Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X

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Dr Mohan Z Mani

"Thank you very much for having published my article in record time.I would like to compliment you and your entire staff for your promptness, courtesy, and willingness to be customer friendly, which is quite unusual.I was given your reference by a colleague in pathology,and was able to directly phone your editorial office for clarifications.I would particularly like to thank the publication managers and the Assistant Editor who were following up my article. I would also like to thank you for adjusting the money I paid initially into payment for my modified article,and refunding the balance.
I wish all success to your journal and look forward to sending you any suitable similar article in future"

Dr Mohan Z Mani,
Professor & Head,
Department of Dermatolgy,
Believers Church Medical College,
Thiruvalla, Kerala
On Sep 2018

Prof. Somashekhar Nimbalkar

"Over the last few years, we have published our research regularly in Journal of Clinical and Diagnostic Research. Having published in more than 20 high impact journals over the last five years including several high impact ones and reviewing articles for even more journals across my fields of interest, we value our published work in JCDR for their high standards in publishing scientific articles. The ease of submission, the rapid reviews in under a month, the high quality of their reviewers and keen attention to the final process of proofs and publication, ensure that there are no mistakes in the final article. We have been asked clarifications on several occasions and have been happy to provide them and it exemplifies the commitment to quality of the team at JCDR."

Prof. Somashekhar Nimbalkar
Head, Department of Pediatrics, Pramukhswami Medical College, Karamsad
Chairman, Research Group, Charutar Arogya Mandal, Karamsad
National Joint Coordinator - Advanced IAP NNF NRP Program
Ex-Member, Governing Body, National Neonatology Forum, New Delhi
Ex-President - National Neonatology Forum Gujarat State Chapter
Department of Pediatrics, Pramukhswami Medical College, Karamsad, Anand, Gujarat.
On Sep 2018

Dr. Kalyani R

"Journal of Clinical and Diagnostic Research is at present a well-known Indian originated scientific journal which started with a humble beginning. I have been associated with this journal since many years. I appreciate the Editor, Dr. Hemant Jain, for his constant effort in bringing up this journal to the present status right from the scratch. The journal is multidisciplinary. It encourages in publishing the scientific articles from postgraduates and also the beginners who start their career. At the same time the journal also caters for the high quality articles from specialty and super-specialty researchers. Hence it provides a platform for the scientist and researchers to publish. The other aspect of it is, the readers get the information regarding the most recent developments in science which can be used for teaching, research, treating patients and to some extent take preventive measures against certain diseases. The journal is contributing immensely to the society at national and international level."

Dr Kalyani R
Professor and Head
Department of Pathology
Sri Devaraj Urs Medical College
Sri Devaraj Urs Academy of Higher Education and Research , Kolar, Karnataka
On Sep 2018

Dr. Saumya Navit

"As a peer-reviewed journal, the Journal of Clinical and Diagnostic Research provides an opportunity to researchers, scientists and budding professionals to explore the developments in the field of medicine and dentistry and their varied specialities, thus extending our view on biological diversities of living species in relation to medicine.
‘Knowledge is treasure of a wise man.’ The free access of this journal provides an immense scope of learning for the both the old and the young in field of medicine and dentistry as well. The multidisciplinary nature of the journal makes it a better platform to absorb all that is being researched and developed. The publication process is systematic and professional. Online submission, publication and peer reviewing makes it a user-friendly journal.
As an experienced dentist and an academician, I proudly recommend this journal to the dental fraternity as a good quality open access platform for rapid communication of their cutting-edge research progress and discovery.
I wish JCDR a great success and I hope that journal will soar higher with the passing time."

Dr Saumya Navit
Professor and Head
Department of Pediatric Dentistry
Saraswati Dental College
On Sep 2018

Dr. Arunava Biswas

"My sincere attachment with JCDR as an author as well as reviewer is a learning experience . Their systematic approach in publication of article in various categories is really praiseworthy.
Their prompt and timely response to review's query and the manner in which they have set the reviewing process helps in extracting the best possible scientific writings for publication.
It's a honour and pride to be a part of the JCDR team. My very best wishes to JCDR and hope it will sparkle up above the sky as a high indexed journal in near future."

