HomeLog: long-term recording of infant temperature, respiratory and cardiac signals in the home environment

Home telehealth--current state and future trends

OBJECTIVE

The purpose of this paper is to give an overview about the state of the art in research on home telehealth in an international perspective.

METHOD

The study is based on a review of the scientific literature published between 1990 and 2003 and retrieved via Medline in January/February 2004. All together, the abstracts of 578 publications have been analyzed.

RESULTS

The majority of publications (44%) comes from the United States, followed by UK and Japan. Most publications deal with vital sign parameter (VSP) measurement and audio/video consultations ("virtual visits"). Publications about IT tools for improved information access and communication as well as decision support for staff, patients and relatives are relatively sparse. Clinical application domains are mainly chronic diseases, the elderly population and paediatrics.

CONCLUSIONS

Internationally, we observe a trend towards tools and services not only for professionals but also for patients and citizens. However, their impact on the patient-provider relationship and their design for special user groups, such as elderly and/or disabled needs to be further explored. In general, evaluation studies are rare and further research is critical to determine the impacts and benefits, and limitations, of potential solutions and to overcome a number of hinders and restrictions, such as - the lack of standards to combine incompatible information systems; - the lack of an evaluation framework considering legal, ethical, organisational, clinical, usability and technical aspects; - the lack of proper guidelines for practical implementation of home telehealth solutions.

The relationship between inside and outside ambient temperatures in Christchurch, New Zealand

The objective of this study was to examine and identify relationships between hourly recorded meteorological temperature and ambient temperature, measured from within the home-sleeping environment of young infants' homes in Christchurch, New Zealand. From 1991 to 1994, home polysomnography recordings were conducted for up to 6 weeks on 32 infants aged between 2 and 24 weeks. One of the recorded signals was ambient room temperature. In total, 15735 hourly recordings of this temperature were available for analysis. The New Zealand Meteorological Service supplied hourly recordings of climatic temperature, collected over this time, from an exposed site that was considered to be representative of weather conditions for Christchurch. Temperature seasonality, hourly climatic temperature recordings and the interaction of these variables were found to be significantly related to the indoor ambient temperature recordings (all had P < 0.001). Fluctuations in hourly recorded indoor temperature appeared to lag outdoor temperature fluctuations by approximately 2 h; hence, a strong autocorrelation was identified in the regression residuals. The most parsimonious autoregression model accounted for 97% of the variability in the hourly indoor temperature measurements (r2 = 0.97). In Christchurch houses, which typically have poor thermal insulation properties, yet have no central heating capabilities, a very strong association between indoor and outdoor temperatures was clearly demonstrated.

Deterministic properties of apnoeas in an abdominal breathing signal

The paper describes a general set of properties that represent most apnoeas as found in an abdominal breathing signal. An apnoea is a pause in breathing during sleep, and only central apnoeas in infants are considered. Human experts are consulted to determine what properties of the signal they use to recognise apnoeas. A set of deterministic, or shape, properties is developed to represent expert opinion. An apnoea is modelled as a flat region with four properties: flatness, duration, thinness and smoothness. Mathematical descriptions of each property are formulated that discriminate between apnoea and non-apnoea events, and each description is tested for discrimination and independence. The average power of discrimination is 24% +/- 16% and the average correlation coefficient is 0.28 +/- 0.16. Applications include scoring apnoeas for sleep studies and developing standard definitions of apnoeas.

The febrile stress of routine vaccination does not increase central apnoea in normal infants

We tested the hypothesis that the febrile stress of routine vaccination would increase central apnoea in normal infants. Twenty-one normal infants had continuous overnight breathing and temperature recorded at home, before and after 58 routine vaccination episodes. Central apnoea, of at least 5 sec duration, was detected by computer algorithm and confirmed by human inspection. The longest recorded apnoea was 16 sec (n = 1) during 3629 h of sleep. Overnight rectal temperature increased after vaccination (median 0.52 degrees C, 95% CI 0.40, 0.65). Apnoea density reduced on 46/53 vaccination nights (median -29%, 95% CI -20, -37) followed by an increase on subsequent nights (median +10%, 95% CI +1%,+21%). Overall, apnoea density was similar during the 3 nights preceding and 4 nights following vaccination (median +1%, 95% CI +9,-6). The febrile stress of routine vaccination did not increase central apnoea in normal infants.

Breathing, sleep state, and rectal temperature oscillations

Overheating may cause terminal apnoea and cot death. Rectal temperature and breathing patterns were examined in normal infants at home during the first 6 months of life. Twenty one infants had continuous overnight rectal temperature and breathing recordings for 429 nights (mean 20.4 nights, range 7-30) spaced over the first six months of life. Periods when breathing was 'regular' were directly marked on single night records. Sleep state was determined from respiratory variables. 'Regular' breathing was a reliable marker of 'quiet' sleep (specificity 93%). The duration of 'quiet' sleep increased from 6 to 22 minutes from two weeks to three months of age and then remained static, as did the proportion of sleep spent in the quiet phase (9% to 34%). Rectal temperature fell during 66% of quiet sleep and usually rose during rapid eye movement (REM) sleep. The drop in rectal temperature was maximal at the start of quiet sleep, whereas the maximum rise during REM sleep was reached after 10 to 15 minutes. Oscillations in rectal temperature are associated with changes in sleep and breathing state. The maturation of rectal temperature patterns during the first six months of life are closely related to a maturation of sleep state and breathing patterns.

Apnoea detection: human performance and reliability of a computer algorithm

We examined the consistency of apnoea recognition between three human experts. The hypothesis was that computer detection of apnoea could emulate human expert apnoea recognition. The aim was to detect apnoeas with the highest possible accuracy from a single breathing signal, by both human experts and computer. Three human experts independently examined recordings of breathing wave-form from overnight sleep studies from 10 infants aged 3-17 weeks. All apnoeas of 5 s or more were identified and reviewed. However, there still remained 10% disagreement. A computer apnoea detector was implemented. An algorithm analysed statistical properties of the signal to find breathing pauses. Optimal performance was 1% missed apnoeas (compared with the agreed apnoeas identified by the three experts) and 29% false detections. This computer algorithm reliably identified most apnoeas but did not replace the human expert.