Further Experimental Evidence that Pulmonary Capillary Pressures Do Not Reflect Cyclic Changes in Left Atrial Pressure (Mitral Lesions and Pulmonary Embolism)

The impact of physiological and pathological processes on metabolism and transport of a variety of substances traversing the pulmonary vasculature depends in part on the capillary surface area available for exchange, and a reliable method for detecting changes in this parameter is needed. In this study, a continuous-infusion approach was used to investigate the response of the pulmonary capillary surface area to increases in flow and left atrial pressure. Isolated rat lungs were perfused with an acellular perfusion solution containing 125I-labeled albumin (an intravascular indicator) and 201Tl, a K+ analogue which is concentrated within lung cells. The extraction of 201Tl from the perfusate was 61% greater at low flow (8.5 ml/min) than at high flow (26 ml/min), and rapid changes in extraction were observed when flow was altered. In contrast, the permeability-surface area product was 76% greater when lungs were perfused at high flow than at low flow, suggesting comparable increases in pulmonary capillary surface area in these zone 2 lungs (airway pressure = 5 cmH2O, left atrial pressure < 0 cmH2O). In a second group of experiments, increases in left atrial pressure to 14 cmH2O (zone 3 lungs) at a constant flow of 8.5 ml/min increased the permeability-surface area product by only 18% despite increases in average intravascular pressure that were at least as high as those associated with high perfusion rates. 201Tl infusions provide a useful method for detecting and quantifying changes in pulmonary capillary surface area.

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Hemodynamics of the diastolic pressure gradients in acute heart failure: implications for the diagnosis of pre-capillary pulmonary hypertension in left heart disease

Pulmonary Circulation ◽

10.1177/2045894018815438 ◽

2018 ◽

Vol 9 (1) ◽

pp. 204589401881543 ◽

Cited By ~ 2

Author(s):

Doron Aronson ◽

Emilia Hardak ◽

Andrew J. Burger

Keyword(s):

Heart Failure ◽

Heart Disease ◽

Acute Heart Failure ◽

Left Atrial ◽

Diastolic Pressure ◽

Atrial Pressure ◽

Left Atrial Pressure ◽

Left Heart ◽

Left Heart Disease ◽

Pulmonary Capillary

The diastolic pressure gradient (DPG) has been proposed as the metric of choice for the diagnosis of pulmonary vascular changes in left heart disease. We tested the hypothesis that this metric is less sensitive to changes in left atrial pressure and stroke volume (SV) than the transpulmonary gradient (TPG). We studied the effect of dynamic changes in pulmonary capillary wedge pressure (PCWP), SV, and pulmonary artery capacitance (PAC) on DPG and TPG in 242 patients with acute heart failure undergoing decongestive therapy with continuous hemodynamic monitoring. There was a close impact of PCWP reduction on TPG and DPG, with a 0.13 mmHg (95% confidence interval [CI] 0.07–0.19, P < 0.0001) and 0.21 mmHg (95% CI 0.16–0.25, P < 0.0001) increase for every 1 mmHg decrease in PCWP, respectively. Changes in SV had a negligible effect on TPG and DPG (0.19 and 0.13 mmHg increase, respectively, for every 10-mL increase in SV). Heart rate was positively associated with DPG (0.41-mmHg increase per 10 BPM [95% CI 0.22–0.60, P < 0.0001]). The resistance-compliance product was positively associated with both TPG and DPG (2.65 mmHg [95% CI 2.47–2.83] and 1.94 mmHg [95% CI 1.80–2.08] for each 0.1-s increase, respectively). In conclusion, DPG is not less sensitive to changes in left atrial pressure and SV compared with TPG. Although DPG was not affected by changes in PAC, the concomitant increase in the resistance-compliance product increases DPG.

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