II. Indications

III. History

  1. First described by Andreas Vesalius in 1555
  2. Negative pressure Ventilators (IronLung) first used
  3. Positive pressure Ventilator first used in 1955
    1. Response to Polio epidemic of 1955
    2. Emerson company tested at Massachusetts General

IV. Types

  1. Volume cycled Ventilators
    1. Newer devices
    2. Deliver constant volume independent of lung mechanics
    3. Best initial setting for most patients (unless pressure needs to be limited)
      1. Example ideal patient: Metabolic Acidosis
  2. Pressure Cycled Ventilators
    1. Initial Ventilator design
    2. Inflates lungs until preset pressure is reached
    3. Requires preset of ventilation duration (length of time pressure is applied, e.g. 1 second)
      1. Greater volume is administered when a given pressure is applied for a longer duration
    4. Difficult to keep inflation volume constant
    5. Best for patients for whom you wish to set a maximum inspiratory pressure
      1. Example ideal patient: ARDS (stiff lungs)

V. Physiology

  1. Ventilators function as a mechanical bellows
  2. Cardiac Output
    1. Enhanced by modest thoracic positive pressure
      1. Reduces left Ventricular Afterload
    2. Decreased by excessive intrathoracic pressure
      1. Reduces diastolic ventricular filling (Preload)

VI. Technique: Ventilation Modes

  1. Assist Control (AC)
    1. Assist
      1. Patient initiates mechanical breath, and a preset Tidal Volume is delivered
    2. Control
      1. Provides ventilations that are not patient initiated at a back-up rate
    3. Indications
      1. Obtunded patient without respiratory drive
      2. Pneumonia with Sepsis (decrease work of breathing)
    4. Advantages over SIMV Mode
      1. Decreased work of breathing
      2. Decreased respiratory muscle Fatigue
      3. Better response to patient's Ventilatory needs
    5. Disadvantages
      1. Risk of breath stacking (multiple full Tidal Volume breaths) and secondary Respiratory Alkalosis
        1. Increased risk in awake or agitated patients
    6. Presets
      1. Tidal Volume
      2. Respiratory Rate
      3. Fraction of Inspired Oxygen (FIO2)
      4. Positive End-Expiratory Pressure (PEEP)
  2. Synchronized Intermittent Mandatory Ventilation (SIMV)
    1. Intersperses spontaneous breath with machine breaths
    2. Two phases of cycle: SIMV and Spontaneous
      1. SIMV Phase
        1. Any patient initiated breath is supported with delivery of a preset Tidal Volume
        2. If no patient initiated breath in first 90% of SIMV, machine delivers a full breath
      2. Spontaneous Phase
        1. Patient initiated breaths will not trigger any additional support from the Ventilator
        2. Ventilation Tidal Volume is 100% dependent on patient's own unsupported inspiration
    3. Machine breaths synchronized (SIMV)
      1. Given at start of spontaneous breaths
    4. Indications
      1. Introduced in 1971 for neonates with RDS
      2. Often used for Ventilator Weaning of adults
      3. May be used if Respiratory Rate is rapid
    5. Advantages over Assist Control Mode
      1. Less Respiratory Alkalosis
      2. Improves Cardiac Output
      3. Prevents respiratory muscle atrophy
    6. Presets
      1. See Assist Control above
  3. Pressure Support Ventilation (PSV)
    1. Indications
      1. Ventilator Weaning
      2. Intubation for airway protection (e.g. Angioedema)
        1. Use AC or SIMV first until RSI wears off and patient starts to wake up
    2. Augments spontaneous breathing (as with SIMV)
    3. Augments every breath (as with assist mode)
    4. Inspired gas to desired pressure (typically starts at 12-15 cmH2O)
    5. Advantages over SIMV
      1. Increases Tidal Volume
      2. Decreases work of breathing
    6. Methods of Setting Pressure
      1. Method 1: Maximum Inspiratory Pressure
        1. Pressure = Maximum Inspiratory Pressure / 3
      2. Method 2: Proximal Airway Pressure
        1. Pressure = Peak Pressure - Plateau Pressure
      3. Method 3: Approximation
        1. Start with pressure 12-15 cmH2O (normal lung compliance, non-rigid chest wall)
        2. Adjust based on observation of first few breaths (increase pressure if TV too low)
    7. Presets (patient controls Respiratory Rate, flow rate and Tidal Volume)
      1. Inspiratory pressure
      2. Fraction of Inspired Oxygen (FIO2)
      3. PEEP Pressure

