Efficacy of nocturnal nasal ventilation in patients with restrictive thoracic disease.

We tested the efficacy of nocturnal nasal ventilation (NNV) using the BIPAP ventilator in patients with restrictive thoracic diseases by withdrawing them from NNV for an average of 1 wk. One male and five female patients were enrolled in the study; four with restrictive chest wall diseases, and two with muscular dystrophies. All patients had chronic CO2 retention (PaCO2 greater than 50 mm Hg) and had been improved by using NNV for at least 2 months before the study. Four patients were switched to the BIPAP ventilator from standard portable volume ventilators at least 1 month prior to the study without changes in gas exchange or symptoms. After withdrawal of NNV, patients had no deterioration in daytime vital signs, pulmonary functions, maximal inspiratory or expiratory pressures, or arterial blood gases compared with measures made immediately before withdrawal and 1 wk after resumption. However, patients had more dyspnea at rest, increased daytime somnolence, more morning headaches, less daytime energy, and felt less rested in the morning during withdrawal of NNV. Furthermore, nocturnal monitoring demonstrated greater tachycardia, tachypnea, oxygen desaturation, and hypoventilation during withdrawal of NNV. We conclude that NNV administered by the BIPAP ventilator is effective in ameliorating nocturnal hypoventilation and daytime symptoms in patients with chronic CO2 retention caused by severe restrictive thoracic diseases. These data also suggest that the efficacy of NNV may depend more on amelioration of nocturnal hypoventilation than on resting of ventilatory muscles.

The evolution of a clinically relevant experimental model for the realistic evaluation of long-length (80-cm) arterial prostheses.

A new carotid-femoral experimental model has been developed which has significant clinical relevance to human limb salvage bypass grafting in the areas of graft length, hemodynamics and tissue environment. More significantly, the graft healing pattern observed with this model is similar to what is seen in humans. Therefore, this experimental model provides a challenging and critical site for dynamic healing studies and comparisons of different types of vascular prostheses.

Effect of healing on compliance of porous Dacron grafts.

The effects of tissue ingrowth on the compliance of porous Dacron grafts were studied in 8 mm external-velour warp-knit Dacron grafts implanted in the canine descending thoracic aorta. The compliance of these grafts was measured before implantation and after implant periods of two weeks and one, two, four, and six months. Compliance, which initially was 0.043 +/- 0.008% mm Hg, decreased less than 10% after implantation (no statistical difference at p less than 0.05). No anastomotic neointimal hyperplasia was observed. Although the total thickness of the graft wall increased two- to three-fold after implantation, the benign healing process observed in this study had very little influence on graft compliance followed to six months.

Differences in reendothelialization after balloon catheter removal of endothelial cells, superficial endarterectomy, and deep endarterectomy.

The process of reendothelialization was studied in a deendothelialized 3 cm segment of the canine descending thoracic aorta from which peripheral endothelial cell ingrowth had been prevented by impervious prosthetic graft sleeves. Three preparations were studied: (1) removal of only the endothelial cells, accomplished by flow surface drying and balloon catheter denudation, (2) removal of the superficial portion of the nonvasal media, accomplished by endarterectomy to a depth of 200 to 300 micron, and (3) removal of the entire inner (nonvasal) media, accomplished by endarterectomy to a depth of 500 to 600 micron to reach the outer (vasal) media. A total of 44 specimens were studied after implantation periods of 7, 14, 28, and 56 days. In all cases endothelial cell ingrowth from the host aorta into the test specimen was prevented by the impervious graft sleeves. In the deep endarterectomy group there were scattered areas of reendothelialization at 1 week, extensive reendothelialization at 2 weeks, almost complete reendothelialization at 4 weeks, and confluence by 8 weeks. However, in the superficial endarterectomy group scanning electron microscopy showed scattered areas of factor VIII/von Willebrand factor (FVIII/vWF)-negative, endothelial-like cells at 4 weeks, whereas at 8 weeks most of the surface was covered by endothelial cells identified by FVIII/vWF. In those specimens subjected to balloon catheter removal of endothelial cells only, reendothelialization was not seen, even at 8 weeks.

A rapid in vitro test of the in vivo healing potential of vascular prostheses.

An in vitro method for comparing the penetration of bovine fibroblasts seeded on the external surface of porous vascular prostheses was devised. The effects of water porosity reduction and differing manufacturing constructions (warp-knit Dacron, woven Dacron and polytetrafluoroethylene) on the ability of the bovine fibroblasts to penetrate transmurally was investigated. Of the warp-knit external-veloured Dacron prostheses, the highest porosity 140-denier prototype had the highest luminal surface cell count and the lowest porosty 280-denier prototype the lowest luminal surface cell count. The intermediate prototypes had values between these two extremes. The woven Dacron prostheses, which were of even lower porosity but with a much thinner wall, had cell counts midway between the 140-denier and the 280-denier prototypes. The microporous polytetrafluoroethylene prostheses did not allow fibroblast penetration despite adherence of cells to the outer surface. These findings agree with in vivo healing studies of the same materials in the descending thoracic aorta of the dog, demonstrating that this rapid in vitro assay method can help predict the healing potential of a vascular prosthesis.

A comparative experimental study of the organization of arterial and venous thrombi.

Organization of a venous thrombus proceeds much faster than that of an arterial thrombus. Two different double-ligation procedures were used for study of the time sequence of thrombus organization by the vascularized (in situ) and devascularized (dissected) walls of the external jugular vein and common carotid artery in 21 mongrel dogs. Blood in the ligated segments of the in situ veins remained mostly fluid. In these segments, intimal hyperplasia was observed after 4 weeks with apparent preservation of an endothelial lining. However, in the dissected veins, the trapped blood rapidly thrombosed. Remarkable cell proliferation quickly occurred in these dissected walls with rapid invasion of the thrombus to achieve complete organization by 4 weeks. In contrast, a thrombus formed in the ligated segments of all arteries, whether in situ or dissected, and organization was much slower, requiring about 4 months for completion. Full-wall viability was maintained in 100% of the in situ veins and in 95% of the devascularized veins, but inner wall viability was lost in 30% of the in situ arteries and in 95% of the devascularized arteries.

Carotid artery Dacron patch graft angioplasty: a ten-year experience.

Of 394 carotid endarterectomies performed during a 10-year period, 36 (9%) included Dacron patch graft angioplasties. Patch graft angioplasties were used selectively in patients because they had undergone previous carotid endarterectomy or had small-caliber vessels. There were no postoperative infections, occlusions, emboli, stroke, or pseudoaneurysms. In addition, no clinically detectable recurrent stenoses developed in this high-risk group of patients. Twenty-four of the 27 patients available for follow-up were screened for asymptomatic stenoses with spectral analysis and B-mode imaging; there was no sign of hemodynamically significant recurrent stenosis in this group. These encouraging results support the continued selective use of Dacron patch graft angioplasty in carotid surgery.