Hyperbaric oxygenation

Essence and the action mechanism

At the heart of hyperbaric oxygenation rising of arterial pressure of oxygen (O2) in organism fluid mediums (plasma, a lymph, an interintercellular lymph, etc.) lays. It leads to the conforming augmentation of their oxygen capacity and is accompanied by augmentation of diffusion of oxygen in hypoxic fields of tissues. Regulating pressure of oxygen in an inhaled gas admixture and consequently, and in alveoluses, it is possible is dosed to enlarge its concentration in organism internal environments.

Breath by oxygen leads to excision of nitrogen from alveoluses, and alveolar O2 thus depends only on size O2 in an inhaled admixture, and also from level O2 and H2O in alveoluses (it more or less stable sizes, they practically do not variate at vicissitude of surrounding pressure). The augmentation of pressure of inhaled oxygen to 2, 3, 4ата and more causes lifting alveolar O2 to 1433, 2193, 2953mm Hg and more (at breath by pure oxygen alveolar O2-673 mm Hg, at breath by air under atmospheric pressure - 100mm Hg). Rising O2 in lungs conducts in turn to increase of a strain of oxygen in an arterial blood: to 1100-1400 mm Hg at 3 atm (initial arterial O2 90-95 mm Hg). In norm the oxygen capacity of blood compounds 20,3 about. %, from which 20 about. Oxygen % it is bound to haemoglobin, 0,3 about % are solved in plasma. In natural conditions the oxygen solved in plasma, in a quantitative sense has no big power value, and organism vital activity is provided with oxygen, transferable haemoglobin. Increase alveolar O2 causes rising arterial O2 and leads to sharp augmentation of quantity of the oxygen solved in plasma. Its lifting descends proportionally to pressure rising in an altitude chamber and practically is not circumscribed.

Quantity of the oxygen solved in a blood plasma, in direct ratio O2 in alveoluses. Rising of pressure of inhaled oxygen on 1 atm involves additional dissolution in 100 ml. Bloods около2,3 ml. Oxygen. Thereof breath by oxygen under pressure 3ата leads to additional dissolution in blood approximately 6об. Oxygen % that corresponds to normal consumption of oxygen by an organism in rest - its arteriovenous difference on oxygen. The oxyhemoglobin thus practically does not dissociate, since even without haemoglobin participation the oxygen capacity of blood here is quite sufficient life for maintenance (a phenomenon "life without blood"). Therefore at pressure of oxygen 3 atm the majority of tissues (the exception represents only a myocardium) entirely will satisfy the oxygen requirement only at the expense of its physically solved fraction. Therapeutic value of hyperbaric oxygenation also is based on it.

Ability considerably to enlarge oxygen capacity of blood allows to use hyperbaric oxygenation at morbid conditions when haemoglobin is in full or in part excluded from breath process, i.e. at anaemic (a massive blood loss) and toxic (venenatings with formation of a carboxyhemoglobin, a methemoglobin and a sulfhemoglobin) forms of an acute hemic hypoxia, and also for indemnification of metabolic requirements of an organism in oxygen at depression of volume of circulating blood and rate of a blood flow. Rising of a strain of oxygen in an arterial blood does not lead to strictly linear lifting O2 in tissues and cells. Degree of its increase in various organs depends on vascularization, conditions of an aboriginal blood flow, oxygen capacity of tissues, intensity of a metabolism, etc.

Enlarging oxygen capacity of vital mediums of an organism, hyperbaric oxygenation at the same time frames also certain conditions for oxygen deposition in tissues. Under shelter of hyperbaric oxygenation therefore probably longer deenergizing of blood supply head and a spinal cord that forms the establishment for application of this method in a cardiosurgery and neurosurgery.

At an assessment of reaction of an organism on an oxygen supertension it is necessary to distinguish the changes arising under influence to toxic doses of oxygen (kompensatorno-adaptive reactions), and the alterations testifying to its toxic action, arising at an oxygen overdosage.

