central venous pressure and intra-arterial blood pressure monitoring. various sites for cvp and Ibp insertion. working principle for cvp and ibp. indication and complication. various waveform of cvp and ibp
2. CVP
Pressure measured in the central veins close to the heart. It indicates mean right atrial pressure and is
frequently used as an estimate of right ventricular preload.
CVP reflects the amount of blood returning to the heart and the ability of the heart to pump the blood
into the arterial system.
It is the pressure measured at the junction of the superior vena cava and the right atrium.
CVP monitoring helps to assess cardiac function, to evaluate venous return to the heart, and to
indirectly gauge how well the heart is pumping.
3. It reflects the driving force for filling of the right atrium & ventricle.
It indicates the relationship of blood volume to the capacity of the venous system.
Normal CVP in an awake , spontaneously breathing patient : 1-7 mmHg or
5-10 cm H2O.
Mechanical ventilation : 3-5 cm H2O higher
Single value has no value. Trend is important.
4. In terms of pressure
1cm H2O = 0.73 mmHg.
1 mmHg = 1.36 cm H2O.
5.
6.
7.
8.
9.
10. Indication
• Major operative procedures involving large fluid shifts or bloodloss
• Intravascular volume assessment when urine output is not reliable orunavailable
• Temporary Hemodialysis
• Surgical procedures with a high risk for air embolism, CVP catheter may be used toaspirate
intracardiac air
• Frequent venous blood sampling, Inadequate peripheral intravenousaccess
• Temporary pacing
• Venous access for vasoactive or irritating drugs & Chronic drugadministration
• Rapid infusion of intravenous fluids (using largecannulae)
• Total parenteral nutrition
11. Factors AffectingCVP
• Cardiac Function
• Blood Volume
• Capacitance of vessel
• Intrathoracic & Intraperitoneal pressure
01/02/2018
14. 01/02/2018
Right IJV is
Preferred
• Consistent, predictable anatomy
• Alignment with RA
• Palpable landmark and high success rate
• No thoracic duct injury
15. CENTRAL VENOUS PRESSURE
MONITORING
In central venous pressure monitoring, the physician inserts a catheter through a
vein and advances it until its tip lies in or near the right atrium.
Because no major valves lie at the junction of the vena cava and right atrium,
pressure at end diastole reflects back to the catheter.
17. 01/02/2018
Mechanical
Events
Waveform Component Phase of Cardiac Cycle Mechanical Events
‘a’ wave End Diastole Atrial Contraction(after P wave)
‘c’ wave Early Systole Isovolumic right ventricle
contraction, TV bow in RA(after
QRS)
‘x’ descent Mid Systole Atrial Relaxation, Descent of RV
base(TV annulus)
‘v’ wave Late Systole Filing of RA with venous blood(just
after T wave)
‘y’ descent Early Diastole Early ventricular filling, opening of
TV
‘h’ wave Mid to Late Diastole Diastole plateau
18.
19. ‘a’ wave
• Atrial Contraction(after P wave)
• End Diastole
• Prominent a wave: resistance in RV filling- RVH, TS, Tamponade,
PS, Pulmonary hypertension
• Absent a wave: Atrial fibrillation or
• flutter
Cannon A waves occur as the RA
contracts against a closed TV: junctional
rhythm, CHB,ventricular arrhythmias
01/02/2018
20. ‘c’ wave
• Isovolumic right ventricle contraction, TV bow in RA(after QRS)
• Early Systole
• TR: Tall Systolic c-v wave
• It is call holosystolic cannon v waves
01/02/2018
21. ‘x’
descent
• Atrial Relaxation, Descent of RV base(TV annulus)
• Mid Systole
• Dominant x descent –good RV function and vice versa
• Cardiac Tamponade
- X descent is steep & Y descent is diminished
01/02/2018
22. ‘v’ wave
• Filing of RA with venous blood(just after T wave)
• Late Systole
• Prominent v wave with increase venous return. ASD, PAPVC or TAPVC,
A-V malformation
• Large V waves may also appear later in systole if the ventricle becomes
noncompliant because of ischemia or RV failure.
• Decrease in RA emptying. TS
01/02/2018
23. ‘y’
descent
• Early ventricular filling, opening of TV
• Early Diastole
• Attentuation of y descent: TS, Tachycardia, RVF, Tamponade,PS
01/02/2018
24. 01/02/2018
Measureme
nt
• The phlebostatic axis is the reference point for zeroing the
hemodynamic monitoring device.
