niv weaning

By

Gamal Agmy,MD,FCCP Professor Of Chest Diseases

Assiut University

Introduction

* NIPPV is recent phenomenon, mainly because of

advances in noninvasive interfaces and ventilator

modes

* The efficacy of noninvasive positive-pressure

Ventilation has been demonstrated for acute

pulmonary edema, for respiratory failure in

immunocompromised patients, and to facilitate

extubation in COPD patients.

* Patients who develop respiratory failure or who

refuse intubation are potentially good candidates for

noninvasive positive-pressure ventilation

*Several factors are vital to the success of noninvasive

positive-pressure ventilation: careful patient selection;

properly timed initiation; comfortable, well-fitting

interface; coaching and encouragement; and careful

monitoring.

*Noninvasive ventilation should be used to avert

endotracheal intubation rather than as an alternative to

it.

Definition

The application of positive pressure ventilation

without using an endotracheal tube.

or

As the provision of ventilatory assistance to the

lungs without an invasive artificial airway

History Until the early 1960s, negative-pressure ventilation in the

form of tank ventilators was the most common type of

mechanical ventilation outside the anesthesia suite

With the introduction of nasal CPAP to treat obstructive sleep

apnea in the early 1980s, NIPPV rapidly displaced negative-

pressure ventilation as the treatment of choice for chronic

respiratory failure in patients with neuromuscular and chest wall

deformities

The past 20 years, noninvasive ventilation has moved

from the outpatient to the inpatient setting, where it is

used to treat acute respiratory failure.

Non-invasiveVentialtion

1- Positive pressure

2-Negative Pressure

Advantage(NIPPV)

*Decreased direct upper airway trauma & bypass of

the upper airway defense mechanisms

*Allows patients to eat orally, vocalize normally, and

expectorate secretions.

* Noninvasive ventilation reduces infectious hospital

including pneumonia,sinusitis, and sepsis.

* lowers morbidity and mortality

* Shorten hospital length of stay, thus reducing costs.

Goals of NIV

Relieve symptoms

Reduce work of breathing

Offset the effect of i PEEP

Improve gas exchange

Minimize risk of barotrauma

Avoid intubation

Indication Airway Obstruction

COPD

Asthma

Cystic fibrosis

Obstructive sleep apnea or obesity hypoventilation

Upper airway obstruction

Facilitation of weaning in COPD

Extubation failure in COPD

Indication Hypoxemic Respiratory Failure

ARDS

Pneumonia

Trauma or burns

Acute pulmonary edema (use of CPAP)

Immuno compromised patients

Restrictive thoracic disorders

Post operative patients

Do-not-intubate patients

During bronchoscopy

Exclusion Criteria

1. Respiratory arrest

2. Medically unstable

3. Unconscious, unable to protect airways

4. Excessive secretions

5. Significant vomiting

6. Agitated or uncooperative

7. Facial trauma, burns, surgery or anatomic

abnormalities interfering with mask

application

PATIENT SELECTION

Primary-step

Identify patients in need of ventilatory assistance by using clinical

and blood gas criteria.

Good candidates are those with moderate to severe dyspnea,

tachypnea, and impending respiratory muscle fatigue( use of

accessory muscles of breathing or abdominal paradox).

The level of tachypnea ( COPD when the respiratory rate exceeds

24 breaths per minute & hypoxemic respiratory failure, higher

respiratory rates are used, in the range of 30 to 35 breaths per

minute.

second step

Exclude patients for whom noninvasive ventilation would

be unsafe.

