oxygen therapy

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OXYGEN THERAPY

A NEW report from Scotland on oxygen therapywill be welcomed in many quarters: its carefully arguedrecommendations reflect the breadth and depth of thefour years of inquiries that have gone into the docu-ment.

Inspired oxygen concentrations of between 24%and 38% are recommended in the treatment of patientswith chronic respiratory disease.2 This concentrationof oxygen provides, in most cases, an adequate increasein arterial oxygen tension without the risk of carbon-dioxide retention. High concentrations of oxygen arerequired in the treatment of such conditions as pul-monary oedema, pneumonia, shock, and carbon-mon-oxide poisoning. Cheap, disposable, and efficient masksare now available for both forms of oxygen therapy.Blood-gas monitoring is highly desirable in all patientsreceiving oxygen in hospital, since it is the only way ofminimising the dangers of oxygen toxicity. Some of thecommittee’s recommendations are, of course, based onreasonable assumption rather than scientific evidence,and perhaps a good example of this is the administra-tion of high concentrations of oxygen to patients withmyocardial infarction.3 A controlled trial of oxygentherapy in myocardial infarction is obviously requiredto establish the truth.

The suggested routine use of low concentrations ofoxygen in patients with pre-existing respiratory diseaseafter upper abdominal surgery seems logical, although,in some industrial areas, a counsel of perfection. Thequestion of optimum oxygenation in shock is one forwhich there is no clearcut answer at the moment.Correction of existing hypoxxmia is undoubtedlybeneficial, but experimental and clinical evidence tosupport the use of hyperoxia (including hyperbaricoxygen) is slender. If criticism can be levelled at the

report at all, it might be to suggest greater attention tothe subject of oxygen therapy in surgical and anaestheticpractice. The complexity of apparatus for oxygenadministration fully justifies the recommendation thatthe post of " gas technician " be established in all majorteaching hospitals. As an interim measure, simpleleaflets explaining the practical principles of oxygentherapy should be readily available at various siteswithin the hospital.A survey carried out under the auspices of the com-

mittee showed that only 1 patient in every 3000 receivedoxygen in general practice, whether the practice wasurban or rural. Difficulties arose in the supply andservicing of oxygen equipment; and it was clear thatless than 50% of general practitioners used oxygen inthe treatment of emergencies, and in urban practiceonly 20% of doctors carried oxygen themselves. Aworking party was required to tackle the practical prob-lems of the supply and transport of oxygen in domi-ciliary practice. Liaison with the ambulance serviceswould clearly improve the handling of emergencies.Oxygen administration did not seem to be indicated

as a routine in all women in labour-only when there1. Uses and Dangers of Oxygen Therapy. Report of a Sub-Committee

of the Standing Medical Advisory Committee. Scottish Home andHealth Department, Scottish Health Services Council. Edinburgh:H. M. Stationery Office. 1969. Pp. 101. 9s. 6d.

2. Campbell, E. J. M. Lancet, 1960, ii, 10.3. See ibid. 1969, ii, 525.

were other maternal indications for it. Perhaps a sur-prising conclusion to the non-specialised observer isthat there was little evidence for the value of oxygen infetal distress. As to the neonatal period, the committeesupports the continued evaluation of hyperbaric oxy-gen in the treatment of asphyxia and confirms theneed for strict surveillance of the administration of highconcentrations of oxygen over long periods to infantswith respiratory distress.

Air travel raises special problems for those withcardiorespiratory disease and severe anaemia. Specialsupplies of oxygen can readily be provided by airlineauthorities.

In resuscitation, the important point is thatoxygen plays a secondary role to adequate ventilationby the most rapid method available, usually therescuer’s own expired air. Oxygen should be intro-duced as soon as possible thereafter, since most patientsrequiring resuscitation are seriously hypoxasmic. Thebag-and-mask apparatus is judged superior to auto-matic cycling ventilators and should be carried by everyprofessional rescuer (i.e., doctors, nurses, ambulancemen, and first-aid workers). A simple modification canbe added to this system to permit the administrationof oxygen. In resuscitation after carbon-monoxide

poisoning, although a mixture of carbon dioxide andoxygen is more suitable than pure oxygen, the latteris recommended as a first-aid measure, since thereare practical difficulties in training non-medical per-sons to diagnose this specific form of gaseous poison-ing. Hyperbaric oxygen is the most efficient treatmentfor coal-gas poisoning.

Reports such as this are of real value only when theyare seriously discussed by authoritative bodies. It isto be hoped that the clearcut practical recommenda-tions made here will receive prompt attention andaction.

PERSISTENCE OF TREPONEMES AND THEINFECTIVITY TEST IN SYPHILIS

TREPONEME-LIKE structures have been seen in the

inguinal lymph-nodes, aqueous humour, and cere-

brospinal fluid of patients treated with penicillin forlate or latent syphilis.’ These observations raised the

question whether these forms are, in fact, Treponemapallidum, and, if so, whether they are viable organisms,still capable of producing disease.

Several methods have been used to look for theseforms. Dark-field examination in experienced hands isreliable in identifying T. pallidum in the early lesions ofsyphilis; and if motile forms of typical appearance canbe found in material from patients with late syphilis,this would seem to be very suggestive evidence.Examination of fixed material by silver staining orfluorescent antibody techniques is less certain. Moti-

lity cannot be assessed, fixation may change the mor-phological appearances, and artefacts may sometimesbe very misleading.2 3 Fluorescein-labelled syphilitic

1. See Lancet, 1965, i, 693.2. Wilkinson, A. E. Trans. ophthal. Soc. U.K. 1968, 88, 2513. Montenegro, E. N. R., Nicol, W. G. Smith, J. L. Am. J. Ophthal.

1969, 68, 197.