Iatrogenic Pediatric Pneumothorax: Reply

We appreciate the comments made by Xie et al.¹  in regard to our recent publication, “Too Much of a Good Thing: Iatrogenic Pediatric Pneumothorax from Engagement of the Oxygen Flush Valve” and the opportunity to respond to their concerns.²  We agree that an understanding of the oxygen flush valve is essential for safe delivery of anesthesia and its use is likely safe in many situations when caring for adult patients. Our intention, however, was to promote an understanding of the potential harm associated with engagement of the oxygen flush valve when the circuit is connected to pediatric patients, and in particular, very young patients for whom even brief delivery of high flows and moderately elevated airway pressures can lead to patient harm.

We agree that it is rare to fully close the adjustable pressure-limiting valve during manual ventilation, but it does not have to be fully closed to permit the generation of high flows and potentially increased pressure at the level of the alveoli with engagement of the oxygen flush valve, especially in a small child. Further, these valves can malfunction, so while they are present as a safety feature, it would be prudent to avoid any unnecessary action which would result in the need to rely on their integrity. The oxygen flush valve itself can also malfunction. One report describes an insidious malfunction in which the valve became intermittently stuck in the “on” position after engagement, but appeared to be fully functional with no damage to the exterior casing.³ 

Although Xie et al.¹  describe ventilation pressures being unaffected by engagement of the oxygen flush valve during mechanical ventilation in a machine with fresh gas decoupling, it is important to note that not all machines offer fresh gas decoupling, and historically, some that have offered it have done so in a way that is not absolute. For example, in the older Dahtex-Ohmeda Aestiva/5 (GE Healthcare, USA) and Dahtex-Ohmeda Anesthesia Delivery Unit, fresh gas decoupling was done through mechanisms that required several breaths to equilibrate, and thus did not immediately protect against sudden increases in flow and pressure during inspiration.⁴  As such, it would be dangerous to assume that the oxygen flush valve can always be safely used during inspiration in all machines with fresh gas decoupling in young children.

The oxygen flush valve is certainly a key component of the modern anesthesia machine with regard to pressurizing the system to perform leak checks, as well as to purge the system of anesthetic gas. Additionally, the use of the oxygen flush valve for jet ventilation has been described; however, this is not recommended by most anesthesia machine manufacturers.⁵  Its proposed utility in this instance, in fact, highlights its capability to deliver high pressures, and thus the potential for harm particularly in small children. When one’s goal is to fill the bellows or the bag, or to change the inspired concentration of oxygen when taking care of a young child, it is most likely safer to turn up the flow of oxygen using an oxygen flowmeter, and deliver a predictable increased flow rate rather than unregulated high flow. Why push the envelope by pushing the oxygen flush valve when taking care of a young child?

The authors declare no competing interests.