Controlled oxygen administration in acute respiratory failure in chronic obstructive pulmonary disease: a reappraisal

Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is equated with chronic bronchitis and emphysema as one disease entity. In COPD airflow limitation is relatively persistent--unlike asthma. Tests for "small-airways disease" form no part of routine practice, for their accuracy in detecting pathological change is debatable. The proteolytic theory of the pathogenesis of emphysema highlights the role of neutrophil elastase, antielastases, oxidants, antioxidants, and thus of potential new treatments. Clinical features of COPD include breathlessness, cough, and sputum, with airflow obstruction and lung hyperinflation. The differential diagnosis includes bronchiectasis, cystic fibrosis, and pulmonary hypertension, but pulmonary fibrosis, etc., is distinguished by radiological infiltrates. Plain chest radiography cannot reliably diagnose emphysema in life, but a new method measuring lung density from the computed tomographic (CT) scan allows location, quantitation, and diagnosis of emphysema (defined by enlargement of distal air spaces) in humans in life. "Pink puffers" with breathlessness, hyperinflation, mild hypoxemia, and a low PCO2 are contrasted with "blue bloaters" with hypoxemia, secondary polycythemia, CO2 retention, and pulmonary hypertension and cor pulmonale. Antismoking measures are a major aim in management. A bronchodilator regimen combining a slow-release oral theophylline with an inhaled beta 2-agonist, ipratropium, and high-dose inhaled steroids is proposed because even modest improvement in obstruction can help these patients. In acute exacerbations with purulent sputum, antimicrobials against Streptococcus pneumoniae and Hemophilus influenzae are used with controlled oxygen therapy aiming to keep the arterial PO2 over 50 mm Hg without the pH falling below 7.25. Influenza prophylaxis is recommended, but pneumococcal vaccination remains debatable. Chronic under-nutrition in "emphysema" implies controlled trials of feeding regimens--but these remain to be assessed. Long-term oxygen therapy is the only treatment known to prolong life in blue bloaters, and oxygen concentrators and transtracheal oxygen delivery are discussed. Pulmonary vasodilators (e.g., beta 2-agonists, hydralazine, nifedipine, angiotensin-converting enzyme [ACE] inhibitors, etc.) have not yet been proved to provide long-term reduction in pulmonary arterial pressure. Blue bloaters have severe nocturnal hypoxemia in rapid eye movement (REM) sleep that is corrected by oxygen or the investigational drug almitrine.(ABSTRACT TRUNCATED AT 400 WORDS)

Failure to predict six-month survival of patients with COPD requiring mechanical ventilation by analysis of simple indices. A prospective study

We analyzed the outcome of 39 consecutive acute exacerbations of chronic obstructive pulmonary disease (COPD) in 35 patients requiring mechanical ventilation, in order to identify the features related to survival. Patients were divided into those surviving less (group A; n = 14) and more (group B; n = 24) than six months. Pulmonary function tests, arterial blood gas levels either on admission or while in a steady state, and nutritional parameters were similar in both groups. Only the duration of mechanical ventilation was longer in group A when compared to group B. In patients dying while being ventilated or surviving less than ten days after extubation, only the forced vital capacity (FVC) was different when compared to the rest of group A. The duration of mechanical ventilation was not related to age or the forced expiratory volume in one second (FEV1). Only a multivariate analysis accounting simultaneously for eight parameters could separate with 78 percent accuracy the different groups of patients; however, following this analysis, 23 percent of the patients in group B could have been falsely classified as nonsurvivors and perhaps rejected for mechanical ventilation. We conclude that the six-month survival of patients with COPD who required mechanical ventilation for an acute exacerbation of their disease cannot be predicted from simple data generally available to the physician in charge at the time of intubation.

Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease (COPD) and asthma. This official statement of the American Thoracic Society was adopted by the ATS Board of Directors, November 1986

Chronic obstructive pulmonary disease (COPD) and asthma are the major causes of pulmonary disability in the United States, with at least 10 million Americans suffering form COPD and up to 5% of the population afflicted with asthma. Over the past 20 years, major strides have been made in our understanding of the pathophysiology of these disorders, although there are still large gaps in our knowledge. While a number of position papers and statements have been promulgated by the American Thoracic Society concerning various aspects of the diagnosis and treatment of COPD and asthma, it was felt that a review of the overall topic was timely. This statement represents the combined efforts of a Task Group appointed by the Scientific Assemble of Clinical Problems of the American Thoracic Society to accomplish this task. Clearly, we could not cover every aspect of this broad topic nor even provide a detailed review of those areas addressed. We elected instead to concentrate on clinically relevant topics and to provide sufficient data to be useful as a guide as well as to include selected, but in no was exhaustive, references. The first two chapters define the entities and set forth recommendations for diagnosis, hospital admission, and discharge. The remaining four chapters critically review the various facets of therapy. We have noted controversial areas and those were conclusive experimental data are not yet available. In these situations, the committee often decided to take a position on one side or the other based upon the best available information.

