Measurement of dyspnea in patients treated with mechanical ventilation.

BACKGROUND: Dyspnea, or difficult breathing, is common in patients receiving mechanical ventilation; however, dyspnea is not routinely or systematically measured.
OBJECTIVE: The primary purpose of this methodological study was to evaluate the test-retest reliability of 5 dyspnea rating scales and the criterion validity of 4 dyspnea rating scales in patients receiving mechanical ventilation. The secondary purpose was to examine the correlations between each of these 5 rating scales and physiological measures of respiratory function.
METHODS: The convenience sample consisted of 28 patients on mechanical ventilation during their hospitalization in the intensive care units of a large, inner-city hospital. Patients rated their dyspnea twice at 30-minute intervals on the visual analogue scale, the vertical analogue dyspnea scale, the modified Borg scale, the numerical scale, and the faces scale. Test-retest reliability was computed by using the intraclass correlation coefficient. Criterion validity was evaluated by using the Spearman rank-order correlation coefficient.
RESULTS: The 5 rating scales had acceptable test-retest reliabilities, with intraclass correlation coefficients ranging from 0.81 to 0.97. Criterion validity of the 4 scales also was acceptable, with Spearman rank-order correlation coefficients from 0.76 to 0.96. The rating scales were not correlated with most of the physiological variables. At least half of the patients reported moderate to severe dyspnea.
CONCLUSION: The scales showed acceptable reliability and validity, and they will be useful in quantifying dyspnea experienced by patients receiving mechanical ventilation. Further work is needed to evaluate the extent and the severity of dyspnea in such patients in order to evaluate the effectiveness of interventions.