title: The effect of sildenafil on sleep respiratory parameters and heart rate variability in obstructive sleep apnea.
abstract: OBJECTIVE
  To evaluate the magnitude of effects of sildenafil on respiratory parameters and heart rate variability (HRV) in slow wave sleep (SWS) and REM sleep of patients with severe obstructive sleep apnea (OSA).
  
  
  METHODS
  Thirteen male patients with untreated severe OSA (aged 43+/-10 years, body mass index of 26.7+/-1.9 kg/m(2)) were studied on two nights, one with sildenafil 50mg and one with a placebo, in a double-blind, randomized fashion. All-night polysomnography and HRV were simultaneously recorded. Short-term HRV measures were performed in apnea-free intervals. Respiratory parameters were separately assessed in non-REM and REM sleep and compared to total sleep time (TST). Short-term HRV analysis was conducted in samples with regular respiration obtained in SWS and REM sleep.
  
  
  RESULTS
  Comparing to placebo, during sildenafil night there was an increase in apnea-hypopnea index (AHI) in TST and also in non-REM and REM sleep. Increase in central AHI occurred in non-REM sleep; increase in obstructive AHI and decrease in oxyhemoglobin saturation occurred in both non-REM and REM sleep. Additionally, an increase in arousal index and in low/high frequency component of HRV ratio (LF/HF) was significant only in REM sleep. Correlation between sleep architecture and respiratory parameters were more frequent in non-REM sleep for placebo and in REM sleep for sildenafil.
  
  
  CONCLUSIONS
  In severe OSA, the use of sildenafil 50mg at bedtime plays a detrimental role on respiratory parameters in both non-REM and REM sleep, fragmentation in REM sleep, and a prolonged increase in LH/HF component of HRV after resumption of ventilation.
authors.affiliation: Department of Psychobiology, Universidade Federal de São Paulo, Brazil. christianen1@hotmail.com
authors.forename: Christiane
authors.initials: C
authors.lastname: Neves
authors.forename: Sérgio
authors.initials: S
authors.lastname: Tufik
authors.forename: Marina Ariza
authors.initials: MA
authors.lastname: Monteiro
authors.forename: Felipe
authors.initials: F
authors.lastname: Chediek
authors.forename: Fabio Freire
authors.initials: FF
authors.lastname: Jose
authors.forename: Suely
authors.initials: S
authors.lastname: Roizenblatt
mesh_terms: D000328:Adult; D000368:Aged; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D015716:Electrocardiography, Ambulatory; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000139:chemically induced / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010108:Oxyhemoglobins / Q000378:metabolism; D010879:Piperazines / Q000008:administration & dosage / Q000009:adverse effects*; D017286:Polysomnography / Q000187:drug effects*; D011687:Purines / Q000008:administration & dosage / Q000009:adverse effects; D000068677:Sildenafil Citrate; D020181:Sleep Apnea, Obstructive / Q000139:chemically induced* / Q000503:physiopathology; D012894:Sleep Stages / Q000187:drug effects* / Q000502:physiology; D012895:Sleep, REM / Q000187:drug effects* / Q000502:physiology; D013450:Sulfones / Q000008:administration & dosage / Q000009:adverse effects*; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D010108:Oxyhemoglobins; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate; D010100:Oxygen