Non-Invasive Ventilation (NIV): Your Guide to Using NIV in A&E

You’re on a busy shift in A&E. A 65-year-old man is brought in by ambulance. He’s struggling to breathe, and the paramedics tell you it started suddenly about two hours ago.

Clinically, he looks unwell and is using all his accessory muscles to breathe. His oxygen saturation is 85% on a non-rebreather mask with the oxygen running at 15 L/min. When you speak to him, he opens his eyes but his responses are confused and broken up by gasps for air.

Is this acute pulmonary oedema? A severe COPD exacerbation? Whatever the cause, he is in acute respiratory failure, and you need to act fast.

Not so long ago, the next step would have been a call to the anaesthetics team for immediate intubation and transfer to ITU. There was little available between simple oxygen therapy and invasive ventilation. Thankfully, we now have an effective intermediate option: non-invasive ventilation (NIV).

Let's break down how you can use this life-saving intervention with confidence.

What Exactly Is Non-Invasive Ventilation?

Non-invasive ventilation (NIV) is a way of supporting a patient's breathing using positive pressure delivered through a snug-fitting face mask connected to a ventilator. The key is in the name: it's non-invasive. No endotracheal tube, no sedation, and no need for a definitive airway.

A standard non-rebreather mask is great for increasing the concentration of oxygen (FiO2) a patient inhales, but that's all it does. It's a passive therapy that doesn't help with the physical effort of breathing.

NIV is an active therapy. It doesn't just deliver oxygen; it provides pressurised air to help the patient take bigger, more effective breaths. This actively reduces their work of breathing, giving the respiratory muscles a much-needed rest.

The Big Two: CPAP vs BiPAP

NIV is usually delivered in one of two main modes. Understanding the difference is key to choosing the right therapy for your patient.

CPAP (Continuous Positive Airway Pressure)

CPAP is the simplest form of NIV. It delivers one constant level of positive pressure throughout the entire breathing cycle (both inspiration and expiration).

• How it works: The ventilator maintains a constant pressure, effectively keeping the airways open. The patient breathes in and out against this continuous pressure.

• Best for: Type 1 Respiratory Failure (hypoxaemia), especially in cardiogenic pulmonary oedema. The constant pressure helps to recruit collapsed alveoli and push fluid out of the airspaces, improving oxygenation.

BiPAP (Bilevel Positive Airway Pressure)

BiPAP, as the name suggests, uses two different pressure levels.

• IPAP (Inspiratory Positive Airway Pressure): A higher pressure delivered when the patient breathes in. This helps them take a deeper breath and improves tidal volume.

• EPAP (Expiratory Positive Airway Pressure): A lower pressure delivered when the patient breathes out. This works like CPAP to keep the airways open.

• How it works: The ventilator detects the patient's own breathing effort and provides a higher pressure "boost" during inspiration. The difference between IPAP and EPAP (known as pressure support) is what helps remove carbon dioxide.

• Best for: Type 2 Respiratory Failure (hypercapnia), making it the go-to for a COPD exacerbation with a rising pCO2.

While BiPAP is more versatile, it can sometimes be trickier to set up and for the patient to synchronise with. For many straightforward cases of pulmonary oedema, CPAP is simpler and just as effective.

Why is NIV so Effective?

When used in the right patient, the effects of NIV can be significant. Here’s what it achieves:

• Reduces the work of breathing: This is its primary benefit. The patient no longer has to fight for every breath.

• Improves gas exchange: By keeping small airways and alveoli open (a process called recruitment), it creates a larger surface area for oxygen to enter the blood.

• Boosts cardiac function: In pulmonary oedema, the positive pressure reduces the amount of blood returning to the heart (preload) and the resistance the heart has to pump against (afterload). This is a massive help for a struggling left ventricle.

• Can deliver high oxygen concentrations: You can titrate the FiO2 up to 100% if needed.

• Helpsavoid intubation: By turning the tide in acute respiratory failure, NIV can prevent the need for invasive ventilation and an ITU admission, with all the associated risks.

Who Needs NIV on Your A&E Shift?

