the exception of one subdimension of HRQoL: physical role function.