Mechanical Ventilation in Special Conditions

Mechanical Ventilation: Outline

• Head injury• Chest Trauma• Bronchopleural Fistula

Traumatic Brain Injury

Prevalence of extracerebral organ dysfunction in TBI

Cerebral Compliance Curve

Intracranial volume

Intracranial pressureCPP

CPP= MAP-ICP

Cerebral Compliance Curve

50

Cerebral Blood Flow CPP

PaO2

PaCO2

100 150

Head Injury: MV Monitoring

• Peak alveolar pressure, airway pressure, auto-PEEP

• PaCo2 end tidal PCO2• Intracranial pressure• Jugular venous oxygen saturation• Pulse oximetry• Heart rate and systemic blood pressure

Hyperventilation in Traumatic Brain Injury

1. Causes cerebral vasoconstriction 2. Decreases cerebral blood flow3. Decreases cerebral blood volume4. Increases ICP5. Has been proven to be of benefit in head

injuries

Head Trauma

• Cerebral physiology– ICP– CBF– Cerebral oxygenation : SJO2, PbrO2

• Hyperventilation• Lung protective strategy• PEEP• Extubation

Hyperventilation in TBI

• Chronic hyperventilation (PCO2 < 25) should be avoided

• Prophylactic hyperventilation (PCO2 < 35) in the first 24 h should be avoided

• May be necessary for a brief period with acute neurologic deterioration

Head Trauma• Lung protective strategy

– Hypoventilation PCO2 ICP – No evidence of detrimental effect– Use protective ventilation– Observe ICP and CPP if PCO2▲

• PEEP– ICP – MAP – Depends on compliance

• Extubation– LOC– Cough– Tracheal secretions

+

Head Trauma

• Lung protective strategy– Hypoventilation PCO2 ICP – No evidence of detrimental effect– Use protective ventilation– Observe ICP and CPP if PCO2▲

• PEEP– ICP – MAP – Depends on compliance

+

Head Trauma

• Extubation– LOC– Cough– Tracheal secretions

Hyperventilation & CBF

Head TraumaCBF and ICP with hyperventilation

▼ICP

►CBF◄

Head Trauma

• Extubation– LOC– Cough– Tracheal secretions

Intrathoracic Pressure (-3 cm H2O)

CPP = MAP – ICP

MAP (90)= CO X SVRVenous Return

ICP= 10

ICP =30

Maintain adequate MAP• Adequate CO• Use inotropic Agents• Adequate filling pressures• Avoid hypotensive agents• Treat infection abruptly

Avoid ↑ Intrathoracic Pressure• Suppress Valsalva

maneuvers• Suppress cough• ↓ Mean airway pressure• Minimize use of PEEP• Treat distended abdomen

CSF Drainage• HOB > 30 degree• Head in neutral

position• Vetriculostomy

Decrease Oxygen Demand• Prevent seizure• Sedation• Treat pain• Barbiturate coma• Avoid hyperthermia• ? hypothermia

Decrease Brain Water• Mannitol• Avoid D5%• Diuretics

VasoconstrictionPa co2 25-30

Decompressive Craniotomy

Underlying lungdisease

Titrate FiO2 for SpO2 ≥ 92%

no ↓ rate

yes

↓ VT

yes

ICP <20

no↑ FiO2

70-100

FiO2 >0.6

↑ rate

<20

>20

ICP

More aggressiveMedical therapy

Slowly ↓ rate to initial setting

no

ICP

yes

↑ PEEP

CMV (A/C), PCV or VC, VT 4-8 mL/kg, FiO2 1, rate20/min TI1s, PEEP 5 cm H2O

yesCMV (A/C), PCV or VC, VT 4-8 mL/kg, FiO2 1, rate15/min TI1s, PEEP 5 cm H2O

no

>45↑ rate PCO2

↓ FiO2>100

>20

yes

FiO2 > 0.6

<70

MaintainVentilator

Setting

<20

no

Pplat > 30<35

PaO2

35-45

Chest traumaWho Gets Admitted?

• Sternal fractures mediastinal injury• Any 1th, 2nd, 3rd Rib fractures• > 1 Rib fracture in any region• Pulmonary contusion• Subcutaneous emphysema• Traumatic asphyxia• Flail segment• Arrhythmia or myocardial injury

Flail Chest

Flail chest

Flail Chest

BPF

BPF

BPF

Adverse effects of BPF in the ventilated patient

Incomplete lung

expansionLoss of TV

Inability to remove

CO2Loss of PEEP

Pleural space

infection

Factitious ventilator cycling

Guidelines for ventilator management in the patient with BPF

Reduce MAP & RR• Wean patient completely if possible• Partial ventilatory support

– low-rate SIMV or PSV• Minimize minute ventilation• Use of permissive hypercapnia• Avoid patient positions that increase

the leak • Treat bronchospasm• Consider unconventional measures

– Bronchoscopic techniques– HFV– ILV

Independent lung ventilation

Independent Lung Ventilation