Sarah Adams

RT 214

December 9, 2010

Objectives Six W’s and One H

What is HFOV?

Why should HFOV be used?

Who would this benefit?

When should HFOV be considered?

Where do you start?

How is HFOV implemented?

Weaning

What is HFOV? Alternative mode of ventilation

Based on protective “open lung” principles

Keep it simple: CPAP with a wiggle

Continuous airway pressure (mPaw and bias flow) keeps the lungs open

Oscillatory movement (amplitude and frequency) produces Vt

Vt is often less than deadspace

What is HFOV? SensorMedics 3100B

Only oscillator FDA-approved for use with adult and pediatric patients weighing > 35 kg

Uses a magnetically-driven reciprocating piston

Forward and backward movement of piston creates active inhalation and exhalation

Why should HFOV be used? Rescue therapy

ARDS patients who are failing CMV

Prophylactically

At-risk patients

Decreases the risk of developing VILI/VALI

Derdak et al (2002) found that there was a reduction in inflammatory mediator levels with HFOV as compared to CMV when applying similar mPaw values

Why should HFOV be used? Lung Protection

The entire ventilatory cycle is contained within the “safe zone”

Overdistension and derecruitment are avoided

INJURY

INJURY

CMV

INJURY

INJURY

HFOV

Who would this benefit? ARDS patients

Patients at-risk for developing VILI/VALI

Special subpopulations:

Major Burn

Trauma

Traumatic Brain Injury

Who would this benefit? Major burn patients

54% of patients on CMV develop ARDS

Treatment of ARDS in burn patients is two-fold and HFOV can supplement both aspects

First, support hypoxemic patient with noncompliant lungs

Second, surgical excision and wound closure

Cartotto et al (2005) states that the need for burn wound surgery influences their decision to start HFOV before surgery due to patients’ rapid improvement in oxygenation

Who would this benefit? Major burn patients with smoke inhalation injury

Improvement in oxygenation was slower and less substantial

72 hrs for improvement, compared to 12 hrs for burn-only patients

Cartotto does not consider smoke inhalation injury a contraindication

Who would benefit? Trauma patients

HFOV has been found to significantly improve oxygenation in patients with blunt trauma

Severity of traumatic injury and organ system failure are greater predictors of survival than respiratory parameters in these patients

The Adult HFOV Outcome Assessment has been found to be non-reliable in these patients, the mortality prediction is lower than actuality

Who would this benefit? Traumatic Brain Injury Patient mortality was found to be much less than the

predicted value calculated from the Adult HFOV Outcome Assessment

Lung protective strategies and brain protective strategies appear contradictory Permissive hypercapnia v. normocapnia goals

However, improvement has been noted in both oxygenation and ICP

Continuous monitoring of ICP, CPP, and PaCO2 is needed

When should HFOV be considered? Criteria recommended by SensorMedics: FiO2 ≥ 60

PEEP ≥ 10

PaO2/FiO2 ratio < 200

Plateau pressure > 30 cmH20

Oxygenation Index (OI) > 24

Bilateral infiltrates on a chest x-ray consistent with ARDS

Contraindications: None, although HFOV may be less effective in

COPD/asthma patients due to air-trapping and hyperinflation

When should HFOV be considered? Oxygenation Index (OI)

From respiratory standpoint – primary indicator of mortality

Calculated as: OI = FiO2 x mPaw

Experts agree: Early intervention produces better outcomes

PaO2

When should HFOV be considered? Ideally, the patient should be hemodynamically stable

MAP ≥ 75 mmHg

If MAP <75 mmHg, fluid boluses and vasopressors

pH > 7.20

If pH ≤ 7.20, aggressive measure should be taken before transition

Manipulation of PaCO2 is significantly slower than on CMV

When should HFOV be considered? After STAT procedures which cannot be performed in

the unit(CT scans, MRIs)

Oscillator is not able to be used during transport

Electrical needs exceed battery capability

Requires two separate pressurized gas sources

After the airway is deemed to be patent

Suction

If there are concerns about airway patency, bronchoscopy recommended

When should HFOV be considered? After patient sedation/paralysis

Spontaneous respirations by the patient can interfere with the oscillator’s ability to effectively ventilate

Large changes in pressure will cause the ventilator to alarm and the oscillatory function to pause

Patient will receive only bias flow of gas when the oscillatory function is paused

Where do you start? Become familiar the machine

Control panel

Piston

Disposable diaphragm

Non-compliant patient circuit

Water trap

Heated humidifier (not seen)

Blender (not seen)

Where do you start? Become familiar with the control panel/parameters

mPaw

Power

Frequency

Inspiratory time percent (Ti%)

Bias flow

Where do you start? mPaw

Adjustment knob manipulates a balloon valve in the expiratory limb of the patient circuit

Balloon valve is able to restrict the flow of expiratory gas (PEEP)

Determines lung volume

Primary control for oxygenation

An incorrectly set bias flow can either hinder or enhance mPaw

Where do you start? Power

Control knob adjusts amplitude, which is shown on a numerical display

Amplitude is the change in pressure created by the forward and backward movement of the piston

This pressure gradient determines Vt

Primary control for ventilation

Where do you start? Frequency

Adjusts the amount of time the piston is allotted for forward and backward movement

