mechanical ventilation

ventilation

The act of breathing and/or moving air

what does a ventilator do?

pushes air into the lungs to quite literally ventilate them

respiration

• Gas exchange for oxygenation

• The actual movement of gas across a membrane

can a ventilator help with respiration?

no

The inability to maintain adequate _____________ to maintain normal _______________, _____________, or a combination of both

ventilation; oxygenation; CO2 elimination; respiratory failure

potential causes of respiratory failure

• Trauma

  • MVC, GSW, C-spine injury, TBI

• Post-surgical

• COPD

• Neuromuscular disease

• Organ system failure

  • Heart, kidneys

• Post-cardiac arrest

• Stroke

Indications for Mechanical Ventilation

• Gas exchange at alveoli is impaired due to inadequate ventilation

• CO2 in the blood goes up, O2 goes down

• Alveolar hypoventilation (too little)

• Disruption to O2 and CO2 levels in the blood

How respiratory failure is measured/detected key terms

• PAO2 and PACO2

• Arterial blood gas (ABG)

• Hemoglobin

• Acidosis

• Alkalosis

• Hypoxemia

• Hypoxia

• Hypercapnia

PAO2 and PACO2

• Partial pressure of O2 and CO2 dissolved in arterial blood

• Refers to the force necessary to move O2 from air to blood, then blood to body tissues

Arterial blood gas (ABG)

• Blood sample from an artery to indicate acid-base or pH status of the blood

• One factor used to determine need for mechanical ventilation

pH of blood should be between ______ and ______

7.35 and 7.45

Hemoglobin

• Protein by which oxygen is transported

• Also reflected in an ABG

Acidosis

Respiratory or metabolic- decrease in pH of the blood due to hypoventilation

Alkalosis

Respiratory or metabolic- increase in pH due to hyperventilation

Hypoxemia

Lack of oxygen in arterial blood

Hypoxia

Lack of oxygen in blood tissue

Hypercapnia

• Alveolar hypoventilation

• The result of too much CO2

In your own words, define respiratory failure

when the lungs can’t ventilate so your body can get oxygen or your body can’t get rid of CO2, or a combination

One determining factor for the need to initiate mechanical ventilation comes from a blood test called what?

arterial blood gas (ABG)

Alkalosis and acidosis are the result of variation in what acid-base measure?

pH level in the blood

The medical term for too much CO2 in the blood is called what?

hypercapnia

mechanical ventilation takes over some or all the work of _________

spontaneous breathing

mechanical ventilation is required when a patient is in or moving towards _________

respiratory failure

mechanical ventilation can help recruit collapsed _____________, keep them open, and increase efficiency of gas exchange

alveolli

Mechanical Ventilation Care Team

• respiratory therapist (RT)

• RN nurse

• MD or physician

• SLPs

Technical operation of the vent per MD orders

respiratory therapist (RT)

Daily care, cleaning, monitoring

RN nurse

MD or physician

• Pulmonologist or Critical Care MD

• Decides the vent mode and settings

SLPs are involved during ______ for ______

Must be familiar with ___

weaning process for communication and swallow

vent

ventilator components

1. The patient is supplied air from the ventilator through a piece of flexible tubing from the ventilator's inspiratory port.

2. Inspiratory gas exits the ventilator and passes through a heated humidifier mounted on the side or through a heat and moisture exchanger placed at the airway connection.

3. After this, the inspired gas is delivered to the interface and into the patient's airway.

4. Exhaled gas from the patient travels back to the ventilator through another flexible tube and goes through a high-efficiency particulate absorbing (HEPA) filter before the gas enters the ventilator.

5. This filter protects the ventilator from internal contamination and the environment from possible infectious agents.

Ventilator Controls- 2 Primary Types

1. volume controlled ventilation

2. pressure controlled ventilation

volume controlled ventilation

• Provides pre-set volume delivered by ventilator

• The pressure provided to pt will be delivered until preset volume of air is reached

• amount of air delivered to lungs (tidal volume, ex: 500mL)

The pressure provided to pt will be delivered until preset volume of air is reached

volume controlled ventilation

amount of air delivered to lungs

volume controlled ventilation (tidal volume, ex: 500mL)

pressure controlled ventilation

• Provides pre-set pressure (inspiratory airflow) delivered by ventilator

• Amount of pressure required is based on pt’s lung compliance

• The volume provided will vary from breath to breath

• Force of air delivered to lungs (ex: fan setting, low/med/high)

Higher the pressure, the sicker the lungs

Amount of pressure required is based on pt’s lung compliance

pressure controlled ventilation

Force of air delivered to lungs

pressure controlled ventilation (ex: fan setting, low/med/high)

what is critical to ensure oxygen delivery?

