Continuous negative extrathoracic pressure ventilation, lung water volume, and central blood volume. Studies in dogs with pulmonary edema induced by oleic acid.

The effect of continuous positive-pressure ventilation (CPPV) on extravascular lung water volume has been investigated, but there is only one report which studied the effect of continuous negative extrathoracic pressure ventilation (CNETPV). The effect of CNETPV on central blood volume (CBV) has not been studied. Changes in intrathoracic pressure by CNETPV may alter lung water volume and CBV. In this study the effects of CNETPV on lung water volume and CBV were compared with those of intermittent positive-pressure ventilation (IPPV) and CPPV in dogs with pulmonary edema induced by oleic acid. Nine mongrel dogs were anesthetized and given oleic acid at 0.06 ml/kg intravenously to induce pulmonary edema; CNETPV was applied with a cuirass and a negative thoracic pressure ventilator (Kimura OKT-100) for 1 h. Extravascular lung water volume (as extravascular thermal volume [EVTV]) and CBV were estimated with the double-indicator dilution method using thermal-sodium; PEEP and continuous negative extrathoracic pressure were matched to produce the same increments in FRC. The EVTV increased during CNETPV but did not change during CPPV. The CBV decreased during CPPV but did not change during CNETPV. An increase of transmural pulmonary microvascular pressure was thought to be one of the reasons for the increase in EVTV with CNETPV.