This liquid is so good at dissolving oxygen, you can breathe it. But why though?
Certain perfluorinated liquids have a unique molecular structure that allows them to dissolve high amounts of oxygen physically, enabling them to transport oxygen to living tissues and making liquid breathing possible under specific conditions. Their poor molecular packing creates cavities that trap oxygen, while their chemical inertness prevents harmful reactions. Despite this, limitations in carbon dioxide removal and physical properties restrict their widespread use.
Understanding the Nature of the Liquid and Its Gas Solubility
Perfluorinated Liquids and Their Unique Gas Dissolution
This liquid belongs to a class known as perfluorinated liquids. These are composed of carbon-fluorine bonds that form highly polarized yet sterically hindered molecules. Because of this, they do not pack closely together in the liquid phase, creating numerous small cavities within the fluid.
These cavities are central to the liquid’s ability to dissolve gases. Rather than chemically binding oxygen, the liquids physically trap the gas molecules within these microscopic spaces. This physical solubility applies broadly to gases, including oxygen (O2), carbon dioxide (CO2), and carbon monoxide (CO).
Mechanism of Gas Solubilization in the Liquid
The gas dissolution process has two main energetic steps:
- Formation of cavities in the liquid. This requires energy to disrupt the molecular packing.
- Incorporation of the gas molecules into these cavities, which is energetically favorable due to the low interaction between fluorinated molecules and gases.
The outcome is a liquid that contains significant volumes of dissolved gas, disproportionate to ordinary liquids like water.
Molecular Structure and Its Influence on Gas Solubility
The molecular geometry of these fluorinated compounds is key. The molecules have bulky fluorine atoms causing steric hindrance and strong dipole moments that prevent dense packing. Due to these factors, the molecules arrange loosely and irregularly.
This loose packing leads to a high free volume in the liquid. The liquid essentially behaves like a flexible sponge, accommodating and dissolving gas molecules easily.
Applications of Oxygen-Dissolving Liquids in Breathing
Liquid Breathing for Oxygenation
This unique property makes perfluorinated liquids an area of interest for liquid breathing. Liquid breathing involves saturating the liquid with oxygen, so it carries enough to support respiration in the lungs.
Oxygen saturation requires bubbling oxygen through the liquid or exposing it to pure oxygen to displace other dissolved gases. These liquids resist reaction with oxygen at ambient temperatures, maintaining chemical stability during use.
Medical Use as Blood Substitutes
Researchers have explored formulating emulsions of perfluorinated liquids mixed with water and surfactants. These emulsions can circulate in the bloodstream temporarily, acting as oxygen carriers when red blood cells are insufficient.
This potential application targets emergency medicine fields where blood substitutes could save lives during severe blood loss. The emulsions improve biocompatibility and ease of transport compared to pure perfluorinated liquids.
Limitations Observed in Research
Although promising, several key limitations exist:
- Density: The liquids are denser than air or blood, increasing strain on lung tissues during respiration.
- CO2 Removal: Carbon dioxide removal is inefficient, leading to acid buildup (acidosis) after about one hour of use.
- Respiratory Discomfort: Breathing liquid produces sensations similar to drowning, causing discomfort even if oxygenation occurs.
- Duration: Safe liquid breathing has only been demonstrated for very short periods.
- Deep-Sea Use: The technology does not work well for deep-sea diving due to pressure and gas exchange limitations.
Animal Experiments and Findings
In laboratory settings, animals like rats have survived when breathing oxygen-saturated perfluorinated liquids. However, attempts to return these animals to air breathing resulted in deaths, highlighting physiological challenges.
These experiments confirm oxygen transport is possible but show that transitioning between liquid and gas breathing remains complex.
Chemical Stability and Toxicity Considerations
Chemical Inertness
The perfluorinated liquids’ chemical inertness ensures they do not react with oxygen or other molecules at normal temperatures, preventing oxidative damage during respiration.
This property is essential for safely carrying oxygen without creating harmful byproducts inside the lungs or bloodstream.
Concerns with Toxicity and Persistence
Despite acute low toxicity, the long-term effects need careful evaluation. These compounds fall into the larger family of per- and polyfluoroalkyl substances (PFAS), some of which exhibit toxicity and environmental persistence.
The unknown potential for harm arises from their slow clearance rates and bioaccumulation tendencies seen in related compounds.
Clearance from the Body
Initial research found that perfluorinated compounds linger in circulation for prolonged periods, raising concerns about chronic effects.
Later studies attempted to develop variants with higher vapor pressures to allow exhalation and faster body clearance, aiming to reduce retention time and toxicity.
Additional Scientific Insights
Broader Gas Solubility Beyond Oxygen
Besides oxygen, these liquids dissolve other gases effectively. Carbon dioxide shows even higher solubility compared to oxygen, though its physical removal from the lungs remains problematic.
Carbon monoxide solubility closely matches oxygen, which is relevant in toxicological contexts.
Physical Challenges in Liquid Breathing
The lungs are structurally optimized for gas exchange with air, not liquids. Transporting dense liquid through alveoli causes mechanical strain, interfering with normal respiratory patterns.
Furthermore, issues with surfactant function and liquid viscosity complicate oxygen delivery and carbon dioxide removal.
Historical Context and Research Status
This field gained notable attention in the 1980s and 1990s amid hopes that liquid ventilation could revolutionize respiratory therapies.
However, research progress slowed due to technical, physiological, and safety challenges. The approach remains mostly experimental without widespread clinical adoption.
Summary: Why This Liquid Can Be Breathed
- Perfluorinated liquids have poor molecular packing creating cavities that physically dissolve oxygen and other gases in large quantities.
- Their chemical inertness prevents harmful reactions with oxygen, allowing saturation and safe oxygen transport.
- Oxygen dissolved in these cavities can transfer to tissues during liquid breathing, sustaining life temporarily.
- Density and mechanical strain on the lungs complicate liquid breathing, causing discomfort and limiting duration.
- Removal of carbon dioxide remains inefficient, restricting practical long-term use.
- Research into emulsions boosts compatibility but toxicity and physiological challenges remain hurdles.
Key Takeaways
- Oxygen solubility in perfluorinated liquids is a physical phenomenon driven by molecular structure and free volume.
- Liquid breathing is possible by saturating these liquids with oxygen, demonstrated in animal experiments.
- Physical and physiological constraints limit clinical and commercial applications at present.
- C hemical stability and inertness support safety but persistence in the body poses toxicity concerns.
- Current research focuses on improving formulation, gas exchange, and safety to realize future applications.
What makes this liquid so effective at dissolving oxygen?
It has poor molecular packing, creating tiny cavities that trap oxygen and other gases. The liquid’s structure prevents tight packing, allowing more gas to be physically dissolved within these spaces.
Can humans actually breathe this liquid safely?
Humans can breathe oxygen-rich versions of this liquid briefly, but it’s not practical long-term. The liquid’s density strains the lungs, and it doesn’t remove carbon dioxide well, causing breathing issues.
Why doesn’t the liquid react with the oxygen it carries?
The liquid is chemically stable and inert at normal temperatures. It does not form chemical bonds with oxygen, allowing oxygen to remain dissolved without being consumed or altered.
What limits the use of this liquid in medical applications?
Its high density and inability to efficiently remove carbon dioxide limit safe use. Also, it stays in the body for a long time, raising concerns about toxicity and clearance.
Have animals been successfully kept alive by breathing this liquid?
Yes, experiments with lab rats and other animals showed survival using oxygenated liquid breathing. However, transitioning back to air breathing often proved fatal, showing the method’s current risks.
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