India’s second wave in April-May 2021 produced one of the largest concentrated demands for acute supplemental oxygen in modern medical history. At the peak of the surge, tens of thousands of patients were on supplemental oxygen simultaneously; the oxygen-supply logistics crisis of those weeks reshaped the Indian home-oxygen market and introduced millions of families to oxygen concentrators for the first time. Five years on, a much smaller but clinically important cohort remains — patients who never fully recovered their baseline respiratory function, whose SpO₂ still falls below 90% on exertion or at rest, and for whom the acute-phase supplemental oxygen has become, effectively, long-term oxygen therapy. This article reviews what the 2024–26 literature tells us about the natural history of post-COVID persistent hypoxaemia, when it is reversible, when it has transitioned to fibrotic lung disease, and how it should be managed in Indian practice.
The audience: pulmonologists seeing persistent post-COVID referrals, primary-care physicians managing chronic oxygen prescriptions that were initiated during 2021–2022 and never weaned, patients living with persistent dyspnoea, and health-system planners thinking about the longer-term respiratory legacy of the pandemic.
The acute-to-chronic transition
Acute COVID-19 pneumonia produces hypoxaemia through a combination of V/Q mismatch, microthrombotic capillary obstruction, diffuse alveolar damage, and — in severe cases — the formation of hyaline membranes and subsequent organising pneumonia. For most patients, these changes resolve: a six-week follow-up high-resolution CT (HRCT) shows residual ground-glass opacities that substantially clear over 3–6 months, and pulmonary function returns to near-baseline by 12 months.
For a minority, resolution is incomplete. Post-COVID persistent hypoxaemia — defined operationally as SpO₂ below the pre-morbid baseline persisting more than three months after acute infection — has been reported in a range of Indian and international cohorts.
Meta-analyses of post-acute COVID sequelae published in 2024 and 2025 provide the most recent synthesis. Synthesising across cohorts with methodological heterogeneity:
- At 3 months post-discharge from hospitalised COVID pneumonia, 15–40% of patients have some degree of persistent dyspnoea; 8–20% have documented exertional desaturation on 6-minute walk testing.
- At 6 months, the proportion with persistent oxygen requirement has typically halved.
- At 12 months, 2–8% of hospitalised-pneumonia survivors have a persistent oxygen requirement.
- At 24 months and beyond, a residual 1–3% of the original hospitalised cohort has a persistent oxygen requirement, and most of this group has developed radiological features of post-COVID interstitial lung disease.
The numbers are estimates with wide confidence intervals; methodology (how persistent dyspnoea and hypoxaemia are defined, how completely patients are followed, whether the cohort is from the Wuhan, Alpha, Delta, or Omicron era) varies enormously. The Delta-era cohorts, relevant to the Indian 2021 surge, had the highest rates of severe acute hypoxaemia and the highest rates of persistent radiological abnormality at follow-up.
The typical weaning timeline
For a patient discharged from a 2021 Delta-era hospitalisation on home supplemental oxygen, the clinical trajectory that applied to most:
Weeks 0–4 post-discharge. Supplemental oxygen continues at the flow prescribed at discharge, typically 1–3 LPM for rest and 2–5 LPM for exertion. SpO₂ on oxygen, exertional tolerance, and respiratory symptoms are the tracked parameters. Physiotherapy and early mobilisation begin.
Weeks 4–12. Weaning trial. The patient is encouraged to spend increasing periods off oxygen during daytime rest, provided SpO₂ remains ≥93%. If the patient tolerates room air at rest, exertional testing (a corridor walk or formal 6MWT) establishes whether exertional supplementation is still needed. For most patients in this phase, the home oxygen prescription is dialled back from continuous to activity-only, then to PRN, and then discontinued.
Months 3–6. Most patients in this window either have stopped needing home oxygen or are trending toward discontinuation. Persistent requirement at 6 months warrants a more formal reassessment — HRCT, pulmonary function tests (spirometry, DLCO, lung volumes), and ABG if hypoxaemia is suspected to involve CO₂ retention.
Months 6–12. The cohort narrows. Patients still requiring oxygen at 6 months have roughly a 50% chance of weaning by 12 months, based on Indian and international cohort data. The other 50% stabilise at a chronic level of hypoxaemia that then becomes a chronic oxygen prescription.
