Feasibility study of a low-cost powered air-purifying respirator (PAPR): A hospital-based simulation study to assess the perception of healthcare professionals

INTRODUCTION

In healthcare settings with risk of disease transmission through contact, droplets, and airborne particles,^1,2 healthcare workers need to use appropriate personal protective equipment (PPE).³ These include: (i) eye and face protection, (ii) hand protection, (iii) body protection, (iv) hearing protection, and (v) respiratory protection.⁴ For respiratory protection, two types of air-filtering respirators are used, namely filtering facepiece respirators (FFRs) and powered air-purifying respirators (PAPRs). The most common FFR is the N-95 respirator, also referred to as N-95 mask. N-95 masks are designed for close facial fit and filter at least 95% of airborne particles larger than 0.3 microns from the inhaled air.⁵ As per Occupational Safety and Health Administration (OSHA) of the USA, PAPR is defined as ‘air-purifying respirator that uses a blower to force the ambient air through air-purifying elements to the inlet covering’.⁶

Efficacy of respirators is measured as assigned protection factor (APF), i.e. the protection a respirator offers when the wearer follows the respiratory protection rules.⁵ The APF values of N-95 mask and hood-powered PAPR, are 10 and 25, respectively, indicating that the latter provides more effective filtration.

The two types of respirators have other advantages and limitations. Some healthcare workers report headache following the use of N-95 masks,⁷ which can be mitigated by using PAPR.⁸ On the other hand, PAPRs have the disadvantages of noise that may impact hearing,^9–14 high cost, large size, and a time-consuming donning and doffing process.¹⁵ Moreover, inadequate air flow rate in a tight-fitting PAPR may impair the worker’s performance, facial cooling, and respirator comfort.¹⁶

During an outbreak of severe acute respiratory syndrome (SARS), the majority of healthcare workers (84%) preferred PAPR over N-95 masks.¹⁷ In a study simulating the typical hospital environment, users preferred PAPRs over N-95 mask in 11 of 16 preference categories.¹⁸ In a low-temperature environment during low to moderate work for one hour, there was no significant difference between the N-95 and PAPR in the measurements of cardiopulmonary variables, facial and overall body heat perception, and perceived breathing ability.¹⁹ In a field observation study, it was found that those respondents wearing PAPR had a higher heat tolerance but were limited by low mobility and audibility.^20,21

In India, PAPRs are, for the most part, imported and hence expensive (around ₹100 000 or US$ 1280 each) and thus unaffordable.

Engineers of our university developed a low-cost PAPR (₹30 000), with the aim of making PAPR affordable, while mitigating the drawbacks of the N-95 masks, namely facial heating, a sensation of suffocation, and fogging of the face shield. After working on 3 progressively enhanced prototypes, a final low-cost PAPR^22,23 has been developed,²⁴ with features of a PAPR as per the National Institute for Occupational Safety and Health (NIOSH) standards and a higher airflow rate.²⁵ It is in the process of certification.

A major factor deciding the choice of a respirator is the perceived comfort of healthcare workers in delivering patient care after donning these. We assessed the feasibility for use of the low-cost PAPR in a hospital setting, based on the perception of healthcare workers as compared to the N-95 mask system while performing routine hospital tasks.

METHODS

Twenty female nurses with a mean (SD) age of 25.8 (1.8) years who had at least 1 year of professional experience (mean [SD] 2.9 [1.6]) years in current position) and provided informed consent were included in the study. They had prior experience of using an N-95 mask for 4.0 (2.7) months but had no prior experience of using a PAPR. They were trained in donning and doffing of the low-cost PAPR through videos and instruction manuals for one week prior to the study.

