RR duration:Time:Pt:Heart^Fetus:Qn:US.measured
rr duration:time:pt:heart^fetus:qn:us.measured
RR duration:Time:To identify measures at a point in time:Heart^Fetus:Quantitative:Ultrasound.measured
rr duration:time:to identify measures at a point in time:heart^fetus:quantitative:ultrasound.measured