Evaluation of the impression technique by measuring interstitial oedema in rat testis

Tissue Tonometry Before and After Liposuction of Arm Lymphedema Following Breast Cancer

BACKGROUND

Arm lymphedema is a common complication after breast cancer treatment. Different conservative and surgical treatments have been used to reduce the arm swelling, but most have failed as chronic edema eventually transforms from a state of accumulated lymph fluid into increased deposition of subcutaneous fat, i.e. a non-pitting lymphedema.

OBJECTIVE

To evaluate changes in tissue tonicity with an electronic tissue tonometer before and after liposuction. To validate the tonometer, outcome of surgery, and aspirate content. If tonometry can discriminate between "soft" and "hard" edema/swelling, it can be used to differentiate these types, as treatment differs.

SUBJECTS AND METHODS

Twenty women with non-pitting unilateral postmastectomy arm lymphedema were operated on. The following measurements were performed: Tissue tonicity with a tonometer, its sensitivity on five different foam-polyethers by ten subjects, arm volumes, and adipose tissue aspirate content.

RESULTS

Tissue tonicity values showed that the upper lymphedematous arm was harder than the normal one. After surgery it became softer, and at one year it was as soft as the normal arm. Polyether tonometries could clearly differentiate the various properties. A sample of three measurements was as good as ten. Horizontal vs. vertical measurements did not differ in the high-density polyethers. Complete reduction of the lymphedema was achieved. Adipose tissue content of the aspirate was 89%.

CONCLUSION

The tonometer could register postoperative changes in tissue tonicity in the upper arm, but not in the forearm, which also showed significantly higher absolute values. Probably this is caused by the high adipose tissue content with little or no free fluid, thus resembling the normal arm in tonicity. Possibly also the thinner subcutaneous tissue in the forearm plays a role. Tonometry can differentiate if a lymphedematous arm that is softer or harder than the normal one. A harder swelling is dominated by adipose tissue and can be treated with liposuction, while the softer one is treated conservatively.

Non-invasive assessment of fluid volume status in the interstitium after haemodialysis

During dialysis excess fluid is removed from uraemic patients. The excess fluid is mainly located in the skin and subcutaneous tissues. In this study we wished, with two noninvasive techniques, the IM (impression method) and BIA (bioimpedance analysis), to study what mechanical (IM) and electrical cellular membrane (BIA) effects the fluid withdrawal has on these tissues. The IM measures the resistive force of the tissues when mechanically compressed. From the force curve two parameters are calculated, the F(0), indicative of interstitial tissue pressure and the FT corresponding to the translocation of tissue fluid (interstitial movable water). The BIA phase angle shift (phi), i.e. geometrical angular transformation of the ratio between reactance and resistance, which has been associated with cellular membrane function, was used as a measurement of electrical cellular membrane effects. Twenty patients were studied before and after haemodialysis measuring the F(0), FT and phi. Theresults showed that the patients lost a median of 3.7 kg during the haemodialysis. F(0) increased until after dialysis, but did not reach significant values, whereas FT increased significantly after dialysis, p < 0.001, as compared with before. After a peak at one hour postdialysis the FT value returned to predialysis values at four hours after termination of dialysis. Also phi increased from before to after dialysis, p < 0.001, but already after one hour it returned to predialysis values. It is common knowledge that dialysis alters the dynamics of fluid in the interstitium of the skin and subcutis. We conclude that the impression method is sensitive enough to detect and chronicle these changes. Furthermore, with the BIA, (phase angle) signs of changes in the electrical properties of the tissues, possibly reflecting cellular membrane function, could be detected.

