In vivo stratum corneum over-hydration and water diffusion coefficient measurements using opto-thermal radiometry and TEWL Instruments.

Skin over-hydration is a common problem that affects many people who wear incontinence pads or diapers. The aim of this study is to develop a new method for stratum corneum (SC) over-hydration and SC water diffusion coefficient measurements using opto-thermal transient emission radiometry (OTTER) and evaporimetry. With OTTER, we can measure the SC surface hydration and hydration gradient. With evaporimetry, we can measure the time-dependent evaporative drying curves of water vapour flux density (WVFD). The combination of hydration results and WVFD results can yield information on the SC water diffusion coefficient and how it depends on the SC surface hydration level. The results show that SC water diffusion coefficient is non-linearly proportional to the SC surface hydration level. The results also show strong correlations between evaporative drying flux measured using the Evaporimeter and surface hydration estimated from OTTER measurements.

Development and preliminary testing of a standardized method for quantifying excess water in over-hydrated skin using evaporimetry.

Although evaporimetry (the measurement of water vapour flux density from the skin) has often been used to study the impact on skin hydration of using products such as baby diapers and incontinence pads, it is difficult to interpret results and to compare data from different studies because of the diversity of unvalidated methodologies used. The aim of this work was to develop a robust methodology for measuring the excess water in over-hydrated skin and test it on volar forearm and hip skin which had been occluded with saline soaked patches. Three repeat measurements were made on the volar forearm and the hip of five young (31-44 years) and six older (67-85 years) women and moderately good within-subject repeatability was found for both skin sites for both subject groups. Measurements taken from the hip were significantly higher (P = 0.001) than those from the arm and had larger coefficients of variation (3.5-22.1%) compared to arms (3.0-14.0%). There were no significant differences between young and older skin, implying that women for future studies could be recruited without regard to age. This is the first time that a robust evaporimetric methodology for quantifying excess water in over-hydrated skin has been described and validated, and it will form a solid basis for future work.

Development and experimental validation of a mathematical model for friction between fabrics and a volar forearm phantom.

An analytical mathematical model for friction between a fabric strip and the volar forearm has been developed and validated experimentally. The model generalizes the common assumption of a cylindrical arm to any convex prism, and makes predictions for pressure and tension based on Amontons' law. This includes a relationship between the coefficient of static friction (mu) and forces on either end of a fabric strip in contact with part of the surface of the arm and perpendicular to its axis. Coefficients of friction were determined from experiments between arm phantoms of circular and elliptical cross-section (made from Plaster of Paris covered in Neoprene) and a nonwoven fabric. As predicted by the model, all values of mu calculated from experimental results agreed within +/- 8 per cent, and showed very little systematic variation with the deadweight, geometry, or arc of contact used. With an appropriate choice of coordinates the relationship predicted by this model for forces on either end of a fabric strip reduces to the prediction from the common model for circular arms. This helps to explain the surprisingly accurate values of mu obtained by applying the cylindrical model to experimental data on real arms.

Development and validation of a new method for measuring friction between skin and nonwoven materials.

A new method for measuring the coefficient of friction between nonwoven materials and the curved surface of the volar forearm has been developed and validated. The method was used to measure the coefficient of static friction for three different nonwoven materials on the normal (dry) and over-hydrated volar forearms of five female volunteers (ages 18-44). The method proved simple to run and had good repeatability: the coefficient of variation (standard deviation expressed as a percentage of the mean) for triplets of repeat measurements was usually (80 per cent of the time) less than 10 per cent. Measurements involving the geometrically simpler configuration of pulling a weighted fabric sample horizontally across a quasi-planar area of volar forearm skin proved experimentally more difficult and had poorer repeatability. However, correlations between values of coefficient of static friction derived using the two methods were good (R = 0.81 for normal (dry) skin, and 0.91 for over-hydrated skin). Measurements of the coefficient of static friction for the three nonwovens for normal (dry) and for over-hydrated skin varied in the ranges of about 0.3-0.5 and 0.9-1.3, respectively. In agreement with Amontons' law, coefficients of friction were invariant with normal pressure over the entire experimental range (0.1-8.2 kPa).

A computerised real-time measurement system to locate the position of the urine stream in designing urine collection devices for women.

