Cardiovascular response to Valsalva’s manoeuvre (VM) in conscious girls with Rett syndrome (RS)

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University of Bristol (2001) J Physiol 536P, S013

Communications: Cardiovascular response to Valsalva’s manoeuvre (VM) in conscious girls with Rett syndrome (RS)

L. Engerström, I. Witt-Engerström, P.O.O. Julu*, F. Apatopolus† and S. Hansen†

Rett Center, Frösö Strand, àstersund Hospital, Sweden, *Peripheral Nerve and Autonomic Unit, Imperial College London, Central Middlesex Hospital and †Department of Medical Physics, Institute of Neurological Sciences, Glasgow, UK

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Rett syndrome is a neurodevelopmental disorder with immature brainstem and multiple breathing dysrhythmias including spontaneous VM (Julu et al. 1999). There is increased intrathoracic pressure during the VM enough to provoke changes in arterial blood pressure (BP) and heart rate (HR). The intrathoracic pressure increases due to forced expiration against closed glottis causing a pentaphasic BP response. We studied the details of cardiovascular reponses to VM in four RS girls in routine clinical examination.

Arterial BP waveforms from the Finapres and electrocardiographic R-R intervals (RR) from the NeuroScope (MediFit Diagnostics Ltd, London) were fed continuously into a microcomputer via the MedullaLab (MediFit Diagnostics Ltd, London) to calculate the systolic BP (SBP) in mmHg and heart rate (HR) in beats min-1, beat-by-beat using the VaguSoft software as previously described (Julu et al. 1996). The pulse-synchronised variation of RR was measured continuously by the NeuroScope and fed into the microcomputer as a non-invasive index of cardiac vagal tone (CVT) (Little et al. 1999). Arbitrary units of an atropine-derived linear vagal scale (LVS) were used to quantify the CVT (Julu, 1992). Continuous measurements covered the VM and intevening intervals.

Roman numerals represent the five clinical phases of BP changes in VM (Table 1). Phase I is the initial rise in BP, phase IIe is the first drop in BP, phase IIi is the recovery from IIe during positive intrathoracic pressure before the glottis opens. Phase III is a second drop in BP following sudden opening of the glottis, marked by forced expiration and phase IV is the rebound increase in BP due to increased sympathetic tone during the VM. The overall HR changes are saw-tooth shaped. The values of SBP, HR and CVT from the start through phases of VM are given in Table 1.

The responses of SBP to VM in Rett syndrome are similar to those previously described in healthy adults (Eckberg, 1980). We have for the first time recorded continuous cardiovascular parasympathetic activity during VM and our results show drops in CVT during baroreceptor unloading and rebound increases during recovery from the VM, consistent with current teaching in physiology. Future studies in healthy volunteers is required for comparison with RS.

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Where applicable, experiments conform with Society ethical requirements.

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