Additive effect of simultaneously varying respiratory frequency and tidal volume on respiratory sinus arrhythmia.

Our aims were to assess, in healthy young females and males, the effects of the linear joint variation of respiratory frequency (RF) and tidal volume (VT) on the logarithmic transformation of high-frequency power of RR intervals (lnHF). ECG and VT were recorded from 18 females and 20 males during three visually guided 30-s breathing maneuvers: linearly increasing RF (RFLI) at constant VT; linearly increasing VT (VTLI) followed by decreasing VT (VTLD) at fixed RF, and RFLI and VTLI-VTLD combined. VT of females was 20% smaller.

Response patterns of arterial pressure and heart period to Mueller manoeuvre and their comparison to those of Valsalva manoeuvre.

Objective: It has not been established if the Mueller manoeuvre (MM) induces characteristic arterial pressure (AP) and heart rate changes analogous to those observed during its respiratory strain opposite, the Valsalva manoeuvre (VM). Our aims were to explore, on a beat-by-beat basis, if MM evokes well-defined changes in AP and heart period (HP), and to compare these responses with those of VM.

Methods: From the ECG and AP records of 24 healthy subjects who performed VM and MM in sitting position, RR intervals and AP series were computed.