BASIC VENTILATOR
SETTINGS OR WORKING PRINCIPLES
1.Mode :in majority of
cases the mode will be assist /control (A/C) or Synchronised Intermittend
Mandatory Ventilation. (SIMV).
2.Fraction of Inspired Oxygen (FiO2):FiO2
of 100% is safe when used for one or two hours
3.Tidal
Volume (TV):It is the gas delivered to the patient during each
ventilator breath. The tidal volume setting is established based on the
patients age , weight, breathing, frequency, clinical conditions and the mode
of the ventilator chosen. Normally it is 5-15ml/Kg body Wt.
4.Respiratory rate
: Number of breaths the ventilator delivers per minute –usual setting is
4-20breaths /min.
5. I:E ratio:
The I:E ratio is the duration of inspiration compared to the duration of
expiration. Normally I:E ratio is maintained at 1:2. In special circumstances I:E ratio may be set differently For example,
in patients with emphysema, asthma I:E ratio is 1:3 or 1:4.
6.Flow Rate :it
is the speed with which tidal volume is delivered –usual setting is 40-100 litre/min.
7.Humidification and airway temperature:Humidifier
should be kept close to body temperature (35-37C)at the patient Y-tube where
the temperature is monitored .Humidified air reduces dryness of mucosa.
Alarms
The
patient life depends upon correct working of the ventilator .To protect the
patient ventilators are equipped with a system of alarms. The important alarm
triggered are
1.Low exhaled volume alarm
: This alarm indicates that there is a loss of tidal volume or a leak in the
system (nurse should rapidly check the ventilator tubings for disconnection and
airway cuff).
2.High pressure alarm:
Anything that increases the airway resistance can trigger the high pressure
alarm..For example coughing .biting the tube ,secretion in the airway, water in
the tubings etc
3.Ventilator failure alarm:Most
ventilator having the alarm that will sound in the event of mechanical failure.Alarms are battery powered in the event
of the electrical failure.
Special BASIC VENTILATOR SETTINGS Modification
1.Sigh volume:The
sigh mode delivers occasional large breaths to patients mimicking normal
breathing pattern to minimise or prevent atelectasis.
2.Negative End Expiratory pressure(NEEP):It
is used to apply negative pressure on the breathing circuit on exhalation.
3.Positive End Expiratory Pressure (PEEP):PEEP
is used in mechanical ventilation to apply positive pressure during
expiration.The application of PEEP prevents alveolar collapse during expiration
by maintaining them open at end exhalation .PEEP is used to
a.
Increase functional residual capacity.
b.
Re-expand collapsed and partially collapsed alveoli.
c.
Improve oxygenation so that toxic concentrations of oxygen are no longer
required.
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