Transcript Blood pressure monitoring

Blood pressure monitoring
Monica Morosan
AAGBI standards of monitoring
A - Induction and Maintenance of Anaesthesia
1. Pulse oximeter
2. Non invasive blood pressure monitor
3. Electrocardiograph
4. Airway gases: oxygen, carbon dioxide and vapour
5. Airway pressure
The following must also be available
6. A nerve stimulator whenever a muscle relaxant is used
7. A means of measuring the patient’s temperature
Methods of BP monitoring
• Indirect: Mercury manometer
Oscillometry
Automatic oscillometric
technique (DINAMAP)
Radial arterial compression
Finapress technique
Microphone (Doppler)
• Direct (Invasive)
Mercury manometer
• BP determined by
palpation or
auscultation
• Korotkoff sounds
Oscillometry
• Aneroid gauge
(Bourdon gauge)
• Measures high
pressures
• Coiled tube
connected to a
pointer
• Bellows
Oscillotonometry
• Does not use
palpation or
auscultation
• 2 cuffs (occluding –
upper, overlaps the
sensing cuff-lower)
• Inflate both and
release the occluding
DINAMAP
• Air pump
• Bleed valve
• Pressure transducer
(measures both
pressure and
oscillations)
• Microprocessor
Problems
• Cuff too small-over reads
• Cuff too large-under
reads
• Over reads at low BP,
under reads at high BP
• Arrhythmias
• External pressure on cuff
• Nerve palsy
• Petechial haemorrhages
Radial artery compression
• Pressure sensor
strapped to wrist
• Sensor driven
hydraulically by a
control system
(applies pressure and
senses oscillations)
• Algorithm –BP from
table values
Finapress technique
• Cuff on finger –
infrared LED and
photocell- detects the
volume of arterial
blood in the finger
• Electronic processor
analyses the
photoplethysmograph
to determine the
volume at MAP
Microphone over artery
• Doppler changes
Invasive measurement
Indications for A line insertion
Uses:
• Arterial pressure
measurement
• Drug delivery
(thrombolysis)
• Procedural access
(angio)
• Mechanical support
techniques (IABP,
ECMO)
Indications:
• Cardiovascular
instability
• Vasoconstrictors/
Inotropes
• BP manipulation
• Blood sampling
Transducer
• Transforms one form
of energy into another
• Based on Wheatstone
bridge
Information from the trace
• BP (systolic, diastolic,
MAP)
• Pulse rate
• Position of dicrotic
notch reflects
peripheral resistance
• Upstroke part reflects
miocardial contractility
Resonance and damping
• Resonance
-Measuring system
posseses a resonant
frequency
-Oscilations occuring
at this frequency will
produce a sine wave
superimposed on the
BP waveform
• Damping
-Property of a system
to resist mechanical
oscillations
-Air bubbles
-Clot
Step response
• Complications:
• Medical (AV fistula,
false anaeurysm,
thrombosis,
ischaemia, infection)
• Equipment
(disconnection, loss
wire, catheter
fracture, inadvertent
intra arterial injection
of drugs)
Summary
Direct
Indirect
Complications
Sources of error