Pediatric Valved Holding Chamber Facemask Leakage at Clinically Relevant Application Forces

Introduction

Effective aerosol therapy in pediatric populations, particularly among children under 4 years of age, reveals unique clinical challenges. The use of pressurized metered-dose inhalers combined with valved holding chambers (VHCs) and facemasks is a widely endorsed method for delivering inhaled medications in this population, as recommended by national and international respiratory guidelines (Nationale VersorgungsLeitlinie Asthma V5.0, Global Strategy for Asthma Management and Prevention 2025). However, the efficacy of this system critically depends on the integrity of the facemask seal, which is influenced by mask design and the applied force during administration (Häselbarth J et al., Acta Paediatr. 2020; 109(3): 565–572). A poor seal resulting from mask-to-face leakage or an ill-fitting mask can substantially reduce pulmonary aerosol deposition and cause discomfort, further compromising therapeutic effectiveness (Nikander K et al. J Aerosol Med Pulm Drug Deliv. 2014; 27 Suppl1: S4–S23).

While regulatory standards for in vitro performance testing prescribe a relatively high, fixed application force of 16 N (equivalent to a weight of 1.6 kg) to ensure a tight facemask seal (US Pharmacopeia<1602>Spacers and Valved Holding Chambers Used with Inhalation Aerosols—Characterization Tests), such conditions do not reflect clinical reality. In real-world settings, caregivers generally apply significantly lower forces when holding the mask to a child’s face. Data indicate that children aged 1–4 years typically tolerate application forces closer to 4 N, which corresponds to a weight of approximately 408 g (Minh KT et al., J Aerosol Med Pulm Drug Deliv. 2014; 27 Suppl 1:S55–S62). This discrepancy raises concerns regarding the clinical significance of laboratory-based performance assessments for pediatric inhalation masks and underscores the potential for facemask leakage under practical conditions.

To address these issues, the present study aimed to compare the leakage performance of six commercially available pediatric VHC facemask systems designed for use in infants and young children. Seal integrity was evaluated across a broad range of applied forces, including both clinically relevant and regulatory-recommended levels. By aligning testing conditions more closely with real-world clinical scenarios, this study seeks to generate data that more accurately inform clinical practice as well as future pediatric face mask design.

Methods

To assess the sealing performance of VHC facemasks for infants and young children, two face models from the Louis Infant Anatomical Face Model (LIAM) family were used. These models were developed based on high-resolution 3D scans of children aged 2–18 months and 18 months to 5 years, captured with a structured light scanner (Winzen et al. Respiratory Drug Delivery. 2022; 315–320). Two faces were selected based on their representativeness for the corresponding age group. LIAM face models accurately replicate the facial geometry and varying tissue firmness of pediatric patients. The infant-sized mask of each VHC system was tested on the LIAM Baby model (9 mo), while child-sized masks were evaluated on the LIAM Infant model (2–3 y). Six VHCs and their corresponding infant and child masks were evaluated: Able Spacer (Clement Clarke), AeroChamber Plus Flow-Vu (Trudell), L’Espace (Air Liquide), OptiChamber Diamond (Philips Respironics), RC-Chamber (CEGLA), and VORTEX (PARI).

Measurements were conducted using a custom-built apparatus designed to ensure reproducible and standardized leakage measurements ([Fig. 1]). Leakage between masks and face models was determined as the difference between the flow rate upstream of the VHC (FR_up) and the flow rate downstream of the LIAM face model (FR_do), normalized by a constant reference flow of FR_ref=30 L/min. The leakage rate was calculated using the following equation: leakage [%]=((FR_do – FR_up)/FR_ref)×100. A defined application force ranging from 2 N to 16 N was applied using a force gauge, and the corresponding leakage flow was recorded. Prior to each test series, preliminary seal integrity assessments were conducted to determine the position of minimal leakage, ensuring the optimal mask placement of each face mask on the respective face models. Each mask was tested using three replicate devices, each measured four times, resulting in 12 measurements per condition. Leakage rates were presented as mean±SD (standard deviation). Statistical analysis was performed using one-way analysis of variance (ANOVA) with a significance level of α=0.05. Post-hoc comparisons were conducted using Tukey’s honest significant difference (HSD) test, and results were consistent with Fisher’s least significant difference (LSD) method.

Fig. 1. A schematic diagram of the experimental set-up measuring the leakage performance of VHC face masks. VHC, valved holding chamber.

