Guide to Prescribing Home Oxygen

by Thomas
L. Petty, M.D.

Contents

The Key
to Prescibing Home Oxygen

Introduction

Keys
to Successful Treatment

Home
Oxygen Options

Conserving
Device Technology

Costs
and Reimbursement

Patient
Considerations in Selecting Equipment

About
Thomas L. Petty, M. D.

For educational
purposes only.

INTRODUCTION

The purpose of this guide is to direct the physician and other
healthcare providers in deciding which oxygen modality is best for each
long-term oxygen therapy (LTOT) patient. This document provides
information on how to match the appropriate piece of oxygen equipment to
the right patient.

COPD Disease State

Chronic hypoxemia results in reactive pulmonary hypertension, which
increases right ventricular afterload. This results in limitation of
cardiac output of the right ventricle and eventual cor pulmonale and right
heart failure. An expanded red cell mass and increased plasma volume due
to salt and water retention by the kidneys in response to hypoxemia add to
the hemodynamic burden. However, pulmonary pressures are only modestly
elevated in COPD and in most interstitial lung diseases. The levels of
pulmonary hypertension in COPD are considerably less severe than the
pulmonary pressures associated with primary and thromboembolic forms of
pulmonary hypertension. Why cor pulmonale in COPD carries such a poor
prognosis is somewhat difficult to comprehend. The answer may lie in the
fact that the consequences of chronic hypoxemia are not just
cardiovascular, hematologic and renal in origin. Thus, the presence of cor
pulmonale in COPD may simply be a surrogate marker of disease severity.
The multiorgan deterioration in advanced COPD and other chronic pulmonary
problems appears to be global and likely is an interaction between
hypoxemia and nutritional-metabolic abnormalities. Subtle, but progressive
multiorgan dysfunction occurs in advanced stages of COPD and related
disorders such as interstitial fibrosis and cystic fibrosis, which are
also characterized by chronic progressive hypoxemia. In any case,
correction of hypoxemia results in improved hemodynamics, reduction of red
cell mass, dry weight gain and improved exercise tolerance.’ Improved
brain function and quality of life accompany these physiologic
improvements in response to LTOT.2

Indications for LTOT

Table 1 lists the commonly accepted indications for LTOT and the
requirements for oxygen prescription from the Health Care Finance
Administration (HCFA) and certain insurance plans. When daytime normoxia
is present, but sleep-related hypoxemia has been established by continuous
nocturnal monitoring of oxygen saturation, oxygen can be prescribed during
the hours of sleep when there is clinical evidence of harm from the
consequences of hypoxemia, i.e., morning headaches, clinical evidence of
pulmonary hypertension and erythrocytosis. Similarly, if exercise-related
hypoxemia is demonstrated by pulse oximetry, ambulatory oxygen can be
prescribed and is particularly appropriate if it can be demonstrated those
improved exercise-tolerance results are from ambulatory oxygen therapy

Controlled Clinical Trials of LTOT

Two major randomized controlled clinical trials conducted in the late
1970’s firmly established the scientific basis for LTOT. The Nocturnal
Oxygen Therapy Trial (NOTT) studied what was intended to be continuous
oxygen therapy (COT), using an ambulatory system which was most often
liquid portable oxygen compared with nocturnal oxygen therapy (NOT) for 12
hours per day which most commonly employed a concentrator. In a few
patients, high pressure oxygen tanks were used for NOT.3 This study was
conducted in six North American cities (n=203). The general conclusion
that can be made from this study is that patients who used continuous Oz
therapy had more benefits than those who used intermittent Oi therapy.

The second study was the British Medical Research Council
(MRC) controlled clinical trials conducted in the United Kingdom. This
study compared 15 hours of oxygen from a stationary source with no oxygen
in a random assignment of patients with severe COPD and chronic stable
hypoxemia. Since the severity of disease and the demographics of the NOTT
and MRC studies were similar, it is reasonable to compare the outcomes of
the four study groups. The survival data are presented in Figure I.5 These
data indicate that the survival in advanced COPD with chronic stable
hypoxemia was poor with no supplemental oxygen. It was better to a
statistically significant degree with oxygen delivered approximately 12
hours per day in the NOTT trial or 15 hours per day in the British MRC
Clinical Trial. Survival was much better with more continuous oxygen
therapy (COT). However, in the NOTT, review of diaries used in COT
patients showed that the median duration of oxygen actually delivered was
19.4 hours per day and the average use was 17.7 hours per day. (See Figure
1.)

The improved survival in the LTOT patients compared with the other
groups could have resulted from the longer duration of oxygen
administration. It is a reasonable hypothesis that ability to ambulate and
participate in more activities of daily living while using ambulatory
oxygen resulted in improved physical conditioning and psychosocial
adjustments that contributed to the improved survival and quality of life.

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