From mild trauma pain-relief to precision laser surgery, gases have a fundamental role to play within the medical and healthcare industry. Rob Cockerill ascertains
how medical gases combat disease through an assortment of approaches.
A car comes screeching to a halt in the car park outside and half a minute later an anxious husband ushers his pensive partner through the double doors of the hospital entrance. Hours later in the maternity ward, and the proud father-to-be watches as his wife is administered with Entonox, an analgesic mixture of nitrous oxide gas and oxygen.
The Entonox gas is provided at hospitals as a relaxant, to calm screaming mothers through the painful labour process. It is just one of a number of areas in which industrial and medical gases are effective throughout the daily life of a busy public hospital.
Gas and air
Entonox, or ‘gas and air’ as it is often referred to, is the trademark name for a mixture of nitrous oxide (N2O) and oxygen (O2) and comprises 50% of each. Prospective mothers are often offered this potent yet harmless gas mixture at the start of the labour process, inhaled at the start of a contraction and until the contraction peaks or the individual indicates she’s had enough. At the height of a given contraction and intense pain, Entonox takes the edge off the pain sensation and also helps to calm the patient by serving to numb the pain centre in the brain.
Administered by inhalation from a cylinder or pipeline supply at a pressure of 137 bar, the analgesic effect of ‘gas and air’ is quite strong at the equivalent to 5-10mg of morphine and is characterised by a rapid onset and offset, meaning it is both very fast acting but can also wear-off quite rapidly.
This medical gas is therefore ideally suited for ladies close to the pain barrier during the labour process and has an important comforting role to play, for many mothers-to-be across the UK and the world.
Entonox, once within reach, is actually self administered and when yelping mothers aren’t grasping for the mask in sheer desperation, should ideally be used around 30 seconds before a contraction becomes painful. Nitrous oxide, as a 50% constituent, is itself active and does not require any changes within the body to become active, with this gas mixture having an onset of around the lung-to-brain circulation time of 30 seconds.
This medical gas mixture is a popular and powerful remedy then, capable of calming and soothing the painful process of childbirth and ensuring it is as comfortable as can be.
But nitrous oxide is not just a component in Entonox. As a rather weak general anaesthetic it has uses in a wide variety of medical and healthcare applications, including emergency medicine, surgical applications, dental procedures and as an effective agent for reducing patient anxiety.
Under room conditions, nitrous oxide is a colourless, non-flammable gas with a pleasant and almost sweet taste and aroma, used in surgery and dentistry for its anaesthetic and analgesic properties and commonly referred to as ‘laughing gas’. Way back as far as the 19th century, nitrous oxide was used by dentists and surgeons for its mild analgesic effects and this gas’ principal use today is still as an anaesthetic in medicine.
So while the anxious couple may have been rushing through the doors of the maternity wing in anticipation of delivering a healthy bouncing baby, the scene at the opposite end of the hospital spectrum couldn’t be more different. In Accident and Emergency (A&E) a young man lies on a bed in surgery experiencing a different kind of pain. And yet, while the 2 scenarios contrast sharply the presence and significance of medical gases is equally paramount for each situation.
After a mistimed and unfortunate accident the patient is in urgent need of a limb-repairing operation, introducing nitrous oxide once again. The gas is useful for analgesia and sedation and as a background anaesthetic in conjunction with more potent additives for major surgery. While it is still the most widely used anaesthetic gas and the perfect solution for the unfortunate patient awaiting minor surgery, nitrous oxide in gas mixtures is insufficient for major surgery.
When inhaled in pure form it is asphiyxiating , but in high concentrations of 80% plus with oxygen it induces a rapid but fairly shallow anaesthesia. As well as being widely used in such minor surgical practices and as a constituent in Entonox for mild trauma and childbirth, the role of this medical gas extends even further in hospitals and healthcare. As mentioned, it also has a role to play in major surgery too: in general anaesthesia it is used as a carrier gas in a 2:1 ratio with oxygen for more powerful general anaesthetic agents such as sevoflurane or desflurane.