• 4th intercostal space, mid-axillary line
• 1 mmHg = 1.36 cm H2O.
• the first step in pressure transducer setup is to zero the transducer by exposing it
to atmospheric pressure
• Thus, a cardiac filling pressure of 10 mm Hg is 10 mm Hg higher than ambient
atmospheric pressure.
25. Respiratory
Effect
A, During spontaneous ventilation, the onset of
inspiration (arrows) causes a reduction in
intrathoracic pressure, which is transmitted to both
the CVP and pulmonary artery pressure (PAP)
waveforms. CVP should be recorded at end-
expiration.
B, During positive-pressure ventilation, the onset of
inspiration (arrows) causes an increase in
intrathoracic pressure. CVP is still recorded at end-
expiration.01/02/2018
26.
27.
28. 01/02/2018
• Fluid Responsiveness: inspiratory fall of CVP > 1 mmHg is high
predictive of fluid responders
• Keeping CVP > 5 mmHg in renal transplant surgery is associated with good
graft function In first 3 post op days
• Post cardiac surgery CVP > 15 mmHg is associated with poor outcome
29. 01/02/2018
• Decrease in CVP is relatively late sign of depletion of intravascular volume
• CVP is better measurement of volume status in anesthetised patient whose
autonomic reflexes are abolished
• Goal directed fluid therapy has not shown good results in critically ill patients.
30. Location – under the medial border of lateral head of SCM.
Right IJV preferred – leads straight to SVC and RA – minimises injury to thoracic
duct, pneumothorax.
Position :
Supine with head down position
Head turned to opposite side
IJV APPROACH
35. USG guided – advantages :
Minimises injury to carotid artery
Helps to identify the anatomy
Especially advantageous in patients with difficult neck
anatomy, prior neck surgeries and anticoagulated patients.
IJV APPROACH
36. Tortuous path – reduced success rate
Advantages – avoids advancement of needle into
deeper structures.
EJV APPROACH
37. Supraclavicular and infraclavicular approach
High incidence of complications – esp pneumothorax.
Site of choice in patients undergoing surgeries of head and neck and in trauma
patients immobilised with cervical collar
Useful in parentral nutrition/prolonged CVP monitoring
SUBCLAVIAN VEIN
38. Advantage –
Decreased complications
Ease of access
Disadvantage –
Difficult to ensure correct central venous placement of
cathether.
Cardiac perforation and arrythmias
ANTECUBITAL VEINS
39. ABSOLUTE
SVC syndrome – CI to upper extremity placement
Infection at the site of insertion
RELATIVE
Coagulopathies
Newly inserted pacemaker wires
CONTRAINDICATIONS- CENTRAL
VENOUS CANNULATION
40. COMPLICATIONS OF CENTRAL VENOUS
CANNULATION
Arterial puncture with hematoma
A-V fistula
Hemothorax, chylothorax, pneumothorax
Brachial plexus injury
Horner’s syndrome
Air embolism
Catheter/wire shearing
COMPLICATIONS
43. INTRA ARTERIAL BLOOD PRESSURE
• Intra-arterial blood pressure (IBP) measurement is often considered to be the
gold standard of blood pressure measurement.
• It involves the insertion of a catheter into a suitable artery and then displaying
the measured pressure wave on a monitor.
44. INDICATIONS:
1. Continuous, real-time blood pressure monitoring
2. Planned pharmacologic or mechanical cardiovascular manipulation
3. Repeated blood sampling
4. Failure of indirect arterial blood pressure measurement
5. Supplementary diagnostic information from the arterial waveform
6. Determination of volume responsiveness from systolic pressure or pulse pressure variation
46. COMPLICATIONS
1. Distal ischemia, pseudoaneurysm, arteriovenous fistula
2. Hemorrhage, hematoma
3. Arterial embolization
4. Local infection, sepsis
5. Peripheral neuropathy
6. Misinterpretation of data
7. Misuse of equipment
47. ADVANTAGES
Reduces the risk of tissue injury and neuropraxias in patients
who will require prolonged blood pressure measurement
More accurate than NIBP, especially in the extremely
hypotensive or the patient with arrhythmias.
