Disclosures Basic Principles of Urodynamics Andrew Gammie Bristol Urological Institute, Bristol, UK Albyn, Andromeda, Laborie, Mediwatch, MMS Project sponsorship T-Doc LLC Trial sponsorship with grateful acknowledgement of Gordon Hosker The Warrell Unit, St Mary s Hospital, Manchester. UK. Good Urodynamic Practices: Uroflowmetry, Filling Cystometry, and Pressure-Flow Studies Schafer W Abrams P Liao L Mattiasson A Pesce F Spangberg A Sterling AM Zinner NR Van Kerrebroeck P Neurourology and Urodynamics 2002 (pp. 261-274) 274) The Standardisation of Terminology of Lower Urinary Tract Function Abrams P Cardozo L Fall M Griffiths D Rosier P Ulmsten U van Kerrebroeck P Victor A Wein A Neurourology and Urodynamics 2002 (pp. 167-178) 178) An International Urogynecological Association (IUGA) / International Continence Society (ICS) Joint Report on the Terminology for Female Pelvic Floor Dysfunction Haylen BT De Ridder D Freeman RM Swift SE Berghmans B Lee J Monga A Petri E Rizk DE Sand PK Schaer GN Neurourology and Urodynamics 2010 29 (pp. 4-20) International Urogynecology Journal 2010 21 (pp. 5-26) 1
Hosker G Rosier P Gajewski J Sand P Szabo L Capewell A Chapter 6: Dynamic Testing (pp 413-522) www.icsoffice.org org Distributor: Editions 21 Paris France ISBN: 0-9546956-8-2 Topics covered What is pressure? Pressure Transducers Different types of transducer Issues with bladder pressure Normal cystometry Flow measurement Pressure-flow tests Force per unit area demonstration Note the level of fluid in the tube is higher than the balloon. 2
Why is level of fluid in the tube higher than the balloon? The pressure inside the balloon is transmitted up the tube and supports a column of water What, apart from pressure, dictates the height of fluid in the tube? Diameter of tube does not matter 3
Pressures on holiday Does the density of the fluid determine the height to which the fluid goes? Density matters Thus we need to state pressure both in terms of a height and also in terms of a particular fluid Unit of pressure How to measure bladder pressure cm H 2 O 1 cm H 2 O = 0.74 mm Hg 100 cm H 2 O = 74 mm Hg 4
Pressure transducers External pressure transducer with dome and taps External pressure transducer without dome External pressure transducer without dome 5
Catheter-tip pressure transducers T-DOC External transducer specifications Transducer characteristics Good linearity Minimal hysteresis Minimal zero shift Minimal sensitivity shift Calibration Overpressurisation Urodynamic equipment is not perfect and its accuracy can alter with time. Therefore, regular checks of its calibration are essential 6
Transducer types Catheter tip Air filled Fluid filled Catheter-tip pressure transducers Catheter-tip tip pressure transducers Catheter-mounted pressure transducers Microtip transducers Solid state transducers 7
Catheter-mounted pressure transducer s lack of movement artefact Catheter-mounted pressure transducers T-DOC No fluid connecting the patient to the equipment only wires No flushing No need to set anything at a reference level Air-charged catheters No fluid pressure measurement No fluid connecting the patient to the equipment only air No flushing No need to set anything at a reference level No substantial comparisons with fluid-filled filled lines 8
Fluid-filled pressure lines Issues in filling cystometry Do you use external pressure transducers connected to the patient via fluid-filled filled lines or do you use catheter-mounted pressure transducers? External pressure transducer Catheter-mounted pressure transducer Recommendation - Pressure Measuring bladder pressure with a fluid-filled line It is recommended that for intravesical and abdominal pressure recording, external pressure transducers connected to fluid- filled tubes and catheters should be used. If microtip or air-filled catheters are used, any deviation from standard zero and reference level should be minimised and taken into account at the time of analysis sterile water amplifier atm strain gauge atm patient 9
Position of the bladder relative to the transducer Recommendation - Pressure We need to know the reference height of the transducers Compare readings on the same patient Check for realistic pressures Equal reference for p abd, p ves relative to bladder The ICS standard reference height is the upper edge of the symphysis pubis Level with the symphysis pubis Calibration Urodynamic equipment is not perfect and its accuracy can alter with time. Therefore, regular checks of its calibration are essential 0 to 50 cmh 2 O before clinic 10
Pump artefact The effect of air in the system Effect of air in the system Effect of air in the system Transducer Bladder Transducer Bladder 11
