testing of a valsalva assist device (vad) in healthy volunteers performing a valsalva manoeuvre

Conditions: SVT; Vagal Bradycardia

Summary: a prototype for a valsalva assist device (vad), which provides resistance to exhalation, has been developed and is ready for testing in healthy volunteers. there is a need to ensure the device can deliver the required strain and evaluate the physiological response (lowered heart rate) when used to deliver a valsalva manoeuvre (vm) with and without postural modification.

the aim of this study is to evaluate the performance of a novel valsalva assist device (vad) in healthy volunteer and to confirm the physiological effects of a modified vm. specific objectives: to measure and compare peak strain pressure and duration produced using the device compared to a standard manometer in supine and modified postures to evaluate whether there is a difference in vagal tone (drop in heart rate) in healthy volunteers performing a vm using the vad versus manometer. to evaluate whether there is a difference in vagal tone (drop in heart rate) in healthy volunteers performing a modified vm versus a standard supine vm using the vad. to evaluate whether there is a difference in vagal tone (drop in heart rate) in healthy volunteers performing a modified vm versus a standard supine vm using a manometer. the investigators will conduct a single centre repeated measures observational study of use of the device to generate a valsalva strain in a sample of healthy adult volunteers from the university of exeter or rd\&e hospital staff. all participants will be screened for eligibility and undergo informed written consent prior to participation. if participants fail screening due to abnormal clinical readings or vital signs, the chief investigator will review them, any urgent abnormalities (very unlikely) would be reviewed by the chief investigator or delegated emergency department doctor as soon as they are discovered. depending on the severity, if treatment is required urgently then they will be treated in the emergency department. otherwise, they will be referred back to their gp. potential participants will be given written information about the study at least 24 hours prior to recruitment and interested individuals invited to attend screening, recruitment and testing. potential participants will be invited to express an interest in taking part by responding to the trial poster. these posters will be displayed in the medical student common rooms ed department notice board. the potential participant contacts the researcher leading the practical aspects of the trial by phone or email. respondents will be asked how they would like to receive further information (post, email, and phone) and offered an appointment at the clinical research facility (crf) for screening and written consent if eligible, at their convenience but at least 24 hours after receiving the information sheet. given the simple, safe and quick nature of the interventions, participants will be given the choice to take part after written consent or to return on another date, whichever they would prefer, to ensure minimal visits whilst giving participants further time to consider taking part should they wish. the vm is an extremely safe, physiological manoeuvre which is used in everyday life (eg straining at stool) and has been used in trial conditions and clinical practice many thousands of times with no serious adverse events. the investigators will exclude participants who could conceivably be at any risk of harm from performing a vm or from the use of the device. the screening will include 12 lead ecg and physical examination including observations of heart rate, oxygen saturations, respiratory rate and blood pressure. any participants with any detected abnormalities, whether they are excluded from participation or not, will be informed and referred to their primary care physician as appropriate. all testing will be conducted in the clinical research facility (crf) of the royal devon \& exeter hospital, according to a strict trial protocol. test valsalva manoeuvres: participants will undergo a total of 4 vms of the following 4 variations in random order, stratified by method of strain generation to ensure balance between the order of manometer and device use: 1. supine vm using a manometer. supine valsalva strain using a manometer visible to the participant with a target of 40mmhg for 15 seconds 2. supine vm using the device. supine valsalva strain using the device connected to manometer invisible to the participant but visible to a researcher for 15 seconds 3. modified vm using a manometer. semi-recumbent (at 45 degrees) valsalva stain using a manometer visible to the participant with a target of 40mmhg for 15 seconds followed by supine positioning and passive 45-degree leg lift immediately at the end of the strain for a further 15 seconds (the modified vm) 4. modified vm using the device. semi-recumbent (at 45 degrees) valsalva strain using the device connected to manometer invisible to the participant but visible to a researcher for 15 seconds followed by supine positioning and passive 45-degree leg lift immediately at the end of the strain for a further 15 seconds (the modified vm)

Eligibility criteria:
inclusion criteria: * adult volunteers between 18 and 60 years old from university of exeter or rd\&e hospital staff * sinus rhythm on initial ecg * self-reported good health exclusion criteria: * any regular medication other than the oral contraceptive * previous cardiovascular or respiratory disease * any contraindication to performing a vm strain. (eg. known aortic stenosis, recent myocardial infarction, glaucoma, retinopathy) * pregnancy * any ecg abnormality * any contra-indication to postural modification (any reason the participant can't lie flat and have both legs lifted to 45 degrees, eg prosthetic hip * inability or refusal to give written consent to take part * observations of heart rate, oxygen saturations, respiratory rate or blood pressure outside the normal range. specifically blood pressure less than 100 systolic * caffeinated drinks within 6 hours prior to testing * the use of stimulant drugs or alcohol within 24 hours prior to testing

Keywords: valsalva manoeuvre vagal tone modified valsalva valsalva assist device