Analysis Of Influencing Factors Of CPAP In Patients With Obstructive Sleep Apnea Hypopnea Syndrome

Objective:The aim of this study was to analyze the factors affecting optimal value of CPAP,and to develop a predictive equation for determining the optimal value of CPAP in Chinese patients with obstructive sleep apnea hypopnea syndrome（OSAHS）,and compare it with the foreign classic predictive formula.Methods:In 419 Chinese patients with moderate to severe OSAHS（AHI>15#/h）from the Department of Respiratory Medicine of Tianjin Medical University General Hospital from March 2016 to August 2019,the optimal value of CPAP was determined by manual titration during polysomnography.An equation predicting the optimal pressure was derived from anthropometric and polysomnographic data.This equation was validated in another 107 Chinese patients with moderate to severe OSAHS in the same hospital from September 2019 to December 2019,and compared with the foreign classic predictive formula.Results:1.The majority of the participants were obese and severe OSAHS patients in both prediction and validation group.2.In prediction group,age was negatively correlated with CPAP（r=-0.133,p=0.006）,and the neck circumference,waist circumference,and body mass index were positively correlated with CPAP,with correlation coefficients of 0.315,0.297,and 0.320,respectively.In the PSG indicators,CPAP was positively correlated with Epworth sleepiness score,apnea hypopnea index,oxygen desaturation index,arousal index,apnea index,longest apnea time,mean apnea time,N1%and T90%;and negatively correlated with REM%,N3%,Min Sp O₂ and Mean Sp O₂.However,other indicators,such as hypopnea index,the longest hypopnea time,the mean hypopnea time and N2%had no correlation with CPAP（P>0.05）.3.The best equation to predict the optimal value of CPAP was:CPAPpred=7.581+0.020AHI+0.101BMI+0.015LAT-0.028Min Sp O₂（R²=27.2%,P<0.05）.4.Among the patients in the prediction group,the average pressure predicted by the formula of this study was in good agreement with the actual titration pressure.5.In validation group,1)The predictive pressure according to the equation in this study was correlated with actual titration pressure（r=0.706,p=0.000）;the predictive pressure obtained by the foreign classic formula also had a correlation with the actual titration pressure（r=0.643,p=0.000）.2)The average titration pressure was 11.0（3.0）cm H₂O,and the average predictive pressure according to the formula in this study was 10.3（2.0）cm H₂O,and the average predictive pressure obtained by the foreign classic formula was 7.4（2.2）cm H₂O.The actual titration pressure was similar with the predictive pressure according to the formula in this study,however,was significantly different from the predictive pressure obtained by foreign classic formula.3)The difference between the actual titration pressure and the predicted pressure of the formula in this study was between-5-5cm H₂O,which was normally distributed,and most of them was concentrated between-2-2cm H₂O;the difference between the actual titration pressure and the predicted pressure of foreign classic formula was distributed between-2-8cm H₂O,most of them was concentrated between 1-6cm H₂O.4)Compared with the predictive pressure obtained by the foreign classic formula,the predictive pressure according to the equation in this study was closer to actual titration pressure.5)The predictive pressure of the foreign classic formula was obviously lower than the actual titration pressure,the predictive pressure according to the formula in this study accorded with the actual titration pressure.Conclusions:1.Indicators related to CPAP in OSAHS patients include:age,neck circumference,waist circumference,body mass index,Epworth sleepiness score,apnea hypopnea index,oxygen desaturation index,arousal index,apnea index,the longest apnea time,the mean apnea time,REM%,N1%,N3%,Min Sp O₂,Mean Sp O₂and T90%.2.The main factors influencing CPAP include:apnea hypopnea index（AHI）,body mass index（BMI）,the longest apnea time（LAT）and Min Sp O₂.The prediction formula was as follows:CPAPpred=7.581+0.020*AHI+0.101*BMI+0.015*LAT-0.028*Min Sp O₂（R2=27.2%,P<0.05）.3.It was demonstrated that our new predictive formula based on AHI,BMI,LAT,and Min Sp O₂ was more useful in calculating the effective CPAP in Chinese patients with OSAHS,compared with foreign classic formula.However,prediction formula cannot replace manual titration.