Recruitment of lung diffusing capacity with exercise before and after pneumonectomy in dogs

Abstract

Although the left lung constitutes 42% of the total by weight and volume in dogs, carbon monoxide diffusing capacity (DL) after left pneumonectomy in adults falls less than 30% at rest, indicating a significant increase of DL in the remaining lung. DL normally increases during exercise, presumably by recruitment of alveolar capillaries and surface area as lung volume (Vs) and pulmonary blood flow (Qc) increase. We asked whether the increase of DL in the remaining lung after pneumonectomy in adult dogs could be explained by this kind of passive recruitment by the increased volume and Qc in the remaining lung. We measured the relationship between DL and Qc with a rebreathing technique at increasing treadmill loads in adult foxhounds, before and 6 mo after left pneumonectomy, and the relationship between DL and Vs by the same technique under anesthesia as Vs was expanded. DL was reduced by 29.1% at rest and 26.5% with heavy exercise after left pneumonectomy, indicating either recruitment or new growth in the right lung. With the assumption that the right lung normally receives 58% of the Qc and contains 58% of the DL, DL of the right lung increased with Qc in accordance with the following relationships before and after left pneumonectomy: right lung DL (before pneumonectomy) = 6.44 + 2.40(Qc) (r = 0.963) and right lung DL (after pneumonectomy) = 7.51 + 1.75(Qc) (r = 0.958). Only approximately 7% of the increase in DL from rest to peak exercise could be attributed to the increase in Vs during exercise before pneumonectomy and approximately 15% after pneumonectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural changes underlying compensatory increase of diffusing capacity after left pneumonectomy in adult dogs.

“…However, in previous studies on dogs, we have oW served that exercise performance is not significantly impaired by left pneumonectomy (4). Diffusing capacity for carbon have increased by some 30% above that ofthe same lung before pneumonectomy (5). Two general sources of compensation are available to the remaining lung that could have accounted for the increase in DLcO after pneumonectomy: (a) greater utilization of existing physiological reserves of DLcO; and (b) growth of new gas exchange tissue.…”

“…Large reserves of diffusing capacity normally exist in the lung and can be used during exercise as pulmonary blood flow and lung volume increase (5). The anatomical basis ofrecruitment of diffusing capacity has not been fully defined, but is presumed to be due to the unfolding of alveolar-capillary membrane (6), opening and/or the distention of pulmonary capillaries (7), and an increase in hematocrit (8).…”

“…The objective of our report is to determine whether and to what extent functional compensation ofdiffusing capacity in adult dogs after left pneumonectomy has been achieved by structural adjustments in the remaining lung. If 5,[10][11][12][13]. Dogs were trained to run on a treadmill up to maximal voluntary effort.…”

Avaliação hemogasométrica em cães submetidos à pneumonectomia esquerda

“…Entretanto, verificou-se que, nos momentos seguintes, a PaO 2 já retornava a valores do intervalo fisiológico para, no T36d, não mais apresentar diferenças significativas em relação ao T0. Estes resultados corroboram com os obtidos por Carlin et al (1991), Hsia et al (1994) e Takeda et al (1999) no pós-operatório mediato. Esta hipoxemia momentânea verificada uma hora após a extubação pode estar relacionada a diferentes fatores.…”

“…Estes resultados vêm ao encontro daqueles descritos por Carlin et al (1991), Hsia et al (1994) e Takeda et al (1999) no pós-operatório mediato, como já ressaltado no segundo parágrafo da discussão.…”