Dr. Arunava Biswas
MD, DM (Clinical Pharmacology)
Assistant Professor
Department of Pharmacology
Calcutta National Medical College & Hospital , Kolkata

Dr. C.S. Ramesh Babu
" Journal of Clinical and Diagnostic Research (JCDR) is a multi-specialty medical and dental journal publishing high quality research articles in almost all branches of medicine. The quality of printing of figures and tables is excellent and comparable to any International journal. An added advantage is nominal publication charges and monthly issue of the journal and more chances of an article being accepted for publication. Moreover being a multi-specialty journal an article concerning a particular specialty has a wider reach of readers of other related specialties also. As an author and reviewer for several years I find this Journal most suitable and highly recommend this Journal."
Best regards,
C.S. Ramesh Babu,
Associate Professor of Anatomy,
Muzaffarnagar Medical College,
On Aug 2018

Dr. Arundhathi. S
"Journal of Clinical and Diagnostic Research (JCDR) is a reputed peer reviewed journal and is constantly involved in publishing high quality research articles related to medicine. Its been a great pleasure to be associated with this esteemed journal as a reviewer and as an author for a couple of years. The editorial board consists of many dedicated and reputed experts as its members and they are doing an appreciable work in guiding budding researchers. JCDR is doing a commendable job in scientific research by promoting excellent quality research & review articles and case reports & series. The reviewers provide appropriate suggestions that improve the quality of articles. I strongly recommend my fraternity to encourage JCDR by contributing their valuable research work in this widely accepted, user friendly journal. I hope my collaboration with JCDR will continue for a long time".

Dr. Arundhathi. S
MBBS, MD (Pathology),
Sanjay Gandhi institute of trauma and orthopedics,
On Aug 2018

Dr. Mamta Gupta,
"It gives me great pleasure to be associated with JCDR, since last 2-3 years. Since then I have authored, co-authored and reviewed about 25 articles in JCDR. I thank JCDR for giving me an opportunity to improve my own skills as an author and a reviewer.
It 's a multispecialty journal, publishing high quality articles. It gives a platform to the authors to publish their research work which can be available for everyone across the globe to read. The best thing about JCDR is that the full articles of all medical specialties are available as pdf/html for reading free of cost or without institutional subscription, which is not there for other journals. For those who have problem in writing manuscript or do statistical work, JCDR comes for their rescue.
The journal has a monthly publication and the articles are published quite fast. In time compared to other journals. The on-line first publication is also a great advantage and facility to review one's own articles before going to print. The response to any query and permission if required, is quite fast; this is quite commendable. I have a very good experience about seeking quick permission for quoting a photograph (Fig.) from a JCDR article for my chapter authored in an E book. I never thought it would be so easy. No hassles.
Reviewing articles is no less a pain staking process and requires in depth perception, knowledge about the topic for review. It requires time and concentration, yet I enjoy doing it. The JCDR website especially for the reviewers is quite user friendly. My suggestions for improving the journal is, more strict review process, so that only high quality articles are published. I find a a good number of articles in Obst. Gynae, hence, a new journal for this specialty titled JCDR-OG can be started. May be a bimonthly or quarterly publication to begin with. Only selected articles should find a place in it.
An yearly reward for the best article authored can also incentivize the authors. Though the process of finding the best article will be not be very easy. I do not know how reviewing process can be improved. If an article is being reviewed by two reviewers, then opinion of one can be communicated to the other or the final opinion of the editor can be communicated to the reviewer if requested for. This will help one’s reviewing skills.
My best wishes to Dr. Hemant Jain and all the editorial staff of JCDR for their untiring efforts to bring out this journal. I strongly recommend medical fraternity to publish their valuable research work in this esteemed journal, JCDR".