48. COMPONENTS OF AN IABP MEASURING
SYSTEM :
1. Intra-arterial Cannula
2. Fluid Filling tube
3. Transducer
4. Infusion/Flushing
system
5. Signal processor, amplifier
and display
49. COMPONENTS OF AN IABP
MEASURING SYSTEM
Wheatstone bridge
diagphragm
Strain gauge
Signal processor, amplifier
and display
50. Intra-arterial cannula
Should be wide and short
Forward flowing blood contains kinetic energy
When flowing blood is suddenly stopped by tip of catheter, kinetic energy
is partially converted into pressure.
This may add 2-10mmHg to SBP
This is referred to as end hole artifact or end pressure product.
Cannulation sites: Radial, Ulnar, Dorsalis Pedis, Posterior tibial, Femoral arteries
51. Fluid filled tubing
Provides a column of non-compressible, bubble free fluid between the
arterial blood and the pressure transducer for hydraulic coupling.
Ideally, the tubing should be short, wide and non-compliant (stiff) to reduce
damping.
extra 3-way taps and unnecessary lengths of tubing should be avoided where possible
52. Transducer
Converts mechanical impulse of a pressure wave into an electrical signal
through movement of a displaceable sensing diaphragm.
It functions on principle of strain gauze and wheatstone bridge circuit.
54. Strain Gauze
Are based on the principle that the electrical resistance of wire or silicone
increases with increasing stretch.
The flexible diagram is attached to wire or silicone strain gauges in such a way
that with movement of the diaphragm the gauges are stretched or compressed,
altering their resistance
55. Infusion/flushing system
Fills the pressure tubing with fluid and helps prevent blood from clotting in
catheter, by continuously flushing fluid through the system at a rate of 1-
3ml/hr,
-by keeping a flush bag at pressure of 300mmHg.
Heparinizing the flush system is not necessary
56. Signal processor, amplifier and display
The pressure transducer relays its electrical signal via a cable to a microprocessor
where it is filtered, amplified, analyzed and displayed on a screen as a waveform of
pressure vs. time.
Beat to beat blood pressure can be seen and further analysis of the pressure waveform
can be made, either clinically, looking at the characteristic shape of the waveform,
or with more complex systems, using the shape of the waveform to calculate cardiac
output and other cardiovascular parameters
57. COMPONENTS OF AN
IABP MEASURING SYSTEM
Wheatstone bridge
diagphragm
Strain gauge
Signal processor, amplifier
and display
58. Invasive Blood Pressure Monitoring
• Transducer Zeroing :
For accurate reading, atmospheric pressure must be discounted from the
pressure measurement
• Transducer Levelling :
level with the patient’s heart, at the 4th intercostal space, in the mid-
axillary line.
60. Levellingandzeroing
Zeroing :
• For a pressure transducer to read accurately, atmospheric pressure
must be discounted from the pressure measurement.
• This is done by exposing the transducer to atmospheric pressure and
calibrating the pressure reading to zero.
• The level of the transducer is not important.
60
62. •Levelling:
• The pressure transducer must be set at the appropriate level in relation
to the patient in order to measure blood pressure correctly.
• This is usually taken to be level with the patient’s heart, at the 4th
intercostal space, in the mid-axillary line.
• A transducer too low over reads, a transducer too high under reads.
26-07-2016 Dr. Vikram Naidu
62
64. The normal waveform for an invasive
ABP
1. Initial sharp rise (left ventricular
systole
2. Rounded slope represents the
peak systolic pressure
3. Dicrotic notch: represents the closure
of the aortic valve
4. Descending slope signifies the
beginning of diastole.
66. • As the pressure wave travels from the central aorta to the periphery,
the arterial upstroke becomes steeper, the systolic peak increases, the dicrotic
notch appears later, the diastolic wave becomes more prominent, and end-diastolic
pressure decreases.
26-07-2016 Dr. Vikram Naidu
66
68. Invasive Blood Pressure Monitoring
PHYSICAL PRINCIPLES
• Sine Waves :
1. Amplitude
2. Frequency
3. Wavelength
4. Phase
69. FUNDAMENTAL FREQUENCY
• The arterial pressure wave consists of a
fundamental wave (the pulse rate) and
a series of harmonic waves.
-These are smaller waves whose
frequencies are multiples of the
fundamental frequency
• The process of analyzing a complex
waveform in terms of its constituent
sine waves
( Fourier Analysis )
70. Invasive Blood Pressure Monitoring
• The complex waveform is broken down by a microprocessor into its component sine
waves, then reconstructed from the fundamental and eight or more harmonic waves of
higher frequency to give an accurate representation of the original waveform.
