mechanical ventilators

Ventilation

Ventilation: Ventilation or breathing is the process of
moving air into and out of the lungs.

Mechanical ventilation: It is a process of giving
artificial respiration through the device “Mechanical
ventilator”.

Mechanical ventilator

 It is a device to

inflate the lungs

artificially by

positive pressure.

Goals of Mechanical Ventilation

 Adjust alveolar ventilation
pH, PaCO2

 Improve oxygenation
Assess with pulse oximetry

 Decrease work of breathing

Indications for mechanical ventilation

 Cardiac diseases:-
Cardiogenic shock.
 Central Nervous system diseases:-
 Cerebral trauma.
 Cerebrovascular accident.
 Spinal cord injury.

 Neuro muscular diseases:-
Guillian –Barre syndrome.
Multiple sclerosis.
Poliomyelitis.
 Musculoskeletal diseases:-

Kyphoscoliosis.
Myasthenia gravis

 Others:-

Trauma like rib fractures, head injury, facial
trauma.
Surgery like cardiac surgery, pulmonary and gastro
intestinal surgery.

Clinical Indicators
Respiratory assessment
 Respiratory rate > 35 bpm
 Negative inspiratory force < -25 cm H2O
 Vital capacity < 10 ml/kg
 Minute ventilation < 3 lpm or > 20 lpm

Gas exchange
 PaO2 < 60 mm Hg with FiO2 > 50%
 PaCO2 > 50 mm Hg (acute) and pH < 7.25

Types of Mechanical ventilators

 Negative-pressure ventilators

 Positive-pressure ventilators

Negative-pressure ventilators

 Negative pressure applied to
chest wall increases the volume
of the thoracic cage
 Mimics spontaneous ventilation
 Negative intrathoracic pressure
gradient causes air to enter lungs
 No need for artificial airway
 Used mainly for chronic care of
patients with neuromuscular
disorders
 Examples: iron lung, pulmowrap,
chest cuirass

Positive-pressure ventilators

 Intrathoracic pressure
remains positive throughout
respiration
 Force oxygen into the
patients lungs through an
endotrechial or
tracheostomy tube to
initiate respiration.
 Gas is distributed to non-
dependent, less-perfused
lung regions

Terms related to mechanical
ventilation


Respiratory rate (f): Number of breaths per minute (10 to 20 bpm).
 Tidal volume (VT): Volume of air inhaled /exhaled during each respiratory

cycle ( 7 to 12 ml/kg).
 Minute ventilation (VE): Volume of air expired per minute. (VE=VT x f;
6 to 8L/min).
 Fraction of inspired oxygen(FIO2) - :amount of oxygen delivered to the
patient. It can range from 21% (room air) to 100%.


 I:E Ratio - The inspiratory time compared to the
expiratory time; I + E = total cycle time. (1:2 or less).
 Maximal Inspiratory pressure (MIP): Maximal
negative pressure generated during inhalation.(15
-20cmH2O)
 Flow rate: Flow rate is the speed with which the tidal
volume is delivered. (40 to 100 L/min).

 Cycling: what cycles, or changes, the ventilator
from one phase of the respiratory cycle to the
other. (volume, time, pressure, flow ).
 Positive end expiratory pressure(PEEP): keeps the
air way open at the end of expiration ; 5 to 20 cms
of H2O.

Classification of PPV

Pressure cycled ventilators- ventilator pushes air

until a preset pressure is reached. It is used for

short periods such as in the post anesthesia care

unit and for respiratory therapy.

 Volume- cycled ventilator: ventilators pushes air
into the lungs until preset volume is delivered.
 Time-cycled ventilators: ventilators pushes air into
lung until a preset time has elapsed. It is used
primarily in pediatric and neonatal population.

Modes of Mechanical ventilation

Mode - how the machine will ventilate the patient
in relation to the patient's own respiratory efforts.

The manner or method of support provided by the
ventilator.

ASSIST CONTROL MODE(AC)

• Most commonly
• As a resting mode, in which ventilator takes over
the work of breathing for the client.
• Machine initiated and /patient initiated breaths.
• A preset tidal volume and respiratory rate are
delivered.