VII. Technique: Starting Parameters

  1. General
    1. Assist Control is a default Ventilator setting appropriate for most patients
    2. Measure the patient length on presentation (to estimate Ideal Weight, and hence Tidal Volume)
  2. Lung Injury (most cases)
    1. Tidal Volume
      1. Setting: 6 ml/kg Ideal Body Weight (lung protective strategy)
      2. Key parameter in lung injury
    2. Inspiratory flow rate (IFR)
      1. Setting: 60-80 lpm
      2. Adjust for patient comfort (faster breaths tend to be more comfortable)
    3. Respiratory Rate
      1. Setting: 16-18 breaths per minute
      2. Increase or decrease based on pCO2 (increase RR to decrease pCO2)
    4. FIO2
      1. Start for first 5 minutes at 100% FIO2 with PEEP 0-5
      2. Obtain Arterial Blood Gas (after first 15 minutes on Ventilator)
      3. Decrease FIO2 toward 30% with PEEP 5, with a goal Oxygen Saturation >90% (and <95%)
      4. Titrate up on FIO2 and PEEP together at 5-10 min increments based on PEEP table (see below)
    5. PEEP
      1. Adjust PEEP in concert with FIO2 based on PEEP tables
    6. Monitoring
      1. Goal PaO2 55-80 mmHg (Oxygen Saturation 88-95%)
      2. Decrease Tidal Volume until plateau pressure <30 cm H2O (see below)
  3. Obstructive Lung Disease (Asthma, COPD)
    1. Precautions
      1. Consider Delayed Sequence Intubation
      2. Status Asthmaticus patients will often respond to aggressive Asthma Management AND BiPap
        1. Asthma patients who require intubation have lost all respiratory drive
      3. Expect a high peak pressure in Asthma due to airway resistance
        1. High peak pressure does not adversely effect the patient
          1. Set peak pressure alarm to trigger >80 cm H2O
        2. However, do not confuse peak pressure with plateau pressure
          1. Plateau pressure >30 cm H2O is a sign of breath stacking and must be corrected
          2. Decrease plateau pressure by decreasing Respiratory Rate
      4. Continue Nebulized Albuterol via Endotracheal Tube
    2. Tidal Volume
      1. Dose: 8 ml/kg Ideal Body Weight
    3. Inspiratory flow rate (IFR)
      1. Setting: 80-100 L/min
      2. Increase to provide faster breath, completes early in cycle (allows greater expiratory time)
    4. Respiratory Rate (RR)
      1. Set rate at 10 breaths per minute (do not set this too high)
      2. Most important parameter in Obstructive Lung Disease ventilation
      3. Allows for full expiration (typical I:E ratio 1:4 or 1:5) and prevents breath stacking
    5. FIO2
      1. Start at 40% and titrate
    6. PEEP
      1. Minimal (0-3 mmHg) to NO PEEP ("PEEP Zero Strategy") is recommended in Obstructive Lung Disease
    7. Monitoring
      1. Check plateau pressure for breath stacking
        1. Decrease Respiratory Rate until plateau pressure <30 cm H2O
      2. Follow Arterial Blood Gas
        1. Permissive hypercapnia is goal in Obstructive Lung Disease ventilation
        2. Expect pCO2 50-70 mmHg (maintain pH > 7.1)
  4. References
    1. Weingart and Orman in Herbert (2016) EM:Rap 16(6):14-5
    2. http://emcrit.org/wp-content/uploads/vent-handout.pdf
    3. http://emcrit.org/archive-podcasts/vent-part-1/
    4. http://emcrit.org/podcasts/vent-part-2/

