Ambulatory pulmonary artery pressure monitoring in pulmonary vascular disease in man

The pulmonary circulation is a relatively dynamic environment in comparison to the systemic circulation. There is no easily applied sphygmomanometer for the pulmonary circulation and conventional methods of measurement have limitations which reduce their usefulness. New treatments for pulmonary hypertension have improved considerably the prognosis for many patients and there is an emerging consensus that they are more effective if given earlier in the course of the disease. However these treatments are expensive and inconvenient to the patient and must be utilised in the context of high quality, objective assessment of the pulmonary circulation, both before and during treatment. Ambulatory pulmonary artery pressure monitoring has been used in patients with heart disease to provide an indicator of left ventricular haemodynamics. It had not been used in patients with pulmonary vascular disease due to other causes before and has been shown to be safe and well tolerated in this group. The hypothesis of this thesis was that ambulatory pulmonary artery pressure monitoring, by allowing assessment of the pulmonary circulation in a variety of real life situations in which patients commonly report symptoms, would permit the correlation of symptoms with haemodynamic changes in the pulmonary vasculature. These high fidelity pressure measurements in a low pressure system might permit a greater understanding of the total haemodynamic burden faced by these patients and (if abnormal pulmonary vascular responses to stress are indicative of the future development of pulmonary hypertension) may facilitate the early diagnosis of pulmonary hypertension. In this thesis ambulatory pulmonary artery pressure monitoring has been used to assess changes in pulmonary artery pressure with posture in a group of patients with pulmonary hypertension secondary to connective tissue disease, during exercise and sleep in a group with chronic obstructive pulmonary disease compared with normal individuals and during exercise in a group with connective tissue disease where pulmonary artery pressure was correlated with non-invasively measured variables measured during cardiopulmonary exercise testing. These non-invasively measured variables were then used to assess the response to conventional treatment in a group of patients with pulmonary hypertension secondary to connective tissue disease. These studies have shown that pulmonary artery pressure varies considerably in these circumstances and that rises in pulmonary artery pressure are not always predicted by resting pressure and can be correlated with symptoms. This work suggests that the contribution of secondary pulmonary hypertension to morbidity and mortality in patients with lung disease is considerable and underestimated. The technique of ambulatory high fidelity pressure measurement obtains a more complete picture of the haemodynamic variations induced by normal daily activity and under stress and contributes to our appreciation of the morbidity of pulmonary hypertension. Abnormal pulmonary vascular responses in these circumstances in individuals with normal resting pressure allows the identification of those at risk of resting pulmonary hypertension thus facilitating the early diagnosis of pulmonary vascular disease. The identification (during exercise) of non-invasive surrogates of pulmonary artery pressure is an area for future study since non-invasive, repeatable and reliable assessment of the pulmonary circulation is highly desirable