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. 2025 Jul 23:12:1538280.
doi: 10.3389/fmed.2025.1538280. eCollection 2025.

Effects of different exhalation valves on CO2 rebreathing and ventilator performance during noninvasive ventilation

Xinyu Li  1 , Bing Dai  1 , Chengguang Zhou  2 , Haijia Hou  1 , Shengchen Wang  1 , Xiangrui Li  1 , Hongwen Zhao  1 , Wei Wang  1 , Wei Tan  1
Affiliations

Effects of different exhalation valves on CO2 rebreathing and ventilator performance during noninvasive ventilation

Xinyu Li et al. Front Med (Lausanne). .

Abstract

Background: Noninvasive ventilation (NIV) is widely used to improve oxygenation and reduce carbon dioxide (CO2) retention in patients with respiratory failure. However, it remains unclear whether different types of exhalation valves affect CO2 rebreathing and ventilator performance during NIV.

Methods: Three noninvasive ventilators (V60, Flexo, and Stellar150) with single-limb circuits and four different exhalation valves (single-arch, whisper swivel, plateau exhalation, and vented mask valves) were separately connected in series to a lung simulator. CO2 gas was injected from the simulated lung outlet, maintaining the end-expiratory CO2 (PetCO2) at 80 mmHg. Both the CO2 rebreathing volume (CO2REB) and the parameters displayed on the lung simulator and ventilator were recorded under each condition.

Results: The mean CO2REB values of the four aforementioned valves were 18.51 ± 2.87, 18.25 ± 2.73, 17.78 ± 2.98, and 14.26 ± 0.92 mL/breath, respectively, with no significant differences among the first three types but all significantly higher than that of the mask valve (all p < 0.0001, rate of difference > 10%). Except with the V60 ventilator, some ventilator performance parameters (triggering and control performance) were significantly lower for the plateau valve than for the others, the rate of difference in tidal volume (VT) between the ventilator and the simulated lung exceeded 10% for all exhalation valves (all p < 0.01).

Conclusion: Mask valves showed significantly lower CO2 rebreathing than circuit-located valves (single-arch, whisper swivel, and plateau exhalation) in this NIV bench study. The different valves influenced ventilator performance differently, particularly the plateau valve. These findings necessitate further clinical validation in vivo.

Keywords: CO2 rebreathing; exhalation valves; noninvasive ventilation; plateau exhalation; ventilator performance.

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Conflict of interest statement

CZ was employed by Shenyang RMS Medical Tech Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Illustration of the experiment. (A) Measuring the intentional leak of the exhalation valves, (B) schematic diagram of experimental setup, (C) time curve of flow and CO2 concentration and the equation, (D) graphic explanation of the ventilator parameters.
Figure 2
Figure 2
The leakage of different exhalation valves.
Figure 3
Figure 3
The CO2REB of different exhalation valves under different conditions. (A) Comparison under different pressure settings (IPAP/EPAP = 12/4 and 16/4 cmH2O); (B) Comparison at different breathing frequencies (10, 15, and 25 breaths/min); (C) Comparison across different ventilator types (V60, Flexo, and Stellar150). * Significantly higher than IPAP = 12cmH2O (p < 0.01), # significantly lower than other exhalation valves (p < 0.01), & significantly lower than f = 10/15 breaths/min (p < 0.01).
Figure 4
Figure 4
Effects of different exhalation valves on ventilator performance. (A) Triggering parameters (Ttrig, Tpmin and Ptrig); (B) control parameters (T90%, Ti, PIP, PIF, MIF and PEEP); (C) tidal volume displayed on the lung simulator (VT-L). # significantly lower than other exhalation valves (p < 0.01).
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