Diaphragm Morphology and Function in Neurocritical Care Patients: Uncovering Key Correlations With Respiratory Muscle Strength Under Mechanical Ventilation

Abstract

Background and Purpose: Severe neurological injuries frequently necessitate prolonged invasive mechanical ventilation (IMV), which contributes to diaphragm atrophy and weakness. These factors can complicate the weaning process and have a detrimental impact on clinical outcomes in neurocritical care patients. This study aimed to examine the morphology and function of the diaphragm in neurocritical patients undergoing IMV, with a particular focus on the relationship between these factors and respiratory muscle strength. Methods: This prospective observational study included 20 neurocritical patients admitted consecutively to an intensive care unit (ICU). All patients were mechanically ventilated in pressure support ventilation (PSV) mode for 24–72 h. Diaphragm morphology and function were assessed using ultrasound, while respiratory muscle strength was measured via manovacuometry to determine maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP). Results: The mean diaphragm thickness (DT) was 1.7 mm (95% CI: 1.4–1.9), and diaphragmatic excursion (DE) was 20.4 mm (95% CI: 17.5–23.2). The mean MIP was −50 cmH2O (95% CI: −55.0 to −40.6), and the mean MEP was 30 cmH2O (95% CI: 26.5–42.9). There was a moderate correlation between MIP and DT (r = −0.45, p < 0.05) and between MEP and DT (r = 0.50, p = 0.03). Ultrasound measurements showed no significant relationship with ICU length of stay, IMV duration, or demographic variables such as sex, age, or body mass index (BMI). However, DT at the end of expiration influenced maximal respiratory pressure (MRP), with female patients exhibiting 92% weaker MIP compared to males. Discussion: Diaphragm thickness was found to moderately correlate with respiratory muscle strength in neurocritical care patients on IMV, suggesting its potential as a marker for muscle strength assessment. However, no significant relationship was found between other ultrasound variables and clinical outcomes such as IMV duration or ICU stay. These findings underscore the need for further longitudinal studies to explore diaphragmatic muscle behavior throughout hospitalization and its impact on clinical outcomes.