Noninvasive Ventilation (NIV): CPAP, BiPAP & HFNC

Use these numbers at the bedside. Settings are starting points from the cited trials and guidelines; titrate to the patient and follow local protocols and medical direction.

NIV pushes air into the lungs under positive pressure, through a face mask or a helmet. No tube goes into the airway. CPAP holds one pressure for the whole breath cycle. BiPAP (bilevel NIV, also called NIPPV) gives a higher inspiratory pressure (IPAP) and a lower expiratory pressure (EPAP). HFNC blows heated, humidified oxygen at high flow through nasal prongs. You get some positive pressure too, with no sealed mask.

How It Works

• CPAP: Splints the airway and alveoli open. In pulmonary oedema it cuts preload and afterload. Oxygenation improves.
• BiPAP: IPAP supports the tidal volume and takes load off the work of breathing. EPAP keeps the alveoli open.
• HFNC: Washes out dead space. FiO₂ stays close to fixed. You get modest positive pressure with a more comfortable interface.
• Apneic oxygenation: Nasal oxygen during laryngoscopy extends the safe apnea time.

Where It Fits

Use NIV for hypercapnic failure from a COPD exacerbation and for cardiogenic pulmonary oedema. Hypoxemic failure is a different story. ERS 2022 suggests HFNC over conventional oxygen and over NIV, so NIV there is a selective choice. Reassess early. Rising work of breathing, falling consciousness or a poor ROX or HACOR trend means plan the intubation now, not later.

Indications

• Hypercapnic COPD exacerbation: the patient is acidotic (pH < 7.35) with PaCO₂ above 6.5 kPa (about 49 mmHg), and that persists after optimal medical therapy (BTS/ICS 2016). Across 17 trials in a Cochrane review (PaCO₂ above 45 mmHg), NIV added to usual care cut mortality (RR 0.54, 95% CI 0.38 to 0.76) and the need for intubation (RR 0.36, 95% CI 0.28 to 0.46).
• Acute cardiogenic pulmonary oedema: add CPAP or NIPPV to standard treatment for severe distress. In 3CPO, 7-day mortality was 9.8% with standard oxygen and 9.5% with NIV (P=0.87). What NIV bought was speed. It improved dyspnoea, heart rate, acidosis and hypercapnia faster at 1 h. The Cochrane review found that NIV may reduce hospital mortality (low-certainty evidence, RR 0.65, 95% CI 0.51 to 0.82). It probably reduces intubation too (moderate-certainty evidence, RR 0.49, 95% CI 0.38 to 0.62).
• Hypoxemic respiratory failure (no hypercapnia): ERS 2022 suggests HFNC over conventional oxygen and over NIV in hypoxaemic acute respiratory failure, as conditional recommendations. Let the early ROX or HACOR trend decide whether to continue or escalate.
• Preoxygenation before intubation: in the PREOXI trial, NIV preoxygenation cut hypoxemia during intubation compared with an oxygen mask (9.1% vs 18.5%).

Absolute Contraindications

Cardiac or respiratory arrest, and inability to protect the airway. An unconscious patient, one in arrest, or one who cannot protect the airway needs intubation, not a mask. Untreated pneumothorax and fixed upper-airway obstruction count as absolute too, until they are resolved. For example, the pneumothorax is drained.

Relative Contraindications & Cautions

• Decreased consciousness or poor airway protection: put the mask on and the aspiration risk goes up.
• Vomiting or active GI bleeding: aspiration is the risk, and the mask can soil the airway.
• Recent upper-airway or upper-GI surgery: Mask pressure and leak may disrupt the repair. Discuss it with the surgical team.
• Facial trauma, burns or a mask that cannot seal: the leak stops effective ventilation.
• Haemodynamic instability: NIV cuts preload. Treat the hypotension first, per protocol.
• Agitated or uncooperative patient: Poor synchrony and mask intolerance follow. Start with coaching, a mask refit and pressure adjustment. Sedation during NIV is a specialist decision. See the analgosedation page.

Mild drowsiness from hypercapnia is not an absolute bar. BTS/ICS 2016 says adverse features should not, on their own, stop a trial of NIV. Relative contraindications still need closer supervision, a monitored bed or HDU/ICU, and an early call: continue NIV or intubate.

Consider an Alternative

Choose HFNC or conventional oxygen for patients who are alert and not hypercapnic. Move to intubation with RSI when NIV fails or the airway is unprotected. Use intubation for the airway itself.

