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| ORIGINAL ARTICLE |
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| Year : 2022 | Volume
: 2
| Issue : 2 | Page : 59-64 |
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A retrospective observational study of utility of nonrebreathing mask in moderate to severe hypoxemic COVID-19 pneumonia
Trinath Dash, Karthik Tipparapu, Sarvendra Vikram Singh, Koustav Roy
Department of Respiratory Medicine, JLNH&RC, Bhilai, Chhattisgarh, India
| Date of Submission | 13-Sep-2021 |
| Date of Acceptance | 09-Nov-2021 |
| Date of Web Publication | 17-May-2022 |
Correspondence Address:
Dr. Trinath Dash
Rose-108, A-block, Gate No- 2, Talpuri, Bhilai, Chhattisgarh
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/jalh.jalh_20_21
Introduction: The pulmonary manifestations of covid-19 disease may range from mild pneumonia to severe acute respiratory distress syndrome (ARDS) complicated by shock or multiorgan failure. Proper selection and utilization of oxygen delivery system is the key factor in treating the hypoxemic respiratory failure in severe covid-19 disease. Here by, we present a retrospective observational study of utility of NRBM (Non Rebreathing Mask) in 1876 moderate to severe hypoxemic Covid-19 pneumonia patients in a single centre and its outcome. Objectives: To study the utility of NRBM in moderate to severe hypoxemic COVID-19 pneumonia Patients. Material and Methods: This was a single centre retrospective observational study. Out of 5024 microbiologically confirmed (by Rapid antigen test/RTPCR/TRUENAT) covid-19 pneumonia patients admitted since September, 2020 to May 2021,1876 patients of age >14 years admitted in the department of Respiratory medicine with moderate to severe hypoxemia (SpO2 <90%) and respiratory rate <30/min who were provided supplemental oxygen by NRBM with or without associated Co-morbidities were included in the study. These patients were provided oxygen Supplementation by NRBM according to their SpO2 levels (<90 %) by starting with a minimum flow rate of 10 L/ min to maximum of 15 L/min. Results: Out of 5024 microbiologically confirmed covid-19 patients who were admitted in respiratory ICU and ward,1876 patients were provided supplemental oxygen by NRBM. Patients were distributed according to their duration of onset of symptoms, mode of oxygen delivery, number of days of supplemental oxygen and number of patients expired accordingly and results were observed and analyzed. Majority of the patients belongs to the age group 45 to 60 yrs. The average duration of presentation to ER with worsened symptoms for oxygen requirement was 6.4 days from the onset of symptoms. 1703 (90.77%) patients recovered well without any further deterioration with NRBM. The average duration of days for weaning from NRBM to simple face mask or nasal prongs were 4.5 days based on their respective SpO2 >90% (corresponds to Pao2 >60 mmhg), respiratory rate (<16/min) and heart rate <100 bpm. About 9.3% of the patients (173) who were provided NRBM support who further deteriorated or showed poor response even after maximum period of 7 days were provided with NIV support (130 patients i.e. 6.92%), HFNC support (14 patients i.e. 0.74%) and invasive mechanical ventilation (29 patients i.e. 1.54%).66 patients who were initially provided NRBM support, recovered and 107 patients (2.129%) succumbed to their illness. smoking (table-4)has been observed to be the major risk factor in majority of the patients (43.7%). As per the data of this study there is significant correlation between the utilization of NRBM and advanced age, early initiation of NRBM rather than directly initiating NIV/HFNC/Invasive mechanical ventilation and duration of presentation to the hospital with symptoms. Smokers were observed to be associated with more severe presentation and longer time for weaning. Hypertension and Diabetes were observed to most commonly associated comorbidities in the study population. Hypoxemic covid-19 patients who were provided NRBM support were having better outcome and reduced mortality risk compared to patients who were provided NIV/HFNC/Invasive mechanical ventilation. Conclusion: In reference to the results in our study, we recommend the use of NRBM in moderate to severe hypoxemic patients of covid-19 disease at the early course of the disease.
