Mechanical Ventilation: A Primer(How to save a life when I’m alone in the middle of the night)

Nick Mohr, MDAssistant Professor

Department of Emergency MedicineDivision of Critical Care, Department of Anesthesia

University of Iowa Carver College of Medicine

Objectives• To review basic mechanical ventilation theory and

terminology• To define an algorithmic approach to mechanical

ventilation in the emergency department• To explore algorithms for troubleshooting ventilation

and oxygenation problems• To discuss specific clinical scenarios requiring

specialized ventilation strategies

Conflicts of Interest• This speaker has no financial relationships to

disclose.

• Topics discussed in this lecture are a component of the University of Iowa Visiting Professor Program Conference Series.

• The content of this lecture was developed following an extensive literature search and contains up-to-date, evidence-based information.

Basic Mechanical Ventilation

Ventilation Mechanics: Inflection Points, Loops, SynchronyAdvanced Strategies: Triggering, PRVC/VC+Ventilation Adjuncts: Proning, Inhaled Vasodilators, HelioxRescue Modes: APRV, HFOV

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What is the goal of mechanical ventilation?

Definitions

Definitions

Modes of Ventilation• Assist-Control (A/C)

– Volume Control (VC)

– Pressure Control (PC)

– Pressure Regulated Volume Control (PRVC/VC+)

• Synchronized Intermittent Mandatory Ventilation (SIMV)

• Pressure Support Ventilation (PSV)

Definitions

Ventilator Terminology

• PEEP

pPEEP

t

Definitions

Ventilator Terminology

• PEEP• Tidal Volume• FiO2

• Respiratory Rate– Set vs. actual

• Peak Pressure• Plateau Pressure

p t

peakplateau

Definitions

Tidal Volume

Respiratory Rate

FiO2PEEP

“Lung Protection”

“Ventilation” “Oxygenation”

Definitions

Determann RM. et al. Crit Care 2010;14:R1

Algorithm

Mascia L. et al. JAMA 2010;304:2620-7.

Algorithm

Ventilation Algorithm

Courtesy Scott Weingart, MD

Algorithm

Successful Intubation

Lung Protection Strategy

Obstructive Lung Disease

1. Select ventilation strategy

Algorithm

Successful Intubation

Lung Protection Strategy

Obstructive Lung Disease

1. Select ventilation strategy

Algorithm

IBWmale (kg) = 50 + (2.3 x h(over 5 ft)(in))

IBWfemale (kg) = 45.5 + (2.3 x h(over 5 ft)(in))

2. Calculate ideal tidal volume

Goal volume 6 mL/kg

Algorithm

Image courtesy JustPressPlay®

Height Male Female5 ft 2 in 350 350

5 ft 5 in 400 400

5 ft 8 in 450 450

5 ft 11 in 500 500

6 ft 2 in 550 500

6 ft 5 in 600 550

6 ft 8 in 650 600

Algorithm

Algorithm

How well do we practice low tidal volume ventilation in the ED?

Fuller BM. et al. Acad Emerg Med 2013;20:659-69.

3. Select respiratory rate

Try to match required minute ventilation

Usually start at 14-18 breaths/minute

Check a blood gas

Algorithm

4. Select oxygenation parameters

Start all ventilated patients at FiO2 = 100%

Wean aggressively

Algorithm

Why add PEEP?

Algorithm

Volu

me

Pressure

Algorithm

Volu

me

Pressure

PEEP

Algorithm

Volu

me

Pressure

PEEP

Algorithm

Bendixen HH. et al. N Engl J Med 1963;269:961-6

AIRPulmonary artery

Pulmonary vein

SHUNT

Algorithm

Slutsky AS. et al. NEJM 2006;354:1839-41

Algorithm

Why add PEEP?• Decrease shunt• Prevent atelectasis• Increase mean airway

pressure

FiO2 PEEP

30% 5

40% 5

40% 8

50% 8

50% 10

60% 10

70% 10

70% 12

70% 14

80% 14

90% 14

90% 16

90% 18

100% 18-24

Brower RG. et al. N Engl J Med 2000;342:1301-8

Algorithm

peakplateau

P

P

alveoli

ventilator

5. Limit plateau pressure

Algorithm

6. Check blood gas, reassess

Check ABG/VBG at 15-30 minutes

Correlate with EtCO2

Algorithm

Volu

me

Pressure

Plateau Pressure ≤ 30 cm H20

Tidal volume 6 – 8 mL/kg

PEEP set to limit atelectasis and shunt

(PEEP table)

