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
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