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VENTILATOR THE BASIC- COURSE. HISTORY OF VENTILATOR. Early History of Ancient times . Old testament there is a mention of Prophet Elisha Inducing pressure breathing from his mouth into the mouth of a child who was dying–(Kings 4:34-35). . Hippocrates (460-375 BC) wrote 

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Early History of Ancient times

Old testament there is a mention of Prophet Elisha

Inducing pressure breathing from his mouth into the mouth of a child

who was dying–(Kings 4:34-35).

Hippocrates (460-375 BC) wrote 

the first description of endotracheal intubation his book –‘Treatise on Air’

“One should introduce a cannula into the trachea along

the jaw bone so that air can be drawn into the lungs”.


Negative Pressure Ventilators

Two successful designs became popular;

In one - the body of the patient was enclosed in an iron box or cylinder

and the patient’s head protruded out of the end.

The second - design was a box or shell that fitted over the thoracic area only

(chest cuirass).



(Philip Drinkerand Louis Agassiz Shaw)mid-1900s

The first iron lungwas used on October 12, 1928at

Children's Hospital,Boston,

-used in a child unconscious from respiratory failure;

-her dramatic recovery, within seconds

popularize the "Drinker Respirator."


In 1949, John Haven Emerson

Developed a mechanical assister for anesthesiaat Harvard University.


Iron lung ward filled with Polio patients,

Rancho Los Amigos Hospital, ca. 1953


During the 1950's

Mechanical ventilators used increasingly in

Anesthesia and intensive care.

-To treatpoliopatients and

-The increasing use ofmuscle relaxants

during anesthesia


















Mechanical ventilation is used when a patient is unable to breathe adequately on his or her own.

  • The ventilator can either completely take over respiratory function, or it can be used to support the patient’s own respiratory efforts


A mechanism for telling the body that it is time to breath:

This involves CO2 sensors in the brainstem, which signal diaphragmatic movement via the cervical nerves.

The phrenic nerves

The diaphragm contracts –

it increases the volume of the thorax,

by moving down into the abdomen,

making the intra-pleural and intra-alveolar pressure more negative,

creating a pressure gradient between the atmospheric and the alveoli,

and allowing air to pass down through a series of narrowing bronchi into the alveoli.

The alveoli and the pulmonary capillary network,

Derived from the main pulmonary arteries,

oxygen and carbon dioxide diffuse across the concentration gradient

out of and into the alveoli respectively.

The diffusion of CO2 is more effective due to it’s higher solubility.


Indications for mechanical ventilation:

Ventilation Failure

Oxygenation Failure


Failure to Ventilate

Characterized by reduced alveolar ventilation

which manifests

as an increase in the PaCO2 > 50 mmHg


Indications for mechanical ventilation:

  • Is itfailure to ventilate(is the PCO2 > 50mmHg), orfailure to oxygenate(is the PO2 <50mmHg)?
  • Remember that a low O2 is much more significant than a high PCO2,
  • If it isventilatory failure, where is the injury – in the brain (the medulla), - in the spinal cord, - in the peripheral nerves, - at the neuromuscular junction, - in the muscle itself or in the chest cage?
  • If the problem isoxygenation failure, where is the injury: - Is it in the blood supply, - at the alveolar-capillary interface or - in the upper, middle or lower airways?
Neurological Problems ( Ventilatory failure )
  • Central:

Loss of ventilatory drive due to sedation, narcosis, stroke or brain injury.

  • Spinal:

Spinal cord injury, cervical – loss of diaphragmatic function,

thoracic – loss of intercostals.

  • Peripheral:Nerve injury (e.g. phrenic nerve in surgery), Guillain-Barre syndrome (demyelination), poliomyelitis, motor neurone disease.
  • Muscular Problems

– myasthenia gravis, steroid induced myopathy, protein malnutrition.

  • Anatomical Problems

Chest Wall– rib fractures or flail chest, obesity, abdominal hypertension, restrictive dressings

Pleura– pleural effusions, pneumothorax, hemothorax.

Airways – airway obstruction (in lumen, in wall, outside wall), laryngeal edema, inhalation of a foreign object, bronchospasm


Failure to Oxygenate

Diffusion abnormality–

Thickening of the alveoli (fibrosis)

Increased extracellular fluid – pulmonary edema.

This obstructs gas exchange.

  • Ventilation/Perfusion Mismatch :Dead Space Ventilation
  • (or high V/Q)–
  • Alveoli are ventilated but not perfused

Eg; pulmonary embolus

  • Dead space may be anatomical - the conducting airways(150ml)
  • physiological, for example in hemorrhage or hypotension

Shunt (or low V/Q)–where alveoli are perfused but not ventilated

occurs in airway collapse,


pulmonary hemorrhage (contusion), ARDS/ALI.

Inability to extract O2 at cellular level–sepsis, cyanide

or carbon monoxide poisoning


Mechanical Ventilator What is it?

Amechanical ventilatoris a machine that generates a controlled flow of gas

into a patient’s airways

Two kinds of ventilators:

Negative pressure and Positive pressure.

Negative Pressure :

-iron lung, the Drinker respirator, and the chest shell

-advantage these ventilators didn’t require insertion of an artificial airway,

-disadvantage they were noisy and made nursing care difficult.

Positive Pressure :

-The Emerson Company in Boston developed the positive pressure ventilator, which was first used at Massachusetts General Hospital.


