ContributorsGIW wrote and revised the manuscript in response to co-author comments. He finalized all the figures and tables, performed the literature search, and assisted with data interpretation. HJK critically reviewed the manuscript and made important suggestions to improve it. He assisted with data interpretation. IBA performed the data analysis, constructed the figures and tables, and made important suggestions to improve the manuscript. H-CK assisted with the data analysis and also reviewed the manuscript. GRC critically reviewed the manuscript and made important suggestions to improve it. He assisted with data interpretation. All other authors were given the opportunity to review the manuscript and make suggestions which GIW received, either revising the paper or providing explanations. All who are not deceased were involved with approval of the manuscript.

BACKGROUND:Cases of H1N1 and other pulmonary infections evolve to acute respiratory failure and death when co‐infections or lung injury predominate over the immune response, thus requiring early diagnosis to improve treatment.OBJECTIVE:To perform a detailed histopathological analysis of the open lung biopsy specimens from five patients with ARDS with confirmed H1N1.METHODS:Lung specimens underwent microbiologic analysis, and examination by optical and electron microscopy. Immunophenotyping was used to characterize macrophages, natural killer, T and B cells, and expression of cytokines and iNOS.RESULTS:The pathological features observed were necrotizing bronchiolitis, diffuse alveolar damage, alveolar hemorrhage and abnormal immune response. Ultrastructural analysis showed viral‐like particles in all cases.CONCLUSIONS:Viral‐like particles can be successfully demonstrated in lung tissue by ultrastructural examination, without confirmation of the virus by RT‐PCR on nasopharyngeal aspirates. Bronchioles and epithelium, rather than endothelium, are probably the primary target of infection, and diffuse alveolar damage the consequence of the effect of airways obliteration and dysfunction on innate immunity, suggesting that treatment should be focused on epithelial repair.

Ramicotomy is a surgical procedure, with less adverse effects than conventional sympathectomy, however, it was abandoned due to the high recurrence rate. Twenty-eight pigs underwent bilateral videothoracoscopic ramicotomy and were divided into five groups. The animals were sacrificed at 15th, 45th, 90th, 135th and 180th postoperative days (POD). The segments were removed and evaluated for macroscopic regeneration and histological analysis. The data were compared to the control group of 10 intact segments of the sympathetic. There was no macroscopic regeneration on the 15th POD, and present on 41.6% on the 180th POD (P<0.05). The Schwann cells presented a similar evolution in both rami beginning at the 45th POD, with a smaller count in the gray rami. The collagen and reticular fibers presented a negative correlation (r=-0.414; P<0.01). The deposition of the collagen fibers was greater in the gray rami with a peak deposition on the 135th POD and a diminishing rate in the 180th POD (P<0.05). Ramicotomy allows complete section of all rami communicantes of the sympathetic ganglia. The histological regeneration might be greater than the recurrence rates of clinical symptoms seen in a human being due to non-functional regenerations.

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