Keywords: COVID-19 pneumonia, hypoxemia, nonrebreathing mask, oxygen supplementing devices
How to cite this article:
Dash T, Tipparapu K, Singh SV, Roy K. A retrospective observational study of utility of nonrebreathing mask in moderate to severe hypoxemic COVID-19 pneumonia. J Adv Lung Health 2022;2:59-64 |
How to cite this URL:
Dash T, Tipparapu K, Singh SV, Roy K. A retrospective observational study of utility of nonrebreathing mask in moderate to severe hypoxemic COVID-19 pneumonia. J Adv Lung Health [serial online] 2022 [cited 2023 Jun 11];2:59-64. Available from: https://www.jalh.org//text.asp?2022/2/2/59/345376 |
| Introduction | |  |
COVID-19 disease by novel coronavirus (severe acute respiratory syndrome coronavirus 2) reported its first case on November-17, 2019, at Wuhan, China. It transformed into a global health emergency and was declared as pandemic by the World Health Organization on March 11, 2020. Globally, it affected approximately 23.9 crore people with nearly 48.7 lakh deaths (2.03%). In India, 3.4 crore cases were recorded till date with 4.5 lakh (1.3%) deaths (as on October 2021). The pulmonary manifestations of COVID-19 disease may range from mild pneumonia to severe acute respiratory distress syndrome (ARDS) complicated by shock or multiorgan failure.[1] This pandemic has presented several challenges in the optimal management of hypoxia. The current COVID-19 management guidelines by surviving sepsis suggest the use of supplemental oxygen if SpO2 is <92%.[2] Hereby, we present a retrospective observational study of utility of nonrebreathing mask (NRBM) in moderate to severe hypoxemic COVID-19 pneumonia patients in Department of Respiratory Medicine, JLNHandRC, 1000-bedded tertiary care hospital at Bhilai, Chhattisgarh.
Aim
The aim is to study the utility of NRBM in moderate to severe hypoxemic COVID-19 pneumonia patients.
| Materials and Methods | | |
This was a single-center retrospective observational study. Out of 5024 microbiologically confirmed (by rapid antigen test/RTPCR/TRUENAT) COVID-19 pneumonia patients admitted from September 2020 to May 2021, 1876 patients of age >14 years admitted to the Department of Respiratory Medicine with moderate to severe hypoxemia (SpO2 <90%) and respiratory rate (RR) <30/min who were provided supplemental oxygen by NRBM with or without associated comorbidities were included in the study. These patients were provided oxygen supplementation by NRBM according to their SpO2 levels (<90%) by starting with a minimum flow rate of 10 L/min to maximum of 15 L/min.
Patient inclusion criteria
Microbiologically confirmed COVID-19 patients with moderate to severe hypoxemia on SpO2 levels by using Philips IntelliVue MP20 monitor oxygen probe for at least 60 s at emergency room (moderate hypoxemia is when SpO2 <75%–90% on room; severe hypoxemia is when SpO2 <75% on room air).[3] Age more than 14 years, both males and females with or without any associated comorbidities.
Patient exclusion criteria
Age <14 years
RR >30/min (as the raised minute ventilation requirement due to extreme tachypnea may not be fulfilled by NRBM and will further worsen the hypoxemia).
Data analysis
Data collected were entered into MS Excel 2013 spreadsheet. The collected data were analyzed using IBM Statistical Package for the Social Sciences version 23 software (IBM-SPSS Statistics,Developers:Norman H. Nie, Dale H. Bent, C. Hadlai Hull, chicago, USA, trial version).
Statistical tests
Continuous variables were reported as mean ± standard deviation (SD) while categorical variables were expressed as absolute values and percentages.
Unpaired t-test and Chi-square test were applied to find significance between two groups and P < 0.05 at 95% confidence interval was considered as statistically significant.
| Results | | |
There is no significant gender variation in the utility of NRBM in hypoxemic COVID 19 pneumonia [Table 1].
