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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.

 

 


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


Table 1. General Prescribing Guidelines for Home Oxygen Patients with Advanced COPD
  Patient Selection Criteria
  • Stable course of disease on optimum indicated medical therapy, e.g., bronchodilator, antibiotics, corticosteroids
  • At least two arterial blood gas determinations while breathing air for at least 20 minutes
  • Room air POi consistently 55 or less, or consistently 55 to 59 + cor pulmonale clinically diagnosed, or hematocrit 55% or greater
  • Normoxic patients, when less dyspnea and increased exercise tolerance is demonstrated with oxygen
 
  Oxygen Dose
  • Continuous flow by double lumen nasal cannula
  • By demand system with demonstration of adequate oxygen saturation
  • Lowest liter flow to raise PCb to 60 to 65 or oxygen saturation to 88% to 94%
  • Increase baseline liter flow by 1 liter/min during exercise and sleep
 
  Expected Outcomes

There are many benefits of LTOT for patients that require it. Some of the most noted and well-documented outcomes are:

  • Improved tolerance of exercise and other ambulatory activities
  • Decreased pulmonary hypertension
  • Improved neuropsychiatric function
  • Decreased erythrocytosis and polycythemia
  • Reduced morbidity and mortality
 

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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