NON INVASIVE VENTILATION (NIV)

Khairunnisa binti Azman

Anaesthesiology department TGH

• A method of providing ventilatory support without needing tracheal intubation

• PPV delivered through a noninvasive interface

• Delivery of ventilatory support via the patient’s upper airway using a mask or similar device & include both continuous positive airway pressure (CPAP) & non invasive positive pressure ventilation (NPPV)

• Initially used to treat type 2 respiratory failure & prevent need of MV & Assc complication.

Proposed benefits include:

• Avoid complications of intubation & mechanical ventilation

– Reduce risk of VAP

• Improve clinical outcomes:

– Reduce mortality & morbidity

– Reduce ICU & Hospital stay

– Reduce cost

ADVANTAGES DISADVANTAGES

• Preservation of airway defence mechanism

• Early ventilatory support • Intermittent ventilation • Patient can eat, drink &

communicate • Ease of application & removal • Patient can cooperate with

physiotherapy • Improve patient comfort • Reduced sedation

requirements • Avoidance of CX of intubation

• Mask is uncomfortable/ Claustrophobic

• Time consuming for medical & nursing staff

>Slower correction of gas exchange abnormalities • Airway is not protected • No direct access to

bronchial tree for suction. • Eye irritation

Respiratory Mechanics:

• Respiratory effort required for inspiration needs to overcome:

– Elastic work (Stretch)

– Flow resistance work (Airway obstruction)

• Respiratory failure

– Forces opposing inspiration exceed respiratory muscle effort

Mechanisms of action:

• Improvement in pulmonary mechanics & oxygenation

Augments alveolar ventilation & allows oxygenation without raising the PaCO2, reverse respiratory acidosis & hypercarbia

Recruits alveoli & increases FRC to reverse hypoxia

Requirements for successful non invasive support:

• A co-operative patient who can control their airway and secretions with an adequate cough reflex.

• The patient should be able to co-ordinate breathing with the ventilator and breathe unaided for several minutes.

• Haemodynamically stable

• Blood pH>7.1 and PaCO2 <92 mmHg

• The patient should ideally show improvement in gas exchange, heart rate and respiratory rate within first two hours.

Patient Selection

Strong evidence:

• AECOPD

– Complicated by hypercapnic acidosis

• Acute cardiogenic Pulmonary oedema

• Post operative

• Facilitates extubation (weaning)

– Prevent post extubation respiratory failure (those with COPD & compensatory hypoxaemia during SBT)

INDICATIONS BEDSIDE OBSERVATIONS GAS EXCHANGE

• ↑Dypsnoea – Mild to Moderate

• Tachypnoea: > 24bpm in obstructive > 30bpm in restrictive • Signs of increase work of

breathing, accessory muscle use & abdominal paradox

• Acute OR Acute on chronic ventilatory failure (Best indication)

- PaCO2 > 50mmHg - Ph <7.15 • Hypoxaemia (used with

caution) - PF Ratio <200 (PaO2<60mmHg despite high FIO2

INDICATIONS

• Acute respiratory failure • Hypercapnic acute respiratory failure • Acute exacerbation of COPD • Post extubation difficulty/Weaning difficulties • Post surgical respiratory failure • Thoracic wall deformities • Acute respiratory failure in obesity hypoventilation

syndrome • Chronic Respiratory Failure • Patients 'not for intubation

CONTRAINDICATIONS

ABSOLUTE RELATIVE

• Respiratory arrest/unstable cardiorespiratory status

• Unable to protect airway- impaired swallowing and cough

• Facial/oesophageal • Craniofacial trauma/burns • Anatomic lesions of upper

airway

• Extreme anxiety • Uncooperative patient • Morbid obesity • Copious secretions • Swallowing impairment • Multiple organ failure • Need for continuous or nearly

continuous ventilatory assistance

INTERFACE ADVANTAGES DISADVANTAGES

Nasal - Less claustrophobic - Easy to fit - More comfortable - Permit speech/cough

• Must be able to nose breathe, keep mouth shut most of the time

• Not for ventilators without leak compensation

Face (Oronasal)

- Permits mouth breathing

- Suitable for moderately cooperative patient

Visor (Full Face)

- Avoid pressure on the nasal bridge

- Increased deadspace - Not for claustrauphobic

Helmet - Avoid pressure on face - Suitable for moderately

cooperative patient

- Large leak may interfere with triggering

- Not for claustrophobic

NIV in COPD

• Significantly reduce mortality & Cx compared to standard medical therapy

• First line therapy

• Growing evidence that maybe applicable to patient with:

– Severe acidaemia (Ph<7.25)

– Hypercarbic Coma

*cond previously considered contraindication to NIV

NIV in Morbid Obesity:

• Assc with certain respiratory syndromes

– Obstructive sleep apnoea

– Chronic alveolar hypoventilation

• Type 2 respiratory failure

– If presenting in early stage, NIV initial treatment of choice

• Post operative period

NIV in Asthma:

• Controversial

• Trial of NIV in acute asthma should only be carried out in CRITICAL CARE areas.

