Monitoring Ventilated Patients

Dr.T.Sureshkumar MD, IDCCM, EDIC

Consultant IntensivistKovai 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

Air way issues Parenchymal issues

Normal lung

Abnormal lung

High resistance

Poor Compliance

Start with…Intubation

1st - Look your PatientLook & check air entry

1. Abnormal breathing Abdomen distendingIrregular chest rise

Hear 1. Five point auscultation2. 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

2nd – 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 Pressure Modes

Volume Control SIMV (Vol. Control)

Pressure ControlPRVCSIMV (PRVC)SIMV (Press. Control)

Pressure SupportVolume Support

Pressure Time

Airway Pressure

Plateau Pressure

Mean airway Pressure

Increased Airway Resistance

Raw

PIP PIP

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.

Decreased Compliance

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 loopsDynamic Compliance

Over distention/DHI

•As airway resistance increases, the loop will become wider.

•An increase in expiratory resistance is more commonly

seen.

Example: Emphysema Example: ARDS, CHF, Atelectasis

Increased Compliance Decreased Compliance

Lung Compliance Changes and the P-V Loop

Lung Compliance Changes and the P-V Loop

Volume (mL)

PIP levels

Preset VT

Paw (cm H2O)

COMPLIANCEIncreasedNormalDecreased

COMPLIANCEIncreasedNormalDecreased

Volume Targeted Ventilation

Lung Compliance Changes and the P-V Loop

Lung Compliance Changes and the P-V Loop

Volume (mL)

Preset PIP

VT

levels

Paw (cm H2O)

COMPLIANCEIncreasedNormalDecreased

COMPLIANCEIncreasedNormalDecreased

Pre

ssu

re Ta

rgete

d

Ven

tilatio

n

A Leak

The expiratory portion of the

loop doesn’t return to baseline.

This indicates a leak.

Pressure / Volume Loop

The shape of the inspiratory portion of the curve will

match the flow waveform.

Normal

A Leak

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

The inspiratory portion of the pressure wave shows a

“dip”, due to inadequate flow.

Flow Starvation

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 becausethe increase in pleural pressure induces a compression of thesuperior 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

A

B

CD

EBaseline

Ascending Phase of Exhalation

Alveolar Plateau

Descending phase of Inhalation

End-tidal

0

45

Hypoventilation

45

0

Hyperventilation

45

0

Normal

45

0

Normal

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 :• Mobile• All time wearable• Real time monitor• Cheap

Cons :• 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.