Value is measured in Hertz (Hz)

1 Hz = 60 cycles(breaths)/minute

Secondary control for ventilation

Relationship between frequency and Vt is inverse

As frequency increases, volume displacement decreases, which results in a decreased Vt

Where do you start? Inspiratory time percent (Ti%)

Adjusts I:E ratio

Allots the percent of time the piston spends in forward motion during one ventilatory cycle

Default setting is 33% (I:E ratio of 1:2)

Tertiary control for ventilation

Once an appropriate setting is found (usually left to the default), it is rarely adjusted

Where do you start? Bias flow

Adjusted with a knob, monitored with a Thorpe tube

When HFOV is being initiated, this is the first parameter to be set

If the flow is insufficient, then desired mPaw cannot be reached

If the flow is too high, the negative force of the active exhalation may be negated

Where do you start? Oscillatory function

The button is either on or off

FiO2

Controlled independent of the ventilator with the use of a blender

Pre-use check

Patient circuit calibration

Must be completed with every circuit change

Ventilator performance check

Where do you start? Set up heated humidifier

Attach a closed-system suction catheter

Suctioning required at least every 12 hrs to prevent occlusion of the ETT

Patient/family education

Complications: pneumothorax, hemodynamic compromise, mucus plugging, anesthesia-related, possible exposure to infectious droplets

Noise

Chest wiggle

How is HFOV implemented? Recruitment maneuvers should be performed upon

initiation of HFOV

Also, after patient circuit disconnection, suctioning, or when SpO2 decreases >5%

Amount of pressure and timing is facility specific

Oscillatory function should be paused during maneuver

If a permissible cuff leak is being used to control PaCO2, the cuff should be reinflated for the duration of the maneuver

Contraindications: pneumothorax, unstable hemodynamics

How is HFOV implemented? Initial settings:

Bias flow is to be set between 25-40 LPM

mPaw is to be set 5 cmH2O higher than CMV mPaw

If hemodynamically unstable, mPaw may be set at 2-3 cmH2O higher than CMV mPaw

Set the power to 4.0 and increase until adequate chest wiggle is achieved

Adequate chest wiggle can be determined by placing a tongue depressor on the patient’s mid-thigh and increase the power until the patient visibly shakes from shoulders to mid-thigh

How is HFOV implemented? Initial settings:

Frequency should be set in the range of 5-6 Hz

Ti% should be left to the default

FiO2 set to 100%

How is HFOV implemented? Confirmation of appropriate settings can be achieved

by chest x-ray and ABG, both to be done within 1 hr of transition

Visualization that the 9th posterior rib is above the diaphragm shows adequate lung expansion and appropriate mPaw setting

The oscillatory function should not be paused during the chest x-ray

Chest x-rays should be reordered whenever there is a suspected change in lung volume or disease process

How is HFOV implemented? Confirmation of appropriate settings can be achieved

by chest x-ray and ABG, both to be done within 1 hr of transition

If ABG shows elevated PaO2:

FiO2 should be weaned in 5% increments, until <60%

If lung volume remains the same, it is safe to wean to 40%

If lungs are near hyperinflation, mPaw should be decreased by 1-2 cmH2O while also weaning FiO2 to 40%

After FiO2 has been weaned to 40%, mPaw should be decreased by 1-2 cmH2o every 4-6 hrs

How is HFOV implemented? If ABG shows a PaO2 that is lower than acceptable:

Increase FiO2 to 100%

Increase mPaw by 3-5 cmH20 every 20-30 minutes until oxygenation improves

Lung volume should be rechecked via chest x-ray

If ARB shows a pH that is higher than acceptable:

Decrease the power, while maintaining adequate chest wiggle

If not resolved, then frequency should be increased

If not resolved, then decrease Ti%, to 33%

How is HFOV implemented? If ARB shows a pH that is lower than acceptable:

Increase the power, while maintaining adequate chest wiggle

If not resolved, then frequency should be decreased

Minimum of 3Hz

If not resolved, generate cuff leak

Slowly deflate cuff until mPaw decreases by 5 cmH2O

Then increase bias flow until previous mPaw value returns

If not resolved, then increase Ti%, to 50%

Permissive hypercapnia: as long as the patient’s pH remains >7.20, an elevated PaCO2 is not corrected

How is HFOV implemented? General patient assessment every 2 hrs

Chest wiggle factor

Watch for changes in vibration and symmetry

Auscultation

Normal BS will not be heard, but changes within the lungs can alter the sound of the pistons as heard through the lungs

Perfusion status via capillary refill

VS

Weaning Can be considered after the underlying disease process

has resolved, and the patient tolerates the following:

mPaw 22-24 cmH20

SpO2 >88%, with FiO2 ≤ 40%

When back on CMV, a mode that is also lung protective (PVC, PRVC) is beneficial

mPaw on CMV should be the same as on HFOV

Vt should remain low-normal (6-10 ml/kg IBW)

Rate, PEEP, FiO2 determined by ABG values

Summary HFOV appears to be a safe alternative therapy for

patients who are failing CMV

Main benefit is improved oxygenation

This has been found not to ensure patient survival

Early intervention improves outcome

Questions?