This document provides information about mechanical ventilators. It begins by defining mechanical ventilation as the process of using an external device to move gas in and out of the lungs. It then describes the two main types as positive pressure ventilation, which pushes air into the lungs, and negative pressure ventilation, which sucks air out. The majority of the document focuses on positive pressure ventilators, describing their history, components, modes of operation like volume-cycled and pressure-cycled, settings, indications for use, complications, and the nurse's role in monitoring patients and the equipment.
2. Introduction
A ventilator is a machine which is designed to
mechanically move breathable air into and out of the
lungs, to provide the mechanism of breathing for a
patient who is physically not able to breathe sufficently.
3. Mechanical ventilation
Mechanical ventilation can be defined as the
technique through which gas is moved toward and from
the lungs through an external device connected directly
to the patient.
There are two main types: positive pressure
ventilation, where air (or another gas mix) is pushed
into the trachea, and negative pressure ventilation,
where air is, in essence, sucked from the lungs.
4.
5. Types of Ventilator
Positive Pressure Ventilator
Negative Pressure Ventilator
Humans, like most mammals, breathe by
negative pressure breathing
9. Positive pressure Ventilator
The design of the modern positive-pressure ventilators were
based mainly on technical developments by the military during
World War II to supply oxygen to fighter pilots in high altitude.
Such ventilators replaced the iron lungs as safe endotracheal
tubes with high-volume/low-pressure cuffs were developed.
The popularity of positive-pressure ventilators rose during the
polio epidemic in the 1950s
Positive pressure through a tracheostomy tube led to a
reduced mortality rate among patients with polio and
respiratory paralysis.
10. Indications for Mechanical Ventilation
Bradypnea or apnea with respiratory arrest
Acute lung injury and the acute respiratory distress syndrome
Tachypnea (respiratory rate >30 breaths per minute)
Arterial partial pressure of oxygen (PaO 2) with a supplemental
fraction of inspired oxygen (FIO 2) of less than 55 mm Hg
Hypotension
Acute partial pressure of carbon dioxide (PaCO 2) greater than
50 mm Hg with an arterial pH less than 7.25
Chronic Obstructive Pulmonary Disease.
11. Cont..
Hypotension including sepsis, shock, CHF.
Obtundation or coma
Neuromuscular disease
Guillian –Barre syndrome
Multiple sclerosis
Poliomyelitis
Nervous system disease
Cerebral trauma
Cerebrovascular accident
Spinal cord injury.
12. Types of positive pressure ventilators
Four types of positive pressure ventilators.
Volume-cycled ventilators
Pressure-cycled ventilators
Flow-cycled ventilators
Time-cycled ventilators
13. Volume-cycled ventilators
Volume-cycled ventilators – Ventilators pushes air into
lungs until a preset volume of gas/air or “tidal” volume is
delivered and then allow passive exhalation.
This type is ideal for patients with acute respiratory
distress syndrome or bronchospasm, since the same tidal
volume is delivered regardless of airway resistance or
compliance.
14. Pressure-cycled ventilators
Pressure-cycled ventilators- Ventilator pushes air into lung
until a preset airway pressure limit is reached and allow
passive exhalation.
The benefit is a decreased risk of lung damage from high
inspiratory pressures.
The disadvantage is that the tidal volume delivered can vary
with changes in lung resistance and compliance if the patient
has poor lung compliance and increased airway resistance.
This ventilator is often used for short-term therapy.
15. Flow-cycled ventilators
Flow-cycled ventilators deliver oxygenation until a preset
flow rate is achieved during inhalation.
Time-cycled ventilators
Time-cycled ventilators deliver oxygenation over a preset
time period. The ventilators are not used as frequently as
the volume-cycled and pressure-cycled ventilators.
It is used primarily in pediatric and neonatal population.
16.
17.
18.
19. PP (Plateau Pressure) = Pressure applied to small airways
and alevoli in end inspiratory Pause to prevent volutrauma.
P PEAK or Peak inspiratory pressure (PIP) - It is highest
level of pressure applied to lung during inhalation or it is
sum of the plateau pressure (pressure used to keep air in
the lungs) and pressure used to overcome airway
resistance (elastic recoil of the lungs and chest wall,
friction, etc.). In other words: Ppeak = Pplat + Presistance.
Consequently, Pplat can never be more than Ppeak, because
there’s always going to be intrinsic resistance which must
be overcome by Presistance.
20.
21. Sensitivity /Trigger
Trigger sensitivity should be set at a high sensitivity (i.e.
a low number), to reduce the ventilator response delay.
This improves patient–ventilator interaction and patient
comfort.
A very high sensitivity can generate ventilator self-cycling
(auto-triggering).
With assisted ventilation, the sensitivity typically is
set at -1 to -2 cm of H2O.
22. Modes of Ventilator
Mode :- how the machine will ventilate the patient in
relation to the patient’s own respiratory efforts.
Volume Modes
Pressure mode
Dual mode
23. Volume Modes
Assist-Control Ventilation (ACV)
Each breath is either an assist or control breath, but they
are all of the same volume also called CMV.
In continuous mandatory ventilation, the ventilator can
be triggered either by the patient or mechanically by
the ventilator depending on transient presence or
absence of spontaneous breathing effort.