NIV is most effective for acute conditions where you can make a significant difference within a few hours. Think of it for these classic presentations:

• Cardiogenic Pulmonary Oedema: Often the most rapid and marked response. CPAP is usually the first choice.

• COPD Exacerbation: Particularly with hypercapnia and respiratory acidosis. BiPAP is the standard of care here and is recommended by NICE guidelines.

• Asthma: Can be used in severe attacks but requires very close monitoring in a high-dependency setting, as these patients can tire suddenly.

• Other causes: Can also be useful in obesity hypoventilation syndrome or certain neuromuscular conditions.

You can even start NIV in a patient with acceptable sats if they have severe dyspnoea and are clearly tiring. Reducing the work of breathing can speed up recovery and improve patient comfort

When to Avoid NIV: Key Contraindications

NIV is a fantastic therapy, but it's not right for everyone. Using it in the wrong situation can be dangerous. These are the key NIV contraindications:

• Apnoea/No Respiratory Drive: The patient must be able to breathe for themselves.

• Inability to Protect the Airway: If the patient is vomiting, has copious secretions, or has a reduced level of consciousness where you're worried about aspiration, NIV is not safe.

• Facial Trauma/Burns/Abnormal Anatomy: Anything that prevents a good mask seal.

• Undrained Pneumothorax: Positive pressure will make this worse.

• Patient Agitation/Non-cooperation: If the patient cannot tolerate the mask and is actively fighting it, it won't be effective and can increase distress.

A tricky area is patients with altered consciousness. While it's a relative contraindication, a patient with a hypercapnic COPD exacerbation is often confused because of their high CO2. In these specific cases, a closely monitored trial of NIV can sometimes reverse the confusion and avoid intubation. However, your team should always be preparing for intubation in parallel.

Crucially, NIV must never delay necessary intubation. A patient who is unconscious after a head injury with low sats needs a definitive airway, not a face mask.

A Practical Guide to Starting NIV

• Communicate: This is the most important step! The mask can feel claustrophobic. Explain to the patient what you are doing and why. Tell them the machine will help them breathe. A calm, cooperative patient is the key to success.

• Position: Sit the patient upright. This is the best position for breathing.

• Set Up:

  • Choose the right size mask.

  • Connect it to the ventilator and select the appropriate mode (e.g., NIV/CPAP or NIV/BiPAP).

  • Set your desired oxygen concentration (FiO2).

  • Start with low pressures to help the patient acclimatise. A good starting point is a CPAP of 3–4 cm H2O or BiPAP of 6/3 cm H2O.

• Apply the Mask: It's often easier with two people – one to hold the mask in place, the other to secure the straps. Let the patient hold the mask to their face initially to give them a sense of control. The seal should be snug, but not painfully tight. A small leak is okay.

• Titrate the Pressure: Once the patient is comfortable, gradually increase the pressures to a therapeutic level.

Sensible Starting Settings

• CPAP Settings: Start at 3–4 cm H2O and gradually increase to a target of 8–12 cm H2O.

• BiPAP Settings: Start at 6/3 or 8/4 cm H2O. Increase the IPAP to improve ventilation and the EPAP to improve oxygenation. A common target is 12–16 / 6–8 cm H2O.

How Do You Know It's Working?

You should see  clinical improvement within minutes.

• Look at the patient: The respiratory rate should slow, and the work of breathing should visibly decrease.

• Ask the patient: They should report feeling less breathless.

• Check the monitor: Oxygen saturations should improve.

• Get an ABG: After 15–30 minutes, a repeat arterial blood gas will give you objective evidence of whether you're improving oxygenation and/or clearing CO2.

If you don't see any improvement, don't wait. Re-check the mask seal, adjust the settings, and coach the patient. If it's still not working, it's time to reconsider your plan and call for senior help – you may need to escalate to intubation.

Remember for Your Next Shift

• Don't be afraid of NIV. It's a core skill for acute and general medicine, not just for ITU. You can do this!

• Think of it for pulmonary oedema and COPD. These are its key indications, where you'll see the best results.

• Patient cooperation is everything. Your communication skills are just as important as your technical skills.

• Know when to stop. Recognise the contraindications and never let NIV delay  necessary intubation.

• Start low and go slow with the pressure settings to help your patient tolerate the therapy.