NON INVASIVE VENTILATION

Noninvasive ventilation is the delivery of alveolar ventilation without the need for an invasive artificial airway.

Types of NIV•Negative pressure ventilation(Iron tank, Chest cuirass)

•Abdominal Displacement (Pneumobelt-Rocking bed)

•Positive pressure ventilation (BIPAP, CPAP, NIPPV)

A) Negative pressure ventilation

(Iron tank, Chest cuirass)

B)Abdominal Displacement

C)Non Invasive Positive pressure ventilation

Advantages of NIV/ NIPPV1) Noninvasiveness Avoids the complications of endotracheal intubation - Early (local trauma, aspiration)- Late (injury to the the hypopharynx, larynx, and

trachea, nosocomial infections)2 ) Ease of application (compared with endotracheal intubation) - Easy to implement - Easy to remove

3) Allows intermittent application 4) Can be used in non ICU settings5) Improves patient comfort6) Reduces the need for sedation 7) Oral patency (preserves speech, swallowing, and cough)8) Avoid the resistive work imposed by the endotracheal tube

Disadvantages of NIV1.System – Slower correction of gas exchange abnormalities– Increased initial time commitment, may need intubation– Gastric distension (occurs in <2% patients)– Time consuming, manpower consuming

2.Mask -Air leakage - Transient hypoxemia from accidental removal -Eye irritation - Facial skin necrosis –most common complication.

3.Lack of airway access and protection - Suctioning of secretions

Location of NIVNIV can be administered in the-Emergency department-ICU-HDU-General ward -Home

Who can administer NIV?- Physicians-Nurses-Respiratory care therapists

Assembly of NIV system

A

B

a) Ventilator unit

1) CPAP 3) Bilevel NIV2) BIPAP 4) Conventional ICU ventilator

Modes of NIPPV Pressure preset mode- (most commonly used)The delivered volume is variable depending on lung compliance .- Compensates better in case of air leak- Limitation of peak airway pressure possible (ie reduction in TV / Insp. flow rate) , hence better in pts. with previous emphysematous bullae/ pneumothoraces.- Comfortable and better tolerated

Volume preset mode- The set volume is delivered with variable peak airway pressures

Pressure preset mode • CPAP(Continous Positive Airway Pressure)Only one level of positive pressure set above

atmospheric pressure during entire spontaenous breath, does not include any mech. breath

If IPPV settings are set as IPAP= EPAP, then it acts like CPAP

• IPPV(Intermittent Positive Pressure Ventilation)Two level of pressure is set –a)IPAP (Inspiratory positive airway pressure)b)EPAP (Expiratory positive airway pressure)

IPAP (Inspiratory positive airway pressure)•Controls peak insp. pressure •Directly proportional to degree of ventilation(tidal volume, minute ventilation) IPAP = PS + PEEP/ EPAP

EPAP (Expiratory positive airway pressure)•Same as PEEP in Mech. Ventilation•Improves oxygenation by ↑ FRC

EPAP = PEEP

Combination of above is also referred as BiPAP (Bilevel Positive Airway Pressure) sometimes but actually it is the trademark of the company RESPIRONICS which designed and marketed such BiPAP machines which were cheaper and portable than the routine ventilators.

The IPPV by BiPAP machine and ventilators with NIV modes differ in following ways

A) Delivered Fio2 –• BiPAP machine lack oxygen blender and Fio2

has to be adjusted by adjusting O2 flow rate.• Fi02 diretly proportional to O2 flow inversely to the set IPAP(more the IPAP , more the driving pressure, more

the admixture of air with O2)• This is not the case with ventilator with NIV

mode.

b) Pressures- •The maximum pressure achievable on BiPAP machine is less than conventional ventilator.•EPAP in BiPAP is achieved by adjusting flow of air•PEEP in ventilators is achieved by a device in expiratory circuit.•The expiratory port in BiPAP is smaller than Ventilator circuit, which can lead to transient rise of peak airway pressure above set IPAP as patient changes to expiration

c) Safety alarms- Lesser with BiPAP machine.