At influence of therapeutic regimens of hyperbaric oxygenation natural change of some the vital functions of the organism, referred on restriction of excessive rising O2 in tissues is observed: breath thins and the bradycardia goes deep, becomes perceptible, warm outlier and an organ blood stream decrease, peripheric vascular resistance is enlarged etc. At the heart of the majority of these phenomena the boring of the parasympathetic centres lays arising at acclimatisation to a hyperoxia. Physiological reaction of an organism to rising O2 usually proceeds in certain sequences (scheme). The augmentation arterial O2 conducts to elimination of normal hypoxic activity of peripheric chemoceptors, depression of excitability of a respiratory centre and lung ventilation oppression. The last is accompanied by augmentation arterial CO2, causing dilating of veins of a brain. Simultaneously increase of a strain of oxygen in blood causes disturbance of dissociation of an oxyhemoglobin (level of the recovered haemoglobin in a venous blood decreases), raises acidity of blood, complicates transport of a carbon dioxide and hydrogen ions in brain tissues, including a respiratory centre. The hypercapnia conducts, in turn, to augmentation of minute volume of breath and a hyperventilation. As a result of CO2 in an arterial blood drops, brain pots are narrowed also an oxygen strain in brain tissues decreases. Type of hyperbaric oxygenation is therapy by the compressed air. At a number of forms of respiratory insufficiency the compressed air can be more effective, than pure oxygen. The hypercapnia thus usually does not accrue, and presence of nitrogen at alveoluses to some extent warns (or stops) oxygen damage of lungs, in particular development of atelectases.

Application

To application of hyperbaric oxygenation it is possible to present the basic indications as follows:

1. Acute and chronic oxygen insufficiency
2. Wet brain
3. the Auxiliary role at other kinds of treatment:
   • a potentiation of antiblastic action of alkylating preparations
   • in a complex with radial therapy for intensifying of a radiosensitiveness of cancerous tumours
   • at an extracorporal circulation for rising of efficacyy and safety of a method, etc
4. an intensive care Complex:
   • an acute heart failure
   • ischemic diseases of heart, nephroses, a liver, a brain, soft tissues
   • some forms of a shock, etc.
5. Respiratory insufficiency in the conditions of a nonperishable arterial anoxemia
6. At presence in an arterial blood of an appreciable admixing of a venous blood (the vein-arterial shunt at congenital heart diseases)

Procedure and technics of application. The therapeutic regimen of hyperbaric oxygenation in most cases consists of pressure 2-3 atm at an exposition 1-2 hours. Observance of the specified norms gives not only the maximum medical effect, but also practically excludes development of the expressed forms of an oxygen intoxication. Hyperbaric oxygenation is carried out in an altitude chamber, i.e. in the pot tightly isolating gas medium concluded in it from surrounding atmosphere and a supplied life-support system, and also the device on prevention and liquidation of failures.

The design of a medical altitude chamber in certain degree is caused by its special-purpose designation. There are two basic types of chambers for hyperbaric oxygenation - single and many-placed medical altitude chambers, in the last except one or several patients, there are attendants. Such chambers recently almost have completely refused, since the medical personnel is in them within all working day, thus "accumulating" toxic influence of oxygen when patients are in an altitude chamber 1-2 hours.

Besides, there are altitude chambers for a banking, and also altitude chambers of various designs for the experimental purposes. Single and many-placed chambers essentially differ: on structure of gas medium (in single usually - oxygen, in many-placed - air or other respiratory admixtures), to design features, equipment, operation etc.

Working pressure in single altitude chambers to 3-4 atm. The patient immediately breathes the gas medium (oxygen) framing pressure. Therefore there is no necessity necessarily to apply respiratory equipment, and medical effect in some cases, for example at the patients having wounds and ulcers, owing to direct action of oxygen for a traumatic surface decreases.

