Self working water-based instrument for positive expiratory pressure by resistance device and its effectiveness in improving oxygenation in acute pulmonary edema, during the COVID 19 pandemic: A pilot study

Akhil Paul; Susana Mathew

doi:10.4103/jalh.jalh_26_21

ORIGINAL ARTICLE

Year : 2022 | Volume : 2 | Issue : 3 | Page : 92-97

Self working water-based instrument for positive expiratory pressure by resistance device and its effectiveness in improving oxygenation in acute pulmonary edema, during the COVID 19 pandemic: A pilot study

Akhil Paul, Susana Mathew
Department of Pulmonary Medicine, MOSC Medical Mission Hospital, Thrissur, Kerala, India

Date of Submission	28-Dec-2021
Date of Acceptance	26-Jan-2022
Date of Web Publication	17-Aug-2022

Correspondence Address:
Dr. Akhil Paul
MOSC Medical Mission Hospital, Kunnamkulam, Thrissur - 680 503, Kerala
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jalh.jalh_26_21

Abstract

Background: About 20% to 67% of COVID 19 infected patients who are admitted to the hospitals and 100% of mechanically ventilated patients suffer from acute respiratory distress syndrome. Extrinsic positive expiratory pressure (PEP) can improve oxygenation by direct and indirect mechanisms, thus reducing the need of medical oxygen. But high-budget and sophisticated machines are required to provide this positive airway pressure, adding on to the treatment cost of the patient and investment expenditure by the health-care facilities. We have designed a simple self-working device called self-working water-based instrument for positive expiratory pressure by resistance (SWIPER) device which can provide a PEP. The objective of this study was to assess the effectiveness of this device in improving oxygenation in patients with acute pulmonary edema, which was quantified using pulse oximetry.
Methods: Patients who were admitted to the medical intensive care unit during the study period, with an acute pulmonary edema-a diagnosis which was made clinico-radiologically, were chosen as the subjects for the study. Once the patients were critically stabilized by the already existing treatment protocols, the SWIPER device was applied.
Results: The device was introduced on 15 patients who were selected after applying the inclusion-exclusion criteria of the study. The mean age of the study group was 65 years (men-64 years, Women-66 years). Eight of them had cardiogenic pulmonary edema whereas seven of them had nephrogenic pulmonary edema. The median baseline SpO₂level was 90% (86%, 94%) and the median plateau SpO₂level after using the SWIPER device was 94% (91%, 99%) (*P < 0.001). The mean rise in SpO₂on using the device was 6% (1.89) which was clinically significant.
Conclusion: SWIPER device is effective in significantly increasing the SpO2 in patients with acute pulmonary edema by providing a PEP. This device is not a replacement for the existing positive airway pressure-providing electrical devices. However, SWIPER devices will definitely come in handy in resource-limited settings in providing better treatment and care till the standard therapeutic measures are obtained. It will also help in significantly reducing the medical oxygen consumption in managing such patients.

Keywords: Acute respiratory distress syndrome, COVID 19, oxygenation, positive expiratory pressure, pulmonary edema, self-working water-based instrument for positive expiratory pressure by resistance device

How to cite this article:
Paul A, Mathew S. Self working water-based instrument for positive expiratory pressure by resistance device and its effectiveness in improving oxygenation in acute pulmonary edema, during the COVID 19 pandemic: A pilot study. J Adv Lung Health 2022;2:92-7

How to cite this URL:
Paul A, Mathew S. Self working water-based instrument for positive expiratory pressure by resistance device and its effectiveness in improving oxygenation in acute pulmonary edema, during the COVID 19 pandemic: A pilot study. J Adv Lung Health [serial online] 2022 [cited 2023 Jun 11];2:92-7. Available from: https://www.jalh.org//text.asp?2022/2/3/92/353871

Introduction

The ongoing COVID 19 pandemic which broke out in December 2019 has infected over 1.5 billion people worldwide, claiming over 3.2 million lives so far.^[1] Many nations, even the developed countries were struggling to manage the exponentially increasing number of infected cases due to a lack of hospital beds, intensive care units, ventilators, and workforce. Adding to this is the lack of sufficient medical oxygen supply.^[2] About 20%^[3] to 67%^[4] of COVID 19-infected patients who are admitted to the hospitals and 100% of mechanically ventilated^[5] patients suffer from acute respiratory distress syndrome (ARDS), a type of noncardiogenic pulmonary edema. This pathophysiology decreases lung compliance and demands a high flow of medical oxygen to maintain arterial oxygen levels in the affected patients. Extrinsic positive expiratory pressure (PEP) can improve oxygenation by direct and indirect mechanisms, thus reducing the need of medical oxygen. However, costly and sophisticated machines are required to provide this positive airway pressure, adding on to the treatment cost and investment expenses by the healthcare facilities.

