Evaluation of Abdominal Expiratory Muscle Thickness Pattern, Diaphragmatic Excursion, and Lung Ultrasound Score in Critically Ill Patients and Their Association with Weaning Patterns: A Prospective Observational Study

Abstract

Introduction: The expiratory muscles are an indispensable component of respiratory function in critically ill patients, yet is often overlooked. We evaluated the association of abdominal expiratory muscles thickness pattern with weaning.

Materials and methods: This was a single-center, prospective observational study done on 81 adult mechanically ventilated patients who underwent the weaning process.

Results: Sixteen patients had simple weaning and 65 patients had either difficult or prolonged weaning. The mean and standard deviation (SD) of the thickness of expiratory abdominal muscles-rectus abdominis (RA), internal oblique (IO), external oblique (EO), and transversus abdominis (TA) were significantly more in patients with simple weaning than those with difficult or prolonged weaning. The receiver operating curve (ROC) of expiratory muscles showed RA, IO, EO, TA cut-offs 0.638, 0.492, 0.315, and 0.253 cm, respectively, to predict simple weaning. The pattern of expiratory muscle thickness RA > IO > EO > TA was maintained in both simple and difficult/prolonged weaning groups (p = 0.362). The ROC of diaphragmatic excursion (DE) for predicting simple weaning had cut-off 1.79 cm. The lung ultrasound score (LUS) was 5.75 ± 3.32 in the simple weaning group, compared to 9.71 ± 5.18 in the difficult/prolonged weaning group (p = 0.005).

Conclusion: Abdominal expiratory muscles were significantly thicker in patients with simple weaning compared to those with difficult or prolonged weaning. The pattern of expiratory muscle thickness followed the pattern of RA > IO > EO > TA in both simple weaning and difficult or prolonged weaning groups. DE >1.79 cm predicted simple weaning and LUS was significantly lesser in patients with simple weaning (CTRI/2020/11/028895).

How to cite this article: Amara V, Vishwas P, Maddani SS, Natarajan S, Chaudhuri S. Evaluation of Abdominal Expiratory Muscle Thickness Pattern, Diaphragmatic Excursion, and Lung Ultrasound Score in Critically Ill Patients and Their Association with Weaning Patterns: A Prospective Observational Study. Indian J Crit Care Med 2022;26(3):307-313.

Keywords: Diaphragmatic excursion; Expiratory abdominal muscles; Expiratory muscle thickness pattern; External oblique; Internal oblique; Rectus abdominis; Transversus abdominis.

Flowchart 1

Flowchart depicting the methodology of the study

Fig. 1

Ultrasound depicting the rectus abdominis muscle (RA)

Fig. 2

Ultrasound depicting the external oblique (EO), internal oblique (IO), and transversus abdominis muscle (TA)

Fig. 3

Depiction of the Area Under Curve (AUC) as per Receiver Operating Characteristic (ROC) curve of the various variables – rectus abdominis (RA), internal oblique (IO), external oblique (EO), diaphragmatic excursion (DE), and diaphragmatic thickening fraction (DTF)% to predict simple weaning. Abdominal Expiratory Muscles—RA [AUC 0.712, p = 0.009, 95% CI (0.561, 0.862), cut-off 0.638 cm], IO [AUC 0.715, p = 0.008, 95% CI (0.558, 0.872) cut-off 0.492 cm], EO [AUC 0.718, p = 0.007, 95% CI (0.567, 0.869), cut-off 0.315 cm], TA [AUC 0.689, p = 0.019, 95% CI (0.557, 0.822), cut-off 0.253 cm], DE [AUC 0.700, p = 0.014, 95% CI (0.552–0.847), cut-off 1.79 cm], DTF% (AUC 0.548, p = 0.553)