Mechanical Ventilation
Respiratory Care Department
Mechanical Ventilation
 Agenda For Discussion
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Definition and Causes for Acute Respiratory Failure
Ventilator Settings
Modes of Ventilation
Mechanical Ventilator Alarm Systems
Airway Placement
Complications of Mechanical Ventilation
Humidification
Respiratory Care Department
Acute Respiratory Failure (ARF)
 A condition in which the lungs, and frequently the heart and
lungs, are not able to sufficiently oxygenate the blood and body
tissue. Often, the ability to excrete CO2 is also impaired.
ARF may develop as…
An acute lung injury in patients
with normal lungs
or
An acute illness, superimposed
on a chronic lung disease
Respiratory Care Department
ARF is diagnosed and managed
with arterial blood gases ...
  PaCO2 accompanies  PaO2.
ARF is 2º to acute alveolar hypoventilation.
 With severe  PaO2 alone, there is a marked
ventilation / perfusion (V/Q) impairment.
 However, VA and  V/Q frequently co-exist!
PaO2 < 50 mm Hg
PaCO2 > 50 - 60 mm Hg
and / or
Significant respiratory acidemia
Respiratory Care Department
Causes of respiratory failure
 Respiratory Center in Brain
Brain
Respiratory Care Department
Causes of respiratory failure
 Respiratory Center in Brain
 Neuromuscular Connections
Brain
(peripheral nervous system)
Nerves
Respiratory Care Department
Causes of respiratory failure
 Respiratory Center in Brain
 Neuromuscular Connections
 Thoracic Bellows
Brain
(intact rib cage and chest wall musculature)
Nerves
Bellows
Respiratory Care Department
Causes of respiratory failure
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Respiratory Center in Brain
Neuromuscular Connections
Thoracic Bellows
Airways (upper & lower)
Brain
Nerves
Bellows
Airways
Respiratory Care Department
Causes of respiratory failure
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Respiratory Center in Brain
Neuromuscular Connections
Thoracic Bellows
Airways (upper & lower)
Lung parenchyma (alveoli)
It only requires one disrupted
“link” to cause respiratory failure !
Brain
Nerves
Bellows
Alveoli Airways
Respiratory Care Department
Effects of Major Surgery & Anesthesia
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Narcotic drugs
Paralyzing agents
Chest or abdominal incision
Dry, irritating gases
Pain, splinting, and ineffective cough
All the links are disrupted !
Brain
Nerves
Bellows
Alveoli
Airways
Respiratory Care Department
Risks of Mechanical Ventilation
 Barotrauma
• PIP > 45 cmH2O
 Volutrauma
• VT > 6-8 ml/Kg
 Oxygen Toxicity
• Prolonged FIO2 of 1.0
Respiratory Care Department
Overview
 A mechanical ventilator is a
complex system consisting of a
power supply, compressed air
and oxygen, a drive mechanism
to provide motive force to push
oxygen into the patient’s lungs
and a control mechanism to
manage the gas flow, volume,
pressure and timing.
 It is connected to the patient’s
lungs through breathing hoses
and a special tube inserted into
the patient’s airway.
 Lung injury and respiratory failure
is treated with mechanical
ventilation as a temporizing
measure until such time as the
lung heals and the patient can
resume responsibility for
adequate respiratory function.
Respiratory Care Department
Overview
 Patients of all ages, from
newborns to geriatrics, routinely
receive mechanical ventilation in
practically every hospital in the
country.
 In the vast majority of these
patients, mechanical ventilation
is a temporizing measure and
the patients are expected to be
removed (weaned) from the
ventilator when appropriate.
 Because of the umbiquity of this
procedure, the actual number of
patients receiving mechanical
ventilation daily is unknown.
 However, in the most recent
NNIS* Report, ~2.5 million
patient days of mechanical
ventilation were recorded in
~300 hospitals over a period
of 101 months.
