RESUMO
The ensemble averaged impedance cardiogram was evaluated during rest and during vocal mental arithmetic stress in samples of female (n = 17) and male (n = 40) undergraduates. Measures of myocardial performance determined from ensemble averaged signals were compared to those determined by simple beat-to-beat averaging over 60-s and 20-s sampling intervals. In addition, the influence of cardiac interval variability on dZ/dt amplitude measures was assessed. As expected, measures derived by the two averaging techniques corresponded closely, with correlations ranging from r = 0.882 to r = 1.000 for the 60-s sampling intervals, and from r = 0.726 to r = 1.000 for the 20-s sampling intervals. Inverse relationships of comparable magnitude were found between cardiac interval variability and dZ/dt amplitude measures determined by both averaging techniques, suggesting that these relationships did not result simply from artifacts introduced by the ensemble averaging technique. The results support the validity of ensemble averaging as a method for deriving impedance cardiographic measures of myocardial performance.
Assuntos
Cardiografia de Impedância/métodos , Pletismografia de Impedância/métodos , Processamento de Sinais Assistido por Computador , Adolescente , Adulto , Débito Cardíaco , Estudos de Avaliação como Assunto , Feminino , Humanos , Masculino , Descanso , Volume Sistólico , Sístole , TrabalhoRESUMO
The association between breast-feeding status and maternal health is examined. A survey questionnaire was presented via the World Wide Web. Self-reports of 168 breast-feeding and 65 weaned mothers between 4 and 208 weeks postpartum were compared for physician visits, symptomatology, and Perceived Stress Scale scores in the last month. Breast-feeding was associated with fewer physician visits and symptoms and less perceived stress. Moreover, the longer a woman breast-fed before she weaned, the fewer the symptoms and less stress she reported. Breast-feeding is associated with better maternal health both during the breast-feeding period and after weaning. Further research on the effects on maternal health of breast-feeding is indicated. Future prospective longitudinal investigations should address the possible inhibition of lactation by stress and physiological mechanisms that may link breast-feeding and weaning with maternal health.
Assuntos
Atitude Frente a Saúde , Aleitamento Materno , Bem-Estar Materno , Vigilância da População , Estresse Psicológico , Adulto , Austrália , Aleitamento Materno/psicologia , Aleitamento Materno/estatística & dados numéricos , Canadá , América Central , Fatores de Confusão Epidemiológicos , Europa (Continente) , Análise Fatorial , Feminino , Comportamentos Relacionados com a Saúde , Inquéritos Epidemiológicos , Humanos , Recém-Nascido , Internet , Nova Zelândia , África do Sul , América do Sul , Estados Unidos , DesmameRESUMO
The interrater reliability and concurrent validity of two methods of scoring the ensemble-averaged impedance cardiogram were evaluated. Impedance cardiographic and electrocardiographic signals were recorded from 40 undergraduate men and women during a baseline rest period and a vocal mental arithmetic task period. Recordings were scored by four rates using a conventional method, involving ensemble averaging after careful editing of beat-to-beat waveforms, and a streamlined method, involving ensemble averaging without beat-to-beat editing. Intraclass correlations for interrater reliability exceeded .92, whereas intraclass correlations for concurrent validity exceeded .97, indicating excellent agreement between rates and scoring methods for all cardiac measures. The streamlined method was significantly faster than the conventional method. The results indicate that variations in beat-to-beat editing do not constitute a serious source of error in the ensemble-averaged impedance cardiogram and support the interrater reliability and concurrent validity of the two scoring methods.