Introduction to Mechanical Ventilation at UT Southwestern

Jonathan C. Weissler M.D.

Chief of Medicine, UT Southwestern University Hospitals

Professor and Vice Chairman, Department of Internal Medicine

University of Texas Southwestern Medical Center

Ventilators in UTSW SystemParkland: Servo-1 (Maquet)

Ventilators in UTSW System

CUH, VA : Puritan Bennett 840

Modes of Ventilation

Volume ControlThe machine guarantees a minimum tidal volume with each delivered breath regardless of the pressure necessary to deliver it (as long as limits are not exceeded)

Pressure ControlThe machine delivers a set pressure with each breath, tidal volumes vary and are not guaranteed.

Modes of ventilation

Mode of ventilation:

Volume Control Assist Control (CMV) –every breath full support

SIMV- mandated breaths plus unsupported extra breaths– NOT APPROPRIATE IN MOST MICU PATIENTS

Setting Up the Ventilator

1. FiO2

2. Tidal Volume

3. Rate

4. I:E ratio

5. PEEP

6. Alarms

7. Sedation/Paralysis

FiO2

1.0 (100%) in most cases

EXCEPT

History of Bleomycin, Amiodarone (risk of oxidant mediated lung injury)

Tidal Volume

General Principles:Normal lungs (neuromuscular disease only, head trauma): 10cc/kg PBW (~700 cc)

ARDS/ALI, bad pneumonia: 6-7 cc/kg PBW (~375-425 for men, 300-325 for women)

Asthma/COPD: 375-425 cc

Compliance Curve

Compliance Curve in ARDS(Am J Resp Crit Care Med 1995,152:121-8)

Percent of ARDS Patients Exceeding the UIP with Increasing VT

(Am J Resp Crit Care Med 1995,152:121-8)

Tidal Volume

General Principles:Normal lungs (neuromuscular disease only, head trauma): 10cc/kg PBW (~700 cc)

ARDS/ALI, bad pneumonia: 6-7 cc/kg PBW (~375-425 for men, 300-325 for women)

Asthma/COPD: 375-425 cc

Low Tidal Volumes Improve Survival in ARDS

(NEJM 2000, 342:1301-8)

How to Ventilate ARDS How to Ventilate ARDS

Brower RG, et al. Am J Respir Crit Care Med 2002:166;1515-1517

Tidal Volume

General Principles:Normal lungs (neuromuscular disease only, head trauma): 10cc/kg PBW (~700 cc)

ARDS/ALI, bad pneumonia: 6-7 cc/kg PBW (~375-425 for men, 300-325 for women)

Asthma/COPD: 375-425 cc

Assist Control2. Rate normal lungs 10-12 ARDS/pneumonia 24-28 asthma/COPD 7-8 UNLESS pCO2 >90

I:E ratio Normal 1:3 ARDS 1:2 Asthma 1:6

Inspiratory time**** Flow rate 50-100 L/min, usually 50-60 L/min

Flow rate vs. no flow rate

Air Trapping Detected by Flow vs Time Curve

Pay Attention to the Interaction Between Tinsp, Rate, and I:E

Relationship of Mortality to Oxygenation in 101 Studies of ARDS

(Intensive Care Med 1996, 22:519-29)

Relationship between FiO2 and pO2

Oxygenation

Palv (mean) ~= Ti/Te + PEEP +

auto PEEP

PEEPNormal Lungs : 0-5 cm

ARDS: unclear, probably 8-10

Unless patient can’t be oxygenated; then 15-18

asthma/COPD : 0*

* until COPD patient is awake and triggering ventilator

elevated CNS pressure :0**

** unless necessary for oxygenation

Peak Pressure Alarm

1. Peak pressure- when alarm sounds breath is terminated.

2. Causes may be mucus plug, kinked tube, pneumothorax, worsening compliance, or patient “fighting the ventilator”.

3. Usually set at 50-60 mmHg; in a tight asthmatic set at >80.

OK thanks for the reassurance that oxygenation doesn’t correlate with survival BUT I Can’t

Oxygenate the Patient (sats <85% and dropping)

Call somebody and get a CXR

Bag the patient with a PEEP valve (10cm or greater) attached

PEEP to increase mean pressure

Pressure control/APRV/Bilevel ventilation

Nitric Oxide

Prone ventilation

Oscillator/high frequency ventilator

ECMO

ECMO 2015V-V ECMO removes CO2, can only send 3-5 L/min thru the membrane so oxygenates better with lower cardiac outputs, avoids some of the embolic complications of V-A ECMO. Allows patients to ambulate pre-transplant.CESAR trial in UK 2001-6: referral to single ECMO center. Survival for those referred at 6 months 63% v 47% at tertiary care centers. Patients started on ECMO at mean 35 hours ventilation (Int Care Med 2009)

ANZ ECMO (JAMA 2009) Salvage therapies (iNO, HFOV) used in less than 30%, median days on vent ECMO 18 v 8 conventional, ICU days higher on ECMO (22 v 12), ICU mortality higher (23% v 9%). Most patients started on ECMO elsewhere then transferred to an ECMO center

What to Follow in a Ventilated Patient

1. ABG- In a sick patient “the enemy of good is better”

2. pCO2- A significant rise with a constant or increased minute ventilation is ALWAYS a bad sign

3. Plateau pressure- Keep it under 33-34, in ARDS change to pressure limited ventilation

4. Air trapping

5. Patient comfort (synchrony)

Rapid Sequence Intubation

1. If patient has spinal cord injury or recent neck surgery, or you anticipate a difficult airway you need anesthesiology

