possible case of diabetes for the first time plasma glucose values ought to be reported. If anticoagulants interfere with the precipitating second antibody of double antibody insulin assay systems then separation of insulin ought to be achieved by other methods-for example, by adsorption to charcoal. They are equally efficient and simple to use.Glucose and insulin responses are being studied under widely varying circumstances-relation between mother and fetus, hypoglycaemic disturbances in the neonate, and the effects of new oral hypoglycaemic agents. Precise comparisons of data in these and other fields cannot be made unless glucose and insulin concentrations are determined on the same basis. An agreement on basic methodology will help to save a great deal of confusion in the future.
SUMMARY Overnight tape recordings of breathing movements, airflow, and arterial oxygen saturation from six infants aged 3 weeks to 7 months, who had cyanotic episodes associated with pertussis, were compared with recordings from 12 age matched healthy controls. In all patients clinically apparent apnoeic episodes were associated with the rapid onset and progression of central cyanosis. When overnight recordings were compared, patients with pertussis had a greater frequency of apnoeic pauses (particularly those ,12-0 seconds duration) and a greater frequency of episodes of hypoxaemia (oxygen saturation -80% for O0 5 seconds) associated with apnoeic pauses. In addition to episodes of hypoxaemia associated with a prolonged absence of breathing movements, patients with pertussis had frequent dips in oxygen saturation in association with continued breathing movements with and without continued inspiratory airflow. These episodes of hypoxaemia during continued breathing movements were more common in patients with pertussis.These findings suggest that episodes of abnormal apnoea accompanied by evidence of a mismatch between ventilation and perfusion of the lungs may produce the rapid onset of severe hypoxaemia in infants with pertussis.Apnoeic and cyanotic episodes often occur during pertussis particularly when it occurs in early infancy.' 2 The underlying mechanisms responsible for this dangerous complication are, however, unknown. In this paper we describe the results of an investigation by non-invasive techniques of infants with pertussis experiencing frequent and severe cyanotic episodes and compare these results with those from 12 healthy, age matched infants.
Patients and methodsDetails of the six patients are given in the table. Pertussis was diagnosed by the presence of characteristic paroxysms of repetitive coughing that persisted for longer than one week and were associated with retching, vomiting, cyanosis, or convulsions in an infant who otherwise appeared to be in good health.3
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