We have designed a simple self-working device called self-working water-based instrument for positive expiratory pressure by resistance (SWIPER) device which can provide a PEP. The objective of this study was to assess the effectiveness of this device in improving oxygenation in patients with acute pulmonary edema, which was quantified using pulse oximetry.

Methods

Self-working water-based instrument for positive expiratory pressure by resistance device: The device comprises two parts

A lower part is a bottle with an inner tube extending from 5 cm outside the bottle mouth to a distance of 3 cm proximal to the bottle base. The inner tube is fixed at the bottle mouth. Another opening at the neck of the bottle is to fill water in the bottle according to the measurement scale in “centimeters” displayed outside the bottle.

The upper part is a modified mask which acts as an interface between the patient and the lower part of the bottle. The mask can be easily fixed to the inner tube extending out of the bottle, via a 15 cm flexible tube. The mask has two valves on each side which will open on inspiration, allowing the air to get into the mask and it will close during expiration guiding the expired air only through the inner tube into the water column in the bottle. It also has an opening to which external medical oxygen tube can be connected and it can be closed when no external oxygen is required, maintaining a closed system. The mask had straps to attach it tightly to the patient's face without air leak. The schematic representation of the device is given in [Figure 1] and the original photograph of the device is given as [Figure 2].

Figure 1: Self-working water-based instrument for positive expiratory pressure by resistance device. A- Inner tube, B- Connector, C- External opening, D- Marking in centimeters, E- Bottle with the water column, F- Inspiratory valve, G- Face mask, H- Oxygen port, I- Mask cushion, J- Straps

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Figure 2: Original photo of the device

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The pilot study was conducted for 6 months from November 1, 2020, to April 30, 2021, in a secondary mission hospital in south India. Patients who were admitted to the medical intensive care unit during this period, with acute pulmonary edema, a diagnosis which was made clinico-radiologically, were chosen as the subjects for the study. Those who were hemodynamically unstable requiring ionotropic support, ongoing arrhythmias, lower respiratory tract infections and those who required support to maintain SpO₂ over 80% were excluded from the study. Standard adult size face mask was used in the device and the size of the mask did not affect the study, as all the patients had a good fit of the mask. There were no obese patients as subjects for the study, even though obesity was not an exclusion criterion.

Preself-working water-based instrument for positive expiratory pressure by resistance device phase

Once the patients were critically stabilized by the already existing treatment protocols, their baseline SpO₂ levels were assessed by a pulse oximeter and it was recorded.

Self-working water-based instrument for positive expiratory pressure by resistance device phase

Then SWIPER device with 10 cm H₂O of water in the bottom part was introduced for 10 min. The plateau SpO₂ level and the time taken to reach the plateau in minutes were recorded.

Postself-working water-based instrument for positive expiratory pressure by resistance device phase

After 10 min, the device was disconnected and the time in minutes taken by the SpO₂ to fall back to the baseline was recorded.

No external medical oxygen was used during the study period. The median change in the SpO₂ level from the baseline value in the pre SWIPER device phase and the plateau value in the SWIPER device phase was calculated. A change of 4% or more was considered to be clinically significant based on the studies on 6 min walk test.^[6] Mood's median test was used to find the statistical significance between the medians. Data were presented as mean standard deviation and median (min, max). The study was approved by the Institutional Review Board and the ethics committee. Informed consent was obtained from the subjects.

Results

The device was introduced on fifteen patients who were selected after applying the inclusion-exclusion criteria of the study. The clinical characteristics of the study subjects are given in [Table 1].

Table 1: Clinical characteristics of the subjects

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There were eight men and seven women in the study group. The mean age of the study group was 65 years (men-64 years, women-66 years). The youngest subject was of 45 years of age and the oldest was of 88 years of age. Eight of them had cardiogenic pulmonary edema whereas seven of them had nephrogenic pulmonary edema. Twelve of them had diabetes mellitus and twelve of them had systemic hypertension as the co-morbidities. Ten of them had both diabetes mellitus and systemic hypertension. The median baseline SpO₂ level was 90% (86%, 94%) and the median plateau SpO₂ level after using the SWIPER device was 94% (91%, 99%) (*P< 0.001). The mean rise in SpO₂ on using the device was 6% (1.89) which was clinically significant and the time taken to reach the plateau SpO₂ on using the device was 1 min in thirteen subjects and 2 min in two subjects. The mean time taken by SpO₂ to fall back to its baseline level on discontinuation of the device was 1.5 min (0.62).

