Using Impedance Plethysmography to Evaluate Antidecubital Underlay Systems for Chronically Immobilized Patients*

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1 original papers Adv Clin Exp Med 2010, 19, 5, ISSN X Copyright by Wroclaw Medical University Emilia Irzmańska 1, Magdalena Charłusz 2, Jolanta Kujawa 2, Jan Kowalski 3, Lucjan Pawlicki 3, Robert Irzmański 2 Using Impedance Plethysmography to Evaluate Antidecubital Underlay Systems for Chronically Immobilized Patients* Zastosowanie pletyzmografii impedancyjnej do oceny podłoży przeciwodleżynowych u chorych przewlekle unieruchomionych 1 Department of Personal Protective Equipment, Central Institute for Labour Protection, National Research Institute, Warszawa, Poland 2 Laboratory of Ergonomics and Exercise Physiology, Medical University of Lodz, Łódź, Poland 3 Clinic of Internal Diseases and Cardiological Rehabilitation, Medical University of Lodz, Łódź, Poland Abstract Background. Recently more and more attention has been paid to the design of variable-geometry mattresses that provide differentiated pressure on the skin. However, the mattress is only one component of an antidecubital underlay system, and it is the bed sheets that come into direct contact with the patient s skin. It therefore seems that the properties of the bed sheet fabric the layer in direct contact with the skin resulting from the type of fibers used, their spatial layout in the fabric structure and the type of contact with the patient s body (point contact or continuous contact) are of significance in the prevention of skin lesions. The use of fibers with varying degrees of water absorbency both hydrophilic and hydrophobic fibers, with the hydrophobic layer directly under the skin of a person who is immobilized long-term may help to stabilize heat distribution and humidity when the thermoregulation mechanism is disrupted. It may also improve the efficacy of vascular perfusion in areas at the highest risk of decubitus ulceration. Objectives. To evaluate impedance plethysmography as a method of assessing local blood flow in areas at risk of decubitus ulcer formation in chronically immobilized persons. Material and Methods. The study involved 47 people. The examinations were performed in four groups and two subgroups of patients. The used antidecubital underlay systems were modified, using bed sheets of corrugated fabric in group 2 and subgroup 2a, while in group 3 and subgroup 3a, bed sheets with satin weave were used. In Group 4, traditional cotton bed sheets with linen weave were used. The method of impedance pletismography was applied for evaluation of local blood flow changes in areas at high risk of decubital ulceration development in chronically immobilised patients with normal and increased body temperature. Tissue blood flow changes were measured, following the procedure, described in the instruction manual of the used Niccomo monitor (Medis, Germany), designed for evaluation of haemodynamic parameters by the method of impedance cardiography with an adapter for plethysmographic measurements. Taking into account the available parameters, the selection for evaluation included those which were reflected by the plethysmographic curve, drawn by the monitor for the examined area in an on-line examination mode. Results and Conclusions. The study shows that using impedance plethysmography to evaluate local blood flow changes in chronically immobilized patients is a useful method for precise and repeatable monitoring of flow parameters in the area under examination. It also serves to prompt appropriate prevention activities and the preparation of anti-decubitus underlay structures at the early stages of skin lesion formation in patients who are bedridden long-term with restricted body positions (Adv Clin Exp Med 2010, 19, 5, ). Key words: anti-decubitus underlay system, bed sheets, hydrophilic and hydrophobic fibers, impedance plethysmography, evaluation of local blood flow changes. * This work was supported financially by grant no 3 TO8E /2005 from Scientific Research Committee (KBN) for the years

