| 1. |
- Bergkvist, Max, 1976-
(författare)
-
Studies on Polarised Light Spectroscopy
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis project focuses on measurements of dermal microcirculation during vascular provocations with polarised light spectroscopy. This is done with a non-invasive method commercially available as Tissue viability imaging (TiVi) which measures concentration and oxygenation of red blood cells in the papillary dermis. Three studies were done with human subjects and one with an animal model, to validate and compare the TiVi technique with laser Doppler flowmetry, which is an established method of measuring dermal microcirculation.The TiVi consists of a digital camera with polarisation filters in front of the flash and lens, with software for analysis of the picture. When taking a picture with the TiVi, the polarised light that is reflected on the skin surface is absorbed by the second filter over the lens (which is perpendicular to the first filter) but a portion of light penetrates the surface of the skin and is scattered when it is reflected on tissue components. This makes the light depolarised, passes the second filter, and produces a picture for analysis. The red blood cell (RBC) has a distinct absorption pattern that differs between red and green colour compared to melanin and other components of tissue. This difference is used by the software that calculates differences in each picture element and produces a measure of output which is proportional to the concentration of red blood cells. The oxygenation of RBC can also be calculated, as there is a difference in absorption depending on oxygen state.The first paper takes up possible sources of error such as ambient light, and the angle and distance of the camera. The main experiment was to investigate how the local heating reaction is detected with TiVi compared to LDF.In the second paper arterial and venous stasis are examined in healthy subjects with TiVi.The Third paper is an animal study where skin flaps were raised on pigs, and the vascular pedicle is isolated to enable control of inflow and outflow of blood.The measurements were made during partial venous, total venous, and total arterial occlusion. The TiVi recorded changes in the concentration of RBC, oxygenation and heterogeneity and the results were compared with those of laser Doppler flowmetry.In the fourth paper oxygenation and deoxygenation of RBC: s was studied. Studies were made on the forearms of healthy subjects who were exposed to arterial and venous occlusion. Simultaneous measurements were made with TiVi and Enhanced perfusion and oxygen saturation or EPOS, which is a new device that combines laser Doppler flowmetry and diffuse reflectance spectroscopy in one probe.With TiVi, one can measure RBC concentration and oxygenation in the area of an entire picture or in one or multiple user defined regions of interest (ROI). Methods such as laser Doppler flowmetry makes single point measurements, which is a potential source of error both because of the heterogeneity of the microcirculation, and that the circulation be insufficient in the margins of the investigated area. TiVi has been able to measure venous stasis more accurately than laser Doppler flowmetry, and venous stasis is the more common reason for flaps to fail.The TiVi is an accurate way to measure the concentration of RBC and trends in oxygenation of the dermal microcirculation. It has interesting possible applications for microvascular and dermatological research, monitoring of flaps, and diagnosis of peripheral vascular disease. Future clinical studies are needed as well as development of the user interface.
