An approach to using heart rate monitoring to estimate the ventilation and load of air pollution exposure.

BACKGROUND: The effects of air pollution on health are associated with the amount of pollutants inhaled which depends on the environmental concentration and the inhaled air volume. It has not been clear whether statistical models of the relationship between heart rate and ventilation obtained using laboratory cardiopulmonary exercise test (CPET) can be applied to an external group to estimate ventilation. OBJECTIVES: To develop and evaluate a model to estimate respiratory ventilation based on heart rate for inhaled load of pollutant assessment in field studies. METHODS: Sixty non-smoking men; 43 public street workers (public street group) and 17 employees of the Forest Institute (park group) performed a maximum cardiopulmonary exercise test (CPET). Regression equation models were constructed with the heart rate and natural logarithmic of minute ventilation data obtained on CPET. Ten individuals were chosen randomly (public street group) and were used for external validation of the models (test group). All subjects also underwent heart rate register, and particulate matter (PM2.5) monitoring for a 24-hour period. RESULTS: For the public street group, the median difference between estimated and observed data was 0.5 (CI 95% -0.2 to 1.4) l/min and for the park group was 0.2 (CI 95% -0.2 to 1.2) l/min. In the test group, estimated values were smaller than the ones observed in the CPET, with a median difference of -2.4 (CI 95% -4.2 to -1.8) l/min. The mixed model estimated values suggest that this model is suitable for situations in which heart rate is around 120-140bpm. CONCLUSION: The mixed effect model is suitable for ventilation estimate, with good accuracy when applied to homogeneous groups, suggesting that, in this case, the model could be used in field studies to estimate ventilation. A small but significant difference in the median of external validation estimates was observed, suggesting that the applicability of the model to external groups needs further evaluation.

Estimativa da carga de exposição diária a material particulado em indivíduos expostos a poluição ambiental de origem veicular / Daily exposure load estimate of particulate matter in individuals exposed to environmental vehicular pollution

Introdução: O uso de amostradores individuais de poluentes e a medida da ventilação (Ve) tem sido avaliados para estimar a dose de exposição a poluição. Por ser a Ve uma medida de difícil mensuração em campo, tem-se estimado a Ve a partir da frequência cardíaca (FC) utilizando equações de regressão construídas em teste de esforço cardiopulmonar (TECP). Entretanto, ainda persistem dúvidas quanto à sua aplicabilidade para estimar a Ve em indivíduos com características semelhantes, porem que não realizaram o TECP. O objetivo do estudo foi avaliar modelos para a estimativa da Ve a partir da FC, construído a partir de TECP, e testar sua aplicabilidade com o uso de medidas da FC em campo, em diferentes grupos expostos a poluentes. Métodos: Avaliados 60 homens, não tabagistas, 33 que trabalham em vias públicas (Grupo Via Publica - GVP), 17 que trabalham em um Parque (Grupo Parque - GP) e 10 outros participantes (Grupo teste - GT) para validação dos modelos utilizados. Todos tiveram registros da FC e da concentração de MP2,5, durante 24 horas, e realizaram TECP. Resultados: Foram encontradas grandes variações nas equações de regressão entre os indivíduos, e entre os grupos avaliados, mas o emprego de equações de regressão médias, para estimar a carga de exposição com registro da FC de 24 horas em campo revelou-se adequado para situações de FC média abaixo de 80 bpm. Conclusão: Equações individuais estimam de maneira mais precisa a Ve e a carga inalada de poluentes, mas equações construídas em um grupo de indivíduos podem ser empregadas para estimar a Ve em atividades onde a FC média não é elevada, como ocorre com a maioria das situações habituais de atividades de vida diárias

Background: To evaluate the degree of exposure to air pollutants, ventilation (Ve) measurements and individual pollutant sampler have been used. Given that Ve is difficult to measure in field studies, it has been estimated based on the heart rate (HR) using regression equations that were built with cardiopulmonary exercise test (CPET) results. However, doubt still exists as to its applicability to estimate Ve in groups of individuals who did not perform the CPET. The purpose of this study was to evaluate different models for estimating Ve based on HR, constructed from CPET, and to test the models' applicability using HR measurements in the field, in different groups exposed to pollutants. Methods: We evaluated 60 men, nonsmokers: 33 public streets workers (Public Street Group - GPS), 17 park workers (Park Group - GP), and 10 other participants (Test Group - GT) for model validation. All subjects underwent HR and PM2.5 concentration recording throughout 24 hours and CPET. Results: We found wide variations in the regression equations between individuals and the assessed groups. Nonetheless, the use of average regression equations to estimate the exposure load within the 24-hour HR monitoring proved to be suitable for situations of average HR, under 80 bpm. Conclusion: Individual equations estimate Ve and pollutant load inhaled more accurately, but equations constructed based on a group of individuals can be used to estimate Ve in activities where the HR remains lower