* National Nosocomial Infection Surveillance
Respiratory Care Department
Overview
 A wide variety of mechanical
ventilators are used in hospitals,
skilled nursing facilities and private
homes to provide augmented
breathing support for people who
can not breathe adequately on their
own.
 These are complex devices in
which malfunctions sometimes
occur and in which dys-synchrony
between the machine and the
patient frequently occurs for a
variety of reasons
 Ventilators have numerous visual
and audible alarms but these are
not always able to be heard by staff
members who are not close by.
Respiratory Care Department
Ventilator (definition)
 A ventilator is simply a machine -- a
system of related elements designed
to alter, transmit, and direct applied
energy in a predetermined manner to
perform useful work.
Puritan-Bennett 7200
 A ventilator is a life support device -a system of essential elements
designed to augment or totally
support cardio-respiratory function
(i.e., ventilation, oxygenation, and
CO2 excretion) in a pre-determined
manner for an indeterminate amount
of time.
Siemens Servo 300
Siemens Servo 900C
Pulmonetics LTV-1000
Drager Evita 4
Respiratory Care Department
Ventilator classification
 Power input
 Power transmission or conversion
 Control scheme
 Output (pressure, volume and
flow waveforms)
Respiratory Care Department
Power input
 Electric
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AC
DC (battery)
 internal
 external
 Pneumatic
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Oxygen (tanks or wall)
Compressed air
 Internal air compressor
 External air compressor
 Internal turbine
Respiratory Care Department
Control scheme
 Control variables & waveform selection:
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Pressure
Volume
Flow
Time
In contemporary ventilators,
all control variables and waveforms
are managed in real time by a
microprocessor acting upon a
digitally-controlled valve.
Respiratory Care Department
Control scheme
 Phase variables:
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Trigger variable
Limit variable
Cycle variable
Baseline variable
Different brands of ventilators have different
control layouts, but they all accomplish
essentially the same functions.
Respiratory Care Department
Output
 Flow:
 Pressure:
 Ramp
 Rectangular
• ascending ramp
• descending ramp
 Sinusoidal
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Rectangular
Exponential
Sinusoidal
Oscillating
 Volume:
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Ramp
Sinusoidal
Respiratory Care Department
Typical vent settings
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FIO2
Rate
Volume
PIP and PEEP
Flowrate, I-time, I:E Ratio
Sighs, inspiratory pause
Mode ???
Different brands of ventilators have different
control layouts, but they all accomplish
essentially the same functions.
Respiratory Care Department
Ventilator Settings
 Tidal Volume (VT)
 amount of gas delivered with each preset breath
 in mechanically ventilated patients it’s usually set at 6 - 8 ml/kg
 Respiratory Rate (RR)
 the frequency of breaths delivered by the ventilator
 Fraction of Inspired Oxygen (FIO2)
 the fraction of inspired oxygen delivered to the patient by the ventilator
 change by ABG and O2 saturation
 Ventilatory Mode
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CMV, IMV, SIMV, A/C, PCV
Respiratory Care Department
Ventilator Settings
 Sigh
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may be included as part of the ventilator settings
 a breath that has a greater volume than the preset VT ,
usually 1.5 to 2.0 times the VT.
 No longer routinely used .
Sensitivity
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used to determine the patient’s effort to initiate an assisted
breath (inspiration)
 Inspiratory : Expiratory Ratio (I : E Ratio)
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usually set at 1 : 2, may be manipulated to facilitate gas
exchange
Respiratory Care Department
Ventilator Settings
 Peak Inspiratory Pressure (PIP)
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peak pressure registered in the airway during normal
ventilation
value used to set high and low pressure alarm limits
Not to be confused with Peak Flow which measures the
velocity of air flow per unit of time (L/min)
 Adjuncts to Mechanical Ventilation
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PEEP, CPAP, PSV
 Pressure Limits
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high pressure limit is the maximum pressure the ventilator
can generate to deliver the preset VT
usually set 10 - 20 cm H2O above the PIP
Respiratory Care Department
Ventilator Settings
 Alarms
VENTILATOR ALARMS MUST NEVER BE IGNORED OR DISARMED!!!!