Positive pressure ventilators

  • Require an artificial airway (endotracheal or tracheostomy tube),
  • and use positive pressure to force oxygen into a patient’s lungs
  • Inspiration can be triggered either by the patient or the machine.
  • Four types of positive pressure ventilators:
  • volume cycled
  • pressure cycled

-deliver a preset tidal volume

-ideal for patients with bronchospasm since the same tidal volume is delivered regardless of the amount of airway resistance

-deliver gases at preset pressure

-decreased risk of lung damage from high inspiratory pressures

-disadvantage is that the patient may not receive the complete tidal volume if he or she has poor lung compliance and increased airway resistance


flow cycled

  • time cycled

-deliver a breath until a preset flow rate

These aren’t used

-deliver a breath over a preset time period

expiration is passive


gas flows along a pressure gradient between the upper airway and the alveoli

Flow is either volume targeted and pressure variable, or pressure limited and volume variable.

The pattern of flow may be either sinusoidal (which is normal), decelerating or constant. Flow is controlled by an array of sensors and microprocessors.


Mechanical Ventilators Classification

1) Control

Either Volume Controlled(volume limited, volume targeted) and Pressure VariableorPressure Controlled(pressure limited, pressure targeted) and Volume VariableorDual Controlled(volume targeted (guaranteed) pressure limited)

2) Cycling:

Time cycled- such in in pressure controlled ventilation

Flow cycled- such as in pressure support

Volume cycled- the ventilator cycles to expiration once a set tidal volume

has been delivered: this occurs in volume controlled ventilation

-If an inspiratory pause is added,

then the breath isboth volume and time cycled



3) Triggering:

  • what causes the ventilator to cycle to inspiration?
  • Ventilators may be
  • time triggered,
  • pressure triggered or flow triggered.
  • Time:the ventilator cycles at a set frequency as determined by the
  • controlled rate.
  • Pressure:the ventilator senses the patient's inspiratory effort
  • by way of a decrease in the baseline pressure.
  • Flow:modern ventilators deliver a constant flow around the circuit
  • throughout the respiratory cycle (flow-by). A deflection in this
  • flow by patient inspiration, is monitored by the ventilator and
  • it delivers a breath.
  • This mechanism requires less work by the patient than pressure triggering.
  • (Contd)
4) Breaths are either:

what causes the ventilator to cycle from inspiration?

  • Mandatory (controlled) -which is determined by the respiratory rate.
  • Assisted - (as in assist control, synchronized intermittent mandatory

ventilation, pressure support)

  • Spontaneous- (no additional assistance in inspiration, as in CPAP)
  • 5) Flow pattern:
  • constant, accelerating, decelerating or sinusoidal
  • Sinusoidal =this is the flow pattern seen in spontaneous breathing and CPAP
  • Decelerating =the flow pattern seen in pressure targeted ventilation:
  • inspiration slows down as alveolar pressure increases
  • (there is a high initial flow).
  • (Contd)
Constant -flow continues at a constant rate until the set tidal volume is delivered
  • Accelerating-flow increases progressively as the breath is delivered. This should not be used in clinical practice. Flow Pattern


1.      Theresting point of outward chest spring and inward lung collapse is the

Functional Residual Capacity (FRC):

this is a reservoir for gas exchange .The FRC is the lung’s physiologic reserve, it is a reservoir.

2.      Loss of chest wall or lung compliance causes reduced FRC.

3.      Exhalation below FRC is active causing dynamic airway collapse,

trapping air in the alveoli (auto PEEP)

4.      At residual volume it is not possible to empty alveoli of air further,

due to dynamic airway collapse (airway closure)

5.      The closing volume (CV) is the point at which dynamic compression of the airways begins.

6.      Such airway closure occurs normally within FRC, and it is known as the closing volume (CV).

With age and disease the CV moves into the tidal breathing range.

7.      The CV increases with age, smoking, lung disease, and body position (supine > erect).

8.      Airway collapse increases the work of breathing and leads to ventilation-perfusion mismatch

9.      In mechanically ventilated patients airway collapse is prevented by applying positive pressure

to the airway throughout the respiratory cycle – CPAP/PEEP

10.  PEEP/CPAP works by increasing FRC, maintaining alveolar recruitment facilitating gas

exchange (and removal of CO2 and replenishment of O2), and

reducing the workload of breathing.

11.  The patient requires sufficient PEEP to prevent alveolar de-recruitment, but not so much PEEP

that alveolar over-distension, dead space ventilation and hypotension occurs.

12.  The ideal level of PEEP is that which prevents de-recruitment of the majority of alveoli,

while causing minimal over-distension.

13.  Recruitment maneuvers are used to re-inflate collapsed alveoli, a sustained pressure above

the tidal ventilation range is applied, and PEEP is used to prevent de-recruitment.

14.  Auto-PEEP is gas trapped in alveoli at end expiration, due to inadequate time for expiration,

bronchoconstriction or mucus plugging. It increased the work of breathing.

15.  The increased work of breathing associated with auto-PEEP can be offloaded by applying CPAP

to the trachea/mouth, and splinting open the connecting airways.

The objective is to set the CPAP level above the auto-PEEP level.


Ventilator Waveforms

Airway pressure screen

Step 1: - determine the CPAP level

– this is the baseline position from which there is a downward deflection on,

at least, beginning of inspiration, and to which the airway pressure returns

at the end of expiration.

