Non-Invasive Ventilation

Arjun Srinivasan, Mahadevan & Pattabhiraman Pulmonology Associates KMCH

Agenda

Definition & mechanism of action Indications When, who, where, what & how ?

Technical aspects Weaning off NIV Complications

NONINVASIVE VENTILATION

Non-invasive ventilation (NIV) refers to a form of assisted ventilation that involves provision of ventilatory support without endotracheal intubation (ETI)

CPAP vs. NIV

CPAP Pressure greater than atm applied to proximal airway throughout resp cycle Splints airway Increases lung volume Raises intrathoracic pressures Does not offload resp muscles NIV Greater pressure applied during inspiration over and above the baseline CPAP Unloads resp muscles Can provide complete resp support

NIV – how it works

Decreasing work of breathing Off loading of resp muscles & decreasing fatigue Preventing wide swings in intrathoracic pressure Decreasing afterload to heart Preventing complications of IMV Intubation & MV Loss of airway defenses Post extubation issues

NIV

Whom to initiate ?

Acute COPD Pulmonary edema Immunocompromised patients Weaning from mechanical Neuromuscular weakness Bronchial asthma ARDS Do not intubate – pts Other indications Chronic

When to initiate ?

Appropriate diagnosis with potential reversibility Establish need for ventilatory assistance Moderate to severe respiratory distress Tachypnea Accessory muscle use or abdominal paradox Blood gas derangement pH <7.35

Paco2 >45 mm Hg Pao2/Fio2 < 200

When not to initiate

Respiratory arrest Medically unstable Unable to protect airway Excessive secretions Uncooperative or agitated Unable to fit mask Recent upper airway or gastrointestinal surgery

Clinicians

Who will initiate ?

Respiratory therapists Trained nurses

Where to initiate ?

Emergency ICUs Step-down units Wards

Which ventilator to use ?

ICU ventilator BIPAP

Critical care ventilator Vs NIV

Variables … Inspiratory Pressure … Leak Tolerance … Different Modes … Alarms … Monitoring Capability … Battery … Oxygen Blender … Compactness ICU Ventilator ++ + ++ ++ ++ + ++ + NIV ++ ++ + + + + ++

Mask interface

Pro & cons of interfaces

Ideal interface  Low dead space  Transparent  Lightweight  Easy to secure  Adequate seal with low facial pressure  Disposable or easy to clean  Non-irritating (non-allergenic) Inexpensive  Variety of sizes  Adaptable to variations in facial anatomy  Ability to be removed quickly  Anti-asphyxia mechanism  Compatible with wide range of ventilators

Vented & Non-vented masks

Depends on the type of ventilator being used 1. BIPAP

Tubings

2. Intermediate type of ventilator 3. Critical care ventilators

Modes

CPAP Bi-level - S (spontaneous) Bi-level - S/T PC Volume preset Vs Pressure preset Dual modes

How to set pressures ?

IPAP & EPAP High-low approach High inspiratory pressures (20-25 cms), rapidly titrated to ensure adequate tolerance & ventilation in the first hour Similarly EPAP is adjusted from high (10) to low levels Rapidly addresses hypoxemia Low-high approach Low initial inspiratory pressures (10-12 cms) and rapid upward titration to ensure adequate ventilation in the first hour EPAP is titrated upward from 4-5 cms Better tolerance Aim for TV ~ 6-7 ml/kg predicted body weight

Trigger

Most portable ventilators have flow triggering Pressure triggering : associated with increased work of triggering with auto PEEP (in AE of COPD) Auto PEEP significantly lower with flow triggering in PSV mode Modern ventilators allow manipulation of trigger sensitivity to allow reduction in work of breathing ST mode offers a timed back up trigger

FiO2

Most portable BIPAP machines lack O2 blender and are dependent on oxygen delivery from wall units/cylinder FiO2 delivered is not constant & is dependent on the flow rates / inspiratory pressures / site of leak port / air leak Oxygen delivered through ICU ventilators is regulated & precise due to blender.

Delivery upto FiO2 of 1 possible

Humidification

Area of intense debate with no clear consensus High flow rates over long hours tend to dry up secretions Dried up upper airway adds to discomfort Probably a good idea in cases of prolonged NIV Heated humidification is the way to go with lesser intensity than in intubated patients HME is strict no as it adds to dead space & interferes with CO2 wash out

Monitoring during NIV

Subjective and objective parameters First 2hrs - intense monitoring Next 8hrs - close monitoring … There after - routine monitoring Even if parameters were borderline at start of NIV, early change / improvement predicts success of NIV This is the most important aspect of NIV First few hours predict the outcome of the patient

Monitoring during NIV

Chest expansion Accessory muscles Synchrony at base line, 1-2hrs after, then based on response

Other settings

Tinsp Inspiratory time of backup rate in st mode Rise time Time taken for IPAP to be reached from EPAP Shorter in tachypneic patients may ensure better tolerance Ramp time Time taken to reach set EPAP/IPAP Relevant in chronic ventilation

Trouble shooting

Potential issues 1. Leak 2. Agitation / asynchrony 3. Hypoxia 4. Hypercarbia Solutions 1. Check mask fit/ strap position/ tubings / ? Chin strap 2. Talk to patient / adjust settings / sedation /analgesia 3. Adjust ventilator / FiO2/ intubate 4. Adjust ventilator / FiO2/ intubate

Potential indicators of success in NIV

… Younger age … Lower acuity of illness … Able to cooperate … Better neurologic score … Less air leak … Synchronous breathing … Intact dentition … Less secretions … Better compliance … Improvements in gas exchange and heart respiratory rates within first 2 hours

Situations where NIV is likely to fail

Hypercapnic failure Hypoxemic failure GCS < 11 RR > 35/min PH < 7.25

APACHE > 29 Asynchrony Agitation / intolerance Edentulous / excessive leak No initial improvement Diagnosis of ARDS / pneumonia Age > 40 SBP < 90 Metabolic acidosis PH < 7.25

Low PO2/ FiO2 Simplified APS II > 34 Failure of PO2 / FiO2 to improve above 175 by 1 st hour

Weaning patients from NIV

No specific protocol Pts of COPD would require at least 24 hours to stabilise NIV is usually removed as per patient’s request for feeding/facial hygiene Re – attached as deemed necessary Attempt gradual decrease in IPAP / EPAP & discontinue when patient tolerates

Complications of NIV

Failure is the most serious complication Most dreaded complication is failure to recognize NIV failure early leading to delay in intubation Studies have shown that this can lead to increased mortality especially when used in situations where NIV is used without strong evidence

Complications of NIV

Principles of mechanical ventilation. 3e

Summary & conclusions

NIV is an important tool in the hands of RT & intensivist Provides a level of respiratory support in emergency / wards unimaginable otherwise Has changed the way we manage COPD exacerbations Needs careful monitoring during initial hours A tool which needs to be used wisely for us to reap the benefits

Thank you

Questions ?