INTERMITTENT MANDATORY VENTILATION(IMV)

 ventilator delivers a preset number of mechanical
breaths.
 allows the client to breath spontaneously in
between with no assistance from the ventilator
and at varying tidal volume.

SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION

(SIMV)

 Delivers preset breaths that are synchronized
with the patient’s spontaneous breaths.
 preferred mode of weaning.

INVERSE RATIO VENTILATION (IRV)

 Normal inspiratory :expiratory ratio is reversed to
2:1 or greater (the maximum is 4:1).
 Longer inspiratory time increases the amount of
air in the lungs at the end of expiration
 Improves oxygenation by reexpanding collapsed
alveoli.

PRESSURE SUPPORT VENTILATION (PSV)

 Preset pressure augments the patient's
spontaneous inspiration effort and decreases the
work of breathing
 Patient completely controls the respiratory rate
and tidal volume.

CONTINUOUS POSITIVE AIRWAY PRESSURE (CPAP)

 Keeps the alveoli open during inspiration and prevents
alveolar collapse during expiration.
 Used in the spontaneous breathing patient.
 Used as a method for weaning patients from
mechanical ventilation.
 Improves gas exchange and improves oxygenation.
 Normal range for CPAP is 5 to 15 cm of H2O.

Low pressure alarm
triggered by air leaks.
Causes
 Patient disconnection

 Circuit leaks -mainline connections to humidifiers,

filters
 Exhaled valve leaks: leaking valves, improperly

connected valves
 Airway leaks: inadequate cuff inflation, leak in pilot

balloon, rupture of tube /cuff

High airway pressure
Triggered when resistance to ventilation is high
Causes
 Ventilator problems:
Inappropriate settings, excessive tidal volume, ventilator malfunction – rare
 Circuit problems
Fluid pooling in circuit/ filter,kinking of circuit
 Endotracheal tube obstruction
Due to sputum, kinking, biting
 Increased airway resistance
Bronchospasm, decreased respiratory system compliance, decreased chest
wall compliance

Apnea alarms
Activated when no exhalation is detected for a selected
time period (e.g., 20 seconds)
causes
 Patient apnea, disconnection, system leaks,

inadequate machine sensitivity,
 Inappropriately set apnea parameters

 Can be accompanied by low pressure / low minute

ventilation alarms

Complications of positive pressure
ventilation. (PPV)
 Pneumothorax:Pleural pressure increases, and collapses
the lung, causing Pneumothorax.
 Volu-pressure trauma/Barotrauma: the lung injury that
occurs when large tidal volumes are used to inflate non
compliant lungs (eg.ARDS). This results in alveolar
fracture and movement of proteins and fluid into the
alveolar spaces.

 Alveolar hypoventilation: caused by inappropriate
ventilator setting, leakage of air from ventilator
tubing or around ET tube and tracheotomy cuff,
lung secretions or obstruction, and low ventilation
perfusion ratio.

 Alveolar hyperventilation: Respiratory alkalosis
can occur if the respiratory rate and tidal volumes
are set too high.
 Ventilator-associated Pneumonia: because ET or
tracheostomy tube bypasses normal upper air way
defenses.

 Sodium and water imbalance: fluid retention
occurs after 48 to 72 hours of PPV. It is associated
with decreased urinary out put increased sodium
retention. Fluid balance changes is due to the
decreased cardiac output.

 Neurologic system: Increased intrathoracic pressure
impedes venous drainage from the head. This
increases the cerebral blood volume and causes a
rise in intra cranial pressure.
 Gastro intestinal system: the ventilated patient is at
the risk of developing stress ulcers and GI bleeding.

ROLE OF NURSE IN
CARE OF MECHANICALLY
VENTILATED PATIENT

Hand Hygiene

• Wash hands before  Use sterlium or
direct contact. 40% of alcohol based
infections are hand rub in
transmitted by the between
hands of Hospital staff procedure or as
required.

Recording of vital signs:

• Record vital signs. {Assess for hypotension, tachycardia,
Tachypnoea }

• Observe respiratory pattern & Auscultate lung sounds.

• Observe for breathing pattern in relation to ventilatory cycle.

• Assess for changes in mental status and LOC.

• Continuous pulse oximetry.