A computerised real-time measurement system has been developed and tested for locating the position of the urine stream into a handheld urinal and onto a body-worn pad using arrays of resistive or optical sensors. Experimental data indicates that urine streams were usually scattered over quite a large cross-sectional area (typically 30mm in the anterior/posterior direction) at the point of entry into handheld urinals. However, a correctly placed aperture of length 90mm would have successfully received all the urine from the total of 36 clinical experiments run with seven women. Similarly, experiments to determine the initial position of the urine stream onto body-worn pads indicated that a target area of length 120mm would have received the initial stream of urine from all 54 clinical experiments with 18 women. These data have been used to help with the design of a handheld urinal and a body-worn urine collection interface (the latter using the body-worn pad data) to be used in two variants of a new urine collection device for women (NICMS). Although both resistive and optical sensors provided useful data, the reliability of optical sensors was often compromised by droplets of urine splashing onto light sources or detectors. Future work should focus on protecting them from splashing.

Absorbent products for light urinary incontinence in women.

BACKGROUND: Incontinence is a common and embarrassing problem which has a profound effect on social and psychological well-being. Many people wear absorbent products to contain urine leakage and protect their clothes. It can be difficult to define light urinary incontinence because urine volumes, flow and frequency rates may vary substantially whilst still being considered 'light'. Light incontinence may encompass occasional (monthly) leaks of very small amounts (e.g. 1 g to 2 g) up to frequent leaks (several times per day) of larger amounts (e.g. 20 g to 50 g). A practical definition is urine loss that can be contained within a small absorbent pad (typically 50 g to 500 g; ISO 1996). OBJECTIVES: To assess the effectiveness of different types of absorbent product designs for women with light urinary incontinence. SEARCH STRATEGY: We searched the Cochrane Incontinence Group Specialised Trials Register (3 May 2006) and the reference lists of relevant articles were perused. SELECTION CRITERIA: TYPES OF STUDIES: All randomised or quasi-randomised trials of absorbent products for women with light urinary incontinence. TYPES OF PARTICIPANTS: Women with light urinary incontinence. TYPES OF INTERVENTION: Absorbent products (disposable insert pads, menstrual pads, washable pants with integral pad, washable insert pads) suitable for light incontinence. DATA COLLECTION AND ANALYSIS: Two review authors assessed the methodological quality of potentially eligible studies and independently extracted data from the included trial. MAIN RESULTS: One study with 85 participants met the selection criteria. This trial studied all the absorbent product designs included in this review. Data were presented on all included outcomes. For preventing leakage, for preference and for overall acceptability disposable insert pads are better than disposable menstrual pads which are better than washable pants with integral pad which are better than washable insert pads. There is no strong evidence that either disposables or washables are better for skin health. The disposable insert is the most expensive design and there is no dominant design for cost-effectiveness. There is evidence that some women will prefer alternative designs which are all cheaper than disposable inserts. AUTHORS' CONCLUSIONS: Although data were available from only one eligible trial the data were sufficiently robust to make recommendations for practice. Disposable insert pads are typically more effective than the other designs considered. However, because they are the most expensive, providing choice of designs (or combinations of designs for different circumstances) is likely to be cost-effective.

A critical investigation of ISO 11948-2 and ISO 11948-1 for predicting the leakage performance of small disposable incontinence pads for lightly incontinent women.

ISO 11948-2--an international standard laboratory method developed to predict the leakage performance of small disposable pads for lightly incontinent women--was investigated. The repeatability and reproducibility (precision within and between laboratories, respectively) of two variants on the method were found to be poor. The coefficient of variation for each method variant in each laboratory (two laboratories ran each variant) was higher than 40% for about half the 12 products evaluated. Results differed by up to 94% between laboratories for a given product. The ability of the method to predict the leakage performance of pads was investigated by measuring correlations between the clinical evaluations of the 12 products, and technical evaluations using ISO 11948-2. Correlations were very weak (r < or= 0.487). Accordingly, it is recommended that 11948-2 is withdrawn. A second international standard method (ISO 11948-1)--developed for evaluating large pads, but sometimes used on small ones--was also investigated. Correlations between the clinical evaluations of the 12 products and technical evaluations using ISO 11948-1 were weak (r < or = 0.560). Accordingly, it is recommended that ISO 11948-1 is not used for evaluating small disposable bodyworn pads for women.

How well does ISO 11948-1 (the Rothwell method) for measuring the absorption capacity of incontinence pads in the laboratory correlate with clinical pad performance.

