Currently, the tools available for assessing peripheral muscle dysfunction in the intensive care setting require patient collaboration. Several studies have shown that peripheral muscle ultrasound is capable of reliably detecting morphological changes in critically ill patients, in addition to contributing to the identification of patients at higher risk of prolonged complications, especially when performed daily. In this sense, a valid, non-volitional alternative capable of determining muscle mass is through ultrasound assessment. However, current studies are characterized by a lack of standardization in their protocols, which include proper positioning of limbs, transducer, clear reference points and techniques for better visualization of the assessed muscle, in addition to significant methodological defects and inadequate sample sizes. We believe that, together with a tool capable of determining muscle mass and being a safe and non-invasive method, we can contribute to a more complete assessment of these patients, exploring outcomes such as survival, length of stay in the ICU, extubation success and functional capacity. In addition to having the potential to serve as a biomarker of muscle strength during rehabilitation, given little knowledge about the long-term physical consequences of COVID-19, thus promoting a more complete assessment, exploring morphological characteristics of the peripheral muscles resulting from the hospitalization process. and assisting the physiotherapist in clinical decision making in rehabilitation.

Introduction: the length of hospital stay may be associated with factors such as the need for mechanical ventilation, severity of the underlying disease, infections, use of sedation and neuromuscular blockers. In this context, the new coronavirus (SARS-CoV-2) presents itself as a group of viruses that can cause acute respiratory syndromes with mild and severe symptoms, contributing to increased hospital stays and periods of immobility. Peripheral muscle measurement through ultrasound is a topic of growing interest in the assessment of critically ill patients. Currently, this tool has been shown to be able to assess muscle dimensions and morphology during hospitalization in the intensive care unit (ICU) and can be performed at the bedside, presenting itself as a reliable inter and intraobserver method. As this tool does not depend on patient collaboration and is a non-invasive method available in most ICUs, it can provide additional information to the physical examination and clinical impression.

Objective: to evaluate the evolution of ultrasound pattern measurements in mechanically ventilated patients admitted to the ICU.

Methods: prospective cohort study that will be carried out in the ICU of the Recife Women's Hospital, located in Recife - PE, with individuals of both genders, over 18 years old, under mechanical ventilation due to suspicion or confirmation of COVID- 19. To carry out this study, the measurement of the ultrasound pattern of peripheral muscles will be performed from admission to the ICU, with follow-up on the 3rd, 5th and 7th days under mechanical ventilation. The length of stay in the ICU and mechanical ventilation, mortality in this population will also be evaluated. Clinical, laboratory, oxygenation, ventilation, respiratory system mechanics data will also be analyzed. Data will be collected and archived for analysis, which considers differences between groups with p<0.05. All ethical principles will be respected with either written Free and Consent Term by the patient or relatives at the intensive care phase or at the post ICU discharge phase.

Expected results: to contribute to a more complete assessment of these patients, exploring outcomes such as survival, length of stay in the ICU and effects of immobility on peripheral muscle mass.

Inclusion Criteria:

• Individuals of both genders;
• Age group over 18 years old;
• Individuals who had a confirmed diagnosis for COVID-19 considering their positivity through the RT-PCR exam on mechanical ventilation due to acute respiratory failure

Exclusion Criteria:

- Patients with neurological impairment or known myopathies

The sample consisted of volunteers with COVID - 19 admitted to the SRAG ICU on mechanical ventilation due to acute respiratory failure.