 Loss of Power
ELECTRICAL FAILURE ALARMS ARE A MUST FOR ALL VENTILATORS
 Most ICU ventilators do not have battery back up like at home
 Know back up system (special emergency outlets)
 Check that power cord plug not accidentally disconnected
Frequency
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Alarms if RR goes above or below set levels
 Volume
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Volumes go above or below preset levels (ie. VT or minute volume)
Respiratory Care Department
Ventilator Settings
 Pressure
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Change in inspiratory or peak airway pressure above or below
preset limits
Low Pressure Alarms
Disconnection
Loss of VT
Leaks
Extubation
High Pressure Alarms
 Compliance: secretions
pneumothorax
ARDS/Pulmonary Edema
bronchospasm
ETT in R mainstem
“bucking”
coughing
pt. biting on tube
tubing kinked
H2O in tubing
Respiratory Care Department
Monitored parameters
 Spontaneous VT
 Vital Capacity (VC)
 Negative Inspiratory Force (NIF)
 Compliance
 Minute Volume (MV)
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determines alveolar ventilation (RR x VT = MV)
 Airway Placement / Patency
 ABGs
Respiratory Care Department
Control Ventilation
The ventilator delivers a pre-determined VT (volume or pressure
targeted) at a preset frequency
 Advantages
 Guaranteed minute ventilation or peak pressure
 Disadvantages
 No patient interaction. The patient can not initiate a breath
Respiratory Care Department
Assist/Control Ventilation
The ventilator delivers a pre-determined VT (volume or pressure
targeted) with each inspiratory effort generated by the patient. A backup frequency is set to insure a minimum VE
 Advantages
 Patient can increase VE by increasing respiratory rate
 Disadvantages
 Dys-synchrony
 Respiratory alkalosis
 Dynamic hyperinflation
Respiratory Care Department
Synchronized Intermittent
Mandatory Ventilation (SIMV)
The ventilator delivers a pre-determined VT (volume or pressure
targeted) at a preset frequency and allows the patient to take
spontaneous breaths between ventilator breaths. Spontaneous
breaths may be augmented with pressure support.
 Advantages
 Decreased mean airway pressure
 Improved venous return
 Disadvantages
 Increased oxygen consumption
 Increased work of breathing
Respiratory Care Department
Pressure Control Ventilation
(PCV)
The practitioner sets the maximal pressure obtained by the ventilator
(preset Pressure), frequency and time the pressure is sustained
(inspiratory time). Inspiratory time is set as a percent of the total cycle or
absolute time in seconds.
 Advantages
 Tidal volume variable with constant peak airway pressure
 Full ventilatory support
 Decreased mean airway pressure
 Control frequency
 Disadvantages
 Requires sedation or paralysis
 Ventilation does not change in response to clinical changing
needs
Respiratory Care Department
High Frequency Ventilation
High frequency ventilation is broadly defined as ventilatory support using small
tidal volumes with high respiratory rates. Initially used in children, now used in
adults who cannot be effectively ventilated with conventional methods.
 Advantages
 Use small tidal volumes at very lower peak inspiratory pressures
 May be associated with lower incidence of pneumothorax
 Improves gas exchange with infants with RDS at lower airway pressures
than conventional ventilation
 Can reduce flow through a bronchopleural fistula and may promote its
healing
 Disadvantages
 Gas trapping
 Necrotizing tracheobronchitis when used in the absence of adequate
humidification
Respiratory Care Department
Pressure Support Ventilation (PSV)
The ventilator delivers a predetermined level of positive pressure
each time the patient initiates a breath. A plateau pressure is
maintained until inspiratory flow rate decreases to a specified level
(e.g. 25% of the peak flow value).
