Predicting severe postoperative respiratory complications following abdominal wall reconstruction.

BACKGROUND: Patients undergoing abdominal wall reconstruction are at risk of developing major postoperative respiratory complications. The authors attempted to identify factors predictive of respiratory complications following abdominal wall reconstruction. METHODS: All patients who underwent complex abdominal wall reconstruction over a 2-year period were reviewed. The primary endpoint studied was severe respiratory complication, defined as respiratory insufficiency requiring intubation or transfer to a higher level of care. RESULTS: Sixty patients underwent complex abdominal wall reconstruction during the study period. The incidence of respiratory complications was 20 percent. Factors predictive of postoperative respiratory complication included age (p = 0.05), American Society of Anesthesiologists score (p = 0.04), and hernia defect size (p = 0.01). In addition, patients who developed respiratory complications were more likely to have had a greater change in plateau pressure (5.8 versus 2.3 cmH(2)O; p = 0.01). The greater the change in plateau pressure, the greater the risk of developing a respiratory complication: for a change in plateau pressure greater than or equal to 6 cmH(2)O, the odds ratio was 8.67; for a change in plateau pressure greater than or equal to 9 cmH(2)O, the odds ratio was 11.5. CONCLUSIONS: Respiratory complications following abdominal wall reconstruction can be serious and are associated with prolonged hospitalizations. Patients with an increase in their plateau pressure of greater than 6 cmH(2)O are at an increased risk of severe postoperative respiratory complications.

Integument pattern formation involves genetic and epigenetic controls: feather arrays simulated by digital hormone models.

Pattern formation is a fundamental morphogenetic process. Models based on genetic and epigenetic control have been proposed but remain controversial. Here we use feather morphogenesis for further evaluation. Adhesion molecules and/or signaling molecules were first expressed homogenously in feather tracts (restrictive mode, appear earlier) or directly in bud or inter-bud regions ( de novo mode, appear later). They either activate or inhibit bud formation, but paradoxically colocalize in the bud. Using feather bud reconstitution, we showed that completely dissociated cells can reform periodic patterns without reference to previous positional codes. The patterning process has the characteristics of being self-organizing, dynamic and plastic. The final pattern is an equilibrium state reached by competition, and the number and size of buds can be altered based on cell number and activator/inhibitor ratio, respectively. We developed a Digital Hormone Model which consists of (1) competent cells without identity that move randomly in a space, (2) extracellular signaling hormones which diffuse by a reaction-diffusion mechanism and activate or inhibit cell adhesion, and (3) cells which respond with topological stochastic actions manifested as changes in cell adhesion. Based on probability, the results are cell clusters arranged in dots or stripes. Thus genetic control provides combinational molecular information which defines the properties of the cells but not the final pattern. Epigenetic control governs interactions among cells and their environment based on physical-chemical rules (such as those described in the Digital Hormone Model). Complex integument patterning is the sum of these two components of control and that is why integument patterns are usually similar but non-identical. These principles may be shared by other pattern formation processes such as barb ridge formation, fingerprints, pigmentation patterning, etc. The Digital Hormone Model can also be applied to swarming robot navigation, reaching intelligent automata and representing a self-re-configurable type of control rather than a follow-the-instruction type of control.