Step 2: is the patient triggering?

-There will be a negative deflection into the CPAP line just before inspiration


Step 3: what is the shape of the pressure wave?

-If the curve has a flat top, then the breath is pressure limited,

if it has a triangular or shark’s fin top, then it is not pressure limited

and is a volume breath.

Flow screen:

Step 4: what is the flow pattern?

– If it is constant flow (square shaped) this must be volume controlled,

if decelerating, it can be any mode.


Is the patient gas trapping? –

-expiratory flow does not return to baseline before inspiration commences

(i.e. gas is trapped in the airways at end-expiration).

Step 4:the patient is triggering –

is this a pressure supported  or SIMV or VAC breath?

-This is easy, the pressure supported breath looks completely differently

than the volume control or synchronized breath:

the PS breath has a decelerating flow pattern, and has a flat topped

airway pressure wave. The synchronized breath has a triangular

shaped pressure wave.

Airway pressure

Flow pattern


Step 5: the patient is triggering – is this pressure support or pressure control?

-The fundamental difference between pressure support and pressure control

is the length of the breath – in PC, the ventilator determined this (the inspired time)

and all breaths have an equal “i” time. In PS, the patient determined the

duration of inspiration, and this varies from breath to breath.


Step 6: is the patient synchronizing with the ventilator?

-Each time the ventilator is triggered a breath should be delivered.

If the number of triggering episodes is greater than the number of breaths,

the patient is asynchronous with the ventilator. Further, if the peak flow rate of the ventilator is inadequate, then the inspiratory flow will be "scooped" inwards, and the patient appears to be fighting the ventilator.

Both of these problems are illustrated below


Ventilator Modes

  • Control Ventilation (CV)
  • Assist-Control Ventilation (A/C)
  • Synchronous Intermittent Mandatory Ventilation (SIMV)
  • Pressure Support Ventilation (PSV)
  • Positive End Expiratory Pressure (PEEP)
  • Constant Positive Airway Pressure (CPAP)
  • Independent Lung Ventilation (ILV)
  • High Frequency Ventilation (HFV)
  • Inverse Ratio Ventilation (IRV)
  • Advanced Pressure Control Modes
  • -Inverse Ratio Ventilation (IRV) and -Airway Pressure Release Ventilation (ARPV),
  • -Bilevel and Proportional Assist Ventilation?

1)Control Ventilation (CV)

-CV delivers the preset volume or pressure regardless of the patient’s own inspiratory efforts.

-This mode is used for patients who are unable to initiate a breath.

-If it is used with spontaneously breathing patients, they must be sedated and/or pharmacologically paralyzed so they don’t breathe out of synchrony with the ventilator.


2)Assist-Control Ventilation (A/C)

-A/C delivers the preset volume or pressure in response to the patient’s own inspiratory effort but will initiate the breath if the patient does not do so within the set amount of time.

-This means that any inspiratory attempt by the patient triggers a ventilator breath.

-The patient may need to be sedated to limit the number of spontaneous breaths since hyperventilation can occur.

-This mode is used for patients who can inititate a breath but who have weakened respiratory muscles.


3) Synchronous Intermittent Mandatory Ventilation (SIMV)

-SIMV was developed as a result of the problem of high respiratory rates associated with A/C.

-SIMV delivers the preset volume or pressure and rate while allowing the patient to breathe spontaneously in between ventilator breaths.

-Each ventilator breath is delivered in synchrony with the patient’s breaths, yet the patient is allowed to completely control the spontaneous breaths.

-SIMV is used as a primary mode of ventilation, as well as a weaning mode.

-The disadvantage of this mode is that it may increase the work of breathing and respiratory muscle fatigue.


4) Pressure Support Ventilation (PSV)

-PSV is preset pressure that augments the patient’s spontaneous inspiratory effort and decreases the work of breathing.

-The patient completely controls the respiratory rate and tidal volume.

-PSV is used for patients with a stable respiratory status and is often used with SIMV to overcome the resistance of breathing through ventilator circuits and tubing.


5) Positive End Expiratory Pressure (PEEP):

-PEEP is positive pressure that is applied by the ventilator at the end of expiration.

-Used as an adjunct to CV, A/C, and SIMV to improve oxygenation by collapsed alveoli at the end of expiration.


decreased cardiac output,

pneumothorax, and

increased intracranial pressure.


6) Constant Positive Airway Pressure (CPAP)

-CPAP is similar to PEEP except that it works only for patients who are breathing spontaneously.

-The effect of both is comparable to inflating a balloon and not letting it completely deflate before inflating it again. The second inflation is easier to perform because resistance is decreased.

-CPAP can also be administered using a mask.


7) Independent Lung Ventilation (ILV)

-This method is used to ventilate each lung separately in patients with unilateral lung disease or with a different disease process in each lung.

-It requires a double-lumen endotracheal tube and two ventilators.

-Sedation and pharmacological paralysis are used to facilitate optimal ventilation and increased comfort for the patient.

8) High Frequency Ventilation (HFV)

-HFV delivers a small amount of gas at a rapid rate (as much as 60-100 breaths per minute.)

-This is used when conventional mechanical ventilation would compromise hemodynamic stability, during short-term procedures, or for patients who are at high risk for pneumothorax.

-Sedation and pharmacological paralysis are required.