Abort / Stop Criteria

Stop NIV and get ready to intubate when consciousness falls, the patient cannot protect the airway, vomiting starts, a new pneumothorax appears, or there is no improvement after reassessment. A HACOR above 5 at 1 h means urgent reassessment and intubation planning. The early failure markers are under Confirmation & Monitoring.

Team Roles During the Procedure

• Operator: applies and fits the interface, sets the mode and pressures.
• Airway lead: watches for failure and holds the intubation plan.
• Medication clinician: gives bronchodilators, diuretics or nitrates per order.
• Monitor and recorder: SpO₂, EtCO₂, respiratory rate, BP, mental status and times.

Anatomic Difficulty

For NIV, interface fit matters more than anatomy. Check the face for a seal, and the airway for protection.

Physiologic Risk

• Acidosis and hypercapnia: This is the COPD case for NIV: pH below 7.35 and PaCO₂ above 6.5 kPa (about 49 mmHg), still there after optimal medical therapy (BTS/ICS 2016).
• Hypoxemia: SpO₂ below 90% on oxygen, or a PaO₂/FiO₂ ratio at or below 300 mmHg (a common threshold). That is hypoxemic failure.
• Haemodynamics: Hypotension or shock makes the preload drop from NIV dangerous. Treat first.
• Exclusion thresholds: Your agency protocol sets the EMS CPAP exclusion criteria, such as a systolic BP limit. This page does not state them.
• Work of breathing: Accessory muscle use and respiratory rate show failure first.

Site / Device Check

• Power and gas: ventilator or CPAP source, oxygen supply and flow, humidifier if used.
• Circuit and valve: exhalation port clear; leak test before the mask goes on.

Equipment

• Interface: nasal or full-face mask in at least two sizes; helmet where available
• Device: CPAP or bilevel ventilator with a pressure gauge and leak control
• Oxygen source: with flowmeter or blender for FiO₂ control
• HFNC: heated humidifier, nasal cannula sizes, and flow controller
• Monitoring: pulse oximetry, EtCO₂ and continuous ECG
• Infection control: viral filter on the exhalation port where the device allows, and aerosol precautions per local policy
• Rescue: suction, bag-mask ventilation, supraglottic airway and intubation equipment

Sizing

Choose the smallest mask that seals without excess pressure on the nasal bridge. For pediatric mask sizing, see the pediatric equipment sizing page.

Patient Positioning & Preparation

Position the patient upright as the protocol allows. Explain the mask and how to signal distress. Give bronchodilators and other drugs per protocol before the mask goes on, unless they are given in-line.

These are typical adult references, so check them against local protocol and the current drug label. Doses vary by protocol; follow local protocols and medical direction.

Ventilator and CPAP Settings

Treat these as trial settings, not device labels. Start at the lowest pressure that controls work of breathing, then reassess within the first hour.

Adjuncts Given per Protocol

• Bronchodilators: albuterol and ipratropium in COPD and asthma. Nebulize in-line only if the device and protocol allow it. This page does not cover drug loss or placement in a vented circuit.
• Diuretic and nitrate: furosemide and nitroglycerin for cardiogenic pulmonary oedema, per protocol.
• Oxygen target: Titrate oxygen to the target SpO₂. In hypercapnic COPD or other hypercapnic risk, aim for SpO₂ 88–92% (BTS/ICS 2016) and avoid hyperoxia. NIV does not replace controlled oxygen.

Phase 1: Prepare

1. Confirm the indication: hypercapnic COPD, cardiogenic pulmonary oedema, or hypoxemic failure. Check that the patient can protect the airway.
2. Take a baseline: SpO₂, respiratory rate, mental status, BP and an arterial blood gas (required before and after starting NIV in COPD, BTS/ICS 2016).
3. Select the interface and size: fit the mask and test the seal before applying.
4. Set the device: CPAP pressure or IPAP/EPAP and FiO₂ per the protocol.

Phase 2: Perform

5. Apply the mask: position it, secure the straps without overtightening, and explain the signal to stop.
6. Titrate: increase pressure in small steps to reduce work of breathing and improve SpO₂.
7. Give adjuncts per protocol: bronchodilator, diuretic or nitrate as ordered.
8. Reassess at the first hour: work of breathing, consciousness, SpO₂, RR and gas if available.

Phase 3: Confirm & Secure

9. Confirm response: check the findings listed under Confirmation & Monitoring.
10. Document settings and times: pressures, FiO₂, mask type, response and any changes.
11. Plan the next step: continue, wean, or escalate per the failure plan on the RSI page.

