: a histological terminology proposal.
The company added that the Pulmonx Zephyr Endobronchial Valves are implantable bronchial valves indicated for the bronchoscopic treatment of adult patients with hyperinflation associated with severe emphysema in regions of the lung that have little to no collateral ventilation
. During a bronchoscopic procedure, tiny Zephyr Valves are placed in the airways to occlude a diseased part of the lungs and reduce hyperinflation.
This may be attributed to the improved alveolar recruitment and the improvement in patency of peripheral airways, which may in turn result in enhanced collateral ventilation
in obstructed pulmonary areas .
We interpreted the observed residual air leak of 400-700 ml/min after placement of the two valves as "intralobar" collateral ventilation
between the closed segments 1-3 (localisation of the fistula) and the ventilated segments 4/5 of the left upper lobe.
This collateral ventilation
helps equalize pressures across alveoli and plays an important role in preventing lung collapse (i.e., atelectasis)  and promoting alveolar recruitment .
The Chartis System is a proprietary assessment system utilized immediately prior to the Zephyr EBV procedure to identify those patients with low or no collateral ventilation
, who are the most likely to respond to the treatment.
Two major caveats for the use of valves and other bronchial blocking devices are the presence of either a homogeneous distribution of emphysema or significant collateral ventilation
.  The degree of heterogeneity can be judged either by visual inspection of a high-resolution chest computed tomography (HRCT) scan or with specifically designed software.
The absence of inter-alveolar and inter-bronchiolar collateral ventilation
, the high ventilation rate and strong resistance to airflow within the respiratory conducts make them more susceptible to respiratory diseases and to infections of this organ (Lekeux, 1998).
The alveoli are laced with the Pores of Kohn, intercommunications between the alveoli that allow for collateral ventilation
A collateral ventilation
system exists in the lung between bronchi (Channels of Martin), between the bronchi and alveoli (Canals of Lambert) and between the alveoli (Pores of Kohn) (see Figure 1).
Additionally, the US patent 9,390,498, titled "Visualization and Characterization of Pulmonary Lobar Fissures," covers a framework for computing and displaying fissure integrity, a measure which serves as a surrogate for collateral ventilation
, stated the company.
 Additionally, valves fail to induce collapse when the affected portion of the lung has collateral ventilation
. This is a normal physiological phenomenon in many individuals, but significant interlobar collateral ventilation
subverts the deflating effect of endobronchial blocking devices.