Non-invasive assessment of intercompartmental fluid shifts in burn victims

Two non-invasive methods (the bioimpedance technique, BIA, and the impression method, IM) were studied, to find out whether they are sensitive enough to detect and chronicle the development of the oedema and fluid resuscitation effects (Parkland formula) that occur secondary to a major burn. Ten patients with a total burned body surface area (TBSA) of more than 10% were included in this prospective study. Total body water (TBW), as measured by the resistance (BIA) or F(0) variable (IM), reached a maximum on day 2. The tissue fluid translocation (INT) variable (IM) followed a different course, increasing slowly to reach a maximum on day 6, when it was 40% higher than the 12 h value. TBW and the interstitial translocatable fluid were still increased 1 week post-burn. The non-invasive measurements of TBW (resistance by BIA and F(0) by IM) reflected the anticipated changes in TBW. The phase angle (BIA) indicative of cellular membrane effects of burn and sepsis had its lowest values at day 1.5, and stayed significantly low until day 4. Interestingly, the phase angle was lowest in the two cases that died subsequently. The different time course of the INT value (IM), which reflected the translocatable interstitial fluid volume in skin, may be the result of resuscitation fluid remaining in this compartment, due to the excess sodium content together with a possible change in tissue compliance secondary to the early total water peak on day 2.

Impression technique for the assessment of oedema: comparison with a new tactile sensor that measures physical properties of tissue

To measure tissue oedema, the impression technique and a new tactile sensor technique are compared and evaluated in a silicone rubber model and in an in vivo rat testis model. The principles of the two techniques differ in that the impression technique evaluates interstitial fluid flow FT and peak force F(O) when tissue is compressed, whereas the tactile sensor evaluates the hardness/softness or change in resonance frequency delta f when a vibrating rod is attached to tissue. Both techniques can detect changes in silicone hardness/softness or in hormone-induced changes of testis interstitial fluid. Although both F(O) and FT are significantly correlated to delta f in the experiments, it is concluded that F(O) is the most promising impression parameter to give valuable information about the hardness of living tissue as compared with delta f. The comparison indicates that the impression technique is the most easy to interpret, non-invasive tool to assess tissue oedema so far developed.

Human postburn oedema measured with the impression method

The course of tissue swelling in human non-injured skin after burn injury was investigated with a non-invasive impression method that measures force and tissue fluid translocation during mechanical compression of the skin. Time-dependent changes in the fluid translocation and the interstitial-pressure related to impression force were measured on 11 occasions, during 3 weeks, in seven patients postburn. A mathematical model was fitted to the impression force curves and the parameters of the model depicted the time-dependent compartmental fluid shift in the postburn generalized oedema. Tissue fluid translocation increased significantly (P < 0.05) up to a maximum value after 6 days postburn and declined thereafter. This indicated a continuous increase in the generalized postburn oedema for the first 6 days postburn. Impression force at 3 weeks postburn was significantly lower (P < 0.001) as compared with the half-day postburn value, indicating an increased tissue pressure during the first days postburn. Parameter analysis indicated a flux of water-like fluid from the vasculature to the interstitial space during the first 6 days postburn. The spread of the values registered between different measurement sites was, however, large.

The time-response and magnitude of hCG-induced vascular changes are different in scrotal and abdominal testes

Adult unilaterally cryptorchid rats were injected with 50 IU human chorionic gonadotrophin (hCG). At 4, 8, 24 and 72 h after treatment, testicular vascular permeability was studied by injecting colloidal carbon intravenously. The number of blood vessel profiles labelled with carbon was increased by hCG in both types of testes, but the response was more sustained in abdominal than in scrotal testes. The number of polymorphonuclear leucocytes (PMNs) accumulating in testicular blood vessels and migrating into the interstitial space in response to hCG treatment was also measured. The volume density of intravascular and interstitial PMNs was increased in both types of testes but the peak response was larger in scrotal than in abdominal testes. PMN accumulation and vascular leakage were apparently correlated in the scrotal but not in the abdominal testes. Testicular interstitial fluid (IF) was collected from intact and unilaterally cryptorchid adult rats. The IF was diluted with sterile buffer and injected intracutaneously in test animals. The vascular permeability response was assessed by measuring the leakage of Evans blue into the injection sites. IF from scrotal and abdominal testes increased vascular permeability in the skin. The response was rapid and transient. IF collected from rats given hCG 24 h earlier did not increase vascular permeability. The vascular permeability response to IF was reduced slightly in neutrophil-depleted animals. The inflammation mediator present in IF cannot explain the kinetics and magnitude of the hCG-induced changes in vascular permeability in intact or unilaterally cryptorchid rats.