- Email: [email protected]
AN EVALUATION OF THE EFFICIENCY OF FACE MASKS IN THE RESUSCITATION OF NEWBORN INFANTS
207 DISCUSSION are two explanations for the improvement observed non-actively treated patients-a placebo effect and the greater consistency and involvement in management. The placebo effect has been extensively studied. There is an inevitable tendency to recruit for asthma trials children and parents who are well motivated and compliant rather than the difficult patients. This tendency biases the results towards agreater placebo response,7 but would not completely explain the degree and persistence of the improvement in our patients. The improvement in the details of management is also important. Patients taking part in trials are seen regularly and frequently, usually by the same doctor, who has a special interest in asthma and a personal interest in a small number of specially selected patients. The gain by the doctor has been seen as a negative factor, potentially causing pressure to recruit unsuitable patients against their best interest, but there are positive aspects to participation, in view of the special attention and treatment provided. In our trials the time spent at each visit was necessarily longer than that for a
Hospital Practice
There
in
routine clinic attendance; parents were able to air their questions and anxieties fully. Generally discussions about asthma, the various medications, and their best use gave the patients and families greater insight into the disease and our view of management. The children were also given extra training on optimum techniques in the use of their inhalation devices and their technique was checked at subsequent visits. This practice led to a better understanding by the family of the child’s asthma, the medication, and its best use. The better use of treatment gave the families more confidence in their ability to cope and to control symptoms, which, together with the prompts from the doctor and the use of reminders like diary cards improved compliance. Being selected for the "special" trial group increased their motivation and also improved compliance. Specialist clinics often achieve better results in the management of chronic disorders such as asthma because they devote more time to detail than is possible in a general clinic. In our experience, asthma treatment prescribed by the referring doctors is usually appropriate and does not require any change, but the patients need careful training and advice on optimum use of treatment. However, even in the apparently optimum setting of a special clinic devoted to asthma, it is possible to achieve additional benefit by participation in a clinical trial. Of course ideally all clinics should be conducted as trials are, with attention to every minute detail and each patient given the time he or she requires, but in practice this is not possible. The additional motivation of doctor and patient during a trial provides advantages which should be considered in the risk/benefit equation used by ethics committees. In view of our observations, the last word could perhaps be left to Claude Bernard, the 19th century French physiologist.8 "Among the experiments that may be tried on man, those that can only harm are forbidden; those that are innocent are permissible; and those that may do good are
frequent
obligatory." V’e thank co-authors of these studies: Dr P. J. Cooper, Dr J. Darbyshire, Dr M. H. Frame, Dr E. N. Hey, Mr A. J. Nunn, Dr J. F. Price, Prof J. F. Soothill, and Dr M. W. Turner.
Correspondence
should be addressed
to
J.
0. W.
REFERENCES 1 Rees J Clinical trials
in
asthma Br MedJ
1983; 287:
376-77
AN EVALUATION OF THE EFFICIENCY OF FACE MASKS IN THE RESUSCITATION OF NEWBORN INFANTS CHARLOTTE PALME BERTIL NYSTRÖM RAGNAR TUNELL
Departments of Pediatrics and Clinical Microbiology, Huddinge University Hospital, Huddinge, Sweden Five widely used neonatal face masks were tested on 44 babies for their efficiency in terms of degree of leakage and ease of cleaning. Leakage was measured indirectly. The mean peak pressure of ten breaths when babies were ventilated from a respirator via a mask was recorded; a low pressure was taken to indicate leakage. A triangular moulded rubber mask (’Rendell-Baker’) leaked most and a circular silicone rubber mask (’Laerdal’) leaked least. The ease of cleaning the masks was measured as the amount of bacteria removed from contaminated masks by wiping them with 70% ethanol. The Laerdal mask was significantly more effectively cleaned than the others. It is also the only one of the masks tested that can be boiled and autoclaved.
Summary
INTRODUCTION
APPROXIMATELY 5% of newborn infants need resuscitation at birth.’ Most infants improve rapidly with ventilation.2 If correctly administered ventilation by bag-andmask rapidly provides adequate expansion of the lungs without exposing the infant to the possible hazards of intubation.3 Apart from a self-expanding bag of suitable size with properly functioning valves, the most critical part of the equipment is the face mask. The efficiency of the face mask depends on the ease of adjusting the mask to the face and thus avoiding too much leakage, even when used by somebody with little experience; its construction (whether or not the parts will come apart during use); and the ease with which the mask can be cleaned after use. To find a face mask which can be recommended for developed as well as developing countries, we have tested five neonatal resuscitation face masks for their efficiency. SUBJECTS
AND METHODS
The Face Masks Five masks were tested (fig 1): 1. The ’Ambu OA’ mask (Ambu International, Copenhagen, Denmark) consists of a central transparent dome surrounded by a circular foam-rubber ring which is covered with a thin layer of rubber. One size is used for all newborn babies.
