Shyam Rithalia

Developments in transcutaneous blood gas monitoring: a review.

Transcutaneous measurements of oxygen (tcPO2) and carbon dioxide (tcPCO2) are useful in the intensive care unit because they provide continuous and non-invasive estimation of arterial blood gases. In patients with compromised peripheral blood flow the cutaneous values will reflect the haemodynamic changes as blood is shunted away. They have been increasingly used in a variety of clinical situations, such as assessment of skin flap viability, drug evaluation, prediction of wound healing and selection of amputation level in peripheral vascular disease. From a review of available literature it appears that transcutaneous monitors have found another application as indicator of local tissue perfusion.

Assessment of patient support surfaces: principle, practice and limitations

Pressure ulcers cause great pain and suffering to patients as well as unnecessary strain on nursing staff. Their treatment is both costly and time consuming. Every effort therefore should be directed towards their prevention. Understanding of the aetiology of pressure ulcers is still incomplete and assessment of devices aimed at prevention is difficult. Over the years, numerous parameters, including interface pressure and transcutaneous blood gas measurements, have been used to evaluate mattresses and cushions. However, the quality of the data gathered is variable and its clinical interpretation remains unsatisfactory. It could be said that the science of evaluation of support surfaces is still at a formative stage, as clinical validation of many of the approaches has yet to be carried out.

Transverse rotation and longitudinal translation during prosthetic gait - a literature review

Improved technology allows for more accurate gait analysis to increase awareness of nonoptimized prosthetic gait patterns and for the manufacture of sophisticated prosthetic components to improve nonoptimized gait patterns. However, prescriptions are often based on intuition rather than rigorous research findings for evidence-based practice. The number of studies found in the literature that are based on prosthetic research regarding transverse rotation and longitudinal translation is small when compared to topics regarding other types of movements. Some design criteria for prosthetic components described in those studies that permit transverse rotation and longitudinal translation can be found in current designs. However, little research has been conducted to establish their effectiveness on the gait parameters and residual limb. This literature review is an investigation into these motions between the socket and the prosthetic foot, with particular reference to gait characteristics and prosthetic design criteria.

Comparison of oscillometric and intra-arterial blood pressure and pulse measurement

Non-invasive oscillometric blood pressure and pulse measured by an Omron HEM-703CP monitor were compared with arterial values obtained from direct measurements of the radial artery. An excellent correlation and agreement was found between the two methods (systolic r = 0.99; diastolic r = 0.97; pulse r = 0.99), although there was some variability among individual subjects. The range of difference between them was 0 to 10 mmHg for systolic and -6 to +5 mmHg for diastolic pressures. When tested on the bench using the Metron QA-1280 non-invasive blood pressure analyser the HEM-703CP monitor rarely exhibited errors exceeding 2-3 mmHg over a measurement range of 50-200 mmHg.

Evaluation of alternating pressure air mattresses: one laboratory-based strategy

Although many different type of alternating pressure air mattresses (APAMs) are used for the prevention and treatment of pressure ulcers, few high quality randomised controlled trials are available on which to base purchasing decisions. Faced with this situation, physiological measurements are increasingly being used as a surrogate. Laboratory evaluation techniques have centred largely on interface pressure (IP) measurement, typically analysing discrete maximum and minimum levels, or average pressure. However, since pressure relief is time varying, a time-based analysis technique may be more suitable for performance assessment. Measurements of IP, mattress air cell pressure (AP), skin tissue perfusion using laser Doppler fluxmetry (LDF), transcutaneous oxygen (tcPO2) and carbon dioxide (tcPCO2) were taken simultaneously on the sacrum, heels, trochanters and buttock over at least two alternating cycles. Duration of IP below three thresholds (30, 20, and 10 mmHg) as well as the area under the tcPO2, tcPCO2 and LDF curves were calculated automatically. Ten healthy volunteers were recruited to evaluate the pressure-relieving characteristics of two different designs of APAMs. Results indicated significant differences between the products. During the deflation phase of the cycle contact pressures on the heel were significantly lower (p < 0.0001) on the device whose inflation pressure was significantly higher, although there was no significant difference in deflation pressure. Therefore, it is important to note that low APs do not necessarily produce lower IPs under the heel, contrary to the intuitive classical notion. These techniques could assist in the selection of alternating or dynamic surfaces of any description confirmed by further clinical validation.

Review articles : Pressure sores: methods used for the assessment of patient support surfaces:

In the seriously ill, the paralysed and the elderly patient, many factors such as poor skin blood flow, malnutrition and immobility predispose to a high incidence of decubitus ulcers or pressure sores. The development of a sore is a complex process, but skin distortion and localized pressure are considered important precipitating factors. Over the last two decades manufacturers have produced a large variety of support surfaces claiming to be effective in prevention as well as treatment of sores. However, a review of available literature shows that none of the test methods used by different investigators has provided a comprehensive means of determining which device is appropriate for a particular patient.

Laboratory measurement of the interface pressures applied by active therapy support surfaces : A consensus document

A key element in pressure ulcer prevention and management is the selection of appropriate pressure redistributing (PR) patient support surfaces for use while seated and in bed. However little explicit guidance exists allowing standardised quantitative comparison of different PR surfaces based upon their ability to redistribute pressure from anatomical landmarks such as the heels and sacrum. In 2008 a working group was established in Europe through the US National Pressure Ulcer Advisory Panel (NPUAP) support surface standardisation initiative (S3I) and under the aegis of the European Pressure Ulcer Advisory Panel with the specific remit of developing test methods for the evaluation of active therapy support surfaces (alternating pressure air mattresses). This report describes a consensus development process to agree test methods appropriate to compare active therapy surfaces based upon their ability to redistribute pressure from the sacrum and the heels.

Evaluation of intermittent pneumatic compression systems

The operational characteristics of eight intermittent pneumatic compression systems were evaluated. Considerable differences between the pressure/time curves were found when different pumps were compared. The pressure attained in the garments varied from 6 to 124 mmHg and the rate of inflation from less than 1 to 9 mmHg per second.

Comparison of transcutaneous oxygen and carbon dioxide monitors In normal adults and critically Ill patients

The performance characteristics of two transcutaneous combined PO2 (tcPO2) and PCO2 (tcPCO2) sensors were compared with single tcPO2 and tcPCO2 electrodes in critically ill patients. The relationship between arterial blood gases (PaO2, PaCO2) and transcutaneous values was linear. Correlation coefficients (r) varied from 0.79 to 0.87 for tcPO2 and 0.92 to tcPCO2. The tcPO2 readings were always lower than PaO2 values, but the tcPCO2, with modified calibration of the electrodes, did not differ significantly from PaCO2. There was no significant difference of clinical importance in the performance of the three monitoring systems.

Measurement of Arterial Blood Pressure and Pulse

The principles of the measurement of blood pressure are set out, together with a description of the mechanisms employed in automatic pulse monitors. The technical requirements of the measurement of pulse pressure in a variety of situations, such as in Paediatrics and the home environment are discussed.