Elsewhere in the hospital and medical field, gases have a fundamental function in a variety of daily practices.
Generally speaking the volume of nitrogen sold is now well in excess of oxygen and while the list of nitrogen applications is almost endless, the gas has a growing position within the hospital sector and is used for its inert or non-toxic characteristics. In its liquid state, nitrogen’s cryogenic properties deem it suitable for medical purposes – as a liquid it can be used in cryosurgery, biotechnology and the important cryogenic storage of organs.
The application of extreme cold to destroy abnormal or diseased tissue, cryosurgery is used to treat a number of diseases and disorders and skin conditions in particular.
Possibly not considered as crucial or influential within the hospital wards, this is in fact necessary for a number of complaints like warts, moles, skin tags and some internal disorders. Small skin cancers are also candidates for cryosurgical treatment, a minimally invasive procedure of little pain, little cost and minimal scarring. Using liquid nitrogen as the cooling or cryogenic solution, cryosurgery is effective by taking advantage of the destructive force of freezing temperatures on cells. At low temperatures ice crystals form inside the cells, capable of tearing them apart and further damage can occur when blood vessels supplying the diseased tissue freeze.
CO2 can also be used for such procedures and recent advances in technology and understanding have meant that argon gas can be utilised to produce ice formation.
In other minor, though no less significant, roles are a few other industrial gases.
Argon, although less than 1% of the atmosphere, is of increasing importance due to its absolutely inert nature and is used as a carrier gas in research and laboratory operations. Similarly, the noble or rare gases krypton and xenon have their own unique applications within the medical field. Among other applications, krypton is used in excimer lasers, particularly in surgery, while xenon is present in some excimer lasers and in the field of medicine can be found in anaesthesia or medical imaging.
A shot-lived dimeric or heterodimeric molecule formed from 2 species of which one is in an electronic excited state, excimer is most commonly applied in excimer lasers.
An excimer laser, or an exciplex laser as it is often known, is a form of ultraviolet laser used in eye surgery. Typically using a combination of an inert gas such as argon, krypton or xenon and a reactive gas like fluorine or chlorine, excimer lasers are perfectly suited to precision eye surgery and other delicate operations and have revolutionised such medical practices. Rather than burning or cutting, an excimer laser has the uniquely useful property of being able to remove extremely fine layers of tissue with almost no heating or change to the remainder of the tissue, all because an excimer laser adds enough energy to disrupt the molecular bonds of the surface tissue.
When it comes to thinking of medical gases and hospitals, possible the first thought conjured up by most of us is oxygen and the tall, slender cylinders it can be found in, at ward bedsides.
This is perhaps due in part to oxygen’s generic perception as the answer to most panic-stricken ailments and serial TV dramas that tend to portray such a depiction. It may be a well-founded perception, as oxygen is vital to healthcare and hospitals are the main users. Supplies are piped into hospitals and cylinder supplies are used for operating theatres, emergency wards, intensive care units and individual beds.
One of the companies providing medical gas supplies, including oxygen, to public hospitals and other healthcare facilities throughout the US is Matheson Tri-Gas. The company’s Tri-Care comprehensive Medical Gas Management programme provides a seamless medical gas supply system including bulk liquid and cylinder gases, high-pressure gases, nitrous oxide and a range of other services.
Bill Kroll, chairman of Matheson Tri-Gas Inc, comments, “Matheson Tri-Gas provides bulk oxygen, cylinder oxygen, blood gases, high pressure gases, nitrous oxide, and other pulmonary mixes just to name a few. Matheson Tri-Gas provides these products in bulk and/or cylinder form to public hospitals, universities, clinics, nursing homes, home medical care resellers and private institutions both in the US and abroad. We monitor hospital gas levels remotely to make sure they have the volumes needed to supply their patients.”
“Our products are manufactured and tested to FDA standards. Our equipment line is high quality and reliable. Without reliability of quality and service, people’s lives could be placed at risk. Our production and distribution teams are responsible for the high quality of service the hospitals and medical sector expect from us,” Kroll added.