Dr. Mamta Gupta
(Ex HOD Obs &Gynae, Hindu Rao Hospital and associated NDMC Medical College, Delhi)
Aug 2018

Dr. Rajendra Kumar Ghritlaharey

"I wish to thank Dr. Hemant Jain, Editor-in-Chief Journal of Clinical and Diagnostic Research (JCDR), for asking me to write up few words.
Writing is the representation of language in a textual medium i e; into the words and sentences on paper. Quality medical manuscript writing in particular, demands not only a high-quality research, but also requires accurate and concise communication of findings and conclusions, with adherence to particular journal guidelines. In medical field whether working in teaching, private, or in corporate institution, everyone wants to excel in his / her own field and get recognised by making manuscripts publication.

Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."

Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
On May 11,2011

Dr. Shankar P.R.

"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."

Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
On April 2011

Dear team JCDR, I would like to thank you for the very professional and polite service provided by everyone at JCDR. While i have been in the field of writing and editing for sometime, this has been my first attempt in publishing a scientific paper.Thank you for hand-holding me through the process.

Dr. Anuradha
On Jan 2020

Important Notice

Original article / research
Year : 2021 | Month : August | Volume : 15 | Issue : 8 | Page : LC01 - LC04 Full Version

Blood Gas Analysis among COVID-19 Patients: A Single Centre Retrospective Observational Study

Published: August 1, 2021 | DOI:
Soumitra Mondal, Tarun Kumar Das, Saikat Bhattacharya, Shibasish Banerjee, Debopam Hazra

1. Demonstrator, Department of Community Medicine, Medical College Kolkata, Kolkata, West Bengal, India. 2. Medical Officer, Department of Emergency, Tamluk District Hospital, Tamluk, West Bengal, India. 3. Assistant Professor, Department of Community Medicine, Medical College Kolkata, Kolkata, West Bengal, India. 4. Assistant Professor, Department of Community Medicine, Medical College Kolkata, Kolkata, West Bengal, India. 5. Medical Superintendent, Department of Medical Administration, Boroma Covid Hospital, Panskura, West Bengal, India.

Correspondence Address :
Dr. Shibasish Banerjee,
40 (Old 21), Iswar Gupta Road, Namita Bas Appartment, Flat 2b, First Floor, Kolkata-700028, West Bengal, India.


Introduction: The dominant respiratory feature of Coronavirus Disease 2019 (COVID-19) is arterial hypoxaemia, greatly exceeding abnormalities in pulmonary mechanics. Arterial Blood Gas (ABG) analysis helps to find out respiratory, metabolic acidosis and alkalosis.

Aim: To evaluate the blood gas levels among critically ill COVID-19 positive patients admitted in Intensive Care Unit (ICU).

Materials and Methods: A retrospective, observational study was conducted in East Midnapore district of West Bengal, India from July 2020 to February 2021. Data of ABG analysis {pH, PaO2 (partial pressure of oxygen in arterial blood), PaCO2 (partial pressure of carbon dioxide in arterial blood) and bicarbonate (HCO3)} in 314 adult COVID-19 positive cases, were obtained from ICU records. All critically ill COVID-19 patients those who were admitted in ICU with more than 15 years of age were included in this study. Data were analysed and Pearson correlation test was applied for statistical significance.

Results: Among the study subjects, 234 (74.5%) were males. Most affected age group was 51-60 years among males and above 60 years among females. Most common ABG finding was high pH indicating alkalosis, found among 183 (58.3%) patients. Acidosis was rare and seen in only 19 (6.0%) patients. A total of 174 (55.4%) patients developed respiratory alkalosis with low PaCO2. Hypoxaemia was found in 144 (45.9%) patients. High HCO3, indicating metabolic alkalosis, was seen in 144 (45.9%) patients. Statistically significant correlation was found between PaCO2 and pH (pearson correlation coefficient (r)=-0.153, p=0.007) and PaCO2 and HCO3 standard (r=0.185, p=0.001).