To destination single chambers part on chambers for adults, newborns and children till 1 year, and also for radial therapy of oncologic patients. Distinguish mobile (established in ambulance cars), portable (used in field conditions) and stationary single altitude chambers. The last place in sample hospital buildings, their equipment and operation are simple, the number of attendants is insignificant.

Many-placed altitude chambers on volume not less than 3000 litres with a working pressure to 10 kgs/see They consist of two or more compartments, one of which plays a role of a sluice and can be used for an orifice and an exit from the chamber during a session of hyperbaric oxygenation and at carrying out of salvage operations. Gas medium of a many-placed altitude chamber, as a rule, is air (oxygen for breath of patients is brought independently through a mask or an endotracheal tube). Equipment of many-placed medical altitude chambers depends on their appointment. In therapeutic chambers where the intensive care and resuscitation is spent, the equipment for artificial ventilation of the lungs is established, hypothermias, etc. the Altitude chamber-operational consists of two compartments - preoperative and operational. The first serves as a sluice for an orifice in operational at a supertension, for placing of necessary surgical toolkit and the instrumentation. Unlike altitude chambers of other appointment, in an altitude chamber-operational the big demands are shown to sterility of air, frequency rate of ventilation. In an altitude chamber there is an operating table (with the hydraulic elevating device filled with solution of Glycerinum), the narcotic apparatus and the apparatus of artificial ventilation of the lungs, the artificial circulation apparatus etc. the Operating lamp should be in explosion-proof execution.

Considering high partial pressure of oxygen, from an altitude chamber in case of a fire, the special attention it is necessary to turn an impediment of fast evacuation of humans on safety precautions. All equipment for functional researches (the electrocardiograph, an electroencephalograph) and other necessary apparatus (e.g., the defibrillator, an electroknife) take places out of an altitude chamber. In an altitude chamber there are only electrodes and gauges which join the special guard bridged by a cable through the pressure-seal connector with specified equipment. Considering, that all elements of an altitude chamber are executed from metal, the special demands are shown to isolation of electrical uptakes in an altitude chamber. The use in an altitude chamber of combustible materials, the stuffs accumulating a static electricity Is forbidden. In an altitude chamber it is impossible to apply explosive Anesthetics Ether, Cyclopropanum, etc. In it fire-prevention devices - the "rain" equipment and water fire engines should be provided.

Difficulty of a choice inhalation and narcotics for application in the conditions of hyperbaric oxygenation is caused by augmentation of fire danger of gas medium in a pressure-surgical. As a result of the spent researches it has been taped, that in the conditions of hyperbaric oxygenation possibility of ignition and, especially, a detonation gas of narcotic admixtures in the concentrations applied to a narcosis, much less, than in the usual. This results from the fact that concentration necessary for a narcosis (at conservation of a partial strain of a steam on which the narcotic effect depends) anaesthetising materials decreases proportionally to pressure rising in a pressure-surgical, i.e. gas a narcotic admixture which in usual conditions can come nearer to stoichiometric, under a supertension becomes a poor admixture.

It is considered, that the admixtures containing not less 4 % of combustible material, are ignited. Concentration of steams of the anaesthetising materials, necessary for carrying out of a mononarcosis in the conditions of a pressure-surgical from 2 atm and above, never reaches 4 %.

At observance of all safety precautions regulations the altitude chamber - operational can be used practically at all kinds of surgical interventions. Except separate many-placed altitude chambers, the so-called decompression systems consisting of several big chambers bound among themselves of different function in some cases are framed.

The dimensions of the therapeutic chamber (70 м3) allow to place in it 4 lying and 8сидячих patients and 2-3 humans of attendants. In the surgical chamber (70 м3) can there is a brigade from 8-10 humans. Successful application of hyperbaric oxygenation depends on a choice of optimum medical regimens, training of attendants to work in the chamber, the organisation of system of maintenance service, etc.

