Trials of Live Influenza Vaccine in the Royal Air Force.

evidence of enlargement of the main pulmonary artery were assessed in all. We attempted to assess changes in the peripheral pulmonary arterial branches as recommended by Davies, Goodwin, Steiner, and Van Leuven (1953), but found in many cases this was too difficult to determine with sufficient certainty. The three criteria we have used (pulmonary hypertension, E.C.G. signs of right ventricular hypertrophy, and enlargement of the pulmonary artery) as a reflection of the pulmonary vascular resistance are not of course exact, but, accepting the inevitable arbitrary grading, we have divided our patients into four grades of presumptive severity: nil, mild, moderate, and severe (Table XXIX).