Noninvasive assessment and monitoring of the pulmonary circulation

Abstract

In pulmonary vascular disease, changes in the pulmonary vascular bed will lead to altered pulmonary haemodynamics. This review describes the application of several physiological principles to measure these changes noninvasively by means of novel techniques.Flow characteristics of blood through the pulmonary vascular bed alter in pulmonary vascular disease. Recent developments in magnetic resonance imaging and computed tomography make it possible to visualise and quantify these abnormal flow patterns. Information regarding pulmonary perfusion can also be obtained by measuring the electrical impedance changes in the lung by electrical impedance tomography. A more indirect approach to measure the pulmonary blood flow is the measurement of the absorption of acetylene, a perfusion limited gas. Information on the pulmonary vascular bed can also be obtained by the measurement of exhaled products of the pulmonary vascular endothelium, such as nitric oxide.Although all the techniques described offer new ways to diagnose or monitor pulmonary vascular disease, clinical data on these techniques are limited. Further improvement and evaluation of the clinical value of these techniques are therefore obligatory before they can be used in clinical practice.

Regional distribution of blood volume within the preterm infant thorax during synchronised mechanical ventilation

“…Our study demonstrates that describing impedance change within different frequency domains is possible, even in the small neonatal chest. Technological advances that enable the complex EIT signal to be filtered has allowed assessment of impedance change due to pulmonary blood flow in adults and animal models [12,[26][27][28][29][30]. Compared to the adult, when the HR is closer to respiratory rate, delineation of the harmonics of the respiratory and cardiac frequencies may be simpler in the neonate.…”

“…Traditional methods of determining lung perfusion, such as radio-nuclide scans, are not feasible in the ventilated neonate [10][11][12]. Electrical impedance tomography (EIT) is a non-invasive, real-time, radiation-free method of measuring the relative change in impedances within regions of a cross-section of the thorax [13][14][15][16] that has been validated in newborn infants [19,20].…”

“…Air generates a greater impedance change than blood, and EIT has been used to measure regional ventilation in newborn infants [14,15,[21][22][23][24][25]. Recent technological advances now enable isolation of the EIT signal within the cardiac frequency domain [14,16,27], thus potentially allowing determination of cyclical changes in blood volume [12,[26][27][28][29][30][31]. To date, the distribution of perfusion within the lung of ventilated preterm infants has not been described.…”

Transoesophageal Doppler Monitoring For Fluid And Hemodynamic Treatment During Lung Surgery

“…Third, in this observational study, we did not address the question whether the restrictive fluid approach coupled with repeated vasopressor injection afforded better outcomes than maximizing the circulatory volume using dynamic cardiac preload markers. Assessment of blood/plasma volume and extravascular lung water content would be helpful not only for adjusting the rate of fluid administration but also for selecting the appropriate type of fluid (colloids vs. crystalloids) [33].…”

Pulmonary Hypertension: NHLBI Workshop on the Primary Prevention of Chronic Lung Diseases

“…However, methods to noninvasively image with or without ionizing radiation are rapidly advancing. For example, contrast-enhanced MRI of the lungs may provide a technique for accurately evaluating pulmonary perfusion and hemodynamics, detecting asymptomatic structural changes of PVD (26)(27)(28)(29)(30). Furthermore, the addition of phase-contrast flow measurements could facilitate reasonably accurate estimates of pulmonary artery velocities and pulmonary arterial pressure; however, detectable structural changes likely lag behind changes in pulmonary vascular function (31,32).…”