2 638 E. Irzmańska et al. Streszczenie Wprowadzenie. W ostatnich latach coraz większą wagę przywiązuje się do projektowania materacy o zmiennej geometrii nacisku na skórę. Materac jest jednak jedną ze składowych podłoża przeciwodleżynowego, bezpośrednio bowiem ze skórą chorego styka się prześcieradło. Wydaje się, że właściwości tkaniny prześcieradłowej warstwy ścisłego kontaktu ze skórą związane z rodzajem użytych włókien, ich przestrzennym rozkładem w strukturze tkaniny oraz charakterem kontaktu z ciałem chorego punktowym lub ciągłym, mają istotne znaczenie w zapobieganiu uszkodzeniom skóry. Zastosowanie włókien o zróżnicowanej zdolności do sorpcji wody hydrofilowych, różniących się fizyczną mikrostrukturą i trwałością mechaniczną, oraz hydrofobowych o różnej budowie tworzywa i zróżnicowanej sprężystości, z usytuowaniem warstwy włókien hydrofobowych przy skórze osoby długotrwale unieruchomionej, może mieć wpływ na stabilizację dystrybucji ciepła i wilgoci w zaburzonym mechanizmie termoregulacji. Może również poprawić sprawność perfuzji naczyniowej w obszarach największego ryzyka wystąpienia odleżyn. Cel pracy. Ocena przydatności pletyzmografii impedancyjnej jako metody badania zmian miejscowego przepływu krwi w miejscu narażonym na powstanie odleżyn u chorych przewlekle unieruchomionych. Materiał i metody. Materiał badań stanowiło 47 osób. Badania wykonano w czterech grupach i dwóch podgrupach chorych. Podłoża przeciwodleżynowe zmodyfikowano, stosując odpowiednio w grupie 2 i podgrupie 2a prześcieradła z tkaniny gofrowanej, w grupie 3 i podgrupie 3a prześcieradła o splocie atłasowym. W grupie 4 zastosowano tradycyjne prześcieradła bawełniane o splocie płóciennym. Do oceny zmian miejscowego przepływu krwi w obszarze dużego ryzyka powstawania odleżyn u chorych długotrwale unieruchomionych z normalną i podwyższoną temperaturą ciała, zastosowano metodę pletyzmografii impedancyjnej. Pomiary zmian tkankowego przepływu krwi określono zgodnie z procedurą opisaną w instrukcji aparatu Niccomo niemieckiej firmy Medis, do oceny parametrów hemodynamicznych metodą kardiografii impedancyjnej z przystawką do pomiarów pletyzmograficznych. Spośród dostępnych wskaźników do oceny wybrano te, które są opisane przez krzywą pletyzmograficzną wykreślaną przez urządzenie dla badanego obszaru w systemie on-line. Wyniki i wnioski. Badania wykazały iż zastosowanie pletyzmografii impedancyjnej u chorych przewlekle unieruchomionych do oceny zmian miejscowego przepływu krwi pozwala na precyzyjne i powtarzalne monitorowanie wskaźników przepływu w badanym obszarze. Umożliwia także podejmowanie odpowiednich działań prewencyjnych dotyczących konstrukcji podłoża przeciwodleżynowego na wczesnym etapie formowania zmian skórnych u chorych, z różnych przyczyn pozostających przez dłuższy czas w łóżku w wymuszonej pozycji ciała (Adv Clin Exp Med 2010, 19, 5, ). Słowa kluczowe: podłoże przeciwodleżynowe, pościel, włókna hydrofobowe i hydrofilowe, pletyzmografia impedancyjna, ocena miejscowego przepływu krwi. Skin lesions observed in chronically immobilized persons both superficial ones, such as skin abrasions or erythemas (i.e., reactive hyperaemias) and internal ones, such as ischemia and/or tissue necrosis with progressive compression of local vascular systems lead to the formation of decubitus ulcers [1]. The common factor in skin lesions that are defined as decubitus ulcerations or compression ulcers is local tissue disorder that occurs after a period of chronic ischemia [2, 3]. Among the important external factors initiating decubitus ulcer formation are variations in average skin temperature and humidity, associated with thermoregulatory disruption in the organism as a result of long-term motor inactivity. The actual status of the disorders mentioned depends largely on the properties of the antidecubital underlay systems used [4, 5], because in chronically immobilized patients, the efficiency of heat distribution is closely associated not only with perspiration rate and external conditions, but also with the efficacy of the local vascular system, which is responsible for heat transfer from the muscles to the skin [6]. Therefore, evaluation of the local circulation status in areas at risk of decubitus ulcer development i.e., in the most protruding anatomical parts, for example, the sacral bone region is quite useful for the preliminary identification of processes conducive to decubitus ulcer development. In recent years, more and more attention has been paid to the design of variable-geometry mattresses that provide differentiated pressure on the skin. However, the mattress is only one component of an antidecubital underlay system, and it is the bed sheets that come into direct contact with the patient s skin. It therefore seems that the properties of the bed sheet fabric, resulting from the type of fibers used, their spatial layout in the fabric structure and the type of contact with the patient s body (point contact or continuous contact), are of significance in the prevention of skin lesions [7]. The use of fibers with varying degrees of water absorbency both hydrophilic and hydrophobic fibres, with different physical microstructures, mechanical durability and elasticity, with the hydrophobic layer situated directly under the skin of a person immobilized long-term may help to stabilize heat distribution and humidity when the thermoregulation mechanism is disrupted. It may also improve the efficacy of vascular perfusion in areas at the highest risk of decubitus ulceration [8]. The goal of this study was impedance plethysmography as a method of assessing local blood

