Monitoring Ventilated
Patients
Dr.T.Sureshkumar MD, IDCCM, EDIC
Consultant Intensivist
Kovai Medical Center and Hospitals
SCOPE OF THIS TALK
• The aim is not to make anybody expert but to guide safe and
efficient practice.
• Narrowed down to avoid major catastrophe
• Focused on graphics and hemodynamics as time limits
• Language is not a barrier here & I am not the best in English.
• My intention is not delivery but reach, so please come close to me.
• Three Phases
1. Induction
2. Maintenance
3. Weaning
• Five Monitors
1. Patient
2. Ventilator
3. Vitals
4. Images
5. Labs
Why Ventilation ??
Need for Ventilation
Pulmonary
Extra Pulmonary
Abnormal
lung
Normal
lung
Air way issues
High
resistance
Parenchymal issues
Poor
Compliance
Start with…Intubation
1st - Look your Patient
Look & check air entry
1. Abnormal breathing
Abdomen distending
Irregular chest rise
Hear
1. Five point auscultation
2. Abnormal sounds –wheeze, crepts
And Yes your tube in right place…
Patient
• At induction phase Pt will be in control ventilation
• During maintenance Pt will trigger and may attempt his own
breath
• Care should be taken whether he tolerates ventilator
• Our settings adequate for him
• Asynchrony
• Disease worsening
• During Weaning :
• Important to communicate with Patient
• Don’t ignore his needs
nd
2
– Check Ventilator
• Two important things
1. What the ventilator gives to
the patient
2. How the lung accepts it.
1.Basic setup
a) Oxygenation ( FiO₂)
b) Ventilation (RR, Vt)
c) Desired mode
d) Recruitment (PEEP) if needed.
2.Scalars and loops
3.Parameters
4.Alarm settings
Ventilator Graphics
• Scalar and Loops are windows to Lung-Ventilation Mechanics
• So all modern ventilators equipped with Graphical representations.
• Gives a quick clue for problem even from a distance.
• On evaluation can diagnose specific disorder and helps in preventive
measures.
• Scalars and Loops:
• Scalars: Plot pressure, volume, or flow against time. Time is the
x-axis.
• Loops: Plot pressure or flow against volume. (P/V or F/V). There
is no time component.
Volume Modes
Volume Control
SIMV (Vol. Control)
Pressure Modes
Pressure Control
PRVC
SIMV (PRVC)
SIMV (Press. Control)
Pressure Support
Volume Support
Pressure Time
Plateau Pressure
Airway Pressure
Mean airway
Pressure
Increased Airway Resistance
PIP
Decreased Compliance
PIP
Raw
Pplat
Pplat
•A -Increase in airway resistance (Raw)
causes the PIP to increase, but Pplat
pressure remains normal.
•B-A decrease in lung compliance causes
the entire waveform to increase in size.
(More pressure is needed to achieve the
same tidal volume). The difference between
PIP and Pplat remains normal.
Air-Trapping (Auto-PEEP)
•An acceptable amount of auto-PEEP
should be < 5cm H2O
Flow Time
Volume
Pressure
Wheeze
&
Bronchodilator Response
Improved Peak Flow
•
The area of no flow
indicated by the red line
is known as a “zero-flow
state”.
•
This indicates that
inspiratory time is too
long for this patient.
Is it Inadequate insp. Time??
No . In spontaneous mode it is
decided by the patient
Volume Time
Air-Trapping or Leak
Pressure / Volume loops
Dynamic
Compliance
Over distention/DHI
•As airway resistance increases, the loop will become wider.
•An increase in expiratory resistance is more commonly seen.
Increased Compliance
Example: Emphysema
Decreased Compliance
Example: ARDS, CHF, Atelectasis
Lung Compliance Changes and the PV Loop
Preset VT
Volume Targeted Ventilation
COMPLIANCE
Increased
Normal
Decreased
Volume (mL)
Paw (cm H2O)
PIP levels
Increased
Normal
Decreased
Pressure Targeted Ventilation
COMPLIANCE
VT levels
Lung Compliance Changes and the PV Loop
Volume (mL)
Paw (cm H2O)
Preset PIP
A Leak
The expiratory portion of the
doesn’t return to baseline. This
indicates a leak.
loop
Pressure / Volume Loop
The shape of the inspiratory portion of the curve will match
the flow waveform.
A Leak
Normal
If there is a leak, the loop will not meet at the starting point
where inhalation starts and exhalation ends. It can also
occur with air-trapping.
Airway Obstruction
Flow Starvation
The inspiratory portion of the pressure wave shows a “dip”, due to
inadequate flow.
Hemodynamics
• Important to understand Thoracic
physiology – Heart & Lung.
• Normally the Negative Plural Pressure
augments the venous return to RA and
thus increases CO
•
So Output increases during
Inspiration than Expiration.
• But in case of Positive Pressure it
differs
The systolic pressure and the pulse
pressure are maximum (SPmax and
PPmax) during inspiration and
minimum (SPmin and PPmin) during
the expiratory period.
In hypovolemic conditions
(1) RV preload decreases because
the increase in pleural pressure
induces a compression of the
superior vena cava
(2) an increase in intramural right
atrial pressure
(3) RV afterload increases because
pulmonary capillaries are compressed.
(4) The increase in alveolar pressure squeezes out the
blood contained in the capillaries toward the left side
of the heart.
(5) The increase in pleural pressure induces a
decrease in left ventricular afterload
In hypervolemic conditions
The vena cava and right atrium are
poorly compliant and compressible and
hence relatively insensitive to changes
in pleural pressure
(4) Each mechanical breath increases
pulmonary venous flow and left
ventricular preload
(5) The increase in pleural pressure
induces a decrease in left ventricular
afterload .
Capnography
• Measures End-tidal CO2 (EtCO2)
• Monitors changes in
• Ventilation - asthma, COPD, airway edema, foreign body, stroke
• Diffusion - pulmonary edema, alveolar damage, CO poisoning, smoke
inhalation
• Perfusion - shock, pulmonary embolus, cardiac arrest, severe dysrhythmias
• Gold Standard for confirming Intubation
• Reports quality of CPR
Normal
45
0
Normal range is 35-45mm Hg (5% vol)
Waveform
End-tidal
Ascending Phase
of Exhalation
A
Baseline
B
C
Alveolar Plateau
D
Descending phase
of Inhalation
E
Normal
45
0
Hyperventilation
45
0
Hypoventilation
45
0
45
Normal
0
Bronchospasm
45
0
SPO₂
• Works at two different wavelengths absorbed by oxy and deoxy Hb
and the gradient is used to calculate Hb saturation.
• Different models of probes available.
• Very useful to pick Pt deterioration.
• Pros :
Cons :
•
•
•
•
Mobile
All time wearable
Real time monitor
Cheap
•
•
•
•
•
Sats < 85 % are unreliable
Impedance disturbances
Picks little late
Cannot measure MetHb, SulHb
Altered with shock state, nail
polish, dyes etc
CXR
• Useful for properly locating the ET
• Diagnosing issues.
• Follow Up of Disease.
ABG
• Its out of scope for this Session.
• Check Ph
• Metabolic side(HCO3) / Respiratory Side(PCO2)
• Compensated/ Uncompensated
• Any ventilator change can alter it.
Charting
• Even the best handing over cannot replace charting
• Reviewing trends helps in Pt Dx & Mx.
Language is not a barrier here
& I am not the best in English.