special perioperative mechanical ventilation modes

Special Perioperative Mechanical Ventilation Modes : HJV,

HFOV, Non-invasive VentilationElizeus Hanindito

Dept. Anesthesiology Airlangga University – dr. Soetomo General Hospital

Non-invasive Mechanical Ventilation

• Delivery of ventilation to the lungs without an invasive airway (endotracheal or tracheostomy)

• Avoid the adverse effects of intubation or tracheostomy (early and late)

• Reduction in inspiratory muscle work & avoidance of respiratory muscle fatigue

• Tidal volume is increased• CPAP counterbalances the inspiratory

threshold work related to intrinsic PEEP.• NIV improves respiratory system

compliance by reversing microatelectasis of the lung.

How does NIV work ?

• Noninvasiveness – Application (compared with endotracheal

intubation) a.Easy to implement b.Easy to remove (allows intermittent application)– Improves patient comfort– Reduces the need for sedation – Oral patency (preserves speech, swallowing, and

cough, reduces the need for nasoenteric tubes)

Advantages of NIV

Advantages of NIV

• Avoid the resistive work imposed by the endotracheal tube

• Avoids the complications of endotracheal intubation – Early (local trauma, aspiration)– Late (injury to the the hypopharynx, larynx, and

trachea, nosocomial infections)

System – Slower correction of gas exchange abnormalities– Increased initial time commitment– Gastric distension

Mask – Air leakage– Transient hypoxemia from accidental removal– Eye irritation– Facial skin necrosis –most common complicationL

Lack of airway access & protection– Aspiration

Disadvantages of NIV

NIPPV : Non-invasive mechanical ventilation.

Modes: CPAP

BIPAP

(CPAP + Pressure-Support)

DefinitionCPAP : It is a modality of respiratory support in

which increased pulmonary pressure is provided artificially during the expiratory phase of the respiration in a spontaneously breathing neonate.

CPAP

SpontaneousVentilation

CPAPPRESSURE (cm H2O)

TIME0

Continuous Positive Airway Pressure (CPAP)

• Increasing compliance , FRC• Decreasing IP shunting , WOB• Decreasing resistance , RR• Indication : FRC , airway collapse , weaning , abnormal

BGA• RDS , apnea of prematurity , MAS

Indications of CPAP

• Respiratory distress : moderate /severe retraction , nasal flaring , grunting

• Post extubation.• P aO2 < 60 with FiO2 > 0.6 ( O2 hood).

Dr. Gautam Ghosh

Ranges ET Tube Nasal Comment

Low 3—4 4—5 CPAP< 3 not useful

Medium 5—7 6—8 Good range

High 8--10 9--10 Adverse effects common

Fi O2 controlled from 0.2 to 1.0 with CPAP.

CPAP ranges

Guidelines for CPAP

• Start with nasal CPAP of 5—6 cm & FiO2 0.4—0.5• Increase CPAP by 1 cm if required• Reach a CPAP of 8—9 cm.• Now increase FiO2 in small steps of 0.05 up to 0.8• Clinical /ABG / SpO2 > 30min in each step• Do not raise FiO2 before pressure : may remove

hypoxic stimulus -- apnea• Revert to IMV if not responding

Optimum CPAP

• Comfortable baby / pink / normal BP• No retraction / grunt• No cyanosis / normal CRT• SpO2 > 90-93 %• BGA : PaO2 60-80 / PaCO2 40-45 /p H 7.30-7.40.

Practical Points in CPAP• Warm gases at 34—37° C & humidify.• Gas flow (2.5 x minute ventilation) at 5-8 L/mnt

minimum• Look for nasal or oral blocks by secretion• Oro-gastric suction is a must• Stabilize the head with a cap and string• Change CPAP circuit/prong every 3 days• Asepsis• Sedation (prn)

Failure of CPAP

• Retraction / Grunt ++• Apnea on CPAP• PaO2 < 50 in FiO2 > 0.8 ( nasal CPAP >8cm)• PaCO2 > 55• Baby not tolerating CPAP.• Commonest cause : delay in starting

Weaning from CPAP

• Reduce nasal CPAP to < 8 cm (1 cm decrement)• Reduce FiO2 by 0.05 to 0.4• Reach a level of CPAP 4cm / FiO2 0.4• Remove CPAP and replace a O2 hood.