JH. The child and clinical research. Lancet 1984, ii: 510-12. College of Physicians of London. Guidelines on the practice of ethics committees in medical research London: RCP, 1984. 4. Cooper PJ, Darbyshire J, Nunn AJ, Warner JO. A controlled trial of oral hyposensitisation in pollen asthma and rhinitis in children Clin Allergy 1984; 14: 2. Pearn 3. Royal
541-50 5 Warner JO, Price
JF, Soothill JF, Hey EN. Controlled trial of hyposensitisation to Dermatophagoides pteronyssinus in children with asthma. Lancet 1978, ii: 912-15 6. Price JF, Warner JO, Hey EN, Turner MW, Soothill JF. A controlled trial of hyposensitisation with adsorbed tyrosine Dermatophagoides pteronyssinus antigen in childhood asthma: in vivo aspects. Clin Allergy 1984; 14: 209-19. 7. Gowdey CW. A guide to the Pharmacology of placebos. Canad Med Ass J 1983; 128: 921-25 8. Bernard C.
Trans, Green HC. An introduction Dover Publications, 1957.
to
the
study of experimental medicine.
208 2. The ’Rendell-Baker’ mask (Warne, Hampshire, England) is a solid triangular rubber mask shaped to fit the baby’s face. Size no 0 is recommended for use on all newborn infants, and size no 1 is for somewhat older infants. We tested size 0 on infants with birthweights below 4 kg and size no 1 on bigger infants. 3. The ’Bennet’ mask (Puritan-Bennet, Los Angeles, California, USA) consists of a central plastic dome surrounded by a double circular complex silicone rubber flap. Size no 1 is recommended for extremely premature infants and size no 2 for other newborn babies. We tested size 2 on babies weighing less than 4 kg and size 3 on
bigger infants.
’
’Laerdal’ mask (Laerdal, Stavanger, Norway) is a soft silicone rubber mask with an inward-curving circular 0 is recommended for extremely premature infants and size 1 for other newborn babies. We tested size 1. 5. The ’Ohio’ mask (Ohio Medical Products, Madison, Wisconsin, USA) is a soft double-walled one-piece rubber mask, pear-shaped and filled with air. There are two sizes: we tested the "premature" on babies with birth-weights below 2500 g and the "new-born" size on bigger infants. 4. The
new
one-piece flap. Size
Fig
1-The five different face masks.
Patients The masks were tested on 44 healthy, spontaneously breathing infants during the first few days after birth. 13 babies had birthweights of 4-5 kg (mean 4410 g), 15 babies weighed 3-4 kg (mean 3550 g), 10 weighed 2-3 kg (mean 2260 g), and 6 babies weighed 1-2
kg (mean
1540
Determination
g).
of Leakage
An indirect method of determining the degree of leakage was used. A ’Babylog 2’ ventilator (Dragerwerk AG, Lubeck, Germany) provided air under intermittent positive pressure. This ventilator is pressure-limited and time-cycled with a constant gas flow of 8 litres/min. The respiratory rate was set at 60/min and the inspiratory time was 0’ 5 s. This gives a maximum gas volume of 66 ml/cycle. The comparatively low gas flow compensates for the effect on the pressure of quiet, spontaneous breathing, but not for the effect of vigorous breathing or leakage. In the absence of leakage, and during quiet breathing, the peak pressure recorded inside the mask is the same as the maximum presure indicated by the manometer on the ventilator. The mean inspiratory pressure of ten inspirations for each child and mask were compared, and the differences were considered to correspond to differences in leakage. A peak pressure of 30 cm of water was used with infants with birth weights of 3000 g or more, and 20 cm of water in the case of smaller babies. The pressure inside the masks was measured by a ’SiemensElema’ pressure transducer (Siemens-Elema, Stockholm, Sweden) and recorded on a ’Siemens-Elema’ mingograph no 803.
Strrcdy Protocol Forty-four medical students and nurses without training in resuscitation took part in the study. They were first instructed on a Laerdal baby mannequin, using a bag and the five different masks. Each student then tested the masks on a healthy child. The student held the mask with one hand as in bag-and-mask ventilation and the air was delivered under pressure by the ventilator. The mask pressure was recorded in ten cycles for each of the five different masks. The order of the masks was randomised according to a randomisation table. The students were not able to see the results of the recording during the test. Each child was subjected to all five masks. Only recordings made during quiet breathing were accepted.
Fig 2-Mean peak pressures often cycles of ventilation for birth weights 1000-3000 g.
babies with
A = 1000 = 2000 g; A = 2000-3000 g.
Cleaning the Masks Two series of ten masks of each kind (ie, 100 masks) were contaminated with Streptococcus faecalis (NCTC 10927)
suspensions
containing
3x106-3 x 108 micro-organisms/ml
amniotic fluid. All the masks were contaminated with 0 - 2 ml of the bacterial suspension and dried at room temperature for lh. The masks in one series were shaken in 1% peptone water for 5 min. The peptone water was then filtered through a 0 - 45 pm ’Millipore’ filter with a hydrophobic edge. The filter was placed on a blood agar plate and incubated at 37°C for 48 h. The masks in the other series were thoroughly wiped with 70% ethanol after inoculation but before being shaken in peptone water. The number of bacteria retrieved from the masks in the first series was less than one-tenth of that in the inoculum-ie, the method gave less than a tenfold loss. The ease of cleaning the masks is expressed as the inactivation factor, which is the quotient of the number of bacteria on uncleaned divided by the number of bacteria on cleaned masks. A high inactivation factor thus means that the mask is easy to clean.
