Supplemental oxygen therapy in bleomycin-induced pulmonary toxicity

Dear Editor,

I read with interest the case report “Reversible Bleomycin Toxicity”.¹ The authors have mentioned high-dose oxygen exposure as one of the risk factors for pulmonary toxicity. This is an important aspect of Bleomycin-induced pulmonary toxicity, as supplemental oxygen therapy is considered to be a synergistic toxin with Bleomycin, particularly in the setting of general anaesthesia and hyperbaric oxygen therapy (HBOT). The dosage of oxygen which can result in toxicity has not been quantified. Even a modest increase in fraction of inspired oxygen (FiO₂) to 0.32 or 0.45, intra-operatively, has reportedly resulted in lung toxicity and death.² Further, the duration of this relationship is not well characterised. An exposure to Bleomycin in the past six months is considered by some to be a significant risk factor;² however for delivery of HBOT, even a remote history of Bleomycin therapy is an absolute contraindication.³

In patients with history of exposure to Bleomycin, requiring oxygen administration, inspired oxygen concentration is recommended to be kept at the lowest level, typically at FiO₂ of 0.22–0.25, that provides adequate tissue oxygenation. A single breath, carbon monoxide diffusion capacity (DLco) is considered to be the most predictive of potential pulmonary toxicity where HBOT is being considered.⁴

The authors in their case report have not described if the patient received any supplemental oxygen therapy after the administration of Bleomycin. Also, they report that the initial pulmonary function test revealed moderate restrictive defect with impaired gas exchange, and the repeat pulmonary function test was normal. It has not been mentioned if DLco was performed and how significantly it improved after resolution of lung lesions. The finding of improved DLco may have a positive bearing if the patient subsequently requires supplemental oxygen therapy for any reason.