RESPIRATORY
MEDICINE
(1999)
93,
46-51
Prescription
and usage of long-term oxygen
therapy in patients with chronic obstructive
pulmonary
disease in the Netherlands
M. J. KAMPELMACHER~, R. G. VAN KESTEREN*, G. P. J. ALSBACH+,
C. F. MELISSANT*, H. J. WYI?NE§, J. M. C. DOUZE” AND J.-W. J. LAMMERS*
Cenfre for Home Mechanical Ventilation, “Division of Infernal Medicine and Dermatology,
‘Division of Obstetrics and Gynaecology and *Department of Pulmonary Diseases,Heart Lung
Institute, University Hospital Ufrechf, and ‘Cenfre for Biosfafisfics, University of Ufrechf, Utrecht,
The Netherlands
Long-term oxygen therapy (LTOT) has been shown to improve survival in hypoxaemic patients with chronic
obstructive pulmonary disease (COPD). This has resulted in recommending the prescription of oxygen for at least
15 h day- ’ in most European countries.
In order to examine the prescription and usage of LTOT and to assess the adherence to international
recommendations for its prescription, a survey was set up in a random sample of clients of the largest oxygen
company in the Netherlands. After patients had been visited for an interview, additional postal surveyswere sent to
the physician who had prescribed LTOT and to the oxygen company.
For 175 COPD patients the mean oxygen prescription and mean oxygen usage were 15.6 f 5.8 and 14.1 & 6.8 h
day - ‘, respectively. In 62 patients (35%) oxygen was prescribed < 15 h day - ‘, more often by non-chest physicians
than by chest physicians (P<O.OOOl),and 91 patients (52%) used oxygen < 15 h day- ‘. Of 113 patients with a
prescription 2 15 h day - ‘, 39 (35%) used oxygen < 15 h day - ’ and 74 for 2 15 h day - ‘. The latter were prescribed
oxygen for more h day - i , had been longer on LTOT, had a higher resting flow rate, were prescribed a concentrator,
employed portable cylinders and used oxygen in public significantly more often than the former,
We conclude that in a selected group of LTOT patients with COPD both oxygen prescription and usage were
often inadequate, particularly if LTOT was prescribed by non-chest physicians.
RESPIR. MED.
(1999)
93,
46-51
Introduction
Long-term oxygen therapy (LTOT) has been shown to
improve survival in hypoxaemic patients with chronic
obstructive pulmonary disease (COPD) (1,2). As a result,
the American Thoracic Society and the European
Respiratory Society have issued recommendations for the
prescription of LTOT and in many countries prescription
guidelines have been formulated, which usually recommend
prescribing oxygen for at least 15 h day - ’ (3-5).
In 1992 some 6000 patients in the Netherlands were
prescribed LTOT and the number of LTOT patients per
100 000 inhabitants was one of the highest in Europe (6).
Nevertheless, national prescription guidelines have not been
Received 24 March 1998 and accepted in revised form
14 October 1998.
Correspondenceshould be addressedto M. J. Kampelmacher,
MD, PhD, Centre for Home MechanicalVentilation, HP C02.
410, University Hospital Utrecht, P. 0. Box 85500, 3508 GA
Utrecht, The Netherlands
0954-6111/99/010046+06
$12.0010
issued yet. In the same year the impression was created, by
both patients and oxygen companies, that the therapy was
often prescribed improperly. In addition, little was known
about oxygen usage and data on compliance were lacking.
On the basis of the literature compliance to therapy
was expected to be poor (7-11). Finally, factors affecting
compliance had not yet been extensively clarified.
The aims of this study were, therefore, to examine the
prescription and usage of LTOT in COPD patients, to
assesspatient compliance to the therapy and to analyse
the adherence to international recommendations for the
prescription of LTOT.
Methods
STUDY DESIGN
The patients of this study took party
set up in a sample of 2523 clients
company in the Netherlands (Hoek
the Netherlands) (12). After they
0
1999
in a survey which was
of the largest oxygen
Loos Co., Schiedam,
had been coded by
W. B. SAUNDERS COMPANY
LTD
OXYGEN
number, 138 1 patients were randomly chosen by computer.
Subsequently, patients were selected if they were at least
18 years, had a telephone connection and had possessed
oxygen equipment at home for at least 6 months.
Of the 895 patients who fulfilled these criteria, 341
(38%) refused to participate and 26 (3%) could not
take part for reasons of severe illness or early death. A
total of 528 patients, including 369 COPD patients, were
visited at home for an interview by a medical student.
