Nocturnal hypoxia in motor neuron disease is not predicted by standard respiratory function tests

Background: With increasing awareness of motor neuron disease (MND) in Australia, the approach to respiratory management of patients with this disease will more commonly face the respiratory physician. Aim: The aim of this study was to determine if standard respiratory function tests could determine the presence of nocturnal hypoxia (NH) in patients with MND. Methods: Respiratory function tests were used to examine daytime respiratory function, and sleep studies were used to detect NH in 16 consecutive patients with MND and in 9 healthy control subjects. Demographic data, clinical parameters, respiratory function tests and sleep studies were obtained. Statistical analyses were carried out using t-tests and anova, where appropriate. Results: NH was detected in 50% of patients with MND, with no hypoxic events detected in the control group. Standard respiratory function tests were not able to predict the presence of NH. Conclusion: There was no correlation between respiratory function tests and NH. This study emphasizes the inability of standard respiratory function tests to predict NH that may arise early in the course of MND.