VIII. Technique: Parameters

  1. Tidal Volume (TV)
    1. Ventilator Tidal Volume: 6-8 ml/kg of Ideal Body Weight
      1. Prior levels of 10 to 15 ml/kg thought too high
      2. ARDS: Start at 6 ml/kg based on Ideal Body Weight (lung protective strategy)
    2. Indications to Reduce Tidal Volume
      1. Lung Resection history (reduce Tidal Volume by percent loss in lung)
      2. Plateau pressure >30 cmH2O
        1. In Obstructive Lung Disease, decrease RR first (indicates breath stacking)
    3. Indications to Increase Tidal Volume
      1. Stiff Lungs (e.g. Pulmonary edema)
        1. High Peak Inflation Pressure (>20-40 cm H2O)
        2. Results in large loss of Tidal Volume in tubing
  2. Respiratory Rate (RR, "Ventilation")
    1. Set at 12 to 14 breaths per minute (many patients may require 16-18, esp. lung injury)
    2. Ensures adequate carbon dioxide removal
    3. Keep to a minimum to avoid Respiratory Alkalosis
    4. Increased Respiratory Rate needed in Metabolic Acidosis
      1. Observe patient's own Respiratory Rate prior to intubation and use as a guide
      2. Recheck Arterial Blood Gas (ABG) at 20 minutes after initial settings
    5. Indications to decrease Respiratory Rate
      1. Obstructive Lung Disease with breath stacking
  3. Fraction of Inspired Oxygen (FIO2)
    1. Start: 80% or higher
    2. Titrate: decrease in 10-20% steps
    3. Goal: Keep FIO2 <60% (<50% if possible)
      1. Higher FIO2 is associated with Oxygen Toxicity
      2. Target Oxygen Saturations 88-94%
      3. Increasing PEEP can reduce FIO2 requirements (see below)
    4. Monitoring: Arterial Blood Gas
      1. Wait 20 minutes after each change in FIO2
      2. Keep PaO2 60 to 80 mm Hg (90-95% O2 Sat)
  4. Inspiratory flow rate (IFR)
    1. Describes how quickly a breath is delivered (anologous to Peak Flow)
    2. Faster breaths tend to be more comfortable, and result in less Air Hunger sensation for patient
    3. Adjust for patient comfort
  5. Positive End-Expiratory Pressure (PEEP)
    1. Prevents distal airspace collapse (especially dependent lung fields)
    2. Most important in shunting of blood past collapsed alveoli (e.g. Pneumonia, Atelectasis)
    3. Start PEEP at 5 cm H2O (minimum)
    4. Higher PEEP Indications
      1. Extensive alveolar collapse (8-10 cm H2O)
      2. Obesity or pregnancy
      3. High FIO2 (esp. >60%) required or Hypoxemia refractory to oxygenation
        1. Goal Oxygen Saturation 88-95% (PaO2 55-80 mmHg)
        2. FIO2 30%: Set PEEP 5 cmH2O (high PEEP to FIO2: 5-8-10-12-14 cmH2O)
        3. FIO2 40%: Set PEEP 5-8 cmH2O (high PEEP to FIO2: 14-16 cmH2O)
        4. FIO2 50%: Set PEEP 8-10 cmH2O (high PEEP to FIO2: 16-18-20 cmH2O)
        5. FIO2 60-80%: Set PEEP 10-14 cmH2O (high PEEP to FIO2: 20 cmH2O)
        6. FIO2 90%: Set PEEP 14-18 cmH2O (high PEEP to FIO2: 22 cmH2O)
        7. FIO2 100%: Set PEEP 18-24 cmH2O (high PEEP to FIO2: 22-24 cmH2O)
        8. http://www.ardsnet.org/files/ventilator_protocol_2008-07.pdf
    5. Precautions: Excessive PEEP
      1. Lung injury risk (alveolar over-distention)
      2. Hypotension risk (increased intrathoracic pressure decreases venous return)
        1. Decrease PEEP if hypotensive response to increasing PEEP
  6. Plateau pressure
    1. Example: Invoke by holding down "inspiratory hold button" for 5 seconds
    2. NOT the same as peak inspiratory pressure (which is typically very high in Obstructive Lung Disease)
    3. Strategy if plateau pressure too high (>30 cm H2O)
      1. Lung Injury
        1. Decrease Tidal Volume until plateau pressure <30 cm H2O
      2. Obstructive Lung (breath stacking)
        1. Decrease Respiratory Rate until plateau pressure <30 cm H2O

IX. Technique: Adjunctive measures

  1. Paralytic Agents
    1. No longer routinely recommended due to Myopathy
    2. Advantages
      1. Reduced oxygen demands
      2. Improved Metabolic Acidosis
      3. Reduced barotrauma
    3. Indications
      1. Ventilator-patient desynchrony
      2. High peak airway pressure
      3. Failed response to Sedation
    4. Complications
      1. Myopathy (exacerbated by Corticosteroids)
      2. Increased Deep Vein Thrombosis risk
      3. Unable to assess mental status
    5. Pearls
      1. Define lowest effective dose with nerve stimulator
      2. Hold infusion every 4-6 hours (avoids accumulation)
      3. Concurrent Sedation is imperative (see below)
  2. Use adequate Sedation
    1. Paralytic Agents do not sedate
    2. Adult doses
      1. Dexmedetomidine (Precedex)
      2. Midazolam 1-2 mg IV prn
      3. Propofol 60-80 mg IV or 50-100 ug/kg/min
      4. Lorazepam 1-2 mg IV prn
  3. References
    1. Cornwell (2003) UW New Therepeutics Lecture, Cable,WI

X. Adverse Effects

  1. Barotrauma
  2. Severe Respiratory Alkalosis
    1. Occurs with high Respiratory Rates
    2. Consider IMV ventilation mode or patient Sedation