Statistical Methods and Ethical Approval Differences were calculated by the use of Wilcoxon’s signed rank Informed consent was given by all the parents and the study was approved by the ethical committee at Huddinge Hospital. test.
RESULTS
Dead Space
Leakage
Dead space was measured by filling the masks with water when they were held tightly against the face of a baby mannequin whose mouth was closed. The volume of water used for filling the mask was measured.
The mean peak pressure often cycles of ventilation for each child and mask can be seen in figs 2 and 3. For all babies with a birth weight of 3000 g or more the Rendell-Baker mask gave a significantly lower peak pressure
209
TABLE I-PROPORTION OF MASKS FOR WHICH THE PEAK PRESSURE IS
LESS THAN
80% OF THE
INTENDED PRESSURE .
TABLE II-DEAD SPACE OF FACE MASKS AND SIZE OF MASK OFTEN L’SED FOR BABIES OF DIFFERENT BIRTH WEIGHTS
Fig 3-Mean peak pressures often cycles of ventilation for babies with birth weights 3000 - 5000 g. &Dgr;=3000-4000 g; A=4000-5000 g.
and thus a higher degree of leakage than the Ambu (p<0. 01), Laerdal (p<0.01), and Ohio (p<0.01) Bennet (p<0.01), a and the Laerdal mask masks; gave significantly higher pressure and thus a smaller degree of leakage than the Ambu (p<0. 01), Bennet (p<0 . 01), Ohio (p<0 . 02), and RendellBaker (p<0. 01) masks. For the babies weighing less than 3000 g the Rendell-Baker mask leaked more than did the Ambu (p<0. 01), Laerdal (p<0.01), and Ohio (p<0-02) masks. No other diff-erences could be found. Among the masks with high leakage (ie, for which the peak pressure was less than 80% of the intended pressure) the Rendell-Baker mask showed high leakage in 50% of the tests, whereas the Laerdal mask did so in only 2%. Dead Space There are considerable differences between different masks
(table 11).
Clearring the Masks (Fig 4) The inactivation factors for the Laerdal mask were higher than those of the Bennet (p<0. 05), Rendell-Baker (p<0 .01), Ambu (p<0.01), and Ohio (p<0.01) masks. The Bennet mask inactivation factor was higher than that of the Ambu mask
(p<0.1).
We
regard the determination of leakage as the most important part of our tests. If leakage is high, the pressure reached is insufficient to exceed the opening pressure in the lungs. Earlier investigations have shown that in the resuscitation of newborn infants an opening pressure of 30
cm
H20 (range
20-40
cm
H20
approximately) is required to aerate non-expanded lungs. 3,5,6 These
earlier results were obtained by ventilating newborn infants via an endotracheal tube at 40 breaths/minute with an insufflation time of 1 s or less. When self-expanding bags with relatively small gas volumes are used the insufflation time will be 0.5-1s.
asphyxiated
Mean;
70% ethanol.
I range.
The present investigation shows that a soft circular mask which adapts its shape to the contours of the baby’s face leaks
DISCUSSION
approximately
Fig 4-Inactivation factors for cleaning by wiping with
less than a moulded triangular mask. A new face mask made of silicone rubber (Laerdal mask) leaked least and may thus be recommended for use by persons without much training in resuscitation. With the hard, moulded mask (Rendell-Baker) 80% of the estimated opening pressure was achieved in only 22 of the 44 babies investigated and seems to be the most difficult mask to use. The mechanical properties of the face mask are also of importance in the assessment of efficiency. Masks made of two separate pieces may come apart during resuscitation and be totally ineffective. Three types of masks (Laerdal, Ohio, and Rendell-Baker) are made in one piece and are thus preferable to the other types in this respect.
210 The amount of dead space varied considerably from mask mask. The Rendell-Baker and the Bennet masks had the smallest (7 ml) and the Ambu mask the largest (25 ml) dead space. The importance of dead space in the resuscitation of newborn infants is unknown, but from a theoretical point of view a small dead space may be of advantage. Further study is needed to clarify this point. One important cause of neonatal problems is infections acquired in connection with birth and transmitted between neonates.’ Asphyxia is often combined with prenatal infections and it is thus important to have a face mask that can be cleaned effectively. In most developing countries the only available method of sterilisation is boiling after mechanical cleaning. The only face mask that can be boiled (and autoclaved) is the Laerdal. The Laerdal silicone rubber mask was the one that was cleaned most effectively by wiping with
to
ethanol. The new silicone rubber circular mask from Laerdal is thus better than the other masks as far as leakage and cleaning are concerned. The smallest dead space was found with the
Rendell-Baker mask which, however, leaked more than the other masks, and in the Bennet mask. The importance of dead space in resuscitation is unclear and needs further
investigation. Correspondence should be addressed to R. T., Department of Paediatrics B57, Huddmgs Hospital, S-141 86 Huddinge, Sweden.
