Table 1.

Frequency and time domain methods for estimating the characteristic impedance (Zc).

Frequency range	Notation	Reference
2.0 – 12 Hz	Zc(2–12)	Pepine et al (1979)
2.0 – 16 Hz	Zc(2–16)	Lucas et al (1988)
3.5 – 10 Hz	Zc(3.5–10)	Westerhof et al (1973)
5.0 – 15 Hz	Zc(5–15)	Dujardin et al (1980)
9.0 – 18 Hz	Zc(9–18)	Cox & Bagshaw (1975)
15 – 25 Hz	Zc(15–25)	O’Rourke & Taylor (1967)
Harmonics range
1 – 8	Zc1–8	Clarke et al (1978)
1 – 9	Zc1–9	Peluso et al (1978)
2 – 10	Zc2–10	Gary et al (1994)
3 – 10	Zc3–10	Hughes & Parker (2009)
4 – 10	Zc4–10	Tabima et al (2012)
k – 10a	Zck–10	Gary et al (1994)
6 – 8	Zc6–8	Abel (1971)
4 – 8	Zc4–8	This study
Time domain techniques
Early systole up-slopeb	Zcqc	Dujardin & Stone (1981)
max(p′)/max(q′)	Zc′	Lucas et al (1988)

^aHere k is the harmonic corresponding to the first impedance minimum provided that it appears before the 5’th harmonic.

^bq_c varies between 25% and 95%. In this study, q_c = 25%, 50%, 90% and 95%.