Wireless sensors for continuous, multimodal measurements at the skin interface with lower limb prostheses

Precise form-fitting of prosthetic sockets is important for the comfort and well-being of persons with limb amputations. Capabilities for continuous monitoring of pressure and temperature at the skin-prosthesis interface can be valuable in the fitting process and in monitoring for the development of dangerous regions of increased pressure and temperature as limb volume changes during daily activities. Conventional pressure transducers and temperature sensors cannot provide comfortable, irritation-free measurements because of their relatively rigid construction and requirements for wired interfaces to external data acquisition hardware. Here, we introduce a millimeter-scale pressure sensor that adopts a soft, three-dimensional design that integrates into a thin, flexible battery-free, wireless platform with a built-in temperature sensor to allow operation in a noninvasive, imperceptible fashion directly at the skin-prosthesis interface. The sensor system mounts on the surface of the skin of the residual limb, in single or multiple locations of interest. A wireless reader module attached to the outside of the prosthetic socket wirelessly provides power to the sensor and wirelessly receives data from it, for continuous long-range transmission to a standard consumer electronic device such as a smartphone or tablet computer. Characterization of both the sensor and the system, together with theoretical analysis of the key responses, illustrates linear, accurate responses and the ability to address the entire range of relevant pressures and to capture skin temperature accurately, both in a continuous mode. Clinical application in two prosthesis users demonstrates the functionality and feasibility of this soft, wireless system.

Skin-interfaced biosensors for advanced wireless physiological monitoring in neonatal and pediatric intensive-care units

Standard of care management in neonatal and pediatric intensive care units (NICUs and PICUs) involve continuous monitoring of vital signs with hard-wired devices that adhere to the skin and, in certain instances, include catheter-loaded pressure sensors that insert into the arteries. These protocols involve risks for complications and impediments to clinical care and skin-to-skin contact between parent and child. Here we present a wireless, non-invasive technology that not only offers measurement equivalency to these management standards but also supports a range of important additional features (without limitations or shortcomings of existing approaches), supported by data from pilot clinical studies in the neonatal intensive care unit (NICU) and pediatric ICU (PICU). The combined capabilities of these platforms extend beyond clinical quality measurements of vital signs (heart rate, respiration rate, temperature and blood oxygenation) to include novel modalities for (1) tracking movements and changes in body orientation, (2) quantifying the physiological benefits of skin-to-skin care (e.g. Kangaroo care) for neonates, (3) capturing acoustic signatures of cardiac activity by directly measuring mechanical vibrations generated through the skin on the chest, (4) recording vocal biomarkers associated with tonality and temporal characteristics of crying impervious to confounding ambient noise, and (5) monitoring a reliable surrogate for systolic blood pressure. The results have potential to significantly enhance the quality of neonatal and pediatric critical care.

Binodal, wireless epidermal electronic systems with in-sensor analytics for neonatal intensive care

Existing vital signmonitoring systems in the neonatal intensive care unit (NICU) requiremultiple wires connected to rigid sensors with strongly adherent interfaces to the skin.We introduce a pair of ultrathin, soft, skin-like electronic devices whose coordinated, wireless operation reproduces the functionality of these traditional technologies but bypasses their intrinsic limitations.The enabling advances in engineering science include designs that support wireless, battery-free operation; real-time, in-sensor data analytics; time-synchronized, continuous data streaming; soft mechanics and gentle adhesive interfaces to the skin; and compatibility with visual inspection and with medical imaging techniques used in the NICU. Preliminary studies on neonates admitted to operating NICUs demonstrate performance comparable to the most advanced clinical-standard monitoring systems.

Glucagon-like peptide-2 stimulates gut mucosal growth and immune response in burned rats

Major burn trauma often leads to reduced gut barrier function, immunosuppression, and increased bacterial translocation. We hypothesized that treatments that maintain normal gut after burn trauma will also reduce immunosuppression and bacterial translocation. Recent studies suggest that treatment with glucagon-like peptide-2 (GLP-2), which is synthesized in the intestine and released after food intake, elicits mucosal hyperplasia in the small intestine of rodents and prevents parenteral nutrition-induced gut hypoplasia. Therefore, we determined whether GLP-2 would prevent loss of gut integrity after major burn trauma. Osmotic minipumps were implanted into the peritoneum of 22 adult, male, Sprague-Dawley rats to infuse saline (10 microl/hr; n = 14) or GLP-2 (1 microg/hr; n = 8). On the next day 8 saline-infused and 8 GLP-2-infused rats were subjected to a 25 sec duration 30% BSA open flame burn, with the remaining rats serving as sham-burn controls. Five days after burn, all rats were killed. Gut protein was assessed, and immunosuppression was estimated by the mitogenic response of cultured splenocytes to phytohemagglutinin, pokeweed, and concanavalin A. Bacterial translocation was determined by culturing the mesenteric lymph nodes. Although protein content was significantly decreased in the ileum of burned rats treated with saline, the burned rats treated with GLP-2 exhibited significant increases in protein levels in duodenum, jejunum. and ileum. Colon protein was not affected by GLP-2 infusion. Saline-treated burned rats also exhibited immunosuppression, as suggested by significantly decreased responses to each of the mitogens. Infusion of GLP-2 normalized the response by the burned rats to each of the mitogens. Lymph nodes taken from sham rats exhibited no colony forming units, whereas in both of the burn groups, 50% of the cultures were positive. However, more aggressive colonization may have occurred in the saline-infused burned rats as compared with the GLP-2-infused burned rats (81 +/- 63 vs 3 +/- 2 colony forming units). These results suggest that GLP-2 may stimulate gut mucosa and reduce immunosuppression in burned rats. However, there does not seem to be a statistically significant positive effect of GLP-2 on bacterial translocation. Thus, improving small intestine mucosa may increase immunity while being ineffective against bacterial translocation.