|
|
| 2. |
- Bäckström, Denise, 1976-
(författare)
-
Injury mortality in Sweden; changes over time and the effect of age and injury mechanism
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Injuries are one of the most common causes of death in the world. Varying types of injuries dominate in different parts of the world, which also have separate influences mortality. In Scandinavia blunt injuries dominates and the majority of those who die do so pre hospital. Over time different injury pattern may vary and by analyzing this we can assess when, where and how preventive work can be reinforced. The aim of this thesis was to study injury epidemiology in Sweden and assess the contribution of different injury patters on mortality. Method: We used the Swedish cause of death and the national patient registries which have a complete national coverage. ICISS was calculated (based on ICD-10) in the in hospital population. We have chosen to do this investigation with a broad perspective using the term injury, which includes trauma but also other diagnoses like suffocation and drowning. Results: During the study period (1999-2012) the number of deaths because of injury was 1213, 25 388, and 18 332 among children, working age and elderly, respectively. Mortality declined in the children and in the working age but inclined in the elderly. Mortality increased with each age group except between the ages of 15–25 and 26–35 years. One thousand two hundred sixty four (97%) of those who died because of penetrating trauma (sharp objects and firearms) were killed by intentional trauma (assault and intentional self-harm). One thousand and seventeen (83%) of the children died prehospital. In the working age 22 211 (80%) of 25 388 died pre hospital. Nine thousand six hundred and eighteen (53%) of 18 332 of the elderly died prehospital. During 2001- 2011 the risk adjusted in hospital mortality decreased in traffic and assault but not in fall related injuries. Discussion: Largely, the anticipated injury mortality picture was found, with blunt injuries (traffic accidents) dominating in the working age and falls in elderly. Further a significant portion of the deaths occurred pre hospital. The intentional injuries are dominated by intentional selfharm. The decrease in child injury mortality is notable as Sweden already has one of the lowest incidences in child injury mortality in the world. The decrease in injury mortality in the working age also implies that preventive work has had an effect. The incline in injury mortality in elderly on the other hand needs to be further studied. Areas of particular importance for future preventive work is the incline in injury mortality in elderly and intentional injuries among children.
|
|
| 3. |
- Grossmann, Benjamin
(författare)
-
Procedural sedation : Aspects on methods, safety and effectiveness
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Safety and effectiveness are fundamental principles within the healthcare sector to provide quality of care and health improvement for patients. By ensuring that care is provided based on evidence-based knowledge, risks and complications can be minimised and the use of scarce resources optimised. An increasing demand for diagnostic and therapeutic procedures challenges the traditional methods for sedation regarding safety and effectiveness. It is desirable that the fundamental principles are improved when refining existing or developing new sedation methods. In this doctoral thesis, safety and effectiveness were evaluated for adult patient-controlled sedation (PCS) using propofol during two endoscopic procedures: endoscopic retrograde cholangiopancreaticography (ERCP) and flexible bronchoscopy (FB); and different doses of rectal racemic ketamine for paediatric (< 4 years) burn wound care.Methods: Data on vital functions, sedation level, safety interventions, procedure feasibility, patient-reported outcome and experience measures, and recovery, from three clinical randomised controlled trials were collected. Costs of sedation for the endoscopic procedures were compiled in a cost-analysis study.Results: PCS with propofol and bedside anaesthetic personnel was shown to be a safe and effective alternative method of sedation during ERCP and FB compared with intravenous sedation with midazolam. The PCS method gives stable cardiorespiratory conditions with few adverse events and interventions, with a low risk of oversedation. PCS offers similar (FB) or better (ERCP) procedure feasibility and patient satisfaction during the procedures than midazolam. Recovery after PCS is quick, minimises the risk for prolonged hospitalisation and is thereby a potential cost-saving sedation method. The optimal dose of rectal racemic ketamine, 6 mg/kg with the addition of 0.5 mg/kg midazolam during severely painful procedures, gives minimal risk for outbreaks of pain, offers stable vital signs conditions and allows rapid recovery without affecting procedure feasibility.Conclusions: The sedation method can be adjusted to type of procedure and patient population. PCS with propofol offers an alternative and reliable method for adult sedation during endoscopic procedures, whereas rectal racemic ketamine combined with midazolam provides good conditions for burn care dressing procedures in young children.
