four functions of the mechanical ventilator

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FOUR BASIC FUNCTIONSOF A

MECHANICAL VENTILATOR

By: Raymond Santos, BSRT


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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.


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What is a Mechanical Ventilator?

The mechanical ventilator is a machine that ventilates the lungs.


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VENTILATORS

vs.

RESPIRATORS


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Mechanical Ventilator


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Mechanical ventilators are machines.


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- 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.



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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


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A tool used to perform a certain task.



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- A device that provides fresh air.

- Performs the process of ventilation.

- Moves air in and out.



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



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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



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1. Start lung inflation

What starts lung inflationor

What initiates inspiration?



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2. Inflate the lungs

What maintains inflation or inspiration?



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3. Stop lung inflation

What stops lung inflationor what terminatesinspiration?



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4. Allow the lungs to empty

What happens duringemptying or what happensduring expiration?



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



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



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1. What starts lung inflation or what initiates inspiration?

A: Trigger Mechanism



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Trigger Mechanism

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



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Trigger Mechanism

- Pressure- Flow - Volume- Time



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2. What maintains inflation or inspiration?

A: Limiting Mechanism



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Limiting Mechanism

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



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3. What stops lung inflation or what terminates inspiration?

A: Cycling Mechanism



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

Cycling Mechanism



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

A: Expiratory Adjuncts



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

Expiratory AdjunctsMechanical Ventilator


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Breath Cycle

start maintain stop empty

INSPIRATION EXPIRATION


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start maintain stop

Breath Cycle

TRIGGER LIMIT CYCLE

machine or patient

VOLUME/PRESSURE/FLOW/TIME


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start maintain stop

Breath Cycle

TRIGGER LIMIT CYCLE

machine or patient

MANDATORY/ASSISTED OR SUPPORTED/SPONTANEOUS


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Breath TypeTRIGGER LIMIT CYCLE

1. MACHINE-CYCLEDBREATHS

Mandatory Breath

Assisted Breath

M M M

P M M


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Breath TypeTRIGGER LIMIT CYCLE

2. PATIENT-CYCLEDBREATHS

Supported Breath

Spontaneous Breath

P M P

P P P


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Mode

How a ventilator, ventilates a patient

Breath types given or allowed

or


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Mode

Volume Ventilation

or

Pressure Ventilation


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


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


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“The RCPProvides Care

By givingInspiration”


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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

four functions of the mechanical ventilator

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