[Prolonged apnea/hypopnea during water swallowing in patients with amyotrophic lateral sclerosis]

Swallowing difficulty is increased along with progression of respiratory disturbance in patients with Amyotrophic Lateral Scalerosis (ALS). To analyze the respiratory patterns during swallowing is important for the management of this disease. In this study, we evaluated apnea/hypopnea during water swallowing and the respiratory cycle at rest and after water swallowing.

We evaluated respiratory patterns in swallowing in 10 ALS patients (66.0 +/- 7.1 years old), in 10 Myotonic dystrophy (MD) patients (46.5 +/- 12.2 years old), and in 10 healthy volunteers as control subjects (61.7 +/- 10.0 years old). The ALS and MD patients had consulted the Department of Neurology of Toneyama National Hospital or Tokushima National Hospital between April 2002 and July 2006. Respiratory patterns were evaluated by simultaneous recording of cervical swallowing sound in water swallow. A hypersensitive microphone measured cervical sound. A thermister was used for pneumography. The means of four continuous respiratory cycles at rest and after swallow of 3 ml water were used for analysis. Respiration with amplitude of 1/2 or smaller than that of the pneumography at rest was defined as hypopnea, and the apnea/hypopnea duration was evaluated as the respiratory suppression time.

All analyses were performed using SPSS 11.0J (SPSS Inc., Chicago, IL).

In the ALS group, the respiratory cycle was 3.15 +/- 0.76 sec (2.31-4.39 sec) at rest, while after swallowing, it was 2.78 +/- 0.83 sec (1.77-4.80 sec) (p = 0.1). In the MD group, the respiratory cycle was 2.56 +/- 0.46 sec (1.91-3.67 sec) at rest, while after swallowing, it was 2.94 +/- 0.60 sec (2.03-4.29 sec). In the control group, it was 3.46 +/- 0.57 sec (3.18-4.34 sec) at rest and 3.24 +/- 0.50 sec (2.64-4.04 sec) after swallowing. The apnea/hypopnea duration during water swallow was 14.33 +/- 8.89 sec (2.50-30.68 sec) in the ALS group, 3.66 +/- 1.58 sec (1.78-6.42 sec) in the MD group, and 3.64 +/- 1.00 sec (2.34-5.56 sec) in the control group. The apnea/hypopnea duration in the ALS group was significantly longer than that in MD and control groups (p = 0.005, p = 0.004 by the t-test). The ALS patients with severe respiratory failure or with aspiration in videofuoroscopy showed extended apnea/hypopnea duration.

Prolonged apnea/hypopnea was observed during water swallowing in ALS patients. We speculate that this prolongation is caused by severe swallowing disturbance and respiratory failure, which increases the risk of aspiration. The respiration of ALS patients should be closely monitored during eating.