Introduction
At present, there is a growing interest in the concept of “home medicine” the pivot of which is to provide people with capabilities for evaluating own health and making own choice among the available means of health control and disease prevention. The approach is very similar to the medical monitoring of cosmonauts, as crew members use medical equipment and research devices on their own in order to collect and download important medical and physiological information. The time-tested experience of space medicine should be used to the benefit of various categories of populations, particularly those who work under chronic stress, senior people and patients recovering from severe diseases. One of the popular health evaluation technologies, heart variability analysis namely, has been used by space medicine since the very early piloted orbital missions. HRV analysis set the basis for the pre-nosologic approach to the evaluation of health.

Method
Pre-nosologic diagnostics is methodology of differentiating the human organism states in-between the norm and pathology. The necessity to understand mechanisms through which cosmonaut’s organism maintains sufficient adaptability throughout long-duration mission governed further elaboration of the new approach within the space medicine domain that carries the responsibility to evaluate health of essentially healthy people. In-flight investigations show functional changes in neurohormonal regulation evidencing that homeostasis of the vital body systems is maintained owing to the activity of regulation systems [4]. The spaceflight environment challenges cosmonauts with a permanent strain of the regulatory systems and mobilization of the function reserve of organism. Regulation strain is a nonspecific response to a stress-factor. Exposure to the complex of spaceflight factors may provoke equally nonspecific and specific changes. The general adaptation syndrome developed in response to a stress-factor is a nonspecific reaction of organism. Similar processes take place whenever an essentially healthy person gets ill. One of the most effective and recognized methods to evaluate stress-reactivity of organism is HRV analysis New algorithms of HRV analysis have been introduced recently to enable evaluation of the risk of pathology development in long-duration space missions. Also, the concept of adaptation risk during extended stay on space mission has been proposed [8]. Adaptation risk is a probabilistic characteristic of human body adaptability and functionality in different periods of adaptation. Adaptation risk increases as of regulation tension grows and functional reserve becomes depleted. Dynamic health monitoring in normal people with allowance for the adaptation risk criteria was embodied in the concept of individual pre-nosologic monitoring (9). We undertook an attempt to apply this approach to real-time medical health monitoring at home.

Application
A smartphone-based system for pre-nosologic monitoring is presented by our company. The smartphone photo camera forms cardiac signals from the pulse-induced oscillations of finger skin transparency or finger photoplethysmogram. The smartphone application identifies and measures length of cardio intervals and then calculates several HRV statistical indicators. With a special algorithm, depending on resulted values of these indicators, a patient can be classed with one of the next three groups: green – physiologically normal, yellow – straining of adaptation (functional stress) or red – adaptation failure. Considering the fundamental principle of functional state evaluation, the system was named “Health signal lights”. For each person the risk of pathology development (adaptation risk) is estimated. It should be noted that numerous pulse measurements with smartphone are not good for HRV analysis and even less so for conclusion on the risk of pathology. We designed a unique data personalization system to take into account an individual pattern of vegetative regulation in every concrete patient-user. Results of adaptation risk evaluation and data personalization help establish the trend the functional state demonstrates in the course of dynamic monitoring, decide whether and which preventive program should be used or whether a person must not delay with a visit to the doctor. Data of the investigation can be e-mailed to an appropriate address or a specialized analytical center. At present, there are three modifications of the Health signal lights intended for:

  1. pre-nosological monitoring (actual functional state determination)
  2. adaptation risk evaluation (trend prediction)
  3. health control (including health improvement and prophylaxis recommendations)