Infrared thermal imaging in sepsis

Microcirculatory dysfunction is important in the pathophysiology of sepsis, yet it is not quantified in clinical practice. The skin has a rich microcirculatory blood supply, with subjective assessment of skin temperature used as a marker of perfusion. Infrared thermal imaging allows precise quantification of skin temperature, with alterations reflecting its underlying microcirculatory perfusion. This thesis explores the use of infrared thermal imaging in the acute clinical environment via a series of five studies split into two groups. The first aimed to address the questions of the effect of environmentally reflected temperature and skin tone on measurement accuracy. The second studied whether infrared thermal imaging can be used in the acute clinical setting to provide meaningful information regarding core body temperature and quantify patterns of skin temperature distribution in patients with sepsis.

The studies included healthy volunteers and patients with sepsis and severe sepsis. A variety of experimental techniques were used including measurement of environmental reflected temperature, reflectance spectrophotometry, and infrared thermal imaging of the face, medial canthus and lower limb, to subjectively assess patterns of underlying microcirculatory dysfunction.

Reflected temperature and skin tone did not affect the accuracy of temperatures recorded using thermal imaging. Medial canthal temperature demonstrated a positive correlation to tympanic temperature, predicting pyrexia at a level of ≥36.85oC with a sensitivity and specificity of 79% and 80% respectively. Several temperature distribution patterns were identified in the anterior knee. The pattern of ‘extended cooling’ appeared to be the most significant with a correlation toward increased organ failure and mortality.

In conclusion, infrared thermal imaging can be used as a screening tool for pyrexia in adult patients, and distinct thermal patterns recognised in the anterior knee of patients with sepsis may be associated to illness severity and provide an early indication of those patients at risk of deterioration.