The uptake of oxygen from air is the essential purpose of respiration, so it is no surprise that such a gas has taken on such an important task in medicine. Medical oxygen is required to be of at least 93% purity and ideally 95-99% purity. Used in a number of applications throughout the daily practices of a hospital, it is perhaps best known for its responsibility in gas mixtures and breathing gas.
As well as its use as a 50% component of Entonox, oxygen is used in recompression chambers, where pure oxygen is utilised to remove nitrogen from the bloodstream to prevent decompression sickness. The tissues and organs within the body can also become damaged if deprived of oxygen for a period longer than 4 minutes and the function of this medical gas then extends into the wider healthcare field, such as mobile oxygen units in care homes and the household.
And it is in the wider healthcare field in which the merits of oxygen appear to be increasingly finding favour. Hyperbaric oxygen therapy, which could soon become further widespread throughout the US and Canada, involves the medical use of oxygen at a higher than atmospheric pressure.
Increasingly finding favour in the US and Canada, hyperbaric oxygen therapy uses medical oxygen at a pressure higher than atmospheric.
Such therapy requires a patient to lie down inside a chamber filled with 100% pressurised oxygen and is thought to remedy a whole host of ailments.
The 100% pressurised oxygen stimulates the growth of new blood vessels and improves the flow of blood to areas with reduced circulation. All the lauded benefits of hyperbaric therapy are not proven though, and this treatment is not a common feature of hospitals and healthcare centres.
One of the most renowned uses of gases in the medical industry is another of the noble gases – helium.
Helium, something of a rare commodity at present due to demand exceeding supply, is used in breathing gas mixtures by divers and similar breathing mixtures to relieve respiratory difficulties.
A very inert gas and with a uniquely low boiling point (within a few degrees of absolute zero at -268.9oC), the extremely low temperature of liquid helium is utilised in superconducting magnets which are used in MRI scanners and specialist research apparatus.
Indeed, without the use of liquid helium in the medical sectors we may not be able to accurately determine certain illnesses and diseases and therefore not cure these or at least offer a solution.
Magnetic Resonance Imaging (MRI) is a medicalscanning method to demonstrate pathological or physiological alterations of living tissues and as such, provide a diagnosis of many minor or critical conditions. The implementation of liquid helium takes on an exceptionally significant role in this process.
The magnet is the largest and most expensive component of an MRI scanner and just as important as the strength of the magnet is the precision.Three types of magent have been used for these machines, of which one particular type is prevalent. Superconducting magnets are the most common and effective type used in MRI scanners and require cooling via liquid helium at -269oC. These magnets deliver extremely high field strength and very high stability, with the coils of superconductive wire immersed in liquid helium inside a vessel called a cryostat.
Ambient heat can cause the helium to slowly boil-off and in some cases a cryocooler is used to re-condense some helium vapour back into the liquid helium vessel. Several manufacturers now offer cryogenless scanners in which the magnet is cooled directly by a cryocooler, rather than immersion in liquid helium and despite the rising expense of this inert gas, liquid helium-cooled superconducting magnets are the most commonly used for MRI.
The role of this gas in preventing and combating disease is then, hugely significant and largely under-estimated by many of us.
No-one could doubt the importance of diligent, caring staff within our hospitals, nor hygienic excellence and the most technically advanced medical equipment possible. Few could question the immense significance of industrial gases within the medical field either it seems.
Bill Kroll affirms, “Medical gases play a significant role in the medical industry in that they support human life and allow many medical procedures to take place that couldn’t without them.”
“Quality supply of medical gas and equipment is extremely important since this is a product that supports human life and carries an extreme amount of liability because humans consume it.”
Just as a surgeon may only be as good as the precision tools he has to work with, a life saving procedure may only be as effective as the gas it has to operate with. Medical gases play an increasingly pivotal role in daily hospital practices. It is no exaggeration to say that without the industrial gases, both industry and medicine would have been unable to develop to their current extent and offer such possible comfort.