 Advantages
 The flow rate, inspiratory time, and frequency are variable
and determined by the patient
 Decreased inspiratory work
 Enhanced muscle reconditioning
 Disadvantages
 Requires spontaneous respiratory effort
 Delivered volumes affected by changes in compliance
Respiratory Care Department
Positive End Expiratory Pressure
(PEEP)
PEEP is the application of positive pressure to change baseline
variable during CMV, SIMV, IMV and PCV. PEEP is primarily used
to improve oxygenation in patients with severe hypoxemia.
 Advantages
 Improves oxygenation by increasing FRC
 Decreases physiological shunting
 Improved oxygenation will allow the FIO2 to be lowered
 Increased lung compliance
 Disadvantages
 Increased incidence of pulmonary brotrauma
 Potential decrease in venous return
 Increased work of breathing
 Increased intracranial pressure
Respiratory Care Department
Continuous Positive Airway pressure
(CPAP)
Continuous Positive Airway Pressure is simply a spontaneous
breath mode, with the baseline pressure elevated above zero.
 Advantages
 Improves oxygenation by increasing FRC
 Decreases physiological shunting
 Improved oxygenation will allow the FIO2 to be lowered
 Increased lung compliance
 Disadvantages
 Increased incidence of pulmonary brotrauma
 Potential decrease in venous return
 Increased work of breathing
 Increased intracranial pressure
Respiratory Care Department
Waveforms (graphics)
The nomenclature of mechanical ventilation
Respiratory Care Department
Graphics can illustrate problems
and help adjust the vent
Respiratory Care Department
Alarm Systems
 Input power alarms:
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Loss of electric power
Loss of pneumatic power
Control circuit alarms:
 General systems failure
(vent inoperative)
 Incompatible ventilator
settings
 Inverse I : E Ratio
Respiratory Care Department
Alarm Systems
 Output alarms:
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Pressure
Volume
Flow
Inspired Gas
 high / low inspired
gas temperature
 high / low FIO2
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Time
 high / low ventilator
frequency
 high / low inspiratory time
 high / low expiratory time
(high expiratory time =
apnea)
Respiratory Care Department
Changes with Mechanical Ventilation
 Endotracheal tube (ETT) or tracheostomy tube (TT) placed
 Increased resistance to air flow
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due to change in airway diameter and length
 diameter = resistance  length =  resistance
 Tube interrupts normal mucociliary clearance of airway
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 risk of infection
 Intrathoracic pressure changes on the chest
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(ie PEEP   venous return,  CO)
Respiratory Care Department
Airway Placement
 Intubation
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Refers to the insertion of an artificial airway, an endotracheal tube
(ETT) into the trachea through the mouth or nose
Oral Intubation
Advantages:
easily and quickly performed
larger tube used - facilitates suctioning and procedures
less kinking of tubing
Disadvantages: not recommended suspected cervical injury
uncomfortable
dental trauma, more difficult to perform mouth care
occlusion due to biting down on tube
Respiratory Care Department
Airway Placement
Nasal Intubation:
Advantages:
greater patient comfort and tolerance
better mouth care possible
less risk of accidental extubation
Disadvantages: more difficult perform
may cause nasal hemorrhage, sinusitis, nasal septal
necrosis
suctioning more difficult (smaller and longer tube)
ETT
- Tube has a distal balloon or cuff that is inflated to facilitate ventilation of the
patient
- Proximal adaptor attaches to ventilator or manual resuscitation bag
- Available in many sizes: average female 7.0 - 8.0 mm (32 -34 Fr)
average male 8.0 - 9.0 mm (36 Fr)
Respiratory Care Department
Airway Placement
 Equipment Needed for Intubation
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Stylet
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Laryngoscope & blade
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Suction / suction catheters
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Syringe to inflate cuff (10 cc)
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Topical anesthetic & sedation as ordered
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Water soluble lubricant
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Tape or device to secure tube
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Stethoscope
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Manual Resuscitation Bag (Ambu)
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O2 flow meter
Respiratory Care Department
Airway Placement
 Assisting with Intubation
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Intubation is performed by anesthesiologists, nurse anesthetists,
RTs, some paramedics, and MDs.