The participants rated their prior experience with the tasks to be performed in the study using a 3-point Likert scale (‘very experienced,’ ‘somewhat experienced,’ or ‘inexperienced’). Thereafter, each participant underwent two sessions, wearing one of the two respirators being compared in turn, and performed six nursing tasks––(i) recording vital signs, (ii) communication with and counseling of patient and bystanders, (iii) taking care of patients’ dietary needs, (iv) moving the patient from bed to wheelchair, (v) back care (cleaning and massaging the back to stimulate circulation, prevent bedsores, and provide emotional relaxation), and (vi) bed making. The order in which the two respirators were worn was haphazard.

During the two sessions, the participants wore PPE comprising a full body suit and gloves, and one of the two respirators–– (i) the low-cost PAPR (Fig 1), or (ii) N-95 mask system (N-95 mask plus a face shield; Fig 2). The N-95 mask used (Aero 2N95 FFP2 mask head-loop with cord-lock [medium]) had Indian Standards Institution certification. The PAPR consisted of a hood, a breather tube, a blower and a 12 V lithium-ion battery; the battery and the blower were located in a backpack. The system had an airflow of 10 cubic feet per minute, noise level of below 70 db, and could operate for more than 10 hours a day. The hood was manufactured by a company that was certified by the International Organization for Standardization (ISO 13485:2016).

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FIG 1.

Low-cost powered air-purifying respirator (PAPR)

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FIG 2.

N-95 mask and face shield

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The sessions were conducted in a vacant 5-bed intermediate respiratory care unit (IRCU) at ambient temperature. Each participant was assigned one bed with a simulated patient (another study participant) for performing the tasks described above, while being observed by one of the investigators to ensure that the participant executed the assigned tasks correctly. The procedure was then repeated with the other respirator (Fig. 3).

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FIG 3.

Flow diagram of the sessions PPE personal protective equipment

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After each session, the participants were asked to rate their perception of comfort while performing the six nursing tasks in 16 domains, each using a Likert scale of 1–5 (Table I). They were also asked to indicate (Yes or No) whether they had experienced discomfort, in the form of back pain, dizziness or eye irritation, while doing the prescribed tasks. At the end of the PAPR session, they were also asked to rate whether they were able to perform a selection of assembly and donning tasks, the time taken to do these, and the level of comfort with certain aspects of wearing the PAPR (Table II).

Further, the participants were asked to indicate which respirator (‘PAPR’ or ‘N-95 mask’) they preferred, they perceived as more effective, and found more acceptable for doing low mobility tasks (tasks 5 and 6), medium mobility tasks (tasks 1 and 4), or high mobility tasks (tasks 2 and 3).

The participants had their vital signs measured before and after the six tasks in each session. These included axillary temperature (using a digital thermometer), pulse rate, peripheral arterial oxygen saturation (SpO₂) with a pulse oximeter, and respiration rate (by the participant counting the number of breaths). Changes in vital signs were obtained by subtracting the values before starting the tasks to the values after completing the tasks. The effect size ‘r’ was calculated for each Wilcoxon signed-rank test.

The participants were also interviewed regarding their experience using semi-structured interviews. The open-ended answers were coded and analyzed using a content analysis method.

The study was approved by our Institutional Ethics Committee and registered with Clinical Trials Registry–India (CTRI). The data were analyzed using the Wilcoxon signed-rank, Cochran’s Q, and McNemar tests, with Statistical Package for the Social Sciences (SPSS) version 25, at an α-level of 0.05.

RESULTS

DISCUSSION

The majority of study participants said that they were either very experienced or somewhat experienced with almost all the nursing tasks included in the study. When the perceived comfort of wearing the N-95 mask was compared with the low-cost PAPR, some categories of comfort were rated in favour of the PAPR. The main difference between the two respirators was that powered air was being supplied into the hood of the PAPR. With powered airflow, a PAPR could provide breathing comfort, reduce facial heat, sweating, and fogging. This was possibly the reason for participants’ preference for the PAPR for ‘more overall breathing comfort,’ ‘less facial and body heat,’ ‘less eye discomfort,’ and ‘more clear line of vision.’ Particularly the categories ‘overall breathing comfort’ and ‘clear line of vision’ showed a large effect size.

