Automated Analysis of Intratidal Dynamics of Alveolar Geometry From Microscopic Endoscopy

Abstract

Alveolar parenchyma, the gas exchange area of the respiratory system, is prone to mechanical damage during mechanical ventilation. Development of lung protective ventilation strategies therefore requires a better understanding of alveolar dynamics during mechanical ventilation. In this paper, we propose a novel method for automated analysis of the intratidal geometry of subpleural alveoli based on the evaluation of video frames recorded from alveolar microscopy in an experimental setting. Our method includes the recording with a microscopic endoscope, feature extraction from image data, the analysis of a single frame, the tracking and analysis of single alveoli in a video sequence, and the evaluation of the obtained sequence of alveolar geometry data. Our method enables automated analysis of 2-D alveolar geometry with sufficient temporal resolution to follow intratidal dynamics. The developed method and the reproducibility of the results were successfully validated with manually segmented video frames.

Toward a comprehensive interpretation of intravital microscopy images in studies of lung tissue dynamics

“…The bright reflexes are currently used as a border for the discrimination between alveolar lumen and tissue. [2][3][4]7 At the transition to liquid filling, the bright reflexes show decreased intensity at the side facing the liquidfilled area compared to the side facing the air-filled region [asterisk in Fig. 4(a)].…”

“…On an alveolar level, we find animal studies investigating in vivo the dynamic behavior of lung parenchyma using intravital microscopy (IVM). [1][2][3][4][5][6][7] Quantitative image analysis of such images can provide the mechanical characteristics of alveolar tissue, which can further be used to model lung mechanics in various states of the parenchyma. 8,9 But what exactly do we see on IVM images of alveoli?…”

Endomicroscopic analysis of time-dependent and pressure- dependent recruitment of subpleural alveoli

“…Alveolar size at the peak pressures and during the plateau levels was analyzed from the recorded videos frame by frame. Therefore the alveolar outline of 10 alveoli was marked manually and the outlined area was calculated [2]. Compliance of tidal breaths before and after the manoeuvres was calculated using two-point compliance.…”

Intravital microscopy of subpleural alveoli via transthoracic endoscopy

“…The method does not require removing the thoracic wall, thus allowing for free movement of the lung. It is based on an endoscopic system 4,16 that is inserted into the thoracic cavity through intercostal space. In this study, we evaluated the endoscopic IVM method, theoretically, by means of finite element (FE) models and, practically, by applying our method on isolated rat lungs and on lungs in intact rats (in vivo).…”