Burn injury stimulates multiple proteolytic pathways in skeletal muscle, including the ubiquitin-energy-dependent pathway

BACKGROUND

Burn injury is associated with increased muscle protein breakdown. However, the role of different intracellular proteolytic pathways in burn-induced muscle proteolysis is not known.

STUDY DESIGN

A 30 percent total body surface area burn injury was inflicted on rats. Total and myofibrillar proteolysis was determined in incubated extensor digitorum longus muscles as release of tyrosine and 3-methylhistidine, respectively. Lysosomal proteolysis was assessed by using the lysosomotropic agents leupeptin and methylamine. Calcium-dependent proteolysis was determined by incubating muscles in the absence or presence of calcium or by blocking the calcium-dependent proteases calpain I and II. Energy-dependent proteolysis was determined in muscles depleted of adenosine triphosphate (ATP) by 2-deoxyglucose and 2,4-dinitrophenol. Muscle ubiquitin messenger RNA (mRNA) was determined by Northern blot analysis to assess ATP-ubiquitin-dependent proteolysis.

RESULTS

Calcium-dependent total protein breakdown was stimulated in muscles from burned rats. However, the sensitivity to calcium in vitro was not increased after burn. The lysosomal and energy-dependent components of total protein breakdown were doubled in muscles from burned rats and the energy-dependent myofibrillar protein breakdown was increased almost seven-fold. Ubiquitin mRNA was increased in muscles from burned rats.

CONCLUSIONS

Burn injury stimulates multiple proteolytic pathways in skeletal muscle. The ubiquitin-energy-dependent pathway may be particularly important for the breakdown of myofibrillar proteins.

Influence of burn injury on protein metabolism in different types of skeletal muscle and the role of glucocorticoids

BACKGROUND

Negative nitrogen balance after burn injury mainly indicates muscle catabolism, but the exact influence of burn on protein synthesis and breakdown in different types of skeletal muscle and the role of glucocorticoids in this metabolic response are unknown.

STUDY DESIGN

A 30 percent body surface area flame burn was inflicted on rats. Protein turnover rates were measured in vitro in the white fast-twitch extensor digitorum longus (EDL) muscle and the red slow-twitch soleus muscle. To test the role of glucocorticoids, groups of rats were treated with the glucocorticoid receptor antagonist RU 38486 or vehicle.

RESULTS

Burns resulted in reduced protein synthesis and stimulated protein breakdown, in particular myofibrillar protein breakdown, and the changes were substantially more pronounced in the EDL than in the soleus muscle. A burn-induced increase in muscle proteolysis was abolished by treatment with RU 38486, whereas the reduced protein synthesis was not affected by the glucocorticoid receptor antagonist.

CONCLUSIONS

The results suggest that the white fast-twitch muscle is more sensitive to the effects of burn injury than the red slow-twitch muscle. Burn-induced muscle proteolysis may be mediated, at least in part, by glucocorticoids, whereas protein synthesis is probably regulated by other mechanisms.

Detrimental effect of nitric oxide synthase inhibition during endotoxemia may be caused by high levels of tumor necrosis factor and interleukin-6

BACKGROUND

Nitric oxide (NO) production increases during sepsis and endotoxemia. Inhibition of NO synthase has been suggested as a therapeutic modality in sepsis and endotoxemia, but in recent reports NO synthase inhibition increased mortality rate. The mechanism of this phenomenon is not known. Other studies have shown that high levels of tumor necrosis factor (TNF) and interleukin-6 (IL-6) contribute to death during sepsis and endotoxemia. We tested the effect of NO synthase inhibition on survival in endotoxemic rats and hypothesized that inhibition of NO synthase during endotoxemia increases circulating levels of TNF and IL-6.

METHODS

Rats were treated with subcutaneous injection of saline solution or 100 mg/kg of the NO synthase inhibitor N-nitro-L-arginine 1 hour before intravenous injection of endotoxin (15 mg/kg) or saline solution. Survival was followed for 24 hours. Plasma nitrite-nitrate (NO2/NO3), TNF, and IL-6 levels were determined at intervals.

