Mechanical Ventilation Flashcards
What is it?
- A machine that generates a controlled flow of gas into a patient’s airway!
- O2 and air are generated from cylinders or wall outlets
- The gas is blended according to prescribed “inspired oxygen tension” - FiO2
- It accumulated in a receptacle in the machine
- Then delivered to the patient using one of many available modes
Indications for Ventilation
- Ventilatory failure
- Inability to protect the airway
- Failure to clear the airway
Airway Accesses
- Non-invasive ventilation
- Nasal cannula
- Face mask
- Non-rebreather mask
- BiPAP
- Laryngeal Mask Airway (LMA)
- Endotracheal tube
- Tracheostomy (for prolonged intubation)
Types of Ventilators
- Negative-Pressure Ventilators
- Positive-Pressure Ventilators
- Non-invasive Ventilation
Negative-Pressure Ventilation
- Creates negative pressure externally to draw the chest outward and air into the lungs
- Mimics spontaneous breathing
- Used for individuals with neuromuscular disorders
Positive-Pressure Ventilation
- PUSHES air into the lungs
- Can be invasive and non-invasive
- Amount of air delivered in:
- Volume (milliliters)
- Specific pressure
•Used for individuals with Acute Respiratory Failure
Positive-Pressure Ventilators:
Noninvasive Ventilation (BIPAP)
- Provides ventilator support, but uses a tight fitting mask
- Used to AVOID intubation
- Supportive for patients with:
- Sleep Apnea•Impending respiratory failure
- Success varies and is limited to patient tolerance
Positive-Pressure Ventilators
•Normal respiratory properties will be reflected in your mechanical ventilation settings
- MODE (Spontaneous vs. Mechanical)
- DEPTH (Tidal Volume)
- OXYGEN (FiO2)
- RATE
Modes of Positive-Pressure Ventilation
•Controlled Mechanical Ventilation (CMV)
•Breaths are delivered regularly and independent of the patient’s own ventilatory efforts
- Used when the patient has NO DRIVE TO BREATHE!
- Under anesthesia
- Chemically paralyzed
•Very rarely used
Modes of Positive-Pressure Ventilation
•ASSIST-CONTROLLED MECHANICAL VENTILATION (ACV)
•Vent breath is triggered by patient inspiration
- Used:
- To initiate mechanical ventilation
- Those at risk for respiratory arrest
- If the patient does not initiate a breath in a pre-set time the vent fires a breath at the pre-set Vt
•Allows the patient to breath faster, but not slower
Modes of Positive-Pressure Ventilation
•SYNCHRONOUS INTERMITTENT MANDATORY VENTILATION (SIMV)
- Allows the patient to breath spontaneously without vent assistance between delivered vent breaths
- Vent has a pre-set rate and tidal volume and will not fire when the patient produces their own breath
- COORDINATED with the patient’s own respiratory effort
Modes of Positive-Pressure Ventilation
•SIMV commonly used to:
- Support ventilation
- Exercise the respiratory muscles between vent-assisted breaths
- During the weaning process
SIMV Setting
- Vent is set on:
- “SIMV of 4 and pt’s RR is 18”
- How many spontaneous breaths is your patient taking?
- 4
- 18
- 14
- 22
Tidal Volume (VT)
•The volume of air delivered during each ventilator-augmented breath
- Normal Adult VT is:
- 6-10 mL/kg or approx. 400-500 mL
- ↑ VT → ↑ risk of barotrauma & ↓ venous return / CO
- ↓ VT → ↑risk of atelectasis
Oxygen
- 3%pf the body’s oxygen is dissolved in the plasma
- PaO2 – partial pressure of oxygen (mmHg)
- Measures how much oxygen is available in the alveoli
- SaO2 (oxygen saturation) measures the degree of oxygen bound to hemoglobin
Oxygen (FiO2)
- Set at the lowest possible level for adequate tissue perfusion
- FiO2 can be 21% - 100% oxygen
- Try to keep FiO2 < 50% to avoid oxygen toxicity or fibrosis
- Often have set parameters to keep:
- SpO2> 90% and PaO2 > 60 mm Hg
Hypoxemia
- Results from ventilation or circulatory problems
- VQ Mismatching (shunting)
PROBLEM VENTILATION CIRCULATION (PERFUSION)
MECHANISM Too little oxygen reaches the alveoli Too little blood reaches the alveoli
EXAMPLE Pneumonia Atelectasis Bronchospasm Pulm. Emboli Heart failure
Rate of Ventilations
- Normal RR is 12 – 20
- Initially set at approx. 12 – 15 vent. Breaths/min.