Those with frank or imminent respiratory arrest

Patients who are medically unstable with hypotensive shock,

uncontrolled upper gastrointestinal bleeding, unstable arrhythmias,

or life-threatening ischemia .

who are uncooperative, unable to adequately protect their upper

airway or clear

PREDICTORS OF SUCCESS DURING

ACUTE APPLICATIONS OF NPPV

Younger age

Lower acuity of illness (APACHE score)

Able to cooperate; better neurologic score

Able to coordinate breathing with ventilator

Less air leaking, intact dentition

Hypercarbia, but not too severe (PaCO2 > 45 mm

Hg, < 92 mm Hg)

Acidemia, but not too severe (pH < 7.35, > 7.10)

Improvements in gas exchange and pulse and respiratory rates within first 1-2 h

INITIATION OF NONINVASIVE VENTILATION

1-Appropriate candidate selected,

2-Ventilator and interface must be chosen,

3-Ventilator settings must be selected,

4-Location ( Icu or step-down unit that offers adequate

continuous monitoring until stabilized)

Comporison of Noninvasive mechanical ventilators with

standard critical care ventilators

NIMV offers a more portable technology due to the reduced size of the

air compressor.

Because of this reduction in size, these noninvasive ventilators do not

develop pressures as high as their critical care ventilator counterparts.

(>30 cm H20)

Noninvasive ventilators have a single-limb tubing circuit that delivers

oxygen to the patient and allows for exhalation.

lack oxygen blenders or sophisticated alarm or battery backup systems

Modes of Noninvasive Mechanical Ventilation

* volume ventilation, initial tidal volumes range from

10 to 15 mL.kg.

1-Pressure modes

2-volume modes

Pressure-cycled vents are better tolerated than volume-cycled vents

Pressure modes

**Continuous Positive Airway Pressure(CPAP)

Continuous positive airway pressure (CPAP) is not NIV

It provides positive airway pressure throughout the respiratory cycle.

This static, positive pressure is maintained constantly during inhalation

and exhalation

CPAP is not a stand-alone mode of assisted mechanical ventilation. It is

equivalent to positive end-expiratory pressure (PEEP) and facilitates

inhalation by reducing pressure thresholds to initiate airflow.

This mode should never be used in patients who may have apneic

episodes because of the lack of a backup rate.

Pressure modes

Spontaneous Modes In spontaneous mode, the airway pressure cycles between an inspiratory

positive airway pressure (IPAP) and an expiratory positive airway

pressure (EPAP).

This is commonly referred to as bilevel or biphasic positive airway

pressure (BL-PAP or BiPAP). The patient's inspiratory effort triggers the

switch from EPAP to IPAP. The limit during inspiration is the set level of

IPAP.

The inspiratory phase cycles off, and the machine switches back to EPAP

when it detects a cessation of patient effort, indicated by a decrease in

inspiratory flow rate, or a maximum inspiratory time is reached, typically

2-3 seconds.

Tidal volume (Vt) varies breath to breath and is determined by degree of

IPAP, patient effort, and lung compliance.

Spontaneous mode depends on patient effort to trigger inhalation. A

patient breathing at a low rate can develop a respiratory acidosis.

Spontaneous/timed (ST) mode

The trigger in the ST mode can be the patient's effort or an elapsed time

interval, predetermined by a set respiratory backup rate.

If the patient does not initiate a breath in the prescribed interval, then

IPAP is triggered. For machine-generated breaths, the ventilator cycles

back to EPAP based on a set inspiratory time.

For patient-initiated breaths, the ventilator cycles as it would in the

spontaneous mode.

Pressure modes

Conceptually:

One can consider BiPAP as PEEP with pressure support (PS).

The pressure during the inspiratory phase is termed IPAP and

is analogous to PS.

The pressure during the expiratory phase is termed EPAP and

is analogous to PEEP.

The IPAP is necessarily set higher than EPAP by a minimum

of 5cm H2O, and the difference between the two settings is

equivalent to the amount of PS provided

Initiating Noninvasive Mechanical Ventilation

Either a face mask or a nasal mask can be used, but a nasal mask is

generally better tolerated.

A respiratory therapist must measure the patient to ensure a good fit and

seal.

Initially supply 3 to 5 cm H2O of CPAP with supplemental oxygen.

sequentially increase the CPAP pressure by 2 to 3 cm H2O increments

every 5 to 10 minutes (ABG-Pulse oximetry)

Recommended initial settings for BiPAP machines in the noninvasive

support of patients in respiratory distress or failure are IPAP of 8 cm H2O

and EPAP of 3 cm H2O, for a pressure support (IPAP minus EPAP) of 5

cm H2O.

