Make your own free website on Tripod.com
MECHANICAL VENTILATORS : The Very Basics !!!
 VENTILATORS

The primary function of the ventilator or respirator is used as a means to inflate the lungs and open the alveoli.

What are the Indications ??

*	They cater for adult patients with  ARDS [ Acute Respiratory Distress Syndrome ]
	:- This is a syndrome where the patient has insufficent surfactans been produced.

*	Patients who need to undergo Thoracic / Abdominal surgery and where the Respiratory 	System need to be surpressed.

*	Patients with abnormal Respiratory Regulatory Mechanism.
	:- This is normally caused by ^ ICP [Increased  Intra-Cranial Pressure ]

*	When there is a  need to introduce Bronchodilators, Antibiotics and Mucolytic Agents.
	:- One of the common ailment such as Severe Asthmatic Patients.

6 CONTROLLING MODES OF VENTILATION

1.	Controlled Mechanical Ventilation [ CMV ]

	This is where the breathing frequency is completely determined by the ventilator - also 	known as Mechanical Breathing. Any inspiratory by the patient is completely ignored.

2.	Assissted Ventilation

	This is a Mechanical Aid in breathing when the patient initiates the frequency of breaths. 	The machine is set to be sensitive to a certain strength of negative inspiratory effort. This 	is useful for patients who have Spontaneous but Inadequate Ventilation. [ Inadequate 	Ventilatory Capacity ] 

3.	Controlled and Assissted Ventilation

	Here the machine delivers controlled breaths at a given fail-safe frequency that takes over 	if the patient fails to trigger assissted breaths fast enough.

4.	Intermittent Mandatory Ventilation [ IMV ]

	This is a controlled mechanical breath placed between spontaneous breaths. It 	encourages patients to use and strengthen their respiratory muscles while providing 	periodic breaths that helps prevent atelectasis. The number of programmed breaths can 	be gradually reduced until the patient can be discontinued from the ventilator. [ Weaning 	Off ]

5.	Synchronized Intermittent Mandatory Ventilation [ SIMV ]

	Similar ti IMV, except that when a mandatory breath with its preset tidal volume is due, 	it is delivered in synchrony with the next spontaneous inspiratory effort.	

6.	Continuous Positive Airway Pressure [ CPAP ]

	Here the constant pressure is above 0 (ZERO ), maintained in the airways throughout 	the respiratory cycle during spontaneous breathing. It helps to hold small airways and 	alveoli open.



WHAT ARE THE TYPES OF VENTILATORS AVAILABLE ???

~	Pressure Cycled	

	A device designed to deliver gas until a preset pressure is reached, regardless of volume 	delivered.

	It pushes gas into the lungs until a predetermined pressure is reached within the 	tracheobronchial tree.

	When this pressure is reached, the driving force of the ventilator shuts off.

~	Volume Cycled

	A device for delivering a preset volume, within certain limits, regardless of the pressure 	required.

	It pushes gas into the lungs until a certain predetermined tidal volume is delivered before 	terminating inspiration.

	It prevents the ventilator from pushing a high tidal volume into obstructed or non-	compliant lungs, which could damage or even rupture the lung tissues.

~	Time cycled

	A device designed to deliver gas until a preset time has passed, regardless of the pressure
	or volume delivered.

	tidal volume is regulated by adjusting the length of inspiration and the flow of the 	pressurized gas.

~	Pressure/Time Cycled

	A device that delivers a primary flow of gas until a preset pressure is reached and then a 	secondary gas provides a continuation of timed flow when airways are at a maximum 	distension.

HAVE YOU HEARD OF  “ PEEPS “  AND “ SIGHS “  ???

> 	POSITIVE END EXPIRATORY PRESSURE

	This can be applied at the end of expirarion so that the pressure in the airways never 	drops below a selected level., usually between 5 to 15 cm H2O of pressure. It holds small 	airways and alveoli open and thereby increae functional residual capacity and limit 	atelectasis. 

>	SIGHS

	It provides larger tidal volume and will inflate more alveoli than normal breaths and
	therefore help prevent atelectasis. The ventilator is normally programmed to deliver 6 
	sighs per hour. A pressure limit is set for the delivery of sighs.

ALARMS !! ALARMS !! ALARMS !!

+	HIGH PRESSURE ALARMS

	This alarms sound whenever the preset limit is reached, and delivery of the full tidal 	volume is aborted.

+	LOW PRESSURE ALARMS

	this alarms sounds whenever the pressure within the system drops precipitously.


VENTILATOR SETTINGS

	TIDAL VOLUME :  10 - 15ml/kg body weight ( 500ml - 1000ml )

	RESPIRATORY RATE  :  10 - 14 breaths/min

	INSPIRATORY / EXPIRATORY RATIO  :  1  :  2  to allow optimal and passive emptying 							of the lungs.
	OXYGEN CONCENTRATION :  Vary with patients ABG and also types of ventilator


NURSING CARE

It is important to know  and understand the following :-

#	Why the patient requires ventilatory assistance ?

#	How the particular ventilator with its special settings alters the patient’s 	physiology and ventilatory pattern and control ?

#	What dangers and possible complications accompany the use of the 	ventilator ?

#	The nursing assessments and interventions necessary for comprehensive 	patient care ?


NURSING RESPONSIBILITIES

1.	Ensure all tubings are connected snugly.

2.	Fill the humidifier container with sterile water to the level marked. 

3.	Check the functioning of the ventilator with a test lung.

4.	Set the ventilator according to the patient’s clinical status.

5.	Ensure the ventilator tubings are properly aligned.

6.	Observe the patient regularly :-
				Respiratory rate and rhythm.
				Chest expansion synchronizes with each 										inspiratory trigger.
				Vital signs, skin colour and mental status.

BACK