3 Impedance Plethysmography in Chronically Immobilized Patients 639 flow in areas at risk of decubitus ulcer formation in chronically immobilized persons. Material and Methods The impedance plethysmography method was used to evaluate local blood flow changes in areas at high risk of decubitus ulcer development in chronically immobilized patients with normal and increased body temperature [9]. The study protocol was approved by the Bioethical Commission of the Medical University in Łódź (Approval No. RNN/134/03/KB). A Niccomo monitor (Medis, Germany), designed for the evaluation of hemodynamic parameters by the impedance cardiography method, was used with an adapter for plethysmographic measurements. Tissue blood flow changes were measured following the procedure described in the instruction manual. This monitor uses its own algorithm, an integral part of its firmware, during both cardiographic and plethysmographic examinations. The parameters selected for evaluation included those reflected by the plethysmographic curve drawn by the monitor for the area examined in an on-line examination mode. On this curve, an ascending (anacrotic) arm is visible, rising steeply almost vertically along with a descending (catacrotic) arm sloping gently from the wave crest downwards (Fig. 1a). Fairly often, a so-called dicrotic notch appears on the catacrotic arm with a subsequent small dicrotic wave, which occurs at the time of semilunar valve closure. Both the notch and the dicrotic wave may remain invisible on the curves from blood flow records in peripheral arteries. On the basis of the plethysmographic curve obtained, the following hemodynamic parameters were evaluated (see Fig. 1a, b): PAmpl (pulse wave amplitude) PSlope (systolic slope) CT (crest time) PT (propagation time), measured from the beginning of the R wave of the ECG to the beginning of the systolic wave slope in the plethysmogram. The examinations were performed in four groups and two subgroups of patients. The antidecubital underlay systems used were varied: Bed sheets of corrugated fabric were used in groups 2 and 2a, while in groups 3 and 3a, bed sheets with a satin weave were used. In group 4, traditional cotton bed sheets with a linen weave were used. Four groups of patients with normal body temperature were identified: group 1 consisted of 14 subjects (10 male, 4 female) with a mean age of 60 years, hospitalized at the time of the examination, without any major limitation to motor ability; group 2 was made up of 12 subjects (7 male and 5 female) with a mean age of 62 years, chronically immobilized after ischemic stroke; group 3 consisted of 10 patients (6 male, 4 female) with a mean age of 61 years, chronically immobilized after ischemic stroke; group 4 comprised 11 patients (7 male, 4 female) with a mean age of 60 years, chronically immobilized after ischemic stroke; In addition, two subgroups of patients with increased body temperature were identified: group 2a consisted of 4 patients (2 male, 2 female) with a mean age of 60 years, chronically immobilized after ischemic stroke, in a subfebrile state and with a mean a) b) Fig. 1. Impedance measurements of blood flow in the examined vascular area: (a) a schematic curve and (b) a realtime presentation Ryc. 1. Impedancyjny pomiar przepływu krwi w badanym obszarze naczyniowym; w ujęciu a) schematycznym krzywa i b) rzeczywistym

4 640 E. Irzmańska et al. Fig. 2. The layout of the measuring electrodes on the patient s body surface during an examination. The electrodes are attached in the vicinity of the caudal bone Ryc. 2. Układ elektrod pomiarowych na powierzchni ciała pacjenta w obrębie kości ogonowej podczas badania body temperature of 38.2 o C; group 3a was made up of 3 patients (1 male, 3 female) with a mean age of 59 years, chronically immobilized after ischemic stroke, with a mean body temperature of 37.9 o C. Taking into account the horizontal body position of the patients during hospitalization, the longest contact with decubitus-ulcer-inducing factors was in the region of the caudal bone, so a 4-electrode monitoring system was applied in that region. One of the two electrodes conducting high-frequency signals (black) was attached on the thigh, and the second one in the region of the distal thoracic vertebrae, while the measuring electrodes (yellow) were placed in the region of the caudal bone (Fig. 2). In groups 1 4, the examinations were performed once daily for seven days between 7:00 laminar blood flow przepływ krwi warstwowy (laminarny) turbulent blood/flow przepływ krwi burzliwy small skin blood vessels małe naczynie krwionośne skóry an incidental crease in a flat bed sheet structure przypadkowy załamek (zagniecenie) na płaskiej strukturze Fig. 3. An incidental crease in bed-sheet fabric results in blood vessel compression, suppressing blood flow in the subcutaneous layer, d fabric length, N compression force Ryc. 3. Przypadkowe zagniecenie tkaniny prześcieradłowej, powodując kompresję naczynia krwionośnego ograniczającą przepływ krwi w warstwie podskórnej, d długość tkaniny, N siła nacisku laminar blood flow przepływ krwi warstwowy (laminarny) small skin blood vessels małe naczynie krwionośne skóry uniform load distribution równomierny rozkład obciążeń periodic elastic convexities in corrugated fabric periodyczne, sprężyste wypukłości na tkaninie gofrowanej Fig. 4. The periodic elastic convexities in corrugated fabric result in adaptive blood vessel deformation, improving blood flow in the subcutaneous layer, d fabric length, N compression force Ryc. 4. Periodyczne sprężyste wypukłości tkaniny gofrowanej, powodujące adaptacyjną deformację naczynia krwionośnego, usprawniającą przepływ krwi w warstwie podskórnej, d długość tkaniny, N siły nacisku