The level of supplemental oxygen flowing into the circuit should be

governed by goal pulse oximetry and corroborated by ABG results as

necessary; it is appropriate to initiate therapy with 2 to 5 L/minute, but

this amount should be adjusted with each titration of IPAP or EPAP.

The intrinsic positive end-expiratory pressure

(PEEPi), or auto-PEEP, cannot be measured by

a noninvasive ventilator; therefore, EPAP

should generally be maintained below 8 to 10

cm H2O to be certain that it does not exceed

PEEPi in patients with obstructive lung disease.

The IPAP must always be set higher than EPAP

Conceptually:

Pressure pre-set

(PCV/PSV)

Varying inspiratory volume,

Constant inspiratory pressure

Advantage:

Compensation for leakage,

Best tolerated

Disadvantage:

Instability of tidal volume in

case of increased airway

resistance

Volume pre-set

(VCV)

Constant inspiratory volume,

Varying inspiratory pressure

Advantage:

Stability of tidal volume even in

case of increased airway

resistance

Disadvantage:

high inspiratory pressure,

No leak compensation

Volume versus pressure: No differences in:

• Improvements in sleep quality

• Improvements in blood gases

But:

• More side effects during volume pre-set

Windisch W. et al. Respir Med 2005; 99: 52-59

Volume versus pressure: No differences in:

• Sleep quality

• Blood gases

• Quality of life

• Physical activity

• Spontaneous breathing

Tuggey JM et al. Thorax 2005; 60: 859-864

Hybird modes combine the advantages of pressure pre-set and volume-

pre-set

AVAPS

Average Volume Assured Pressure

Support • Automatic adjustment of inspiratory pressure (range setting)

• Target volume set

• Measurement of inspiratory pressure and expiratory volume

• Calculation of missing patient tidal volume

• Changes of inspiratory pressure (1 cmH2O/min)

Assurance of tidal volume + comfort of pressure pre-set

AJRCCM 2001;163:283-91

Rational of NPPV in COPD

Management Strategies

COPD

– Main goal to decrease work of breathing (decreasing

V/Q mismatch) and provide adequate ventilation

– Relatively low EPAP: 5-8cm H2O (assuming no

obesity or sleep disordered breathing)

– Relatively moderate IPAP+EPAP: 10-14cm H2O

– Goal to have at least a 5cm H2O differential between

EPAP and IPAP+EPAP; may need to go higher

depending on ventilation requirements

» ie BiPAP 14/10 or 8/5

From a Cochrane Review

A meta-analysis of 14 studies of NIV in COPD

exacerb showed:

mortality ( RR 0.52 )

need for intubation ( RR 0.41 )

pCO2, and resp rate faster

length of stay by 3.24 days

complications of treatments


CHF

– Goal is to decrease work of breathing, decrease

afterload and decrease overall static pressure

– Relatively moderate EPAP: 6-12 cm H2O

– Relatively low IPAP+EPAP: 12-18cm H2O

– Patient will benefit mostly with EPAP unless

other concurrent disease ( COPD, Obesity-

Hypoventilation)

» Typical starting point: BiPAP 10/6


Obesity-Hypoventilation Syndrome

– Goal of therapy is to decrease work of breathing and

increase ventilation

– Combined disease as >90% will also have concurrent

Obstraction sleep Apnea(OSA)

– EPAP: usually on the higher side; enough to overcome

OSA and cardiopulm disease: ~10cmH2O, more for

bigger individuals

– IPAP+EPAP: at least a 4cm H2O differential

– Need to adjust according to ventilation requirements;

may benefit from back up rate


Sleep Disordered Breathing

– Most often post-op with known OSA or as a

complication associated with admit (CHF or

Obesity-Hypoventilation)

– For elective admit with known OSA: usual

CPAP/BiPAP unless physiologic changes with

acute illness, surgery or narcotics.


