Nina Zaproudina

Reproducibility of infrared thermography measurements in healthy individuals

The aim of this study was to investigate the reproducibility of skin surface infrared thermography (IRT) measurements and determine the factors influencing the variability of the measured values. While IRT has been widely utilized in different clinical conditions, there are few available data on the values of the skin temperature patterns of healthy subjects and their reproducibility. We recorded the whole body skin temperatures of sixteen healthy young men with two observers on two consecutive days. The results were compared using intra-class correlations analyses (ICC). The inter-examiner reproducibility of the IRT measurements was high: mean ICC 0.88 (0.73-0.99). The day-to-day stability of thermal patterns varied depending on the measured area: it was high in the core and poor in distal areas. The reproducibility of the side-to-side temperature differences (deltaT) was moderately good between the two observers (mean ICC 0.68) but it was reduced with time, especially in the extremities, mean ICC 0.4 (-0.01-0.83). The results suggest that the IRT technique may represent an objective quantifiable indicator of autonomic disturbances although there are considerable temporal variations in the measured values which are due to both technical factors such as equipment accuracy, measurement environment and technique, and physiological variability of the blood flow, and these factors should be taken into account.

Determinants of serum 25-hydroxyvitamin D concentration in Finnish children: the Physical Activity and Nutrition in Children (PANIC) study

We studied vitamin D intake, serum 25-hydroxyvitamin D (S-25(OH)D) concentration, determinants of S-25(OH)D and risk factors for S-25(OH)D <50 nmol/l in a population sample of Finnish children. We studied 184 girls and 190 boys aged 6-8 years, analysed S-25(OH)D by chemiluminescence immunoassay and assessed diet quality using 4-d food records and other lifestyle factors by questionnaires. We analysed the determinants of S-25(OH)D using linear regression and risk factors for S-25(OH)D <50 nmol/l using logistic regression. Mean dietary intake of vitamin D was 5·9 (sd 2·1) µg/d. Altogether, 40·8 % of children used no vitamin D supplements. Of all children, 82·4 % did not meet the recommended total vitamin D intake of 10 µg/d. Milk fortified with vitamin D was the main dietary source of vitamin D, providing 48·7 % of daily intake. S-25(OH)D was <50 nmol/l in 19·5 % of children. Consumption of milk products was the main determinant of S-25(OH)D in all children (standardised regression coefficient β=0·262; P<0·001), girls (β=0·214; P=0·009) and boys (β=0·257; P=0·003) in multivariable models. Vitamin D intake from supplements (β=0·171; P=0·035) and age (β=-0·198; P=0·015) were associated with S-25(OH)D in girls. Children who drank ≥450 g/d of milk, spent ≥2·2 h/d in physical activity, had ≥13·1 h/d of daylight time or were examined in autumn had reduced risk for S-25(OH)D <50 nmol/l. Insufficient vitamin D intake was common among Finnish children, one-fifth of whom had S-25(OH)D <50 nmol/l. More attention should be paid to the sufficient intake of vitamin D from food and supplements, especially among children who do not use fortified milk products.

Asynchronicity of facial blood perfusion in migraine.

Asymmetrical changes in blood perfusion and asynchronous blood supply to head tissues likely contribute to migraine pathophysiology. Imaging was widely used in order to understand hemodynamic variations in migraine. However, mapping of blood pulsations in the face of migraineurs has not been performed so far. We used the Blood Pulsation Imaging (BPI) technique, which was recently developed in our group, to establish whether 2D-imaging of blood pulsations parameters can reveal new biomarkers of migraine. BPI characteristics were measured in migraineurs during the attack-free interval and compared to healthy subjects with and without a family history of migraine. We found a novel phenomenon of transverse waves of facial blood perfusion in migraineurs in contrast to healthy subjects who showed synchronous blood delivery to both sides of the face. Moreover, the amplitude of blood pulsations was symmetrically distributed over the face of healthy subjects, but asymmetrically in migraineurs and subjects with a family history of migraine. In the migraine patients we found a remarkable correlation between the side of unilateral headache and the direction of the blood perfusion wave. Our data suggest that migraine is associated with lateralization of blood perfusion and asynchronous blood pulsations in the facial area, which could be due to essential dysfunction of the autonomic vascular control in the face. These findings may further enhance our understanding of migraine pathophysiology and suggest new easily available biomarkers of this pathology.

