REBEL Core Cast 148.0–Demystifying Non-Invasive Ventilation & HiFlow

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Jan 12, 2026

Eric Acker, DO, a resident physician specializing in emergency medicine, joins the discussion on non-invasive ventilation techniques. They break down the differences between CPAP and BiPAP, highlighting their uses for conditions like pulmonary edema and COPD. The conversation dives into practical aspects, such as mask discomfort and sedation risks, while demystifying high-flow nasal cannula (HFNC) mechanics. Acker emphasizes how these supportive modalities stabilize patients and improve oxygenation, all without needing invasive measures.

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INSIGHT

Hairdryer Analogy Clarifies Modes

Frank uses a hairdryer-in-the-mouth analogy: CPAP is one continuous speed and BiPAP cycles high (IPAP) on inspiration and lower (EPAP) on expiration.
Use CPAP for hypoxemia/recruitment and BiPAP when you need to augment tidal volume and unload inspiratory muscles.

ADVICE

Avoid Sedation To Tolerate Mask NIV

Avoid over-sedating patients to tolerate mask NIV because their airway remains unprotected and sedation risks hypotension and altered mental status.
Monitor patients closely and weigh tolerance benefits against the high-stakes risk of an unsecured airway.

ADVICE

Practical Starting Pressures

Start BiPAP settings around IPAP 10 / EPAP 5 and ensure a delta of at least ~4 cm H2O between pressures.
Increase IPAP to improve CO2 clearance and increase EPAP to improve oxygenation; widen both if the patient is hypoxemic and hypercapnic.

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🗝️ Key Points

💨 NIV = Support without a tube: CPAP, BiPAP, and HFNC improve oxygenation and reduce the work of breathing.
🫁 CPAP = Continuous pressure: Best for hypoxemic patients (e.g., pulmonary edema, OSA).
️ BiPAP = Two pressures (IPAP/EPAP): Great for hypercapnic failure (e.g., COPD, obesity hypoventilation).
🌬️ HFNC = Heated, humidified high flow: Reduces effort, improves comfort, and enhances oxygen delivery.
🩺 Supportive, not definitive: NIV stabilizes patients while the underlying cause is treated.

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📝 Introduction

Non-invasive ventilation (NIV) refers to respiratory support provided without endotracheal intubation. The most common modalities include continuous positive airway pressure (CPAP), bilevel positive airway pressure (BiPAP), and high-flow nasal cannula (HFNC). These therapies aim to improve oxygenation, reduce the work of breathing, and potentially prevent invasive mechanical ventilation.

💨 CPAP and BiPAP

CPAP delivers a single, continuous pressure during inspiration and expiration. This pressure (commonly 5–10 cm H₂O) helps recruit atelectatic alveoli, reduce shunt, and improve oxygenation. It is commonly used for conditions like pulmonary edema, obstructive sleep apnea, or mild hypoxemia without significant ventilatory failure.
BiPAP alternates between two pressures:
- Inspiratory positive airway pressure (IPAP), augments tidal volume and unloads inspiratory muscles.
- Expiratory positive airway pressure (EPAP), maintains alveolar recruitment and improves oxygenation.
  The differential between IPAP and EPAP is critical for reducing hypercapnia in patients with COPD exacerbations or acute hypercapnic respiratory failure.
Indications
- CPAP: hypoxemia without major ventilatory failure (e.g., cardiogenic pulmonary edema, atelectasis, OSA).
- BiPAP: hypercapnia with increased work of breathing (e.g., COPD exacerbation, neuromuscular weakness, obesity hypoventilation).
A helpful way to conceptualize CPAP and BiPAP is through the hairdryer analogy. Imagine placing a hairdryer in your mouth:

🩺 Clinical Considerations

Masks can be uncomfortable, impair secretion clearance, and limit oral intake.
Some patients require sedation to tolerate NIV, but this carries risks in patients with unprotected airways.
NIV is thus a high-stakes intervention requiring close monitoring.
Common starting dose to understand titration, but start at the level appropriate for your patient: IPAP 10 cm H₂O / EPAP 5 cm H₂O (“10/5”) and are titrated:
- Increase IPAP to improve tidal volume and CO₂ clearance.
- Increase EPAP to recruit alveoli and improve oxygenation.
- Both may be raised simultaneously if the patient is both hypoxemic and hypercapnic.

🚀 High-Flow Nasal Cannula (HFNC)

H: Heated & humidified – improves mucociliary clearance, prevents airway drying, and enhances tolerance. I: Inspiratory flow – high flow meets or exceeds patient demand, reducing respiratory rate and effort.
F: Functional residual capacity – modest generation of positive end-expiratory pressure (PEEP), promoting alveolar recruitment.
L: Lighter – generally more comfortable and less restrictive than mask-based NIV.
O: Oxygen dilution – minimizes entrainment of room air, delivering higher and more predictable FiO₂.
W: Washout – flushes anatomical dead space, reducing CO₂ rebreathing.
HFNC delivers heated, humidified oxygen at high flow rates (30–60 L/min) through wide-bore nasal prongs. A mnemonic, H-I-F-L-O-W, helps summarize its mechanisms:
Indications: Traditionally used for acute hypoxemic respiratory failure (e.g., pneumonia), HFNC is increasingly studied for hypercapnic failure as well, with trials suggesting non-inferiority to BiPAP in select populations.

Post Peer Reviewed By: Marco Propersi, DO (Twitter/X: @Marco_propersi), and Mark Ramzy, DO (X: @MRamzyDO)

👤 Show Notes

Syed Moosi Raza, MD

PGY 3 Internal Medicine Resident

Cape Fear Valley Internal Medicine Residency Program Fayetteville NC Aspiring Pulmonary Critical Care Fellow

REBEL Core Cast 148.0–Demystifying Non-Invasive Ventilation & HiFlow

Hairdryer Analogy Clarifies Modes

Avoid Sedation To Tolerate Mask NIV

Practical Starting Pressures

🧭 REBEL Rundown

🗝️ Key Points

📝 Introduction

💨 CPAP and BiPAP

🩺 Clinical Considerations

🚀 High-Flow Nasal Cannula (HFNC)

👤 Show Notes

Syed Moosi Raza, MD

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