Neuromuscular Disease

– Goal to decrease work of breathing, decrease

fatigue, assist ventilation

– EPAP: usually low; 4-5cm H2O

– IPAP+EPAP: at least 4cmH2O differential

– May benefit from backup rate


Other causes of respiratory failure

– Pneumonia/ARDS

– Cancer and respiratory failure

– Post-op management

» Settings depend on disease and other

cardiopulmonary disease

» Most often used as a bridge to mechanical

ventilation or for pts DNR/DNI

» Usually moderate settings: 12/8 or 14/8

The device that makes physical contact between the patient and the

ventilator is termed the interface.

Interfaces for NPPV come in a variety of shapes and sizes

Include:

Nasal mask,Nasal pillow, Oronasal mask (face mask) or the helmet.

Ideally, interfaces should be comfortable, offer a good seal, minimize

leak, and limit dead space.

Interface *Definition:

Standard interfaces

Facial masks

advantages:

– sufficient ventilation also during mouth breathing

– sufficient ventilation in patients with limited co-operation

disadvantages:

– coughing is difficult

– skin lesions (bridge of the nose)

Nasal masks

advantages:

– better comfort

– good seal

– coughing is possible

– communication is possible

disadvantages:

– effective in nose breathing only

– good co-operation is necessary

Standard interfaces

Nasal prong/nasal pillow systems

for patients with

claustrophobia

for patients with allergies

against straps

for low to moderate

pressures only

(< 20 cmH2O)

Standard interfaces

total-face masks

• Safe interface for acute respiratory insufficiency with high pressures

• well tolerated by the patients

Standard interfaces

helmet

• well tolerated by the patient

• no direct contact to the skin of

the face

• large dead space

• may influence the triggering of

the patient; use with CPAP

• very noisy

Standard interfaces

mouthpieces

• simple and cheap

• short-interval alternative

interface for long-term

ventilated patients

Custom-made masks

• for long-term ventilation

• if standard masks are not

tolerated

Standard interfaces

Physiologic evaluation of three

different interfaces

cohort: 26 stable patients with hypercapnic COPD or interstitial lung disease.

intervention: three 30 minute tests in two ventilatory modes with

facial mask / nasal mask / nasal prongs Conclusions: NIPPV was effective with all interfaces. patients‘ tolerance: nasal mask > facial mask or nasal prongs pCO2 reduction: facial mask or nasal prongs > nasal mask

Navalesi P et al. Crit Care Med 2000;28:2139-2140

NIPPV machines

BiPAP

NIPPV machines

CPAP machine

Head straps hold the mask in place and are important for

patient comfort.

Straps attach at two to five points, depending

on the type of mask. More points of attachment add to

stability.

Head straps

OXYGENATION AND HUMIDIFICATION

Oxygen is titrated to achieve a desired oxygen saturation,

usually greater than 90% to 92%

Either by using oxygen

blenders on critical care and some bilevel ventilators or

By adjusting liter flow (up to 15 L/min) delivered via oxygen tubing connected

directly to the mask or ventilator circuit.

Bilevel ventilators

have limited oxygenation capabilities (maximal inspired oxygen fraction( %45 to

50)

so ventilators with oxygen blenders should be used for patients with hypoxemic

respiratory failure.

A heated humidifier should be used to prevent drying of the nasal passage and

oropharynx when the duration of application is anticipated to be more than a

few hours.

MONITORING

Once noninvasive ventilation is initiated, patients should be

closely monitored in a critical care unit or a step-down unit

until they are sufficiently stable to be moved to a regular

medical floor.

The aim of monitoring is

Relief of symptoms, reduced work of breathing, improved or stable

gas exchange, good patient-ventilator synchrony, and patient comfort

A drop in the respiratory rate with improved oxygen saturation or

improving pH with a lower PaCO2, reduce heart rate, within the first

1 to 2 hours portends a successful outcome.

The absence of these propitious signs indicates a poor response to

noninvasive ventilation

MONITORING OF PATIENTS RECEIVING

NON-INVASIVE VENTILATION IN ACUTE CARE SETTINGS

Location Critical care or step-down unit

Medical or surgical ward if able to breathe unassisted for >20-30 min

"Eyeball“ test

Dyspnea

Comfort (mask, air pressure)

Anxiety

Asynchrony

Leaks

Vital signs Respiratory and heart rates

Blood pressure

Continuous electrocardiography

Gas exchange

Continuous oximetry

Arterial blood gases (baseline after 2 h ,and as clinically indicated)

ADVERSE EFFECTS AND COMPLICATIONS in NIV

The mask, Discomfort and erythema or skin ulcers.

