Recruitment of Pulmonary Capillaries

Recruitment of pulmonary capillaries is an important component of gas exchange reserve that is utilized during exercise to meet the demand for increased oxygen uptake. However, important gaps exist in our understanding of the way in which alterations of pulmonary hemodynamics, with the attendant redistribution of pulmonary blood flow, affect capillary recruitment. The major reason that many aspects of pulmonary microcirculatory function are poorly understood is the considerable technical difficulty in studying pulmonary micro-vessels directly. The classical direct approach of in vivo microscopy is plagued by problems with tissue movement during the cardiorespiratory cycles. Nevertheless, important information has come historically from in vivo microscopy of the lung. The directness of this approach continues to make the technique attractive today.