Minimize FiO2

Lung Protective Ventilation

Algorithm

Goal-Directed Ventilation

MAP ≥ 65 pH ≥ 7.15

FiO2 ≤ 60%VT < 8 mL/kgpplateau < 30 pO2 ≥ 60

ComfortSedation

Pain Control

Algorithm

Lung Protective Ventilation1. Start with A/C (VC), sedation/pain control

2. Set tidal volume (6 – 8 mL/kg IBW)

3. Adjust respiratory rate for ventilation

4. Set FiO2 at 100% and wean aggressively

– Titrate PEEP to necessary FiO2 (table)

5. Check plateau pressure (goal < 30)

6. Check blood gas and titrate

Algorithm

How does ventilation differ in patients with obstructive lung

disease?

Algorithm

P

Flow

Flow does not return to zero

Peak pressure rises

“Air trapping”

Algorithm

Normal lungsObstructive Lung Disease

Algorithm

Marini. et al. Critical Care Medicine: The Essentials, 1997

Normal Abnormal

Flow

“Rest” “No Silence”

Algorithm

Tidal Volume

Respiratory Rate

FiO2PEEP

“Lung Protection”

“Ventilation” “Oxygenation”

Protection

Algorithm

Successful Intubation

Lung Protection Strategy

Obstructive Lung Disease

1. Select ventilation strategy

Algorithm

IBWmale (kg) = 50 + (2.3 x h(over 5 ft)(in))

IBWfemale (kg) = 45.5 + (2.3 x h(over 5 ft)(in))

2. Calculate ideal tidal volume

Goal volume 8 mL/kg

Algorithm

3. Select respiratory rate

Try to meet ventilatory demands

Start at 8 breaths per minute

Reassess at bedside – look at flow loop

THIS IS THE MOST EFFECTIVE WAY TO KILL A SEVERE ASTHMATIC WITH THE VENTILATOR

Algorithm

4. Select oxygenation parameters

Start all ventilated patients at FiO2 = 100%

Wean aggressively

These patients probably will not require high FiO2 levels

Algorithm

5. Set PEEP

Start low (PEEP 0 okay)

