Factors Contributing to the Reversible Pulmonary Hypertension of Patients with Acute Respiratory Failure Studied by Serial Observations during Recovery

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Abstract
Eight patients with acute respiratory failure secondary to chronic bronchitis were studied for up to 5 consecutive days following admission; cardiac output and intravascular pressures, blood volume, arterial blood gas tensions, and body weight were measured. These observations were also compared with further measurements made some weeks later just before the patient was discharged. The effects of oxygen and acetylcholine on the pulmonary circulation were also studied. Pulmonary arterial pressure was raised in all patients during their acute illness and had fallen substantially after recovery. The pulmonary arterial pressure throughout the study correlated directly with the arterial carbon dioxide and inversely with the arterial oxygen tensions. The inhalation of 24% and 28% oxygen and the infusion of acetylcholine into the pulmonary artery resulted in a fall in pulmonary arterial pressure, often to levels close to those subsequently seen after recovery from the acute illness. No significant change in cardiac output was observed. It is suggested that the acute pulmonary hypertension seen in these patients is due primarily to pulmonary vasoconstriction resulting from hypoxia.