Influence of Body Position Changes on Diaphragmatic Excursion Assessed by Ultrasonography in a Healthy Population

Background: The diaphragm is the primary respiratory muscle, and its proper function is essential for efficient breathing. Respiratory muscle weakness is a common complication that can hinder the withdrawal of mechanical ventilation. This weakness not only negatively affects patients' quality of life but also represents an economic challenge for healthcare systems, as it significantly increases medical costs due to prolonged hospitalization and the need for additional procedures to manage associated complications. Ultrasonography has emerged as a precise technique for assessing diaphragmatic function through measurements such as diaphragmatic excursion and thickening fraction, with the right hemidiaphragm being the most suitable for evaluation. However, several studies have shown that diaphragmatic ultrasound measurements vary considerably in both healthy individuals and patients, mainly due to the lack of standardization of body position during assessment. Therefore, it is necessary to investigate how patient posture influences diaphragmatic ultrasound measurements in order to standardize protocols, improve diagnostic accuracy, and support reliable clinical decision-making. We employed ultrasonography to determine the influence of changes in body position on diaphragmatic excursion in a healthy population from the city of Cali. Methods: A descriptive cross-sectional study was conducted in 36 healthy adults aged 18 to 65 years, distributed into sex and age groups. Diaphragmatic excursion was assessed using a 3.5-5 MHz ultrasound transducer. Participants were evaluated in five body positions: supine at 0°, and head-of-bed inclinations of 30°, 45°, 70°, and 90°. Results: A progressive increase in diaphragmatic excursion was observed from the supine position (0°) up to 70° inclination. The 70° inclination showed the greatest diaphragmatic mobility as measured by ultrasonography. This finding suggests the existence of an optimal intermediate position in which biomechanical conditions and intra-abdominal pressure allow more efficient diaphragmatic contraction. Conclusions: The results of this study demonstrate that changes in body position significantly influence diaphragmatic excursion in healthy individuals, with a trunk inclination of 70° yielding the greatest diaphragmatic mobility. These findings support the importance of considering body posture as a key determinant in the functional assessment of the diaphragm using ultrasonography.