Background: Failure to wean from invasive mechanical ventilation is multifactorial, with diaphragmatic dysfunction a significant contributing factor. Diaphragmatic function can be easily and non-invasively assessed by ultrasound. However, it remains unknown how ultrasound measurements of diaphragm function are affected by changes in apparent work of breathing. Methods: In patients undergoing weaning from mechanical ventilation, we evaluated diaphragmatic ultrasound measurements [diaphragmatic excursion (Dex), diaphragmatic thickening fraction (Tfdi)] simultaneously with manometric indices of breathing effort and load [esophageal pressure swings (ΔPes), transdiaphragmatic pressure swings (ΔPdi), and the pressure–time product of esophageal pressure (PTPes)]. These assessments were performed during two distinct phases; during an unassisted spontaneous breathing trial (phase SBT) and during an inspiratory resistive loading with 30 cmH₂O/L/s (phase IRL), applied during the same SBT. Our primary aim was to evaluate the relationship between diaphragmatic ultrasound and breathing effort using the method of repeated measures correlation. Results: Forty-nine patients were enrolled. Dex correlated with ΔPes (r = 0.5, p < 0.001), ΔPdi (r = 0.55, p = < 0.001) and PTPes (r = 0.32, p = 0.031). Tfdi did not correlate with ΔPes (r = 0.27, p = 0.052), ΔPdi (r = 0.2, p = 0.235) and PTPes (r = 0.24, p = 0.110). Dex and Tfdi increased during IRL compared to SBT [1.44(0.89–1.96) vs. 1.05(0.7–1.59), p = 0.002], [0.55(± 0.32) vs 0.46(± 0.2), p = 0.019] as did Pes, Pdi and PTPes [(11.87 (7.86, 18.32) vs. 6.8 (4.6–10.23), p < 0.001), (10.89 (± 6.42) vs. 7.94 (± 3.81), p < 0.001), and (181.10 (108.34, 311.7) vs. 97.52 (55.96–179.87), p < 0.001), respectively]. Conclusion: In critical care patients spontaneously breathing under resistive load, diaphragmatic excursion had a weak to moderate correlation with indices of breathing effort and differed between weaning success and failure.

OBJECTIVES: Weaning failure from mechanical ventilation (MV) is primarily caused by increased respiratory load and decreased respiratory neuromuscular competency, leading to a rapid shallow breathing pattern. We hypothesized that the product of diaphragmatic contraction velocity (a sonographic estimate of respiratory load) and tidal volume (an estimate of breathing pattern), termed the volume-velocity index (VVI), may predict weaning outcomes. DESIGN: The diagnostic accuracy of VVI (mL*cm/s) in predicting weaning outcomes was prospectively assessed, along with its relationship to indices of breathing effort, including esophageal pressure swings (ΔPes), the pressure-time product of esophageal pressure (PTPes), and maximal inspiratory pressure (MIP). A power analysis, informed by the results of an inception cohort, determined the required sample size for the validation cohort. Patients were enrolled through consecutive sampling. Weaning failure was defined as failure of the spontaneous breathing trial (SBT) or the need for MV within 48 hours. SETTING: The study was conducted in a tertiary academic ICU. PATIENTS: VVI was evaluated in critical care patients undergoing a SBT for the first time. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: In the inception cohort ( n = 30), VVI was significantly higher in successful weaning compared to failures (764.76 [±432.61] vs. 278 [±183.66], p < 0.001). It correlated with ΔPes ( r = 0.74, R ² = 0.55), PTPes ( r = 0.76, R ² = 0.58), and MIP ( r = 0.75, R ² = 0.55) all p values less than 0.001. In the validation cohort ( n = 40), VVI was higher in successful weaning (840 [550, 1220] vs. 250 [225, 302.5], p < 0.001) and predicted weaning success with an area under the receiver operating characteristic of 0.92 (95% CI, 0.83–1). CONCLUSIONS: VVI effectively differentiates between weaning success and failure, shows a strong correlation with respiratory effort indices, and may enhance weaning protocols.

BACKGROUND: Patients with a tracheostomy and difficult weaning from invasive mechanical ventilation constitute a challenging problem in critical care. An increased duration of ventilation may lead to diaphragmatic dysfunction and a noninvasive assessment of the diaphragm, such as ultrasound, attracts interest in the clinical practice. We evaluated the relationship of ultrasound-derived indices with weaning outcome and with established indices of respiratory strength and load in subjects who are tracheostomized and undergoing weaning. METHODS: This prospective study was conducted at an academic ICU in Greece. Twenty subjects with tracheostomy and difficult weaning, during a spontaneous breathing trial, underwent time synchronous diaphragmatic sonography and esophageal manometry, to assess diaphragmatic excursion and thickening fraction, esophageal and transdiaphragmatic pressures, pressure-time product of the esophageal pressure, and maximum inspiratory pressure. The primary outcome was liberation from mechanical ventilation at 48 h. The relationship of diaphragmatic ultrasound with esophageal pressure–derived indices was also evaluated. RESULTS: Weaning from invasive ventilation failed in 10 subjects. Diaphragmatic excursion exhibited a significant difference between weaning success and failure (1.34 ± 0.56 versus 0.79 ± 0.44; P = .044), a strong correlation with transdiaphragmatic pressure (r = 0.7, P = .02), and a moderate correlation with the pressure-time product of the esophageal pressure (r = 0.65, P = .02) and the maximum inspiratory pressure (r = 0.66, P = .02). Transdiaphragmatic pressure presented the highest area under the curve (0.97). However, when transdiaphragmatic pressure was compared with diaphragmatic excursion (area under the curve, 0.84) for predictive accuracy, no significant difference was found. CONCLUSIONS: Diaphragmatic excursion is a valuable tool for the assessment of diaphragmatic strength, respiratory load, and weaning prediction.

Background: Bacterial co-infections in patients with viral pneumonia might increase mortality. In this study we aimed to evaluate their effect on the mortality of critically ill patients with viral pneumonia. Methods: A systematic search was conducted in PubMed, Web of Science, Scopus and Cochrane from inception until 30 March 2025. We included studies comparing the effect on mortality of bacterial co-infections in critically ill patients with viral pneumonia. The risk of bias was assessed by the Newcastle–Ottawa Scale. Results: From 3643 studies, 10 were included in our study with a total of 2862 COVID-19 patients and 4573 influenza patients. Seven studies were retrospective and three prospective. In total, 359/2862 of the COVID-19 and 904/4573 of the influenza patients were co-infected. Co-infections increased mortality in five out of the six studies evaluating COVID-19 patients and in two out of the eight studies evaluating influenza patients. Conclusions: The majority of the included studies were retrospective, which may limit the accuracy of these results. The exclusion of non-English literature may have led to the omission of relevant data. Based on our results, the impact of bacterial co-infection may be more pronounced in patients with COVID-19 pneumonia admitted to the ICU than in patients with influenza pneumonia.