5 Impedance Plethysmography in Chronically Immobilized Patients 641 and 8:00 in the morning, after at least seven hours of night rest in an air-conditioned hospital room with an air temperature of 21 C and relative humidity of 55%. In groups 2a and 3a, plethysmographic evaluations of local circulation were performed on the third day of the examinations, from 8:00 a.m to 8:00 p.m. with the same temperature and relative humidity conditions. All the examinations were done by the same person. Patients with major cardiovascular defects and/or disseminated atherosclerosis were excluded from the study. Statistical analysis of the results obtained was performed using the STATISTICA PL 5.1 software package, inputting the calculated median values of the studied variables and the standard deviations. Differences between the various study groups evaluated parameters were analysed by the ANO- VA test. In order to assess distribution normality, the distribution variance of the studied variables was evaluated by the Shapiro-Wilk test, and the homogeneity of variance by the F test. Then the analysis was continued for unpaired data by Student s t test. Differences were regarded as statistically significant when. Results Statistically significant differences in blood flow were observed at the region of high risk for decubitus ulcer development in the chronically immobilized patients using bed sheets made of the studied fabrics. The results of the study for patients with normal body temperature using bed sheets of corrugated fabric (group 2), satin fabric (group 3) and traditional (cotton) fabric (group 4) during seven days of hospitalization, considering four plethysmographic parameters (PAmpl, PSlope, CT and PT), vs. the same values in the group of hospitalized patients without any major limitations of motor ability (group 1), were as follows: Regarding the PAmpl parameter, a statistically significant difference was observed between the patients of group 1 and the patients of groups 2, 3 and 4. In groups 2 and 3, a statistically significant increase in the PAmpl parameter was noted on the fifth day of the study vs. group 4. During the subsequent two days of the study, significant differences were maintained between groups 2 & 3 and group 4 (). On the last day of the study, a statistically significant increase of the PAmpl parameter was observed in group 2 vs. group 3 () (Tables 1 and 2; Fig. 5). Regarding the PSlope parameter, a statistically significant difference was observed between the patients in group 1 and the patients in groups 2, 3 and 4. In groups 2 and 3, a statistically significant increase in the PSlope parameter was noted on the seventh (the last) day of the study vs. group 4 (). A statistically significant increase in the PSlope parameter was also observed in group 2 vs. group 3 (). (Tables 3 and 4; Fig. 6). With regard to the CT parameter, a statistically significant difference was observed between the patients in group 1 and the patients in groups 2, 3 and 4. In groups 2 and 3, a statistically significant decrease of the CT parameter was noted on the fifth day of the Table 1. PAmpl parameters [p.m] in groups 1, 2, 3 and 4 Tabela 1. Zestawienie wyników dla grup 1, 2, 3 i 4 badanych osób dotyczących parametru PAmpl [p.m] Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Table 2. Comparison of PAmpl parameters [p.m] in groups 1, 2, 3 and 4 Tabela 2. Porównanie uzyskanych wyników w grupach 1, 2, 3 i 4 badanych osób dotyczących parametru PAmpl [p.m] Gr1 Gr2 Gr1 Gr3 Gr1 Gr4 Gr2 Gr3 Gr2 Gr4 Gr3 Gr4