The ability of ISO 11948-1 (the Rothwell method) to predict the leakage performance of disposable bodyworn pads for heavy urinary incontinence was investigated by measuring correlations between models based on clinical evaluations of 138 diapers and inserts (the two major design categories), and technical models based on their Rothwell absorption capacities and design features. Correlations were poorer than in the original 1993 study for the standard (r < or =0.87 compared with r < or =0.95), but still strong enough to help with purchasing choices. For a given Rothwell capacity, the leakage performance of diapers was far superior to inserts; for example, diapers containing 450 and 300 g of urine performed, as well as inserts containing 300 and 100 g, respectively. No evidence was found for any other design feature having a significant impact on leakage performance. The coefficient of variation for Rothwell capacity (a measure of product consistency) had significant impact on the leakage performance of diapers, but not inserts. The probability of diapers with the poorest consistency leaking exceeded that for the best by about 10 percentage points. Similarly, diapers were about 10 percentage points more likely to leak when used at night than during the day. Differences between day-time and night-time use of inserts were not studied.

Mapping liquid distribution in absorbent incontinence products.

This paper reviews methods available for mapping the distribution of fluid in incontinence pad materials to assist with evaluating existing products and developing new ones, and to provide data for building and validating predictive models. Specifically, the following technologies are considered and their strengths and limitations described: discrete sensors based on conductance, temperature or optical measurements, optical imaging, gravimetric methods, X-ray imaging and magnetic resonance imaging. It is suggested that the ideal method would enable fluid distribution to be mapped in three dimensions with good spatial and time resolution in single materials and composite structures of simple and complex geometries under static and dynamic mechanical loading. It would also allow liquid to be mapped in products when worn by users. It is concluded that, although each existing method meets some of these requirements, and each requirement is met, at least reasonably well, by at least one method, improved techniques are needed. The particular need for methods that can provide some measurement of liquid saturation within absorbent products, both in the laboratory and in real use, is highlighted. In many cases, simple methods used appropriately are sufficient to elicit the important aspects of liquid transport and storage within absorbent products.

Experimental and theoretical study of the spread of fluid from a point source on an inclined incontinence bed-pad.

The spread of fluid from a localized source on to a flat fibrous sheet is studied. The sheet is inclined at an angle, alpha, to the horizontal, and the areal flux of the fluid released is Qa. A new experimental study is described where the dimensions of the wetted region are measured as a function of time t, Qa and alpha (>0). The down-slope length, Y, grows according to Y approximately (Qa t)(2/3) (sin alpha)(1/3); for high discharge rates and low angles of inclination, the cross-slope width, X, grows as approximately (Qa t)(1/2), while for low discharge rates or high angles of inclination, the cross-slope transport is dominated by infiltration and X approximately 2(2Ks psi* t)(1/2), where Ks is the saturated permeability and psi* is the characteristic value of capillary pressure. A scaling analysis of the underlying non-linear advection diffusion equation describing the infiltration process confirms many of the salient features of the flow observed. Good agreement is observed between the collapse of the numerical solutions and experimental results. The broader implications of these results for incontinence bed-pad research are briefly discussed.

The further development of the active urine collection device: a novel continence management system.

Continence difficulties affect the lives of a substantial minority of the population. Women are far more likely than men to be affected by urinary incontinence but the range of management options for them is limited. There has been considerable interest in developing an external urine collection system for women but without success to date. This paper describes the development and preliminary clinical testing of an active urine collection device (AUCD), which could provide a solution for sufferers. The device uses stored vacuum, protected by a high bubble point filter, to remove urine as quickly as it is produced. This allows a small battery-operated pump to provide the required vacuum, enabling the device to be portable. Two different types of non-invasive patient/device interface were developed, and tested by volunteers: urinal and small pad. The slimline urinal was popular with users although liquid noise was a problem. The pad interface was successful on occasions but further work is necessary to produce a reliable pad. This study has successfully demonstrated that a prototype AUCD liquid handling system can remove urine at clinically relevant flowrates. While further development is required, volunteer tests have shown that the AUCD could be a useful advance in continence management.

A system for logging incontinence events using a simple disposable sensor.

Many elderly people entering residential or nursing care are already incontinent to some degree, relying on incontinence pads to deal with the consequences. A proportion of these people have been shown to exhibit a regular pattern in their incontinence, which opens up the possibility of mitigating the problem by instituting an individual toileting regime for the person. This can reduce their reliance on incontinence pads, both improving their quality of life, and reducing the cost of care. This paper covers the development and evaluation of a sensor for detecting incontinence events, suitable for use in this setting, and describes the design of an associated electronic logger. The devices form part of an assessment system intended to identify a pattern in incontinence where it exists, and to help with the design of the toilet regime for an individual. The requirement is that the system must reliably record incontinence events, and present the information describing them in a manner appropriate to the users of the devices, who are likely to be non-technical and non-specialist.

An investigation of the repeatability and reproducibility of ISO 11948-1 (the Rothwell method) for measuring the absorption capacity of incontinence pads.