Prior to the visit, the students had been trained in formulating the questions of a questionnaire and they had been
instructed that all questions had to be answered by the
patients themselves. At the end of the interview each
patient was asked for informed consent to send additional
postal surveys both to the physician who had prescribed
LTOT and to the oxygen company. This study was
approved by the Medical Ethics Committee of our
hospital.
DEFINITIONS
AND
MEASUREMENTS
PrePhy is the daily length of the treatment prescribed,
according to the physician. In the assessmentof the extent
to which physicians followed the international recommendations for LTOT prescription, a daily oxygen prescription 215h day-’ was defined as ‘adequate’, while a
prescription < 15 h day - i was considered as ‘inadequate’
(3,4X
As oxygen usage was not actually measured and reliable
data on this matter could not be obtained from the oxygen
company, daily oxygen usage was assumed to be as stated
by the patients (UsaPat). The one and only controlled
trial comparing oxygen with no oxygen in severe chronic
hypoxaemia showed that the minimum time for clinical
benefit was 15 h day - r (2). For this reason, patients using
LTOT for a minimum of 15 h day - ’ were defined as
‘effective’ users of treatment, while patients using it for
c15h day-’ were considered to be ‘ineffective’ users.
Patients who were prescribed oxygen for 2 15 h day - ’ and
who also used it for this number of hours were classified
as ‘compliant’. Those with a prescription of L 15 h day - ‘,
but who used oxygen for < 15 h day - ’ were classed as
‘non-compliant’.
DATA
ANALYSIS
Data analysis was performed and descriptive statistics
obtained using the SPSS/PC+program (SPSS Inc.,
Chicago, U.S.A.). Continuous values are reported as
mean 5 SD. Subgroups were compared by Mann-Whitney
U-tests for continuous variables, and by Fisher’s exact tests
in contingency tables for categorical variables. Linear
regression analysis was applied to relate UsaPat to PrePhy.
The physicians’ answers were supposed to represent the
prescription correctly and were, therefore, regarded as the
predicting variable. Two-sided tests were employed
throughout and a P-value of ~0.05 was considered
significant.
PRESCRIPTION AND USAGE IN COPD
PATIENTS
47
Results
For 175 COPD patients data on both oxygen prescription
and usage were available. Table 1 lists their characteristics and those of the 194 COPD patients who were
excluded because their doctors did not reply. No statistically significant differences were found between both
patient groups.
OXYGEN PRESCRIPTION
Apart from the fact that the number of daily hours of
oxygen prescribed was unknown to 52 patients (30%),
patients and physicians held different views on the daily
length prescribed (Table 2). A prescription 2 15 h day - i
was not related to age or mobility of the patients, the
number of follow-up visits or duration of LTOT. The
median flow rate prescribed was 1.O1min - ‘, both at rest,
during exercise and sleep. Sixty-three patients (36%) stated
that LTOT had mainly been prescribed for dyspnoea.
In 149 patients (85%) LTOT had been prescribed by a
chest physician, in 17 (10%) by a general practitioner (GP)
and in nine (5%) by an internist. GPs wrote prescriptions
more often than chest physicians on the basis of ‘if necessary’ (P<O.OOl). The latter prescribed oxygen more often
>15hday-’
than non-chest physicians (BO.001).
Usually the decision between an oxygen concentrator and
cylinders was left to the oxygen company. Liquid oxygen,
however, was only installed if prescribed by a physician.
OXYGEN USAGE
More than half of the patients used oxygen ~15 h day- ’
and 10 applied it only ‘if necessary’ (Table 2). For 175
patients the mean UsaPat and mean PrePhy were 14.1 &
6.8 and 15.6 f 5.8 h day- ‘, respectively, with the following relationship: UsaPat = 3.9 + 0.66 * PrePhy; P<O.OOl for
H,,P=l (Fig. 1). Although UsaPat increased with PrePhy,
increasing the length prescribed did not guarantee a usage
of 2 15 h day-‘. As compared to patients using ~15 h
day-‘, those using oxygen 2 15 h day- i had been prescribed LTOT more often L 15 h day - ’ than c 15 h day - ’
(P<O.OOl). This was done more frequently by chest
physicians than by non-chest physicians (P=O.O06), and
mainly for hypoxaemia rather than dyspnoea (P=O.O097).