REFERENCES 1
Valman HB The first year of life Resuscitation of the newborn Br Med J 1343-45
2
Henriksson P, Milerad J, Tunell R, Varendh G Resuscitation of asphyxiated neonates Lakartidningen 1978, 75: 121-24 Hull D Lung expansion and ventilation during resuscitation of asphyxiated newborn infants J Pediatr 1969, 75: 47-58 1979 National Conference on Cardiopulmonary Resuscitation and Emergency Cardiac Care Advanced Cardiac Life Support for Neonates JAMA 1980; 244: 495-500 Boon AW, Milner AD, Hopkin IE. Lung expansion, tidal exchange, and formation of the functional residual capacity during resucitation of asphyxiated neonates J
3. 4 5
1979, ii:
Pediatr 1979, 95: 1031-36. AW, Milner AD, Hopkin IE. Physiological responses of the newborn infant to resuscitation Arch Dis Child 1979, 54: 492-98 7 Ferer J, Taylor PM, Gezon HM Pseudomonas Aeruginosa epidemic traced to delivery room resuscitators N Engl J Med 1967, 276: 991-96.
6 Boon
world are
leaves, barks, animal hairs, animal horns, cow droppings, soil, salt, and ash, singly or in combination. Also, many modern
Point of View
of the active ingredients extracted from plants long by traditional healers eg, quinine and reserpine. What is generally less appreciated is that most cultures have a strong tradition of preventive health care and that many items in the traditional pharmacopoeia are used for prophylaxis against illness
drugs consist used
WHY DO PEOPLE LIKE MEDICINES? A PERSPECTIVE FROM AFRICA
Nigeria,
lecture broadcast by the Federal Radio Corporation of Dr A. Adeniyi-Jones, a former medical consultant to the United Nations, said that the excessive prescription of medicinal preparations by doctors and self-medication by patients have "made the taking of medicines in general the greatest form of drug abuse in Nigeria". Gross wastage and inappropriate prescription of drugs, not insufficient funding alone, are major factors contributing to the inadequate health services in many countries both south and north of the Equator, It is impossible to quantify the unwanted health problems or unnecessary deaths which occur in developing countries as a result of misuse of drugs, but the following two examples of what are probably widespread practices may suffice as an indication of its magnitude. On my first visit to an African hospital I noted that a course of penicillin injections had been prescribed by the hospital matron for a man with a closed fracture of the forearm; he had not received any analgesics. And "Good health begins with right eating", declares a poster issued by the Jamaican Nutritional Education Programme, yet many poor families continue to spend as much on purchasing traditional and modern medicines as on food. The reasons for this unhealthy cycle of overprescription by health workers and excessive consumption by patients are undoubtedly complex and difficult to unravel even in a particular locality. Nevertheless, I believe that some pertinent general observations can be made about the interaction between health workers (of all types), patients, and drug usage in poor countries. I will concentrate on the misconceptions which develop from cultural, historical, and economic reasons and which contribute to the negative impact of drug usage on health standards in developing countries. IN
a
misfortune. Public health is not a new concern for traditional healers in societies where interactions between people, alive or dead (but not without influence), are held to be responsible for many forms of illness, accidents, injuries, social failure, or infertility. In fact, "Prevention is better than cure" is an almost universal saying. In North and West Africa, there is a Hausa proverb which says that "Prevention is better than medicine", yet to a casual observer the Hausas seem to be extremely interested in taking medicines. This is because Hausas are so used to taking medicines which are thought to fortify the body or promote fertility or social success, that they readily ascribe, in an arbitrary manner, these same properties to modern, imported drugs which the manufacturers recommend for some other, specific, and limited curative purpose. In many African cultures it is believed that the White races must possess powerful medicines, regular ingestion of which confers apparent immunity to local diseases and, more importantly, material riches and technical superiority. Sometimes the White man’s drugs are taken for a more immediate impact rather than for prevention. In a rural hospital in North Nigeria, I met a man with a violent urticarial reaction. Close questioning revealed that the only unusual item he had ingested recently was dapsone, taken because it made him feel good and increased his sexual potency. Dapsone was freely available at the weekly market in his village along with roots, leaves, and dried animal entrails. Other modern drugs are also rapidly being incorporated into the day-to-day prescriptions of these healers, as found in a study of traditional practitioners in Ibadan, a large African city in Nigeria, (Una Maclean, Magical Medicine, Pelican). It is common in Africa for a patient whose complaints have been cured by a course of antibiotics to ask for more of the same medicine to ensure a continuing state of good health. He will not readily accept the advice that, good food or some other action will be more beneficial at much lower cost. In many instances, traditional healers or private practitioners, for a fee-for-service basis, will be only too happy to comply with the villager’s request. or
J.-M. MICHEL Rural Health Program, Advenist Health Services in PMB 2054, Jos, Plateau State, Nigeria
-
recent
Nigeria,
INFLUENCE OF TRADITION OF PREVENTIVE HEALTH
Almost everything ever discovered in the natural world seems to have been used at some time or other as a means of trying to alleviate human pain and suffering. Commonly used in different parts of the
INFLUENCE OF POOR COMMUNICATION BETWEEN PATIENT AND WESTERN-TRAINED DOCTOR I do not mean to imply that traditional healers have only medicinal preparations to offer patients. They often have vast local knowledge
.