XI. Evaluation: Monitoring parameters

  1. Arterial Blood Gas (ABG)
    1. Obtain 15-20 minutes after intubation, acute Resuscitation, status change, Ventilator change
  2. Oxygen Saturation (O2 Sat)
    1. Target 88-94% Oxygen Saturations
  3. End-Tidal CO2 (EtCO2)
    1. Note the EtCO2 at the time of each ABG
      1. Determine the difference between the PaCO2 and the EtCO2 (PaCO2 to EtCO2 gap)
    2. EtCO2 can be followed as an ABG surrogate during Ventilator setting adjustments
      1. No significant change in patient status
      2. Consistent PaCO2 to EtCO2 gap

XII. References

  1. Marino (2014) ICU Book, Walters-Kluwer, Philadelphia
  2. Nugent (2011) Bedside Guide to Mechanical Ventilation, 1st ed
  3. Owens (2012) Ventilator Book, First Draught Press

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Ontology: Ventilator - respiratory equipment (C0087153)

Definition (UMD) Devices designed to provide temporary ventilation and/or respiratory assistance by delivering an appropriate volume of gas to the respiratory airways. Most ventilators deliver gas to the lungs using positive pressure by means of a mouthpiece, mask, tracheostomy, or an endotracheal tube, but some of them (e.g., tank ventilators) are based on the application of negative pressure to the body surface or chest wall. Ventilators are used in patients who cannot breathe on their own or who require assistance to maintain adequate ventilation because of illness, trauma, congenital defects, or drugs including anesthetics.
Definition (NCI) A medical device that facilitates breathing.
Definition (NCI_NCI-GLOSS) In medicine, a machine used to help a patient breathe.
Concepts Medical Device (T074)
MSH D012122
SnomedCT 78645005
LNC LP7706-7, MTHU008126
German Beatmungsgeräte
English respiratory equipment ventilator (treatment), respiratory equipment ventilator, ventilator, ventilators, respirator, Ventilator, Ventilators, Ventilator - respiratory equipment
French Ventilateurs
Norwegian Ventilatorer

Ontology: Mechanical ventilation (C0199470)

Definition (NCI) A method to mechanically assist or replace spontaneous breathing in patients by use of a powered device that forces oxygenated air into the lungs.
Definition (NIC) Use of an artificial device to assist a patient to breathe
Concepts Therapeutic or Preventive Procedure (T061)
MSH D012121
SnomedCT 182685002, 25638009, 182688000, 150946007, 150950000, 78563003, 150947003, 40617009
English Mechanical Ventilations, Ventilations, Mechanical, Mech assisted breathing, Mech assisted ventilation, Mechanical respirat assist NOS, Mechanical respiratory assistance NOS, mechanical respiratory assist, mechanical ventilation (treatment), mechanical ventilation, Mechanical ventilation NOS, Mechanical Ventilation, Ventilation-mechanical, Mechanical ventilation (procedure), Mechanical respiratory assistance NOS (procedure), Mechanical assistance to resp., Respiratory assist, mechanical (procedure), Respiratory assist, mechanical, Mechanically assisted breathing, Mechanically assisted ventilation, Mechanical ventilation, NOS, Mechanical ventilation (procedure) [Ambiguous], Mechanical ventilation, Ventilation, Mechanical
Dutch mechanische beademing, Ventilatie, mechanische
French Ventilation artificielle, Ventilation mécanique
German mechanische Beatmung, Beatmung, mechanische
Portuguese Ventilação artificial, Ventilação Mecânica
Spanish Ventilación mecánica, Ventilación Mecánica, asistencia respiratoria mecánica, SAI, asistencia respiratoria mecánica, SAI (procedimiento), ventilación mecánica (procedimiento), ventilación mecánica, Mechanical respiratory assistance NOS, asistencia respiratoria, mecánica, asistencia respiratoria, mecánica (concepto no activo), ventilación mecánica (concepto no activo)
Japanese 機械的換気, キカイテキカンキ
Czech Mechanická ventilace, mechanická ventilace
Hungarian Gépi lélegeztetés
Norwegian Mekanisk lufttilførsel, Mekanisk åndedrett, Mekanisk ventilasjon
Italian Ventilazione meccanica

Ontology: Assisted controlled mandatory ventilation (C0419014)

Concepts Therapeutic or Preventive Procedure (T061)
SnomedCT 243150007
English Assisted contr mandat ventilat, Assist control, Assisted controlled mandatory ventilation, Triggered ventilation, Assisted controlled mandatory ventilation (procedure)
Spanish ventilación asistida controlada obligatoria (procedimiento), ventilación asistida controlada obligatoria