9) Inverse Ratio Ventilation (IRV)

-The normal inspiratory:expiratory ratio is 1:2 but this is reversed during IRV to 2:1 or greater (the maximum is 4:1).

-This mode is used for patients who are still hypoxic even with the use of PEEP.

-The longer inspiratory time increases the amount of air in the lungs at the end of expiration (the functional residual capacity) and improves oxygenation by reexpanding collapsed alveoli.

-The shorter expiratory time prevents the alveoli from collapsing again.

-Sedation and pharmacological paralysis are required since it’s very uncomfortable for the patient.



Control Ventilation (CV)Delivers preset volume or pressure Usually used for patients who are apneic regardless of patient’s own inspiratory efforts

Assist-Control Ventilation (A/C)Delivers breath in response to Usually used for spontaneously

patient effort and if patient fails to breathing patients with weakened

do so within preset amount of timerespiratory muscles

Synchronous Intermittent MandatoryVentilator breaths are synchronized Usually used to wean patients from

mechanical ventilation

with patient’s respiratory effort

Ventilation (SIMV)

Pressure Support Ventilation (PSV)Preset pressure that augments the Often used with SIMV during

weaning patient’s inspiratory effort and

decreases the work of breathing

Positive End Expiratory Pressure

(PEEP)Positive pressure applied at the end Used with CV, A/C, and SIMV to

Improve oxygenation by opening collapsed alveoli

of expiration

Constant Positive Airway PressureSimilar to PEEP but used only with Maintains constant positive pressure

in airways so resistance is decreased

spontaneously breathing patients



Independent Lung Ventilation (ILV) Ventilates each lung separately; Used for patients with unilateral lung

disease or different disease process

In each lung

requires two ventilators and


High Frequency Ventilation (HFV) Delivers small amounts of gas at a Used for hemodynamic instability,

during short-term procedures, or if

patient is at risk for pneumothorax

rapid rate (60-100 breaths/minute);

requires sedation/paralysis

Inverse Ratio Ventilation (IRV) I:E ratio is reversed to allow longer Improves oxygenation in patients

who are still hypoxic even with PEEP;

keeps alveoli from collapsing

inspiration; requires sedation/



Volume Control Ventilation

Anesthesiologists use mechanical ventilators in the operating room.

These are “bag in bottle” mechanical bellows which are controlled by three factors:

1) tidal volume, 2) respiratory rate, 3) I:E ratio.

Conventional anesthesia ventilator: the patient is delivered mandatory breaths from a “bag in bottle” ventilator.

He can also draw unsupported spontaneous breaths from an in-line reservoir bag:


-Longer inspiratory times and faster respiratory rates predispose to alveolar gas trapping

Pressure-assist ventilation –

Pressure assist ventilation is pressure control without a set rate.

Patients take pressure controlled breaths at the rate of their choosing,

and the volumes derived are determined by the pressure preset level,

the Ti and the flow demanded.

This is a very comfortable mode,

and is used in weaning from pressure control (the pressure limit is weaned).


Pressure Controlled Ventilation

controlled (CMV)


pressure control.


“The term “pressure control” refers to an assist control mode”

-A pressure limited breath is delivered at a set rate.

-The tidal volume is determined by the preset pressure limit.

-The flow waveform is always decelerating in pressure control

-Gas flows into the chest along the pressure gradient.

-As the airway pressure rises with increasing alveolar volume the rate of flow

drops off (as the pressure gradient narrows) until a point is reached.

when the delivered pressure equals the airway pressure: flow stops.

-The pressure is maintained for the duration of inspiration .

Obviously, longer inspiratory times lead to higher mean airway pressures

(the “i” time (Ti) is a pressure holding time after flow has stopped).

-The combination of decelerating flow and maintenance of airway pressure

over time means that stiff, noncompliant lung units (long time con

which are difficult to aerate are more likely to be inflated.

-Drawbacks of pressure control? -Pressure control does not guarantee minute ventilation. change in the compliance, then the patient may hypoventilate and become hypoxic.


Volume Assist Control

In volume assist-control -often labelled “volume control”

-patients may receive either controlled or assisted breaths.

-When the patient triggers the ventilator,

he/she receives a breath .

-The patient receives a breath of this type irrespective of

actual minute ventilation requirement, so patients

tend to hyperventilate as they emerge.

Assist control (AC) ventilationinvolves the use of four variables:

-tidal volume

-respiratory rate

- inspiratory flow (as an alternative to I:E ratio)

-trigger sensitivity

If the flow rate is too high, the volume is rapidly delivered to only the

most compliant lung tissues (and not to the inelastic diseased tissues),

If the peak flow is too low, the patient will demand more gas than the

ventilator is set up to supply and dysynchrony with the machine occurs


The inspiratory flow rate is measured in liters per minute, and it determines

how quickly the breath is delivered.

The time required to complete inspiration is determined by the tidal volume

delivered and the flow rate:

Ti = VT/Flow Rate.

controlled breaths

assisted breaths

decelerating flow pattern

tidal volume is identical


Ventilation  How to Initiate Mechanical Ventilation

The ventilation strategy

-is determined by whether the patient has failure to ventilate or failure to oxygenate.

-The first problem is managed by increasing the patients minute ventilation,

-the second by recruiting collapsed lung units and controlling mean airway pressure.