In addition, patients who used oxygen 2 15 h day - ’ were
more often women (P=O.O19), used a concentrator more
frequently (P<O.OOl), had more complaints due to LTOT
(P=O.O04) and had been prescribed a higher flow rate at
rest (BO.001) than the patients who used it < 15 h day- ‘.
UsaPat-PrePhy was negative in 83 (47%) and positive in 47
patients (27%), and decreased with PrePhy. The number of
patients who used fewer daily hours than prescribed was
larger if oxygen was prescribed L 15 h day - ’ than if it was
prescribed < 15 h day - ’ (P=O.O023), and increased with
PrePhy (Fig. 2).
Of the 113 patients with an oxygen prescription of 2 15 h
day - ‘, 39 patients (35%) used oxygen < 15 h day - I and 74
for >15hday-‘.
The latter differed from the former with
48
M.
J. KAMPELMACI~ER
ET AL
1. Demographic and clinical data for the COPD patients who were included and for those
excluded because their physicians did not reply*
TABLE
Included
(n= 175)
Excluded
(n= 194)
12550
70.1 f 7.7
3.3 f 3.2
16.8 f 5.8
14.1 f 6.8
- 0.5 f 2.6
4.5 f 4.7
149 (85)
17 (10)
127 (73)
28 (16)
36 (21)
111 (63)
136:58
69.0 zt 9.7
3.9 f 3.5
16.5 f 7.3
12.8 zk8.0
- 1.0*4.4
4.3 * 4.5
166 (86)
21 (11)
135 (70)
35 (18)
50 (26)
126 (65)
Oxygen source
Cylinders
Concentrator
Liquid
Combination
Receiving portable cylinders
Using portable cylinders 2 1 week - i
144 (82)
22 (13)
7 (4)
2 (1)
112 (64)
35 (31)
157 (81)
25 (13)
9 (5)
3 (2)
114 (59)
39 (34)
Delivery device
Nasal prongs
Nasopharyngeal catheter
Cuffed nasal catheter
Transtracheal microcatheter
Oxygen mask
Other
157 (90)
9 (5)
4 (2)
2 (1)
1 (1)
2 (1)
166 (86)
17 (9)
5 (3)
3 (2)
90 (51)
18 (10)
66 (38)
81 (46)
81 (46)
105 (54)
14 (7)
70 (36)
74 (38)
77 (40)
Sex ratio (M:F)
Age (years)
Duration of LTOT (years)
Oxygen prescription (h day - ‘)
Oxygen usage (h day - ‘)
Overall compliance (h day- ‘)
Visits to physician (n yr - ‘)
Prescribed by chest physician
Prescribed by general practitioner
Ex-smokers
Smokers
Living alone
Needing help from other people
Complaints (61% had >one complaint)
Restricted autonomy
Duration of therapy
Shame
Oxygen source
Delivery device
3 (2)
*All data were provided by the patients. Values are presented either as mean f SD or as number of
patients with percentage in parentheses. None of the differences were statistically significant,
respect to the oxygen prescription and usage, duration of
LTOT, resting flow rate, and concentrator and portable
cylinder use (Table 3). There were, however, no differences in age, sex, reason for starting LTOT, prescribing
physician, the number of smokers, complaints due to the
treatment, reduction of dyspnoea following the start of
LTOT, living conditions or in the number of follow-up
visits between compliant and non-compliant patients, all of
whom had an oxygen prescription of 2 15 h day - ‘.
Discussion
This study demonstrates that in a selected group of LTOT
patients with COPD more than one-third of the physicians
who prescribed LTOT did not adhere to international
recommendations, more than half of the patients used
oxygen ineffectively, and almost half of the patients used it
for fewer daily hours than prescribed.
Inadequate prescription was probably caused by the
still-existing misconception that the therapy is aimed at
the symptomatic relief of breathlessness, and also by
non-adherence to the international recommendations
because physicians were apparently not aware of them.
The duration of the treatment prescribed was inadequate,
particularly if it was done by non-chest physicians.
This finding is consistent with several other studies
(10,13,14). In some European countries the prescription
of LTOT is, therefore, restricted to chest physicians
(15,16).
