A. Negative Pressure Ventilators (Extrathoracic)
1. Negative pressure (suction) is applied to the outside of the chest.
2. This force causes the chest to rise and expand (inspiration).
3. Ventilation is controlled by adjusting the length of inspiration (time-cycled) and the amount of suction.
4. Chest shell must be correct size for proper fit to prevent leaks.
5.Indicated for intermittent use, home care and patients with neuromuscular pathologies. 6. Examples of this type of ventilator include:
a. lron Lung (Body Tank).
b. Chest Cuirass - see picture above.
7. Troubleshooting.
a. Chest cuirass is hissing and unable to reach pressure, check for leaks.
b. lf patient is breathing faster than the rate set on the ventilator, increase the set rate to match the patient.
B. Positive PressureVentilators (lntrapulmonary Pressure)
1. The ventilator creates a positive pressure that will push air into the patient's lungs and increase intrapulmonary pressure.
2. The amount of air that is delivered depends upon the amount of pressure applied and how long it is applied. Side effects of positive pressure
ventilation include:
a. Decreased venous return.
b. Increased intrathoracic pressure.
c. Increased intracranial pressure.
d. Decreased cardiac output.
3. Exhalation is passive and begins when the pressure is terminated and the exhalation valve opens.
C. Types of Positive Pressure Ventilators
There are three (3) types of positive pressure ventilators.
1. Volume Cycled.
a. Pressure is applied to the airways until a preset volume is delivered.
b. Minute volume will remain constant to provide stable blood gases. Airway pressure will increase or decrease with changes in the patient's
compliance and/or airway resistance.
c. Volume cycled ventilators can be used with most patients.
d. Most common approach for mechanicalventilation.
2. Pressure Cycled.
a. These ventilators are normally pneumatically powered (50 PSI) and apply positive pressure to the airways until a preset pressure limit is
reached.
b. Tidal volume (Vr) is adjusted by increasing or decreasing the pressure limit.
c. Although peak pressure will remain constant, the volume will change as lung compliance and/or airway resistance change.
d. This type of ventilator is best for intermittent therapy (IPPB) or continuous ventilation for patients with normal lungs (Post-Op, Neuro,etc.).
e. Examples: Bird Mark 7.
Bennett PR-2.
3. Time Cycled.
a. These ventilators apply positive pressure until a preset time is reached.
b. The peak inspiratory pressure (PlP) is usually limited by an adjustable pop-off valve.
c. TidalVolume (V1) is adjusted by increasing or decreasing the peak inspiratory pressure, inspiratory time, or flow.
d. Commonly used for infant ventilation.
D. Fluidic Ventilators
1. Pressure-limited ventilators.
2. Often used during the inspiratory cycle and expiratory phase on pressure-limited ventilators; enabling the ventilator to switch back and forth
between inspiration and exhalation.
E. Home Ventilators
1. Many negative pressure and positive pressure ventilators can be used in the home setting.
2. A backup ventilator should be provided for any patient who requires ventilation the majority of the time.
3. Non-invasive ventilators and CPAP devices are often utilized in the home setting.
F.Transport Ventilators
1. Should be portable and lightweight.
2. Duration of flow must be considered when using air and oxygen cylinders to power the ventilator.
3. lf respiratory rate or tidal volume decreases on pneumatic transport ventilator - check the cylinder pressure.
4. Many different models are available for use; should be able to meet the patient's demands.
G.Microprocessor Ventilators
1. Used with volume-cycled flow-limited ventilation or pressure-limited time-cycled (pressure control) ventilation.
2. Ventilator rate, mean airway pressure (Paw), peak and plateau pressures, volumes, compliance, etc. can all be easily monitored.
3. Can provide pressure control ventilation (PCV) and pressure support ventilation (PSV).
H.Ventilator Circuit
1. Typical ventilator circuit includes:
a. Inspiratory limb.
b. Expiratory limb.
c. Wye adaptor.
d. Nebulizer.
e. Humidifier.
I.Changing Ventilator Circuits
1. Ventilator circuits should not be changed on a regular basis unless:
a. Circuit is grossly contaminated.
b. Malfunctioning.
2. The patient should be off the ventilator for the shortest possible amount of time.
3. Manual ventilation with a resuscitation bag will be necessary while the new circuit is attached and tested by another person.
4. Pre and post oxygenate with 100% 02 to prevent iatrogenic hypoxemia.
J. Ventilator Alarms
1. Common Alarms.
a. High pressure limit (set 10 cmH2O above peak airway pressure).
b. Minimum exhaled volume (set 100 mL below exhaled tidal volume).
c. Low pressure limit (set 10 cmH2O below peak airway pressure).
d. Oxygen alarm (set 5% above and below set FrOz).
e. PEEP/CPAP (high and low level).
f. Failure to cycle (check power supply).
g. Loss of power (check power supply).
h. Oxygen failure (check oxygen source).
i. Temperature alarm (set low and high level).
