Oxygen Therapy and Non-Invasive Ventilation

Source: Oxygen Delivery and NIV Teaching — 17 slides (September 2023) Learning levels: Foundation = Band 5 | Intermediate = Band 6 | Advanced = Band 7+

1. Oxygen Therapy

1.1 Overview

Learning level: Foundation

• Oxygen is a drug — it needs to be prescribed
• Used for patients with hypoxaemia
• Long-Term Oxygen Therapy (LTOT): to be considered for patients with chronic hypoxaemia
  • Can be used throughout the day, nocturnally, or sometimes during exercise

1.2 Indications for Oxygen Therapy

Learning level: Foundation

• Acute desaturations not spontaneously resolving (e.g. secondary to mucus plugging, obstruction, sepsis)
• Hypoxaemia on blood gas (ideally arterial):
  • PaO2 < 10 kPa
  • PaO2 < 8 kPa = severe hypoxaemia
• SpO2 dipping when asleep or exercising

1.3 Respiratory Failure Types

Learning level: Foundation

2. Modes of Oxygen Delivery

Learning level: Foundation

2.1 Low-Flow Devices

2.2 Controlled Oxygen Devices

2.3 High-Flow / Emergency Devices

2.4 High-Flow Nasal Cannula (HFNC)

Learning level: Intermediate

• O2 is warmed and humidified
• Paediatric and adult setups available
• Limited flow rate for paediatric cannulae
• Delivered with a set flow rate and FiO2
• Flow usually described in terms of L/kg in paediatrics
• Usually 1-2 L/kg

3. Non-Invasive Ventilation (NIV)

3.1 Definition

Learning level: Foundation

• A non-invasive method of positive pressure delivery utilising the patient’s upper airway
• Tracheostomy ventilation counts as invasive ventilation (via an artificial airway)
• Used for patients in respiratory failure:
  • Type 1: hypoxaemia
  • Type 2: hypoxaemia and hypercapnia (ventilation failure)

3.2 Indications and Goals of Therapy

Learning level: Foundation

Goals:

• Correct gas exchange abnormalities
• Increase PaO2, decrease PaCO2 to aim for normal pH
• Improve WOB
• Provide support to the fatiguing patient — aiming to avoid intubation
• Improve alveolar minute ventilation leading to improved gaseous exchange

3.3 Contraindications

Learning level: Foundation

• Unable to maintain upper airway
• Not tolerant of interface used
• Haemoptysis
• Undrained pneumothorax
• Ceiling of care in place
• Be aware of possible complications if patient has high secretion load or recent vomiting

4. CPAP vs BiPAP

Learning level: Intermediate

Cross-reference: CPAP/PEEP is also covered in the 2019 Fundamentals deck (01-fundamentals-of-ventilation.md, Section 4.7) with more detail on the physiological effects (FRC increase, V/Q matching, reduced shunting).

4.1 CPAP Detail

Learning level: Foundation

• PEEP is set and the patient breathes on top of this
• Commonly used long term for patients with:
  • Obstructive Sleep Apnoea (OSA)
  • Malacic airways

4.2 BiPAP Detail

Learning level: Intermediate

Modes within the BiPAP umbrella:

Settings:

• Set EPAP (equivalent to PEEP)
• Set IPAP (maximum inspiratory pressure) or PS (pressure support)
• PS = IPAP - EPAP

Worked example:

If EPAP = 6 and IPAP = 14, then PS = 8

4.3 Pressure Delivery

Learning level: Foundation

• The source material includes a diagram showing pressure delivery in CPAP (single continuous pressure level) vs BiPAP (two pressure levels — IPAP during inspiration, EPAP during expiration)

4.4 Interfaces (Masks)

Learning level: Foundation

• Various mask types are available (the source material includes images of ventilators and masks used at RLH)
• Correct mask fit is essential for effective NIV delivery

5. Long-Term Ventilation (LTV)

Learning level: Intermediate

5.1 Definition and Criteria

• Some patients require ventilation long term at home
• If requiring ventilation for > 3 months, this is defined as LTV
• Sleep study completed in hospital when well, then initiated on CPAP or BiPAP
• Patients will have well and unwell ventilation summaries
• Parents trained in all care and often go home with a care package

5.2 The LTV Service at RLH

• Team consisting of: consultant, CNSs, sleep physiologists, and physiotherapist
• Initiate LTV in hospital as a planned admission
• Monitor the patient and use of ventilators at home
• Complete sleep studies
• Review in clinic

6. Summary Table: Oxygen Delivery and NIV Devices

Cross-reference: For invasive ventilation modes (SIMV, PCV, VCV, PRVC), see 01-fundamentals-of-ventilation.md. For HFOV, see 03-hfov-and-nitric-oxide.md.