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BLB Mask (Boothby-Lovelace-Bulbulian Mask)
Overview
The BLB mask is a partial rebreathing oxygen mask named after its inventors — Dr. Walter Boothby, Dr. W. Randolph Lovelace, and Arthur Bulbulian — developed at the Mayo Clinic in the 1930s–1940s. It was one of the earliest practical oxygen delivery devices and was heavily used in aviation medicine during World War II.
Design & Components
| Feature | Details |
|---|---|
| Type | Partial rebreathing mask |
| Reservoir bag | Attached; holds ~1 L of oxygen |
| Valves | One-way inhalation and exhalation valves |
| Seal | Oral-nasal fitting with adjustable metal nosepiece |
| Flow rate | Typically 6–8 L/min |
How It Works
- Inspiration: The patient inhales a mixture of 100% oxygen from the reservoir bag plus ambient air.
- Partial rebreathing: The first third of exhaled air (from anatomical dead space, which is rich in oxygen and low in CO₂) re-enters the reservoir bag.
- Exhalation: The remaining exhaled air (containing CO₂) exits through exhalation valves.
- This design conserves oxygen while still delivering a relatively high FiO₂.
Oxygen Delivery
| Flow Rate | Approximate FiO₂ |
|---|---|
| 6 L/min | ~60% |
| 8 L/min | ~70–80% |
| 10 L/min | ~80–90% |
FiO₂ can vary based on the patient's respiratory rate, tidal volume, and mask fit.
Indications
- Hypoxia requiring moderate-to-high FiO₂
- Aviation / high-altitude hypoxia (original primary use)
- Pre-hospital and emergency oxygen therapy
- Carbon monoxide poisoning (high-FiO₂ delivery)
- Post-operative oxygen supplementation (historical use)
BLB vs. Other Oxygen Masks
| Mask Type | FiO₂ Range | Reservoir Bag | Rebreathing |
|---|---|---|---|
| Nasal cannula | 24–44% | No | No |
| Simple face mask | 35–55% | No | Partial |
| BLB mask | 60–90% | Yes | Partial |
| Non-rebreather mask | 90–95% | Yes | No |
| Venturi mask | 24–60% (fixed) | No | No |
Advantages
- Higher FiO₂ than simple masks at lower flow rates
- Oxygen-conserving (partial rebreathing design)
- Good seal, suitable for aviation environments
- Durable and adjustable fit
Limitations
- CO₂ accumulation risk if flow rate is too low (< 6 L/min)
- Bulkier and less comfortable than nasal cannula
- Not suitable for patients with COPD (hypercapnic drive concern)
- Largely replaced in clinical settings by non-rebreather masks and high-flow nasal cannula (HFNC)
Historical Significance
The BLB mask was a landmark innovation in respiratory support. It was standard equipment for U.S. Army Air Forces pilots in WWII and contributed significantly to the understanding of supplemental oxygen physiology. It formed the conceptual basis for modern partial rebreathing and non-rebreathing masks.
Summary: The BLB mask is a partial rebreathing oxygen delivery device capable of delivering FiO₂ of 60–90% at flow rates of 6–10 L/min. While largely supplanted by modern devices, it remains historically important and its design principles underpin many current oxygen delivery systems.
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