Pulmonary Imaging Laboratory, UC San Diego Health Sciences, La Jolla, California, United States.
Department of Radiology, University of California, San Diego, La Jolla, California, United States.
J Appl Physiol (1985). 2024 Apr 1;136(4):853-863. doi: 10.1152/japplphysiol.00747.2023. Epub 2024 Feb 22.
Ventilation-perfusion matching occurs passively and is also actively regulated through hypoxic pulmonary vasoconstriction (HPV). The extent of HPV activity in humans, particularly normal subjects, is uncertain. Current evaluation of HPV assesses changes in ventilation-perfusion relationships/pulmonary vascular resistance with hypoxia and is invasive, or unsuitable for patients because of safety concerns. We used a noninvasive imaging-based approach to quantify the pulmonary vascular response to oxygen as a metric of HPV by measuring perfusion changes between breathing 21% and 30%O using arterial spin labeling (ASL) MRI. We hypothesized that the differences between 21% and 30%O images reflecting HPV release would be ) significantly greater than the differences without [Formula: see text] changes (e.g., 21-21% and 30-30%O) and ) negatively associated with ventilation-perfusion mismatch. Perfusion was quantified in the right lung in normoxia (baseline), after 15 min of 30% O breathing (hyperoxia) and 15 min normoxic recovery (recovery) in healthy subjects (7 M, 7 F; age = 41.4 ± 19.6 yr). Normalized, smoothed, and registered pairs of perfusion images were subtracted and the mean square difference (MSD) was calculated. Separately, regional alveolar ventilation and perfusion were quantified from specific ventilation, proton density, and ASL imaging; the spatial variance of ventilation-perfusion (σV̇a/Q̇) distributions was calculated. The O-responsive MSD was reproducible ( = 0.94, < 0.0001) and greater (0.16 ± 0.06, < 0.0001) than that from subtracted images collected under the same [Formula: see text] (baseline = 0.09 ± 0.04, hyperoxia = 0.08 ± 0.04, recovery = 0.08 ± 0.03), which were not different from one another ( = 0.2). The O-responsive MSD was correlated with σV̇a/Q̇ ( = 0.47, = 0.007). These data suggest that active HPV optimizes ventilation-perfusion matching in normal subjects. This noninvasive approach could be applied to patients with different disease phenotypes to assess HPV and ventilation-perfusion mismatch. We developed a new proton MRI method to noninvasively quantify the pulmonary vascular response to oxygen. Using a hyperoxic stimulus to release HPV, we quantified the resulting redistribution of perfusion. The differences between normoxic and hyperoxic images were greater than those between images without [Formula: see text] changes and negatively correlated with ventilation-perfusion mismatch. This suggests that active HPV optimizes ventilation-perfusion matching in normal subjects. This approach is suitable for assessing patients with different disease phenotypes.
通气-血流匹配是被动发生的，也可以通过低氧性肺血管收缩（HPV）主动调节。HPV 在人类中的活性程度，特别是在正常受试者中的活性程度，尚不确定。目前对 HPV 的评估是通过测量在缺氧时通气-血流关系/肺血管阻力的变化来进行的，这是一种侵入性的方法，或者由于安全性问题，不适合患者。我们使用了一种基于非侵入性成像的方法来定量测量氧对肺血管的反应，方法是使用动脉自旋标记（ASL）MRI 测量呼吸 21%和 30%O 之间的灌注变化。我们假设，反映 HPV 释放的 21%和 30%O 图像之间的差异（[Formula: see text]）将显著大于没有变化的差异（例如，21-21%和 30-30%O），并且与通气-血流不匹配呈负相关。在健康受试者（7 名男性，7 名女性；年龄=41.4±19.6 岁）中，在正常氧合（基线）、30%O 呼吸 15 分钟（高氧）和 15 分钟正常氧合恢复（恢复）后，在右肺中定量了灌注。对正常化、平滑化和配准的灌注图像对进行了减法，并计算了均方根差（MSD）。此外，从特定的通气、质子密度和 ASL 成像中定量了区域肺泡通气和灌注；计算了通气-灌注（σV̇a/Q̇）分布的空间方差。O 反应性 MSD 是可重复的（=0.94，<0.0001），并且大于（0.16±0.06，<0.0001）在相同[Formula: see text]下收集的减去图像（基线=0.09±0.04，高氧=0.08±0.04，恢复=0.08±0.03）之间的差异（=0.2）。O 反应性 MSD 与 σV̇a/Q̇呈正相关（=0.47，=0.007）。这些数据表明，主动 HPV 优化了正常受试者的通气-血流匹配。这种非侵入性方法可应用于具有不同疾病表型的患者，以评估 HPV 和通气-血流不匹配。我们开发了一种新的质子 MRI 方法来无创地量化肺血管对氧的反应。使用高氧刺激来释放 HPV，我们定量了灌注的重新分布。与没有[Formula: see text]变化的图像相比，正常氧和高氧图像之间的差异更大，并且与通气-血流不匹配呈负相关。这表明主动 HPV 优化了正常受试者的通气-血流匹配。这种方法适用于评估具有不同疾病表型的患者。