Nitroglycerin-induced changes in facial skin temperature: 'cold nose' as a predictor of headache?

Nitroglycerin (NTG) often induces headaches when used to treat cardiac diseases. Such property of NTG has been widely used in modelling of migraine‐like headaches. However, background reasons, predisposing to the development of NTG‐headache, are less studied. The main aim of our study was to find, using NTG model, easily accessible markers of the vascular changes associated with headache. Because changes in the blood flow alter the local skin temperature (Tsk), we studied the relationship between the regional changes in the facial Tsk and NTG‐induced headaches. Tsk was measured with infrared thermography in 11 healthy women during 3 h after sublingual NTG administration. NTG caused headache in five women, and four of them were the first‐degree relatives of migraine patients. Notably, before NTG administration, subjects in the headache group had lower Tsk values, especially in the nose area, than women in the pain‐free group (n = 6). NTG‐induced headache was associated with a long‐lasting increase of Tsk over the baseline. In sharp contrast, in the pain‐free group, the Tsk reduced and returned rapidly to the baseline. Thus, the low baseline level and greater increase of regional Tsk correlated with the incidence of headache that supports a role of greater vascular changes in headache happening on the basis of the dissimilarities in vascular tone. An easily accessible phenomenon of ‘cold nose’ may indicate background vascular dysfunctions in individuals with predisposition to headache. Facial infrared thermography, coupled with NTG administration, suggests a novel temporally controlled approach for non‐invasive investigation of vascular processes accompanying headaches.

Measurements of skin temperature responses to cold exposure of foot and face in healthy individuals: variability and influencing factors.

Skin vasomotor responses to cold exposure (CE) have been measured widely and shown to be abnormal in some clinical conditions. Among other methods, monitoring of skin temperature (Tsk) changes has been applied for those purposes. We investigated such changes simultaneously in different skin areas of healthy young men during foot and facial CE. Tsk was measured using infrared thermography in the big toe and dorsum of the left foot and with a contact thermode in the fingertip. The relationship of Tsk responses within individuals and factors influencing them were examined using mixed model analysis. Tsk changes varied greatly between sessions, measured areas and individuals. Foot CE that was painful produced both stronger central circulatory and Tsk responses than facial CE. Tsk changes were prominent in the fingertip, moderate in the toe and weak or absent in the dorsal foot. The Tsk changes were related to the baseline levels and changes of blood pressure, heart rate, the baseline Tsk values and stimulus intensity. However, despite the different cold stimuli and measurement techniques, an intra‐individual correlation of the Tsk responses was good. In the foot, the big toe area is applicable for studies of Tsk reactions when warm, and the modified Tsk gradient helps to evaluate the level of peripheral vasoconstriction. The cold‐induced Tsk changes may be informative in the studies of the cutaneous vasoregulation but the individual character of the cold stress reactivity and numerous confusing factors should be considered when drawing conclusions on the basis of the recorded results.

Are the infrared thermography findings skin temperature-dependent? a study on neck pain patients.

Skin temperature (Tsk) disorders have been proposed as sign of impaired innervation in several conditions, but the influence of different factors on the infrared thermography (IRT) findings remains unclear.

Acral coldness in migraineurs.

In search for new biomarkers of vascular disturbances accompanying migraine, we compared the facial and hand skin temperatures in 41 women, including 12 migraine patients during the headache-free period and 29 healthy controls. Compared to the controls, the acral skin temperatures were lower in migraineurs, especially in those with right-sided headache. Our findings suggest that migraine is associated with a peripheral coldness possibly due to abnormal autonomic vascular control. The cold nose and hands may represent easily assessable biomarkers of these disorders.