Flushing a fluid-filled line Flushing a fluid-filled line patient sterile water Topics covered Pressure Transducers Different types of transducer Issues with bladder pressure Normal cystometry Flow measurement Pressure-flow tests What route is used for inserting pressure sensors in the bladder? Transurethral Suprapubic 12
Suitable sites for measuring abdominal pressure Symbol of pressure Rectum Vagina (upper part) Abdominal stoma p (p not P) Qualifiers Definition of detrusor pressure det detrusor ves - intravesical abd abdominal ura urethral p det = p ves - p abd p det det, p ves, ves, p abd, p ura Why subtract? Why not just display detrusor? p ves p det p det p ves p abd p det p ves p abd 13
Rectal artefact Why then display all three? Quality control Quality control p det p det p ves p ves p abd p abd Quality control Quality control p det p det p ves p ves p abd p abd 14
Quality control Quality control p det p ves p ves p abd p abd Quality control Quality control p det p det p ves p ves p abd p abd Quality control Quality control p det p ves p ves p abd p abd 15
Biphasic spike A BIG issue in filling cystometry Do you zero your transducers inside the patient, outside the patient, to atmospheric pressure or to resting bladder pressure? Zeroing to atmosphere X X Zeroing while connected Recommendation - Pressure It is recommended that there is strict adherence to the ICS standardisation of zero pressure and reference height Zero pressure is the surrounding atmospheric pressure X 16
Pressures at beginning of filling cystometry Pressures at beginning of filling cystometry Reasons to zero to atmospheric pressure Zeroing to atmosphere It produces a scientifically meaningful parameter Has a role in quality control When comparing with other centre s data, it is necessary to compare like with like Some measurements (eg VLPP) are made on the intravesical or abdominal pressure not detrusor pressure Detrusor overactivity & filling 17
Patient position In only 38% of bladders displaying detrusor overactivity is the overactivity manifest on supine filling cystometry y Issues in filling cystometry Detrusor overactivity Do you use external pressure transducers connected to the patient via fluid-filled filled lines or do you use catheter-mounted pressure transducers? Do you zero your transducers inside the patient or to atmospheric pressure? What rate should you fill the patient? What temperature should the filling medium be at? What position should the patient be in? What provocation should be used? How do you define detrusor overactivity? Clinically significant detrusor contractions are those which h are associated with patient symptoms 18
Urodynamic equipment Hardware Normal cystometry nhscep.useconnect.co.uk Free flow rate measurement Uroflowmetry 19
Flowmeters Load cell flowmeter Load cell (gravimetric) Rotating disc Capactive dipstick Pressure sensor Air displacement Rotating disc flowmeter 20
Free flow rate measurement Free flow rate measurement Free flow rate measurement Free flow rate measurement 21
Free flow rate measurement Voided volume Patient apprehension Patient position 22
Free flow rate measurement What does it tell us? Whether there is a problem with voiding It DOES NOT tell us whether any problem is due to outflow obstruction or poor detrusor contractility Normal pressure-flow Normal pressure-flow (female) P detqmax : 40-60 cm H 2 O (male) P detqmax : 20-40 cm H 2 O (female) Outflow obstruction (female) 23
Normal pressure-flow plot Obstructed pressure-flow plot ICS nomogram Pressure-flow plots PURR LPURR URA CHESS ICS (Abrams-Griffiths) nomogram BOOI (Abrams-Griffiths number) BOOI (Abrams-Griffiths number) Female pressure-flow nomogram p -2Q detq max max < 20 non obstructed > 40 obstructed 24
Topics covered - summary Types of flow Pressure Transducers Different types of transducer Issues with bladder pressure Normal cystometry Flow measurement Pressure-flow tests Transducer characteristics Non-linearity Non-linearity Electrical signal does not change in proportion to the pressure put on it Linearity Transducer characteristics Hysteresis Electrical signal for a given pressure is different when that pressure is reached from a lower pressure than when it is reached from higher pressure 25
Hysteresis No hysteresis Transducer characteristics Zero drift Zero shift Electrical signal when no pressure is applied to the transducer changes if the temperature of the transducer changes Transducer characteristics Sensitivity drift Sensitivity shift Electrical signal for a given pressure changes if the temperature of the transducer changes 26