- ETCO2 (capnography) or the PaCo2 may be used to determine the rate
- PaCO2 < 38 mmHg indicates –
- ETCO2 > 45
•What does this tell us?
Special Ventilator Settings
•Positive End-Expiratory Pressure (PEEP)
- Used to maintain positive pressure in the lungs at the end of expiration
- Improves the VQ relationship and diffusion across the alveolar-capillary membrane
- Prevents:
- Atelectasis
- Reduces Hypoxemia
- Allows for a lower % of FiO2
Special Ventilator Settings
•Pressure Support Ventilation (PSV)
- Preset pressure delivery augmenting patient own respiratory effort
- Applies positive pressure during “spontaneous” inspiration
- Can be used with all modes of ventilation
- Used to:
- Overcome dead space of circuit & pt’s airways
- Decreases the work of breathing
Special Ventilator Settings
•Continuous Positive Airway Pressure (CPAP)
- Elevates end-expiratory pressure during spontaneous breaths
- Used for intubated and non-intubated patients
- Used to:
- Maintain open airways
- Decrease the work of breathing
CPAP Mask or BiPAP
- Used to improve oxygenation on patient’s who can breath on their own
- Used for those experiencing sleep apnea at night
- Masks must be very tight on the face!
SO…WHATS ALL THE NOISE ABOUT?
High Pressure Limit
- Secretions or Condensation in tubing
- Kink in vent tubing
- Biting ETT
- Coughing or gagging
- Bronchospasm or Pneumothorax
Low Pressure
- Vent tubing disconnect
- Displaced OETT or Trach tube
High Respiratory Rate
- Anxiety or pain
- Secretions
- Hypoxia
- Hypercapnea
Low Exhaled Volume
- Vent tubing disconnect
- Cuff leak or inadequate cuff seal
- Another occurring alarm preventing breath delivery
Complications of Mechanical Ventilation
- Improper Tube Placement
- Inflated lung vs. Uninflated lung
- Gastric Distention
- Aspiration
- Facial Skin Necrosis
- Crepitus
- Drying of eyes & mucous membranes
- Stress
- Claustrophobia
- Hospital Acquired Pneumonia
- Normal respiratory defense mechanisms bypassed
- Open epiglottis
- Cough/Gag reflexes inhibited or impaired
- Secretions often thick & tenacious
- Increases the risk of atelectasis
•What is vital in preventing this?
Complications of Mechanical Ventilation
- Aspiration
- Oxygen toxicity
- Resp. acidosis/alkalosis
- Failure to wean
- ↓ BP & CO
- Poss. Liver & renal dysfunction
- ↑ Intracranial pressure
- Fistulas
- Barotrauma
- Fluid retention
- Loss of muscular conditioning
- Malnutrition
Ventilator Weaning
•The process of removing ventilator support and re-establishing spontaneous, independent breathing
•Process depends on: •Preexisting lung conditions •Duration of mechanical ventilation •Patient’s general condition –physically and psychologically
Ventilator Weaning
•Both SIMV and PSV are used for weaning
- When duration of mechanical ventilation has been longer and respiratory muscle reconditioning is needed.
- Duration of periods off the vent is gradually increased until patient can maintain adequate independent respirations for several hours
- Using SIMV to wean:
- Number of vent assisted breaths are gradually decreased
- When pt is able to tolerate an SIMV of 4 bpm → a T-piece or CPAP weaning is attempted
- Using PSV to wean:
- Pressure support levels are gradually decreased
- When PSV is just enough to overcome ETT resistance → support is DC’d →Pt. is extubated
Ventilator Weaning
•Terminal Wean
•Gradual withdrawal of mechanical ventilation when survival without assisted ventilation is NOT expected
- Nursing Considerations:
- Need to discuss option with pt /family / SO
- When? Where? What?
- Provide education and comfort