Sedation- fentanyl


morphine with lorazepam, midazolam or propofol

For profoundly hypoxemic patients, the addition of a

neuromuscular blocking agent


The Procedure of Rapid Sequence Induction

  • Preparation:
  • Drugs:thio/ propofol/ etomidate/ midazolam, succinyl choline,
  • atropine, ephedrine/phenylephrine.
  • Endotracheal tubes:a variety of sizes available and cuff checked
  • (to make sure that the cuff is intact -–ie. Not punctures)
  • Laryngoscopes– 2 functioning laryngoscopes with a variety of blades.
  • Suction– on and under the pillow.
  • AGum elastic bougie– to railroad the ETT if there is difficulty in placing the ett.
  • An intravenouscannula, with a free-flowing drip
  • Monitoring:
  • blood pressure, ECG, pulse oximetry, end tidal CO2 (if available).


1.       Awake intubation +/- local anesthesia applied topically.

2.       Sedation with midazolam +/- local anesthetic.

3.       Midazolam + succinylcholine

4.       Ketamine + succinylcholine (small babies).

5.       Thiopental or propofol + succinylcholine

6.       Etomidate + succinylcholine


Ventilator Settings

Respiratory Rate (RR)

-The respiratory rate is the number of breaths the ventilator delivers to the patient each minute.

-The rate chosen depends on the

tidal volume

the type of pulmonary pathology

the patient’s target PaCO2.

-Obstructive lung disease, the rate should be set at 6-8 breaths/minute to avoid the development of auto-PEEP and hyperventilation

-Restrictive lung disease usually tolerate a range of 12-20 breaths/minute.

- Patients with normal pulmonary mechanics can tolerate a rate of 8-12 breaths/minute.

Tidal Volume (VT)

-The tidal volume is the volume of gas the ventilator delivers to the patient with each breath.

-The usual setting is 5-15 cc/kg, based on compliance, resistance, and type of pathology.

-Patients with normal lungs can tolerate a tidal volume of 12-15 cc/kg,

-Patients with restrictive lung disease may need a tidal volume of 5-8 cc/kg.


To start a patient on assist-control

one must select

-a PEEP (as determined by lung compliance),

-a minute volume (MV 100ml/kg),

-a tidal volume (TV 6ml/kg), and a peak flow.

-The respiratory rate is the MV/TV.

-The peak flow is usually four times the minute ventilation.

-The trigger is either set as “flow-by” or a negative pressure of -2cmH2O


Fractional Inspired Oxygen (FIO2)

-The fractional inspired oxygen is the amount of oxygen delivered to the patient.

It can range from 21% (room air) to 100%.

-Oxygen toxicity causes structural changes at the alveolar-capillary membrane, pulmonary edema, atelectasis, and decreased PaO2.

Inspiratory:Expiratory (I:E) Ratio

-The I:E ratio is usually set at 1:2 or 1:1.5

Pressure Limit

-The pressure limit regulates the amount of pressure the volume-cycled ventilator can generate to deliver the preset tidal volume.

-High pressures can cause lung injury, it’s recommended that the plateau pressure not exceed 35 cm H20.

-Caused by airway is obstructed with mucus,the patient coughing, biting on the ETT, breathing against the ventilator, or by a kink in the ventilator tubing.


Flow rate

  • -The flow rate is the speed with which the tidal volume is delivered. The usual setting is 40-100 liters per minute.
  • Sensitivity/Trigger
  • -The sensitivity determines the amount of effort required by the patient to initiate inspiration.
  • It can be set to be triggered by pressure or flow
  • Sigh
  • -The ventilator can be programmed to deliver an occasional sigh with a larger tidal volume.
  • it prevents collapse of the alveoli (atelectasis)
  • Minute volume (VE)
  • Minute volume is the total volume of air inhaled and exhaled in one minute. The patient’s minute volume should be less than 10 liters per minute.

Ventilator Settings

The following is a summary of the settings that nurses deal with the most.


Respiratory Rate (RR) Number of breaths delivered usually 4-20 breaths/mt

by the ventilator per minute

Tidal Volume (VT) Volume of gas delivered during usually 5-15cc/kg

each ventilator breath

Fractional Inspired Amount of oxygen delivered by 21%-100% to keep

Oxygen(FIO2) ventilator to patient PaO2>60mmHg or


Inspiratory:Expiratory Ratio Length of inspiration usually 1:2 or 1:1.5

(I:E) compared to length of expiration

Pressure Limit Maximum amount of pressure 10-12cm H2O above

the ventilator can use to PIP; maximum35cmH2O

deliver breath


Alarms and Common Causes

  • High Pressure Low Pressure High Respiratory Rate Low Exhaled Volume
  • Secretions in -vent tubing not –patient anxiety or -vent tubing not
  • ETT/airway or connected pain connected
  • condensation in -displaced ETT -secreations in ETT/ -Leak in cuff or
  • tubing or trach tube airway inadequate cuff seal
  • • Kink in vent - Hypoxia
  • Tubing - Hypercapnia -Occurrence of
  • • Patient biting on another alarm
  • ETT preventing full
  • • Patient coughing, delivery of breath
  • gagging, or trying
  • to talk
  • • Increased airway
  • pressure from
  • bronchospasm or
  • pneumothorax

Noninvasive Forms of Mechanical Ventilation

Noninvasive positive pressure ventilation (NIPPV) include

- patients who don’t have oxygenation problems,

- who are able to manage their secretions, and

- who don’t have an upper airway obstruction.


