1995 OPEN FORUM Abstracts
TRANSTRACHEAL AIRWAY INSUFFLATION OF HELIUM-OXYGEN MIXTURES REDUCES APPARENT WORK OF BREATHING
D. Onorato, MD; A. Derosa, RRT; J. Zodda, RRT; P. Harrison, RRT; J. Gagliardi, Engineer. Pulmonary Division, Respiratory Care Department, Mechanical Engineering, Hartford Hospital, Hartford, CT; Pulmonary Science Associates, Hartford, CT.
INTRO: Helium is a biologically inert, insoluble gas whose Reynolds number, density and kinematic viscosity favor the production of laminar flow at all flow rates thereby reducing resistance to airflow in the conducting airways. Mixtures of heliox have been demonstrated to reduce dead space, PIP, inspiratory and expiratory work of breathing and alter ventilation-perfusion relationships in animal models of obstructive lung disease. Although effective, large quantities of heliox are wasted due to inspiratory and expiratory losses into the atmosphere. Transtracheal airway insufflation has been demonstrated to reduce work of breathing, enhance minute ventilation and conserve oxygen utilization. We reason that a substitution of heliox for nitrox delivered through a transtracheal catheter system would reduce apparent work of breathing, enhance minute ventilation and reduce apparent gas utilization.
Methods: Five spontaneously breathing adult patients with obstructive lung disease requiring transtracheal oxygen therapy (3 males, 2 females) who gave informed consent were examined breathing mixtures of nitrox (80/20, 70/30) and heliox (80/20, 70/30). Esophageal balloon was placed into the distal esophagus and calibrated. Work of breathing was calculated from alterations in the pressure-volume curve (Bicore, CPU, Irvine, Calif.). Transducers calibrated for 80% helium and 70% helium were utilized during heliox breathing. Gas was delivered through a mature miniostomy site via a transtracheal catheter (Scoop-1, Transtracheal System, Englewood, Colo.). Respiratory rate and inspiratory volume were stereotyped by timing with a metronome and breathing through a 600 cc bag system. See data below (mean ±SEM).
WORK OF BREATHING (Joules)
TGI Flow Heliox (N=5) Nitrox (N=5)
80/20 [Delta] %70/30 [Delta] %80/20 [Delta] %70/30 [Delta] %
0 0.34 (0.02)0.32 (0.01)0.34 (0.05)0.34 (.03)
2 0.30 (0.01) 11.70.30 (0.01)6.20.34 (0.05) 0 0.34 (0.02) 0
4 0.26 (0.01) 240.29 (0.01) 14.70.34 (0.02) 0 0.33 (0.02) 3
6 0.22 (0.01) 350.24 (0.01) 25 0.30 (0.01) 11.50.31 (0.02) 8
8 0.20 (0.01) 410.24 (0.01) 25 0.28 (0.10) 170.29 (0.02) 14
FINDINGS: Transtracheal gas insufflation reduces measured work of breathing in a dose dependent manner. Insufflation of heliox reduced apparent work of breathing greater than insufflation of nitrox. Heliox 70/30 and 80/20 reduced work of breathing 25-41% respectively. Nitrox 70/30/and 80/20 reduced work of breathing 14-18% respectively. The reduction of work of breathing due to heliox is mediated by a combination of inspiratory augmentation of minute ventilation and reduced airflow resistance, whereas the reduction in work of breathing with nitrox insufflation is due to minute ventilation augmentation alone. These observations suggest that the use of transtracheal heliox mixtures may be beneficial in patients with obstructive lung disease.