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DR. YOTIN CHINVARUN MD, PhD
Vice-president of Epilepsy Society of Thailand, Director of Comprehensive Epilepsy and Sleep Disorder Program, Phramongkutklao Hospital, Director of Sleep club, The Neurological society of Thailand
Interview with Dr. Yotin Chinvarun on prescribing fixed CPAP
What are the different ways of finding the right pressure to set on fixed CPAP for OSA patient?
CPAP Titration can be done at home using Auto CPAP (APAP) which is called APAP titration or at the Sleep Laboratory which is called manual titration.
Do you use auto CPAP for finding the right pressure of fixed CPAP? If yes, what is the trial period for auto CPAP before pressure is set on fixed CPAP?
Yes, we use auto CPAP for finding the right pressure of fixed CPAP, called APAP titration and usually we give a trial period of One week for APAP titration.
How do you determine the pressure to be set on fixed CPAP based on auto CPAP report?
In my practice I determine fixed CPAP pressure based on auto titration by identifying the minimal effective pressure level (reference pressure). This is referred to as P90(Philips Respironics)/P95(Resmed). I look at P90/P95 after one week trial of Auto CPAP and set P90/P95 as therapy pressure on fixed CPAP. Different devices may utilize di erent algorithms for monitoring respiratory events.
Does pressure requirements changes on fixed CPAP for OSA patient over period of time? What is the finding of the recent study in this regard?
Yes, pressure changes are necessary in the majority of patients several weeks after CPAP therapy initiation. Therefore, re-evaluation of therapy pressure is useful.
A prospectively study by Netzer NC etal., 2011, in 905 consecutive patients (740 men and 165 women) with SDB and therapeutic intervention with continuous positive airway pressure (CPAP)/bilevel PAP showed pressure change needed in 511 patients (58.2%). Pressure increase was more frequent than pressure reduction (41.7% vs. 11.7%).1
If patient is unable to tolerate starting fixed CPAP pressure, do you use RAMP function to help him adapt to starting pressure on fixed CPAP?
Yes. The RAMP function on CPAP allows a slow increase in airway pressure from a low setting to the prescribed pressure so that the patient can fall asleep at lower pressures.
What is the setting of RAMP pressure and RAMP time? Can respiratory events happen during RAMP time?
In our experience a short RAMP time may be better than a long one. Usually we can set RAMP pressure of 4cmH2O and RAMP time will depend upon sleep latency of the patient eg: if he/she takes 15 min to fall asleep, set RAMP time of 15min. In my experience, if patient falls asleep during RAMP time itself, then there is a possibility of respiratory events happening during RAMP time period.
If patient is unable to tolerate starting xed CPAP pressure, do you lower the xed CPAP pressure initially and then gradually increase it towards the therapy pressure to help patient adapt to xed CPAP pressure?
Yes, if patient is unable to tolerate starting xed CPAP pressure, we lower the xed CPAP pressure initially and then gradually increase it towards the therapy pressure to help patient adapt to xed CPAP pressure.
If answer to question-7 is yes, how long do you take to go back to therapy pressure?
I take 2-4 weeks to go back to therapy pressure after lowering the pressure. Eg: let us assume a patient is prescribed a xed CPAP at 10cmH2O and he/she cannot tolerate 10cmH2O. I will lower the pressure to 6cmH20 and call him after 1 week. If he can tolerate 6cmH2O, I will increase pressure by 1cmH2O and wait for one more week. The new pressure now is 7cmH2O. If he can tolerate 7cmH2O, I will increase pressure by 1cmH2O (New pressure is 8cmH2O) and wait for one week. If he/she can tolerate 8cmH2O, I will increase pressure by 1cmH2O (new pressure become 9cmH2O) and wait for one week. If patient can tolerate 9cmH2O, I will increase pressure by 1cmH2O (new pressure becomes 10cmH2O) and wait for one week for follow up.
References: 1. Netzer NC et al. Sleep Breath (2011) 15:107–112.
The prevalence of sleep disorders in Thai
The prevalence of sleep disorders in Thai children who underwent polysomnography at a tertiary-care hospital is very high. In restrospective, analysis of 166 pediatric sleep studies done in a tertiary care hospital in Thailand, OSA was the most common diagnosis with prevalence of 92.2%. the second most common diagnosis was Periodic Limb Movement Disorder with a prevalence of 20.6%.
Even in tropical climate area, CPAP adherence and quality of life appeared to improve when heated humidi cation was employed in subjects with moderate to severe OSA with nasopharyngeal symptoms post-split-night polysomnography. In a prospective randomized cross over study, 20 moderate to severe OSA patients were randomized to receive CPAP with and without humi dication and observed for 4 weeks and then crossed over. Informtion on CPAP adherence, quality of life assessed by the Functional Outcomes of Sleep Questionnaire, nasopharyngeal symptoms assessed by a modi ed XERO questionnaire, and bedroom ambient humidity and temperature data were obtained.
In 42 OSA induced hypertension patients, the appropriate cuto points of BMI and neck circumference for Thai STOP-BANG questionnaire were 25kg/m(2) and 36cm.
In a prospective cohort study in Thai pregnant women, pregnant women with a high risk of OSA as assessed by Berlin Questionnaire were at an increased risk of having Pre-Term Delivery, compare with pregnant women with a low risk of OSA.4
1. Veeravigrom M etal. Indian J Pediatr. 2016 May 26.
2. Soudorn C etal. Respir Care. 2016 May 24.
3. Pavarangkul T etal. Neurol Int. 2016 Apr 1;8(1):6104.
4. Na-Rungsri K etal. Sleep Breath. 2016 Apr 8.