Conclusion: ABG should be done in all COVID-19 patients during admission. A regular interval monitoring of ABG can help in early identification of respiratory damage, silent hypoxia and cytokine storm and with early detection many lives can be saved with early initiation of management.


Alkalosis, Bicarbonate, Hypoxaemia, Metabolic acidosis

Coronaviruses are a family of viruses that are known to cause both respiratory and intestinal diseases in various animal species and in humans (1). These viruses tend to target the upper respiratory tract, which in extreme cases can progress to severe pneumonia. While most COVID-19 cases have been identified as mild, extreme diagnoses have led to respiratory failure, septic shock, and/or multiple organ dysfunction (2). As this infectious disease continues to spread, further clinical and epidemiological characteristics must be elucidated to improve our understanding of the true extent of the virus, in order to improve diagnostic and treatment capabilities and reduce its overall impact on morbidity and mortality.

Arterial hypoxemia is key respiratory feature among COVID-19 patients. Patients’ oxygenation is evaluated initially using a pulse oximeter. Pulse oximetry estimates SaO2 (oxygen saturation as measured by blood analysis) by measuring changes in light absorption by oxyhaemoglobin in arterial blood (3). Saturation (SpO2) thus estimated by pulse oximetry can differ from true SaO2 (measured with a CO-oximeter) by as much as ±4% (4).

Hypocapnic hypoxia, also termed as silent hypoxia, has multi-factorial causation in case of COVID-19. Fever, prominent with COVID-19, causes the oxygen dissociation curve to shift to the right; thus any given PaO2 will be associated with a lower SaO2. It is also seen that Angiotensin-Converting Enzyme 2 (ACE 2), the cell receptor of Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2), is expressed in the carotid body, the site at which chemoreceptors sense oxygen (5). Carotid bodies are responsible for respiratory drive, respond only to PaO2 and not SaO2. Due to this rightwards shift, substantial desaturation of oxygen occurs without change in carotid body stimulation which is responsible for occurrence of silent hypoxemia (6). Silent hypoxemia, with increased thrombogenesis leading to the development of thrombi within the pulmonary vasculature, has been noted in patients with COVID-19 (7). Thrombi within the pulmonary vasculature can cause severe hypoxemia and dyspnoea is related to pulmonary vascular obstruction and its consequences. Dyspnoea can also arise from the release of histamine or stimulation of juxtacapillary receptors within the pulmonary vasculature leading to serious complications (8).

Different pathological mechanism like fever, inflammation involving multiple organs, thrombogenesis, respiratory tract infection (both upper and lower) and carotid body suppression are possible in different stages of COVID-19 disease. Depending on the underlying mechanism, predominant blood acid base balance can shift either towards acidosis or alkalosis. Recently some studies were conducted on acid base balance and ABG of COVID-19 patients in different countries like China, Italy and South Africa (9),(10),(11),(12). These studies concluded that alkalosis is more prevalent among the ICU admitted COVID-19 patients which is unusual as acidosis is more common in patients admitted to ICU (for other diseases). Hence, the present study was conducted among the patients suffering from severe form of COVID-19 disease with the aim of finding out pH, PaO2, PaCO2 and HCO3 (bicarbonate) levels as per ABG analysis, which are suggestive of respiratory and metabolic acidosis/alkalosis.

Material and Methods

A retrospective observational was conducted at a designated COVID-19 Hospital in East Midnapore district of West Bengal, India. Data of 314 critically ill COVID-19 patients admitted in ICU from 1st July 2020 to 1st February 2021 were analysed. Data of seven patients were excluded who succumbed before their ABG analysis could be done. Analysis of data was conducted in March 2021. The study was approved by the Institutional Ethics Committee (MC/KOL/IEC/NON-SPON/1051/02/2021 dated 23.02.2021). Permission from the medical superintendent of the institute was also obtained for accessing records.

Inclusion criteria: All patients of 15 years of age and above who were admitted due to severe form of COVID-19 in ICU within the study period were included.