Maintenance of pressure in the lungs

Think back to residual volume, discussed in previous lectures

if we exhale completly- there would be lung collapse

How is pressure maintained?

Positive End Expiratory Pressure (PEEP

Positive End Expiratory Pressure (PEEP)

• Setting that can be added to any of the modes of ventilation

• Allows patient to exhale passively, but stops complete exhalation, resulting in positive baseline pressure

baseline pressure of adults

5 cm of pressure (PEEP is set here)

some may be higher to be stented to keep them from collapsing

Tidal Volume (TV)

Volume of air inhaled and exhaled during normal quiet breathing

Residual Volume (RV)

Volume of air that remains in the lungs beyond a maximum forced expiration

What are the 2 main types of controls for mechanical ventilation?

1. volume 

2. pressure

In your own words, state what PEEP is abbreviated for and what it means

Positive End Expiratory Pressure

for stenting the airway so no collapse of airway and expiring all the volume of the lungs

Ventilator Modes(i.e. mandatory vs. spontaneous breaths)

controlled- highest level of support (sedated) cannot trial PVM

intermittent- less support, can trial PVM

controlled ventilator modes (most to least support)

1. Controlled-Mode Ventilation (CMV)

2. Assist Control (AC)

3. Assist Mode (A)

Provides complete control over the rate and volume of each breath provided

Controlled-Mode Ventilation (CMV)

Only used for sedated patients or those with inability to trigger the vent with own breaths

Controlled-Mode Ventilation (CMV)

Assist Control (AC)

• Provides preset volume or pressure every time pt initiates a breath

• Provides backup if pt does not initiate inspiration

• does need to be alert at some degree

Assist Mode (A)

• Inspiration initiated by pt to trigger vent support

• No backup vent rate set

intermittent ventilator modes (most to least support)

1. Intermittent Mandatory Ventilation (IMV)

2. Synchronized Intermittent Mandatory Ventilation (SIMV)

Intermittent Mandatory Ventilation (IMV)

• Permits pt to breathe spontaneously at own rate and volume in between preset positive pressure breaths

• Pt still receives some volume from ventilator

• Pt takes on more work of breathing

Synchronized Intermittent Mandatory Ventilation (SIMV)

• Synchronizes with pt through coordination of mandatory breaths and pt’s inspiratory efforts

• If pt does not breathe, vent delivers breath to the patient

• If pt triggers the breath, vent support is not provided (support as needed)

• Commonly used during vent weaning

what are the 2 main ventilator modes?

1. controlled - highest level of support

2. intermittent- certain support but more spontaneously, as needed= (SIMV)

What is the main difference between the two ventilator modes?

can trial PMV with intermittent (SIMV) most likely

Both the ____________ and __________ are monitored closely for ventilator

ventilator and patient

Care for a patient on the vent involves collaboration between multiple disciplines

• Frequent care by nursing (likely in ICU setting)

• Respiratory care (suctioning and treatments) by RT

Ventilator Monitoring Parameters

• mode of ventilation

• tidal volume

• respiratory rate

• inspiratory and expiratory ratio

• inspiratory flow rate

• FiO2

• PEEP

• sensitivity

• Peak inspiratory pressure (PIP)

mode of ventilation

Type of support being delivered by the ventilator (operating characteristics)

Amount of air per breath delivered by ventilator (in ml or L)

tidal volume

Exhaled tidal volume: air returned to ventilator ensures delivery of

proper volume

respiratory rate

Number of breath cycles delivered per minute (normal individuals = 12)

respiratory rate can be titrated down during

vent weaning (i.e., # mandatory breaths)

volume of air provided over 1 minute

minute volume

inspiratory and expiratory ratio

Time relationship between inspiratory phase and expiratory phase

General rule: Expiratory phase is __ times the length of ________

2; inspiratory phase (1:2 ratio)

Expiration may need to be longer to minimize risk for _____

air trapping

inspiratory flow rate

Amount of gas in flow (in liters) provided to patient on inspiration

Amount of oxygen provided to the patient, expressed as a percentage

Pt may require supplemental O2 when there is poor oxygenation

FiO2

Oxygen concentration of room air is

21%

FiO2 stands for

fraction of inspired oxygen

what happens if FiO2 is too high?

O2 is too high, oxygen toxicity, not enough Nitrate

Maintenance of positive pressure in lungs at the end of expiration

PEEP

sensitivity

Regulation of how much effort is needed by the patient to cycle ventilator

Higher sensitivity requires more patient effort to …

trigger assisted breath

Peak inspiratory pressure (PIP)

Ventilator preset to limit the amount of pressure created in airway during inspiration to limit barotrauma (i.e, alveolar ruptures due to increased pressures)

Mean airway pressure

Average amount of pressure in the lungs