Discussion

ARDS is diagnosed in a COVID 19 infected patient when the Berlin 2012 ARDS criteria^[7] is met, which includes (1), Acute hypoxemic respiratory failure (2), presentation within 1 week of worsening respiratory symptoms (3), radiologically proven bilateral airspace disease which cannot be completely explained by collapse, effusion, or lung nodules, and (4) absence of cardiac failure as the primary cause for the presentation. ARDS causes diffuse alveolar damage of the lung. In the acute stage, there will be hyaline membrane formation in the alveoli and later in the organizing stage, it is followed by interstitial widening, edema, and fibroblast proliferation.^[8],[9] This hyaline membrane and the disruption of the alveoli decreases the diffusion of oxygen across this barrier and thus impairs arterial oxygenation. A high flow of oxygen will be required to rise the alveolar partial pressure of oxygen to effect the diffusion across the barrier. 53% of the COVID 19 ARDS death is attributed to this respiratory failure alone.^[10]

A PEP will come handy in such cases. The various mechanisms by which extrinsic PEP acts in improving oxygenation, ventilation, and patient stabilization are:

The applied PEP will increase the pressure in the airway, increasing the solubility of oxygen and thus its ability to diffuse through the alveolo-capillary membrane resulting in increased arterial oxygenation
It also splints the distal airways from collapsing during the end-expiration which will make the alveoli distal to it available for oxygenation during the next inspiration^[11]
The above mechanism will increase the alveolar ventilation minimizing the ventilation-perfusion mismatches^[12]
It decreases the work of breathing and thus increases the CO₂ and lactate production^[13],[14]
PEP will also decrease the preload and afterload of the left ventricle of the heart, decreasing the cardiac strain.

PEP for the management of cardiogenic or noncardiogenic pulmonary edema/ARDS is provided using dedicated noninvasive ventilatory machines like continuous positive airway pressure (CPAP) or BiPAP or by the invasive ventilators. However, such machines are expensive, which demands a larger investment by the hospitals and a higher cost of treatment for the patients. Furthermore, the high expiratory pressure from the device during the patient's expiratory phase will result in aerosol generation that can escape through the expiratory valves in the mask leading to a higher risk of infection transmission. As the COVID 19 pandemic continues to affect more and more people worldwide, there is a growing demand for such machinery and not all can afford it. The large volume of consumption of such devices and the hospital beds have led to the scarcity of the same, making the health system inefficient in providing adequate treatment for all.

High-flow nasal cannula is a preferred mode of providing oxygen to COVID 19 infected patients because of its added advantage of providing a PEP by the high flow oxygen.^[15] However, it consumes a lot of medical oxygen in the process and adds on to the current scenario of medical oxygen scarcity. In the absence of a PEP, the medical oxygen requirement for the management of these patients also increases. Our effort was to design a simpler and more effective device which can provide a PEP to these patients. The design of the SWIPER device was mentioned under “methodology.” When the SWIPER device is connected to a patient, during inspiration the valves on both sides of the mask will open and the air enters the circuit. If required, additional oxygen can be provided through the oxygen port which needs to be kept closed otherwise.

During expiration, the valves will close and the expired air will pass through the inner tube to the lower part, where the tube is immersed under a measured column of water. The length of the inner tube under the water will provide resistance to the flow of the expired air. The resistance can be adjusted by altering the water level in the bottle, according to the measurement in “centimeters” provided. For example, 10 cm of the inner tube under the water will provide a 10 cm H₂O of resistance, which will provide an equal amount of airway pressure according to Newton's third law. The expired air will bubble out through the water. Thus, this acts as a water-based positive airway pressure device. This same principle was used in bubble CPAP devices for neonates to prevent acute respiratory distress in them^[16],[17] and in bubble PEP devices used for pulmonary rehabilitation in chronic obstructive pulmonary disease,^[18] bronchiectasis,^[19] community-acquired pneumonia, etc.^[20] In this aspect, SWIPER device can be considered as a modified bubble CPAP device.