|
|
| 4. |
- Karlsson, Matilda, 1981-
(författare)
-
Studying the healing and long-term outcomes of two partial thickness wound models using different wound dressings
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Safe and effective wound dressing treatments are important for proper wound healing. Such procedures therefore need to be evidence-based regarding the most important outcome measures such as healing time, less discomfort for the patient, duration of hospital care and, importantly, less scarring. As the relation between longer healing times and more severe scarring is known, it is important to find dressing treatments that reduces such complications by providing fast and proper wound healing. In this thesis, four established wound dressing treatments (hydrofibre covered with film; porcine xenografts and polyurethane foam, with and without silver), were evaluated for two types of acute, partial thickness wounds: split thickness skin graft (STSG) donor sites and partial thickness burn wounds in two randomised, controlled clinical trials (RCT) with longterm scar follow ups. The relations between factors thought to influence wound healing and scarring as sex, infection, wound extent and depth, healing time and skin grafting were also investigated in these two wound models.Methods: Data from these trials were collected on sex, infection rates, wound depth and extent, need of skin grafting, healing times and scarring frequency together with demographic data. Scars were evaluated at 8 years in Study II and III and at 6 and 12 months after injury in Study V.Results: Two dressing treatments; hydrofibre covered with film and porcine xenografts gave significantly faster healing of the STSG donor sites than the standard of care (SOC) dressing, the polyurethane foam. The hydrofibre was thereafter implemented as the new SOC at the department. The long-term scar follow up showed that the hydrofibre group was most satisfied with their donor site scar, providing further evidence for the implementation of this dressing strategy. From the observer’s perspective no differences were found between these treatment groups. For partial thickness burns the treatment with a silvercontaining foam dressing showed significantly shorter healing time, whereas for the scars, no difference between dressing groups could be detected. A number of factors were identified that affected healing time: for donor sites only male sex was associated with shorter healing time. Sex was also the only factor that influenced donor site scarring, where female patients, both subjectively and objectively, were rated with higher scores (worse outcome). For partial thickness burns a larger extent of the burn wound, presence of deep dermal burns, and the need of skin grafting, all had a negative impact on both healing time and final scar. The final scar was also significantly affected by longer wound healing times and infection.Conclusion: The results suggest that the use of hydrofibre dressings covered with film on donor sites resulted in positive short-term and long-term outcomes. Regarding partial thickness burns, silver foam dressing resulted in faster healing but as for the final scar, no difference could be seen. Several factors were associated with longer healing times and more severe scarring such as: female sex, larger burns, deep dermal burns, skin grafting, and infection. Longer healing times were related to more severe scarring.
|
|
| 5. |
- Larsen, Robert, 1980-
(författare)
-
Risk-Adjustment for Swedish In-Hospital Trauma Mortality using International Classification of disease Injury Severity Score (ICISS) : issues with description and methods
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- IntroductionDifferent methods have been used to describe the epidemiology of trauma with varying results. Crude mortality outcome data differ significantly from risk-adjusted information. A previous standard method for risk-adjustment in trauma was the Injury Severity Score (ISS), although it has several shortcomings. In this thesis I examine Swedish injury statistics from an epidemiological perspective using crude and risk-adjusted mortality, and to adjust for injury I used the International Classification of disease Injury Severity Score (ICISS). The groups of most lethal injuries (fall, traffic, and assault) were examined separately using an ICISS mortality prediction model that focused particularly on the effects on the prediction of mortality by adding coexisting conditions (comorbidity) to it. Differences in mortality between the sexes and changes over time were tested separately.Material and MethodsData from all patients with ICD-10 based diagnoses of injury (ICD-10: V01 to Y36) in the Swedish National Patient Registry and Cause of Death Registry were collected from 1999 to 2012 and used for assessment of mortality and comorbidity. A subgroup (patients in hospital) from 2001-2011 were selected as the study group. Their injuries were in the subgroups of falls, traffic, and assaults, and are the focus of this thesis. Mortality within 30 days of injury was used as the endpoint. The severity of injury was adjusted for using the ICISS, which was first described by Osler et al. The model was also adjusted for age, sex, and comorbidities.ResultsThe study group comprised 815 846 patients (of whom 17 721 died). There was a decrease over time in injuries caused by falls and traffic (coefficient -4.71, p=0.047 and coefficient -5.37, p<0.001), whereas there was no change in assault-related injuries/100 000 inhabitants. The risk-adjusted 30-day mortality showed a decrease in injuries related to traffic and assault (OR 0.95, p<0.001 and OR 0.93, p=0.022) whereas for falls it remained unchanged. There was also a risk-adjusted survival benefit for women, which increased with increasing age. Adjusting for comorbidities made the prediction of 30-day mortality by the ICISS model better (accuracy, calibration, and discrimination). However, most of this effect was found to be the result of the other characteristics of the fall related injury group (they were older, and had more coexisting conditions).ConclusionDuring a 10-year period, there has been a significant overall decrease in crude as well as risk-adjusted mortality for these three injury groups combined. Within these groups there is a clear, risk-adjusted, female survival advantage. The ICISS model for the prediction of mortality improves when comorbidities are added, but this effect is minor and seen mainly among the injuries caused by falls, where comorbidity is significant. The ICISS method was a valuable adjunct in the investigation of data on Swedish mortality after injury that has been gathered from health care registry data.
