Serum doxapram and respiratory neuromuscular drive in normal man

Summary

To investigate the means by which doxapram affects the control of ventilation, ventilatory function and P_0.1 have been related to serum doxapram concentration during a 45-min infusion of doxapram hydrochloride in 7 healthy, conscious subjects under normoxic conditions.

Serum doxapram concentrations increased during the infusion: 1.88, 2.48, 3.42, and 3.97 µg/ml after 5, 10, 30 and 45 min, respectively. The majority of significant changes in the measurements from the baseline were observed at 30 and 45 min:${{\dot V}}_{{E}}$, V_T, P_0.1, P_0.1/end-tidal CO₂ tension, V_T/T_i and blood pressure were increased, and end-tidal CO₂ tension was decreased.

No significant changes in Pdi_max, T_i/T_tot,${{\dot V}}_{{E}}$/P_0.1, and P_0.1/(V_T/T_i) were observed. A correlation was observed between the % increases in P_0.1 and${{\dot V}}_{{E}}$ and doxapram concentration, and between${{\dot V}}_{{E}}$ and P_0.1.

The doxapram-induced increase in${{\dot V}}_{{E}}$ appears to be caused by increased neural drive. It is related to the serum drug concentration in the conscious subject.