NON-INVASIVE VENTILATION

Objectives:

• Definitions• Advantages and Disadvantages• Indications• Contraindications• Modes

Non-invasive ventilation

“The delivery of mechanical ventilation to the lungsusing techniques that do not require endotracheal intubation”

Background

• Initially used in the treatment of hypoventilation with Neuromuscular Disease

• Now accepted modality in treatment of acute respiratory failure

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

Respiratory failure

Failure to maintain adequate gas exchange

• Hypoxic ( Type 1) orHypercapnic /Hypoxic (Type 2)

• Acute /Chronic / Acute on Chronic

Effects of NIV

• Improves alveolar ventilation to reverse respiratory acidosis and hypercarbia

• Recruits alveoli and increases FRC to reverse hypoxia

• Reduces work of breathing

Advantages

Noninvasiveness

• Application - easy to implement or remove• Improves patient comfort• Reduces the need for sedation • Oral patency

(preserves speech, swallowing, and cough)

Advantages 2

• Avoid the resistive work of ETT

• Avoids the complications of ETT– Early (local trauma, aspiration)– Late (injury to the the hypopharynx, larynx,

and trachea, nosocomial infections)

• Reduced Cost and Length of Stay

Disadvantages

1.System

Slower correction of gas exchange abnormalitiesGastric distension (occurs in <2% patients)

2.Mask

Air leakageEye irritationFacial skin necrosis (most common complication)

Disadvantages

3.Lack of airway access and protection Suctioning of secretionsAspiration

4. Compliance / claustrophobia

5. Work load and supervision

Which mode?

• Hypoxaemia = CPAP

• Hypercapnia and hypoxaemia= Bi Level

CPAP

CONTINUOUS POSITIVE AIRWAY PRESSURE (AKA PEEP)

• Constant positive airway pressure throughout cycle • Improves oxygenation• Decreases work of breathing by alveolar recruitment (Dec

elastic work) and unloads insp muscles• Decreases hypoxia by alveolar recruitment and reduces

intrapulmonary shunt

Indications

• Acute pulmonary oedema

• Pneumonia

Bi-level Pressure Support

• Combination of IPAP and EPAP

Inspiratory PAP = Pressure Support

Expiratory PAP = CPAP

Respiratory Effects Bi-PAP

• EPAP – Provides PEEP– Increases Functional Residual Capacity– Reduces FiO2 required to optimise SaO2

• IPAP– Decreases work of breathing + oxygen demand– Increases spontaneous tidal volume– Decreases spontaneous respiratory rate

Indications for Bi Level

• Acute Respiratory Failure

• Chronic Airway Limitation/COPD

• Asthma?

When to use NIV/CPAP• Indication: APO, COAD• Contraindications excluded• Assessment– Sick not moribund– Able to protect airway– Conscious/cooperative– Haemodynamic stability

• Premorbid state / Ceiling of therapy?

Contraindications• Impaired consciousness, confusion, agitation• Inability to protect airway • Excessive secretions or vomiting• Haemodynamic instability

• Untreated pneumothorax• Bowel obstruction• Facial trauma, burns, recent surgery• Fixed upper airway obstruction

Complications

• Hypoxia • Pulmonary barotrauma• Reduced cardiac output• Vomiting and aspiration• Pressure areas• Gastric distension

Ventilator Settings- LVF

• CPAP at 5-8 and increase to 10-15 cm H20

• Mask is held gently on patient’s face.

• Increase the pressures until adequate Vt (7ml/kg), RR<25/min, and patient comfortable.

• Titrate FiO2 to achieve SpO2>90%.

• Keep peak pressure <25-30 cm

COAD exacerbation: NIV

• increases pH, reduces PaCO2, reduces the severity of breathlessness in first 4 h of treatment

• decreases the length of hospital stay

• mortality and intubation rates are reduced

Ventilator settings COAD

• Mode- Spontaneous/Timed

• EPAP- 4-5 cm H20 IPAP- 12- 15 cm H20

• Trigger- maximum sensitivity

• Back up rate- 15 breaths/min

• Back up I:E 1:3

Setting It Up• No contraindications• O2 \ medical therapy underway

• Explanation and reassurance• Correct mask size • Ventilator set up• Commence NIV hold mask in place• Reassure and fix mask• Monitor and observe, regular assessment

Monitoring response

Physiological a) Continuous oximetryb) Exhaled tidal volume

c) ABG- Initial, 1, 2-6 hrsObjective

a) Respiratory rateb) Chest wall movementc) Coordination of respiratory effort with NIVd) Accessory muscle usee) HR and BPf) Mental state

Subjective a) Dyspnoea b) Comfort

Documentation

• Mode of ventilation• Flow rate of oxygen, percentage of oxygen• TPR and BP• Respiratory assessment• Conscious level (GCS)

Obs - 15 minutely for first hour, then hourly if condition stable

Treatment Failure

• Deterioration in condition

• Worsening or non improving ABG

• Intolerance or failure to coordinate with machine

Treatment Failure

• Back to the patient- ABC

• Medical therapy optimised

• Treatment of complications

Criteria to discontinue NIV

• Inability to tolerate the mask

• Inability to improve gas exchange or dyspnoea

• Need for endotracheal intubation

• Hemodynamic instability

• ECG – ischaemia/arrhythmia

Withdrawal of NIV

• Clinical improvement• Aim for– RR<24– HR <110– pH>7.35– Sats >90% on <40%

Most important THPs

• Selection of patient really vital to success - need to have reversible pathology

• Aim for gradual improvement over hours with good supportive nursing

• In ED, main use is to avoid intubation / ventilation in LVF and COAD