9.2 Respiratory Investigations, Inhaler and Nebuliser Technique & the MRC Dyspnoea Scale

Respiratory Investigations, Inhaler and Nebuliser Technique & the MRC Dyspnoea Scale

RCSI's Respiratory reading group runs well beyond disease pathophysiology. It names inhaler technique, nebuliser therapy, incentive spirometry, bronchoscopy, accessory muscles of breathing, blood oxygen levels, the MRC Dyspnoea Scale and lung cancer - and RCSI publishes two videos under the respiratory heading on its equipment page. Respiratory also appears as a chronic disease management OSCE example (asthma and COPD) and lung cancer appears as a teaching the junior student nurse example paired with bronchoscopy.

The practical consequence: expect to be asked to teach a device or explain an investigation, not only to describe a disease.

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Grading Breathlessness: The MRC Dyspnoea Scale

The MRC Dyspnoea Scale grades functional limitation from breathlessness, which is far more useful than asking "are you short of breath?".

Its value is that it is reproducible and comparable over time. A patient who was grade 2 at their last review and is now grade 4 has deteriorated measurably, whatever their saturation reads. Grade 3 and above is a common threshold for referral to pulmonary rehabilitation.

Observing Work of Breathing

Numbers do not capture effort. Look for:

• Accessory muscle use - sternocleidomastoid, scalenes and trapezius recruited on inspiration; the abdominal muscles on forced expiration.
• Tracheal tug and intercostal or subcostal recession.
• Pursed-lip breathing, which generates positive end-expiratory pressure and splints small airways open - a useful self-management technique in COPD.
• Tripod positioning, leaning forward on the arms to fix the shoulder girdle.
• Ability to speak: full sentences, short phrases, or single words. Inability to complete a sentence is a marker of severity in acute asthma.
• Cyanosis, exhaustion, drowsiness and a silent chest - all late and ominous.

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Teaching Inhaler Technique

Poor technique is one of the commonest reasons an inhaled treatment appears to fail. Always ask the patient to demonstrate before assuming they can use the device - "do you know how to use it?" is not an assessment.

Metered-Dose Inhaler (MDI) with a Spacer

A spacer should be used wherever possible: it removes the need to coordinate actuation with inhalation, increases the proportion of drug reaching the lungs, and reduces oropharyngeal deposition.

1. Remove the cap and shake the inhaler well.
2. Insert the inhaler into the spacer.
3. Breathe out gently, away from the spacer.
4. Seal the lips around the mouthpiece.
5. Press the canister once to release one dose.
6. Breathe in slowly and deeply, then hold the breath for about 10 seconds, or breathe normally through the spacer for several breaths (tidal breathing) if a deep breath is not possible.
7. Wait about 30 seconds before a second dose, and shake again between doses.
8. Rinse the mouth with water and spit out if the inhaler contains a corticosteroid.

Spacers are washed in warm soapy water, left to air-dry without rinsing or towel-drying - drying with a cloth generates static that attracts drug to the chamber wall - and replaced periodically.

Dry Powder Inhaler (DPI)

Dry powder devices are breath-actuated and need a different technique from an MDI:

1. Load the dose exactly as that device requires.
2. Breathe out gently away from the device - never into it, because exhaled moisture clumps the powder.
3. Seal the lips and breathe in quickly and deeply (the opposite of the slow inhalation used with an MDI).
4. Hold the breath for about 10 seconds.
5. Rinse the mouth if the device contains a corticosteroid.
6. Do not use a spacer with a DPI.

The Errors to Look For

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Nebuliser Therapy

A nebuliser converts a liquid drug into an aerosol for inhalation over several minutes. Standard nursing practice:

• Check the prescription, the drug, the dose, the diluent, the route and the expiry, and the patient's allergy status and identity.
• Sit the patient upright.
• Assemble the chamber, add the prescribed solution, attach the mask or mouthpiece, and set the driving gas flow to the rate that produces a visible mist (commonly around 6-8 L/min).
• Stay with the patient initially; monitor for tremor, tachycardia and palpitations with beta-2 agonists.
• Record the observations before and after, and the effect on breathlessness and peak flow where relevant.
• Clean or dispose of the equipment per local policy - a shared, poorly cleaned chamber is an infection route.

The Driving Gas Question

In an acute exacerbation of COPD in a patient at risk of hypercapnic respiratory failure, nebulisers should be driven by compressed medical air, not oxygen. If the patient needs oxygen, it is given concurrently by nasal cannulae at 1-2 L/min underneath the nebuliser mask, titrated to the prescribed target of 88-92%.

Driving a 6-8 L/min nebuliser with oxygen delivers a high inspired oxygen concentration for the duration of the treatment and can precipitate hypercapnia. In acute asthma, by contrast, hypoxaemia is the immediate threat and oxygen-driven nebulisation is appropriate.

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Incentive Spirometry

An incentive spirometer is a simple device that encourages slow, deep, sustained inspiration. It is used mainly after thoracic or upper abdominal surgery and in patients at risk of atelectasis, where pain and immobility cause shallow breathing and basal collapse.

Teaching points:

• Sit the patient upright, ideally on the edge of the bed or in a chair.
• Ensure analgesia is effective first - a patient splinting a painful abdominal wound cannot take a deep breath, and the intervention will fail.
• Exhale normally, seal the lips around the mouthpiece, then breathe in slowly and deeply to raise the indicator and hold for 3-5 seconds.
• Remove the mouthpiece, breathe out normally, rest briefly, and repeat as prescribed - commonly around 10 breaths every hour while awake.
• Encourage supported coughing afterwards, with a pillow or folded towel braced against the wound.
• Record the volumes achieved to show progress.

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Bronchoscopy

Bronchoscopy allows direct visualisation of the airways and sampling by washings, brushings or biopsy. RCSI pairs it with lung cancer as a teaching-station example, so be able to explain it in plain language.

The single point most often missed is the return of the gag reflex before anything is swallowed - the throat has been anaesthetised, and a patient who drinks too soon can aspirate without coughing.

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Lung Cancer: The Nursing Frame

You are unlikely to be asked to stage a tumour, but you may be asked to explain an investigation, recognise red flags, or teach a student.

Red-flag symptoms prompting urgent referral: a cough persisting more than three weeks, haemoptysis, unexplained weight loss, persistent chest or shoulder pain, hoarseness, recurrent chest infections, finger clubbing, and breathlessness or fatigue that is new and unexplained.

Nursing priorities: breathlessness management (positioning, pacing, fans, breathing techniques), pain assessment and multimodal analgesia, nutrition and MUST screening, smoking cessation support offered without judgment, honest and compassionate communication, and early involvement of palliative care alongside active treatment rather than only at the end of life. Signpost patients to Irish Cancer Society supports and the lung cancer clinical nurse specialist.