The validity and reliability of the clinical assessment of increased work of breathing in acutely ill patients.

Background: Mechanical ventilation is frequently indicated to reduce the work of breathing. Because it cannot be measured easily at the bedside, physicians rely on surrogate measurements such as patient appearance of distress and increased breathing effort.

Objective: We determined the validity and reliability of subjectively rating the appearance of respiratory distress and the reliability of 11 signs of increased breathing effort.

Subjects: The study included consecutive, acutely ill patients requiring various levels of respiratory support.

Methods: Blinded to each other's observations, a fellow and a critical care consultant rated the severity of distress (absent, slight, moderate, severe) after observing subjects for 10 seconds and then determined the presence of the signs of increased breathing effort.

Results: A total of 149 paired examinations occurred 6±6 minutes apart. The rating of respiratory distress correlated with oxygenation, respiratory rate, and 9 signs of increased work of breathing. It had the highest intraclass correlation coefficient (0.69; 95% confidence interval, 0.59-0.78). Rating distress as moderate to severe had a sensitivity of 70%, specificity of 92%, and positive likelihood ratio of 8 for the presence of 3 or more of hypoxia, tachypnea, and any sign of increased breathing effort. Agreement was moderate (κ = 0.53-0.47) for rating of distress, nasal flaring, scalene contraction, gasping, and abdominal muscle contraction, and fair (κ = 0.36-0.23) for sternomastoid contraction, tracheal tug, and thoracoabdominal paradox.

Conclusion: Assessing the increased work of breathing by rating the severity of respiratory distress based on subject appearance is a valid and moderately reliable sign that predicts the presence of serious respiratory dysfunction. The reliability of the individual signs of increased breathing effort is moderate at best.