nocturnal desaturations

[cindy-loftin]

   I recently had an overnight sleep study done with the following results : Standard polysomnogram... 50% of study was noted to be wakefulness. REM sleep not entered. 12% of sleep was in stage I, 20% in stage II, and 17% was noted to be delta sleep. No obstructive apneic or hypopneic events. Throughout the study, however, the patient had multiple desaturation events with SaO2 falling to a low of 79%. These desaturations were not associated with apneic events. Only 65% of the study had an SaO2 greater than 93%. 10% of the study had an SaO2 between 86-92%. The patient was studied for 5 hours and 53 minutes. During the recording she demonstrated 0 obstructive apneas, 0 central apneas, and 0 hypopneas. The average cardiac rate was 118. The low cardiac rate was 21 and the maximumwas 240. There were 169 desaturation events (4% below baseline, 3 seconds minimum). I am 7 months pregnant and don't know if this could be caused by pregnancy. My OB/GYN doesn't know what to think and my neurologist isn't sure either. Please let me know if this a common occurence during pregnancy or if I should get another neurologist or what. Any input would be greatly appreciated.
  Cynthia
Dear Cynthia:
Congradulations on your pregnancy.  The reason for the sleep study????  There is not much in the literature on the effects of pregnancy on sleep.  I am curious why you didn't go into REM sleep.  The average person has 4-5 cycles of REM and it usually takes about 60-90 minutes before you cycle into the first REM.  However, this can be seen in patients entering a sleep study room for the first time.  Anyway, the SaO2 falling to a low of 79% is actually not bad during sleep, given your circumstances.  You likely were sleeping either on your back or side in a horizontal position.  Since you have this mass (baby) in your abdomen area, the ability of your diaphragm to move is somewhat decreased and the ability to completely fill your lungs with air therefore decreases and with that you get lower oxygen saturations.  Since you were able to physiologically respond (no apnea or prolonged desaturation) your body is acting correctly.  The pulse-ox machine is only accurate within 2-4%, so a value of 79% could be 83 or
75%.  The variation in heart rate is like physiological, although 240 is alittle fast and 21 alittle slow.  During the day, when you take your heart rate, have you noticed it being real fast, or real slow?  I am betting, that if you have no history of heart rate irregularities that this is a response to the oxygen saturations changing.  What did the sleep expert whose sleep lab you did your sleep study say?  I would follow his/her advice.  Likely you have little to worry about, but I would make a few suggestions.  I would raise the head of the bed or sleep with two pillows under your head.  Once you deliver you baby, then I would revisit the sleep lab and confirm the results were due to pregnancy.  Best of luck with your new one when he or she comes.  Frankly, you will not sleep well for the next 17 or 18 years (sorry, just from experience).  
Sincerely,
CCF Neuro[P] MD