• The IABP system must be able to transmit and detect the high frequency components of the
arterial waveform (at least 24Hz) in order to represent the arterial pressure wave precisely.
• This is important to remember when considering the natural frequency of the system
71. The arterial pressure wave has a characteristic periodicity termed the
fundamental frequency, which is equal to the pulse rate.
Although the pulse rate is reported in beats per minute, fundamental
frequency is reported in cycles per second or hertz (Hz).
If the heart rate is 60 beats/min, then this equals one cycle per second ( 1
Hz) So the fundamental frequency is 1 Hz.
72. Accuracy of IABP Monitoring
• :
1. Natural Frequency and Resonance: quantifies how rapidly the system
oscillates
2. Damping Coefficient: quantifies the frictional forces that act on the
system and determine how rapidly it comes to rest.
3. Transducer Zeroing and Levelling
73. Natural Frequency & Resonance
Every material has a frequency at which it oscillates freely. This is called its
natural frequency.
If a force with a similar frequency to the natural frequency is applied to a
system, it will begin to oscillate at its maximum amplitude. This phenomenon
is known as resonance.
74. Invasive Blood Pressure Monitoring
If the natural frequency of an IABP measuring system lies close to the
frequency of any of the sine wave components of the arterial waveform, then
the system will resonate, causing excessive amplification, and distortion of
the signal.
So, it is important that the IABP system has a very high natural frequency – at
least eight times the fundamental frequency of the arterial waveform (the
pulse rate). Therefore, for a system to remain accurate at heart rates of up to
180bpm, its natural frequency must be at least: (180bpm x 8) / 60secs =
75. The natural frequency of a system is determined by the properties of its components. It may
be increased by:
- Reducing the length of the cannula or tubing
- Reducing the compliance of the cannula or diaphragm
-Reducing the density of the fluid used in the tubing
-Increasing the diameter of the cannula or tubing
76. Most commercially available systems have a natural frequency of around
200Hz but
this is reduced by the addition of three-way taps, bubbles, clots and
additional lengths of tubing
77. Damping Coefficient
• :
The amount of damping inherent in a
system can be described by the damping
coefficient (D) which usually lies between 0
and 1
• Critical-Damping
• Over-Damping
• Under-Damping
• Optimal Damping
78. DAMPING
Anything that reduces energy in an oscillating system will reduce the amplitude of
the oscillations.
Some degree of damping is required in all systems (critical damping), but if
excessive (overdamping) or insufficient (underdamping) the output will be adversely
effected.
In an IABP measuring system, most damping is from friction in the fluid pathway
79. OVER DAMPING FACTORS
Three way taps
Bubbles and clots
Vasospasm
Narrow, long or compliant tubing
Kinks in the cannula or tubing
Damping also causes a reduction in the natural
frequency of the system, allowing resonance and
distortion of the signal.
81. FAST-FLUSH TEST
• Provides a convenient bedside method for determining dynamic
response of the system
• Natural frequency is inversely proportional to the time between
adjacent oscillation peaks
• The damping coefficient can be calculated mathematically, but it is
usually determined graphically from the amplitude ratio
81
82. • Performed by opening the valve of continuous flush device such that flow
through catheter- tubing system is acutely increased to 30ml/ hr from usual 1-
3ml/ hr.
• This generates an acute rise in pressure within the system such that a square
wave is generated on bedside monitor.
• With closure of valve, a sinusoidal pressure wave of a given frequency and
progressively decreasing amplitude is generated.
• A system with appropriate dynamic response characteristics will return to the
baseline pressure waveform within one to two oscillations.
86. Determining natural frequency (Fn):
Fn = Paper speed (mm/sec)/ wavelength
Eg. Paper speed = 25 mm/ sec; wavelength = 1mm Fn
= 25/1 = 25Hz
87. When to perform FAST FLUSH TEST
Whenever the waveform seems overdamped or underdamped.
Whenever physiological changes of the patient ( increased heart rate, vasoconstriction)
place higher demand on the monitoring system.
After opening the system
Before implementing interventions or changes of interventions.
Whenever the accuracy of arterial blood pressure measurement is in doubt.
At least every 8-12 hours
89. Percutaneous Radial Artery Cannulation
26-07-2016 Dr. Vikram Naidu
89
• The radial artery is the most common site for invasive blood pressure monitoring
because it is technically easy to cannulate and complications are uncommon
• Modified Allen’s test