OXYGEN
TABLE2. Oxygen prescription (Pre) and oxygen usage (Usa)
according to physicians (Phy) and patients (Pat) (n= 175)*
Period
If necessary only
At night only
Continuously
Miscellaneous
Unknown
Daily hours
215
<I5
Unknown
PrePhy
PrePat
UsaPat
2 (1)
31 (18)
46 (26)
44 (25)
52 (30)
23 (13)
46 (26)
56 (32)
31 (18)
19 (11)
10 (6)
48 (27)
55 (31)
62 (35)
113 (65)
62 (35)
91 (52)
32 (18)
52 (30)
84 (48)
91 (52)
3
6
9
12
15
18
PATIENTS
49
60,
<8
Prescribeddaily hours
FIG. 2. Difference between the used (U) and prescribed
*Values are presented as numbers of patients with percentages in parentheses.
I
0
PRESCRIPTION AND USAGE IN COPD
21
24
Prescription (h day-‘)
FIG. 1. Individual and average relationship between daily
oxygen usage, according to the patient, and daily oxygen
prescription, as given by the physician, in 175 COPD
patients (r=0.56; P<O.OOl). Individual data points are
shown. Solid lines represent the mean f SD. The horizontal dashed line distinguishes effective ( 2 15 h day- i) from
ineffective (< 15 h day - ‘) users; the vertical dashed line
distinguishes adequate (2 15 h day - ‘) from inadequate
(C 15 h day - ‘) prescriptions.
The prescription was also inadequate with regard to
the oxygen flow rates. Most patients were prescribed
l.Olmin-‘? irrespective of their activity level. Such a flow
rate is quite low and probably not adequate even at rest
(17). To keep them well oxygenated, patients frequently
need extra oxygen during sleep and exercise (18). Hence,
titration of the oxygen flow rate during sleep and exerciseis
recommended to prevent serious hypoxaemia (3,4).
Furthermore, both the content of the prescription and
the way in which it was given to the patients were frequently
inadequate, as 30% of the patients was unaware of the
number of daily hours prescribed, and patients and their
physicians held different opinions on the prescribed daily
(P) daily hours of oxygen therapy per patient, in relation
to the prescribed duration of treatment in 175 patients
(Mantel-Heanszel test: P=O.O18). The number of patients
is given above each bar. (0, U<P; W, U=P; El, U>P.)
length of the treatment. Physicians should make every effort
to give their patients adequate instructions, preferably
orally as well as in writing.
It is very plausible that ineffective oxygen usage was
caused by the trouble induced by the treatment, like
restricted autonomy and complaints due to the oxygen
equipment (12). Due to the local density and accessibility of
patients and because of the reimbursement policies in the
Netherlands the oxygen companies supplied most patients
with oxygen cylinders until recently.
In addition, ineffective usage may also have been caused
by inadequate prescription. Several studies, however, have
shown a comparable oxygen usage, even when patients had
been prescribed oxygen for 2 15 h day- ’ (11,19,20). In
accordance with other studies, our study showed that
effective oxygen usage was positively related to disease
severity, LTOT duration, concentrator use, oxygen usage
during indoor movements and to the resting oxygen flow
rate, all of which may be explained by progressive hypoxaemia (9,19). Oxygen usage also increased with the daily
hours prescribed. Although important, prescribing enough
daily hours was no guarantee for effective usage since, even
when oxygen was prescribed continuously, seven out of 35
patients still followed this advice for < 15 h day - i. Furthermore, oxygen usage improved when LTOT had been prescribed by chest physicians. The latter is in keeping with a
study in which more than 90% of the 560 patients, who were
prescribed oxygen for a mean of 19 h day- i by chest
physicians only, reported using oxygen for 2 15 h day - ’
(21). The present findings demonstrate that non-compliance
is a serious problem in COPD patients with LTOT. Poor
compliance may have been due to a relatively good clinical
condition, insufficient motivation and encouragement of
patients, and to inconvenience induced by the treatment.
Oxygen usage is a problem for many patients, particularly
when moving in and around the house, going out and
meeting other people. The latter is probably related to the
weight of the portable cylinders and to stigmatization
caused by the nasal cannulae. Portable liquid oxygen may
50
M. J. KAMPELMACHER
ET AL.