Hospital Practice
There
in
routine clinic attendance; parents were able to air their questions and anxieties fully. Generally discussions about asthma, the various medications, and their best use gave the patients and families greater insight into the disease and our view of management. The children were also given extra training on optimum techniques in the use of their inhalation devices and their technique was checked at subsequent visits. This practice led to a better understanding by the family of the child’s asthma, the medication, and its best use. The better use of treatment gave the families more confidence in their ability to cope and to control symptoms, which, together with the prompts from the doctor and the use of reminders like diary cards improved compliance. Being selected for the "special" trial group increased their motivation and also improved compliance. Specialist clinics often achieve better results in the management of chronic disorders such as asthma because they devote more time to detail than is possible in a general clinic. In our experience, asthma treatment prescribed by the referring doctors is usually appropriate and does not require any change, but the patients need careful training and advice on optimum use of treatment. However, even in the apparently optimum setting of a special clinic devoted to asthma, it is possible to achieve additional benefit by participation in a clinical trial. Of course ideally all clinics should be conducted as trials are, with attention to every minute detail and each patient given the time he or she requires, but in practice this is not possible. The additional motivation of doctor and patient during a trial provides advantages which should be considered in the risk/benefit equation used by ethics committees. In view of our observations, the last word could perhaps be left to Claude Bernard, the 19th century French physiologist.8 "Among the experiments that may be tried on man, those that can only harm are forbidden; those that are innocent are permissible; and those that may do good are
frequent
obligatory." V’e thank co-authors of these studies: Dr P. J. Cooper, Dr J. Darbyshire, Dr M. H. Frame, Dr E. N. Hey, Mr A. J. Nunn, Dr J. F. Price, Prof J. F. Soothill, and Dr M. W. Turner.
Correspondence
should be addressed
to
J.
0. W.
REFERENCES 1 Rees J Clinical trials
in
asthma Br MedJ
1983; 287:
376-77
AN EVALUATION OF THE EFFICIENCY OF FACE MASKS IN THE RESUSCITATION OF NEWBORN INFANTS CHARLOTTE PALME BERTIL NYSTRÖM RAGNAR TUNELL
Departments of Pediatrics and Clinical Microbiology, Huddinge University Hospital, Huddinge, Sweden Five widely used neonatal face masks were tested on 44 babies for their efficiency in terms of degree of leakage and ease of cleaning. Leakage was measured indirectly. The mean peak pressure of ten breaths when babies were ventilated from a respirator via a mask was recorded; a low pressure was taken to indicate leakage. A triangular moulded rubber mask (’Rendell-Baker’) leaked most and a circular silicone rubber mask (’Laerdal’) leaked least. The ease of cleaning the masks was measured as the amount of bacteria removed from contaminated masks by wiping them with 70% ethanol. The Laerdal mask was significantly more effectively cleaned than the others. It is also the only one of the masks tested that can be boiled and autoclaved.
Summary
INTRODUCTION
APPROXIMATELY 5% of newborn infants need resuscitation at birth.’ Most infants improve rapidly with ventilation.2 If correctly administered ventilation by bag-andmask rapidly provides adequate expansion of the lungs without exposing the infant to the possible hazards of intubation.3 Apart from a self-expanding bag of suitable size with properly functioning valves, the most critical part of the equipment is the face mask. The efficiency of the face mask depends on the ease of adjusting the mask to the face and thus avoiding too much leakage, even when used by somebody with little experience; its construction (whether or not the parts will come apart during use); and the ease with which the mask can be cleaned after use. To find a face mask which can be recommended for developed as well as developing countries, we have tested five neonatal resuscitation face masks for their efficiency. SUBJECTS
AND METHODS
The Face Masks Five masks were tested (fig 1): 1. The ’Ambu OA’ mask (Ambu International, Copenhagen, Denmark) consists of a central transparent dome surrounded by a circular foam-rubber ring which is covered with a thin layer of rubber. One size is used for all newborn babies.
JH. The child and clinical research. Lancet 1984, ii: 510-12. College of Physicians of London. Guidelines on the practice of ethics committees in medical research London: RCP, 1984. 4. Cooper PJ, Darbyshire J, Nunn AJ, Warner JO. A controlled trial of oral hyposensitisation in pollen asthma and rhinitis in children Clin Allergy 1984; 14: 2. Pearn 3. Royal
541-50 5 Warner JO, Price
JF, Soothill JF, Hey EN. Controlled trial of hyposensitisation to Dermatophagoides pteronyssinus in children with asthma. Lancet 1978, ii: 912-15 6. Price JF, Warner JO, Hey EN, Turner MW, Soothill JF. A controlled trial of hyposensitisation with adsorbed tyrosine Dermatophagoides pteronyssinus antigen in childhood asthma: in vivo aspects. Clin Allergy 1984; 14: 209-19. 7. Gowdey CW. A guide to the Pharmacology of placebos. Canad Med Ass J 1983; 128: 921-25 8. Bernard C.