Acute respiratory failure and chronic obstructive lung disease

Patients with COPD who develop acute respiratory failure require special attention in their management. Patients with severe COPD often have cor pulmonale, complex acid/base compensations, and altered respiratory control mechanisms. These need to be considered when approaching the patient with an acute decompensation. Because of the improving prognosis in this group of patients, aggressive management should be undertaken using combinations of bronchodilator medications, oxygen, bronchial hygiene, and antibiotics.

Chronic obstructive lung disease and acute respiratory failure

Patients with chronic obstructive lung disease (COLD) experience one or more episodes of acute respiratory failure in the late years of their illness. Initial evaluation is aimed at assessing the precipitating factor or factors as well as the severity of the acute episode and the need for intubation and mechanical ventilation. Specific treatment is directed toward the individual precipitating cause, as well as toward the general relief of hypoxemia and airflow obstruction. The prognosis for recovery from most episodes of acute respiratory failure is excellent and warrants an aggressive approach.

Effect of supplemental nocturnal oxygen on gas exchange in patients with severe obstructive lung disease

We studied the effect of supplemental nocturnal oxygen on blood gases in 15 patients with severe but stable chronic obstructive lung disease (ratio of forced expired volume in one second to forced vital capacity, 37.2 +/- 1.8 [mean +/- S.E.] per cent of predicted; arterial oxygen tension, 50.7 +/- 1.4 mm Hg; and arterial carbon dioxide tension [PCO2], 53.1 +/- 1.5 mm Hg). Sleep variables and measures of gas exchange were determined on two consecutive nights; on the first night the subjects breathed supplemental oxygen, and on the second they breathed room air. Transcutaneous PCO2 was measured with an infrared sensor, and arterial oxygen saturation with an ear oximeter. Breathing of supplemental oxygen sufficient to keep oxygen saturation at or above 90 per cent was associated with only small increases (less than 6 mm Hg) in PCO2 throughout sleep, as compared with values while subjects were breathing room air. The increase in PCO2 occurred early in the night and was not progressive. Only three patients, who were found to have obstructive sleep apnea in addition to obstructive lung disease, had larger increases in PCO2 during sleep and reported morning headaches. We conclude that nocturnal oxygen does not induce clinically important increases in PCO2 during sleep in patients with stable obstructive lung disease and therefore can safely be used to prevent the dangerous consequences of hypoxia.

Oxygen therapy and oxygen toxicity

When oxygen therapy is warranted, the minimum effective dose generally should be given. Hypoxemic patients who have normal baseline ABG may be treated initially with an intermediate to high FiO2 in the range of 35% to 100%, depending on the severity of the respiratory distress. The majority of patients with exacerbations of COPD who are not in extremis may be given an initial FiO2 of 28%, especially if their previous response to oxygen is known. When treating patients who have chronic severe hypercapnia (eg, those requiring chronic home oxygen), the initial FiO2 should be 24% even though renal compensation of the respiratory acidosis has occurred. Further mild elevation of the PaCO2, due mainly to the V/Q mismatch that oxygen therapy induces, may be sufficient to precipitate unacceptable hypercapnia. Patients with exacerbations of COPD who are obviously in extremis, with severe hypoxemia and acidosis, should start with an FiO2 of 24% unless they are being mechanically ventilated. The severity of the hypoxemia and acidosis is more predictive for the development of CO2 narcosis and respiratory failure than is the degree of hypercapnia in these patients. The FiO2 can be increased to 28% and incrementally higher if low FiO2 is tolerated. The use of a high FiO2 is subject to the following guidelines for prevention of clinically significant oxygen toxicity: 100% oxygen at atmospheric pressure is safe if given for less than six hours; 70% oxygen is probably safe for 24 hours; and after this time, 45% should be the approximate upper limit to the FiO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute respiratory failure and chronic obstructive lung disease: recent advances

Treatment of respiratory failure in the patient with chronic obstructive lung disease requires the use of a controlled oxygen, treatment of reversible causes of deterioration, and treatment of the associated bronchospasm. Complications such as pulmonary emboli and gastrointestinal bleeding should be avoided by prophylactic therapy. Mechanical ventilation should be avoided if possible. If the patient requires intubation, weaning and extubation should be an orderly transition to spontaneous ventilation. Nutritional support should be stressed during respiratory failure. Finally, as explained in detail in other chapters, a comprehensive outpatient treatment program should be planned prior to discharge from the hospital. A comprehensive approach to management should improve the quality of life and further improve survival in the patient with chronic obstructive lung diseases.

Respiratory failure revisited: acute exacerbations of chronic bronchitis between 1961-68 and 1970-76

Factors determining survival have been analysed retrospectively in 157 admissions of 135 patients with an acute exacerbation of chronic bronchitis and emphysema causing hypoxaemia and carbon dioxide retention. All were treated with controlled oxygen therapy. The death-rate increased with the age of the patient, but was not correlated with the age of the patient, but was not correlated with the severity of hypoxaemia on admission, when the patient was breathing air. The death-rate was significantly higher in those patients in whom arterial [H+] rose above 55 nmol/1 (pH = 7.26) during controlled oxygen therapy. The absence of a rise in the arterial PCO2 during controlled oxygen therapy was not necessarily indicative of a good prognosis, since 5 out of 18 patients showing this response subsequently died in that admission. Only 28% of the 111 patients who left hospital alive survived for five years.