Possible complications. At long action of oxygen educe decompensated the reactions, showing functional and structural disturbances in various systems and organs. It is accepted to excrete 2 basic forms of an oxygen intoxication - acute and chronic (subacute). The acute venenating arises at a short-term exposition concerning oxygen high pressures (3 atm and above). To a lesion it is most subject a CNS, therefore this form designate as neurotoxic or convulsive. Signs of an oxygen intoxication appear through the certain season. Duration of this stage of latency extremely variable also is subject to influence of many factors. Them first of all concern: individual sensitivity to oxygen, temperature and humidity of environment, concentration CO2 in inhaled gas, emotional and physical exercises, a condition a CNS, an initial oxygen regimen of an organism and so forth

Initial toxic action of oxygen on a cell, apparently, is bound to an inhibition of respiratory enzymes and with accumulation of peroxides of the lipids causing damage of cellular structures. The most sensitive to oxygen are fermental systems of SH-bunch. The excessive augmentation of oxygen in a cell leads to change of a metabolism in a cycle tricarboxylic acids, to disturbance of synthesis of high-energy phosphatic bonds and to formation of free radicals. As the earliest objective signs of educing acute oxygen insufficiency consider changes an EEG (appearance of the nonperishable and plural locuses of convulsive activity) and an electrocardiogram (change of a voltage of a teeth and warm conductivity), and also sphygmus and breath increase. The preconvulsive stage of an acute oxygen poisoning shows vegetative disturbances (a tachycardia, a nausea, giddiness, disturbance of sight, paresthesia, difficulty and increase of breath, etc.) And local muscular twitchings (especially in range of eyelids, labiums, forehead).

Then there are the generalised tonic and clonic cramps proceeding as a classical epilepsy. At oxygen poisoning first signs it is necessary to effect decompression and to relay the victim to breath by air. When it is possible, transfer of the victim into breath by air should be spent even before pressure decrease. The chronic oxygen intoxication is possible at long, sometimes repeated, influence of small pressure of oxygen. Leaders thus are changes of lungs - the pulmonary form of an intoxication. First signs of a chronic pulmonary intoxication, as a rule, are bound to stimulating action of oxygen on the top respiratory tracts: a hyperemia, a mucosa swelling, a burning sensation, dryness in a mouth and other unpleasant sensations. Further the traheo-bronchitis joins them (a pain behind a breast bone, dry tussis, breath increase, rise in temperature) and a pneumonia. Roentgenologically intensifying of a pulmonary drawing, atelectases (the last consider pathognomic as a sign of this form of an intoxication) becomes perceptible. At timely cancellation of oxygen of any consequences neither that, nor other form of an intoxication does not abandon.

Classification of complications at hyperbaric oxygenation (are located on frequency of occurrence)

1. Functional disorders of an Eustachian tube and a middle ear:
   • I degree - an obstruction of ears
   • II degree - insignificant pains in ears
   • III degree - an obstruction and strong pains in ears
2. An exacerbation of chronic diseases and a condition after the tolerated operations:
   • Motorial disturbing
   • Giddiness
   • Discomfort
   • Pains in the field of heart
   • Pains in extremities
   • Pains in a postoperative wound
   • Vomiting
   • A headache
   • Lifting of a BP more than 170 mm Hg
3. Pathological influence hyperbaric oxygenation:
   • Intensifying, bleeding renewal
   • An epileptiform attack
   • An oxygen intoxication
   • A baro-otitis
   • A claustrophobia

To 1 bunch: to brake these implications were observed at patients with an ENT-pathology: a vasculomotor, subatrophic rhinitis, a pharyngitis, adenoides, tortuosity of a nasal septum. Disorders were eliminated by a softening of conditions of technics of carrying out of sessions (a time stopping of a compression, shunt of pressure on 0,1 atm, the subsequent ladder-shaped compression and decompression).