Results

At a clinically relevant application force of 4 N, the extent of leakage varied markedly across the evaluated VHC infant masks ([Fig. 2]). A one-way ANOVA revealed statistically significant differences between most infant mask types. Pairwise post-hoc comparisons (Tukey’s test) showed that VORTEX (2.2±0.17%) and L’Espace (4.0±2.5%) had significantly lower leakage rates than the other four tested infant mask types. An OptiChamber Diamond (17.4±4.1%) sealed significantly better than a RC-Chamber (35.9±1.8%) and an AeroChamber Plus Flow-Vu (36.3±2.8%). The Able Spacer infant mask exhibited the highest leakage (94.8%±1.2), significantly exceeding that of all other masks and reflecting an ineffective mask-to-face interface under the applied force conditions. Among the VHC child masks, statistical analysis also revealed significant differences in leakage rates ([Fig. 2]). The VORTEX (1.3±0.5%) and RC-Chamber (4.3±1.8%) exhibited the lowest leakage, with VORTEX showing significantly lower values than the OptiChamber Diamond (8.4±4.8%), AeroChamber Plus Flow-Vu (10.6±1.7%), and L’Espace (18.9±7.8%). The RC-Chamber demonstrated significantly less leakage than AeroChamber Plus Flow-Vu and L’Espace. The AbleSpacer child mask failed to achieve an effective seal under the applied test conditions and was therefore excluded from the comparative analysis. Across all measured forces (2–16 N), VORTEX, OptiChamber Diamond, and L'Espace masks demonstrated relatively consistent leakage patterns for both infant and child versions with VORTEX showing the most effective and consistent seal ([Fig. 3]). AeroChamber Plus Flow-Vu and RC-Chamber masks showed force-dependent leakage, suggesting that their performance may vary with caregiver-applied pressure. The Able Spacer exhibited the highest leakage, with the child mask failing to achieve any effective seal.

Fig. 2. Leakage rates of commercially available VHC infant and child masks measured at a clinically relevant application force of 4 N. Data are presented as mean±SD. Statistical analysis was performed using one-way ANOVA with a significance level of α=0.05. Post-hoc comparisons were conducted using Tukey’s honest significant difference (HSD) test. Statistically significant differences in leakage were observed among most mask types. Non-significant comparisons within each age group are indicated by ‘n.s.’, whereas all other pairs showed statistically significant differences. For improved visualization, AbleSpacer face masks (leakage rates>94.8%±1.2) were excluded from this graph. ANOVA, analysis of variance; SD, standard deviation; VHC, valved holding chamber.

Fig. 3. Leakage of commercially available VHC infant (left) and child (right) masks across a range of application forces (2–16 N). Leakage is shown as mean±SD. SD, standard deviation; VHC, valved holding chamber.

Conclusions

Significant differences in facemask leakage were observed among various VHC mask designs across a wide range of application forces, highlighting the critical role of mask selection in pediatric inhalation therapy. The force applied by caregivers can vary substantially depending on the situation, directly impacting mask seal integrity and, consequently, drug delivery efficiency. VHC masks that maintain a reliable seal across a broad range of force levels—such as the VORTEX infant and child masks—may provide more consistent drug delivery regardless of the caregiver technique. Particularly in children requiring frequent inhalation therapy, masks that achieve an effective seal with minimal applied pressure can reduce both leakage and patient distress, thereby enhancing overall treatment effectiveness.

Ongoing efforts to optimize facemask design and align testing standards with real-world usage are warranted, so that young children receive the full benefit of inhaled treatments in practice. By choosing VHC masks with proven sealing performance and educating caregivers on achieving a good mask seal, healthcare providers can help in improving therapeutic outcomes for infants and children with respiratory illnesses.

Key messages

• Facemask leakage can substantially reduce the effectiveness of drug delivery in pediatric patients using VHCs with pressurized metered-dose inhalers.

• The sealing performance of pediatric VHC masks is influenced by both the mask design and the level of application force applied by caregivers during use.

• Observed variability in leakage among different VHC facemasks underscores the critical importance of mask selection for ensuring effective inhalation therapy in children.

Conflict of Interest

Andrea Winzen is employed by PARItec GmbH. Yvonne Burmeister is employed by PARI GmbH.

Publication History

Received: 02 August 2025

Accepted after revision: 05 November 2025

Article published online:
12 December 2025