Neuromuscular Electrical Stimulation in Critically Ill Patients Aged 80 and Over

The aim of this clinical trial is to evaluate the effectiveness of Medium-Frequency Neuromuscular Electrical Stimulation, in combination with standard physical therapy, compared to standard physical therapy alone, on muscle mass, muscle strength, and functionality in critically ill patients aged 80 and over during their hospital stay. The safety of the intervention and the standardization of protocol parameters will also be assessed.

The main research questions are:

* Does the implementation of a standardized Medium-Frequency Neuromuscular Electrical Stimulation protocol, in combination with standard physical therapy, compared to standard physical therapy alone, help attenuate the loss of skeletal muscle mass, strength, and functionality in critically ill patients aged 80 and over? * Is the use of this protocol and its proposed parameters safe for critically ill patients aged 80 and over? The study will consist of applying a standardized Medium-Frequency Neuromuscular Electrical Stimulation protocol to oldest old patients admitted to the Intensive Care Unit of Dr. Hernán Henríquez Aravena Hospital in Temuco, Chile. The sample will consist of oldest old participants (≥80 years), who will be randomly divided into two subgroups: a control group that will receive standard physical therapy typically provided during hospitalization, and an experimental group that will receive the same standard therapy plus Medium-Frequency Neuromuscular Electrical Stimulation, which will begin within the first 48 hours of Intensive Care Unit admission.

The following variables will be assessed in both groups (control and experimental), from Intensive Care Unit admission to hospital discharge:

* Skeletal muscle mass characteristics and evolution (quadriceps femoris and anterior tibialis muscle thickness), measured by ultrasonography. * Handgrip strength, measured using a digital hand dynamometer. * Inspiratory muscle strength, assessed using a pimometer. * Peripheral muscle strength, evaluated with the Medical Research Council Sum Score (MRC-SS). * Functionality, assessed by the Functional Status Score for the Intensive Care Unit (FSS-ICU) . * Independence in basic activities of daily living, measured using the Barthel Index. * Quality of life, evaluated using the Short Form-36 Health Survey (SF-36). * Cognitive impairment, assessed through the Montreal Cognitive Assessment (MoCA). * Frailty, measured using the Clinical Frailty Scale (CFS).