Oxygen-induced hypercapnia revisited
2000; Elsevier BV; Volume: 356; Issue: 9241 Linguagem: Inglês
10.1016/s0140-6736(00)03119-6
ISSN1474-547X
Autores Tópico(s)Neuroscience of respiration and sleep
ResumoIt is almost a medical truism that each generation must repeat the errors of its predecessors before anyone takes note of research findings. Over 50 years ago Donald 1 Donald KW Neurological effects of oxygen. Lancet. 1949; ii: 1056-1057 Abstract Scopus (38) Google Scholar challenged the then prevailing view that hypoxaemia was the main cause of death among patients with exacerbations of chronic obstructive pulmonary disease (COPD) and pointed out the major risk of CO2 narcosis and its attendant acidosis. This impression was confirmed when arterial blood-gas tensions were first systematically recorded by McNichol and Campbell, 2 McNicol MW Campbell EJM Severity of respiratory failure: Arterial blood-gases in untreated patients. Lancet. 1965; i: 336-338 Abstract Scopus (34) Google Scholar who also appreciated that high-flow oxygen was an important cause of severe hypercapnia. This problem was overcome when Campbell designed a controlled low-flow oxygen mask. 3 Campbell EJM The J Burns Amberson Lecture. The management of acute respiratory failure in chronic bronchitis and emphysema. Am Rev Respir Dis. 1967; 96: 626-639 PubMed Google Scholar This method of oxygen delivery remains the most accurate way of controlling the inspired oxygen concentration, 4 Bazuaye EA Stone TN Corris PA Gibson GJ Variability of inspired oxygen concentration with nasal cannulas. Thorax. 1992; 47: 609-611 Crossref PubMed Scopus (97) Google Scholar although it is not necessarily one that the patient always uses effectively. 5 Costello RW Liston R McNicholas WT Compliance at night with low flow oxygen therapy: a comparison of nasal cannulae and Venturi face masks. Thorax. 1995; 50: 405-406 Crossref PubMed Scopus (53) Google Scholar Other workers subsequently noted that, even when delivery of oxygen is controlled, patients with severe COPD can still develop life-threatening acidosis requiring ventilatory assistance. 6 Bone RC Pierce AK Johnson RL Controlled oxygen administration in acute respiratory failure in chronic obstructive pulmonary disease. Am J Med. 1978; 65: 896-902 Summary Full Text PDF PubMed Scopus (72) Google Scholar , 7 Lopez-Majano V Dutton RE Regulation of respiration during oxygen breathing in chronic obstructive lung disease. Am Rev Respir Dis. 1973; 108: 232-240 PubMed Google Scholar Yet a recent 12-month review by P K Plant and colleagues in Leeds of 918 patients not managed in intensive-care units in Leeds found that 47% were hypercapnic at admission, with 20% having a pH below 7·35 and 9·4% a pH below 7·30. 8 Plant PK Owen JL Elliott MW One year period prevalence study of respiratory acidosis in acute exacerbations of COPD: implications for the provision of non-invasive ventilation and oxygen administration. Thorax. 2000; 55: 550-554 Crossref PubMed Scopus (234) Google Scholar The severity of the acidosis was greater the higherthe PaO2, which reflected the effect of prior supplementary oxygen. Of the 155 hypercapnic patients 81 had a PaO2 of more than 10 kPa. Acidosis resolved in a third of hyperoxic patients when the oxygen concentration was reduced, an uncommon occurrence among the hypoxaemic patients. Fortunately the same group of investigators have recently shown that non-invasive positive-pressure ventilation is practical in district general hospitals and can reduce mortality as well as stay in intensive-care units. 9 Plant PK Owen JL Elliott MW Early use of non-invasive ventilation for acute exacerbations of chronic obstructive pulmonary disease on general respiratory wards: a multicentre randomised controlled trial. Lancet. 2000; 355: 1931-1935 Summary Full Text Full Text PDF PubMed Scopus (1031) Google Scholar
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