Exclusion criteria: Those patients who succumbed before ABG analysis could be done were excluded.

Sample size was calculated using complete enumeration method. Data of ABG were collected from ICU records register. For each patient, only the first ABG data was collected. As per the protocol, ABG was conducted among all patients immediately after ICU admission. In case of repeat ABG reports the first one collected immediately after ICU admission was considered for analysis. Apart from ABG, SpO2 was measured using pulse oximeter at the time of ICU admission.

COVID-19 was diagnosed on the basis of clinical features like flu-like symptoms, fever, tachypnoea, hypoxemia and SARS-COV-2 detection through Real-time PCR (12),(13). Patients admitted in ICU and Fraction of inspired Oxygen (FiO2) atleast 60% or more and/or those who were under mechanical ventilation were considered as critically ill patients (14).

For operational purpose, pH values of 7.35-7.45 was taken as normal. As for PaO2, normal value was taken as 75-100 mmHg, for PaCO2-35-45 mmHg and for standard bicarbonate value (after adjusting actual bicarbonate value automatically in ABG) 22-26 mmol/L was taken as normal (15).

Statistical Analysis

Collected data were compiled in MS excel and analysed using Statistical Package for Social Sciences (SPSS) version 20. Frequency of different variables was calculated and presented as percentage. Variables like pH, PaCO2, PaO2, standard HCO3 was recoded as low, normal and high. Pearson correlation was applied for statistical significance and p<0.05 was considered as significant.


Data of total 314 critically ill COVID-19 patients admitted in ICU were analysed. There were 234 (74.5%) males. Most affected age group was 51-60 years in male followed by 41-50 years. Among females most affected age group was above 60 years, followed by 51-60 years (Table/Fig 1).

High pH (alkalosis) was found in 183 (58.3%) patients. Only 19 (6.1%) patients’ pH was <7.35, indicating that acidosis was rare. Total 174 (55.4%) patients developed respiratory alkalosis (low PaCO2) in ABG. Low PaO2 (hypoxaemia) was found in 144 (45.9%) patients. As per pulse oximeter, 146 (46%) patients had hypoxaemia as indicated by SpO2 less than 95 percent. Surprisingly, 103 (32.8%) patients had high PaO2. High HCO3 was seen in 144 (45.9%) patients (Table/Fig 2).

Pearson correlation test was done and statistically significant correlation was found with PaCO2 and pH (pearson correlation coefficient (r)=-0.153, p=0.007) and PaCO2 and HCO3 standard (r=0.185, p=0.001) (Table/Fig 3), (Table/Fig 4). A positive correlation was found between PaO2 and PaCO2 indicating coexistence of hypocapnia and hypoxia (r=0.008, p>0.05).


The study was aimed at finding the blood picture, suggestive of respiratory and/or metabolic acidosis or alkalosis, among severely ill ICU admitted COVID-19 patients. A clear and significant pattern, helps in understanding the underlying pathophysiology in the study population. Results indicate alkalosis in about 58% of the subjects. Low PaCO2 among 56% study subjects indicated that mostly respiratory alkalosis occurs in severe COVID-19. Pearson correlation between pH and PaCO2 showed negative correlation which is expected in case of respiratory alkalosis. Many hypotheses were postulated for possible reasons of respiratory alkalosis in COVID-19 patients instead of acidosis. One hypothesis says that by suppressing response of carotid body towards lack of oxygen COVID-19 prevents hyperventilation and subsequently CO2 accumulation in blood. ACE2 receptors present in carotid body are probably involved in this process, as the COVID-19 causing virus has shown affinity towards ACE2 receptors (6).

It is found that the air sacs in the lungs of COVID-19 patients are not filled with fluid or pus but instead here virus causes the water sacs to collapse, thereby causing hypoxia in the patients. On the other hand the normal lungs’ ability to expel carbon dioxide is not hampered in this process. As there is no accumulation of CO2, patients do not feel Shortness of Breath (SOB) (16).