The factors causing disorders of 2 bunches, are psychoemotional, painful (at transportation and a rearrangement), physical and adaptic stress. For the prevention or levelling of its negative influence it is necessary to spend the purposeful differentiated medicamental therapy. So, for putting off of a painful syndrome before a session to the patient introduced analgetics, for the disturbing prevention - 1-2 ml. Seduxenum or Droperidolum, at a hyperthermia - antipyretics (analginum, Dimedrol, aminazine), at BP lifting - antihypertensives. The patient of a reanimation profile with available functional disorders to a session spent a corrective intensive care to stabilise indicators of vital functions of an organism: maintenance of passableness of pneumatic pathes, a stomach and bladder evac, cupping of a painful syndrome. In need of a session course continued infusional therapy. Cardiologic patients should take with themselves on a session Nitroglycerinum, and the patient with diabetes - Saccharum slice.

Carrying out of the corrective differentiated therapy compounded with profile unit allows to avoid in most cases functional disorders during hyperbaric oxygenation; for putting off of these complications sometimes was to resort to a repeated purge of the chamber during a session enough, to pressure decrease in an altitude chamber on 0,1-0,2 atm, in some cases to reduce duration of a session, and only in one case (the expressed discomfort, delicacy, a sweating) was necessary to interrupt a session.

It is necessary to name 3 bunch of complications "true" as they are bound immediately to negative influence of supertension О2.

Preventive maintenance of complications

As is known, oxygen at normal and especially at a supertension can have damaging an effect on lungs, causing a boring of respiratory tracts with overflow of capillars, a thickening of alveolar membranes, intersticial and intra-alveolar an edema and microatelectases. Observed thus morphological and functional changes are similar with so it is named by "a shock lung".

The most effective method of preventive maintenance of the named complications inflating of lungs is represented at spontaneous breath under constant positive pressure in pneumatic pathes or at artificial ventilation of the lungs with positive pressure in the end of an expiration.

The physiological effect of breath on an expiration is bound to resistance, first of all, with an expanding of lungs that enriches ventilating - a perfused interrelation and reduces intrapulmonic shunting. The augmentation of a diffusive surface of lungs, and also depression intersticial intra-alveolar an edema leads to depression alveolarly - a capillary gradient.

Use of artificial breath with positive pressure upon an expiration probably only at the patients who are under a narcosis or in extremely grave condition, also is interfaced to dangers of the complications caused both an intubation of a trachea, and apparatus ventilation of the lungs. At the patients who are on independent breath, we suggest to use building resistance on an expiration by means of the pouch from polyethylene.

On a neck of the patient by means of soft lock foam tapes the polyethylene package in which angles two tubes are pasted is fixed. One serves for additional giving of oxygen to a head of the patient and provides excess of pressure in the pouch, peer 5-10 sm. Water against the general pressure in an altitude chamber, and another is connected to the shutter to an aerotonometer which allows to watch size of framed pressure in the pouch and shunts its possible excess.

It has been thus noticed, that application of independent breath under constant positive pressure upon an expiration during sessions of hyperbaric oxygenation allows to avoid disturbances of mechanics of the breath, usually strengthening to 3 session, and provides longer and expressed effect, in particular higher and nonperishable oxygenation after a session.

Contraindications for work in the conditions of an oxygen supertension

For preventive maintenance of toxic action of oxygen on the medical personnel the medical control and selection of experts for work under a supertension is very important.

The basic points of offers are more low resulted. Selection and inspection of the experts involved for work in a medical altitude chamber descends in constantly reacting medical commission under presidency of the doctor-barophysiologist to the subsequent trial compression and sensitivity check to breath by pure oxygen.

Taking into account character of activity each expert passes inspection at the neuropathologist, the therapist, the oculist, the otolaryngologist, the surgeon and the stomatologist on the basis of preliminary spent is functional-laboratory researches.

At removal of the decision on the admission to work under pressure at neurologic inspection by contraindications organic lesions a CNS, an epilepsy, mental diseases and disorders are: a psychopathy, a claustrophobia, neurosises and neuritises, and also residual the phenomena of the occluded brain injuries. The question on suitability to works under pressure for the persons, suffering a chronic radiculitis in a remission stage is strictly individual solved. The general condition, influence of disease on the basic work in usual conditions, and also frequency of exacerbations in flow of year is considered.

