Indications for mechanical ventilation
MECHANICAL VENTILATION - cont'd info
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
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