RESULTS

Endotoxin caused a significant increase in levels of plasma NO2-/NO3-, TNF, and IL-6 and a 33% mortality rate. Pretreatment with N-nitro-L-arginine increased mortality rate to 74%, decreased NO2/NO3, and substantially increased TNF and IL-6 levels.

CONCLUSIONS

Inhibition of NO synthase increases mortality rate during endotoxemia. The detrimental effect of NO synthase inhibition during endotoxemia may be caused by excessive production of TNF and IL-6.

Diclofenac

Diclofenac is the newest NSAID to be introduced to the United States. Extensive worldwide clinical studies with diclofenac have demonstrated its efficacy in the treatment of rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis. Its overall safety and efficacy is comparable to other available NSAIDs. The potential advantage of diclofenac is its short serum half-life but long synovial fluid concentration which enables twice daily dosing.

Superoxide dismutase in rats with sepsis. Effect on survival rate and amino acid transport

In a recent study, administration of the free radical scavenger superoxide dismutase (SOD) improved survival in rats with sepsis when administered two hours before induction of sepsis. The present study was designed to determine whether free radical-induced membrane damage is involved in the pathogenesis of decreased muscle amino acid uptake, noted in sepsis. Additionally, the effect on survival rate of SOD given after the onset of sepsis was studied. Sepsis was induced by cecal ligation and puncture in rats. Amino acid transport in incubated soleus muscles was studied using tritiated alpha-aminoisobutyric acid. Amino acid uptake was significantly reduced in muscle from rats with sepsis. Administration of SOD before induction of sepsis or added in vitro to incubated muscles with sepsis had no effect on alpha-aminoisobutyric acid uptake. Survival rate was not increased when SOD was given two hours after cecal ligation and puncture. The results suggest that free radical-induced membrane damage is not the mechanism of inhibited muscle amino acid transport in sepsis. Since survival was not improved by SOD administered after induction of sepsis, the role of the enzyme in the treatment of sepsis may be questioned.

Evaluation of serum proteins in relation to body nitrogen in tumor-bearing rats

Assessment of visceral and somatic protein stores by serum proteins in surgical oncology patients has been difficult to interpret. Tumor-bearing (methylcholanthrene sarcoma) (TB) and nontumor-bearing (NTB) Fischer 344 rats were infused with a total parenteral nutrition solution at either 25, 100, or 175% of an infusion rate that provided sufficient nutrients for normal rat growth: On the fifth day after diet initiation, the rats were exsanguinated, decapitated, eviscerated, and skinned. Serum was analyzed for transferrin (TF), complement C3, albumin (ALB), retinol-binding protein (RBP), and transthyretin (TTR). Carcass (CAR) and organ (VIS) nitrogens were determined by the Kjeldahl method. TTR, TF, and RBP correlated significantly with TB and NTB VIS nitrogen and TB CAR nitrogen. The correlation of NTB VIS nitrogen with TTR, TF, and RBP (r range = 0.70-0.85, P less than 0.001) was higher than for TB rats (r range = 0.53-0.57, P less than 0.005). The correlation of TB carcass nitrogen (r range = 0.47-0.51, P less than 0.01) with TTR, TF, and RBP was higher than for NTB carcass nitrogen which was not significant (r range = 0.25-0.37, P less than 0.57). These data indicate that TTR, TF, and RBP do correlate with components of body nitrogen mass, but factors other than nutrition may influence their metabolism in the TB host.

Reduced muscle amino acid uptake in sepsis and the effects in vitro of septic plasma and interleukin-1

Inhibited amino acid transport in skeletal muscle during sepsis has been demonstrated previously. In the present study we investigated the effects in vitro of plasma from septic animals or fractions of septic plasma that contain solutes with a molecular weight less than 30,000 daltons or less than 2000 to 3000 daltons on amino acid transport in incubated rat soleus (SOL) muscles. The influence of interleukin-1 (IL-1), prostaglandin E2 (PEG2), and the "catabolic" hormones corticosterone, glucagon, and epinephrine on muscle amino acid uptake was also investigated. Amino acid transport was studied with 3H-alpha-aminoisobutyric acid (AIB). Whole-septic plasma and the two low molecular-weight fractions of the septic plasma reduced muscle amino acid uptake by about 20%. IL-1 or PGE2 did not affect amino acid transport. When the catabolic hormones were added individually to incubated SOL muscles, no changes in AIB uptake were noticed. When glucagon or epinephrine was added in combination with corticosterone or when all three hormones were added together, amino acid transport was reduced by 10% to 15%. The results suggest that inhibited muscle amino acid uptake in sepsis is caused by a circulating factor(s) with a molecular weight less than 2000 to 3000 daltons. A synergistic action among the catabolic hormones may be one important factor for reduced muscle amino acid transport in sepsis.