Continuous Positive Airway Pressure (CPAP)

CPAP can also be delivered through either a nasal mask or a full face mask.

Full face masks- minimize air leaks,

-more claustrophobic- must be removed for the patient to speak or expectorate secretions.

- a smaller air leak leads to greater pressure buildup and gastric distention

Nasal masks - less claustrophic and don’t have to be removed to speak or expectorate,

- they usually have large air leaks BiPAP


Bi-level Positive Airway Pressure (Bi-PAP)- similar to CPAP - BiPAP maintains positive airway pressure during both inspiration and expiration. -The two levels are referred to as inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP). -Benefits of IPAP increased tidal volume and minute ventilation, decreased PaCO2 level, relief of dyspnea, and reduced use of accessory muscles. -Benefits of EPAP increased functional residual capacity, resulting in an increased PaO2 level. -Bi-Pap is usually delivered through a nasal mask, allowing exhalation through the mouth



-Intermittent Positive Pressure Breathing (IPPB) is used after surgery or for a short time after mechanical ventilation has been discontinued.

-The IPPB machine is a pressure-cycled ventilator that delivers compressed

gas under positive pressure into the patient’s airway.

-It’s triggered when the patient inhales,but it allows passive expiration.

-Usually, 10-20 breaths are given every 1-2 hours for 24 hours.

-Benefits of IPPB include

prevention of atelectasis,

promotion of full-lung expansion,

improved oxygenation, and

administration of nebulized medications.

Nursing Care of the

Mechanically Ventilated Patient


Nursing Care of the Mechanically Ventilated Patient

Nursing Care of the Endotracheal Tube (ETT)

ETT management consists of

- ensuring a patent airway,

- suctioning pulmonary and oral secretions, and

- providing frequent oral and/or nasal care.

-secure ETT in place


Oral cavityshould also be suctioned separately

-oral care should be provided every eight hours and as needed.

Bite block -If the patient has a bite block to prevent them from biting on the tube, it must be removed and cleaned or replaced every eight hours.

-If the tube is taped to the patient’s face, the tape must be removed and replaced on the opposite side of the face at least once per day .

-The amount of air in the cuff should be checked every eight hours to ensure that the cuff is not exerting too much pressure on the trachea walls.

-ETT should be confirmed to be the same as prior to the procedure


Endotracheal tube care Tray

This includes -a sterile suction kit;

(two separate suction catheters for oral and ETT)

-a bottle of sterile 0.9% sodium chloride;

-sterile gloves;

-a clean bite block, and

-tape torn into appropriately sized pieces.

Nursing Care of the Tracheostomy Tube

-Tracheostomy (trach) care should be done every eight hours

and involves cleaning around the incision,

as well as replacing the inner cannula if the patient has a double-lumen tube.

-prevent breakdown of the skin surrounding the site,

and prevent infection.

-Using sterile technique, the skin and external portion of

the tube is cleaned with hydrogen peroxide.

- inner cannula must be cleaned with hydrogen peroxide, rinsed with 0.9% sodium chloride, and reinserted using sterile technique


Sterile suctioning

- Suctioning should be performed only when the patient needs it; the need should be assessed at least every two hours.

- Pre-oxygenation with 100% O2

- two separate suction catheters for oral and ETT

- size of suction catheter should be 1/3rd of ETT diameter

- Duration of each suction pass should be limited to ten seconds

-The number of passes should be limited to three or less

- saline installation should not be used routinely

  • Eyes should be covered with a sterile gauze after applying a eye ointment.
  • This is to avoid dryness of cornea & subsequent development of any ulceration.
naso gastric tubes
Naso gastric tubes
  • Instituted for gastric decompression
  • Administration of medications.
  • Nutritional support
  • Should be irrigated every 4 hours.
  • Position should be verified before administration of any fluids.
  • After administration flush with 10ml of water.
care of bladder
Care of Bladder

Continuous bladder drainage

Catheter should changed once in 72 hours – check patency

git care
GIT Care
  • Oral cavity examination
  • Abdominal Examination
  • Per Rectal Examination
care to avoid development of bed sore
Care to avoid development of bed sore
  • Constant changing position of patient
  • Avoid pressure points
  • Alpha bed or Water bed
psychological care
Psychological care
  • Good communication
  • Alleviate anxiety and promote emotional well being
  • Orientation of patient to surrounding, Time and Persons

Sedation & Neuromuscular Blockade

-Patients require sedation in order to tolerate mechanical ventilation

Common Medications

- sedatives decrease anxiety and produce amnesia

- neuroleptics,

- analgesics, and

- paralytics


Lorazepam Midazolam Propofol Dexmedetomidine

Onset of action5-15 minutes 1-3 minutes 1 minute Immediately

Half-life 6-15 hours 1 hour < 30 minutes 1.5-3 hours

Loading Dose0.05 mg/kg 0.03 mg/kg 0.5 mg/kg 1 mcg/kg

Infusion rate0.5-5 mg/hr 1-20 mg/hr 0.5-3mg/kg/hr 0.2-0.7 mcg/kg/hr



-Given to patients who are experiencing delirium or “ICU psychosis.”

Symptoms -disorganized thinking,

- audio and visual hallucinations, and

- disorientation.

