Exploring Pressures, Tissue Reperfusion and Body Positioning: A Pilot Evaluation

Objective:
To assess the relationship in healthy adults and critically ill patients between: patient position, body mass index (BMI), patient body temperature; and interface pressure (IP) and tissue reperfusion (TR). Also to assess the relationship in critically ill patients between: sequential organ failure assessment (SOFA) score, Braden Scale score for predicting pressure injury risk, Acute Physiology and Chronic Health Evaluation II (APACHE II) severity of disease classification score, and IP and TR.

Setting:
27-bed intensive care unit (ICU) of an Australia tertiary hospital.

Participants:
23 low- and high-acuity ICU patients and 9 healthy adult volunteers.

Methods:
IP and TR outcomes were measured at the sacrum and greater trochanter. Repeated measures analyses of variance (ANOVAs) and doubly multivariate repeated measures ANOVAs were conducted using peak pressure index (PPI), and peak time (PT), settled time constant (STC) and normalised hyperaemic area (NHA) measures of TR as outcomes. Participant type, body mass index (BMI), Braden and APACHE II scores and patient body temperature were considered as between-groups factors and covariates.
Results Not all IP readings could be obtained from ICU patients. TR readings were collected from all recruited patients, but not all TR measurements were mutually uncorrelated. Controlling for age, PPI readings substantively differed between participant types (p=0.093), with the highest values associated with high-acuity patients and the lowest with healthy adults; the association was not substantive when controlling additionally for age and BMI. The controlling variable of age was also significant (p=0.008), with older participants having higher scores than younger ones. No statistically significant associations between any measured parameter and TR variables were revealed; however, temperature was revealed to be substantively related to TR (p=0.091).

Conclusions:
While not being powered to detect significant effects, this pilot analysis has nonetheless determined several associations of importance, with substantive differences in outcomes observed between low- and high-acuity ICU patients; and between ICU patients and healthy volunteers