The Role Of TST90% In Assessing Disease Severity In Patients With Obstructive OSAHS

Objective:obstructive sleep apnea syndrome（OSAHS）is a respiratory and sleep disorder caused by repeated pharyngeal collapse during sleep.It is one of the serious public health problems all over the world.At present,the diagnosis and treatment effect evaluation of OSAHS are mainly based on the clinical manifestations of patients,AHI in polysomnography and the lowest SaO₂ at night.However,AHI can only represent the frequency of apnea and hypopnea events during night sleep,and can not reflect the duration of apnea and hypopnea events or the decrease of blood oxygen saturation at night.The lowest SaO₂ at night can only reflect the instantaneous blood oxygen saturation,and can not truly reflect the degree of hypoxia in the whole night sleep process.Studies have shown that the average minimum SaO₂ of healthy adults during sleep is 90%.According to the characteristics of oxygen dissociation curve,when SaO₂ > 90%,the physiological function of body cells is not significantly affected.Therefore,SaO₂ < 90% is clinically used as the baseline value for evaluating hypoxic injury related to OSAHS.TST90% refers to the percentage of the accumulated time when the blood oxygen saturation（SaO₂）is less than 90% in the total sleep monitoring time during the whole night.Compared with sleep apnea hypopnea index AHI and the lowest blood oxygen saturation LSaO₂ at night,it can more accurately,intuitively and comprehensively reflect the degree of body hypoxia in patients with OSAHS during night sleep.In recent years,the role of TST90% in assessing the severity of nocturnal hypoxia in patients with OSAHS has attracted more and more scholars’ attention.Many studies suggest that TST90% should be used as an indicator of hypoxia in patients with OSAHS.This study mainly explores the role of TST90% in evaluating the degree of hypoxia in patients with sleep apnea syndrome,in order to provide a more reasonable method and basis for judging the severity of OSAHS.Methods:from September 2019 to March 2022,128 patients suspected of sleep apnea syndrome due to night snoring and daytime sleepiness were analyzed retrospectively.They were treated in the respiratory department of the Fourth Affiliated Hospital of Nanchang University.They completed PSG monitoring in the sleep monitoring laboratory.After querying the general clinical data and the completion of the examination,a total of 128 patients were included,According to the diagnostic criteria of OSAHS in the guidelines for the diagnosis and treatment of adult OSAHS in the 2015 guidelines for the diagnosis and treatment of obstructive sleep apnea hypopnea syndrome（Basic Edition）,patients were divided into simple snoring group（AHI < 5 times/h）,mild group（5 times/h ≤ AHI < 15 times/h）,moderate group（15times/h ≤ AHI < 30 times/h）and severe group（AHI ≥ 30 times/h）.The general clinical data of patients were collected,including gender,age,height,weight and so on.Before receiving polysomnography monitoring,all subjects scored their daytime sleepiness according to the Epworth Sleepiness Scale under the guidance of the experimenters.Embletta MPR PG polysomnography was used to monitor polysomnography for at least 7 hours at night,and the sleep apnea hypopnea index（AHI）,mean nocturnal oxygen saturation（MSaO₂）,minimum nocturnal oxygen saturation（LSaO₂）and the percentage of cumulative time with blood oxygen saturation less than 90% in the total monitoring time（TST90%）were recorded.Inclusion criteria: patients aged ≥18 years,sleep monitoring and recording time > 7hours,and SaO₂ effective test value accounts for more than 90% of the overnight test value.All patients are forbidden to drink alcohol,strong tea,coffee and other excitatory drinks 24 hours before monitoring;Sedative and sleeping drugs are prohibited within 1 month.Exclusion criteria: previous history of severe neuromuscular diseases;Suffering from serious medical diseases that can lead to hypoxemia（such as myocardial infarction,heart failure,chronic obstructive pulmonary disease,pulmonary embolism,pulmonary interstitial disease,renal insufficiency and shock）;Those who cannot cooperate.SPSS 26.0 software was used for statistical analysis of the data.The scores of age,BMI and ESS lethargy scale of each group were in line with the normal distribution.The data were expressed in X ± s,and one-way ANOVA was performed.The data with skewed distribution of AHI,TST90%,MSaO₂ and LSpO₂ among different groups were expressed in [M（QR）],and the rank sum test of multiple independent samples was performed.Spearman correlation analysis was used between the scores of AHI,TST90%,MSaO₂,LSaO₂ and ESS in different groups.P < 0.05 showed that the difference was statistically significant.Result:1.comparison of age and BMI between OSAHS group and healthy control group The average age of the healthy control group was（58.20 ± 12.27）years old,and the BMI was（23.43 ± 3.04）kg / m2;In mild OSAHS group,the average age was（57.14 ± 11.82）years old and BMI was（26.13 ± 3.30）kg / m2;The average age of moderate OSAHS group was（60.53 ± 16.88）years old and BMI was（25.37 ± 4.22）kg / m2;The mean age of severe OSAHS group was（51.19 ± 12.51）years old and BMI was（28.55 ± 4.74）kg / m2.The age and body mass index of the subjects in each group had very significant statistical differences（P < 0.05）.2.Comparison of respiratory and sleep parameters between OSAHS group and healthy control group There were significant differences in sleep apnea hypopnea index（AHI）,ESS sleepiness scale score,mean nocturnal oxygen saturation（MSaO₂）,minimum nocturnal oxygen saturation(（LSaO₂）and the percentage of time with blood oxygen saturation less than 90 in the total monitoring time（TST90%）among OSAHS groups（P < 0.01）.3.Correlation analysis between AHI,BMI,MSaO₂,LSaO₂,TST90% and ESS sleepiness scale scores The correlation between TST90%,AHI,MSaO₂,LSaO₂ and ESS sleepiness scale was analyzed.Spearman test showed that TST90% was positively correlated with AHI and ESS sleepiness scale（P < 0.01）.TST90% was negatively correlated with LSaO₂ and MSaO₂,which was statistically significant（P < 0.01）,indicating that TST90%,MSaO₂ and LSaO₂ were good indicators to evaluate the severity of OSAHS,of which TST90%（r=0.453,P < 0.001）was the best index,and the correlation between ESS sleepiness score and AHI was low（r = 0.537,P < 0.001）Conclusion:1.There are significant differences in BMI between different groups.The correlation coefficient between BMI and AHI is 0.519（P < 0.001）.Body mass ratio（BMI）is a good index to evaluate obesity.There is a correlation between the severity of OSAHS and obesity.2.There are significant differences in TST90% among different groups,and there is also a good correlation between TST90% and AHI index.TST90% can be used as an index to evaluate the hypoxia of OSAHS.3.TST90% also considered the duration and severity of hypoxia during sleep.The correlation between TST90% and ESS sleepiness scale score is higher than that between AHI and ESS sleepiness scale score,which can better represent the hypoxia of OSAHS patients during all night sleep.4.In clinical work,it is suggested that the severity of OSAHS can be judged more objectively and accurately based on AHI and LSaO₂ combined with TST90%Provide basis for patients to formulate personalized and reasonable treatment plan.