2. Troubleshooting: alwavs provide manual ventilation first.
a. Low pressure alarm - consider:
1. Patient disconnect.
2. Leak in the ventilator circuit.
3. Insufficient flow.
4. Endotracheal/tracheostomy tube cuff leak.
b. High pressure alarm - consider:
1. Patient obstruction (endotracheal tube, pneumothorax, t Raw, secretions, etc).
2. Equipment obstruction (ventilator circuit).
c. Low exhaled volume alarm - consider:
1. Patient disconnect (ventilator circuit).
2. Low spontaneous tidal volume.
d. Temperature alarm.
1. High temperature alarm - check humidifier temperature.
2. Low temperature - check humidifier temperature, may decrease during aerosol therapy.
3. Example:
Question: A patient who is being mechanically ventilated has received an aerosol treatment inline with the ventilator circuit.
Following the treatment, the high temperature alarm is sounding. Why would this occur and how should the respiratory
therapist correct the problem?
Answer: The high temperature alarm sounded because the flow of the aerosol caused the temperature probe to cool down.
The humidifier responded by increasing its temperature. Once the treatment is completed the cooling stops, so the air
temperature rises. To correct the problem, adjust the temperature setting on the humidifier.
K.Time Cycled Pressure-Limited Ventilators
1. General Principles.
a. Continuous flow provided between breaths for spontaneous breathing (lMV).
b. Inspiration begins and ends according to preset inspiratory time.
c. Maintains preset pressure limit using pressure popoff.
d. Volume delivered demands close monitoring because it varies with EVERYTHING.
1) Pressure Limit.
2) Flowrate.
3) Inspiratory Time.
4) Compliance (Lung and machine tubing).
5) Airway Resistance (Patient and machine tubing).
6) Patient effort during spontaneous breathing.
7) CPAP or PEEP changes.
2. lnitial Settings for Infants.
a. Mode :IMV.
b. Peak Inspiratory Pressure (PlP) :20 - 30 cmH2O.
c. Respiratory Rate :20 - 30 breaths/min.
d. Inspiratory time (lT) :0.5 - 0.6 seconds.
e. Flow :5 - 6 L/min.
f. Fro2 :40 - 60 % or Set at same level prior to ventilation.
g. PEEP :+2 - +4 cmH2O.
1. Negative pressure (suction) is applied to the outside of the chest.
2. This force causes the chest to rise and expand (inspiration).
3. Ventilation is controlled by adjusting the length of inspiration (time-cycled) and the amount of suction.
4. Chest shell must be correct size for proper fit to prevent leaks.
5.Indicated for intermittent use, home care and patients with neuromuscular pathologies. 6. Examples of this type of ventilator include:
a. lron Lung (Body Tank).
b. Chest Cuirass - see picture above.
7. Troubleshooting.
a. Chest cuirass is hissing and unable to reach pressure, check for leaks.
b. lf patient is breathing faster than the rate set on the ventilator, increase the set rate to match the patient.
B. Positive PressureVentilators (lntrapulmonary Pressure)
1. The ventilator creates a positive pressure that will push air into the patient's lungs and increase intrapulmonary pressure.
2. The amount of air that is delivered depends upon the amount of pressure applied and how long it is applied. Side effects of positive pressure
ventilation include:
a. Decreased venous return.
b. Increased intrathoracic pressure.
c. Increased intracranial pressure.
d. Decreased cardiac output.
3. Exhalation is passive and begins when the pressure is terminated and the exhalation valve opens.
C. Types of Positive Pressure Ventilators
There are three (3) types of positive pressure ventilators.
1. Volume Cycled.
a. Pressure is applied to the airways until a preset volume is delivered.
b. Minute volume will remain constant to provide stable blood gases. Airway pressure will increase or decrease with changes in the patient's
compliance and/or airway resistance.
c. Volume cycled ventilators can be used with most patients.
d. Most common approach for mechanicalventilation.
2. Pressure Cycled.
a. These ventilators are normally pneumatically powered (50 PSI) and apply positive pressure to the airways until a preset pressure limit is
reached.
b. Tidal volume (Vr) is adjusted by increasing or decreasing the pressure limit.
c. Although peak pressure will remain constant, the volume will change as lung compliance and/or airway resistance change.
d. This type of ventilator is best for intermittent therapy (IPPB) or continuous ventilation for patients with normal lungs (Post-Op, Neuro,etc.).
e. Examples: Bird Mark 7.
Bennett PR-2.
3. Time Cycled.
a. These ventilators apply positive pressure until a preset time is reached.
b. The peak inspiratory pressure (PlP) is usually limited by an adjustable pop-off valve.
c. TidalVolume (V1) is adjusted by increasing or decreasing the peak inspiratory pressure, inspiratory time, or flow.
d. Commonly used for infant ventilation.
