New device for nonvolitional evaluation of quadriceps force in ventilated patients.

INTRODUCTION: In mechanically ventilated patients, nonvolitional assessment of quadriceps weakness using femoral-nerve stimulation (twitch force) while the leg rests on a right-angle trapezoid or dangles from the bed edge is impractical. Accordingly, we developed a knee-support apparatus for use in ventilated patients.

METHODS: Ninety subjects (12 ventilated patients, 28 ambulatory patients, and 50 healthy subjects) were enrolled. Twitches with leg-dangling, trapezoid, and knee-support setups were compared.

RESULTS: Knee-support twitches were similar to trapezoid twitches but smaller than leg-dangling twitches (P < 0.0001). Inter- and intraoperator agreement was high for knee-support twitches at 1 week and 1 month. In ventilated patients, knee-support twitches were smaller than in healthy subjects and ambulatory patients (P < 0.004).

DISCUSSION: The new knee-support apparatus allows accurate recording of quadriceps twitches. The ease of use in ventilated patients and excellent inter- and intraoperator agreement suggest that this technique is suitable for cross-sectional and longitudinal studies in critically ill patients. Muscle Nerve 57: 784-791, 2018.