With reference to [Table 2], in the patients of advanced age group, the utilization of NRBM increases with a statistically significant association. With reference to [Table 3], the mortality risk associated with NRBM utilization is low compared to direct utilization of NIV/HFNC/invasive mechanical ventilation and it is. Out of 5024 microbiologically confirmed COVID-19 patients who were admitted in respiratory intensive care unit and ward, 1876 patients were provided supplemental oxygen by NRBM. Patients were distributed according to their duration of onset of symptoms, mode of oxygen delivery [Table 4], number of days of supplemental oxygen, and number of patients expired accordingly and results were observed and analyzed. Gender and age distribution of patients are given in [Table 1] and [Table 4], respectively. Majority of the patients belongs to the age group 45–60 years. The average duration of presentation to ER with worsened symptoms for oxygen requirement was 6.4 days from the onset of symptoms. One thousand seven hundred and three (90.77%) patients recovered well without any further deterioration with NRBM. The average duration of days for weaning from NRBM to simple face mask or nasal prongs was 4.5 days based on their respective SpO2 >90% (corresponds to Pao2 >60 mmHg), RR (<16/min) and heart rate <100 bpm. About 9.3% of the patients (173) who were provided NRBM support who further deteriorated or showed poor response even after maximum period of 7 days were provided with noninvasive ventilation (NIV) support (130 patients, i.e., 6.92%), high flow nasal cannula (HFNC) support (14 patients, i.e., 0.74%), and invasive mechanical ventilation (29 patients, i.e., 1.54%). Sixty-six patients who were initially provided NRBM support recovered and 107 patients (2.129%) succumbed to their illness. Smoking [Table 5] has been observed to be the major risk factor in majority of the patients (43.7%). [Table 3] and [Table 6],[Table 7],[Table 8],[Table 9] show patient distribution according to various methods of oxygen support, associated comorbidities, duration of symptoms before initiation, mortality on different supports, and duration of support with NRBM. As per the data of this study, there is a significant correlation between the utilization of NRBM and advanced age, early initiation of NRBM rather than directly initiating NIV/HFNC/Invasive mechanical ventilation, and duration of presentation to the hospital with symptoms. Smokers were observed to be associated with more severe presentation and longer time for weaning. Hypertension and diabetes were observed to most commonly associated comorbidities in the study population. Hypoxemic COVID-19 patients who were provided NRBM support were having better outcome and reduced mortality risk compared to patients who were provided NIV/HFNC/Invasive mechanical ventilation. | Table 3: Comparison of mortality with nonrebreathing mask and other modes of high flow oxygen delivery systems
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 | Table 4: Distribution of the admitted patients as per their mode of oxygen delivery
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 | Table 6: Distribution of patients according to the duration of onset of symptoms and presentation
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 | Table 7: Distribution of patients according to the duration of support with nonrebreathing mask
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 | Table 8: Initiation of nonrebreathing mask and duration of onset of symptoms
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 | Table 9: Distribution of patients according to the duration of support with nonrebreathing mask
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| Discussion | | |
Hypoxemia is the most common presenting symptom in severe COVID-19 pneumonia. Pulmonary manifestations in the form of acute respiratory failure are the most common complication of severe COVID-19 disease. Higher SpO2 levels after oxygen supplementation were associated with reduced mortality independent of age and sex.[4] Oxygen supplementation is initiated when the SpO2% drops below 90%.[5] The normal range of partial pressure of oxygen in arterial blood (PaO2) is 80–100 mmHg. This corresponds to oxygen saturation of hemoglobin (SaO2) of 93% to 97% in the oxyhemoglobin dissociation curve (OHDC).[5] The OHDC is a sigmoid or Sshaped curve that represents the relationship between PaO2 and SaO2 in the arterial blood. The flat portion of the curve suggests that a significant change in PaO2 (80–100 mmHg) has small change in SaO2 (93%–97%) indicating that the patient's oxygenation status is better protected at this flat portion.[5] At the steep lower part of the curve where the PaO2 is between 40 and 60 mmHg, the change in SaO2 is drastic.[5] Clinically, this indicates that, when SpO2 drops below 90%, the patient can potentially suffer hypoxic damage.[5] Therefore, when the SpO2 reading falls below 93%–94%, it is alarming, as 90% corresponds to steeper drop in PaO2 between 40 and 60 mmHg because of the shape of the OHDC [Figure 1]. When patients present to the hospital with 60% or 70% O2 saturation, some tissue hypoxia and acidosis would have already set in. This must be avoided by early initiation of oxygen therapy.
Since the severity of disease is closely related to the prognosis, the basic and essential strategies to improve outcomes are early detection of high-risk and critically ill patients.[6],[7] Hypothesis postulated by Gattinoni et al.[8] may help us understand why these patients had different outcomes despite applying the same measures of respiratory support. It is hypothesized that COVID-19 can be characterized by 2 phenotypes: L and H.[8] Type L is characterized by normal compliance, which may explain why patients can be hypoxemic but not in severe respiratory distress.[8] Type H is characterized by low compliance and high lung weight, resembling typical severe ARDS physiology.[8] Proper selection and utilization of oxygen delivery system is the key factor in treating the hypoxemic respiratory failure in severe COVID-19 disease.
