The experience of dyspnea during weaning.

OBJECTIVE

To compare the degree of dyspnea experienced by ventilator-dependent patients receiving synchronized intermittent mandatory ventilation (SIMV) versus T-piece or pressure support ventilation (PSV) weaning. The relationship between self-reported perceptions of dyspnea and physiologic variables observed during weaning trials was examined. Variables included heart rate, respiratory rate, minute ventilation, and oxygen saturation as measured by a pulse oximeter.

DESIGN

Quasi-experimental, counterbalanced design with repeated measures.

SETTING

Medical intensive care unit of a large university-affiliated medical center.

PATIENTS

Nine mechanically ventilated patients diagnosed with chronic obstructive lung disease. The patients were admitted for respiratory failure between May 1990 to November 1990. Six tolerated SIMV 4 versus T-piece trials; three were placed in the SIMV 8 versus PSV trials.

PROCEDURE

Each patient's perception of dyspnea was measured using a visual analog scale (VAS) at the initiation and at 5-minute intervals of 20-minute weaning trials. Physiologic indicators were noted simultaneously with VAS ratings of dyspnea.

RESULTS

Findings indicated no difference in the degree of dyspnea experienced between weaning methods compared. Within-subject regression analysis on VAS scores revealed individual differences in the relationship between physiologic indicators and perceptions of dyspnea.

CONCLUSIONS

The patient's experience of dyspnea during the weaning process can be a valuable guide to observe the patient's progress. The VAS serves as a reliable, easy-to-use tool for quantifying the patient's perception of dyspnea.