Background: Lately, there has been many discussions regarding happy / silent hypoxia, whereas the patient does not sense or show symptoms of breathlessness yet the patient has been experiencing hypoxia due to Covid-19 infection. This has caused death to many Covid-19 patients without comorbidities. The most common therapy that is given to COVID-19 patients who experience worsened breathing is to use a mechanical ventilator. However, this therapy has not provided satisfactory result while Hyperbaric Oxygen Therapy (HBOT) has been used to treat various disease that lead to hypoxia, including CO poisoning and chronic anemia. Objective: to explore the possible pathophysiology underlying happy/silent hypoxia in COVID-19 patients, its consequences to oxygen debt and how HBOT is a better treatment compared to mechanical ventilation. Method: This study uses the literature review method using electronic database in the form Pubmed, SCOPUS, Science Direct, Open Access Library (OALIB), Research gate and Google Scholar with restrictions on the keywords of HBOT, Happy hypoxia and COVID-19. Result: Reports from multiple hyperbaric centres in China and the USA showed that patients receiving HBOT treatment as adjuvant therapy can prevent them receiving mechanical ventilation and help overcome the respiratory failure. The proposed mechanism underlying this effect is due to its noninvasive, anti-inflammatory properties and the ability to increase alveolar-arterial oxygen partial pressure (PA-a)O2. Although this therapy has only been given to a small number of COVID-19 patients, the results obtained are that most of these patients experience rapid and permanent improvement without any serious side effect that can worsen the condition. Conclusion: Reports from various Hyperbaric Centres in China and the USA show promising results in using HBOT to overcome the respiratory failure in COVID-19 due to its various properties and with ongoing RCTs, it is hoped that it will give satisfactory results so that it can help overcome hypoxia in COVID-19 patients.