Ball Valve Gas Trapping in Pediatric One‐Lung Ventilation: Not All Ventilation Is Loss of Isolation

We thank Templeton et al. [1] for their valuable insights. We completely agree that one lung ventilation in small children is challenging in part due to air-trapping and ballooning of the collapsed lung. As mentioned by the authors, choosing too small a bronchial cuff predisposes to a ball-valve effect by necessitating cuff over-inflation, thus reducing the equatorial cuff-bronchial interface and leading to a poor seal [1]. Another reason for using the largest possible bronchial blockers (BBs), in our opinion, is the fact that larger blockers have thicker stems, offering stronger support and possibly lesser chance that the BB would recoil into the trachea. The short mainstem bronchi in children increase the chance of a dislocation of the BB into the trachea causing sudden complete tracheal occlusion. Immediate deflation is needed, leading to loss of lung isolation and interruption of surgery. The BB then needs to be re-positioned, which, if in the left mainstem, can be particularly time-consuming. Sometimes the retrograde migration of the BB is caused by the surgeon manipulating the lung more than usual to stem a major bleed, and sudden loss of lung isolation at this time is very problematic. In one series, retrograde migration of the Arndt blocker with a high-volume low-pressure balloon, occurred in 3 (13%) of 23 cases [2]. To minimize air-trapping, one may need to inflate the BB to a higher pressure. Pressure titration, however, must be done with two problems in mind. First, increased BB pressure may injure the bronchial mucosa and the supporting cartilages. Second, a tense BB may increase the chance of retrograde migration into the trachea. In children, it is common to have to re-inflate the down-lung to restore satisfactory oxygen saturation several times before the pulse oximetry stabilizes. If and once the minimum BB inflation pressure is found and there is no ball-valve effect, the delicate balance needs to be maintained with each deflation and inflation. To maintain accuracy, we prefer to attach a three-way stopcock to the inflation port to minimize air leak during connection and disconnection of the syringe. To ensure a stable endobronchial blockade, we deliberately have the BB emerge from the Murphy eye of the endotracheal tube (ETT). We also position the ETT tip close to the carina (Figure 1) [3]. Migration of the BB into the trachea is prevented. Ventilatory pressure is directed away from the non-ventilated side, possibly resulting in slightly less change in the bronchial diameter between inspirations and expirations on that side. To utilize this technique, the ETT must already have the BB intraluminally with its tip emerging slightly through the Murphy eye during intubation. This technique is suitable for children old enough to accommodate an ETT of internal diameter 4.5 mm such that a neonatal flexible bronchoscope can be inserted coaxially and still allows positive-pressure ventilation. If the left mainstem is the target to block, as soon as the ETT tip has passed the larynx, the ETT should be rotated 180° such that the BB can be easily advanced into the left mainstem once the ETT tip has been placed just above the carina. The authors declare no conflicts of interest. Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.

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