6 642 E. Irzmańska et al. pulse wave amplitude PAmpl [p.m] amplituda fali pulsu PAmpl [p.m] days (from 1st to 7th) group 1 healthy subjects (fully mobile)/osoba zdrowa (poruszająca się) group 2 patients using corrugated bed sheets/chorzy użytkujący prześcieradła z tkanin gofrowanych group 3 patients using satin bad sheets/chorzy użytkujący prześcieradła z tkanin atłasowych group 4 patients using traditional bed sheets/chorzy użytkujący tradycyjne prześcieradła Fig. 5. Correlations observed in PAmpl parameters [p.m] in groups 1 4 Ryc. 5. Graficzne przedstawienie obserwowanych zależności dla grup 1 4 badanych osób dotyczących parametru PAmpl [p.m] study vs. group 4. During the two subsequent days of the study, the significant differences between groups 2 & 3 and group 4 were maintained (). On the last day of the study, a statistically significant rise in the CT parameter was noted in Group 2 vs. group 3 (). (Tables 5 and 6; Fig. 7). As for the PT parameter, a statistically significant increase was noted in Group 4 on the sixth and seventh days of the study vs. groups 1, 2 and 3 (p < 0.05). However, no significant differences were noted between groups 2 and 3 with regard to the PT parameter (). (Tables 7 and 8; Fig. 8) The results for the patients with elevated body temperature during twelve hours of hospitalization, considering four plethysmographic parameters (PAmpl, PSlope, CT and PT) in patients with a mean body temperature of 38.2 C using bed sheets of corrugated fabric (group 2a) and those with a mean body temperature of 37.9 C using bed sheets of satin fabric (group 3a) were as follows: Regarding the PAmpl parameter, a statistically significant increase was noted in the seventh hour of the observation in group 3a vs. group p2a (). (Table 9; Fig. 9). Regarding the PSlope parameter, a statistically significant increase was noted in the seventh hour of the observation in group 3a vs. group 2a () (Table 10; Fig. 10). Table 3. PSlope parameters [p.m/s] in groups 1, 2, 3 and 4 Tabela 3. Zestawienie wyników dla grup 1, 2, 3 i 4 badanych osób dotyczących parametru PSlope [p.m/s] Group ± ± ± ± ± ± ± 1.10 Group ± ± ± ± ± ± ± 0.89 Group ± ± ± ± ± ± ± 0.36 Group ± ± ± ± ± ± ± 0.51 Table 4. Comparison of PSlope parameters [p.m/s] in groups 1, 2, 3 and 4 Tabela 4. Porównanie uzyskanych wyników w grupach 1, 2, 3 i 4 badanych osób dotyczących parametru PSlope [p.m/s] Gr1 Gr2 Gr1 Gr3 Gr1 Gr4 Gr2 Gr3 Gr2 Gr4 Gr3 Gr4

7 Impedance Plethysmography in Chronically Immobilized Patients 643 systolic slope of pulse wave PSlope [p.m/s] skurczowe nachylenie fali pulsu PSlope [p.m/s] days (from 1st to 7th) group 1 healthy subjects (fully mobile)/osoba zdrowa (poruszająca się) group 2 patients using corrugated bed sheets /chorzy użytkujący prześcieradła z tkanin gofrowanych group 3 patients using satin bad sheets/chorzy użytkujący prześcieradła z tkanin atłasowych group 4 patients using traditional bed sheets/chorzy użytkujący tradycyjne prześcieradła Fig. 6. Correlations observed in PSlope parameters [p.m/s] in groups 1 4 Ryc. 6. Graficzne przedstawienie obserwowanych zależności dla grup 1 4 badanych osób dotyczących parametru PSlope [p.m/s] With regard to the CT parameter, a statistically significant decrease was noted in the seventh hour of the observation in group 3a vs. group 2a () (Table 11; Fig. 11). No statistically significant changes were found in the PT parameter values during the 12-hour observation period in groups 2a and 3a (). (Table 12; Fig. 12). Discussion Experimental studies in recent years have overtly proven the plethysmographic curve record to be a useful method of blood flow evaluation [10], which prompted its use to monitor local perfusion disorders in chronically immobilized patients as well [11]. An analysis of the hemodynamic parameters studied indicates that local blood flow Table 5. CT parameters [ms] in groups 1, 2, 3 and 4 Tabela 5. Zestawienie wyników dla grup 1, 2, 3 i 4 badanych osób dotyczących parametru CT [ms] Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Table 6. Comparison of CT parameters [ms] in groups 1, 2, 3 and 4 Tabela 6. Porównanie uzyskanych wyników w grupach 1, 2, 3 i 4 badanych osób dotyczących parametru CT [ms] Gr1 Gr2 Gr1 Gr3 Gr1 Gr4 Gr2 Gr3 Gr2 Gr4 Gr3 Gr4

