3. Monitoring of Patient on Mechanical Ventilation

Report
Department of Critical Care Medicine
Kovai Medical Center and Hospital
MONITORING OF MECHANICALLY
VENTILATED PATIENT
DR.T.GOPINATHAN MD., IDCCM.,EDIC
Consultant Intensivist
Kovai Medical Center and Hospital
GOALS OF MECHANICAL VENTILATION
 Decrease the WOB and improve patient comfort
 Maintain adequate gas exchange to keep body in
relative homeostasis
OBJECTIVE
Monitoring : monere - meaning ‘to warn’
Goals of continuous monitoring :
 Baseline measurement – initial plan, reference for
future
 follow real time specific physiological values that
changes rapidly – alerts for adverse events
 Assessment of therapeutic intervention
RESPIRATORY


Monitoring gas exchange
•
Oxygenation
•
Ventilation
Monitoring lung and chest wall mechanics
•
Pressure
•
Volume
•
Flow
•
Compliance
•
Resistance
GAS EXCHANGE

Clinical signs and symptoms - Nonspecific, late

ABG

PULSE OXYMETRY

CAPNOGRAPHY

The clinical significance of hypoxia/hypercapnia
depends on Chronicity of Compensatory
mechanisms and tolerance of vital organs
PULSE OXYMETRY

Pulsatile signal generated by
arterial blood

Difference in the absorption spectra
of oxyHb and Hb.

