physics

Liquid breathing

Liquid breathing is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Liquid breathing rather than just read about it. In short: Liquid breathing is a form of respiration in which a normally air-breathing organism breathes an oxygen-rich liquid which is capable of CO2 gas exchange (such as a perfluorocarbon). The liquid involved requires certain physical properties, such as respiratory gas solubility, density, viscosity, vapor pressure and lipid solubility, which some perfluorochemicals (PFCs) have.

Key takeaways

Liquid breathing belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Liquid breathing to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Liquid breathing from memory before moving on to harder problems.

Reference excerpt

Liquid breathing is a form of respiration in which a normally air-breathing organism breathes an oxygen-rich liquid which is capable of CO2 gas exchange (such as a perfluorocarbon). The liquid involved requires certain physical properties, such as respiratory gas solubility, density, viscosity, vapor pressure and lipid solubility, which some perfluorochemicals (PFCs) have. Thus, it is critical to choose the appropriate PFC for a specific biomedical application, such as liquid ventilation, drug delivery or blood substitutes. The physical properties of PFC liquids vary substantially; however, the one common property is their high solubility for respiratory gases. In fact, these liquids carry more oxygen and carbon dioxide than blood does. In theory, liquid breathing could assist in the treatment of patients with severe pulmonary or cardiac trauma, especially in pediatric and neonatal cases. Liquid breathing has also been proposed for use in deep diving and space travel. Despite some recent advances in liquid ventilation, a standard mode of application has not yet been established.

Approaches

As liquid breathing is still a highly experimental technique, there are several proposed approaches.

Total liquid ventilation Although total liquid ventilation (TLV) with completely liquid-filled lungs can be beneficial, the complex liquid-filled tube system required is a disadvantage compared to gas ventilation—the system must incorporate a membrane oxygenator, heater, and pumps to deliver to, and remove from the lungs tidal volume aliquots of conditioned perfluorocarbon (PFC). One research group led by Thomas H. Shaffer has maintained that with the use of microprocessors and new technology, it is possible to maintain better control of respiratory variables such as liquid functional residual capacity and tidal volume during TLV than with gas ventilation. Consequently, the total liquid ventilation necessitates a dedicated liquid ventilator similar to a medical ventilator except that it uses a breathable liquid. Many prototypes are used for animal experimentation, but experts recommend continued development of a liquid ventilator toward clinical applications. Specific preclinical liquid ventilator (Inolivent) is currently under joint development in Canada and France. The main application of this liquid ventilator is the ultra-fast induction of therapeutic hypothermia after cardiac arrest. This has been demonstrated to be more protective than slower cooling method after experimental cardiac arrest.

Partial liquid ventilation In contrast, partial liquid ventilation (PLV) is a technique in which a PFC is instilled into the lung to a volume approximating functional residual capacity (approximately 40% of total lung capacity). Conventional mechanical ventilation delivers tidal volume breaths on top of it. This mode of liquid ventilation currently seems technologically more feasible than total liquid ventilation, because PLV could utilise technology currently in place in many neonatal intensive-care units (NICU) worldwide. The influence of PLV on oxygenation, carbon dioxide removal and lung mechanics has been investigated in several animal studies using different models of lung injury. Clinical applications of PLV have been reported in patients with acute respiratory distress syndrome (ARDS), meconium aspiration syndrome, congenital diaphragmatic hernia and respiratory distress syndrome (RDS) of neonates. In order to correctly and effectively conduct PLV, it is essential to

properly dose a patient to a specific lung volume (10–15 ml/kg) to recruit alveolar volume redose the lung with PFC liquid (1–2 ml/kg/h) to oppose PFC evaporation from the lung. If PFC liquid is not maintained in the lung, PLV can not effectively protect the lung from biophysical forces associated with the gas ventilator. New application modes for PFC have been developed. Partial liquid ventilation (PLV) involves filling the lungs with a liquid. This liquid is a perfluorocarbon such as perflubron (brand name Liquivent). The liquid has some unique properties. It has a very low surface tension, similar to the surfactant substances produced in the lungs to prevent the alveoli from collapsing and sticking together during exhalation. It also has a high density, oxygen readily diffuses through it, and it may have some anti-inflammatory properties. In PLV, the lungs are filled with the liquid, the patient is then ventilated with a conventional ventilator using a protective lung ventilation strategy. The hope is that the liquid will help the transport of oxygen to parts of the lung that are flooded and filled with debris, help remove this debris and open up more alveoli improving lung function. The study of PLV involves comparison to protocolized ventilator strategy designed to minimize lung damage.

PFC vapor Vaporization of perfluorohexane with two anesthetic vaporizers calibrated for perfluorohexane has been shown to improve gas exchange in oleic acid-induced lung injury in sheep. Predominantly PFCs with high vapor pressure are suitable for vaporization.

Aerosol-PFC With aerosolized perfluorooctane, significant improvement of oxygenation and pulmonary mechanics was shown in adult sheep with oleic acid-induced lung injury. In surfactant-depleted piglets, persistent improvement of gas exchange and lung mechanics was demonstrated with Aerosol-PFC. The aerosol device is of decisive importance for the efficacy of PFC aerosolization, as aerosolization of PF5080 (a less purified FC77) has been shown to be ineffective using a different aerosol device in surfactant-depleted rabbits. Partial liquid ventilation and Aerosol-PFC reduced pulmonary inflammatory response.

Human usage

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Liquid breathing

Start with the simplest possible case. Write down what Liquid breathing claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Liquid breathing before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Liquid breathing ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Liquid breathing

In research: Liquid breathing appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Liquid breathing in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Liquid breathing is common in secondary-school and first-year university syllabi. It links to neighbouring topics Liquids, Medical procedures, Modes of mechanical ventilation, so understanding it makes those chapters shorter.
In everyday life: Look for Liquid breathing outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Liquid breathing in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Liquid breathing means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Liquid breathing out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Liquid breathing in simple terms?

Why does Liquid breathing matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Liquid breathing?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Liquid breathing.