Contraindication at ophthalmologic inspection is any disease of eyes conducting to nonperishable disturbance of function of sight at change of pressure in an altitude chamber. Especially it concerns persons with the raised ophthalmotonus, amotio of a retina of an eye and at visual acuity more low 0,5. The admission to works in an altitude chamber of persons with the lowered visual acuity is carried out taking into account a kind of work, level of light exposure of a workplace and pressure size. At research of an internals the attention is given to the tolerated diseases of organs of a circulation, breath, digestion. Revealing in bronchuses of lumens of bronchiectasises with deformation of the bronchuses leading in the conditions of a supertension to occurrence of a barotrauma of lungs (a breakage of tissues of a lung with the subsequent aeroembolism of the vital organs) is especially important. The decision on the admission to work of persons with the raised BP is born after 1-2 months of observation over fluctuations of pressure in the course of work in an altitude chamber. At the admission adhere to following parametres of a BP: systolic - not above 140 mm Hg and not more low 100mm Hg, diastolic - not above 85 mm Hg and not more low 60mm Hg at the sphygmus peer of 50-90 impacts in minute

Organic diseases of heart, it is not dependent on indemnification degree, and also the idiopathic hypertensia and a vascular hypotension are the basic contraindications. The decision on the admission of the persons, a stomach suffering by a peptic ulcer and a duodenum is very cautiously made; in all cases are considered not only X-ray inspection data, but also the general condition and duration of the seasons between exacerbations. Otolaryngologic selection of experts passes on the basis of research of a barofunction of an ear by a long aerotonometer, a purge a cylinder, a catheterization of an ear and an otoscopy during swallowing. The assessment of degree of a barofunction of an ear after carrying out of a trial compression is defined on a tympanic membrane condition. The barofunction of I degree is characterised by absence of any changes from pots of a membrane, II degree - an ill-defined hyperemia of pots of the top opuses of a tympanic membrane and on a course of the handle of a hammer; Barofunction of III degree - sharp reddening of a tympanic membrane without hemorrhages; IY degrees a-intensive hyperemia of pots of a tympanic membrane with hemorrhages.

To work under a high pressure chronic otites, chronic eustachitises with a barofunction III or IY degrees and disturbance of function of a vestibular mechanism are considered as contraindication. Experts at whom barofunction IY of degree is established are not supposed to work. At III degree the individual regimen of a compression is selected. At selection of experts by the surgeon the special attention addresses on presence of a chronic lymphadenitis, a widespread varicose phlebectasia, hernias. In the presence of hernias the question on the admission can be solved only after surgical treatment. Easy forms of a hemorrhoids with individual bleeding ganglions are not absolute contraindication to work under pressure, serious forms of a hemorrhoids with frequent bleedings, with the phenomena of abaissement of a mucous rectum and hemorrhoidal ganglions is absolute contraindication to work.

At survey of women by the doctor-gynecologist by absolute contraindications the dysmenorrhea and pregnancy are.

Apparently from the resulted data, the majority of observable complications of hyperbaric oxygenation have functional character, can be prognosticated and warned. It is necessary to give the special attention to technics of carrying out of the first sessions in which course to test features of a barofunction of Eustachian tubes, reactions to hyperbaric oxygenation, hemodynamic and breath, that at timely revealing of pathological alterations allows to introduce corrective amendments in technics of carrying out of sessions. Important also carrying out of the presession medicamental therapy referred on elimination of available functional alterations, and also special selection and preparation of the personnel for work under an oxygen supertension. Teamwork of the doctor-giperbarista with doctors of profile units will allow to compound the rational program of individual presession preparation for each patient. Such approach allows to dilate indications to hyperbaric oxygenation and, accordingly, to reduce the list of contraindications.