A 50-year-old woman with severe resting hypoxia not amendable to high-flow oxygen supplementation

Abstract

Introduction: Pulse oximetry is a widely used non-invasive method to measure arterial oxygen saturation (SpO2). However, haemoglobinopathies, including rare low-oxygen-affinity variants such as haemoglobin (Hb) Lansing can result in falsely low SpO2 readings due to alterations in the Hb oxygen dissociation curve and spectral properties. Recognising these conditions is crucial to avoid misdiagnosis and unnecessary interventions. Case description: A 50-year-old female with a history of chronic obstructive pulmonary disease (COPD), hypertension and compensated cirrhosis presented for pre-operative evaluation. Persistent hypoxia (SpO2 84%), unresponsive to oxygen supplementation, was noted during routine assessment. Diagnostic investigations excluded pulmonary or cardiac shunts, hepatopulmonary syndrome and common causes of methaemoglobinaemia or carboxyhaemoglobinemia. Arterial blood gas analysis using a CO-oximeter revealed a true oxygen saturation of 90%, highlighting a discrepancy with pulse oximetry. Hb electrophoresis demonstrated an abnormal haemoglobin fraction, and subsequent genetic testing identified a heterozygous mutation (HBA1: c.264C>G), confirming Hb Lansing. The patient was asymptomatic apart from mild exertional dyspnoea attributed to underlying COPD and safely underwent planned surgery. Discussion: Hb Lansing is a rare haemoglobinopathy characterised by low oxygen affinity and high p50, leading to falsely low SpO2 readings and minimal response to supplemental oxygen. Diagnosis relies on CO-oximetry, Hb electrophoresis and genetic analysis. No specific treatment is required for low-affinity haemoglobinopathies, which generally have a benign clinical course. Conclusion: Haemoglobinopathies should be considered in the differential diagnosis of unexplained hypoxia. Utilisation of targeted diagnostic tools enables clinicians to ensure accurate diagnosis and appropriate management.

Keywords

• hypoxia
• haemoglobinopathy
• co-oximetry
• dissociation curve
• blood gases