Intravital endoscopy of alveoli: a new method to visualize the mechanical alveolar dynamics

Introduction

In the frame of protective lung ventilation, alveolar biomechanics become more and more the focus of scientific interest. New microscopic techniques and experimental setups enabled a view of the alveoli dynamically changing their geometry under mechanical ventilation [1]. Although of fascinating image quality the alveoli are observed at an open chest wall under a glass plate representing an artificial situation. To circumvent this restriction we developed a method of intravital endoscopy and tested it on an animal rat model.

Methods

In cooperation with Schoelly GmbH (Denzlingen, Germany) we developed an endoscope with an outer tube diameter of 2.7 mm (including the optical fiber). To prevent the alveoli under observation from mechanical deformation due to the tip of the endoscope we developed a flushing catheter that continuously produces a thin fluid film between the endoscope tip and the alveoli being in the optical focus. The endoscope tube can be introduced by minimally invasive thoracotomy, thus enabling microscopic videos of the alveolar dynamics. The thorax remains intact.

Results

Figure 1 shows a tissue area after lavage of 0.8 mm diameter. This region is displayed at different time points during a breath. Four snapshots were taken in inspiration (upper row) and four in expiration (lower row). In the middle of the figure the corresponding P-V loop (left) and the intratidal dynamic compliance (right) are shown.

Figure 1

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Conclusion

This new minimal invasive method of intravital endoscopy enables microscopic observations of the mechanical alveolar dynamics in situ. The concurrent observation of respiratory mechanics and alveolar dynamics provides a promising tool to correlate global measurements with local alveolar properties.