D. Fluidic Ventilators
1. Pressure-limited ventilators.
2. Often used during the inspiratory cycle and expiratory phase on pressure-limited ventilators; enabling the ventilator to switch back and forth
between inspiration and exhalation.
E. Home Ventilators
1. Many negative pressure and positive pressure ventilators can be used in the home setting.
2. A backup ventilator should be provided for any patient who requires ventilation the majority of the time.
3. Non-invasive ventilators and CPAP devices are often utilized in the home setting.
F.Transport Ventilators
1. Should be portable and lightweight.
2. Duration of flow must be considered when using air and oxygen cylinders to power the ventilator.
3. lf respiratory rate or tidal volume decreases on pneumatic transport ventilator - check the cylinder pressure.
4. Many different models are available for use; should be able to meet the patient's demands.
G.Microprocessor Ventilators
1. Used with volume-cycled flow-limited ventilation or pressure-limited time-cycled (pressure control) ventilation.
2. Ventilator rate, mean airway pressure (Paw), peak and plateau pressures, volumes, compliance, etc. can all be easily monitored.
3. Can provide pressure control ventilation (PCV) and pressure support ventilation (PSV).
H.Ventilator Circuit
1. Typical ventilator circuit includes:
a. Inspiratory limb.
b. Expiratory limb.
c. Wye adaptor.
d. Nebulizer.
e. Humidifier.
I.Changing Ventilator Circuits
1. Ventilator circuits should not be changed on a regular basis unless:
a. Circuit is grossly contaminated.
b. Malfunctioning.
2. The patient should be off the ventilator for the shortest possible amount of time.
3. Manual ventilation with a resuscitation bag will be necessary while the new circuit is attached and tested by another person.
4. Pre and post oxygenate with 100% 02 to prevent iatrogenic hypoxemia.
J. Ventilator Alarms
1. Common Alarms.
a. High pressure limit (set 10 cmH2O above peak airway pressure).
b. Minimum exhaled volume (set 100 mL below exhaled tidal volume).
c. Low pressure limit (set 10 cmH2O below peak airway pressure).
d. Oxygen alarm (set 5% above and below set FrOz).
e. PEEP/CPAP (high and low level).
f. Failure to cycle (check power supply).
g. Loss of power (check power supply).
h. Oxygen failure (check oxygen source).
i. Temperature alarm (set low and high level).
2. Troubleshooting: alwavs provide manual ventilation first.
a. Low pressure alarm - consider:
1. Patient disconnect.
2. Leak in the ventilator circuit.
3. Insufficient flow.
4. Endotracheal/tracheostomy tube cuff leak.
b. High pressure alarm - consider:
1. Patient obstruction (endotracheal tube, pneumothorax, t Raw, secretions, etc).
2. Equipment obstruction (ventilator circuit).
c. Low exhaled volume alarm - consider:
1. Patient disconnect (ventilator circuit).
2. Low spontaneous tidal volume.
d. Temperature alarm.
1. High temperature alarm - check humidifier temperature.
2. Low temperature - check humidifier temperature, may decrease during aerosol therapy.
3. Example:
Question: A patient who is being mechanically ventilated has received an aerosol treatment inline with the ventilator circuit.
Following the treatment, the high temperature alarm is sounding. Why would this occur and how should the respiratory
therapist correct the problem?
Answer: The high temperature alarm sounded because the flow of the aerosol caused the temperature probe to cool down.
The humidifier responded by increasing its temperature. Once the treatment is completed the cooling stops, so the air
temperature rises. To correct the problem, adjust the temperature setting on the humidifier.
K.Time Cycled Pressure-Limited Ventilators
1. General Principles.
a. Continuous flow provided between breaths for spontaneous breathing (lMV).
b. Inspiration begins and ends according to preset inspiratory time.
c. Maintains preset pressure limit using pressure popoff.
d. Volume delivered demands close monitoring because it varies with EVERYTHING.
1) Pressure Limit.
2) Flowrate.
3) Inspiratory Time.
4) Compliance (Lung and machine tubing).
5) Airway Resistance (Patient and machine tubing).
6) Patient effort during spontaneous breathing.
7) CPAP or PEEP changes.
2. lnitial Settings for Infants.
a. Mode :IMV.
b. Peak Inspiratory Pressure (PlP) :20 - 30 cmH2O.
c. Respiratory Rate :20 - 30 breaths/min.
d. Inspiratory time (lT) :0.5 - 0.6 seconds.
e. Flow :5 - 6 L/min.
f. Fro2 :40 - 60 % or Set at same level prior to ventilation.
g. PEEP :+2 - +4 cmH2O.