Maximum Inspiratory Pressure, Grip Strength and Physical Functional Status Relationship in MV Patients

Progressive inadequate ventilation results in multiple organ dysfunction due to impaired oxygenation and subsequent hypoxia. Additionally, the combined effects of reduced exercise capacity and increased oxidative stress contribute to cardiovascular failure, further immobilization, increased peripheral muscle weakness, and a diminished quality of life. From this standpoint, there is a dynamic interaction between the respiratory muscles and peripheral striated muscles; strengthening one muscle group positively influences the other. Respiratory muscle strength is closely related to both limb muscle strength and endurance. Therefore, it is essential to assess not only respiratory but also peripheral muscle strength in mechanically ventilated patients.

Maximum Inspiratory Pressure (MIP) and Maximum Expiratory Pressure (MEP) are functional units used to assess respiratory muscle strength. In this context, various measurement methods developed to determine MIP and MEP provide valuable insights into the condition of patients' respiratory muscles. Although invasive methods are sometimes used to evaluate respiratory muscle strength in mechanically ventilated patients, simple bedside measurements are often sufficient. One such method, particularly for ventilator-dependent patients, utilizes the negative inspiratory pressure value available through the ventilator's software features. In this procedure, the intensive care unit clinician instructs the patient to perform a strong inspiratory effort against a "closed circuit" within the system, and the resulting pressure serves as an indicator of inspiratory muscle strength. It is crucial that the patient is informed about the absence of airflow during this procedure and that they are cooperative.

Peripheral muscle strength is typically assessed using muscle strength tests or isokinetic evaluations. Additionally, grip strength measurement serves as a non-invasive indicator of both functional status and peripheral muscle strength in patients on mechanical ventilation .Respiratory muscles work in a complex interaction with peripheral muscles.This dynamic relationship has been described in many populations. In certain disease groups, peripheral muscle strength has been assessed through grip strength, while respiratory muscle strength was measured using maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) values, allowing for the determination of the relationship between these two muscle groups. Typically, MIP is measured in the literature using manometers and specialized devices. However, this study was designed to measure MIP using the negative inspiratory pressure value-equivalent to maximal inspiratory pressure-directly from the mechanical ventilation device, without the use of external equipment and without disconnecting the patient from the respiratory circuit.The aim of this study is to determine the relationship between maximal inspiratory pressure, grip strength, and physical functional status in mechanically ventilated patients.

Inclusion criteria

• Hemodynamically stable
• Consciousness level sufficient to follow commands
• Patients with functionally intact extremities

Exclusion criteria

• Patients with neurological disorders (central or peripheral)
• Patients with craniocerebral injury
• Patients using medications that affect muscle tone
• Patients using sedative agents