Beyond 12 months. By this point, the clinical picture is typically stable. The question shifts from “will this resolve?” to “what is the underlying condition, and how should it be managed chronically?” In most cases, the answer is post-COVID ILD or post-COVID fibrosis; occasionally it is an unmasked pre-existing lung disease or a superimposed condition (pulmonary embolism, pulmonary hypertension).
When long-COVID becomes ILD territory
The transition from “persistent post-COVID hypoxaemia” to “post-COVID ILD” is radiological and physiological, not chronological. A patient at 9 months post-infection with stable exertional hypoxaemia, ground-glass opacities and traction bronchiectasis on HRCT, and reduced DLCO is in ILD territory whether or not the label is formally applied. The management shifts accordingly.
HRCT features that identify post-COVID ILD:
- Reticular opacities with traction bronchiectasis
- Subpleural fibrotic bands, particularly in the posterior lower lobes
- Ground-glass opacities that do not resolve over 6+ months
- Honeycombing (late and uncommon, but when present indicates established fibrosis)
Pulmonary function features:
- Restrictive physiology (reduced TLC, reduced FVC, preserved FEV1/FVC ratio)
- Reduced DLCO (often the most sensitive marker)
- Exertional desaturation on 6MWT
If post-COVID ILD is established, the oxygen prescribing principles shift to the ILD framework described in oxygen therapy for ILD patients. Higher flow rates for exertional correction become relevant; ambulatory oxygen becomes a specific indication; flow ceiling and equipment selection follow the ILD pattern.
A clinical question that arose in 2022–2023 — whether post-COVID fibrosis responds to antifibrotic therapy (nintedanib, pirfenidone) — has produced mixed early evidence. Trials including TRAIL-1 and others suggest a modest effect in some subgroups but no broad-based benefit that would change first-line management. Most Indian pulmonologists reserve antifibrotic therapy for radiologically progressive post-COVID fibrosis, rather than routinely treating early post-COVID interstitial changes.
The Indian cohort experience
Indian post-COVID cohorts reported from 2022 onward provide the most directly applicable data. Several characteristics distinguish the Indian experience:
Younger age distribution. India’s 2021 Delta surge affected a younger population than Western waves; the median age of severe COVID-19 hospitalisation in India was approximately 48, compared to 65+ in many Western cohorts. Younger patients generally recover more fully; but the absolute numbers of affected patients, given India’s population, remain substantial.
Under-vaccination at surge time. The Indian Delta surge predated widespread vaccination. Most patients admitted with severe COVID pneumonia in 2021 had received either no vaccine or one dose. This contrasts with later Omicron cohorts where vaccination status was more favourable; Omicron-era hospitalisation rates in India were lower and long-COVID rates appear correspondingly lower.
Diabetes prevalence. Diabetic status was strongly associated with severe acute COVID and with persistent post-COVID respiratory sequelae in Indian cohorts. India’s very high adult diabetes prevalence (ICMR-INDIAB estimates ~11–12% nationally, higher in urban centres) is a proximate cause of the elevated long-COVID burden.
Secondary infections. Indian hospitalised COVID cohorts had high rates of superinfection — bacterial pneumonia, mucormycosis (post-steroid), aspergillosis, and reactivation tuberculosis. Each of these complicates the post-COVID respiratory picture; persistent hypoxaemia in a Delta-era patient requires exclusion of superimposed bronchiectasis from bacterial infection, residual aspergillosis, or reactivated TB.
Long-term follow-up cohort data from Indian centres — AIIMS Delhi, PGIMER Chandigarh, CMC Vellore, and several private tertiary centres — published through 2024 and 2025 suggest:
- Approximately 5–10% of hospitalised Delta-wave survivors had persistent oxygen requirement at 12 months.
- By 24–30 months, most of this group had stabilised at a chronic requirement or weaned further.
- The persistent-requirement cohort was disproportionately older, more comorbid (diabetes, cardiovascular disease), and had more severe acute disease (ICU admission, mechanical ventilation).
Across India, the cumulative number of patients with persistent post-COVID oxygen requirement at five years is plausibly in the low six figures — not a routine clinical encounter at a typical pulmonology clinic, but not rare either.
