Central Respiratory Drive in Patients With Neuromuscular Diseases

Abstract

BACKGROUND:

The contribution of the central respiratory drive in the hypercapnic respiratory failure of neuromuscular diseases (NMD) is controversial.

OBJECTIVE:

To compare the CO₂ response and the duration of weaning of mechanical ventilation between a group of NMD patients and a group of quadriplegic patients due to ICU-acquired weakness (ICU-AW).

METHODS:

We prospectively studied 16 subjects with NMD and 26 subjects with ICU-AW ready for weaning, using the method of the re-inhalation of expired air. We measured the hypercapnic drive response, defined as the ratio of change in airway occlusion pressure 0.1 second after the start of inspiration (ΔP_0.1) to the change in Paco ₂ (ΔPaco ₂), and the hypercapnic ventilatory response, defined as the ratio of the change in minute ventilation (ΔV̇e) to ΔPaco ₂. We considered a value of ≤ 0.19 cm H₂O/mm Hg as reduced hypercapnic drive response.

RESULTS:

Hypercapnic drive response (ΔP_0.1/ΔPaco ₂ = 0.14 ± 0.08 cm H₂O/mm Hg vs 0.37 ± 0.27 cm H₂O/mm Hg, P = .002) and hypercapnic ventilatory response (ΔV̇e/ΔPaco ₂ = 0.21 ± 0.19 L/min/mm Hg vs 0.44 ± 0.40 L/min/mm Hg, P = .02) were lower in the NMD than in the ICU-AW subjects. Duration of weaning values, according to the Kaplan-Meier curves, were similar in both groups (Log-rank = 0.03, P = .96). Eleven NMD (69%) and 9 ICU-AW (35%) subjects had hypercapnic drive response ≤ 0.19 cm H₂O/mm Hg. The duration of weaning was longer in subjects with hypercapnic drive response ≤ 0.19 cm H₂O/mm Hg (log-rank = 15.4, P < .001).

CONCLUSIONS:

Subjects with acute hypercapnic respiratory failure due to NMD had reduced hypercapnic drive response, compared to ICU-AW subjects. The duration of weaning was longer in subjects with reduced hypercapnic drive response.