Inline Positive End-Expiratory Pressure Valves: The Essential Component of Individualized Split Ventilator Circuits

Abstract

Background: As resources are overwhelmed with the coronavirus disease 2019 pandemic, multiple approaches to produce individualized split-ventilator designs have emerged. These designs attempt to address the significant limitations and safety concerns of coventilation practices by allowing practitioners to adjust pressure settings for individual patients connected with specialized circuits to a single ventilator. The critical component in virtually all individualized circuit designs is the adjustable inline positive end-expiratory pressure valve. Methods: We reviewed the literature on the mechanics of inline positive end-expiratory pressure valve function, the implications and considerations for advanced application of inline positive end-expiratory pressure valves in individualized circuits, available methods of adapting commercial positive end-expiratory pressure valves in the resource-restricted setting, and major caveats of the use of inline positive end-expiratory pressure valves. Results and Conclusions: The function of adjustable inline positive end-expiratory pressure valves in advanced individualized ventilator circuits has not been described. Adjustable inline positive end-expiratory pressure valves are critical to individualized circuit reliability and patient safety when attempting to extend ventilator capacity in the setting of extreme ventilator shortages. Adjustable inline positive end-expiratory pressure valves provide a means to reduce delivered peak inspiratory pressure to an individual patient circuit, a method to increase positive end-expiratory pressure for an individual patient circuit, and act as an one-way valve to ensure unidirectional gas flow through the divided circuit. Adjustable inline positive end-expiratory pressure valves can be adapted from commercial valves or printed de novo when commercial options are unavailable. Noncommercial sourcing of ventilator components should only be considered in the setting of extreme ventilator shortages under the supervision of a knowledgeable anesthesiologist or intensivist.

Ventilator output splitting interface ‘ACRA’: Description and evaluation in lung simulators and in an experimental ARDS animal model

“…This method allowed real-time and tight manual adjustments of the inspiratory flow, and is the same principle currently suggested by several authors [ 7 – 9 , 17 ]. However, it must be considered that, in pressure-controlled ventilation, the use of a pinch valve imposes changes in the delivery of the volume and that tight and individual monitoring of ventilation (i.e., capnography) and precise setting of the ventilator alarms are paramount to ensure adequate volume delivery to each paired unit [ 11 , 20 , 21 ]. In our study, it was evident that the sole modification of the respiratory rate using a variable inspiratory time resulted in a decrease of the delivered volume to the paired unit in which a restriction to flow was applied.…”

“…The use of an adjustable in line PEEP valve, however, can result in inadequate pressure signals that lead to the ventilator not reaching its target PEEP, alarm triggering and undesirable ventilator responses. According to Roy et al [ 11 ] and Raredon et al [ 17 ], this could be offset by the addition of a 22 mm bypass circuit between the inspiratory and expiratory ports of the ventilator to ensure equal inspiratory and expiratory gas volume and pressure at the expiratory port of the ventilator. However, the addition of a bypass circuit could result in cross contamination [ 11 ].…”

“…According to Roy et al [ 11 ] and Raredon et al [ 17 ], this could be offset by the addition of a 22 mm bypass circuit between the inspiratory and expiratory ports of the ventilator to ensure equal inspiratory and expiratory gas volume and pressure at the expiratory port of the ventilator. However, the addition of a bypass circuit could result in cross contamination [ 11 ]. To avoid this drawback, the interpose of a one-way valve in the bypass circuit is recommended [ 11 ].…”

“…Unidirectional valves inhibit the flow in undesired directions in both the inspiratory and expiratory phase. A 15 cm long and 6-mm bore bypass circuit between the expiratory and inspiratory limbs bypasses flow parallel to the two paired units in order to ensure predictable behavior of the ventilator [ 11 ].…”

Design for the Automation of an AMBU Spur II Manual Respirator

“…Some manual respirators are equipped with a pressure valve, which protects the patient's lungs from overpressure, while other complements can be used to ensure a minimum threshold pressure throughout the cycle (PEEP valves) [12]. Expired gasses, except for a few special cases like divided respirators, are released to the atmosphere without any processing [13].…”