Neonates being obligate nose breathers, the pressure leak through the mouth is not significant and for pulmonary rehabilitation, the patient blows to the bubble PEP device through a mouthpiece. However to use the same principle to those patients with pulmonary edema, for a prolonged period, a modified interface was required. The described modifications in the mask were made to effect the process. The inner diameter of the inner tube was kept >2 cm and the length of the inner tube along with the flexible connector was 25 cm to nullify any added resistance.^[21] The study conducted by Santos et al. had proven that the therapist made bubble PEP device with 10 cm H20 water-filled and inner tube resting 3 cm above the bottle base provided PEP of 10.4 ± 0.14 to 10.8/−0.24 cm H₂O and oscillations between 13 and 17 Hz.^[22] They also concluded that it was the PEP device which provided a stable airway pressure throughout the range of flows tested. We also placed the inner tube at a level of 3 cm above the bottle base for the same reason.

The study was conducted in patients with acute pulmonary edema in whom no active infection was detected. Active infective cases were excluded to keep the infection containment policy of the institution intact in the present pandemic situation. Acute pulmonary edema was chosen as the target pathology as the lung physiology stayed closer to COVID 19 ARDS, which was found to be having better compliance than other ARDS^[23],[24] and more recruitability of the alveoli.^[25] The new device was applied only after stabilizing the patient using the existing standard treatment protocols and when it was found to be safer to stop the ongoing oxygen therapy for 10–15 min. External medical oxygen therapy was not given during the study time as the objective was to find out the difference in the oxygenation by the device alone.

The device was introduced on fifteen patients of which eight had cardiogenic pulmonary edema whereas seven of them had nephrogenic pulmonary edema. The median baseline SpO₂ level was 90% (86%, 94%) and the median plateau SpO₂ level after using the SWIPER device was 94% (91%, 99%) (*P< 0.001). The difference was statistically significant. The mean rise in SpO₂ on using the device was 6% (1.89) which was clinically significant. The lowest rise in SpO₂ was of 2% and in a patient who had a post-COVID 19 extensive lung fibrosis along with nephrogenic pulmonary edema. The extensive lung fibrosis could be the reason for the minimal change in SpO₂. Another low rise of SpO₂ was of 3%, but the baseline SpO₂ value in that patient was 94% and a comparatively better baseline value could have been the reason for that clinically insignificant improvement.

Four patients had an improvement of 8% in SpO₂. A study with ongoing oxygen therapy would have shown more significant results as the PAP will increase the oxygen diffusion across the alveolar membrane and increase its solubility. During this study there was no significant change in the heart rate, respiratory rate or blood pressure of the subjects and the patients also did not complain of any discomfort. High-efficiency particle air filters need to be attached to the external opening of the bottle (for the escape of expired air and pouring in the water) for adequate infection transmission prevention if used in an infected patient.

The advantages of the SWIPER device:

It is less expensive
It is easy to assemble
It is self-working without the need of electricity
The PEP can be adjusted easily by adding or removing water
As the PEP is produced by the patient's expiration itself, the process is well synchronized and the discomfort feeling is much lesser for the patients
The added advantage of the bubble oscillations will help in secretion clearance from the airway.^[19],[20]

Clinical application of SWIPER device:

It provides PEP in treating pulmonary edema (e.g., COVID 19 ARDS), which improves oxygenation
It decreases the oxygen consumption on the treatment of pulmonary edema
It helps in the clearance of the secretions from the airway^[19],[20]
It will help in avoiding dynamic hyperinflation in patients with obstructive airway diseases^[18]
It can be used at home for patients with recurrent episodes of acute pulmonary edema
It can be used for clinical improvement of the respiratory symptoms during active COVID 19 infection, the cytokine storm following that and later for pulmonary rehabilitation, at home as well as at a health care facility.

This study had the limitation of having a low sample size. Much larger studies are required to find out the role of the device in acute presentation as a mode to stabilize the patient and also to look at the impacts and effects of the device on the prolonged duration of usage. However, this study introduces a new instrument which can be handy in limited-resource settings to treat the patients with acute pulmonary edema in a better way and to reduce the oxygen consumption for the same, especially in the scenario of the ongoing COVID 19 pandemic.

Conclusion

SWIPER device is effective in significantly increasing the SpO₂ in patients with acute pulmonary edema by providing a PEP. This device is not a replacement for the existing positive airway pressure-providing electrical devices. However, SWIPER devices will definitely come in handy in resource-limited settings in providing better treatment and care till the standard therapeutic measures are obtained. It will also help in significantly reducing the medical oxygen consumption in managing such patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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