• Observe ABG for abrupt changes or deterioration as required.

Endotracheal tube care:
• Introduce an oropharyngeal airway.
• Maintain inflation of the cuff at 15 to 20 mmHg.
• Institute Endotracheal suctioning as appropriate.
• Administer humidified oxygen before suctioning
to loosen secretions.
• Change Endotracheal tapes every 24 hours.
• Inspect the skin and oral mucosa.

• Stop feeding during 30 – 60 minutes before
suctioning & chest physiotherapy.
• Observe the type, color & amount of
secretion, notify the changes.
• Avoid drawing of arterial blood sample
immediately after suctioning.
• Watch for side effects: hypoxemia,
bradycardia, hypotension.

Oral hygiene:

• Provide careful oral hygiene

• Apply lubricant to lips to prevent drying, cracking
and excoriation.
• Rotate the ET tube from one corner of mouth to the
other side atleast every 24 hours.

Arterial Blood Gas analysis:
• ABG reflects oxygenation adequacy of gas
exchange in the lungs & Acid-base status.
• Avoid taking sample immediately after
suctioning, nebulisations and baging.
• While drawing blood prevent entry of air in
syringe.
• Send immediately ABG sample to laboratory..

Maintain Nutritional need

Basal energy expenditure calculation
[Harris Benedict equation]
Men : 66.47 + (13.75×W) + (5×H) - (6.76 ×A) Kcal/Day
Fem. : 65.51 + (9.56×W) + (1.58×H) - (4.68 ×A) Kcal/Day
[W=Weight of Pt., H=Height of Pt., A=Age of Pt.]
# High protein, High fat & Low carbohydrates diet can be
beneficial.
# Add mineral supplements to the diet especially magnesium &
phosphorus. These are essential for energy production &
respiratory muscle function.

Positioning:
• Turn and reposition the patient every 2nd
hourly.
• Positioning prevents complications such as
pneumonia and atelectasis.

Personal hygiene:
• Frequent oral hygiene must be done.
• Eye care to be given every 4th hourly to prevent
corneal ulcers and dryness of conjunctiva.
• Provide skin care.
• Provide catheter care using sterile technique.

Allaying anxiety & fear:
• Explain all the procedures to the patient &
relatives to win their confidence.
• Talk and clear the doubts of patient &
attainders. Never ignore there feelings.
• Use therapeutic touch.
• Encourage the family members to visit the
patient as per hospital policy.

Care of ventilator circuit:
• Keep the water level in humidifier in normal
limit.
• Humidification during mechanical ventilation
required to prevent hypothermia, inspissations'
of airway secretions, destruction of airway
epithelium & atelectasis.
• A heated humidifier should be set to deliver an
inspired gas temperature of 33 -/+ 2˚C.
• The temperature of inspired gas should not
exceed 37˚C at the airway threshold.
• Sterile water should be used only.

• Condensation from the patient circuit should be
considered infectious waste and should never be
drained back in to the humidification reservoir.
• Change the circuit when it is visibly soiled or
mechanically malfunctioning.
• Bacterial filters should not be used for more than 48
hours.
• Use universal precautions when involved in circuit
changes.

Care of ventilator alarms:
• Never Shut Alarms Off – Alarm system must be
activated and function at all time. It is acceptable
to silence alarms for a preset delay while
suctioning and during oxygen flush before
suctioning.

• If equipment failure is suspected and unable to
determine the cause of alarm, Manually
ventilate the patient with resuscitation bag until
the problem is corrected.

VENTILATOR CARE BUNDLE
Acc to IHI “bundle” is a group of evidence –based
care components for a given disease that ,when
executed together ,may result in better outcomes
than if implemented individually.

VENTILATOR CARE BUNDLE
It includes :

DVT prophylaxis(unfractioned heparin,elastic
stockings,pneumatic compression,elevation of
affected extrimity,gentle foot & leg exercise,fluid
administration)

GI prophylaxis(H2 blocker /proton pump inhibitor)

Head of bed elevated to 30-45

Daily sedation vacation /daily spontaneous
breathing trial
Skin safety (manage pressure,adequate
nutrition,wound assessment & wound care)
Fall prophylaxis

mechanical ventilators

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