[Effect of early off-bed mobility on diaphragm function in intensive care unit patients undergoing mechanical ventilation].

OBJECTIVE: To explore the improvement of diaphragm function after early off-bed mobility intervention in intensive care unit (ICU) patients undergoing mechanical ventilation. METHODS: A randomized controlled trial was conducted. A total of 147 adult patients undergoing mechanical ventilation admitted to ICU of Affiliated Hospital of Zunyi Medical University from October 2019 to March 2022 were enrolled. The patients were divided into control group and observation group by convenient sampling. Except for the different intervention programs of early mobility, other treatment and nursing of the patients in the two groups were carried out according to ICU routine. Progressive early activities were performed in the control group, while early off-bed mobility was performed in the observation group. The changes of diaphragm thickness at the end of inspiratory (DTei), diaphragm thickness at the end of expiratory (DTee) and diaphragm thickening fraction (DTF) before and 24, 48, 72 and 96 hours of intervention, and the duration of mechanical ventilation, length of ICU stay and 24-hour re-intubation rate after intervention were compared between the two groups. RESULTS: Among the 147 patients, there were 4 cases of detachment in the control group and 5 cases of detachment in the observation group. Finally, 138 patients were enrolled, 69 cases in the control group and 69 cases in the observation group. There was no significant difference in gender, age, diagnosis of ICU, sedatives, muscle strength, ventilator model, acute physiology and chronic health evaluation II (APACHE II) score and DTei, DTee, DTF before intervention between the two groups. The DTei, DTee and DTF in both groups were increased gradually with the extension of intervention time, especially in the observation group [DTei (cm) at 24, 48, 72 and 96 hours of intervention in the observation group were 0.247±0.014, 0.275±0.016, 0.300±0.013 and 0.329±0.013, while in the control group were 0.242±0.015, 0.258±0.013, 0.269±0.014, and 0.290±0.017, effect of time: F = 993.825, P = 0.000, effect of intervention: F = 82.304, P = 0.000, interaction effect between intervention and time: F = 84.457, P = 0.000; DTee (cm) of the observation group were 0.213±0.014, 0.227±0.013, 0.243±0.016, 0.264±0.010, while in the control group were 0.213±0.016, 0.218±0.013, 0.224±0.013, 0.234±0.014, effect of time: F = 385.552, P = 0.000, effect of intervention: F = 28.161, P = 0.000, interaction effect between intervention and time: F = 45.012, P = 0.000; DTF of the observation group were (15.98±4.23)%, (21.35±4.67)%, (24.09±4.44)% and (25.24±3.74)%, while in the control group were (14.17±4.66)%, (18.11±3.92)%, (20.22±4.19)% and (20.98±4.12)%, effect of time: F = 161.552, P = 0.000, effect of intervention: F = 49.224, P = 0.000, interaction effect between intervention and time: F = -4.507, P = 0.000]. The duration of mechanical ventilation and length of ICU stay in the observation group were significantly shorter than those in the control group [duration of mechanical ventilation (hours): 112.68±12.25 vs. 135.32±22.10, length of ICU stay (days): 7.84±1.78 vs. 10.23±2.43, both P < 0.01]. However, there was no significant difference in 24-hour re-intubation rate between the observation group and the control group (0% vs. 2.90%, P > 0.05). CONCLUSIONS: Both early off-bed mobility and progressive early activities can prevent diaphragm weakness in ICU patients undergoing mechanical ventilation, and the effect of early off-bed mobility is better. Early off-bed mobility can significantly shorten the duration of mechanical ventilation and length of ICU stay, and it is safe and feasible.

Fatigue Life Estimation for Suspenders of a Three-Pylon Suspension Bridge Based on Vehicle-Bridge-Interaction Analysis.

Fatigue damage of suspenders is a main concern during the life-cycle maintenance of arch bridges and suspension bridges. This paper presents a practical framework for estimating the fatigue life of suspenders under repeated traffic loads by taking a three-pylon suspension bridge as an example. First, the basic theory of vehicle-bridge interaction (VBI) is introduced and a finite element model of the bridge structure is established. Second, the fatigue load spectrum is defined in detail based on the analysis of WIM (weigh-in-motion) data. And then, parametric analysis is carried out to clarify the influence of road roughness, vehicle speed, and driving lanes. Among which, the time-dependent stress laws are simulated according to the defined fatigue load spectrum and the stress range is counted through the Rain flow counting method. At last, the fatigue life of uncorroded suspenders and naturally corroded suspenders is estimated by an S-N curve and Miner cumulative damage criterion. Results reveal that the fatigue life of suspenders is more than 100 years if no corrosion happens, while less than 20 years for short suspenders considering the influence of natural corrosion.

Atmospheric Initial Nucleation Containing Carboxylic Acids.

The possible involvement of chemical components in atmospheric new particle formation has received increased attention in recent years. However, the deep understanding of the clusters formed between atmospheric gas-phase organic acids is incomplete. In this work, the chemical and physical properties of the cluster formed between three organic acids [glyoxylic acid (GA), oxalic acid (OA), and pyruvic acid (PA)] with common atmospheric nucleation precursors [methyl hydrogen sulfate (MHS), methanesulfonic acid (MSA), and hydroxymethanesulfonic acid (HMSA)] have been investigated with density functional theory and ab initio coupled-cluster singles and doubles with perturbative triples (CCSD(T)) theory. Six- to nine-membered cyclic ring structures are mainly arranged via two classes of intermolecular hydrogen bonds: SO-H···O and CO-H···O. The GA/OA/PA-MHS/MSA/HMSA complexes with the nine- and eight-membered cyclic ring structures are thermodynamically more stable than the others. Large red shifts of the OH-stretching vibrational frequencies of both SO-H···O (354-794 cm-1) and CO-H···O (320-481 cm-1) are obtained with regard to the isolated gas monomers. Atoms in molecules topological analysis reveals that the Laplacian of the charge density of the bimolecular interactions in the GA/OA/PA-MHS/MSA/HMSA complexes is higher than the upper value of the hydrogen bond criteria. The thermodynamic data, dipole moments, and atmospheric mixing ratios indicate that the MHS- and MSA-containing complexes possibly take part in atmospheric new particle formation. Additionally, the environmental factors, such as temperature and pressure, are also important in atmospheric particle nucleation, and the gas-mixing ratios of the clusters at 12 km are much enhanced by 18-44 times with respect to the ones at the ground level. This study suggests that small cluster calculations may be helpful in simulating atmospheric new particle formation.