The respiratory control of carbon dioxide in children and adolescents referred for treatment of psychogenic non-epileptic seizures

Abstract

Psychogenic non-epileptic seizures (PNES) are a common problem in paediatric neurology and psychiatry that can best be understood as atypical responses to threat. Threats activate the body for action by mediating increases in arousal, respiration, and motor readiness. In previous studies, a range of cardiac, endocrine, brain-based, attention-bias, and behavioral measures have been used to demonstrate increases in arousal, vigilance, and motor readiness in patients with PNES. The current study uses respiratory measures to assess both the motor readiness of the respiratory system and the respiratory regulation of CO₂. Baseline respiratory rates during clinical assessment and arterial CO₂ levels during the hyperventilation component of routine video electroencephalogram were documented in 60 children and adolescents referred for treatment of PNES and in 50 controls. Patients showed elevated baseline respiratory rates [t(78) = 3.34, p = .001], with 36/52 (69%) of patients [vs. 11/28 (39%) controls] falling above the 75th percentile (χ ² = 6.7343; df = 1; p = .009). Twenty-eight (47%) of patients [vs. 4/50 (8%) controls] showed a skewed hyperventilation-challenge profile-baseline PCO₂ <36 mmHg, a trough PCO₂ ≤ 20 mmHg, or a final PCO₂ <36 mmHg after 15 min of recovery-signaling difficulties with CO₂ regulation (χ ² = 19.77; df = 1; p < .001). Children and adolescents with PNES present in a state of readiness-for-action characterized by high arousal coupled with activation of the respiratory motor system, increases in ventilation, and a hyperventilation-challenge profile shifted downward from homeostatic range. Breathing interventions that target arousal, decrease respiratory rate, and normalize ventilation and arterial CO₂ may help patients shift brain-body state and avert PNES episodes.

Keywords: Conversion disorder; Dissociative convulsions; Functional neurological symptom disorder; Hyperventilation; Non-epileptic seizures.

Fig. 1

Hyperventilation profiles in children and adolescents assessed for PNES and in controls. The shaded blue area depicts the homeostatic range for arterial CO2. The top blue line depicts controls. Controls showed a clear pattern of PCO₂ changes during the HV task: a baseline PCO₂ within the homeostatic range, a steep drop in PCO₂ during HV, and a prompt return to homeostasis during recovery. The middle red line depicts the 60 children and adolescents with PNES who participated in the study. Children and adolescents with PNES showed a downwardly skewed HV-challenge profile suggesting difficulties with PCO₂ regulation. The bottom black line depicts the subgroup of 32 children and adolescents who whose PNES were typically preceded by—“triggered by”—HV