Trans, Green HC. An introduction Dover Publications, 1957.
to
the
study of experimental medicine.
208 2. The ’Rendell-Baker’ mask (Warne, Hampshire, England) is a solid triangular rubber mask shaped to fit the baby’s face. Size no 0 is recommended for use on all newborn infants, and size no 1 is for somewhat older infants. We tested size 0 on infants with birthweights below 4 kg and size no 1 on bigger infants. 3. The ’Bennet’ mask (Puritan-Bennet, Los Angeles, California, USA) consists of a central plastic dome surrounded by a double circular complex silicone rubber flap. Size no 1 is recommended for extremely premature infants and size no 2 for other newborn babies. We tested size 2 on babies weighing less than 4 kg and size 3 on
bigger infants.
’
’Laerdal’ mask (Laerdal, Stavanger, Norway) is a soft silicone rubber mask with an inward-curving circular 0 is recommended for extremely premature infants and size 1 for other newborn babies. We tested size 1. 5. The ’Ohio’ mask (Ohio Medical Products, Madison, Wisconsin, USA) is a soft double-walled one-piece rubber mask, pear-shaped and filled with air. There are two sizes: we tested the "premature" on babies with birth-weights below 2500 g and the "new-born" size on bigger infants. 4. The
new
one-piece flap. Size
Fig
1-The five different face masks.
Patients The masks were tested on 44 healthy, spontaneously breathing infants during the first few days after birth. 13 babies had birthweights of 4-5 kg (mean 4410 g), 15 babies weighed 3-4 kg (mean 3550 g), 10 weighed 2-3 kg (mean 2260 g), and 6 babies weighed 1-2
kg (mean
1540
Determination
g).
of Leakage
An indirect method of determining the degree of leakage was used. A ’Babylog 2’ ventilator (Dragerwerk AG, Lubeck, Germany) provided air under intermittent positive pressure. This ventilator is pressure-limited and time-cycled with a constant gas flow of 8 litres/min. The respiratory rate was set at 60/min and the inspiratory time was 0’ 5 s. This gives a maximum gas volume of 66 ml/cycle. The comparatively low gas flow compensates for the effect on the pressure of quiet, spontaneous breathing, but not for the effect of vigorous breathing or leakage. In the absence of leakage, and during quiet breathing, the peak pressure recorded inside the mask is the same as the maximum presure indicated by the manometer on the ventilator. The mean inspiratory pressure of ten inspirations for each child and mask were compared, and the differences were considered to correspond to differences in leakage. A peak pressure of 30 cm of water was used with infants with birth weights of 3000 g or more, and 20 cm of water in the case of smaller babies. The pressure inside the masks was measured by a ’SiemensElema’ pressure transducer (Siemens-Elema, Stockholm, Sweden) and recorded on a ’Siemens-Elema’ mingograph no 803.
Strrcdy Protocol Forty-four medical students and nurses without training in resuscitation took part in the study. They were first instructed on a Laerdal baby mannequin, using a bag and the five different masks. Each student then tested the masks on a healthy child. The student held the mask with one hand as in bag-and-mask ventilation and the air was delivered under pressure by the ventilator. The mask pressure was recorded in ten cycles for each of the five different masks. The order of the masks was randomised according to a randomisation table. The students were not able to see the results of the recording during the test. Each child was subjected to all five masks. Only recordings made during quiet breathing were accepted.
Fig 2-Mean peak pressures often cycles of ventilation for birth weights 1000-3000 g.
babies with
A = 1000 = 2000 g; A = 2000-3000 g.
Cleaning the Masks Two series of ten masks of each kind (ie, 100 masks) were contaminated with Streptococcus faecalis (NCTC 10927)
suspensions
containing
3x106-3 x 108 micro-organisms/ml
amniotic fluid. All the masks were contaminated with 0 - 2 ml of the bacterial suspension and dried at room temperature for lh. The masks in one series were shaken in 1% peptone water for 5 min. The peptone water was then filtered through a 0 - 45 pm ’Millipore’ filter with a hydrophobic edge. The filter was placed on a blood agar plate and incubated at 37°C for 48 h. The masks in the other series were thoroughly wiped with 70% ethanol after inoculation but before being shaken in peptone water. The number of bacteria retrieved from the masks in the first series was less than one-tenth of that in the inoculum-ie, the method gave less than a tenfold loss. The ease of cleaning the masks is expressed as the inactivation factor, which is the quotient of the number of bacteria on uncleaned divided by the number of bacteria on cleaned masks. A high inactivation factor thus means that the mask is easy to clean.
Statistical Methods and Ethical Approval Differences were calculated by the use of Wilcoxon’s signed rank Informed consent was given by all the parents and the study was approved by the ethical committee at Huddinge Hospital. test.