TABLE 3. Differences between compliant patients (n=74) using oxygen 2 15 h day - i, and non-
compliant patients (n = 39) using oxygen < 15 h day - ‘, all of whom had been prescribed oxygen for
215 h day-‘*
Prescription according to physicians (h day- i)
Prescription according to patients (h day - ‘)
Usage according to patients (h day - ‘)
Duration of LTOT (years)
Resting flow rate (1min - ‘)
Urged to use more (h day- *)
Concentrator use
Use of portable cylinders
Use in public
Use during transfers at home
Use when being visited
Use when visiting
*Values are given either as mean f
SD
Compliant
Non-compliant
P-value
19.5 & 3.8
19.9 f 4.0
20.1 f 3.9
3.4 f 2.8
1.2 f 0.6
l/74 (1)
16/74 (22)
48/59 (81)
59/70 (84)
50/73 (69)
66/74 (89)
39159 (66)
17.9 & 3.2
13.7 & 3.6
9.9 f 3.6
2.4 f 2.1
0.7 * 0.7
4139 (10)
2139 (5)
13124 (54)
19/31 (61)
5139 (13)
6139 (15)
2133 (6)
0.018
<O*OOl
<O.OOl
0.048
0.002
0.047
0.013
0.01
0.011
<0~0001
<0~0001
<0~0001
or numbers of patients with percentages in parentheses.
facilitate oxygen usage during activities and thereby
increase daily oxygen usage (22,23). Given the negative
influence of shame on compliance, the latter may be
improved by transtracheal oxygen therapy in selected
patients (24).
The fact that only 10% of the non-compliant patients
were urged to use oxygen for more hours a day casts doubt
on the effectiveness of the follow-up visits. Encouragement
and close supervision of patients, as well as assistance of
specially trained nurses forming part of a home care
programme are recommended to improve compliance
(20,25-27).
Being part of a survey which was set up in a random
sample of LTOT patients, this study has several limitations.
Similar to most other studies in this field, it was retrospective. Consequently, selection bias may have occurred. Only
59% of the 895 selected patients were interviewed. In
addition, 194 (53%) of the 369 COPD patients had to be
excluded because of a lack of doctors’ postal reply.
Although these patients did not differ from the participants,
their physicians prescriptions might have. It was not possible to ascertain whether the latter were lessinterested in the
field, and thus probably less informed and not adhering to
prescription guidelines, or well informed but simply too
busy to respond. Furthermore, the information on each
patient was limited. Data on lung function, blood gasesand
medication were, for example, absent. Finally, the oxygen
usage was not actually measured and reliable data on this
matter could not be obtained from the oxygen company. As
it is well known that patients tend to overestimate their
oxygen consumption, oxygen usage and the number of
compliant patients in our population are likely to be even
lessthan reported (10,19). Nevertheless, the outcome of this
study is considered to be representative of the situation in
the Netherlands.
We conclude that in a selected group of LTOT patients
with COPD both oxygen prescription and usage were
inadequate, particularly if this treatment was initiated by
non-chest physicians. We recommend that LTOT should be
prescribed by chest physicians, who should educate and
encourage their patients in an attempt to gain effective use
of oxygen therapy. To improve compliance, the assistance
of specially trained nurses forming part of a home-care
programme may be helpful and the oxygen equipment
should become more acceptable to patients.
Acknowledgements
This study was supported by research grant No. 28-1721
from the Dutch Praeventiefonds. We would like to thank
the staff of the Hoek Loos Co., Schiedam, for their expert
help and cooperation in this study, and the patients for
volunteering to participate in this study.
References
1. Nocturnal Oxygen Therapy Trial Group. Continuous
or nocturnal oxygen therapy in hypoxaemic chronic
obstructive airways disease: a clinical trial. Ann Intern
Med 1980; 93: 391-398.
2. Medical Research Council Working Party. Long-term
domiciliary oxygen therapy in chronic hypoxic car
pulmonale complicating chronic bronchitis and
emphysema. Lancet 1981; 1: 681-686.
3. Siafakas NM, Vermeire P, Pride NB, et al. Optimal
assessment and management of chronic obstructive
pulmonary disease (COPD). A consensus statement of
the European Respiratory Society (ERS). Eur Respir J
1995; 8: 1398-1420.
4. American Thoracic Society. Standards for the diagnosis and care of patients with chronic obstructive
pulmonary disease. Am J Respir Crit Care Med 1995;
152 (Suppl.): 77-120.
OXYGEN
5. Fauroux B, Howard P, Muir JF. Home treatment for
chronic respiratory insufficiency: the situation in
Europe in 1992. Eur Respir J 1994; 7: 1721-1726.
6. Viskum K. Organisation of professional care services
with special reference to LTOT. Mona/& Arch Chest
Dis 1993; 48: 453457.
7. Evans TW, Waterhouse J, Howard P. Clinical experience with the oxygen concentrator. Br Med J 1983; 287:
459461.