2. Preoxygenate without bagging unless patient hypoxic (sats<91%), if critically unstable bag and tube

3. Versed 2-4 mg IV over 30-60 seconds, Etomidate 20mg over 30-60 seconds, Succinylcholine 1mg/kg IV over 30-60 seconds

Don’t use succ in patients with ALS,

Polio, or hyperkalemic

SedationSedation

Usually a combination of an Usually a combination of an anxiolytic and an analgesicanxiolytic and an analgesic

Parkland ICU: Morphine (or Parkland ICU: Morphine (or Fentanyl) and AtivanFentanyl) and Ativan

VA ICU/UHSP: Fentanyl and VersedVA ICU/UHSP: Fentanyl and Versed

Alternative: Propofol (Diprivan)Alternative: Propofol (Diprivan)

SedationSedation

Important principlesImportant principles:: Always start with a loading dose followed Always start with a loading dose followed

a low-dose continuous infusion.a low-dose continuous infusion. Any up titration of the continuous Any up titration of the continuous

infusion should be preceded by an infusion should be preceded by an additional loading doseadditional loading dose

Avoid writing: “Morphine and Ativan Avoid writing: “Morphine and Ativan drips—titrate to sedation”drips—titrate to sedation”

Sedation holidaysSedation holidays

SedationSedation

MorphineMorphine Loading dose: 2-5mg IV bolusLoading dose: 2-5mg IV bolus Initial infusion: 2-4 mg/hrInitial infusion: 2-4 mg/hr Titration:Titration:

Reload with 2-5mg IV bolusReload with 2-5mg IV bolus Increase infusion by 1-2mg/hrIncrease infusion by 1-2mg/hr May repeat every 15-30 minutes as neededMay repeat every 15-30 minutes as needed

Maximum: 20mg/hrMaximum: 20mg/hr

SedationSedation

AtivanAtivan Loading dose: 2-4mg IV bolusLoading dose: 2-4mg IV bolus Initial infusion: 1-2 mg/hrInitial infusion: 1-2 mg/hr Titration:Titration:

Reload with 2-4mg IV bolusReload with 2-4mg IV bolus Increase infusion by 1-2mg/hrIncrease infusion by 1-2mg/hr May repeat every 15-30 minutes as neededMay repeat every 15-30 minutes as needed

Maximum: 10mg/hrMaximum: 10mg/hr

SedationSedation

FentanylFentanyl Loading dose: 25-50 mcg IV bolusLoading dose: 25-50 mcg IV bolus Initial infusion: 25-50 mcg/hrInitial infusion: 25-50 mcg/hr Titration:Titration:

Reload with 25 mcg IV bolusReload with 25 mcg IV bolus Increase infusion by 25 mcg/hrIncrease infusion by 25 mcg/hr May repeat every 15-30 minutes as neededMay repeat every 15-30 minutes as needed

Maximum: 150-200mcg/hrMaximum: 150-200mcg/hr

SedationSedation

VersedVersed Loading dose: 2-5mg IV bolusLoading dose: 2-5mg IV bolus Initial infusion: 2-4 mg/hrInitial infusion: 2-4 mg/hr Titration:Titration:

Reload with 2-5mg IV bolusReload with 2-5mg IV bolus Increase infusion by 1-2mg/hrIncrease infusion by 1-2mg/hr May repeat every 15-30 minutes as neededMay repeat every 15-30 minutes as needed

Maximum: 20mg/hrMaximum: 20mg/hr

SedationSedation

Propofol (Diprivan)Propofol (Diprivan) Rapid onset/short duration of actionRapid onset/short duration of action Rapid Induction: Rapid Induction:

20-40mg IV bolus Q 20 seconds until sedated20-40mg IV bolus Q 20 seconds until sedated Continuous infusion: Continuous infusion:

Start 5-10 mcg/kg/minStart 5-10 mcg/kg/min Increase by 5-10 mcg/kg/min every 5-10 minutes Increase by 5-10 mcg/kg/min every 5-10 minutes

until desired sedation (Max 100mcg/kg/min)until desired sedation (Max 100mcg/kg/min) Adverse ReactionAdverse Reaction: : HypotensionHypotension, ,

bradycardiabradycardia

ParalyticsParalytics

Bolus dosing:Bolus dosing: Vecuronium Vecuronium (Norcuron) 0.08-0.1 mg/kg (Norcuron) 0.08-0.1 mg/kg

IV x 1IV x 1 Usual dose Usual dose 7-10mg IV bolus7-10mg IV bolus Short onset/Intermediate durationShort onset/Intermediate duration Used for one time/short-term paralysis or Used for one time/short-term paralysis or

repeated boluses as needed for longer repeated boluses as needed for longer duration of paralysisduration of paralysis

Caution in liver and neuromuscular Caution in liver and neuromuscular diseasedisease

ParalyticsParalytics

Continuous infusion:Continuous infusion: Cisatracurium (Cisatracurium (NimbexNimbex))

Loading dose: 0.1-0.2mg/kg IV bolusLoading dose: 0.1-0.2mg/kg IV bolus Maintenance dose: 2.5-3 mcg/kg/min Maintenance dose: 2.5-3 mcg/kg/min

continuous infusioncontinuous infusion Titrate infusion to 2/4 on “Train of Four” Titrate infusion to 2/4 on “Train of Four”

(TOF)(TOF) Intermediate onset/intermediate Intermediate onset/intermediate

durationduration Safe to use renal and liver failureSafe to use renal and liver failure