NIV in Neuromuscular disorder

Acute (GBS/Acute myasthenia):

• Often a/w upper airway dysfunction may increased incidence of pulmonary aspiration

• Respiratory compromised d/t GBS often a/w prolonged MV

– Recommended for early tracheostomy

NIV in Neuromuscular disorder

Chronic (MND):

• Characterized by an irreversible decline in respiratory function d/t respiratory muscle atrophy

• Use of NIV:

– Improve quality of life

– Improve survival in patient with advanced ND/MND (NICE/AAN)

NIV in Cardiogenic Pulmonary Oedema:

• Reduction in both preload & afterload and improved oxygenation and reduced work of breathing

NIV in Pneumonia:

• Controversial

• Pneumonia in underlying COPD or Immunocompromise mortality benefit

• Trial of NIV Should be done in CRITICAL CARE areas.

NIV in Lung Contusion/Chest Trauma:

• Respiratory failure d/t chest trauma or contusion responds well to NIV

• Combine with effective analgesic regime:

– Favourable outcome

– Reduce mortality & infective complications related to MV

Post Extubation use of NIV

Post extubation in critical care:

- As a preventive measures in patient who have been extubated but high risk of developing post-ext respiratory failure

- Reduce need for re-intubation & mortality in selected patient

Weaning from MV:

- Use in patient with difficult weaning from MV, aim to reduce risk a/w prolonged tracheal intubation

- To help wean patient not suitable for extubation from MV by providing respi support w/o need of sedation/NMB/Tracheal intubation

Postoperative patient

*After abdominal surgery:

- Basal atelactasis

- Prolonged supine position

- Diagpragmatic splinting

(Contribute to Post OP respi failure)

* Post OP prophylactic CPAP

Which Mode??

• Hypoxaemia CPAP

• hyPERcapnia & hypoxaemia BiPAP

CPAP (Continuous Positive Airway Pressure)

• Constant positive airway pressure throughout cycle.

• Increases FRC & opens collapsed alveoli Improves oxygenation

• ↓ work of breathing by alveolar recruitment – ↓ elastic work

– Unload respiratory muscles

• Reduces left ventricular transmural pressure (↓intrapulmonary shunt) Increases cardiac output Effective for treatment of Pulmonary oedema

• PS limited to 5-12cm H20 – Why? Higher pressure tends to result in gastric

distension requiring continual aspiration from Ryles tube

BiPAP (Bi-Level Pressure Support):

• Combination of IPAP & EPAP – Inspiratory PAP Pressure support

– Expiratory PAP CPAP

• EPAP: – Provides PEEP

– Increases FRC

• IPAP: – ↓ Work of breathing & O2 demand

– ↑ TV

– ↓ RR

Monitoring Response

Physiological - Continuous Oximetry - Exhaled TV - ABG; Initial, 2-6hrs

Objective - RR - Chest wall movement - Coordination of respiratory effort with

NIV - HR & BP - Mental state

Subjective - Dypsnoea - Comfort

Persistent Respiratory acidosis?

• Large mask/Circuit leak?

• Expiratory valve wrongly fitted

• Re- breathing?

– Single limb circuit ventilator

– Expiratory pressure is maintained by expiratory flow & set low

• Failing to synchronized with ventilator

Predictors of failure

Hypercapnic Acute respiratory failure (Ph<7.30)

Hypoxaemic Acute respiratory failure (P/F<200, not COPD

- No increased pH by 1-2 hrs - No ↓ RR by 1-2 hrs - Lack of cooperation

- Minimal ↑ PF by 1-2hr - Age >40 - ARDS - CAP/Sepsis - Multiorgan failure

Criteria for teminating NIV & switching to mechanical ventilation

• Worsening Ph & PCO2

• Tachypnoea

• Hemodynamic instability

• Spo2 < 90%

• Decreased level of conciousness

• Inability to clear secretion

• Inability to tolerate NIV

CONCLUSIONS

Key factors in success: • Careful patient selection/rejection • Skilled initiation & application • Algorithmic approach in initiation, use &

discontinuation • Patient comfort • Avoid dyssynchrony • Avoiding complication Most importantly decision making on when to switch to invasive mechanical ventilation

THANK YOU

References:

1. Non Invasive Ventilation, http://www.frca.co.uk/article

2. Non invasive ventilation in ICU, http://www.frca.co.uk/article.aspx?articleid=100753

3. Clinical application of NIV in critical care, CEACCP