8 644 E. Irzmańska et al. crest time CT [ms] czas do szczytu fali CT [ms] days (from 1st to 7th) group 1 healthy subjects (fully mobile)/osoba zdrowa (poruszająca się) group 2 patients using corrugated bed sheets/chorzy użytkujący prześcieradła z tkanin gofrowanych group 3 patients using satin bad sheets/chorzy użytkujący prześcieradła z tkanin atłasowych group 4 patients using traditional bed sheets/chorzy użytkujący tradycyjne prześcieradła Fig. 7. Correlations observed in CT parameters [ms] in groups 1 4 Ryc. 7. Graficzne przedstawienie obserwowanych zależności dla grup 1 4 badanych osób dotyczących parametru CT [ms] disorders in tissues exposed to long-term external pressure [12] depend largely on the type of contact between the underlay systems and the skin. In the current study, in the findings for the groups of patients with normal body temperature using bed sheets manufactured of the fabrics studied, statistically significant differences were observed in blood flow changes in the regions at risk for skin lesions. A significant progression in local circulation disturbances was noted in the group of patients using generally-available linen weave cotton bed sheets (group 4). In that group of patients, perfusion disorders identified while observing the risk-affected region led to the observation period being limited to seven days for ethical reasons. On the fifth day, a significant decrease in the PAmpl parameter with CT time extension were observed, while the PSlope parameter significantly decreased on the seventh day. These results indicate a rapid rise in local circulation disorders in the area at high risk for decubitus ulceration. The result of propagation time analysis is another piece of evidence for the unfavorable character of the intravascular changes observed. On the sixth day of the Table 7. PT parameters [ms] in groups 1, 2, 3 and 4 Tabela 7. Zestawienie wyników dla grup 1, 2, 3 i 4 badanych osób dotyczących parametru PT [ms] Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Group ± ± ± ± ± ± ± Table 8. Comparison of PT parameters [ms] in groups 1, 2, 3 and 4 Tabela 8. Porównanie uzyskanych wyników w grupach 1, 2, 3 i 4 badanych osób dotyczących parametru PT [ms] Gr1 Gr2 Gr1 Gr3 Gr1 Gr4 Gr2 Gr3 Gr2 Gr4 Gr3 Gr4

9 Impedance Plethysmography in Chronically Immobilized Patients 645 propagation time PT [ms] czas propagacji PT [ms] days (from 1st to 7th) group 1 healthy subjects (fully mobile)/osoba zdrowa (poruszająca się) group 2 patients using corrugated bed sheets/chorzy użytkujący prześcieradła z tkanin gofrowanych group 3 patients using satin bad sheets/chorzy użytkujący prześcieradła z tkanin atłasowych group 4 patients using traditional bed sheets/ chorzy użytkujący tradycyjne prześcieradła Fig. 8. Correlations observed in PT parameters [ms] in groups 1 4 Ryc. 8. Graficzne przedstawienie obserwowanych zależności dla grup 1 4 badanych osób dotyczących parametru PT [ms] study, the propagation time increased significantly in group 4 as compared to the other groups of patients in the study. This behaviour of the PT parameter is associated with significant blood flow limitation. On the other hand, in the patients using bed sheets made of specially designed fabrics (groups 2 and 3), key changes were recorded on approximately the fifth day of the study. At that time, in both of these groups, a significant increase in the PAmpl parameter was observed, with simultaneous CT reduction; and a significant increase in the PSlope parameter occurred on the seventh day of the study. This trend in the changes in the plethysmographic parameters indicates progress towards blood flow normalization, following a period of insignificant disruption of hemodynamic balance observed in the studied area on the second day of the study. It should be emphasized that on the last day of the study, a particularly significant increase in the Pampl and PSlope parameter values was noted, along with CT reduction, in the group of patients, using bed sheets of satin-weave fabric. It should also be noted that during the entire observation period, the mean propagation time did not change significantly in either group 2 or group 3. There was no significant difference noted between the PT parameter in either of these groups of patients (using corrugated-fabric bed sheets or bed sheets of satin-weave fabric) and the PT parameter of the subjects with full motor ability, i.e., not bedridden. That fact confirms the effective protection of local circulation provided by bed sheets made of the fabrics studied, particularly the corrugated fabric. Considering the significant differences in heat and humidity transfer found in model studies of the fabrics used at temperature of 39.5 C, additional clinical studies were undertaken in two groups of patients with elevated body temperatures [13]. It appears from the model studies that, in fever, humidity transfer is more effective with corrugated bed sheets, while heat transfer is improved by bed sheets with a satin weave. Twelve-hour observations demonstrated significantly increased values in the PAmpl and PSlope hemodynamic parameters along with CT reduction in the seventh hour of febrile status in the group of patients using satin-weave bed sheets as compared with the group using corrugated-fabric bed sheets. At the same time, no significant changes were observed in the PT parameter. Analysis of the plethysmographic parameters indicates blood flow normalization in the studied area in the patients using satin bed sheets, thus confirming the usefulness and suitability of satin fabrics for effective distribution of accumulated heat when the organism is in a febrile state. A comparison of the results of previous clinical studies may support the conclusion that thermoregulation disorders that lead to elevated body temperatures (the febrile state) also impair the microclimate of the skin of chronically immobilized persons, accelerating the occurrence of conditions conducive to decubitus formations on the skin. This is consistent with the significant increase in the values of the Pampl, PSlope and CT hemodynamic parameters in the groups of patients using bed sheets as compared with subjects with full motor ability. Local blood flow disorders in the groups of patients in the study occurred at the very beginning of