The repeatability and reproducibility (precision within and between laboratories, respectively) of an international standard method (ISO 11948-1, the Rothwell method) for measuring the absorption capacity of incontinence pads was investigated. The 74 shaped disposable bodyworn insert pads for heavy incontinence on the UK market in spring 1997 were tested in three laboratories experienced in using the method, one in each of England, Spain and Sweden. Coefficients of variation (standard deviation as a proportion of the mean) for five repeats rarely exceeded 5% within any laboratory. However, there were systematic differences between laboratories: results from the Swedish and Spanish laboratories typically exceeded those from the English laboratory by 13% and 8%, respectively. The good repeatability suggests that the method is capable of adequate precision but the poor reproducibility implies that the instructions in the standard for building and/or using the test apparatus are inadequate, leaving too much room for interpretation. Having studied the data presented here and viewed videos of the apparatus in use in five laboratories (including the three contributing to this note) the ISO working group which wrote the original standard has identified several likely sources of imprecision and is now working to revise the standard to improve its reproducibility.

Sheaths for urinary incontinence: a randomized crossover trial.

OBJECTIVE: To evaluate the full range of self-adhesive continence sheaths for men available in the UK and thus provide clinicians and consumers with a basis for product selection. PATIENTS AND METHODS: Fifty-eight volunteers (aged 30-89 years) tested each of six different self-adhesive sheaths available in the UK in September 1998 for 1 week each. Thirty subjects applied the sheaths themselves and 28 subjects relied on a carer to do so. During each week subjects completed a diary recording sheath changes and the result of skin inspection, to note any unscheduled sheath changes (because of sheath detachment) and any skin problems. At the end of each week an 11-item questionnaire was completed using a three-point rating scale ('good', 'acceptable', 'unacceptable') to assess the key aspects of product performance. RESULTS: A significantly higher proportion of subjects scored the 'Aquadry Clear Advantage' sheath as 'good' than four of the other sheaths (P < 0.01) and a significantly higher proportion found the 'Incare' sheath to be 'unacceptable' than all of the other sheaths (P < 0.001) for the 'overall opinion' question. Sheath detachments (sheath falling off or blowing off) for the 'Incare' were significantly more common than for four of the other products (P < 0.01). Sheath detachments for the 'Aquadry Clear Advantage' were significantly less common than for two of the other products (P < 0.01). A significantly higher proportion of subjects found sheaths with an applicator to be 'unacceptable' than sheaths with no applicator (P < 0.001) for the 'ease of putting on' and 'overall opinion' questions (when adjusted for previous product use and person applying the sheath). CONCLUSIONS: There were substantial differences between products in their general performance and ergonomics, and for the frequency of detachment as recorded in the diary. The 'Aquadry Clear Advantage' was particularly successful and the 'Incare' particularly unsuccessful when compared with the other sheaths. Sheaths with no applicators were preferred to those with applicators. Applicators are mainly designed to make sheaths easier to put on, especially for carers, but there was no evidence that carers preferred applicators. This may have implications for manufacturers.

Coated catheters for intermittent catheterization: smooth or sticky?

OBJECTIVE: To evaluate the current range of hydrophilic-coated catheters for intermittent self-catheterization, focusing on the adherence of the catheter to the urethral mucosa at the end of catheterization. PATIENTS AND METHODS: In a prospective randomized study, 61 community-based men tested each of four different hydrophilic-coated catheters available in the UK at the time. Subjects used each of the four test catheters for 1 week in a random order, and were provided with the number and size of catheter they normally used. To assess the products, the subjects: (i) timed seven catheterizations using a stop-watch to determine the time taken from extracting the catheter from the water-filled package, to removing the catheter from the penis, having emptied the bladder; (ii) recorded the severity of 'sticking' on catheter removal on a three-point scale (not at all, a little, a lot); and (iii) completed a product-performance questionnaire. RESULTS: There were no significant differences in ratings of 'sticking' between the 'Easicath' and 'Lofric' (P > 0.05), but there were significant differences between these two products and the 'Aquacath' and the 'Silky', which were found to 'stick' more (P < 0.001). The 'Silky' was reported to stick significantly more than the 'Aquacath' (P < 0.001). CONCLUSIONS: Adherence to the urethral mucosa on catheter removal was a common problem, occurring with all catheters, but two products were significantly more likely to stick than the other two. The clinical importance of 'sticking' and the long-term implications are currently unknown. The relative 'sticking' of uncoated catheters has also not been established.

Is there a risk of cross-infection from laundered reusable bedpads?