8. Desrues B, Lecoq C et I’Association d’Aide aux
Insuffisants Respiratoires de Bretagne, Prescription et
observance de l’oxygenotherapie de longue duree. Rev
Mal Resp 1989; 6: 237-241.
9. Vergeret J, Tunon de Lara M, Douvier JJ, Freour P,
Cardinaud JP, Courty G, Taytard A. Compliance of
COPD patients with long term oxygen therapy. Eur J
Respir Dis 1986; 69 (Suppl. 146): 421425.
10. Walshaw MK, Lim R, Evans CC, Hind CRK. Prescription of oxygen concentrators for long term oxygen
treatment: reassessmentin one district. Br Med J 1988;
297: 1030-1032.
11. Vergeret J, Brambilla C, Mournier L. Portable oxygen
therapy: use and benefit in hypoxaemic COPD patients
on long-term oxygen therapy. Eur Respir J 1989; 2:
20-25.
12. Kampelmacher MJ, van Kesteren RG, Alsbach GPJ,
Melissant CF, Wynne HJ, Douze JMC, Lammers
J-WJ. Characteristics and complaints of patients prescribed long-term oxygen therapy in the Netherlands.
Respir Med 1998; 92: 70-75.
13. Bellone A, De Angelis G, Toietta P, Aliprandi PL,
Castelli C, Raineri M. Who has to prescribe long-term
oxygen therapy? Eur Respir J 1994; I (Suppl. 18): 242.
14. Dilworth JP, Higgs CMB, Jones PA, White RJ.
Prescription of oxygen concentrators: adherence to
published guidelines. Thorax 1989; 44: 576578.
15. Gorecka D, Sliwinski P, Zielinski J. Adherence to entry
criteria and one year experience of long-term oxygen
therapy in Poland. Eur Respir J 1992; 5: 848-852.
16. Morrison D, Skwarski K, MacNee W. Review of the
prescription of domiciliary long term oxygen therapy in
Scotland. Thorax 1995; 50: 1103-l 105.
PRESCRJPTION AND USAGE IN
COPD PATIENTS
5I
17. Waterhouse JC, Nichol J, Howard P. Survey on
domiciliary oxygen by concentrator in England and
Wales. Eur Respir J 7: 2021-2025.
18. Sliwinski P, Lagosz M, Gorecka D, Zielinski J. The
adequacy of oxygenation in COPD patients undergoing
long-term oxygen therapy assessedby pulse oximetry at
home. Eur Respir J 1994; 7: 27Lc278.
19. P&pin J-L, Barjoux CE, Deschaux C, Brambilla C.
Long-term oxygen therapy at home. Compliance with
medical prescription and effective use of therapy. Chest
1996; 109: 11441150.
20. Frey J-G, Kaelin R-M, De Werra M, Jordan B,
Tschopp J-M. Oxysgenotherapie continue a domicile.
Etude de l’observance des extracteurs d’oxygene apres
un programme d’enseignement. Rev MaI Resp 1992; 9:
301-305.
21. Strom K, Boe J, The Swedish Society of Chest
Medicine. Quality assessment and predictors of survival in long-term domiciliary oxygen therapy. Eur
Respir J 1991; 4: 50-58.
22. Lock SH, Blower G, Prynne M, Wedzicha JA. Comparison of liquid and gaseous oxygen for domiciliary
portable use. Thorax 1992; 47: 98-100.
23. Leach RM, Davidson AC, Chinn S, Twort CH,
Cameron IR, Bateman NT. Portable liquid oxygen and
exercise ability in severe respiratory disability. Thorax
1992; 47: 781-789.
24. Kampelmacher MJ, Deenstra M, van Kesteren RG,
Melissant CF, Douze JMC, Lammers J-WJ. Transtracheal oxygen therapy: an effective and safe alternative to nasal oxygen administration. Eur Respir J 1997;
lo: 828-833.
25. Restrick LJ, Paul EA, Braid GM, Cullinan P,
Moore-Gillon J, Wedzicha JA. Assessment and follow
up of patients prescribed long term oxygen treatment.
Thorax 1993; 48: 708-713.
26. Ley P. Improving patients’ understanding, recall,
satisfaction and compliance. In: Broom AK, ed. Health
Psychologwy. London: Chapman & Hall, 1989: 74102.
27. Rudkin S. Home support for patients on long-term
oxygen therapy. Nursing Times 1996; 92: 34-35.