The Partial Pressure of Oxygen Under Long-Term Oxygen Therapy With Various Types of Face Masks

During the COVID-19 pandemic, wearing a mask was mandatory in many countries (1). Face masks might have an impact on the partial pressure of oxygen (pO₂) in patients on long-term oxygen therapy. Data on the true extent of this effect are sparse. The aim of this study was to assess the effect of different mask types on pO₂ and other vital parameters.

Methods

Study population, study design, and data collection

The pilot study was conducted as a prospective observational pilot study at the Center for Pulmonology in Donaustauf, Germany in 2023.

In patients on long-term oxygen therapy, various clinical parameters were tested one after another on the same day at rest without a mask, with a surgical mask, with a well fitted FFP2 mask, and with a FFP3 mask. The order of mask type was randomized. Masks were used for 15 minutes before measurements were performed. Lung function tests (total lung capacity [TLC], forced vital capacity [FVC], forced expiratory volume in 1 second [FEV₁], diffusion capacity [TLCO]) were evaluated if available. The parameters measured were dyspnea, assessed using a modified Borg scale (2), respiratory rate, blood pressure, heart rate, and earlobe arterialized capillary blood gas analysis parameters.

The study was approved by the local ethics committee (no. 22–3165–101) of the University of Regensburg. Written informed consent was provided by all participants.

Statistics

Data were analyzed using IBM SPSS Statistics 29.0 with a general linear model, with mask type as fixed factor and the individual patient as random factor. Summary statistics of continuous variables are presented as median and interquartile range.

Results

Baseline characteristics

Twenty-five patients participated; three of them were excluded because their measurement data (blood gas analysis parameters) were incomplete. Twenty-two patients (mean age: 69 ± 7 years, 41% female, mean body mass index 31 ± 20 kg/m²; mean oxygen therapy 3.7 l/min (min 1 l/min, max 15 l/min) were included, 17 of whom had chronic obstructive pulmonary disease and five, interstitial lung disease. Lung function test data were available for 19 patients, among them 13 patients with an obstructive, three with a restrictive, and one with a combined obstructive and restrictive ventilatory impairment.

Clinical parameters

Wearing a mask (of any type) had an impact on pO₂ but no effect on other clinical parameters such as breathing rate, heart rate, or pCO₂ (Table).

Table

Clinical parameters

Discussion

In our study patients receiving oxygen therapy via a nasal cannula had a higher pO₂ while using any type of mask (surgical mask, FFP2, FFP3). To our knowledge, this is the first time that this effect has been described in patients with pulmonary disease. These findings might assist in formulating future recommendations on mask wearing by patients on oxygen therapy.

Brown et al. reported that the addition of surgical masks to oxygen therapy can increase the inspired oxygen fraction and improve the performance of the devices (nasal cannula and manikin nasal cannula) by more than a third, but their study was conducted in healthy volunteers without prior prescribed oxygen therapy (3).

In the outpatient setting, oxygen therapy is titrated by office-based pulmonologists. During the pandemic, wearing a mask was a condition for access to patient care. Taking this into account, normal pO₂ measurements could have resulted in hypoxemia in other settings. On the other hand, face masks could lead to hypercapnia due to increased respiratory resistance (4).

Our study has several limitations: it was a single-center study with a small number of participants; the measurements were conducted only at rest; exercise testing with masks might lead to different results. The results also do not permit any conclusions on the effect of wearing masks continuously for a longer period (e.g., several hours).

Arno Mohr, Maria M. Mercado, Nina M. Sicker, Stefanie Zahn, Michael Pfeifer, Maximilian V. Malfertheiner, Bernd Salzberger, Florian Hitzenbichler, Florian Geismann

Department of Pulmonology, Respiratory Medicine, and Infectiology, Inn Hospital Mühldorf, Mühldorf am Inn (Mohr), [e-mail]

Center for Pulmonology, Donaustauf Hospital, Donaustauf (Mohr, Mercado, Sicker, Zahn, Pfeifer, Malfertheiner, Geismann)

Department of Internal Medicine II, University Hospital Regensburg, Regensburg (Geismann, Mohr, Malfertheiner)

Department of Pulmonology and Conservative Intensive Care Medicine, Barmherzige Brüder Hospital, Regensburg (Mercado, Pfeifer)

Department of Hospital Hygiene and Infectiology, University Hospital Regensburg, Regensburg (Salzberger, Hitzenbichler)

Conflict of interest statement
The authors declare that no conflict of interest exists.

Submitted on: 25 March 2024, revised version accepted on 17 July 2024

Cite this as:
Mohr A, Mercado MM, Sicker NM, Zahn S, Pfeifer M, Malfertheiner MV, Salzberger B, Hitzenbichler F, Geismann F: The partial pressure of oxygen under long-term oxygen therapy with various types of face masks. Dtsch Arztebl Int 2024; 121: 884–5. DOI: 10.3238/arztebl.m2024.0153

References

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4. Schönhofer B, Rosenblüh J, Kemper P, Voshaar T, Köhler D: Einfluss des Mundschutzes auf die Atemarbeit bei Patienten mit chronischer Belastung der Atempumpe. Pneumologie 1995; 49 Suppl 1: 209–11.