Alternative Technique: Preoxygenation with NIV

Before induction, use NIV in place of a standard mask for preoxygenation, if the protocol allows it. PREOXI compared NIV with an oxygen mask in critically ill adults. Keep the same plan running through intubation, with apneic oxygenation. See RSI.

Primary Confirmation

Is it working? The one objective check that matters is the clinical response. Work of breathing falls, SpO₂ climbs at a stable FiO₂, and the respiratory rate drops. In cardiogenic pulmonary oedema, look for fewer crackles, better SpO₂ and less accessory muscle use.

Secondary Confirmation

• ROX index: (SpO₂/FiO₂)/RR at 2, 6 and 12 h. At or above 4.88, the value goes with lower intubation risk. It was derived in pneumonia patients on HFNC.
• HACOR score: Above 5 at 1 h means urgent reassessment and intubation planning. It was derived in hypoxemic patients. A low score does not rule out failure.
• Blood gas: PaCO₂ and pH trend, especially in COPD

Ongoing Monitoring

• Continuous: SpO₂ and ECG; EtCO₂ where the device allows it
• Frequently at first, per protocol: RR, work of breathing, consciousness and mask fit
• Hourly, then per protocol: reassess with ROX or HACOR trends

Pediatrics

This page covers adults only. Pediatric NIV and HFNC settings, interfaces and failure criteria are not in it. Follow the pediatric protocol and medical direction. For mask size, use equipment sizing. For failure planning, use pediatric airway. For any adjunct drug, use weight-based dosing.

Older Adults

• Frailty and cognition: Delirium and mask intolerance come up more often. Reassess consciousness often.
• Chronic disease: COPD and heart failure are common here. Treat the indication, not the number on the monitor.

Pregnancy

This page does not give pregnancy-specific oxygen targets or NIV settings. Follow obstetric and local protocols, and bring the obstetric team in early.

• Aspiration risk: Pregnancy delays gastric emptying. Vomiting and aspiration both become more likely. Screen for vomiting before the mask.
• Positioning: Relieve aortocaval compression with left uterine displacement, where the protocol allows it.

Obesity

• Interface: You may need a larger or specialized mask to get a seal.
• Preoxygenation: NIV preoxygenation reduced hypoxemia in PREOXI. The cited trial does not report an obesity subgroup.
• Obesity hypoventilation or sleep apnoea: Bilevel NIV is an established long-term treatment. In acute care, the same failure criteria apply.

Physiologically Difficult

• Severe acidosis: NIV may help COPD. If the trend is poor, intubation may be needed.
• Acute asthma: Evidence for NIV is limited. Use it only with specialist input and a clear failure plan.
• Immunocompromised: Bring the ICU team in early, and use the same failure criteria.
• After extubation: For patients at high risk of extubation failure, ERS 2022 suggests NIV over HFNC. The exception is a contraindication to NIV.

Immediate Aftercare

• Reassess: SpO₂, RR, work of breathing, consciousness and BP.
• Continue or wean: per the protocol and your reassessment trend.

Ongoing Maintenance

• Mask care: check fit, skin and cleanliness every hour.
• Humidification: keep the circuit and humidifier running for HFNC.

Transport Considerations

• Securing: strap the mask and the device so they do not move in the vehicle.
• Reassess after every move: recheck SpO₂, consciousness and mask seal.
• Noise and vibration: rely on waveform and monitor trends, not sound.
• Escalation: carry the intubation plan with you.
• Air transport and altitude: this page does not cover gas expansion, pressure effects on the mask seal or in-flight interface fit. Follow your air-medical protocol.

Pearls

• Start early, reassess often: Once the patient is exhausted, NIV has less to work with. Start before that.
• Pick the interface that seals: No seal, no trial. A leaking mask ends it.
• Use ROX and HACOR as trends: A single reading rarely decides anything.
• Preoxygenate with NIV when the protocol allows: In PREOXI, hypoxemia during intubation dropped.

Common Pitfalls

• Mask in a drowsy patient: remove and secure the airway first.
• Waiting too long: RR climbing and consciousness falling? Plan the intubation now, not later.
• Trusting SpO₂ alone: Look at the work of breathing and the mental status too, not just the number.

Skill Maintenance

• Practice mask fitting and sealing on a manikin each quarter
• Run a simulated NIV failure and transition to intubation
• Review ROX and HACOR calculations in case debriefs
• Check device settings and humidifier function at each shift