Keep it low

Algorithm

peakplateau

P

P

alveoli

ventilator

6. Limit plateau pressure

Recheck frequently

Algorithm

7. Check blood gas, reassess

Check ABG/VBG at 15-30 minutes

Correlate with EtCO2

pH ≥ 7.10 – 7.15 is good enough in most circumstances

Algorithm

Goal-Directed Ventilation

MAP ≥ 65 pH ≥ 7.15

FiO2 ≤ 60%VT < 8 mL/kgpplateau < 30 pO2 ≥ 60

ComfortSedation

Pain Control

Algorithm

Obstructive Lung Disease Ventilation

1. Start with A/C (VC), sedation/pain control (deep)

2. Set tidal volume (8 mL/kg IBW), higher for ventilation

3. Keep respiratory rate low

4. Set FiO2 at 100% and wean aggressively

– Use PEEP 0 - 5

5. Check plateau pressure (goal < 30), no air trapping

6. Check blood gas and titrate

Algorithm

Troubleshooting the Ventilator

Troubleshooting

Failures of Mechanical Ventilation

Hypoxia

Hemodynamic Instability

Troubleshooting

Hypoxia on the Ventilator

islodgementDOPE

EtCO2

Direct Visualization

Fiberoptic Bronchoscopy

Troubleshooting

Hypoxia on the Ventilator

islodgement

bstruction

DOPE

Pass suction catheter

Lavage

Replace ETT

Troubleshooting

Hypoxia on the Ventilator

islodgement

bstruction

neumothorax

DOPE

Bilateral breath sounds

Tracheal deviation

Ventilator peak pressures

Troubleshooting

Hypoxia on the Ventilator

islodgement

bstruction

neumothorax

quipment failure

DOPE

Bag-valve on FiO2 100%

Use PEEP valve

Check ventilator

Troubleshooting

Hypoxia on the Ventilator

islodgement

bstruction

neumothorax

quipment failure

DOPE

Troubleshooting

Failures of Mechanical Ventilation

Hypoxia

Hemodynamic Instability

Troubleshooting

Sudden Cardiovascular Collapse

Post-IntubationInduction

Loss of sympathetic

tone

Right heart dysfunction

Volume depletion

New OnsetTension PTX

Breath stacking/Air

trapping

Excessive PEEP

Hypoxia/vagal

Image courtesy Department of Environmental Health, Pitkin County, Colorado

Troubleshooting

Sudden Cardiovascular Collapse

Post-IntubationFluid bolus

Vasopressor

BV slowly, unless

intubated for acidemia

New OnsetDisconnect

the ventilator

Look for tension PTX

BV slowly, turn down PEEP

Image courtesy Department of Environmental Health, Pitkin County, Colorado

Troubleshooting

Cases

Cases

Case 1

84 y/o f (height 5’11”) with UTI presents with hypotension (BP70/30), tachycardia (P135), fever (T39.1 C), and unresponsiveness

You decide to intubate.Ventilator settings?

Cases

Lung Protective Ventilation1. Start with A/C (VC), sedation/pain control

2. Set tidal volume (6 – 8 mL/kg IBW)

3. Adjust respiratory rate for ventilation

4. Set FiO2 at 100% and wean aggressively

– Titrate PEEP to necessary FiO2 (table)

5. Check plateau pressure (goal < 30)

6. Check blood gas and titrate

Cases

Case 229 y/o m (height 5’11”) with h/o asthma

presents by ambulance after waking up unable to breath. He is no longer arousable.

P160 BP180/110 RR52 FiO2 86%

You decide to intubate.Ventilator settings?

Cases

Obstructive Lung Disease Ventilation

1. Start with A/C (VC), sedation/pain control (deep)

2. Set tidal volume (8 mL/kg IBW), higher for ventilation

3. Keep respiratory rate low

4. Set FiO2 at 100% and wean aggressively

– Use PEEP 0 - 5

5. Check plateau pressure (goal < 30), no air trapping

6. Check blood gas and titrate

Cases

Case 368 y/o m with h/o COPD was involved in

MVC and was intubated on arrival. While he is returning from CT 25 minutes later, he becomes hypoxic to 60% and bradycardic.

What is your intervention?

Cases

Hypoxia on the Ventilator

islodgement

bstruction

neumothorax

quipment failure

DOPE

Cases

Case 449 y/o f intubated for severe COPD at OSH

is transferred for ICU care. As EMS arrives, they are starting chest compressions.

What is your intervention?

Cases

Sudden Cardiovascular Collapse

Post-IntubationFluid bolus

Vasopressor

BV slowly, unless

intubated for acidemia

New OnsetDisconnect

the ventilator

Look for tension PTX

BV slowly, turn down PEEP

Image courtesy Department of Environmental Health, Pitkin County, Colorado

Cases

Summary• Thou shalt not fear mechanical ventilation. Most

problems in the ED can be resolved with sedation, respiratory rate, and FiO2

• Thou shalt not use injurious ventilatory strategies (low tidal volume)

• Thou shalt not code an asthmatic on the ventilator (low respiratory rate/air trapping)

• Maintain an algorithmic approach to critically ill patients, then think about the physiology

Mechanical Ventilation: A Primer

Nick Mohr, MDAssistant Professor

Department of Emergency MedicineDivision of Critical Care, Department of Anesthesia

University of Iowa Carver College of Medicine