Haloperidol - intravenously in 2-10 mg doses every 2 to 4 hours


Intravenous narcotics – Morphine,fentanyl or hydromorphone

PARALYTICS AGENTS or neuromuscular blocking agents (NMBs)

- must always be administered with other sedatives and narcotics

Two classes of NMBs: - Nondepolarizing (Succinylcholine – for intubation)

- Depolarizing ( Atracurium,Pancuranium,Vecuranium)


Assessment Criteria

Breath Sounds

- Breath sounds should be assessed at least every four hours

Crackles (rales)



Pleural friction rub

Spontaneous Respiratory Rate and Tidal Volume

-If the spontaneous tidal volume is low

-the patient may not do well with weaning attempts.

-If the respiratory rate is high, particularly with weaning modes indicate -the patient isn’t tolerating the mode,

-needs suctioning,

-or he or she is anxious or trying to communicate.

Pulse Oximetry

-The machine detects the percent of hemoglobin that is fully saturated. -pulse oximetry can be a helpful guide when titrating FIO2

-In general, a SpO2 of 92% in white patients, and 95% in black patients indicates adequate oxygenation (PaO2 > 60 mmHg).


(Capnography) End Tidal CO2

-Capnography, also called end tidal CO2, is CO2 measured at the end of exhalation

-a display where a waveform (capnogram) is created, along with a number that closely approximates the PaCO2

-In a hemodynamically stable patient with a normal ventilation/perfusion relationship, the end tidal CO2 (also called PetCO2) is generally 1-5 mmHg less than the PaCO2

-The most useful function of end tidal CO2 measurement is to confirm ETT placement in the lungs.


Arterial Blood Gases (ABG)


• Normal pH of body fluids = 7.35-7.45

• pH < 7.35 = acidosis

• pH > 7.45 = alkalosis


• PaCO2 is the partial pressure of dissolved CO2 in blood.

• Normal = 35-45 mmHg

• PaCO2 is directly related to rate and depth of respiration.

It’s a direct indicator of the effectiveness of ventilation.

• As PaCO2 rises, the blood becomes more acidic and pH drops.

• As PaCO2 decreases, the blood becomes more alkaline and pH rises.

• If a change in PaCO2 is the primary alteration, then a respiratory problem exists.


• Bicarbonate (HCO3) is the primary buffer in the body and is able to take up and release H+.

• Normal = 22-26 mmHg

• As HCO3 rises, the blood becomes more alkaline and pH increases.

• As HCO3 drops, the blood becomes more acidic and pH decreases.

• If a change in HCO3 is the primary alteration, then a metabolic problem exists.



• Considered a measure of bicarbonate concentration; includes total of bicarbonate and carbonic acid.

• Normal = 23-27 mEq/L

Base Excess/Deficit

• Measures excess amount of acid or base present in blood. This is independent of changes in PaCO2; therefore, it’s a measure of metabolic acid-base balance.

• Increased HCO3 = base excess (alkalosis)

• Decreased HCO3 = base deficit (acidosis)


• The amount of oxygen dissolved in plasma (about 3% of total; the other 97% is bound to hemoglobin).

• Normal is 80-100 mmHg in healthy young people breathing room air at sea level; this decreases with age and altitude.

• PaO2 > 60 mmHg is considered acceptable in critically ill, mechanically ventilated adults


Figure out the ABG results

  • pH 7.30, PaCO2 40, HCO3 18
  • Metabolic acidosis (pH , PaCO2 ok, HCO3 )
  • 2. pH 7.48, PaCO2 30, HCO3 24
  • Respiratory alkalosis (pH , PaCO2 , HCO3 ok)
  • 3. pH 7.25, PaCO2 54, HCO3 26
  • Respiratory acidosis (pH , PaCO2 , HCO3 ok)
  • 4. pH 7.50, PaCO2 42, HCO3 33
  • Metabolic alkalosis (pH , PaCO2 ok, HCO3 )

Indications for weaning and extubation:

The patient is able to ventilate

The patient is able to oxygenate

The patient is able to protect his/her airway

  • Increased HR
  • Increasrd RR (>30/mt)
  • Increased work breathing
  • Sweating (Hypercapnia)
  • Hypertension
  • Hypoxia

Does the patient meet criteria?

How do I know if the patient is tolerant

intolerant of the trial?

Is the patient suitable for extubation?


Other Factors

Is the patient suitable for extubation?



Weaning & Extubation

Partial Ventilation Support

Normalization of inspiratory times

Driving pressure is targeted to

a tidal volume of 4 - 6ml/kg.

Mean airway pressure, the CPAP level and the FiO2 are reduced to targeted PaO2

As PaCO2 reduces reduce the controlresp.rate


Failure to Wean:

Is the patient able to ventilate?

Is the patient able to oxygenate?

What other factors influence weaning?

Is the patient able to ventilate?



Anatomical Problems


Is the patient able to oxygenate?

  • Diffusion abnormalities,
  • ventilation-perfusion mismatch,
  • dead space and shunt.
  • Certain factors may limit successful weaning
  • - persistent lower respiratory tract infection,
  • -alveolar edema,
  • -airway/lobar collapse,
  • -lung fibrosis.

What other factors influence weaning?

Cardiovascular – pulmonary edema,fluid overload

Gastroinestinal – recurrent aspiration pneumonitis,

ascites or abdominal wounds leading to

diaphgramatic splinting

Nutrition -protein malnutrition leading to muscular atrophy,

which affects the diaphragm and intercostals

Acid base – metabolic alkalosis reduces respiratory drive.