d) Leak compensation – •BiPAP•Ventilators with NIV mode can compensate for the leak due to face mask by increasing the flow to achieve the set IPAP.Not possible with the conventional ventilators without NIV where either face mask has to be tight to prevent leak or have to tolerate frequent alarms.

b) Interface Nasal mask

Oronasal / Facial Mask

Nasal pillows/ cushions

Helmets

Mouth pieces

Scenarios in which NIV can be used

CAT I- life support without preset limitsCAT II – life support with preset limits (DNI )CAT III – comfort care

Indications I) Acute respiratory failure a) Hypercapnic acute respiratory failure •Acute exacerbation of COPD •Post extubation NIV•Post surgical respiratory failure •Thoracic wall deformities /Neuromuscular diseases•Status asthmaticus •Acute respiratory failure in OSAHS

b) Hypoxemic acute respiratory failure •Cardiogenic pulmonary edema •Community acquired pneumonia •Post traumatic respiratory failure •ARDS

II) Chronic Respiratory FailureIII) Immunocompromised PatientsIV) Weaning difficultiesIV) Do Not Intubate Patients

Scenarios where strong evidence exists on use of NIV•COPD1)To avoid intubation2)To extubate to NIV (i.e facilitate extubation)

•OSAHS (esp CPAP)

•Acute cardiogenic pulmonary edema

•Immunocompromised/ Hematologic patients

Criteria for NIV- GOLD 2005

Contraindications Absolute •Comatose•Cardiorespiratory arrest•Upper airway obstn•Airway secretions•Ileus, UGIB, vomitting•MODS•Facial surgery, trauma

Relative •Confused, disoriented•Hemodynamic instability•ACS•Recent gastric surgery

1. Do a baseline arterial blood gas

2. Discuss and explain the patient, discuss with the family too.

3. Patient in bed or chair at >30 angle

4. Select interface of proper size for patient + Select ventilator ( BiPAP or NIV through ventilator)

5. Apply headgear. Hold or allow the patient to hold the mask gently to the face until the patient is comfortable with it. Encourage the patient to use proper breathing technique. Avoid excessive strap tension (one or two fingers under strap)

6. Connect interface to ventilator tubing and turn on ventilator

7. Start with low pressure in spontaneously triggered mode with backup rate; pressure limited: 8 to 12 cm H2O inspiratory pressure; 3 to 5 cm H2O expiratory pressure

Steps in initiation of NIV

8. Gradually increase inspiratory pressure (10 to 20 cm H2O) as tolerated to achieve alleviation of dyspnea, decreased respiratory rate, increased tidal volume (if being monitored), and good patient-ventilator synchrony

9. Provide O2 supplementation as need to keep O2 sat >90 percent

10. Check for air leaks, readjust straps as needed. Add humidifier as indicated

11.Consider mild sedation (eg, intravenously administered lorazepam 0.5 mg) in agitated patients

12. Encouragement, reassurance, and frequent checks and adjustments as needed

13. Monitor occasional blood gases (within 1 to 2 hours) and then as needed

14. Monitor the respiratory rate, heart rate,level of dyspnea, O2 saturation , minute ventilation,and exhaled tidal volume.

Initial settingsIPAP -15, EPAP – 5 (on BiPAP)PS -10, PEEP- 5 (on NIV ventilator)

Back up rate - 8-12 breaths/min

For optimal ventilation- ↑ IPAP/ PS in increments of 2To adjust for inadequate oxygenation- ↑ EPAP/ PEEP in increments of 2Adjust oxygen flow rate/ FiO2

What to expect ?•Relief of dyspnea•Reduced work of breatn•Acceptable oxygenation without unacceptable hypercapnea•Improved respiratory acidosis

What not to ? •Major improvement in PaCo2 in short term•Major improvement in clinical parameters