10 646 E. Irzmańska et al. Table 9. PAmpl parameters [p.m] in groups 2a and 3a Tabela 9. Zestawienie wyników dla grup 2a i 3a badanych osób dotyczących parametru PAmpl [p.m] 1st hour 2nd hour 3rd hour 4th hour 5th hour 6th hour 7th hour 8th hour 9th hour 10th hour 11th hour 12th hour Gr 2a ± ± ± ± ± ± ± ± ± ± ± ± Gr 3a ± ± ± ± ± ± ± ± ± ± ± ± p pulse wave amplitude PAmpl [p.m] amplituda fali pulsu PAmpl [p.m] hours (from 1st to 12th) group 2a patients using corrugated bed sheets/chorzy użytkujący prześcieradła z tkanin gofrowanych group 3a patients using satin bad sheets/chorzy użytkujący prześcieradła z tkanin atłasowych Fig. 9. Correlations observed in PT parameters [ms] in groups 2a and 3a Ryc. 9. Graficzne przedstawienie obserwowanych zależności dla grup 2a i 3a badanych osób dotyczących parametru PAmpl [p.m]

11 Impedance Plethysmography in Chronically Immobilized Patients 647 Table 10. PSlope parameters [p.m/s] in groups 2a and 3a Tabela 10. Zestawienie wyników dla grup 2 i 3 badanych osób dotyczących parametru PSlope [p.m/s] 1st hour 2nd hour 3rd hour 4th hour 5th hour 6th hour 7th hour 8th hour 9th hour 10th hour 11th hour 12th hour Gr 2a 8.79 ± ± ± ± ± ± ± ± ± ± ± ± 0.15 Gr 3a 8.67 ± ± ± ± ± ± ± ± ± ± ± ± 0.12 p systolic slope of pulse wave PSlope [p.m/s] skurczowe nachylenie fali pulsu PSlope [p.m/s] hours (from 1st to 12th) group 2a patients using corrugated bed sheets/chorzy użytkujący prześcieradła z tkanin gofrowanych group 3a patients using satin bad sheets/chorzy użytkujący prześcieradła z tkanin atłasowych Fig. 10. Graphic presentation of the correlations observed in PSlope parameters [p.m/s] in groups 2a and 3a Ryc. 10. Graficzne przedstawienie obserwowanych zależności dla grup 2a i 3a badanych osób dotyczących parametru PSlope [p.m/s]

12 648 E. Irzmańska et al. Table 11. CT parameters [ms] in groups 2a and 3a Tabela 11. Zestawienie wyników dla grup 2a i 3a badanych osób dotyczących parametru CT [ms] 1st hour 2nd hour 3rd hour 4th hour 5th hour 6th hour 7th hour 8th hour 9th hour 10th hour 11th hour 12th hour Gr 2a ± ± ± ± ± ± ± ± ± ± ± ± 5.50 Gr 3a ± ± ± ± ± ± ± ± ± ± ± ± 2.08 p crest time CT [ms] czas do szczytu fali CT [ms] hours (from 1st to 12th) group 2a patients using corrugated bed sheets/chorzy użytkujący prześcieradła z tkanin gofrowanych group 3a patients using satin bad sheets/chorzy użytkujący prześcieradła z tkanin atłasowych Fig. 11. Correlations observed in CT parameters [ms] in groups 2a and 3a Ryc. 11. Graficzne przedstawienie obserwowanych zależności dla grup 2a i 3a badanych osób dotyczących parametru CT [ms]

13 Impedance Plethysmography in Chronically Immobilized Patients 649 Table 12. PT parameters [ms] in groups 2a and 3a Tabela 12. Zestawienie wyników dla grup 2a i 3a badanych osób dotyczących parametru PT [ms] 1st hour 2nd hour 3rd hour 4th hour 5th hour 6th hour 7th hour 8th hour 9th hour 10th hour 11th hour 12th hour Gr 2a ± ± ± ± ± ± ± ± ± ± ± ± 9.57 Gr 3a ± ± ± ± ± ± ± ± ± ± ± ± 7.64 p propagation time PT [ms] czas propagacji PT [ms] hours (from 1st to 12th) group 2a patients using corrugated bed sheets/chorzy użytkujący prześcieradła z tkanin gofrowanych group 3a patients using satin bad sheets/chorzy użytkujący prześcieradła z tkanin atłasowych Fig. 12. Correlations observed in PT parameters [ms] in groups 2a and 3a Ryc. 12. Graficzne przedstawienie obserwowanych zależności dla grup 2a i 3a badanych osób dotyczących parametru PT [ms]