The risk of cross-infection from reusable incontinence bedpads was assessed by determining their microbial content after one night's use by incontinent adults and after laundering using the standard foul wash procedure specified by the NHS Executive (NHS E, 1995) (which includes heat disinfection at 71 degrees C for 3 minutes). Measurements were made on a total of 145 bedpads from five different product designs. It was found that effective laundering destroyed all known pathogenic organisms, although some commensal flora were isolated in small numbers (mean 12.2 colony forming units/ml). It is concluded that laundering reusable incontinence pads using the foul wash procedure leaves pads safe for multiple patient reuse with no demonstrable risk of cross-infection.

Disposable bedpads for incontinence: predicting their clinical leakage properties using laboratory tests.

A multi-centre project has been run to identify laboratory tests capable of predicting the leakage performance of disposable incontinence bedpads. Each of 95 subjects tested each of six products for a week in turn and reported whether or not they and/or their carers found the leakage performance of each product acceptable. In addition, carers noted the severity with which individual used bedpads had leaked so that, when they had been weighed, their leakage performance could be determined as a function of urine weight. These clinical data were compared with results from the 16 different laboratory tests used routinely for bedpad evaluation in three hospital laboratories. Each test was evaluated by seeing how well the data it yielded correlated with the clinical test data. No individual test was very successful at predicting the performance of bedpads when used as sole protection but a combination of an absorption capacity test and an absorption time test predicted the percentage of users/carers finding leakage performance acceptable, accurate to within +/- eight percentage points for all six test products. A different absorption capacity test proved most successful for bedpads used as back-up to body-worn products. It predicted the percentage of users/carers finding leakage performance acceptable, accurate to +/- five percentage points for all six products.

Predicting the leakage performance of small bodyworn disposable incontinence pads using laboratory tests.

An international multi-centre project has been run to create an international standard for measuring the leakage performance of small, disposable incontinence pads for lightly incontinent women. One hundred and thirteen women tested batches of nine different incontinence pads of widely differing designs and noted the severity with which each individual used pad had leaked so that leakage performance could be determined as a function of urine weight. In addition, testers rated the overall leakage performance of each of the nine products on a five-point scale. These clinical data were compared with laboratory data from 153 different pad measurements, each of which was evaluated by seeing how well the data it yielded correlated with the clinical test data. A wetback test emerged as the clear winner. It usually predicted the clinical leakage performance of pads to an accuracy of +/- 10%. It involved applying 25 ml of 1% w/v saline to a pad and measuring how much escaped into a filter paper held against the wet pad for 1 min under a pressure of 1.5 kPa. Pads which released the least test fluid into the filter paper leaked least in the user tests. The method will be published as an ISO standard during 1997.

Predicting the leakage performance of bodyworn disposable incontinence pads using laboratory tests.

An international multi-centre project (The ISO Pad Leakage Project) was conducted to study the leakage performance of large bodyworn incontinence pads for heavily incontinent users and to create international standards for measuring their absorption capacities in the laboratory. This was achieved by recruiting 13 user test centres through which over 100 incontinent subjects tested each of six different products (each in three different sizes) for a period of about a week to a common protocol. Over 10,000 used pads were collected and weighed and the severity of leakage from each of them recorded. Correlations were sought between these data and the results from some 50 technical tests performed in a total of 16 technical test centres in order to discover the impact of different technical parameters on clinical pad performance. It was found that at low urine weights (less than 50 g, say) pad shaping was the most important predictor of pad leakage performance: shaped pads leaked less. With increasing urine weight, absorption capacity and absorption time increased in importance until at 350 g of urine these two parameters and shaping were of about equal significance: shaped pads with high absorption capacity and fast absorption time leaked least. A second series of analyses identified two absorption capacity tests which produced data correlating well with the overall leakage performance of pads, considering all urine weights together. Both tests were checked for repeatability (precision within laboratories) and reproducibility (precision between laboratories) and have been written up as working draft standards.(ABSTRACT TRUNCATED AT 250 WORDS)

Incontinence pads: clinical performance, design and technical properties.

The paper describes the functional requirements of urinary incontinence pads and reviews the results of several studies which seek to relate the clinical performance of pads to their design and the technical properties of their constituent materials. Pad designs covered include: simple rectangular (for use with conventional pants or marsupial pants containing a pouch); wing-folded; shaped; and all-in-one infant-style diapers. Data on the clinical and technical properties of fluff wood pulp and hydrogel absorbents, and viscose rayon, polyester, polypropylene and polyethylene coverstocks are presented. Attention is focussed on four major aspects of pad function: freedom from leakage; freedom from discomfort and skin damage; ease of application and removal; and aesthetic properties. The relationships established between clinical and technical data will be of interest to health care professionals selecting products; organizations seeking to create standards; and pad designers.