Respiratory alkalosis with hypoxaemia was most common finding in this study which was similar to the findings of a study conducted in Italy (17). A positive correlation between PaO2 and PaCO2 suggests presence of hypocapnic hypoxia which is responsible for the so called ‘silent’ or ‘happy’ hypoxia. Hypocapnic hypoxia is not associated with air hunger; rather, a feeling of calm and well-being may arise which makes the determination of severity of disease difficult resulting in delay in hospitalisation. As per an aviation medicine (18) study, decompression to high altitude causes severe hypoxaemia, which triggers the carotid chemoreceptors and sparks a brisk respiratory response with ensuing hypocapnia. Triggering carotid chemoreceptors may be the reason of hypocapnia in COVID-19 disease also. It is interesting to note that all patients were suffering from severe form of disease and many of them presented with SOB leading to air hunger and hypercapnia. In spite of that, overall weak positive correlation between PaO2 and PaCO2 suggests that there is possibility of having positive correlation between these two if the ABG is conducted before initiation of SOB.

Though less in number, some COVID-19 patients also presented with respiratory acidosis which is expected in case of air hunger. Another study, conducted in Bolivia, found that respiratory acidosis with hypoxaemia leads to pneumolysis and death (19).

As compensatory mechanism to respiratory alkalosis it is expected that metabolic acidosis would develop. But in this study, metabolic alkalosis was found among 46% patients. Hyperpyrexia due to cytokine storm could be a cause of metabolic alkalosis. Similar findings were also seen among intubated COVID-19 patient with obstructive lung disease and hyperpyrexia (15). Many COVID-19 patients also presented with vomiting, diarrhoea and dehydration which may lead to metabolic alkalosis due to deficiency of potassium. Operationally, prior use of corticosteroid at home or any other hospital setting can also lead to metabolic alkalosis by triggering mineralocorticoid system. In this study approximately 16% patient developed metabolic acidosis. Multiorgan failure, especially acute kidney injury triggered by cytokine storm and microvascular thrombosis indicated by elevated D-dimer and low platelet count, was the main cause of metabolic acidosis in COVID-19 patient (20). Though metabolic alkalosis was predominant finding but significant positive correlation (r=0.185) between PaCO2 and standard bicarbonate indicates that patients with hypocapnia are also having low bicarbonate level leading to metabolic acidosis which may be compensatory in nature.


The study was conducted among seriously ill ICU admitted COVID-19 patients. It would have been better if ABG analysis of mild and moderately ill patients were also included. The relationship of ABG with outcome of the patients in terms of survival and the change of pattern of ABG report over time with disease progression were not included in the present study which needs further research. One important limitation was the presence of operational causes of respiratory alkalosis found in the study. Though all the ABG reports were taken at the time of admission in the ICU but many of the patients were in home oxygen support before admission or even on BiPAP (Bilevel Positive Airway Pressure) support in some other nursing homes from where they were referred out. These may have caused over correction of natural respiratory acidosis leading to the picture found out in the present study.


Acid base disorder is very common in COVID-19 patients. Though respiratory alkalosis was predominant but respiratory acidosis with mixed metabolic acidosis and alkalosis was also seen in the study. A significant correlation between pH and PaCO2; and PaCO2 and HCO3 were found in the study. A regular interval monitoring of ABG can help in early identification of respiratory damage, silent hypoxia and cytokine storm. With early detection many lives can be saved with early initiation of management.


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DOI and Others


Date of Submission: Apr 09, 2021
Date of Peer Review: May 13, 2021
Date of Acceptance: Jun 16, 2021
Date of Publishing: Aug 01, 2021

• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? NA
• For any images presented appropriate consent has been obtained from the subjects. NA

• Plagiarism X-checker: Apr 12, 2021
• Manual Googling: Jun 02, 2021
• iThenticate Software: Jul 08, 2021 (15%)

ETYMOLOGY: Author Origin

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