|
|
| 6. |
- Mirdell, Robin, 1989-
(författare)
-
Blood Flow Dynamics in Burns
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Objectives:Burns of intermediate thickness are hard to evaluate clinically. This often leads to unnecessary delays of up to 14 days before a surgical decision can be made. To counter this, several objective methods have been developed to determine the healing potential of the wound. Over the years, measurement of perfusion has proven to be the most successful method for evaluation of healing potential. Laser Doppler imaging (LDI) is currently the most used method and can determine surgical need 2 days after injury with an accuracy >90%. There are however emerging techniques like laser speckle contrast imaging (LSCI), which also measure perfusion. LSCI have several advantages over LDI and is easier to use. LSCI can also investigate aspects of the microcirculation, previously not possible with LDI. The aim of this thesis was to investigate LSCI’s ability to evaluate surgical need in burns of indeterminate partial-thickness. The first objective was to investigate the dynamics of perfusion the first 14 days after injury. The purpose was to find the optimal time-window for perfusion measurements. The next goal was to determine the accuracy of different perfusion cut-offs. In this second study, the benefit of a subsequent measurement was also investigated. After this, interobserver variation between different profession groups was studied. Both the agreement of perfusion measurements and observer assessments were evaluated. Finally, cardiac vasomotion in combination with perfusion (pulsatility) was investigated as a method to determine surgical need <48 hours after injury. Methods:Perfusion was measured in a total of 77 patients at the Department of Plastic Surgery, Hand Surgery and Burns at Linköping University Hospital, Sweden. Most of these patients were children and the most common type of burn was scalds. A laser speckle contrast imager (PeriCam PSI System, Perimed AB, Järfälla, Sweden) was used to measure perfusion. Results: In the first paper we showed a clear relation between perfusion dynamics and the healing potential of the wound. The changes in perfusion were largest the first 5 days after injury, why this time interval was selected for subsequent papers. Perfusion measurements done day 3-4 after injury could predict surgical need with a sensitivity of 100% (95% CI: 83.9-100%) and a specificity of 90.4% (95% CI: 83.8-94.9%). If two measurements were used, <24 hours and 3-4 days after injury, the accuracy was 100%. Furthermore, we found that different observers could consistently predict perfusion, while there was a large variation in their clinical assessments. This was not improved by extensive burn experience. Finally, pulsatility could be used to predict surgical need the same day as the injury occurred with a sensitivity of 100% (95% CI: 88.1-100%) and a specificity of 98.8% (95% CI: 95.7- 99.9%). Conclusions: LSCI is a promising method for evaluation of burns and provides several benefits over LDI. The surgical need of burns can be determined mere hours after injury when pulsatility is measured. However, the benefits of early scald diagnostics in children with LSCI need to be evaluated in a prospective study before the method is ready for routine clinical use.
