Effects of intraoperative individualized PEEP on postoperative atelectasis in obese patients: study protocol for a prospective randomized controlled trial.

BACKGROUND: Obese patients undergoing general anesthesia and mechanical ventilation during laparoscopic abdominal surgery commonly have a higher incidence of postoperative pulmonary complications (PPCs), due to factors such as decreasing oxygen reserve, declining functional residual capacity, and reducing lung compliance. Pulmonary atelectasis caused by pneumoperitoneum and mechanical ventilation is further aggravated in obese patients. Recent studies demonstrated that individualized positive end-expiratory pressure (iPEEP) was one of effective lung-protective ventilation strategies. However, there is still no exact method to determine the best iPEEP, especially for obese patients. Here, we will use the best static lung compliance (Cstat) method to determine iPEEP, compared with regular PEEP, by observing the atelectasis area measured by electrical impedance tomography (EIT), and try to prove a better iPEEP setting method for obese patients. METHODS: This study is a single-center, two-arm, prospective, randomized control trial. A total number of 80 obese patients with body mass index ≥ 32.5 kg/m2 scheduled for laparoscopic gastric volume reduction and at medium to high risk for PPCs will be enrolled. They will be randomly assigned to control group (PEEP5 group) and iPEEP group. A PEEP of 5 cmH2O will be used in PEEP5 group, whereas an individualized PEEP value determined by a Cstat-directed PEEP titration procedure will be applied in the iPEEP group. Standard lung-protective ventilation methods such as low tidal volumes (7 ml/kg, predicted body weight, PBW), a fraction of inspired oxygen ≥ 0.5, and recruitment maneuvers (RM) will be applied during and after operation in both groups. Primary endpoints will be postoperative atelectasis measured by chest electrical impedance tomography (EIT) and intraoperative oxygen index. Secondary endpoints will be serum IL-6, TNF-α, procalcitonin (PCT) kinetics during and after surgery, incidence of PPCs, organ dysfunction, length of in-hospital stay, and hospital expense. DISCUSSION: Although there are several studies about the effect of iPEEP titration on perioperative PPCs in obese patients recently, the iPEEP setting method they used was complex and was not always feasible in routine clinical practice. This trial will assess a possible simple method to determine individualized optimal PEEP in obese patients and try to demonstrate that individualized PEEP with lung-protective ventilation methods is necessary for obese patients undergoing general surgery. The results of this trial will support anesthesiologist a feasible Cstat-directed PEEP titration method during anesthesia for obese patients in attempt to prevent PPCs. TRIAL REGISTRATION: www.chictr.org.cn ChiCTR1900026466. Registered on 11 October 2019.

Constitutive expression of NtabSPL6-1 in tobacco and Arabidopsis could change the structure of leaves and promote the development of trichomes.

The coding sequence of NtabSPL6-1 was cloned by high-fidelity PCR with specific primers and was used in construction of a binary vector for overexpression. Wild-type Col-0 Arabidopsis plants and Qinyan95 tobacco leaves were transformed using floral dip and leaf disc methods, respectively. Phenotypic observation showed that constitutive expression of NtabSPL6-1 in Arabidopsis could promote the development of trichomes on leaf epidermis and influence the growth pattern of cauline leaves. In tobacco, ectopic expression of NtabSPL6-1 led to dwarfism of the plants and alteration of the leaf structure, accompanied by changes of the glandular trichomes in development. At the same time, the self-regulation capability of NtabSPL6-1 was determined by yeast two-hybrid system. The results indicated that SBP-C terminal domain and C terminal domain of NtabSPL6-1 possessed strong transcriptional activation ability; the intact protein, N terminal domain, and the first peptide fragment in N terminal domain possessed weak transcriptional activation ability; and the second and the third peptide fragments in N terminal domain had no transcriptional activation ability, suggesting the N terminal domain of NtabSPL6-1 could block the activity of the C terminal domain. NtabSPL6-1 may affect the resistance of plants to biotic stress factors indirectly by regulation of the trichome growth.

Characterization and phylogenetic analysis of fifteen NtabSPL genes in Nicotiana tabacum L. cv. Qinyan95.

Fifteen SPL (SQUAMOSA PROMOTER BINDING PROTEIN-LIKE) genes were identified and characterized in Nicotiana tabacum L. cv. Qinyan95. The exon-intron structures of these genes were determined according to the coding sequences confirmed by RT-PCR and the genomic DNA sequences downloaded from the databases in Sol Genomics Network, and thirteen of them were found to carry the response element of miR156. To elucidate the origin of the validated NtabSPL genes, multiple alignments of the nucleotide sequences encompassing the open reading frames were conducted by using the orthologs in N. tabacum, Nicotiana sylvestris, Nicotiana tomentosiformis, and Nicotiana otophora. The results showed that six NtabSPL genes were derived from a progenitor of N. sylvestris, and nine NtabSPL genes were derived from a progenitor of N. tomentosiformis, further corroborating that N. tabacum came from the interspecific hybridization between the ancestors of N. sylvestris and N. tomentosiformis. In contrast to previous statements about highly repetitive sequences, the genome of N. tabacum mainly retained the paternal-derived SPL genes in diploidization process. Phylogenetic analyses based on the highly conserved SBP (SQUAMOSA PROMOTER BINDING PROTEIN) domains and the full-length amino acid sequences reveal that the SPL proteins of tobacco, tomato, and Arabidopsis can be categorized into eight groups. It is worth noting that N. tabacum contains seven NtabSPL6 genes originated from two parental genomes and NtabSPL6-2 possesses a GC-AG intron. In addition, transgenic tobacco plants harboring Arabidopsis Pri-miR156A were generated by Agrobacterium-mediated transformation method, and the constitutive expression of miR156 could obviously inhibit the activity of the NtabSPL genes containing its target site, suggesting the function of miR156 is conservative in tobacco and Arabidopsis.