RESULTS
Dead Space
Leakage
Dead space was measured by filling the masks with water when they were held tightly against the face of a baby mannequin whose mouth was closed. The volume of water used for filling the mask was measured.
The mean peak pressure often cycles of ventilation for each child and mask can be seen in figs 2 and 3. For all babies with a birth weight of 3000 g or more the Rendell-Baker mask gave a significantly lower peak pressure
209
TABLE I-PROPORTION OF MASKS FOR WHICH THE PEAK PRESSURE IS
LESS THAN
80% OF THE
INTENDED PRESSURE .
TABLE II-DEAD SPACE OF FACE MASKS AND SIZE OF MASK OFTEN L’SED FOR BABIES OF DIFFERENT BIRTH WEIGHTS
Fig 3-Mean peak pressures often cycles of ventilation for babies with birth weights 3000 - 5000 g. &Dgr;=3000-4000 g; A=4000-5000 g.
and thus a higher degree of leakage than the Ambu (p<0. 01), Laerdal (p<0.01), and Ohio (p<0.01) Bennet (p<0.01), a and the Laerdal mask masks; gave significantly higher pressure and thus a smaller degree of leakage than the Ambu (p<0. 01), Bennet (p<0 . 01), Ohio (p<0 . 02), and RendellBaker (p<0. 01) masks. For the babies weighing less than 3000 g the Rendell-Baker mask leaked more than did the Ambu (p<0. 01), Laerdal (p<0.01), and Ohio (p<0-02) masks. No other diff-erences could be found. Among the masks with high leakage (ie, for which the peak pressure was less than 80% of the intended pressure) the Rendell-Baker mask showed high leakage in 50% of the tests, whereas the Laerdal mask did so in only 2%. Dead Space There are considerable differences between different masks
(table 11).
Clearring the Masks (Fig 4) The inactivation factors for the Laerdal mask were higher than those of the Bennet (p<0. 05), Rendell-Baker (p<0 .01), Ambu (p<0.01), and Ohio (p<0.01) masks. The Bennet mask inactivation factor was higher than that of the Ambu mask
(p<0.1).
We
regard the determination of leakage as the most important part of our tests. If leakage is high, the pressure reached is insufficient to exceed the opening pressure in the lungs. Earlier investigations have shown that in the resuscitation of newborn infants an opening pressure of 30
cm
H20 (range
20-40
cm
H20
approximately) is required to aerate non-expanded lungs. 3,5,6 These
earlier results were obtained by ventilating newborn infants via an endotracheal tube at 40 breaths/minute with an insufflation time of 1 s or less. When self-expanding bags with relatively small gas volumes are used the insufflation time will be 0.5-1s.
asphyxiated
Mean;
70% ethanol.
I range.
The present investigation shows that a soft circular mask which adapts its shape to the contours of the baby’s face leaks
DISCUSSION
approximately
Fig 4-Inactivation factors for cleaning by wiping with
less than a moulded triangular mask. A new face mask made of silicone rubber (Laerdal mask) leaked least and may thus be recommended for use by persons without much training in resuscitation. With the hard, moulded mask (Rendell-Baker) 80% of the estimated opening pressure was achieved in only 22 of the 44 babies investigated and seems to be the most difficult mask to use. The mechanical properties of the face mask are also of importance in the assessment of efficiency. Masks made of two separate pieces may come apart during resuscitation and be totally ineffective. Three types of masks (Laerdal, Ohio, and Rendell-Baker) are made in one piece and are thus preferable to the other types in this respect.
210 The amount of dead space varied considerably from mask mask. The Rendell-Baker and the Bennet masks had the smallest (7 ml) and the Ambu mask the largest (25 ml) dead space. The importance of dead space in the resuscitation of newborn infants is unknown, but from a theoretical point of view a small dead space may be of advantage. Further study is needed to clarify this point. One important cause of neonatal problems is infections acquired in connection with birth and transmitted between neonates.’ Asphyxia is often combined with prenatal infections and it is thus important to have a face mask that can be cleaned effectively. In most developing countries the only available method of sterilisation is boiling after mechanical cleaning. The only face mask that can be boiled (and autoclaved) is the Laerdal. The Laerdal silicone rubber mask was the one that was cleaned most effectively by wiping with
to
ethanol. The new silicone rubber circular mask from Laerdal is thus better than the other masks as far as leakage and cleaning are concerned. The smallest dead space was found with the
Rendell-Baker mask which, however, leaked more than the other masks, and in the Bennet mask. The importance of dead space in resuscitation is unclear and needs further
investigation. Correspondence should be addressed to R. T., Department of Paediatrics B57, Huddmgs Hospital, S-141 86 Huddinge, Sweden.
