M. Guazzi et al., Influence of ACE-inhibition on salt-mediated worsening of pulmonary gas exchange in heart failure, BR J CL PH, 51(5), 2001, pp. 482-487
Aims In congestive heart failure (CHF), pulmonary gas exchange, as evaluate
d by carbon monoxide diffusion (DLCO), is impaired. ACE-inhibition improves
DLCO. Infusion of saline worsens DLCO, because of upregulated sodium and w
ater transport to the alveolar interstitium, which thickens the alveolar-ca
pillary interface and lengthens the diffusion path for gas exchange. We inv
estigated whether enalapril can readjust the capillary permeability to sodi
um.
Methods In 10 NYHA class II-III CHF patients, we measured DLCO, its two sub
components (V-C, capillary blood volume available for gas exchange, and DM,
alveolar-capillary membrane diffusion), left and right ventricular filling
pressures, plasma noradrenaline, aldosterone and renin activity, at baseli
ne and following saline infusion in the main pulmonary artery stem, before
and after 1 week enalapril treatment (20 mg daily).
Results Saline (150 mi) significantly reduced DLCO (-9.1%) and D-M (-9.8%)
and augmented V-C (+10.7%). Responses to 750 mi saline were somewhat greate
r and qualitatively similar. Enalapril produced a significant improvement o
f DLCO and D-M at rest as well as after saline, that was not associated wit
h variations in ventricular filling pressures, cardiac output and left vent
ricular ejection fraction, and was not accounted for by humoral changes.
Conclusions In CHF, ACE-inhibition attenuates the deterioration of pulmonar
y gas transfer produced by saline infusion, suggesting an ability to readju
st the upregulated sodium transport across the pulmonary microvascular endo
thelium.