Scenario Goal Hypoxemic ARF • Ensure an adequate Pao2 until the

underlying problem can be reversed

COPD, asthma • Reduce co2 by unloading the respiratory muscles and

• Augmenting alveolar ventilation

Cardiogenic pulmonary edema

• Improve oxygenation, • Reduce work of breathing, and • Increase cardiac output

OSA • Limit sleep- and position-induced changes in oxygenation

• Co2 elimination • Increasing lung volume and • Augmenting alveolar ventilation

Predictors of success

Trouble shooting Corrective action

Low PaO2 • ↑ EPAP/ PEEP • Adjust oxygen flow rate/ FiO2• Increase inspiratory time

High PaCO2 • ↑ IPAP/ PS • ↑ Back up RR• Check for leaks• Reduce oxygenation in COPD• Increase time on IPPV than

plain mask• Make sure EPAP > 4

Low PaCo2 • ↓ IPAP• ↓ Back up RR

Altered sensorium (↓PO2, ↑PCO2, REM sleep)

Adjust IPAP, EPAP, Back up RR

Trouble shooting Corrective action

Asynchrony • Change settings• Change machine• Change the interface-Mouth breathing in nasal maskLeaks due to inapropriate size• Mild sedation/ reinforcement

High inflation pressure • Identify Atelectasis, bronchospasmPneumothorax, pulmonary

edema, consolidation, mucus plug

Cough , rhinitis, epistaxis • Humidifiers• Bronchodilators• antibiotics

Criteria to discontinue NIV and intubate

• Inability to tolerate the mask because of discomfort or pain

• Inability to improve gas exchange or dyspnea• Need for endotracheal intubation to manage

secretions or protect airway• Hemodynamic instability• ECG – ischemia/arrhythmia• Failure to improve mental status in those with CO2

narcosis.

Failure – 5-40% (Average – 20 %)

Early ( < 48 Hrs) •Patient compliance •Technical issues(if non improvement of pH and RR within 2 hrs- Consider intubation )

Late ( >48 Hrs) •Added medical complications

NIV in specific situations

NIV in COPD (success rate 80-85%)•Staff expertise important than location of use•Reduces the need of endotracheal intubation•Significantly improves paco2, pao2, pH•Reduced VAP, Pneumothorax•No consistent reduction in mortality and hospital stay.•Significant increase in nursing workload

• No difference in outcome of pressure vs volume preset modes

• But pressure preset mode better tolerated

• BiPAP is first mode of choice• CPAP to be used if BiPAP not available, as

the degree of unloading of respiratory work with former is better.

NIV in Cardiogenic pulmonary edema• CPAP reduces venous return and can lower left

ventricular preload .

• Even with very poor left ventricular function & active ischemia, the stroke volume and ejection fraction can improve with CPAP, leading to a rapid decrease in heart rate without undue hypotension.

• Sufficently high level evidence to favor the use of CPAP

• There is insufficient evidence to recommend the use of BiPAP/ NIPPV probably the exception being patients with hypercapnic CPE.

• Some have even reported evidence of ongoing myocardial ischemia with BiPAP

• No effect in short term mortality• Reduction in rate of intubation, metabolic

disturbances, long term mortality (45%)• CPAP should be mode of choice• BiPAP/ Bilevel pressure NIMV - if hypercapnic CPE or if CPAP results in inadequate

relief of symptoms.

NIV in OSAHSHome CPAP at night time is the first line therapy•Reduced apnea, hypoapneas•Better nocturnal oxygenation•Better quality of life, mood, cognition and vigilance

NIV in Hematological Malignancies• Early use of CPAP reduces ALI requiring invasive

ventilation (even without secure diagnosis of infection),

• Reduced ICU mortality• But same hospital mortality

In Community acquired Pneumonia• Reasonable first line t/t. • Reduced intubation rate• No overall mortality benefit as c/t O2 therapy

In acute severe asthma

• May consider, no trial available so far with conventional ventilation

In Cystic fibrosis/ bronchiectasis• Useful in hypercapniec , acidotic patients

Post extubation• Reduced risk of respiratory failure, 90 day

mortality

In Chest trauma

• CPAP as first line in flail chest, hypoxemic patients post trauma.

• Patients on BiPAP to be monitored for Pneumothorax

In NMD • CPAP should be tried first.• Containdicated in extreme bulbar weakness