Mechanical ventilation

Khaled R. Khasawneh, MD

Assistant Professor of Medicine

Division of Pulmonary and Critical Care

Mechanical Ventilation

Physiologic Causes of Hypoxemia

• Low FiO2

• Hypoventilation

• V/Q mismatch

• Shunt

• Diffusion abnormality

Physiologic causes of Hypercapnia

• PACO2 = k x VCO2 / VA

• PACO2 = k x VCO2 / VE(1 - Vd/ Vt)

• PACO2 = k x VCO2 / (Vt x F) (1- Vd/ Vt)

• VA = (Vt - Vd) x F

• PaCO2≈ 1/ VA

Definition• The pulmonary system is no longer able to meet the

metabolic demands of the body with respect to oxygenation of the blood and/or CO2 elimination

Etiologies• Primary pulmonary pathology

• Extra-pulmonary pathology

Classification• Type 1 (Hypoxemic)

• Type 2 (Hypercapnic/Ventilatory)

• Type 3 (Peri-operative)

• Type 4 (Shock)

Type 1 (Hypoxemic)

• V/Q mismatch and shunt are the most common causes in the ICU

• Pulmonary edema

• ARDS

• Pneumonia

• Lung hemorrhage

• Atelectasis

Type 2 (Hypercapnic/Ventilatory)

• Decreased CNS drive

• Neuromuscular disease

• Increased Physiologic Dead Space (Vd)

Type 3 (Peri-operative)

• Subtype of type 1

• Decreased FRC

• Supine/ obese/ ascites

• Anesthesia

• Upper abdominal incision

• Airway secretions

Type 4 (Shock)

• Ventilator therapy to decrease work of breathing

Management of Acute Respiratory Failure

• Oxygenation

• Ventilation

• Airway control

• Ventilator management

Oxygen Delivery Devices• Nasal cannula

• Simple face mask

• Venturi mask

• Nonrebreather mask

• High flow nasal cannula

• Misty Ox

Nasal cannula

• 1 LPM = 24% FIO2

• 2 LPM = 28% FIO2

• 3 LPM = 32% FIO2

• 4 LPM = 36% FIO2

• 5 LPM = 40% FIO

Simple face mask

• 5 LPM = 40% FIO2

• 7 LPM = 44% FIO2

• 7 LPM = 48% FIO2

• 8 LPM = 52% FIO2

• 9 LPM = 56% FIO2

• 10 LPM = 60% FIO2

Venturi mask

Nonrebreather mask

High Flow Nasal Cannula

Misty Ox

Non-invasive Positive Pressure Ventilation(NIPPV)

• COPD

• Pulmonary edema

• Preventing post-extubation respiratory failure

Contraindications• Cardiac or respiratory arrest

• Inability to cooperate, protect the airway, or clear secretions

• Severely impaired consciousness

• Facial surgery, trauma, or deformity

• High aspiration risk

• Prolonged duration of mechanical ventilation anticipated

• Recent esophageal anastomosis

Devices• Standard ICU ventilator

• BIPAP

Interface• Full face mask

• Oronasal mask (Face mask)

• Nasal mask

• Nasal pillows

Mode• Assist control (AC)

• Pressure support ventilation (PSV)

• Continuous positive airway pressure (CPAP)

• Bilevel positive airway pressure (BPAP)