Description of nonrebreathing mask
A NRBM is similar to a partial rebreathing mask except for the presence of three one-way valves. Two of the one-way valves cover the exhalation port during inhalation, preventing room air from entering the mask during inspiration [Figure 2]. During exhalation, these valves allow the exit of expired gas from the mask. Another valve is located between the mask and the reservoir bag. This valve prevents expired gas from entering the reservoir bag during expiration. During inhalation, this valve opens allowing fresh gas to flow from bag to mask. The design minimizes dilution from room air and can deliver higher FIO2. Oxygen flow should be set high enough to prevent deflation of the reservoir bag–usually about at least >10 L/min. The capacity of NRBM bag is 2700 ml.
NRBM with a flow rate of >10 L/min to 15 L/min can provide Fio2 up to 80%–90%.[9],[10] When the patient is extremely tachypneic (RR >30/min), the raised minute ventilation requirement may not be fulfilled by NRBM and patient may further deteriorate with severe hypoxemia. The NRBM was used to prevent aerosolization of particles that may have been generated by the use of HFNC. Studies suggest that NRBM has the least dispersed aerosols, with a maximum exhaled air distances of <0.1 mts at 10 l/min.[11] Roy et al.[12] stated that NRBM can be used to provide moderate to high FiO2 for moderate duration and with a tight-fitting mask, the aerosol spread is minimum. Studies suggest that high Fio2 for prolonged duration is associated with hyperoxic lung injury that attributes to increased mortality; hence, patients using NRBM for a prolonged period had a higher mortality rate compared to shorter duration of time.[13] This is possibly attributed to the oxygen toxicity as a result of high concentration oxygen therapy reported in a previous study.[14] NRBM should be used wherever possible, especially for preoxygenation before intubation.[10],[14],[15] NRBM + nasal cannula may represent an inexpensive and easily accessible therapeutic substitute for HFNC, particularly when the risk of transmission and costs related with HFNC use is considered.[16] In selected patients, by reducing the work of breathing, these devices might alleviate the need for ventilators and possibly lead to lesser aerosol generation due to the reduction in flow requirements.[17] If a patient is suspected to have hypercapnic respiratory failure due to excessive oxygen therapy, the oxygen therapy must be stepped down to the lowest level required to maintain a saturation range of 88%–92%. This may be achieved using 28% or 24% oxygen from a Venturi mask or 1–2 L/min through nasal cannulae depending on oxygen saturation and subsequent blood gas measurements. Sudden cessation of supplementary oxygen therapy can cause life-threatening rebound hypoxemia with a rapid fall in oxygen saturations below the starting oxygen saturation before the start of supplementary oxygen therapy. One study has found the incidence of hypoventilation to be as high as 31% in a cohort of obese hospitalized patients.[18] Wijesinghe et al.[19] have demonstrated that breathing high FiO2 causes worsening hypercapnia in patients with obesity-associated hypoventilation and hence patients with morbid obesity the target saturation should be usually 88%–92%. Few studies have evaluated the accuracy of SpO2 in critically ill patients.[20] The mean difference between SpO2 and SaO2 was −0.02% and SD of the differences was 2.1%.[20] Subgroup analysis showed that the accuracy of SpO2 appeared to be influenced by the type of oximeter, the presence of hypoxemia and the requirement for vasoactive drugs.[20] A SpO2 above 94% appears necessary to ensure a SaO2 of 90% in OHDC,[20] hence the kind of pulse oximeter we use has a significant effect in estimating the oxygenation levels in critically ill patients. Recent technology changes have significantly improved pulse oximeter performance during motion artifacts thereby improving the accuracy of estimating SpO2 levels.[21] In this study, providing NRBM support at the early phase of the disease in appropriate patients were associated with early positive outcome and decreased mortality compared to patients receiving noninvasive and invasive mechanical ventilation.
| Conclusions | | |
O2 therapy is critical for the successful treatment of hypoxemic COVID19 patients and to decrease mortality. NRBM proved to be utilized as a preferred oxygen supplementation device of choice in acute moderate to severe hypoxemic COVID pneumonia patients during early phases of presentation, thereby preventing them from progressing to NIV/invasive mechanical ventilation. It is an economical oxygen delivery system which can provide maximum Fio2 (up to 90% @ flow rate of 15 L/min). Extremely tachypneic (RR >30/min) respiratory failure patients proved to be the poor candidates for NRBM utilization. NRBM is the most significant and impactful oxygen delivery system in the current pandemic period where limited resources are of major concern.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9]
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