Conversely, muscles perform poorly in an acidic environment

Electrolytes– hypophosphatemia, hypomagnesemia, hypokalemia, hypocalcemia:

these all affect muscular function and protein metabolism.

Endocrine – muscle weakness due to hypothyroidism or steroid induced myopathy.

Oxygen delivery capacity – the circulating hemoglobin concentration:

anemia increases respiratory drive and cardiac output

Pain control – it is very difficult to wean patients who are in pain


Weaning & Discontinuation Algorithm

  • Removing a patient from a ventilator involves discontinuation of mechanical ventilation and extubation.
  • There are two parts to weaning: weaning to partial ventilator support and weaning to discontinuation.
  • The single most traumatic event for the patient is conversion from positive pressure to negative pressure ventilation.
  • To extubated a patient, they need to be awake, able to cough and protect their airway.
  • If it is possible to wean a patient to extubation, but the patient cannot protect his/her airway, it is best to perform tracheotomy.

6. For a patient to self ventilate, many body systems must be functioning:

-the cardiopulmonary apparatus,

-the central nervous system,

-the nerves that supply the diaphragm (including the neuromuscular junctions),

-the muscles themselves.

-Moreover the patient must be willing to breath and maintain their own

functional residual capacity (not if there is diaphragmatic splinting due to pain).

-There must be room in the abdomen for the diaphragm and lungs to move into.

-There must be adequate hemoglobin to deliver oxygen to the tissues.

7. Difficult to wean a patient if ongoing inflammatory processes persist in the lungs:

consolidation, fibrosis, auto-PEEP, diffusion defects

8. Muscles must be trained and nourished, and patient-ventilator interaction encouraged

9. most effective method of weaning to discontinuation is spontaneous breathing trials

(SBT). SBTs should not be performed more than once daily.


Methods of weaning

  • There are three primary methods
      • T piece/CPAP trials,
      • Synchronized Intermittent Mandatory Ventilation (SIMV),
      • Pressure Support Ventilation (PSV).
  • PSV is often used with SIMV to decrease the work of breathing.

T-piece/CPAP trials

-T-piece trials consist of alternating intervals of time on the ventilator with intervals of spontaneous breathing.

-T-shaped tube is attached

- endotracheal or tracheostomy tube. - tubing is attached to an oxygen flowmeter

-the other end is open

-watch for signs of hypercapnia






- With CPAP, the patient breathes spontaneously, but has the benefit of the ventilator alarms if he or she has difficulty.

- CPAP maintains constant positive pressure in the airways, which facilitates gas exchange in the alveoli.



-SIMV is a ventilator mode that delivers a preset number of breaths to the patient but coordinates them with the patient’s spontaneous breaths.

-Theventilator may be set to deliver 12 breaths per minute, but the patient’s respiratory rate may be 16 (12 ventilator breaths plus 4 patient-initiated breaths).

-The ventilator rate is usually decreased by one to three breaths at a time and an arterial blood gas (ABG) is obtained 30 minutes after the change

Pressure support

- Placing the patient on the pressure support mode at a level that allows the patient to achieve a spontaneous tidal volume of 10-12 ml/kg.

- During weaning, the level of PS is decreased by 3-5 cm H2O as long as the

patient maintains the desired tidal volume.


Weaning criteria

Simple bedside pulmonary function tests

Vital capacity (VC)

-The vital capacity is the maximal amount of air that can be exhaled after a maximal inhalation.

-The patient’s vital capacity should be at least 10-15 cc/kg.

Negative inspiratory force (NIF)

-Negative inspiratory force is the ability to take a deep breath and to generate a cough strong enough to clear secretions.

-The patient’s NIF should be at least –20 cm H20.

Tidal volume (VT)

-Tidal volume is the volume of air inspired and expired during a normal respiratory cycle.

-The patient’s tidal volume should be at least 5 ml/kg


Minute volume (VE)

-Minute volume is the total volume of air inhaled and exhaled in one minute.

-The patient’s minute volume should be less than 10 liters per minute.

Respiratory rate (RR)

-The respiratory rate is the number of breaths per minute. The patient’s RR should be less than 25 breaths/minute.

Arterial blood gas (ABG)

-An ABG should be done before the patient is extubated. The PaO2 should be at least 50 mmHg on less than 50% oxygen and with no more than 5 cm H20 PEEP.


Post-Extubation Care

Humidified oxygen

-Supplemental oxygen requires humidification to prevent drying and irritation of the respiratory tract and to facilitate removal of secretions.

-oxygen delivered through a mask for a few hours after extubation.

Respiratory exercises

-coughing and deep breathing.

-incentive spirometry exercises.


-is used in some institutions to assist patients to take deeper breaths, especially after surgery.

-The IPPB machine is a pressure-cycled ventilator that delivers compressed gas under positive pressure into the patient’s airway.

-It’s triggered when the patient inhales, but it allows passive expiration.


-10-20 breaths are given every 1-2 hours for 24 hours.

-Benefits of IPPB

-prevention of atelectasis,

-promotion of full-lung expansion,

-improved oxygenation, and

-administration of nebulized medications

Assessment and monitoring

- Breath sounds, pulse oximetry, and vital signs should be assessed and recorded every 15 minutes x 1 hour, every 30 minutes x 1 hour, then every hour until stable

- ABG to be done 30-60 minutes after extubation

-Don’t forget to ask the patient how his or her breathing feels