The CPAP delivery system consists of three components: • the circuit for continuous flow of inspired gases.• the interface connecting the CPAP circuit to the infant’s airway.• a method of creating positive pressure in the CPAP circuit.

CPAP delivery system

Dual flow (IFD) CPAP

Bi-level mechanical ventilationBIPAP

BiPAP is CPAP plus Pressure Support Ventilation

IPAP = 12

EPAP = 4

PS = 8

• 10-12/min - Adult

• 20 + 3 - Child

• 30- 40 - New born

Respiratory Rate

HIGH FREQUENCY VENTILATION

Types of HFV

• High Frequency Oscillatory Ventilation• High Frequency Jet Ventilation• High Frequency Positive Pressure

Ventilation

HFOV - General Principles

• A CPAP system with piston displacement of gas

• Active exhalation

• Tidal volume less than anatomic dead space (1 to 3 ml/kg)

• Rates of 180 – 900 breaths per minute

• Lower peak inspiratory pressures for a given mean airway pressure as compared to CMV

HFOV Objectives

• Support Lung– Oxygenation– CO2 Removal

• Reduce Vent Induced Lung Injury

Ventilator Associated Lung Injury

• All forms of positive pressure ventilation (PPV) can cause ventilator associated lung injury (VALI).

• VALI is the result of a combination of the following processes:

–Barotrauma–Volutrauma–Atelectrauma–Biotrauma

Pressure and Volume Swings

INJURY

INJURY

CMV

HFOV

During CMV, there are swings between the zones of injury from inspiration to expiration.

During HFOV, the entire cycle operates in the “safe window” and avoids the injury zones.

Gas entering the lungs travels centrally, while gas leaving the lungs swirls around it

Neonatal Uses of HFOV

• Hyaline membrane disease• Persistent pulmonary hypertension• Pulmonary interstitial emphysema (prevention and treatment)• Sepsis / Pneumonia• Congenital diaphragmatic hernia• Meconium aspiration syndrome

Timing CMV HFOV• Inadequate oxygenation that cannot safely be treated

without potentially toxic ventilator settings and, thus, increased risk of VALI.

• Objectively defined by:– Peak inspiratory pressure (PIP) > 30-35 cm H2O

– FiO2 > 0.60 or the inability to wean

– Mean airway pressure (Paw) > 15 cm H2O

– Peak end expiratory pressure (PEEP) > 10 cm H2O– Oxygenation index > 13-15

Ventilator Settings

• Hertz = BPM• Power (Amplitude P) • Paw• FiO2

• Bias Flow• Inspiratory time %

Initial Frequency Settings

• Guidelines for setting the initial frequency.

• Adjustments in frequency are made in steps of ½ to 1 Hz.

Patient Weight HertzPreterm Neonates 10 to 15

Term Neonates 8 to 10Children 6 to 8Adults 5 to 6

HFOV Initial Settings

• FiO2 = 1.0• Hz = 5.0• Power setting = 5• Paw = CMV + 5• Insp Time = 33%• Flow = 30

Weaning

• Wean FiO2 for Sat’s > 90%• When FiO2 60%, wean Paw by 1• Return to CMV when:

– FiO2 < 40%– Paw 15-20– Amplitude < 40

HFOV: Conversion

• Pressure limited ventilation• Delivered tidal volume ~6 ml/kg• PEEP ~10 cm H2O • Adjust for Paw same as HFOV• FiO2 ~40 - 50%

Signs of Failure

• OI > 42 at 48 hrs HFOV• Unable to wean FiO2 > 10% within 24 hours• Unable to PaCO2 <100 with pH 7.25