Determines O2 saturation by
absorption spectrophotometry
PULSE OXYMETRY
 Advantages:
• Inexpensive
• Accuracy - Spo2 below 80%
• Direct measurement
• Continuous
• Non-invasive
• Pleth variability index
LIMITATIONS OF PULSE OXYMETRY
 Shape of oxygen dissociation curve
 False alarms
 Dyshemoglobinemia
 Motion artifact
 Dyes
 Skin pigmentation
 Nail polish
 Low perfusion state
 Ambient light
ABG
Advantages:
• Direct measurement of PaO2 and PaCO2
• Also gives values for acid-base status and electrolytes
Disadvantages:
• Not specific or sensitive
• Calculates saturation
• Requires invasive procedure
• Intermittent sampling - miss events
ABG
Factors influencing values:
PaO2 varies
• Age
• Altitude
• Sampling techniques: air bubble, heparin
PaCO2 remains relatively constant
OXYGENATION
Efficacy of oxygen exchange
• Alveolar gas equation
 PAO2 = PIO2 – (PaCO2/R)
• AaDO2 = PAO2 – PaO2
• Oxygenation index : PaO2/(FiO2 X Paw)
• PaO2/FiO2
VENTILATION
• PaCO2 is directly measured in blood.
• PaCO2 is a measure of ventilation - CO2 elimination
• Increased PaCO2
.
PaCO2 = VCO2/ ( Vt –Vd ) RR
CAPNOGRAPHY
•
Between ETT and expiratory limb of vent tubing
•
Expired CO2 against time
•
Healthy subjects, V/Q ≈
•
Information about RR and rhythm
•
ETT placement (obstr, discon, kinking)
•
Determine dead space, CO and PE
•
Best PEEP, PaCO2 – PET CO2 difference
1, EtCO2 ≈PaCO2
CAPNOGRAPHY
ABNORMAL EtCO2 WAVEFORMS
ASTHMA/ COPD
ABNORMAL EtCO2 WAVEFORMS
Hypoventilation
Hyperventilation
OBJECTIVES OF VENTILATOR GRAPHICS
• Describe how to use graphics to more appropriately adjust
the patient ventilator interface.
• Identify adverse complications of mechanical
ventilation.
EQUATION OF MOTION
Muscle pressure + ventilator pressure =flow
resistance pressure +Elastic recoil pressure
Pmus + PrS =
(R x Flow) + V/C
SCALARS & LOOPS
SCALARS
• Pressure vs. Time
• Flow vs. Time
• Volume vs. Time
LOOPS
• Pressure vs Volume
• Flow vs volume
MODE OF VENTILATION -> USEFUL
WAVEFORMS
Mode of
ventilation
Independent
variables
Dependent
variables
Waveforms that will be
useful
Waveforms that
normally remain
unchanged
Volume
Control/
AssistControl
Tidal volume,
RR, Flow rate,
PEEP, I/E ratio
Paw
Pressure-time:
Changes in Pip, Pplat
Flow-time (expiratory):
Changes in compliance
Pressure-volume loop:
Overdistension, optimal PEEP
Volume-time
Flow time (inspiratory)
Flow-volume loop
Pressure
Control
Paw, Inspiratory
time (RR), PEEP
and I/E ratio
Vt, flow
Volume-time and flowtime: Changes in Vt and
compliance
Pressure-volume loop:
Overdistension, optimal PEEP
Pressure-time
Pressure
support/
CPAP
PS and PEEP
Vt,and RR,
flow, I/E
Ratio
Volume- time
Flow- time
(for Vt and VE)
PRESSURE TIME
PRESSURE TIME
20
Pressure Ventilation
Volume Ventilation
Paw
cmH2O
Sec
1
2
3
4
5
6
flow
pressure
pressure
HIGH AIRWAY RESISTANCE
time
timetime
HIGH FLOW RATE
pressure
Paw(peak) = Flow x Resistance + Volume x 1/compliance + PEEP
time
INADEQUATE FLOW - VCV
30
Adequate flow
Paw
Flow set too low
cmH2O
1
-10
2
3
Time (s)
pressure
DECREASED COMPLIANCE
time
FLOW - TIME
120
INSP
Inspiration
PIFR
.
Vt
V
LPM
Te
Ti
SEC
1
2
3
4
5
6
Expiration
PEFR
120
EXH
CHANGING FLOW WAVEFORM IN VCV:
EFFECT ON INSPIRATORY TIME
120
.
V
SEC
LPM
1
-120
2
3
4
5
6
EXPIRATORY FLOW RATE AND CHANGES IN
EXPIRATORY RESISTANCE
120
.
SEC
V
LPM
-120
1
2
3
4
5
6
DETECTING AUTOPEEP
120
.
V
SEC
LPM
1
120
2
3
4
5
6
The transition from expiratory to inspiratory
occurs without the expiratory flow returning
to zero
VOLUME Vs TIME CURVE
800 ml
Vt
Inspiration
Expiration
VT
SEC
1
Ti
2
Te
3
4
5
6
LEAKS
1.2
A
VT
Liters
SEC
Leak Volume
1
2
3
-0.4
A = exhalation that does not return to zero
4
5
6
MEASUREMENT OF AUTOPEEP
800 ml
Inspiration
VT
Expiration
End Expiratory Hold
PEEP i
SEC
PEEP e
1 Ti
2 Te
3
4
5
6
LOOPS
Pressure-Volume Loop
PV Loops
VT
Volume
(mL)
Paw (cm H2O)
PIP
Flow-Volume Loop
Inspiration
Volume (ml)
Expiration
FV Loops
ASSISTED BREATH
spontaneous breath
Assisted breath
controlled breath
Expiration
Inspiration
Paw
v
cmH2O -60
40
20
0
20
40
60
PV LOOP-INCREASED RESISTANCE
PCV
DECREASED COMPLIANCE
WORK OF BREATHING
Work of Breathing
Volume (ml)
A: Resistive Work
B: Elastic Work
B
A
Pressure (cm H2O)
Essentials of Ventilator Graphics
©2000
RespiMedu
COPD
LEAK
OVERDISTENSION
VT
A = inspiratory pressure
LITERS
B = upper inflection point
0.6
C = lower inflection point
A
0.4
B
0.2
C
Paw
cmH2O
-60
-40
-20
0
20
40
60
NORMAL FLOW-VOLUME LOOPS
FV LOOP – VOLUME CONTROL
Tidal Volume
Peak Inspiratory Flow
Peak Expiratory Flow
Inspiration
Volume
Expiration
ETT OR CICUIT LEAKS
AUTOPEEP
BRONCHODILATOR RESPONSE
BEFORE
AFTER
3
3
INSP
2
2
1
1
V
LPS
V
LPS
1
1
2
2
3
3
.
.
VT
EXH
USES
• Identify mode
• Detect auto-PEEP
• Determine patient-ventilator synchrony
• Assess and adjust trigger levels
• Measure the work of breathing
• Adjust tidal volume and minimize overdistension
• Assess the effect of bronchodilator admn.
USES
• Detect equipment malfunctions
• Determine appropriate PEEP level
• Evaluate adequacy of inspiratory time in pressure control
ventilation
• Detect the presence and rate of continuous leaks
• Determine appropriate Rise Time
No monitoring device, no matter how
simple or complex, invasive or noninvasive, inaccurate or precise will
improve outcome unless coupled to a
treatment, which itself improves
outcome
Thank you

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