Transtracheal Gas Administration and the Perception of Dyspnea

The effects of nasal cannula gas flow on dyspnea have been studied by Liss and Grant (Am Rev Respir Dis 1988;137:1285), who concluded that reduction of dyspnea was a placebo effect from the wearing of the nasal cannula. We conducted a similar study in subjects using transtracheal oxygen catheters (TTOCs). METHODS: Nine patients with chronic lung disease and hypoxemia were administered zero flow, 2 and 4 L/min of air, and 2 and 4 L/min of oxygen via their TTOCs. After each study segment, the subjects recorded their degree of dyspnea on a visual analog scale (VAS) calibrated from 0 (not short of breath) to 100 (extremely short of breath). After the first five tests, the subjects' tracheas were anesthetized with topical 1% lidocaine via their TTOCs, and the five tests were repeated. RESULTS: Prior to tracheal anesthesia, air and oxygen flows at 4 L/min produced significantly higher VAS scores (more dyspnea) than at baseline (air, p = 0.0233; oxygen, p = 0.0183). Air and oxygen at 2 L/min did not produce VAS scores significantly higher than baseline scores (air, p = 0.3196; oxygen, p = 0.0669). VAS scores associated with 4 L/min air and oxygen flows were significantly higher than scores associated with 2 L/min flows (p = 0.0179). VAS scores during zero flow prior to tracheal anesthesia were not significantly different from baseline VAS values (p = 0.5534). After tracheal anesthesia, no significant relationship was found between gas flowrate and VAS scores (p = 0.9618). The anesthesia appeared to eliminate the effect of transtracheal gas flow on dyspnea. CONCLUSIONS: Transtracheal gas administration can affect the perception of dyspnea in patients with chronic lung disease. This effect on flow-sensitive tracheal receptors appears to be abolished by tracheal anesthesia .