Relationship between arterial oxygen tension and mortality of patients in intensive care unit on mechanical ventilation support

BACKGROUND: Although there are studies demonstrating hyperoxia may be an independent risk factor for increased mortality and morbidity, this issue remains unclear. Our research then aimed to examine the relationship between arterial oxygen tension, arterial carbon dioxide tension, and in-hospital mortality of critically ill patients in intensive care unit (ICU).
METHODS: After obtaining ethics committee approval, we analyzed a retrospective data of patients over the age of 18 who survived at least 24 hours in the ICU on mechanical ventilatory support between year 2008 and 2012. The demographic properties, mechanical ventilation, and blood gas parameters were studied. We defined hyperoxia group as PaO2 value of ≥120 mmHg and normoxemia group as PaO2 of 60–120 mmHg. Patients with PaCO2 value <30 mmHg were determined to have hypocapnia, those with 30–50 mmHg normocapnia, and those with >50 mmHg hypercapnia.
RESULTS: Between 2008 and 2012, a total of 7689 patients were admitted to the ICU. Of 450 patients meeting the inclusion criteria of the study, 263 (58.4%) were male and 187 (41.6%) were female. Normoxia was observed in 232 (51.5%) patients and hyperoxia in 218 (48.5%) patients. The mean PaO2 was 16.2 kPa (121.50 mmHg), and FiO2 was 60%. 254 (56%) of the patients had died during the five-year period. There was no statistically significant difference in mortality between PaO2 levels and PCO2 levels (p>0.05). According to the classification of PaO2 and FiO2, there was no statistically significant difference in mortality (p>0.05) among patients. In addition, no statistically significant difference was found between the survival rates according to PCO2 classification (p=0.602, p>0.05).
CONCLUSION: There was no significant association between mortality and oxygen and carbon dioxide of patients in ICU on mechanical ventilatory support.

Yoðun bakým ünitesinde mekanik ventilatör desteði ile takip edilen hastalarda arteriyel oksijen basýncý ile mortalite arasýndaki iliþki

AMAÇ: Hiperoksinin yoðun bakým ünitelerinde mekanik ventilasyon desteði ile takip edilen hastalarda mortalite ve morbiditeyi artýran baðýmsýz bir risk faktörü olduðuna dair farklý çalýþmalar olmasýna raðmen bu konu belirsizliðini korumaktadýr.
GEREÇ VE YÖNTEM: Bu çalýþma, etik komite onayý alýndýktan sonra mekanik ventilatör desteði ile yoðun bakým ünitesine takip edilen 18 yaþ üzerindeki 7689 hastanýn ilk 24 saatteki verileri incelenerek yapýlan geriye dönük, gözlemsel bir çalýþmadýr. Hastalarýn demografik özellikleri, mekanik ventilasyon ve kan gazý parametleri analiz edildi. Hiperoksemiyi PaO2 ≥120 mmHg, normoksemiyi PaO2 60–120 mmHg olarak tanýmlandý. PaCO2 deðeri <30 mmHg olan hastalar hipokapnik, 30–50 mmHg olanlar normokapnik, >50 mmHg olanlar hiperkapnik olarak tanýmlandý.
BULGULAR: Hastalarýn yaþ ortalamasý 59.60±16.96 (daðýlým, 18–93) yýl idi. Ortalama PaO2 deðeri 16.2 kPa (121.50 mmHg) ve FiO2 deðeri %60 idi. Ýki yüz otuz iki hasta normoksi (%51.5) ve 218 hastada (%48.5) hiperoksi gözlendi. Hastalarýn mortalite oran %56 idi. PaO2 düzeyleri ve PCO2 düzeyleri ile mortalite arasýnda istatistiksel olarak anlamlý fark bulunmadý (p>0.05). PaO2 ve FiO2 sýnýflamasýna göre mortalitede istatistiksel olarak anlamlý fark yoktu (p>0.05). PCO2 sýnýflamasýna göre saðkalým oranlarý arasýnda istatistiksel olarak anlamlý fark bulunmadý (p=0.602, p>0.05).
TARTIÞMA: Yoðun bakým ünitesindeki mekanik ventilatör desteði ile takip edilen hastalarda oksijen ve karbondioksit deðerleri ile mortalite arasýnda anlamlý iliþki bulunmadý.