Check cuff and laryngoscope prior to insertion
Administer sedation/neuromuscular blockade as ordered
Prepare patient: remove dentures, suction if indicated, and
preoxygenate
Certified individual intubates, assist as needed
After intubation: Auscultate breath sounds bilaterally, inflate cuff,
secure tube, connect to ventilator or oxygen source
Order CXR to confirm placement
Insert NGT or OGT to prevent aspiration
Record position of tube at lips (cm)
Change sides of mouth q 24 hours
May need to insert oral airway to prevent biting of tube
Respiratory Care Department
Airway Placement
 Complications of Intubation
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Trauma to airway structures
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Hypoxia
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Dysrhythmias
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Aspiration
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Intubation of esophagus or right mainstem bronchus
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Laryngospasm
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Bronchospasm
Respiratory Care Department
Airway Placement
 Tracheostomies
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a tracheostomy tube (TT) may be needed if the patient requires long term mechanical ventilation, frequent suctioning to manage
secretions, or to bypass airway obstruction
procedure is usually performed in the OR
 Advantages of TT to ETT
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faster weaning
enhanced patient comfort and communication
possibility of oral feeding
more effective clearing of secretion
 Disadvantages of TT
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hemorrhage, pneumothorax, tracheal stenosis, accidental
decannulation
need for an operative procedure
Respiratory Care Department
Airway Placement
 Types of TT
1. Cuffed TT
- used for patients who require long term mechanical ventilation
- may or may not have inner cannula
2. Fenestrated TT
- used to wean patient from vents as well as the trach itself
- has holes that permit some air to escape
- Patient can emit vocal sounds while the tube is in place
3. Cuffless TT
- used for long-term airway management in a patient who does not
require mechanical ventilation and is at low risk for aspiration
Respiratory Care Department
Complications of Mechanical
Ventilation
 Barotrauma
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presence of extra alveolar air
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this air may escape (usually due to alveolar or bleb rupture) into the:
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pleura (pneumothorax)
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mediastinum (pneumomediastinum)
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pericardium (pneumopericardium)
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under the skin (subcutaneous emphysema or crepitus)
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may occur when the alveoli are over distended such as with positive
pressure ventilation, high tidal volumes or PEEP
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Signs & Symptoms: increased PIP, decreased breath sounds, tracheal
shift, hypoxemia
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Could worsen to tension pneumothorax
Respiratory Care Department
Complications of Mechanical
Ventilation
 Cardiovascular
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decreased venous return and CO
may be manifested by decreased BP, decreased LOC,
decreased urinary output, weak pulses, fatigue
 Gastrointestinal
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stress ulcers
GI bleeding
distention
hypomotility & paralytic ileus
Malnutrition: atrophy of respiratory muscles,  protein,
 albumin,  immunity,  surfactant production, impaired
cellular oxygenation, and central respiratory depression
Respiratory Care Department
Complications of Mechanical
Ventilation
 Inadequate Ventilation
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Intubation of right mainstem bronchus
ETT out of position/extubation
Incompatible settings
Misassembly of circuits or parts
Tampering
Operator error
 Tracheal Damage/Necrosis
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the systolic pressure in mucosal vessels of the trachea normally
20 - 25 mmHg
Goal: create seal with inflation of cuff at inflation pressure
 20 mmHg
Leaks
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can cause a decrease in tidal volume
check all ventilator tubing for disconnections or leaking
can be leaking at cuff of airway or one - way valve of airway
Respiratory Care Department
Complications of Mechanical
Ventilation
 Mechanical Malfunction (Breakdown)
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Ventilator mechanically fails
Tubing / or exhalation valve
Humidifier
Medication nebulizer
Air / Oxygen mixer
Compressed gas supply
Oxygen gas supply
Monitoring components
Respiratory Care Department
Complications of Mechanical
Ventilation
 Resistance / Obstruction of Airway
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Usually caused by situations which  compliance
May be equipment related: ETT kinked, water in tubing, patient biting ETT
May be patient related: secretions, bronchospasm, atelectasis, “bucking”
ventilator
 Acid - Base Disturbances
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respiratory alkalosis versus respiratory acidosis
 O2 Toxicity
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occurs with high concentrations of oxygen (FIO2 60%)
 Aspiration
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gastric distention, impaired gastric emptying and esophageal reflux
predispose patient to aspiration
Respiratory Care Department
Complications of Mechanical
Ventilation
 Infection
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patients with artificial airways are at increased risk for pulmonary infection
ETT suctioning can also predispose the patient to infection and frequently
cause nosocomial infection
Intubated patients have a 10 fold increase in nosocomial pneumonia
Water Imbalance
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increased pressures on baroreceptors in the thoracic aorta from positive
pressure ventilation stimulates release of ADH.