However, some categories were rated in favour of the N-95. During the PAPR session, the participants reported significantly more ‘pressure or pain,’ more ‘difficulty in donning,’ more ‘difficulty in operating the respiratory protection gear,’ less ‘flexibility during tasks,’ less ‘ability to hear properly,’ ‘fewer hours that they thought they could wear it continuously,’ and less ‘overall flexibility of the respiratory protection gear.’ These categories showed a medium effect size. The PAPR had numerous components, such as a blower, battery, breather tube hood, and waist bag, to be assembled before donning and to be disassembled for doffing. With the N-95 mask, only the mask and face shield had to be dealt with for donning and doffing. Fewer items on the body could provide more flexibility, less pressure or pain, and enable the participants to work for longer hours. The PAPR blower was noisy, and could be the reason for participants rating ‘communication’ in favour of the N-95 mask.

The participants’ preference, perceived effectiveness, and acceptance for a particular respirator showed significant differences depending on the mobility requirement of the task. A larger number preferred, perceived as effective, and accepted the PAPR for low mobility tasks, such as vital signs measurement and patient communications/counseling of bystanders. This could be due to airflow inside the hood of the PAPR, which gave the participants breathing comfort, but did not allow for flexibility of movement. The N-95 mask was preferred for high mobility tasks requiring much movement and bending, such as bed making and changing the patients’ position from bed to wheelchair. During the semi-structured interviews, the participants also mentioned that they would prefer the N-95 mask if they had to do cardiopulmonary resuscitation (CPR). These findings are in line with a similar study that found that 50% of the participants preferred the N-95 mask over three types of PAPRs because the N-95 mask was lightweight, easy to wear, and easy to use.¹⁸

When comparing bodily discomforts while wearing the N-95 mask versus the low-cost PAPR, the participants complained of back pain more frequently while using the PAPR. This could be due to the backpack of the PAPR that contained a battery weighing 1 kg. However, while using the N-95 mask, the participants had more eye irritation, feeling of suffocation, and subjective temperature rise. This could be due to the lack of airflow, which causes breathing difficulty, sweating, and fogging of the face shield, making it unsuitable for clear vision. Other studies had shown that the use of the N-95 masks as part of the PPE caused tiredness, fogging, headache, mask soakage, and breathing difficulties.²⁶

There were no significant differences in vital signs before and after tasks between the N-95 and PAPR. However, changes in vital signs need not be a strong indicator to evaluate the respirators, because there are other factors, such as the type of the tasks, that could cause changes in vital signs rather than the type of respirator.^19,27

When the ability of the participants regarding the assembly and donning of the PAPR was assessed, most participants were quite proficient. The most challenging part of the donning process was the breather tube connection, which needs to be improved in future constructions of the PAPR. Overall, most participants were satisfied with the comfort of the assembled parts of the PAPR.

In the interviews, the participants felt the N-95 mask was a good source of protection. could be especially useful for dealing with Covid-19 patients, high mobility tasks, and emergency patient care. However, the participants felt that the N-95 mask still needed improvement. Due to the lack of airflow, the N-95 mask caused sensations of increased facial heat, suffocation, sweating, and fogging. Some of the participants experienced communication difficulties while wearing the N-95 mask.

Regarding the PAPRs, participants felt the system was protective and had good airflow, a low sense of suffocation, and clear visibility. They preferred PAPR for low mobility tasks or tasks requiring fewer movements, due to lack of flexibility. The PAPR also led to communication issues due to the noise of the blower. Some of the participants felt that they could become used to the PAPR system in the long run, just as they became used to the N-95 mask, as none of them had any previous experience using a PAPR. Most of the participants also felt that the PAPR system could be more useful for doctors who did not perform many tasks that required much movement.

The limitations of our study include the small sample size. A larger and more representative sample would have yielded more generalizable results. All the participants had prior experience with using the N-95 mask, while none of them had used a PAPR before, this could have biased the results. We also did not include male nurses or doctors.