Figure 1

Figure shows respirogram (green line at the top of each panel), electrocardiogram (green signal at the bottom of each panel) and mitral inflow pulsed wave Doppler during hyperpneac phase (panels A, B and C), progressing gradually to a hypopneac (D) and then an apneac phase (panels E and F). Progressive decrease in heart rate, from 94 bpm in panel A to 65 bpm in panel F, is shown as hyperpneac phase slows into an apneac phase. This is associated with progressive separation of mitral inflow E and A waves. Regular A waves are evident in panels D, E and F, whereas A waves with minimal E and A separation occur when diastolic mitral inflow coincides with peak inspiration during the hyperneac phase as shown in panels A and B. White arrows depict mitral inflow A waves. Panels G, H and I show the LV outflow tract pulsed wave Doppler velocity and VTI which improves progressively from 9.14 cm during early hyperpneac phase at heart rate of 93 bpm to 10.62 cm during mid respiratory phase at a heart rate of 84 bpm and finally to 13.18 cm at heart rate of 66 bpm during the apneac phase.