14 650 E. Irzmańska et al. immobilization (on the second day). The results of the study suggest that local blood flow disorders observed early in the immobilization, and the accompanying elevation in body temperature and skin humidity, intensify skin lesion processes. Asher [14] expresses a similar opinion, studying physiological indicators that manifest in the early period of immobility; according to that author, it is associated with limited muscular tissue activity, as well as with progressive blood rheological disorders. Prior clinical studies confirm the practical suitability of specially designed fabrics, regardless of the nature of their contact with human skin continuous contact (fabric with a satin weave) or point contact (fabric that is corrugated during the weaving process). According to Van Langenhove, the main causes of decubitus ulcer formation in chronically immobilized subjects include incidental creases and folds in bed sheet fabrics [15]. An incidental fabric deformation can cause considerable compression of vessels in the subcutaneous layer, changing blood flow from laminar to turbulent. The compression of vessels radically suppressing the blood flow in the vessel, reduces the metabolism of neighboring tissues and increases the changes associated with oxygen deficiency, which is conducive to the formation of decubitus ulceration. However, when the fabric structure has programmed, regular convex elements (corrugated fabric), the physiological reaction of the local vascular system seems to be more complex. Fabric with properly designed surface geometry and appropriate elasticity in its convex fragments, causing adaptive deformation of vessels in the subcutaneous layer, does not limit blood flow but, paradoxically, improves it [16]. It seems that the main role in this mechanism belongs to the density of the convex elements of corrugated fabric, which support laminar blood flow stability in vessels under uniform compression [17]. On this basis it may be concluded that designed point contact with the skin is especially favorable in terms of blood flow dynamics in the small vessels of the subcutaneous layer (Figs 3 and 4). In conclusion, the authors wish to emphasize that using impedance plethysmography to evaluate local blood flow changes in chronically immobilized patients is a useful method for precise and repeatable monitoring of flow parameters in the area under examination. It also serves to prompt appropriate prevention activities and the preparation of anti-decubitus underlay structures at the early stages of skin lesion formation in patients who are bedridden long-term with restricted body positions. References [1] Seiler WO, Stähelin HB: Decubitus ulcers in geriatrics pathogenesis, prevention and therapy. Ther Umsch 1991, 48, 5, [2] Kosiak M: Etiology and pathology of ischemic ulcers. Arch Phys Med Rehabil 1959, 40, [3] McInnes E, Bell-Syer SE, Dumville JC, Legood R, Cullum NA: Support surfaces for pressure ulcer prevention. Cochrane Database Syst Rev 2008, 8, 4, CD [4] Cochran G, Palmieri V: Development of test methods for evaluation of wheelchair cushions. Bull Prosthet Res 1980, 17, [5] Stewart S, Palmieri V, Cochran G: Wheelchair cushion effect on skin temperature, heat and relative humidity. Arch Phys Med Rehabil 1980, 61, [6] Wywiałowski EF: Tissue perfusion as a key underlying concept of pressure ulcer development and treatment. J Vasc Nurs 1999, 17, [7] Cullum N, Deeks J, Sheldon TA, Song F, Fletcher AW: Beds, mattresses and cushions for pressure sore prevention and treatment. Cochrane Database Syst Rev 2004, 3, CD [8] Nicholson GP, Scales JT, Clark RP, Calcina-Goff MLD: A method for determining the heat transfer and water vapour permeability of patient support systems. Med Eng Phys 1999, 21, [9] Siebert J, Poliński A: Badania modelowe zastosowania pletyzmografii impedancyjnej do badania przepływu krwi w kończynach. Folia Cardiol 1999, 6, [10] Siebert J, Poliński A, Rogowski J: Pletyzmografia impedancyjna ocena całkowitego przepływu krwi w przedramieniu. Folia Cardiol 1999, 6, [11] Kozera G, Miszkowska E, Bieniaszewski L, Nyka W: Zakrzepica żył głębokich u chorych na udar mózgu. Neurol Neuroch Pol 2007, 41, 3, [12] Mayrovitz HN, Sims N: Biophysical effects of water and synthetic urine on skin. Adv Skin Wound Care 2001, 14, [13] Irzmańska E, Lipp-Symonowicz B, Kujawa J, Irzmański R: Textiles preventing skin damages. Fibr Tex East Eur, 2009, in press. [14] Bruck K: Thermal balance and the regulation of body temperature. Hum Physiol 1989, [15] Van Langenhove L: Formation of creases in bedsheets a cause of decubitus. I International Conference Medical Textiles, Bolton [16] Sulzberger M, Cortese TA, Fishman L, Wiley HS: Studies on blister produced by friction. J Invest Dermatol 1996, 47, [17] Kosiak M: Prevention and rehabilitation of pressure ulcers. Decubitus 1999, 4, 2 4.

15 Impedance Plethysmography in Chronically Immobilized Patients 651 Address for correspondence: Magdalena Charłusz Laboratory of Ergonomics and Exercise Physiology Medical University of Lodz Hallera Łódź Poland Tel.: charlusz@o2.pl Conflict of interest: None declared Received: Revised: Accepted: