MECHANICAL VENTILATION - cont'd info

Indications for mechanical ventilation

Indications for mechanical ventilation

Protect the airway

Ventilatory failure

– Respiratory acidosis with pH < 7.25

– PaCO2 ≥ 50

– Respiratory rate > 35 or < 10

– Increased work of breathing, diaphoresis, agitation, confusion

Impending respiratory failure

Cardiopulmonary arrest

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The various modes of mechanical ventilation

  • Airway Pressure Release Ventilation (APRV)

VC = volume control

PC = pressure control

PRVC = pressure-regulated volume control

Complications of mechanical ventilation

  • Ventilator-associated pneumonia
  • Venous thromboembolism
  • Barotrauma (pneumothorax or pneumomediastinum)
  • Tracheomalacia
  • Hypotension
  • Gastric ulcers
  • Critical illness polyneuropathy/myopathy
  • Deconditoning
  • Delirium

Indications for mechanical ventilation

Assist control modes

– Volume control
– Pressure control
– Pressure regulated volume control

Intermittent Mandatory Ventilation (SIMV)

– SIMV VC
– SIMV PC
– SIMV PRVC

Support mode (Continuous Positive Airway Pressure=CPAP)

– Varying amounts of pressure support

How to choose the initial ventilator settings

Initial Ventilator Settings

Assist-Control mode of ventilation

Tidal Volume

– Typically 6-8 mL/kg PBW
– PBW (kg) = 45.5 + [2.3 x (height in inches-60)] (women)
= 50 + (2.3 x (height in inches-60)] (men)

FiO2: Typically 0.8 to 1.0

PEEP: caution with shock or increased ICP

Pressure support

Rate: typically 12-15

I:E – usually 1:2 or 1:3

Assist-Control mode of ventilation

Tidal Volume

– Typically 6-8 mL/kg PBW
– PBW (kg) = 45.5 + [2.3 x (height in inches-60)] (women)
= 50 + (2.3 x (height in inches-60)] (men)

FiO2: Typically 0.8 to 1.0

PEEP: caution with shock or increased ICP

Pressure support

Rate: typically 12-15

I:E – usually 1:2 or 1:3

How to adjust ventilator setting to improve oxygenation

  • Trial of Airway Pressure-release Ventilation (APRV) ventilator mode

 

How to adjust ventilator settings to change ventilation

Improving oxygenation (Pa02)

– Increase FiO2
– Increase PEEP
– Increase Inspiratory time (caution for auto-PEEP)
– Increasing minute ventilation

Improving ventilation (PaCO2) MV=(Vt)(RR)

– Increase rate
– Increase tidal volume

Ventilator troubleshooting

  • If plateau pressure (Pplat) >30 or airway pressures are high
    • Suction ETT to assure no mucous plugging
    • Increase sedation if there is patient-ventilator dyssynchrony (bucking the vent)
    • Administer albuterol nebulized treatment for bronchospasm
    • Increase sedation if patient is biting on the ETT
    • Assure no kinks in airway tubing
    • Make sure that there is no auto-PEEP
    • Assure that a pneumothorax has not occurred
    • Assure that endotracheal tube has not migrated forward into right mainstem bronchus – if so, withdraw the tube to appropriate level
    • Investigate for possible abdominal compartment syndrome
  • If patient is not receiving adequate tidal volumes
    • Suction ETT to assure no mucous plugging and to confirm that suction catheter can pass fully
    • Assure that patient does not have a cuff leak
    • Assure that ETT has not been pulled back above vocal cords
    • Assure that patient is not biting ETT or that ETT is not kinked
    • Assure that airway tubing is connected properly to ETT
    • Make sure that there is no auto-PEEP
    • Assure that a pneumothorax has not occurred
    • Investigate for possible abdominal compartment syndrome
  • If patient has desaturation
    • Suction ETT to assure no mucous plugging
    • Increase sedation if there is patient-ventilator dyssynchrony (bucking the vent)
    • Administer albuterol nebulized treatment for bronchospasm
    • Increase sedation if patient is biting on the ETT
    • Assure no kinks in airway tubing
    • Make sure that there is no auto-PEEP
    • Assure that a pneumothorax has not occurred
    • Assure that endotracheal tube has not migrated forward into right mainstem bronchus or pulled back above vocal cords
    • Investigate for possible abdominal compartment syndrome
    • Assure that patient does not have a cuff leak
    • Examine for possible ventilator-associated pneumonia
    • Examine for possible pulmonary embolus
    • Examine for possible pulmonary edema

 

Ventilator weaning

  • If the patient is in an Assist-Control (AC) Mode
    • Wean FiO2 to keep SpO2>90%
    • Once FiO2 is less than 50%, begin weaning PEEP by 2 every 6 hours as tolerated until PEEP 5
  • Transition to Continuous Positive Airway Pressure (CPAP)/Pressure Support (PS) ventilation
    • Adjust PS to keep tidal volume (Vt) >325 mL
    • Wean PS by 2 every 4-6 hours to PS 6-8 as tolerated

Criteria for extubation

 

Ventilator sedation and analgesia

RASS = Richmond Agitation Sedation Scale

Ventilator Sedation

Sedating Agents (impart anxiolysis and amnesia)

– Ativan 2 mg IV q1hr prn agitation or anxiety

Side effect: Propylene glycol intoxication if > 10 mg/hr

– Propofol drip 0.5 mg/kg bolus then 5-100 mcg/kg/min.

Side effects: hypertriglyceridemia, hypotension & bradycardia

Propofol infusion syndrome

– Dexmedetomidine: start 0.5 mcg/kg/hr gtt then titrate between
0.2-1.4 mcg/kg/hr

Side effects: hypotension and bradycardia

Titrate meds to RASS scale 0 to -2

Richmond Agitation Sedation Scale

+4 Combative Overtly combative or violent, immediate danger to staff
+3 Very agitated Pulls on or removes tubes or catheters or has
aggressive behavior toward staff
+2 Agitated Frequent nonpurposeful movement or patient
ventilator dyssynchrony
+1 Restless Anxious or apprehensive but movements not
aggressive or vigorous
0 Alert and calm
-1 Drowsy Not fully alert, but has sustained (more than 10 sec)
awakening, with eye contact/eye opening to voice
-2 Light sedation Briefly (less than 10 seconds) awakens with
eye contact to voice
-3 Moderate sedation Any movement (but no eye contact) to voice
-4 Deep sedation No response to voice, but any movement to
physical stimulation
-5 Unarousable No response to voice or physical stimulation

Ventilator Analgesia

Morphine sulfate 2-4 mg IV q1hr prn analgesia

– Side effects: hypotension, itching and sedation

Fentanyl 50-100 mcg IV then 50-400 mcg/hr prn

– Side effects: Less hypotension and itching

Ketamine 1 mg/kg IV load then gtt between
0.2-1 mg/kg/hr

– Side effects: Tachycardia, hypertension, increased ICP, increased IOP, emergence reactions

Dexmedetomidine: start 0.5 mcg/kg/hr gtt then
titrate between 0.2-1.4 mcg/kg/hr

– Side effects: hypotension and bradycardia

Titrate meds to pain level ≤ 3