The severity of muscle weakness after critical illness is very heterogeneous. To identify
those patients who may maximally benefit from early exercises would be highly valuable.
This implies an assessment of physical capacities, comprised at least of strength
measurement and functional tests.
The objective of this study was to investigate the relationship between muscle strength
and functional tests in an intensive care unit (ICU) setting.
Adults with ICU length of stay ≥2 days were included. Handgrip strength (HG) and maximal
isometric quadriceps strength (QS) were assessed using standardised protocols as soon
as patients were alert and able to obey commands. At the same time, their maximal
level of mobilisation capabilities and their autonomy were assessed using ICU Mobility
Scale (ICU-MS) and Barthel Index, respectively.
Ninety-three patients with a median age of 64 [57–71.5] years, body mass index of
26.4 [23.4–29.6] kg/m2, and Simplified Acute Physiology Score II of 33 [27.7–41] were included. Absolute
and relative QS were, respectively, 146.7 [108.5–196.6] N and 1.87 [1.43–2.51] N/kg.
HG was 22 [16–31] kg. The ICU-MS score was 4 [1–5]. A significant positive correlation
was observed between HG and absolute QS (rs = 0.695, p < 0.001) and between HG and relative QS (rs = 0.428, p < 0.001). The ICU-MS score correlated with HG, with a weak positive relationship
(rs = 0.215, p = 0.039), but not with QS. The ICU-MS score did not statistically differ
between the weakest and strongest patients for absolute or relative QS, but was lower
in patients with the lowest HG values (p = 0.01). A weak positive correlation was
observed between the Barthel Index and muscle strengths (maximum rs = 0.414, p < 0.001).
The present results suggest that, during ICU stay, there is no strong association
between muscle strength and functional test such as the ICU-MS or Barthel Index. Muscle
dynamometry and functional tests are probably complementary tools for physical capacities