Predictors of Success• Clinical improvement

• Improvement of the pH

• Improvement in PaCO2

Mechanical Ventilation

Ventilator

Volume Control

AC (VC) SIMV

Pressure Control

AC (PC) SIMV PS BiPAP

Triggering

• RR 10

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

• RR 10

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

Volume ControlAC SIMV

• RR 10

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

• RR 10

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

Volume ControlAC SIMV

• RR 10

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

• RR 10

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

Volume ControlAC SIMV

I+E = 6 secI= 0.5 secE= 5.5 secI:E = 1:11

• RR 30

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

• RR 30

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

Volume ControlAC SIMV

• RR 30

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

• RR 30

• TV 500 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

Volume ControlAC SIMV

I+E = 2 secI= 0.5 secE= 1.5 secI:E = 1:3

• RR 10

• TV 1000 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

• RR 10

• TV 1000 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

Volume ControlAC SIMV

• RR 10

• TV 1000 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

• RR 10

• TV 1000 ml

• FIO2 50%

• PEEP 5 cmH2O

• Flow 60L/m

Volume ControlAC SIMV

I+E = 6 secI= 1 secE= 5 secI:E = 1:5

• RR 10

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 0.5 sec

• RR 10

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 0.5 sec

Pressure ControlAC SIMV

• RR 10

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 0.5 sec

• RR 10

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 0.5 sec

Pressure ControlAC SIMV

I+E = 6 secI= 0.5 secE= 5.5 secI:E = 1:11

• RR 30

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 0.5 sec

• RR 30

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 0.5 sec

Pressure ControlAC SIMV

• RR 30

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 0.5 sec

• RR 30

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 0.5 sec

Pressure ControlAC SIMV

• RR 10

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 1 sec

• RR 10

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 1 sec

Pressure ControlAC SIMV

• RR 10

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 1 sec

• RR 10

• Pi 10 cmH2O

• FIO2 50%

• PEEP 5 cmH2O

• Ti 1 sec

Pressure ControlAC SIMV

I+E = 6 secI= 1 secE= 5 secI:E = 1:5

• Patient-triggered, pressure limited, flow-cycled breath

• Adequate spontaneous drive

• Gas flow to a preset pressure

• Support is only provided if the patient triggers the vent

• Invasive and non-invasive• No rate is set

• PS

Pressure Support

• IPAP – inspiratory positive airway pressure

• EPAP – expiratory positive airway pressure

• FIO2

BiPAP

• IPAP 10 cmH2O

• CPAP 5 cmH2O

• FIO2 50%

• PS 10 cmH2O

• PEEP 5 cmH2O

• FIO2 50%

PS VS BiPAPPS BiPAP

10

55

Peak and Plateau Pressure

CASE30 years-old male admitted with drug over dose and required ETT + MV on AC of 12/450/5 and 50% his Peak airway pressure was 35 cmH2O and Plateau pressure was 15 cmH2O.

On day 2 patient developed an episodes of decreased SPO2 . At that time Peak airway pressure was 60 cmH2O and Plateau pressure was 15 cmH2O.

What is the etiology of the patient decreased SPO2?

A) ARDS.

B) Pulmonary edema.

C) Pneumothorax

D) Right main stem mucus plug.

CASE30 years-old male admitted with drug over dose and required ETT + MV on AC of 12/450/5 and 50% his Peak airway pressure was 35 cmH2O and Plateau pressure was 15 cmH2O.

On day 2 patient developed an episodes of decreased SPO2 . At that time Peak airway pressure was 60 cmH2O and Plateau pressure was 15 cmH2O.

What is the etiology of the patient decreased SPO2?

A) ARDS.

B) Pulmonary edema.

C) Pneumothorax

D) Right main stem mucus plug.

CASE30 years-old male admitted with drug over dose and required ETT + MV on AC of 12/450/5 and 50% his Peak airway pressure was 35 cmH2O and Plateau pressure was 15 cmH2O. He developed fever and chills and was difficult to wean from the ventilator secondary to aspiration pneumonia.

On day 10 patient developed an episodes of decreased SPO2 . At that time Peak airway pressure was 60 cmH2O and Plateau pressure was 40 cmH2O.

What is the etiology of the patient decreased SPO2?

A) ARDS.

B) Bronchospasm.

C) Right main stem mucus plug.

D) Biting on the ETT.

CASE30 years-old male admitted with drug over dose and required ETT + MV on AC of 12/450/5 and 50% his Peak airway pressure was 35 cmH2O and Plateau pressure was 15 cmH2O. He developed fever and chills and was difficult to wean from the ventilator secondary to aspiration pneumonia.

On day 10 patient developed an episodes of decreased SPO2 . At that time Peak airway pressure was 60 cmH2O and Plateau pressure was 40 cmH2O.

What is the etiology of the patient decreased SPO2?

A) ARDS.

B) Bronchospasm.

C) Right main stem mucus plug.

D) Biting on the ETT.

CASE30 years-old male admitted with drug over dose and required ETT + MV on AC of 12/450/5 and 50% his Peak airway pressure was 35 cmH2O and Plateau pressure was 15 cmH2O. He was difficult to wean from the mechanical ventilation.

On day 10 patient developed an episodes of decreased SPO2 . At that time Peak airway pressure was 35 cmH2O and Plateau pressure was 15 cmH2O.

What is the etiology of the patient decreased SPO2?

A) ARDS.

B) Bronchospasm.

C) Right main stem mucus plug.

D) Pulmonary embolous.

CASE30 years-old male admitted with drug over dose and required ETT + MV on AC of 12/450/5 and 50% his Peak airway pressure was 35 cmH2O and Plateau pressure was 15 cmH2O. He was difficult to wean from the mechanical ventilation.

On day 10 patient developed an episodes of decreased SPO2 . At that time Peak airway pressure was 35 cmH2O and Plateau pressure was 15 cmH2O.

What is the etiology of the patient decreased SPO2?

A) ARDS.

B) Bronchospasm.

C) Right main stem mucus plug.

D) Pulmonary embolus.

Peak and Plateau Pressure

Auto-PEEP

Santanilla JI, Daniel B, Yeow ME. Mechanical ventilation. Emerg Med Clin North Am. 2008;26(3):849-862.

Auto-PEEP• Increase intrathoracic pressure

• Alveolar overdistension

• Increase work of breathing required to trigger the ventilator

Santanilla JI, Daniel B, Yeow ME. Mechanical ventilation. Emerg Med Clin North Am. 2008;26(3):849-862.