Severe hypercapnia after low-flow oxygen therapy in patients with neuromuscular disease and diaphragmatic dysfunction

To increase the general awareness of the possible exacerbation of hypercapnia by the administration of low-flow oxygen in patients with neuromuscular disorders.

We retrospectively reviewed the medical records of 118 consecutive adult patients with a diagnosis of neuromuscular disease who underwent phrenic nerve conduction studies during a 5-year period, and we analyzed pulmonary function data for 8 patients who underwent arterial blood gas studies before and after the administration of low-flow oxygen.

In the eight patients with neuromuscular disease and diaphragmatic dysfunction (three with polymyositis, three with amyotrophic lateral sclerosis or nonspecific motor neuron disease, and one each with inflammatory motor neuropathy and chronic poliomyelitis), we analyzed the response of the arterial carbon dioxide tension (PaCO2) after low-flow supplemental oxygen therapy (0.5 to 2 L/min). Linear analysis was used to attempt to find correlations between respiratory variables and the PaCO2 response after oxygen therapy.

For the overall study group, the mean PaCO2 increased 28.2 +/- 23.3 torr after low-flow oxygen treatment; in five patients, it increased by 27 torr or more. Four patients who were subsequently treated with nocturnal assisted ventilation were able to use supplemental oxygen during the day with less severe hypercapnia. Statistical analysis failed to reveal specific correlations between increased PaCO2 values after oxygen therapy and any respiratory variables.

In patients with neuromuscular disease and diaphragmatic dysfunction, even low-flow supplemental oxygen should be administered with caution, and assisted ventilation should be strongly considered as an initial intervention.