VETERANS HEALTH ADMINISTRATION CLINICAL PRACTICE GUIDELINE FOR
THE MANAGEMENT OF COPD OR ASTHMA
Outpatient Management of COPD: Long-Term Oxygen Therapy (A5)
In chronic obstructive pulmonary disease (COPD), clients with hypoxemia
and cor pulmonale, long-term oxygen therapy (LTOT) may increase the life
span by 6 to 7 years. Mortality is reduced in patients with chronic hypoxemia
when oxygen is administered for > 12 hours daily and greater survival benefits
have been shown with continuous oxygen administration.
A. Patient with COPD on Maximal Medical Therapy
and Stable for 30 Days--Clients should be on maximal medical therapy
and stable for 30 days before decisions about LTOT are made. Short-term
oxygen may be instituted in the interim. In addition to treating acute
exacerbations, therapy to correct anemia and congestive heart failure should
be instituted (see Module A4, Pharmacotherapy, and Module A3, Acute Exacerbation).
Intensify smoking cessation efforts, since smoking poses a safety
hazard for patients on LTOT. The benefits of long-term oxygen therapy may
not be realized in patients who continue to smoke and have high levels
of carboxyhemoglobin.
TABLE OF EVIDENCE
| Intervention |
References |
Grade of Evidence |
Strength of Recommendation |
| LTOT prolongs life in hypoxemic patients, with greater benefit
with 24-hr/day than 12-hr/day therapy. |
MRC 1981*
NOTT 1980* |
A |
1 |
| Up to 40-percent of patients will no longer require LTOT
when retested 1 to 3 months after O2 initiation at time of instability. |
Timms 1981
Levi-Valensi 1986 |
C |
1 |
*Medical Research Council
*Noctoral Oxygen Therapy Trials
B. Is PaO2 < 55 mmHg or SaO2
< 90 Percent?--Based on a randomized controlled trial (NOTT
1980), long-term oxygen therapy of COPD patients with a PaO2
55 or a PaO2 < 60 with signs of tissue hypoxia is
associated with improved survival. Although pulse oximetry can be used
to exclude hypoxemia, measurement of resting PaO2 after 30 minutes
of breathing room air is the clinical standard for initiating LTOT. Oximetry
may be used to adjust oxygen flow settings over time.
TABLE OF EVIDENCE
| Intervention |
References |
Grade of Evidence |
Strength of Recommendation |
| Pulse oximetry is less accurate than arterial blood gases
to determine oxygenation, especially during exercise. |
Carone 1997
Carlin 1994
McGovern 1996
ATS 1995
Pierson 1990 |
C
|
1
|
C. Refer to Respiratory Specialist. Institute Long-Term,
24-Hour Oxygen Therapy--The precise PaO2 level to improve
quality of life or increase survival has not been well defined. Arterial
oxygen saturations of 90 to 92 percent or PaO2 of 60 to 65 mmHg
are usual acceptable targets because of the shape of the oxygen hemoglobin
saturation curve. Ambulatory clients should be provided ambulatory and
stationary oxygen equipment to reach the target of use 24 hours a day to
correct PaO2 > 60 or SaO2 > 90 percent.
Immobile patients may only require a stationary system with a portable
system for use during transport (see Module D, Collaborative Self-Management
for Patients with COPD/ Asthma). In most cases, changes in flow rate are
not indicated for sleep and exercise. Some authorities recommend increasing
flow rates to greater than 1 liter per minute rather than resting for possible
sleep desaturation, but evidence for this approach is not strong. If there
are signs of cor pulmonale despite adequate daytime oxygenation, the patient
may be monitored with oximetry during sleep to determine the best sleep
setting. Some patients may be candidates for oxygen-conserving devices
(e.g., reservoir cannulae, demand oxygen delivery device, transtracheal
oxygen) to improve mobility and portability of oxygen therapy.
TABLE OF EVIDENCE
| Intervention |
References |
Grade of Evidence |
Strength of Recommendation |
| Oxygen-conserving devices may reduce costs and increase
patient mobility. |
ATS 1995
Petty 1994 |
C |
2a |
D. Are There Signs of Tissue Hypoxia?--Occasionally
severe dyspnea with exercise is the result of arterial oxygen desaturation.
Evaluation of saturation during exercise should be performed in COPD patients
with such dyspnea. Signs of tissue hypoxia include: Hct > 55, "p"
pulmonale on ECG; impaired mental status; or cor pulmonale.
