Computerized morphometry of the pulmonary vasculature over a range of intravascular pressures

Abstract

Recent availability of computerized image analysis has fostered hope that barium injection and landmarking of pulmonary arteries would be unnecessary for morphometric assessment when using this technique. We reasoned that if barium injection altered morphometric variables, it would do so in a linear fashion correlating with incremental increases in injection pressure of the barium. The two goals of the present study were to determine whether barium injection into arteries affected morphometric measurements and to determine whether incremental increases in injection pressure correlated with alterations in morphometric measurements in a linear fashion. Computerized image analysis was used to measure the internal elastic lamina (IEL) and external elastic lamina (EEL). Medial area (MA), luminal area (LA), percentage of medial thickness, IELͱMA, and idealized LA were calculated. Barium injection did not alter morphometric variables in a linear fashion correlating with incremental increases in injection pressure of the barium except the percentage of arteries that filled with barium. Maximum recruitment for pre-acinar arteries occurred at 40 mmHg pressure and 60 mmHg distending pressure for intra-acinar arteries. Incremental increases in injection pressure did not affect IEL, EEL, or calculated morphometric variables. However, IEL, medial thickness, and MA were all smaller in injected vessels than in uninjected vessels. IELͱMA and the ratio of measured vs. idealized LA were both increased in injected lungs. We suspect that vascular injection selects for evaluation, a population of smaller, thin-walled vessels, which in the uninjected lungs are collapsed and hence excluded from analysis. Anat. Rec. 252:92-101, 1998. 1998 Key words: computer-assisted diagnosis; pulmonary artery; pulmonary circulation; pulmonary hypertension; vascular resistance; vascular smooth muscle Computerized interactive morphometric analysis entails measurement of the internal elastic lamina (IEL) circumference and the outer limit of the media, often demarcated in larger vessels, by the external elastic lamina (EEL). The computer then, by using integrals, calculates the actual area occupied by the media and lumen. Computer-assisted morphometric analysis is based on the premise that medial cross-sectional area and IEL circumference of the vessel wall are independent of intravascular distending pressure, thus raising the hope that the practice of uniform vascular distension would no longer be necessary (Cook and Yates, 1972). Traditional morphometric analysis requires preparation of the lungs under uniform conditions to ensure accurate comparisons. Lungs for morphometric evaluation are traditionally fixed after intravascular injection of a barium sulfate/gelatin suspension at a standard supraphysiologic pressure (73 mmHg).

Structure and Composition of Pulmonary Arteries, Capillaries, and Veins

“…However, this consistent proximal-to-distal decrement in medial thickness is absent in lungs fixed by immersion or by airway instillation of fixative (but without gelatin in the vasculature). As a result, the % medial thickness measured with these preparations varies little between large and small arteries (see Table 2 ) and exceeds that measured when gelatin infusion is included in the preparation (227). Data varies regarding the contribution of muscular pulmonary arteries to total artery number within the respiratory acinus in human lung.…”

“…In rat the frequency with which muscular arteries are found adjacent to respiratory bronchioles is substantially less, ranging from 4-10% in most reports (2, 115, 140). Muscular arteries can be found as far distal as the alveolar wall in the dog, rabbit and rat lung, albeit with low frequency (52, 132, 204, 227). …”

Acinar arterial changes with chronic lung disease of prematurity in the surfactant era

“…The percent wall thickness is a quantitative test but is dependent on similar barium sulfate expansion of all intraacinar vessels, which does not always occur. 22 The arteriograms showed a variability in filling patterns.…”

PRX-08066, a Novel 5-Hydroxytryptamine Receptor 2B Antagonist, Reduces Monocrotaline-Induced Pulmonary Arterial Hypertension and Right Ventricular Hypertrophy in Rats

“…MetaMorph Offline imaging software (MetaMorph Imaging System; Molecular Devices, Sunnyvale, CA) was used to calculate the area of the lumen and the area of total vessel. A ratio of lumen area to total vessel area multiplied by 100 (L/TV%) was then calculated as a relative measurement of arteriole wall thickness and lumen-carrying capacity (Ohar et al, 1998;Zhou et al, 2006). Statistical Analysis.…”