THE PROGNOSTIC VALUE OF PULMONARY FUNCTION TESTS IN EMPHYSEMA. WITH SPECIAL REFERENCE TO ARTERIAL BLOOD STUDIES

Twelve year clinical study of patients with hypoxic cor pulmonale given long term domiciliary oxygen therapy

Patients presenting with chronic obstructive airways disease and hypoxic cor pulmonale were assessed during a period of clinical stability. Seventy two patients (53 male) with a mean age of 60 years were selected for long term oxygen therapy. Mean FEV1 was 0.78 l and forced vital capacity 1.9 l. The mean arterial oxygen tension (PaO2) was 6.1 kPa (46 mm Hg) and the mean arterial carbon dioxide tension (PCO2) 6.9 kPa (52 mm Hg). All patients had a PaO2 of less than 8.0 kPa (60 mm Hg) and 57 patients had a PCO2 of more than 6.0 kPa (45 mm Hg). Pulmonary haemodynamics were measured in 45 patients yielding the following mean values: pulmonary artery pressure 28.3 mm Hg; cardiac output 5.9 l min-1; total pulmonary vascular resistance 59.2 kPa l-1 S. Oxygen delivery systems, including 23 oxygen concentrators, were installed in the patients' homes. Flow rates were adjusted to raise PaO2 to more than 8.0 kPa (60 mm Hg) for at least 15 hours each day and close supervision was maintained. Overall five year survival was 62%, which is better than previously reported for this type of patient; but the 10 year survival was only 26% owing to an observed acceleration in death rate at about this time. Progressive disturbances of the pulmonary circulation were arrested. Mortality was associated with the severity of airflow obstruction, reflecting a continuing pathological process affecting the airways.

The relation between spirometric measurements and arterial blood gas analysis in patients with chronic airflow obstruction

Spirometric studies and arterial blood gas analyses were statistically evaluated in 75 patients with chronic airways obstruction to determine whether any spirometric parameters can predict arterial blood gas status. Radioactive lung scans, both ventilation (using ¹³³Xe gas) and perfusion (using ¹³¹I-MAA), were performed in selected patients.

In all 75 patients as one group, no spirometric parameter correlated with resting arterial blood gases. Comparing spirometric values with arterial blood studies during exercise, 5% carbon dioxide breathing and 100% oxygen breathing revealed no consistently predictive correlation coefficients.

Ventilation and perfusion lung scanning revealed that in patients whose ventilation/perfusion (V̇/Q) `match' was good, arterial blood gases approached normal, while hypoxaemia and/or hypercapnia were present when V̇/Q relationships were disturbed.

Spirometry measures static and dynamic lung volumes, reflecting the mechanical and structural status of the lung-bellows system. Arterial blood gas status is conditioned by severe factors, including V̇/Q relationship, and can be determined accurately only by measurement in each individual patient.

Serial studies of 100 patients with chronic airway obstruction in London and Chicago

One hundred patients with chronic airway obstruction, 50 in Chicago and 50 in London, were studied by standardized techniques in 1961. The results of the initial studies, previously reported, showed that the patients in the two cities were similar; using clinical and physiological criteria based on pathological studies, the patients were divided into three types—emphysematous type A, bronchial type B, and an indeterminate type X. The patients were studied again in succeeding years, 1962-65. During this time 26 died, 19 due to their respiratory disease; these 19 patients were initially more breathless, had a higher incidence of cor pulmonale, and had more severe airway obstruction and higher carbon dioxide pressures than the remainder. Type B patients (mortality 36%) had a worse prognosis than either type A (15%) or type X (12%). Of the measurements made, high carbon dioxide pressures were most closely related (p<0·001) to mortality.

During the period of follow-up about one-third of the patients who did not die became more short of breath and developed more severe airway obstruction and carbon dioxide retention: about 10% showed definite improvement in symptoms and pulmonary function. The F.E.V._1·0 declined on average by 46 ml./year, 4·8% of the initial value; V.C. declined by 120 ml./year, 4·0% of the initial value; mixed venous Pco₂ increased 1 mm. Hg/year.

The changes that occurred during this time confirmed the previously reported similarity between the patients attending the two clinics. Although the incidence of bronchitic exacerbations was similar in the two cities, such illnesses in the London patients led to more frequent and more prolonged incapacity.