A preset tidal volume and respiratory rate are delivered.
It takes over the work of breathing for the client.
24. Cont…
The larger the volume, the more expiratory time
required. If the I:E ratio is less than 1:2, progressive
hyperinflation may result.
ACV is particularly undesirable for patients who breathe
rapidly – they may induce both hyperinflation and
respiratory alkalosis. Note that mechanical ventilation
does not eliminate the work of breathing, because the
diaphragm may still be very active.
25. Intermittent Mandatory Ventilation
IMV
It delivers a preset number of mechanical breaths at
varying tidal volume.
Allows the client to breath spontaneously in between
with no assistance from ventilator and a varying tidal
volume
26. Synchronized Intermittent-Mandatory
Ventilation
(SIMV)
A certain number of breaths, but unlike ACV, patient breaths
are partially their own, reducing the risk of hyperinflation or
alkalosis.
It delivers a preset number of mechanical breaths that are
synchronized with patient’s spontaneous breath
Mandatory breaths are synchronized to coincide with
spontaneous respirations.
Disadvantages of SIMV are increased work of breathing and a
tendency to reduce cardiac output, which may prolong
ventilator dependency.
27. ACV vs. SIMV
1. Patients who breathe rapidly on ACV should switch to
SIMV
2. Patients who have respiratory muscle weakness and/or
left-ventricular dysfunction should be switched to ACV
28. Pressure Modes
Pressure-Controlled Ventilation (PCV)
It does not allow for patient-initiated breaths.
The inspiratory flow pattern decreases exponentially,
reducing peak pressures and improving gas exchange.
The major disadvantage is that there are no guarantees
for volume, especially when lung mechanics are
changing. Thus, PCV has traditionally been preferred for
patients with neuromuscular disease
29. Synchronized Intermittent-Mandatory
Ventilation
Synchronized Intermittent Mandatory Ventilation (SIMV)
Combination of set patient or ventilator-initiated breaths
delivered by the ventilator that control pressure, and
the patient's own spontaneous breaths.
30. Pressure Support Ventilation (PSV)
Preset pressure augments the patient’s spontaneous
inspiration effort and decrease the work of breathing,
thus can only be used to augment spontaneous
breathing.
Patient completely control the respiratory rate and tidal
volume.
31. 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.
32. Cont..
CPAP is Positive pressure given throughout the cycle. It
can be delivered through a mask and is can be used in
obstructive sleep apnea (esp. with a nasal mask), to
postpone intubation, or to treat acute exacerbations of
COPD
33. 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 typically with the
intention to increase oxygenation and to maintain alveoli
inflation.
Improves oxygenation by reexpanding collapsed alveoli.
It is indicated in acute respiratory distress syndrome
(ARDS)
34. Airway Pressure Release Ventilation
(APRV)
Airway pressure release ventilation (APRV) is a pressure
control mode of mechanical ventilation that utilizes
an inverse ratio ventilation strategy.
APRV is an applied continuous positive airway pressure
(CPAP) that at a set timed interval releases the applied
pressure. Fundamentally this is a continuous
pressure with a brief release.
Indicated in patients with acute lung injury, acute
respiratory distress syndrome and atelectasis after major
surgery
35. Dual Modes
Pressure Regulated Volume Control (PRVC)
A volume target backup is added to a pressure assist-
control mode
Dual-control modes of ventilation are auto-regulated
pressure-controlled modes of mechanical ventilation with
a user-selected tidal volume target. The ventilator adjusts
the pressure limit of the next breath as necessary
according to the previous breath's measured exhaled
tidal volume.
53. Ventilator Alarms
High pressure alarm -
Patient obstruction (endotracheal tube, pneumothorax, secretions,
etc) - Due to sputum, kinking or biting
Equipment obstruction (ventilator circuit)- fluid pooling in circuit.
Increase airway resistance- bronchospasm, decrease chest wall
compliance
Low pressure alarm –
Patient disconnect
Leak in the ventilator circuit.
Insufficient flow.
Endotracheal/tracheostomy tube cuff leak.
54. Complication of Ventilator
Decreased Cardiac Output
Barotrauma
Nosocomial Pneumonia
Inappropriate ventilation (respiratory acidosis or alkalosis)
Pneumothorax :Pleural pressure increases, and collapses the
lung, causing Pneumothorax.
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.
55. Patient Goals
Promote respiratory functions:
Auscultate lungs frequently to assess for abnormal
sounds
Suction as needed
Turn and reposition every 2 hrs
Secure ETT properly
Monitor ABG values
Monitor for signs of respiratory distress
Restlessness
Apprehension
Irritability and increased Heart rate
57. Assess for symptoms of barotrauma
Decreased O2 level
Increased dyspnea
Tracheal deviation from effected side
Agitation
Assess for cardiovascular depression
Hypotension
Tachy/bradycardia
Dysrhythmias
58. Prevent infections:
Maintain color , amount and consistency of sputum
Maintain sterile techniques when suctioning
Provide adequate nutrition:
Monitor intake and output
Weight daily
Monitor GI bleeding:
Monitor bowel sounds
Monitor gastric pH and gastric secretions test every shift
Achieve Communication Pattern
