Oxygen Therapy

Introduction to Oxygen Therapy

Oxygen therapy is a critical intervention in medical care, used to treat hypoxaemia (low blood oxygen levels). Oxygen is delivered from wall taps at 100% concentration and is administered to patients using various devices that adjust the concentration and flow rate of inspired oxygen.

• Oxygen Concentration: The percentage of oxygen a patient receives depends on the flow rate and the delivery device.

• Flow Rate: Adjustable from 0–15 L/min at the wall tap.

• Prescription: Oxygen is a prescription-only medicine (POM) and must be prescribed with a target saturation range.

• Indication: Oxygen treats hypoxaemia, not breathlessness in non-hypoxaemic patients.

Assessment and Monitoring

Oxygen therapy should be guided by regular assessment and monitoring of oxygen saturation using pulse oximetry, which is considered the 'fifth vital sign' alongside pulse, blood pressure, temperature, and respiratory rate.

• Pulse Oximetry: Essential for all breathless and acutely ill patients; results should be recorded with the inspired oxygen concentration.

• Target Saturation: Most acutely ill patients: 94–98%. Patients at risk of hypercapnic respiratory failure: 88–92% or patient-specific range.

• Clinical Assessment: Required if saturation falls by ≥3% or below the target range.

• Early Warning Scores: Use systems like NEWS for ongoing assessment outside critical care areas.

Oxygen Delivery Devices

Different devices are used to deliver oxygen, each with specific indications, flow rates, and oxygen concentrations.

Nasal Cannula

• Oxygen Delivery: 24–30% O2

• Flow Rate: 1–4 L/min (2 L/min is most comfortable; >4 L/min may dry the nose)

• Indication: Non-acute or mildly hypoxic patients

Simple Face Mask (Hudson Mask)

• Oxygen Delivery: 30–40% O2

• Flow Rate: 5–10 L/min

• Indication: Mild to moderate hypoxia

• Limitations: Less precise FiO2 control; aspiration risk if vomiting occurs

Venturi Mask

Venturi masks deliver precise oxygen concentrations and are especially important in patients with COPD to avoid over-oxygenation.

• Oxygen Delivery: 24–60% O2 (depending on valve color)

• Flow Rate: Varies by color (e.g., Blue: 2–4 L/min = 24%, White: 4–6 L/min = 28%, Yellow: 8–10 L/min = 35%, Red: 10–12 L/min = 40%, Green: 12–15 L/min = 60%)

Non-Rebreather Mask

• Oxygen Delivery: 85–90% O2

• Flow Rate: 15 L/min

• Indication: Acutely unwell patients requiring high concentrations of oxygen

• Precaution: Do not maintain 15 L/min for prolonged periods; avoid saturations of 100%

Humidified Oxygen

• Purpose: Prevents drying of mucous membranes and airway damage

• Mechanism: Oxygen is passed through a humidifying device to produce sterile vapor

• Issues: Water can pool in tubing, potentially obstructing flow

Non-Invasive Ventilation (CPAP/BiPAP)

• CPAP: Continuous positive airway pressure; used in acute pulmonary oedema and sleep apnoea

• BiPAP: Bilevel positive airway pressure; used in COPD exacerbations

Invasive Ventilation

• Oxygen Delivery: Up to 100% O2

• Indication: Intensive care and surgical settings

• Mechanism: Artificial airway with ventilation bag or machine

Oxygen Administration and Monitoring

• Oxygen should be administered by trained staff using appropriate devices and flow rates.

• Oxygen saturation and delivery system (including flow rate) must be recorded on the patient's chart.

• Adjustments should be made to maintain target saturation; prompt assessment is needed if saturation falls.

• Oxygen should be weaned and discontinued when the patient can maintain target saturation on room air, but the prescription should remain in case of deterioration.

Airway Management

Introduction to Airway Management

Airway management is essential for ensuring adequate ventilation and oxygenation in patients with compromised airways. It involves recognizing airway obstruction, performing simple maneuvers, and using adjuncts to maintain patency.

Causes of Airway Obstruction

• Tongue: Most common cause in unconscious patients (relaxes and falls back)

• Foreign bodies: Vomit, blood, secretions, or external objects

• Swelling: Allergic reactions, trauma, or infection

Identifying Airway Compromise

• Conscious Patient: Look for signs such as stridor, use of accessory muscles, inability to speak, or cyanosis.

• Unconscious Patient: Assess for absent or abnormal breathing, snoring, or gurgling sounds.

Simple Airway Manoeuvres

Basic techniques can relieve airway obstruction caused by the tongue or soft tissues.

• Head Tilt, Chin Lift: Tilts the head back and lifts the chin to open the airway.

• Jaw Thrust: Used if cervical spine injury is suspected; lifts the jaw forward without moving the neck.

• Suction: Removes secretions, vomit, or blood from the airway.

Simple Airway Adjuncts

• Nasopharyngeal Airway (NPA): Soft tube inserted through the nostril to maintain airway patency. Size is marked on the tube (6 mm for women, 7 mm for men). Lubricate before insertion and aim towards the occiput.

• Oropharyngeal Airway (OPA): Curved device inserted into the mouth to prevent the tongue from obstructing the airway. Measure from incisors to the angle of the jaw; insert upside down and rotate 180° behind the tongue.

Advanced Airway Devices

• I-gel: Supraglottic airway device inserted into the mouth, gliding along the hard palate until resistance is felt. Used when basic maneuvers and adjuncts are insufficient.

Summary Table: Oxygen Delivery Devices