|
|
| 7. |
- Pompermaier, Laura, 1975-
(författare)
-
Outcome of burn care : the mortality perspective
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Despite the improvements in burn care during the last decades, burns remain catastrophic for the patients and a challenge for the care-givers. The early outcome of burn care is to assess its quality and to improve it, but the crucial outcome is mortality, which is the main focus of this thesis. In particular, I address questions about mortality that have arisen from working with burned patients and that can have clinical consequences: the impact of pre- existing medical conditions; long-term survival; the causes of unexpected deaths; and the possible differences between sexes in the provision of resources.Patients with burns share the fact that the time of their injury is known, its severity can be quantified from the size of the burn, and the care is relatively standardised. The analysis of outcome among burned patients treated at a single burn centre may therefore be of general value to others who treat burns.Methods: We retrospectively analysed data that had been collected prospectively (the burn unit database) from patients with burns admitted consecutively to a national burn centre in Sweden during the last 25 years.Results: Age and percentage of total body surface area burned (TBSA %) affected the in- hospital mortality, whereas pre-existing medical conditions did not influence the prediction of outcome (Paper I). After discharge, both age and the presence of full thickness burns reduced the long-term survival, whereas the extent of the burn (TBSA %) did not (Paper II). Most patients with moderate burns who die in hospital despite a good prognosis, die for reasons other than the burn (Paper III). Previously, it has been shown that sex is not an independent factor for mortality during burn care; in this thesis we show that the sex of the patients did not affect the number of medical interventions given either (Paper IV).Conclusion: The addition of “coexisting condition” to a mortality model based on age and size of burn does not improve its predictive value; rather, the factor “age” is sufficient to adjust for comorbidity in the assessment of a burn and its outcome (Paper I).If patients with burns survive, the long-term prognosis is good. The effect of age is the one that governs survival, whereas the effect of the extent of the burn ends when the patient is discharged (Paper II).The in-hospital mortality during burn care is low, but some patients die for reasons other than the actual burn (Paper III).In a centre where the mortality is independent of the sex of the patient, the provision of medical interventions is also equal between men and women (Paper IV).
|
|
| 8. |
- Wilhelms, Susanne, 1985-
(författare)
-
The epidemiology of severe sepsis in Sweden : Methodological aspects on the use of ICD coding in national registries
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Severe sepsis is characterized by acute organ dysfunction caused by an infection. Despite advanced treatment with antibiotics and organ support the mortality remains high. The epidemiological research on severe sepsis has expanded over the years but has led to conflicting results. In this thesis, we present evidence that some of these conflicting results may be explained by inappropriate methods used in epidemiological studies on severe sepsis. The definition of severe sepsis relies on consensus criteria including a number of clinical signs, parameters and laboratory findings. To facilitate large nation-wide studies on the incidence of severe sepsis in already existing administrative datasets, several investigators have attempted to mirror the clinical criteria by using combinations of the International Classification of Diseases (ICD) codes for infection and organ dysfunction. In paper I of this thesis, however, we found that three different ICD code abstraction strategies applied on the same dataset (the Swedish National Patient Register) generated three almost separate cohorts of patients. Furthermore, in paper II, where we followed intensive care unit (ICU)-treated patients with severe sepsis according to clinical consensus criteria to discharge, we observed that most patients did not meet any ICD code abstraction strategies for severe sepsis when reviewing their ICD codes registered at discharge from the hospital. In conclusion, the ICD code abstraction strategies previously used in the epidemiological research on sepsis seem to be inaccurate in the Swedish setting. Sepsis may also result in poor long-term outcomes, and contribute to an increased risk of late mortality. However, the actual causes of late mortality in sepsis remain unclear. In paper III, we investigated causes of death over 1 year after treatment of sepsis in the ICU. In this study, a matched control group consisting of ICU-treated patients without sepsis was included. The most common causes of late mortality in both the sepsis group and the control group were heart diseases and cancer. The sepsis group, however, had a significantly increased incidence of infectious-related deaths compared with the control group, even over 1 year after the initial ICU event.
|
|