E. Order Overnight Oximetry and Exercise Oximetry--It
is unusual that patients with COPD and a PaO2 70 desaturate
low enough to require oxygen. During exercise, noninvasive pulse oximetry
may be inaccurate, particularly in patients with poor peripheral perfusion.
Verification of oximetry accuracy can be accomplished by obtaining ABG
before and after exercise. The level of exercise tested should be appropriate
to the patient's normal or anticipated level of activity.
In COPD clients who have PaO2 60 mmHg during wakefulness,
signs of tissue hypoxia occur more often and survival is reduced when sleep
desaturation is present (> 5 minutes during the night). However,
studies documenting improved outcome with oxygen supplementation during
sleep have yet to be conducted. One night of overnight oximetry is sufficient
to determine the present of arterial oxygen desaturation during sleep (see
Annotation G).
TABLE OF EVIDENCE
| Intervention |
References |
Grade of Evidence |
Strength of Recommendation |
| Nocturnal oxygen therapy is indicated in COPD patients who
have daytime PaO2 60 mmHg with nocturnal desaturation less than
90-percent. |
Fletcher 1989
1992a, 1992b |
C |
2a |
| Exercise desaturation does not predict nocturnal desaturation. |
Baldwin 1995 |
C |
2a |
| A diffusing capacity > 55-percent of predicted was
100-percent specific in excluding exercise desaturation compared with 82-percent
specificity for FEV1 > 55-percent predicted. |
Owens 1984 |
C |
2a |
F. Is PaO2 > 45 mmHg?--Hypercapnia
during the day predicts a high prevalence of sleep desaturation even in
patients who have PaO2 60 mmHg during wakefulness.
TABLE OF EVIDENCE
| Intervention |
References |
Grade of Evidence |
Strength of Recommendation |
| Hypercapnia (PaCO2 > 45) during the day predicts
a high prevalence of nocturnal arterial oxygen desaturation. |
Littner 1980
Fletcher 1991
Douglas 1990
Mulloy 1995
Vos 1995 |
C
|
1
|
G. Obtain Overnight Oximetry--One night of overnight
oximetry is sufficient to diagnose or substantially exclude sleep desaturation
in stable COPD clients. Such desaturation can occur as the patient's COPD
evolves with time and the overnight oximetry may need to be repeated at
regular intervals (such as 6 months to yearly) in patients who have or
develop an indication.
TABLE OF EVIDENCE
| Intervention |
References |
Grade of Evidence |
Strength of Recommendation |
| One overnight oximetry is sufficient to diagnose nocturnal
desaturation in stable COPD patients. |
Vos 1995 |
C |
2a |
H. Refer to Respiratory Specialist to Provide Long-Term
Oxygen Therapy During Sleep--Studies showing the long-term benefit
of oxygen solely for exercise desaturation have yet to be conducted. Short-term
studies have shown more immediate benefits in reduction in dyspnea, improvement
in exercise performance, and prevention of transient increases in pulmonary
artery pressure and pulmonary vascular resistance. Oxygen should be administered
to increase SaO2 to > 90 percent. To maximize mobility,
liquid or light tanks such as those made from aluminum are preferable for
use during exercise.
TABLE OF EVIDENCE
| Intervention |
References |
Grade of Evidence |
Strength of Recommendation |
| Oxygen during exercise provides short-term physiologic benefits,
reduces dyspnea, and improves exercise tolerance at submaximal workloads. |
McDonald 1995
ATS 1995
Light 1989
Zack 1985 |
C
|
2a
|
| Lightweight portable ambulatory equipment should be used
for patients who are able and willing to be active. |
Petty 1994 |
C |
2a |
I. Continue Medical Care and Follow-Up--Patients
started on oxygen therapy at the time of an exacerbation require reevaluation
within 1 to 3 months when stable. For patients started when stable on maximal
medical therapy, LTOT most likely represents a lifetime commitment. Reevaluation
every 12 months is appropriate to assess for continued need and adequacy
of flow rate. Results of O2 saturation 90 percent should not
be used as a sole rationale for discontinuing therapy.
TABLE OF EVIDENCE
| Intervention |
References |
Grade of Evidence |
Strength of Recommendation |
| Increased PaO2 after 6 months LTOT may be due
to reparative effect of LTOT. |
Summary conference report 1990
O'Donohue 1991 |
C |
2a |
Module
A4 | Table
of Contents | Module
A6