Reimbursement and access reality, five years on
At the peak of the 2021 surge, oxygen concentrators were in acute shortage; government relief programmes, state-level procurements, NGO distributions, and emergency imports flooded the market. Many concentrators from that period are now out of warranty, variably maintained, and in homes where the patient has long since weaned but the machine sits unused. A smaller subset of machines is in homes of the persistent-requirement cohort, providing ongoing therapy.
Reimbursement five years on is less emergency-driven and more aligned with chronic LTOT reimbursement pathways:
- CGHS beneficiaries with documented post-COVID ILD or persistent hypoxaemia are reimbursed under standard LTOT documentation — ABG or SpO₂ evidence, pulmonologist prescription, specified flow and duration. Many CGHS oxygen concentrators were procured during 2021; the replacement cycle is underway.
- ECHS similar, varies by hospital.
- Private insurance largely does not cover durable home oxygen equipment.
- PMJAY does not cover home oxygen as a scheme benefit. A subset of state-level schemes provide support.
- NGO and charitable distribution of concentrators that were donated during 2021 continues patchily; the original supply lines and reconditioning programmes still operate in some regions.
The concentrator market itself is substantially changed from pre-2021. Indian production (Bharat Electronics, BPL, Oxymed, Inogen-partner companies) scaled dramatically, and the price floor for a functional 5 LPM unit dropped. The oxygen concentrator reviews on this site include many models that entered the Indian market during or immediately after the surge.
Clinical management principles for the persistent cohort
A patient who has been on home oxygen since 2021–2022 and continues to require it in 2026 should be managed with a few specific considerations:
Establish the current diagnosis. Most of these patients have post-COVID ILD by now. An HRCT and pulmonary function tests (if not recent) establish the current disease state and distinguish stable fibrosis from ongoing inflammatory change.
Re-titrate the oxygen prescription. A prescription written at discharge in 2021 may be excessive or inadequate now. Resting and exertional SpO₂ on room air and on current oxygen should be documented; flow adjusted accordingly.
Consider specific therapy. Antifibrotic therapy for clearly progressive post-COVID fibrosis; pulmonary rehabilitation for any patient with persistent exertional limitation; vaccination (COVID boosters per current schedule, influenza, pneumococcal) universally.
Monitor for complications. Persistent hypoxaemia produces secondary pulmonary hypertension over time; an echocardiogram every 12–24 months is reasonable. Patients with chronic oxygen use who develop new symptoms (worsening dyspnoea, oedema, syncope) need re-evaluation.
Weaning is still possible. Even five years on, a subset of patients weans with pulmonary rehabilitation, optimised medical therapy, and time. A trial of stepped weaning every 6–12 months is reasonable in stable patients.
Psychological impact. Persistent oxygen requirement five years after an acute illness that many peers recovered from produces a specific psychological burden. Formal screening for depression and anxiety, and referral where indicated, is a legitimate part of chronic oxygen care.
Consult your pulmonologist if you are still on home oxygen from a 2021 COVID admission and have not been recently reassessed — both to confirm that the current prescription is still appropriate and to evaluate whether any step-down is feasible.
Closing: what the pandemic left us
The Indian home-oxygen market, the national consciousness about respiratory distress, and the clinical literature on post-COVID respiratory sequelae are all permanently reshaped by the 2021 experience. Most patients who needed oxygen during that surge recovered. A smaller number did not, and that smaller number represents a chronic respiratory-disease population that will remain identifiable for decades. Their management is not fundamentally different from other ILD or chronic hypoxaemia populations, but the origin story — a specific viral insult affecting a specific cohort, with documented acute-phase care — allows more precise longitudinal tracking than most chronic lung disease cohorts.
For the prescribing physician, the key position is that post-COVID hypoxaemia at five years is not “long COVID” as a vague syndromic label; it is a structural lung disease with specific radiological features, a measurable physiology, and a management plan that follows established ILD principles. Treating it as such — rather than as an indefinite acute sequela — serves patients better.
Primary references that inform clinical practice in this area: Post-acute COVID meta-analyses 2024–2025 (Lancet Respiratory Medicine, Chest, JAMA Internal Medicine); Indian cohort studies from AIIMS/PGIMER/CMC published 2022–2025; ATS/ERS 2020 home oxygen guidance; ICMR guidelines on post-COVID care; ongoing antifibrotic trial data 2023–25.