ADH causes water retention and stimulates the renin-angiotensin-aldosterone
mechanism which increases water retention.
Immobility
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complications: muscle weakness/wasting, contractures, loss of skin integrity,
pneumonia, DVT  PE, constipation, ileus
Respiratory Care Department
Complications of Mechanical
Ventilation
 Psychological Complications
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patient may experience stress/anxiety due to being on a machine to
breathe
communication becomes challenging
loses autonomy/control over care
altered sleep pattern may occur
depression may occur
may develop psychological dependence on vent even if can
physically be weaned
 Ventilator Dependence/ Inability to Wean

patients who require long term ventilation are usually very
challenging when it comes to weaning.
Respiratory Care Department
Complications of Mechanical
Ventilation
 Ventilator Acquired Pneumonia Issues
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Circuit Change frequency
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Closed system suction change frequency
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Condensate elimination
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Elevate head of bed
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Limit the number of disconnects
Respiratory Care Department
Complications of Mechanical
Ventilation
 Emergency Response / Procedure
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Disconnect ventilator circuit from patient
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Provide manual ventilation with self-inflating
manual resuscitation bag
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Call immediately for Respiratory Care Practitioner
Respiratory Care Department
Heated Humidification
Respiratory Care Department
Heated Humidification
 The Early Days of Heated Humidification
 The potential role of inhalation therapy equipment in nosocomial
pulmonary infection. Reinarz, et al. J Clin Invest 1965; 44:831-839.
 A hospital outbreak of Serratia marcesens associated with
ultrasonic nebulizers. Ringrose, et al. Ann Intern Med 1968; 69:
719-729.
 Long-term evaluation of decontamination of inhalation therapy
equipment and the occurrence of necrotizing pneumonia. Pierce, et
al. N Engl J Med 1970; 282:518-530.
 Bacterial contamination of aerosols. Pierce, et al. Arch Intern Med
1973; 131:156-159.
Respiratory Care Department
The original Cascade® Humidifier
Gas outlet
Gas inlet
Bubble
diffuser
Heater
Respiratory Care Department
Heated Humidification
 Humidifier Evolution
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In the “early days,” both pneumatic and ultrasonic nebulizers (large
volume particle generators) were used to provide humidification
during mechanical ventilation.
The Cascade® Humidifier was the first “vapor phase” humidifier but
it inadvertently produced aerosols.
Bubbling humidifiers produce microaerosols
which can carry bacteria. Rhame, et al. Infection
Control 1986; 7: 403-406.
Respiratory Care Department
Heated Humidification
 Humidifier Evolution
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Contemporary humidifiers produce water vapor only and
are incapable, by design, of producing particles or
conducting particles in the gas stream, even at flowrates as
high as 120 L/min.

Contemporary humidifiers heat water to such a high
temperature that they may be at least bacteriostatic, if not
bacteriocidal.
Humidifiers kill bacteria. Gilmour, et al.
Anesthesiology 1991; 75(3A): a498.
Respiratory Care Department
Wick Type Heated Humidifier
Hudson/RCI “ConchaTherm”
Respiratory Care Department
Hudson/RCI “ConchaTherm”