Airflow or pressure,

Conjunctival irritation. Ear pain. nasal or oral dryness .

Nasal congestion and discharge. Gastric insufflation.

Patient-ventilator asynchrony Caused by high airflow is usually indicative of air leaking

through the mouth.

How do I set the ventilator?

• Bilevel device

– IPAP

–EPAP

–Back up rate

• Adjust according to response /

comfort

• Try to improve SaO2 by IPAP

First hour……..

*Titrate settings and FiO2.

*Aim to reduce work of breathing /RR.

*Assist patient comfort and tolerate mask.

*Minimal sedation may be used.

*Monitor mental status.

*Intubate if worsening.

*KEEP PATIENT NPO!

*Check ABGs in 1-2 hours.

Monitoring

NIV monitoring:

- Evaluate the achievement of objectives

(NIV success and quality control)

- Modify the settings if necessary

Efficacy

Comfort Compliance

NIV

success

How can I monitor a patient with

domiciliary ventilation?

1. Clinical monitoring

2. Technical monitoring

• Nocturnal oximetry

• Expiratory capnography

• Transcutaneous capnography

• Ventilator software

• Polysomnography

Weaning Algorithm

Respir Care 2004. Vol. 49 (1):72-89

NO Continue with

NPPV therapy

Does

patient meet

weaning guidelines?

Clinically stable

RR < 24

HR < 110

pH > 7.35

SpO2 >90%

on< 50%

If patient status does

not improved consider

intubation

NO

YES

Restart NPPV at

previous settings

YES

Trial off NPPV with

supplemental

oxygen

Slowly titrate IPAP

downward in decrements

of 2-3 cm H2O

Does

patient demonstrate

clinical evidence

of respiratory

distress?

Discontinue NPPV and place on

supplemental oxygen

NIV Failure: Decide Early

Worsening Encephalopathy or Agitation

Inability to Clear Secretion

Inability to Accept Any Interface

Hemodynamic Instability

Worsening Oxygenation

Progressive Hypercapnia, pH <7.20

Persistent tachypnea /tachycardia

Troubleshooting

pCO2 remained high:

Exclude inappropriately high FiO2

Check mask + circuit for leaks

Check Patient Ventilator Asynchrony Patient

Check expiration valve patent

Increase IPAP

Increase FiO2/EPAP pO2 remained low:

Clinical Deterioration: Consider complications Optimize medical therapy Consider intubation

Gastric distension: Simethicone /Reduce IPAP. Irritation or ulceration of nasal bridge:

Adjust strap tension, Try cushion dressing, Change mask type.

Dry nose or mouth: Add humidifier

Check for leaks.

Dry sore eyes:Check mask fit

Nasal congestion: Decongestants Hypotension: Reduce IPAP

Troubleshooting

Use of Nasogastric Tubes

Use of nasogastric tubes to take air from

the stomach is controversial

The tube increases leaking around the

mask

The tube itself blocks a nasal passage

Compression of tube against the skin by

the mask may increase risk of skin

breakdown

Criteria for Termination of

NPPV for Invasive Ventilation Worsening pH and PaCO2

Tachynpnea (> 30 breaths/min)

Hemodynamic instability

SpO2 < 90%

Decreased level of consciousness

Inability to clear secretions

And inability to tolerate interfaces

Noninvasive ventilation as a weaning strategy for mechanical ventilation in

adults with respiratory failure: a Cochrane systematic review

Karen E.A. Burns MD MSc, Maureen O. Meade MD MSc, Azra Premji MSc RRT,

Neill K.J. Adhikari MDCM MSc

CMAJ 2014. DOI:10.1503

Noninvasive weaning reduces rates of death and pneumonia without increasing

the risk of weaning failure or reintubation.In subgroup analyses, mortality benefits were significantly greater in patients with COPD.

niv weaning

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