Four Functions of the Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

FOUR BASIC FUNCTIONSOF A

MECHANICAL VENTILATOR

By: Raymond Santos, BSRT

VVEE = V = VTT x x ff

C = C = VV PP

What is a Mechanical Ventilator?

An automatic mechanical device designed to provide all or part of the work the body must produce to move gas into and out of the lungs.

VVEE = V = VTT x x ff

C = C = VV PP

What is a Mechanical Ventilator?

The mechanical ventilator is a machine that ventilates the lungs.

VVEE = V = VTT x x ff

C = C = VV PP

VENTILATORS

vs.

RESPIRATORS

VVEE = V = VTT x x ff

C = C = VV PP

VVEE = V = VTT x x ff

C = C = VV PP

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Mechanical Ventilator

Mechanical ventilators are machines.

VVEE = V = VTT x x ff

C = C = VV PP

- A machine is defined as a system of related elements designed to alter, transmit and direct applied energy in a predetermined manner to perform useful work.

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Mechanical Ventilator1. Drive Mechanism - Gas Powered

- Electrical2. Control Scheme - Control Circuit

- Variables- Modes

3. Output - Volume- Pressure- Flow

4. Alarm Systems - Input/Output- Control Circuit

VVEE = V = VTT x x ff

C = C = VV PP

A tool used to perform a certain task.

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

- A device that provides fresh air.

- Performs the process of ventilation.

- Moves air in and out.

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Its primary purpose is to provide the patient with the right volume of fresh air in the lungs.

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Whether manual or mechanical, a ventilator must perform 4 Basic Functions.

1. Start lung inflation2. Inflate the lungs3. Stop lung inflation4. Allow the lungs to empty

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

1. Start lung inflation

What starts lung inflationor

What initiates inspiration?

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

2. Inflate the lungs

What maintains inflation or inspiration?

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

3. Stop lung inflation

What stops lung inflationor what terminatesinspiration?

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

4. Allow the lungs to empty

What happens duringemptying or what happensduring expiration?

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Attempting to answer thesequestions would certainlygive the Respiratory Care Practitioner hints on the capabilities of a particular mechanical ventilator.

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

The answers could even describe the different modes available that the RCP can use in ventilating the patient.

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

1. What starts lung inflation or what initiates inspiration?

A: Trigger Mechanism

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Trigger Mechanism

- Patient ( Assist/IPPB)- Machine (Control/CMV)- Both (Assist/Control)- Clinician (Manual)

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Trigger Mechanism

- Pressure- Flow - Volume- Time

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

2. What maintains inflation or inspiration?

A: Limiting Mechanism

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Limiting Mechanism

- Pressure (Pressure-Limited/PCV)- Volume (Volume-Limited)- Flow (Flow-Limited)

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

3. What stops lung inflation or what terminates inspiration?

A: Cycling Mechanism

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

- Pressure (Pressure-Cycled)- Volume (Volume-Cycled)- Flow (Flow-Cycled)- Time (Time-Cycled)

Cycling Mechanism

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

4. What happens during emptying or what happens during expiration?

A: Expiratory Adjuncts

Mechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

- ZEEP- NEEP- PEEP/CPAP/APRV- Expiratory Resistance- Inspiratory Hold

Expiratory AdjunctsMechanical Ventilator

VVEE = V = VTT x x ff

C = C = VV PP

Breath Cycle

start maintain stop empty

INSPIRATION EXPIRATION

VVEE = V = VTT x x ff

C = C = VV PP

start maintain stop

Breath Cycle

TRIGGER LIMIT CYCLE

machine or patient

VOLUME/PRESSURE/FLOW/TIME

VVEE = V = VTT x x ff

C = C = VV PP

start maintain stop

Breath Cycle

TRIGGER LIMIT CYCLE

machine or patient

MANDATORY/ASSISTED OR SUPPORTED/SPONTANEOUS

VVEE = V = VTT x x ff

C = C = VV PP

Breath TypeTRIGGER LIMIT CYCLE

1. MACHINE-CYCLEDBREATHS

Mandatory Breath

Assisted Breath

M M M

P M M

VVEE = V = VTT x x ff

C = C = VV PP

Breath TypeTRIGGER LIMIT CYCLE

2. PATIENT-CYCLEDBREATHS

Supported Breath

Spontaneous Breath

P M P

P P P

VVEE = V = VTT x x ff

C = C = VV PP

Mode

How a ventilator, ventilates a patient

Breath types given or allowed

or

VVEE = V = VTT x x ff

C = C = VV PP

Mode

Volume Ventilation

or

Pressure Ventilation

VVEE = V = VTT x x ff

C = C = VV PP

To begin understanding how a mechanical ventilator works, the RCP must start by knowing that it is a machine.

VVEE = V = VTT x x ff

C = C = VV PP

And like any machine, the mechanical ventilator has a purpose – to ventilate.

VVEE = V = VTT x x ff

C = C = VV PP

“The RCPProvides Care

By givingInspiration”

VVEE = V = VTT x x ff

C = C = VV PP

REFERENCES

1. McPherson S.P.: Respiratory Care Equipment, ed 5, 1995, St. Louis, Mosby2. Scanlan et al: Egan’s Fundamentals of Respiratory Care, ed. 6, 1995, St. Louis, Mosby3. Barnes T. A.: Core Textbook of Respiratory Care Practice, ed 2, 1994, St. Louis, Mosby4. Dupois Y.G.: Ventilator “Theory and Clinical Application”, ed. 2, St. Louis, Mosby5. Kirby R. R.et al: Clinical Applications of Ventilatory Support, revised edition, 1990, New York, Churchill Livingstone6. Chang D. W.: Clinical Application of Mechanical Ventilation, 1997, New York, Delmar Publishers