title: Nocturnal hypoxia and arterial lactate levels in sleep-related breathing disorders.
abstract: BACKGROUND
  Lactate may be useful in pointing out the higher risk subgroups in sleep-related breathing disorders (SRBD) with various patterns of hypoxemia. We aimed to search whether morning and night lactate levels are related to apnea-hypopnea, hypoventilation, and hypoxemia in patients with SRBD and to compare it with patients without SRBD (No-SRBD).
  
  
  METHODS
  Eighty patients with suspected SRBD underwent polysomnography (PSG) testing. SRBD patients had obstructive sleep apnea syndrome with or without sleep-related hypoventilation/hypoxemic conditions. Patients without SRBD were in the control group. Measurements included pulmonary function testing, PSG, analysis of arterial blood gases, and arterial lactate before and after PSG. Arterial lactate was compared with SRBD and No-SRBD patients.
  
  
  RESULTS
  Morning lactate was significantly higher in the SRBD group than the No-SRBD group (1.65 +/- 0.48 and 1.35 +/- 0.57 mmol/L, respectively) (P = 0.003). Lactate levels at night and the change overnight in lactate levels were not significantly different between groups. After an adjustment for age, gender, and body mass index, lactate levels before PSG were related to the apnea-hypopnea index (beta: 0.004, 95% CI: 0.000-0.008) and the rate of sleep-time spent under 90% oxygen saturation (T90%). The following morning lactate level was correlated with the T90% (beta: 0.005, 95% CI: 0.000-0.010). After an adjustment for lactate levels before PSG, lactate in the morning was correlated with T90% (beta: 0.004, 95% CI: 0.000-0.008).
  
  
  CONCLUSIONS
  As a marker of tissue hypoxia, arterial lactate may be used to assess the severity of SRBD.
authors.affiliation: Department of Sleep Disorders, Dr Suat Seren Chest Diseases and Chest Surgery Training and Research Hospital, Izmir, Turkey.
authors.forename: Zeynep Zeren
authors.initials: ZZ
authors.lastname: Ucar
authors.forename: Zuhre
authors.initials: Z
authors.lastname: Taymaz
authors.forename: Ahmet Emin
authors.initials: AE
authors.lastname: Erbaycu
authors.forename: Cenk
authors.initials: C
authors.lastname: Kirakli
authors.forename: Fevziye
authors.initials: F
authors.lastname: Tuksavul
authors.forename: Salih Zeki
authors.initials: SZ
authors.lastname: Guclu
mesh_terms: D000328:Adult; D001158:Arteries; D015415:Biomarkers / Q000097:blood; D001784:Blood Gas Analysis; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood*; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000175:diagnosis*
chemical_list: D015415:Biomarkers; D019344:Lactic Acid