Burden and Characteristics of Severe Chronic Hypoxemia in a Real-World Cohort of Subjects with COPD.

Background: Chronic respiratory failure may occur as a consequence of chronic obstructive pulmonary disease (COPD) and is associated with significant morbidity and mortality. Hypoxemia is determined by underlying disease characteristics and comorbidities. Severe hypoxemia is typically only found in subjects with severe airflow obstruction (FEV ₁ <50% predicted). However, how hypoxemia relates to disease characteristics is not fully understood.
Methods: In the French Initiatives BPCO real-life cohort, arterial blood gases were routinely collected in most patients. Relationships between severe hypoxemia, defined by a Pa0 ₂ <60 mmHg (8 kPa) and clinical/lung function features, comorbidities and mortality were assessed. In subjects with severe hypoxemia, clinical characteristics and comorbidities were compared between those with non-severe versus severe airflow limitation. Classification and regression trees (CART) were used to define clinically relevant subgroups (phenotypes).
Results: Arterial blood gases were available from 887 subjects, of which 146 (16%) exhibited severe hypoxemia. Compared to subjects with a PaO2≥60 mmHg, the severe hypoxemia group exhibited higher mMRC dyspnea score, lower FEV ₁ , higher RV and RV/TLC, more impaired quality of life, lower 6-minute walking distance, less frequent history of asthma, more frequent diabetes and higher 3-year mortality rate (14% versus 8%, p=0.026). Compared to subjects with Pa0 ₂ <60 mmHg and FEV ₁ <50% (n=115, 13%), those with severe hypoxemia but FEV1≥50% predicted (n=31) were older, had higher BMI, less hyperinflation, better quality of life and a higher rate of diabetes (29% versus 13%, p=0.02). Severe hypoxemia was better related to CART-defined phenotypes than to GOLD ABCD classification.
Conclusion: In this cohort of stable COPD subjects, severe hypoxemia was associated with worse prognosis and more severe symptoms, airflow limitation and hyperinflation. Compared to subjects with severe hypoxemia and severe airflow limitation, subjects with severe hypoxemia despite non-severe airflow limitation were older, had higher BMI and more diagnosed diabetes.
Trial Registration: 04-479.
Competing Interests: MZ reports grants and personal fees from Boehringer Ingelheim, grants and personal fees from Novartis, personal fees from Chiesi, personal fees from Astra Zeneca and personal fees from GSK outside the submitted work. PRB reports personal fees from Aptalis, personal fees from Astra-Zeneca, grants and personal fees from Boehringer Ingelheim, personal fees from Chiesi, personal fees from GSK, personal fees from Novartis, personal fees from Pfizer, personal fees from Vertex, personal fees from Zambon, personal fees from Insmed, outside the submitted work. ICF reports grants and personal fees from Boehringer Ingelheim, grants and personal fees from Novartis, and GSK outside the submitted work. GBR reports grants and personal fees from Boehringer Ingelheim, grants and personal fees from Novartis, grants and personal fees from Astra Zeneca, personal fees and non-financial support from Chiesi, outside the submitted work. PNM reports grants and personal fees from Boehringer Ingelheim, grants and personal fees from NOVARTIS, personal fees and non-financial support from Chiesi, outside the submitted work. PS reports grants and personal fees from Boehringer Ingelheim outside the submitted work. GD reports personal fees from Novartis, personal fees and grants from Astra Zeneca, personal fees from BTG/PneumRx, personal fees from Chiesi, personal fees from Boehringer Ingelheim, personal fees from GSK, outside the submitted work. TP reports personal fees from Boehringer Ingelheim, personal fees from Novartis, personal fees from GSK, personal fees from Chiesi, personal fees from Pierre Fabre, outside the submitted work. OLR reports grants and personal fees personal fees and non-financial support from Astra Zeneca, Boehringer Ingelheim, Chiesi, Lilly and Novartis; non-financial support from Glaxo Smith Kline, Correvio, Mayoli, Mylan, MSD, PulmonX, Zambon, Novartis, MundiPharma, Pfizer, Teva, Santelys Association, Vertex and Vitalaire, all outside the submitted work. GJ reports personal fees from Boehringer Ingelheim, personal fees from GSK, personal fees from Novartis, personal fees from Menarini, personal fees from Astra Zeneca, personal fees from Chiesi, outside the submitted work. PC reports personal fees from Boehringer Ingelheim, personal fees from GSK, personal fees and grants from ALK, personal fees and grants from Almirall, personal fees and grants from Boehringer-Ingelheim, personal fees from Novartis, personal fees from Teva, personal fees from Astra Zeneca, grants and personal fees from Chiesi, personal fees from Sanofi, personal fees and non-financial support from SNCF, personal fees from GlaxoSmithKline, grants and personal fees from Sanofi-Aventis, grants from Amu, outside the submitted work. JLP reports grants from iBPCO association, during the conduct of the study. DC has nothing to disclose. NR reports grants and personal fees from Boehringer Ingelheim, grants and personal fees from Novartis, grant and personal fees from Pfizer, grants and personal fees from GSK, personal fees from AstraZeneca, personal fees from Chiesi, personal fees from Sanofi, personal fees from Zambon, personal fees and grants from Boehringer Ingelheim, outside the submitted work.
(© 2021 Zysman et al.)