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IntroductionMechanical ventilation and the effect of respiratory muscle unloading on the diaphragm cause ventilator-induced diaphragmatic dysfunction (VIDD). Atrophy of the diaphragmatic muscle is a major part of VIDD, and has a rapid onset in most animal models. We wanted to assess the clinical evolution and risk factors for VIDD in an adult intensive care unit (ICU) by measuring diaphragm thickness using ultrasound.MethodWe performed a single-centre observational cohort study, including 54 mechanically ventilated patients. The right hemidiaphragm was measured daily at the zone of apposition on the midaxillary line.ResultsMean baseline thickness was 1.9 mm (SD ± 0.4 mm), and mean nadir was 1.3 mm (SD ± 0.4 mm), corresponding with a mean change in thickness of 32 % (95 % CI 27–37 %). Length of mechanical ventilation (MV) was associated with the degree of atrophy, whereas other known risk factors for muscle atrophy in an ICU were not. The largest decrease in thickness occurred during the first 72 hours of MV.ConclusionsDiaphragm atrophy occurs quickly in mechanically ventilated patients and can accurately be monitored using ultrasound. Length of MV, as opposed to other variables, is associated with the degree of atrophy.Clinical trial registrationClinicaltrials.gov NCT02299986. Registered 10/11/2014Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-015-1141-0) contains supplementary material, which is available to authorized users.

Ventilator-associated pneumonia (VAP) is one of the commonest hospital-acquired infections associated with high mortality. VAP pathogenesis is closely linked to organisms colonizing the endotracheal tube (ETT) such as Staphylococcus epidermidis and Pseudomonas aeruginosa, the former a common commensal with pathogenic potential and the latter a known VAP pathogen. However, recent gut microbiome studies show that pathogens rarely function alone. Hence, we determined the ETT microbial consortium co-colonizing with S. epidermidis or P. aeruginosa to understand its importance in the development of VAP and for patient prognosis. Using bacterial 16S rRNA and fungal ITS-II sequencing on ETT biomass showing presence of P. aeruginosa and/or S. epidermidis on culture, we found that presence of P. aeruginosa correlated inversely with patient survival and with bacterial species diversity. A decision tree, using 16S rRNA and patient parameters, to predict patient survival was generated. Patients with a relative abundance of Pseudomonadaceae <4.6% and of Staphylococcaceae <70.8% had the highest chance of survival. When Pseudomonadaceae were >4.6%, age of patient <66.5 years was the most important predictor of patient survival. These data indicate that the composition of the ETT microbiome correlates with patient prognosis, and presence of P. aeruginosa is an important predictor of patient outcome.

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