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A Short Guide to Maximizing Long-term O2 Therapy

A Short Guide to Maximizing Long-term O2 Therapy

Q:Which patients with chronic obstructive pulmonary disease (COPD)
benefit most from long-term oxygen therapy?

A:Long-term oxygen therapy (LTOT) improves both the length and quality
of life of hypoxemic patients with COPD.1,2 It is the only therapy that
clearly increases survival for selected patients with advanced stable COPD.1

LTOT is prescribed both for patients with exacerbations of COPD and for
those with advanced disease.

Exacerbations of COPD. LTOT may be prescribed for hypoxemic
patients at discharge from the hospital following an acute exacerbation.
Hypoxemia is defined as a resting arterial oxygen saturation (SaO2) of 88% or
less, which corresponds to a partial pressure of arterial oxygen (PaO2) of
55 mm Hg or less. Many hypoxemic patients recover sufficient lung function
so as not to need oxygen for physiologic indications. After about 60 to 90 days
of LTOT, retest these patients once they have not received oxygen for 20 minutes
to determine if significant hypoxemia is still present. In many patients,
LTOT can be discontinued if normoxia is found with pulse oximetry or, better
yet, arterial blood gas analysis.

Advanced disease. The second group of candidates for LTOT are those
with stable advanced COPD characterized by compelling symptoms, such as
dyspnea on exertion, evidence of right-sided heart failure, or morning headache.
3,4 These patients are typically being treated with a maintenance regimen
of inhaled bronchodilators (anticholinergics, β-agonists, or both); theophylline
when appropriate; and, often, inhaled corticosteroids.

Patients with an SaO2 of 88% or less and a PaO2 of 55 mm Hg or less
qualify for third-party reimbursement (Table). Reimbursement is also allowed
for an SaO2 as high as 89% if a patient has secondary polycythemia with a hematocrit
of 55% or more or clinical signs of cor pulmonale (verified on chest
radiography and ECG).

  Table —Indications for long-term oxygen therapy
(standard reimbursement criteria)
Obligatory
For a patient who has been treated with an optimal medical regimen
for at least 30 d* and whose values are PaO2 = 55 - 59 mm Hg or
SaO2 = 88%.†
 

For a patient with cor pulmonale or erythrocytosis (hematocrit > 55%)
whose values are PaO2 55 - 59 mm Hg or SaO2 = 89%.†
 

Optional  
For a patient whose room-air PaO2 is ≤ 55 mm Hg or SaO2 ≤ 88%
during exercise or sleep but whose daytime values may be
PaO2 ≥ 60 mm Hg or SaO2 ≥ 90%.†
 

PaO2, partial pressure of arterial oxygen; SaO2, arterial oxygen saturation.
*Patients who are recovering from an acute respiratory illness and who meet the listed criteria should
be given oxygen and rechecked while breathing room air in 60 - 90 d.
†Arterial oxygen levels measured at rest during air breathing.
Adapted from Beers MH, Berkow R, eds. The Merck Manual of Diagnosis and Therapy. 1999.5

Once a patient with chronic stable COPD requires oxygen, he or she
will need it for life. There is no need to retest for hypoxemia after LTOT has
been administered for months. Because oxygen is a potent bronchodilator
and vasodilator, it has a restorative effect in some patients. Thus, if LTOT
improves ventilation/perfusion matching, room-air PaO2 may rise. It is as inappropriate
to withhold oxygen from patients with this successful outcome
as it would be to withhold insulin from a patient with diabetes after blood glucose
is controlled or to withhold systemic antihypertensives after serious
hypertension is controlled.

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