REFERENCES 1
Valman HB The first year of life Resuscitation of the newborn Br Med J 1343-45
2
Henriksson P, Milerad J, Tunell R, Varendh G Resuscitation of asphyxiated neonates Lakartidningen 1978, 75: 121-24 Hull D Lung expansion and ventilation during resuscitation of asphyxiated newborn infants J Pediatr 1969, 75: 47-58 1979 National Conference on Cardiopulmonary Resuscitation and Emergency Cardiac Care Advanced Cardiac Life Support for Neonates JAMA 1980; 244: 495-500 Boon AW, Milner AD, Hopkin IE. Lung expansion, tidal exchange, and formation of the functional residual capacity during resucitation of asphyxiated neonates J
3. 4 5
1979, ii:
Pediatr 1979, 95: 1031-36. AW, Milner AD, Hopkin IE. Physiological responses of the newborn infant to resuscitation Arch Dis Child 1979, 54: 492-98 7 Ferer J, Taylor PM, Gezon HM Pseudomonas Aeruginosa epidemic traced to delivery room resuscitators N Engl J Med 1967, 276: 991-96.
6 Boon
world are
leaves, barks, animal hairs, animal horns, cow droppings, soil, salt, and ash, singly or in combination. Also, many modern
Point of View
of the active ingredients extracted from plants long by traditional healers eg, quinine and reserpine. What is generally less appreciated is that most cultures have a strong tradition of preventive health care and that many items in the traditional pharmacopoeia are used for prophylaxis against illness
drugs consist used
WHY DO PEOPLE LIKE MEDICINES? A PERSPECTIVE FROM AFRICA
Nigeria,
lecture broadcast by the Federal Radio Corporation of Dr A. Adeniyi-Jones, a former medical consultant to the United Nations, said that the excessive prescription of medicinal preparations by doctors and self-medication by patients have "made the taking of medicines in general the greatest form of drug abuse in Nigeria". Gross wastage and inappropriate prescription of drugs, not insufficient funding alone, are major factors contributing to the inadequate health services in many countries both south and north of the Equator, It is impossible to quantify the unwanted health problems or unnecessary deaths which occur in developing countries as a result of misuse of drugs, but the following two examples of what are probably widespread practices may suffice as an indication of its magnitude. On my first visit to an African hospital I noted that a course of penicillin injections had been prescribed by the hospital matron for a man with a closed fracture of the forearm; he had not received any analgesics. And "Good health begins with right eating", declares a poster issued by the Jamaican Nutritional Education Programme, yet many poor families continue to spend as much on purchasing traditional and modern medicines as on food. The reasons for this unhealthy cycle of overprescription by health workers and excessive consumption by patients are undoubtedly complex and difficult to unravel even in a particular locality. Nevertheless, I believe that some pertinent general observations can be made about the interaction between health workers (of all types), patients, and drug usage in poor countries. I will concentrate on the misconceptions which develop from cultural, historical, and economic reasons and which contribute to the negative impact of drug usage on health standards in developing countries. IN
a
misfortune. Public health is not a new concern for traditional healers in societies where interactions between people, alive or dead (but not without influence), are held to be responsible for many forms of illness, accidents, injuries, social failure, or infertility. In fact, "Prevention is better than cure" is an almost universal saying. In North and West Africa, there is a Hausa proverb which says that "Prevention is better than medicine", yet to a casual observer the Hausas seem to be extremely interested in taking medicines. This is because Hausas are so used to taking medicines which are thought to fortify the body or promote fertility or social success, that they readily ascribe, in an arbitrary manner, these same properties to modern, imported drugs which the manufacturers recommend for some other, specific, and limited curative purpose. In many African cultures it is believed that the White races must possess powerful medicines, regular ingestion of which confers apparent immunity to local diseases and, more importantly, material riches and technical superiority. Sometimes the White man’s drugs are taken for a more immediate impact rather than for prevention. In a rural hospital in North Nigeria, I met a man with a violent urticarial reaction. Close questioning revealed that the only unusual item he had ingested recently was dapsone, taken because it made him feel good and increased his sexual potency. Dapsone was freely available at the weekly market in his village along with roots, leaves, and dried animal entrails. Other modern drugs are also rapidly being incorporated into the day-to-day prescriptions of these healers, as found in a study of traditional practitioners in Ibadan, a large African city in Nigeria, (Una Maclean, Magical Medicine, Pelican). It is common in Africa for a patient whose complaints have been cured by a course of antibiotics to ask for more of the same medicine to ensure a continuing state of good health. He will not readily accept the advice that, good food or some other action will be more beneficial at much lower cost. In many instances, traditional healers or private practitioners, for a fee-for-service basis, will be only too happy to comply with the villager’s request. or
J.-M. MICHEL Rural Health Program, Advenist Health Services in PMB 2054, Jos, Plateau State, Nigeria
-
recent
Nigeria,
INFLUENCE OF TRADITION OF PREVENTIVE HEALTH
Almost everything ever discovered in the natural world seems to have been used at some time or other as a means of trying to alleviate human pain and suffering. Commonly used in different parts of the
INFLUENCE OF POOR COMMUNICATION BETWEEN PATIENT AND WESTERN-TRAINED DOCTOR I do not mean to imply that traditional healers have only medicinal preparations to offer patients. They often have vast local knowledge
.