Effects Of MAD On NO In Plasma And Small Pulmonary Arteries Of OSAHS Rabbits

Objective: Through the animal model of obstructive sleep apnea-hypopnea syndrome(OSAHS) established, the effects of OSAHS and treatment of mandibular advancement device(MAD) on nitric oxied (NO)in plasma and small pulmonary vessels were observed. This experiment provided theoretical test basis for clinical using MAD to treat OSAHS and to prevent damages of the small pulmonary arteries.Method: Thirty male New Zealand rabbits were divided into three groups at random: group OSAHS, group MAD and control group. 1% sodium pentobarbital was injected into group OSAHS and MAD. One to two milliliters mixed colloid was injected into muscularis mucosa of soft palate which was 0.5 centimeter to the boundary of soft and hard palate. The gel was stopped injecting until the subjects showed obvious snoring and apnea. The cephalometrical data of supine position showed the upper airway width of 1/4 point, middle point and 3/4 point of soft palate were significantly decreased compared with control group. Blood gas analysis showed that blood oxygen saturation decreased by 22% after model established. Those demonstrated that animal model had been established successfully. Then group MAD were worn mandibular advanced device.After the animal model established successfully, each group was given 10% chloral hydrate(5~6ml/kg) through oral cavity and slept 4~6 hours in a supine position everyday. On the second day, cephalometrical data and blood gas analysis of three groups were conducted again during sleep. After 8 weeks, three groups of animals were anaesthetized the with 1% pentobarbital sodium. Two milliliters blood was drawn from the ear vein to make analysis the amount of NO in plasma using Griess reaction assay.Under the same anesthetic states, lung tissues were obtained and perfused by 3.3% neutral formaldehyde buffer fluid. Then the trachea was ligated and the organs were immersed in the same solution over 48h. When fixation was completed, one block of tissue was taken from hilus pulmonis in transverse section and embedded in paraffin wax. Sections were cut and stained with HE and Elastic Van Gieson(EVG). Then sections were observed under Nikon ECLIPSE 80i microscope. The sections were analyzed under Motic Digilab version1.2 image analytical system to get the percentage wall thickness(WT%) of muscular pulmonary arteries and percentage of arterioles . At the same time, soft palate tissues of injection site were obtained and fixed in 3.3% neutral formaldehyde buffer fluid. Then its histological structures were observed under HE stained.All test figures were analyzed by SPSS 13.0 statistical software. Standard of significance test wasα<0.05.Results:1 General conditions:When sleeping, animals of group OSAHS had obvious snore and waked several times. Some of them had limbs symptoms. Animals of group MAD breathed less smoothly and had light snore. Animals of control group breathed regularly and smoothly.2 Cephalometrical analysis of the upper airway width in supine position: the upper airway width of 1/4 point, middle point and 3/4 point of soft palate in group OSAHS were 2.66±1.04mm, 2.26±0.79mm, 2.29±0.73mm. Compared with those of group MAD and control group, the upper airway width significantly decreased (P<0.05). While the upper airway width of group MAD decreased than those of control group with no significant difference(P>0.05).3 Blood gas analysis: blood oxygen saturation, arterial partial pressure of oxygen and PH values of group OSAHS were 69.43±1.66%, 72.40±2.53mmHg, 7.25±0.13, which reduced obviously than those of group MAD and control group(P<0.05).While partial pressure of carbon dioxide of OSAHS was 53.32±2.57mmHg, which was higher than those of group MAD and control group(P<0.05).There was no significant differences between group MAD and control group(P>0.05).4 Histological observation of injection tissue: there was a white bump in middle edge of the soft palate. A transparent and thin envelope surrounded it and the injection tissue was flexible. Observing under a light microscope, polyacrylamide hydrogel was stained to violet and surrounded by collagen fibers and elastic fibers which were distinguished from other tissues around. There was no inflamation and infiltration phenomenon.5 Measurements of NO in plasma: The amount of NO in plasma of group OSAHS, group MAD and control group were 52.28±0.38μmol/L, 65.16±0.53μmol/L, 66.17±0.60μmol/L. Compared with those in group MAD and control group, the content of NO in group OSAHS decreased significantly(P<0.05).The content of NO in group MAD was slightly lower than control group(P>0.05).6 The histological observation of small pulmonary arteries :6.1 Muscular pulmonary arteries(40μm≤d≤150μm): The microscopic examination by HE stain showed that the vessel wall of group OSAHS was thick and the lumen was narrow obviously. The vessel wall in group MAD was somewhat thicker than control group. But it was not obvious. The vessel wall of control group was thin and the lumen was large. Compared with control group and group MAD, the microscopic examination by EVG showed that the medial thickness of group OSAHS increased significantly. The medial thickness in group MAD was somewhat thicker than the control group. The medial thickness of control group was normal.6.2 Arterioles(d≤40μm): Differences could not be distinguished by HE stain. The microscopic examination by EVG showed that the arterioles in group OSAHS showed a thick media of circularly smooth muscle cells between internal and external elastic laminae. The arterioles in MAD group which consisted only of single elastic laminae were similar to those of control group.7 Measurements of percentage wall thickness(WT%)of the muscular pulmonary arteries: WT% in group OSAHS, group MAD and control group was 13.07±0.56%, 9.05±0.36%, 8.62±0.46%. WT% in group OSAHS was significantly higher than those of group MAD and control group(P<0.05). WT% in group MAD was increased a little than in control group(P>0.05). 8 Measurements of percentages of arterioles: In group OSAHS, group MAD, control group, the percentages of fully muscularised and partially muscularised arteries in three types of arterioles were 22.56%, 8.75%, 7.64%. The percentages in group OSAHS were higher than those of group MAD and control group(P<0.05). There were no statistical differences between group MAD and control group(P>0.05).Conclusions: NO in group OSAHS was increased and damage of small pulmonary arteries was prevented in treatment OSAHS by MAD.