The Application of Biomedical Engineering Techniques to the Diagnosis and Management of Tropical Diseases: A Review <s> Strain Gauge Plethysmography <s> During studies of the pathogenesis of dengue shock syndrome, a condition largely confined to childhood and characterized by a systemic increase in vascular permeability, we observed that healthy controls, age-matched to children with dengue shock syndrome, gave high values of filtration capacity (K(f)), a factor describing vascular permeability. We hypothesized that K(f) might be age dependent. Calf K(f) was studied in 89 healthy Vietnamese subjects aged 5 to 77 years. The K(f) was highest in the youngest children [7. 53 (1.96-15.46) K(f)U; median (range); where the units of K(f), K(f)U=ml.min(-1).100 ml(-1).mmHg(-1)]. Values were 3- to 4-fold lower towards the end of the second decade [4.69 (1.91-7.06) K(f)U]. Young mammals are known to have a larger microvascular surface area per unit volume of skeletal muscle than adults. During development the proportion of developing vessels is greater. Moreover, the novel microvessels are known to be more permeable to water and plasma proteins than when mature. These factors may explain why children more readily develop hypovolaemic shock than adults in dengue haemorrhagic fever and other conditions characterized by increased microvascular permeability. <s> BIB001 </s> The Application of Biomedical Engineering Techniques to the Diagnosis and Management of Tropical Diseases: A Review <s> Strain Gauge Plethysmography <s> Dengue shock syndrome (DSS) is a potentially lethal complication of dengue virus infection associated with hypotension and leakage of plasma water into the extravascular space. To determine whether the underlying pathophysiology of DSS is distinct from that in milder forms of the disease, we assessed microvascular permeability, by use of strain gauge plethysmography, in Vietnamese children with DSS (n=19), or dengue hemorrhagic fever (DHF) without shock (n=16), and in healthy control children (n=15). At admission and after fluid resuscitation, the mean coefficient of microvascular permeability (K(f)) for the patients with dengue was approximately 50% higher than that for the control patients (P=.02). There was no significant difference in K(f) between the 2 groups of patients with dengue; this suggests the same underlying pathophysiology. We hypothesize that in patients with DSS, the fluctuations in K(f) are larger than those in patients with DHF, which leads to short-lived peaks of markedly increased microvascular permeability and consequent hemodynamic shock. <s> BIB002
Liquid metal (Mercury-in-silicon elastomer tube) strain gauge plethysmography has been used in various studies to assess the microvascular permeability in dengue patients BIB001 BIB002 . Gamble et al. BIB001 investigated the possible use of age-related changes in microvascular permeability as a health indicator, and it was found that the value was highest in DSS young children. These findings indicated that children significant factor in the susceptibility of children to DSS using strain gauge plethysmography BIB001 . Both adults and children DSS patients were found to have higher vascular permeability than the healthy control data, and the value was highest in the young children. These findings indicated that children are more susceptible to develop hypovolaemic shock than adults in DHF and other conditions characterized by increased microvascular permeability. Bethell et al. BIB002 , on the other hand, investigated whether the underlying pathophysiology of DSS is distinct from the milder forms of the disease by assessing the microvascular permeability also using strain gauge plethysmography. Three groups were investigated: children with DSS, DHF without shock, and in healthy children. The mean coefficient based on the statistical analysis of microvascular permeability for the patients with dengue was 50% higher than in healthy control patients. However, there was no significant difference in the permeability between the two groups of patients with dengue, which suggests the same underlying pathophysiology. This study also demonstrated that increased microvascular leakage occurs in children with DHF, and is most pronounced in children with DSS. However, the time taken to conduct the measurement was long (40 min average), and the procedure of cuffing the patients may put the patients at risk by inducing more capillary leakage. Children are more susceptible to develop hypovolaemic shock than adults in DHF Bethell et al. BIB002 2001 Assessment of microvascular to differentiate children with DSS, DHF without shock, and healthy children The microvascular permeability for patients with dengue was 50% higher compared to healthy patients. However, there was no significant difference in the permeability between the DSS, DHF dengue patients 