Influence of altitude on cerebral and splanchnic oxygen saturation in critically ill children during air ambulance transport

OBJECTIVE: The aim of the current study was to investigate how cerebral and splanchnic oxygen saturation (rSO(2)-C and rSO(2)-A) in critically ill children transported in air ambulance was affected by flight with cabin pressurization corresponding to ≥ 5000 feet. A second aim was to investigate any differences between cyanotic and non-cyanotic children in relation to cerebral and splanchnic oxygen saturation during flight ≥ 5000 feet. The variability of the cerebral and splanchnic Near Infrared Spectroscopy (NIRS) sensors was evaluated. DESIGN: NIRS was used to measure rSO(2)-C and rSO(2)-A during transport of critically ill children in air ambulance. rSO(2) data was collected and stored by the NIRS monitor and extracted and analyzed off-line after the transport. Prior to evaluation of the NIRS signals all zero and floor-effect values were removed. SETTING: The Pediatric Intensive Care Unit (PICU) at Astrid Lindgren Children’s Hospital, Karolinska University Hospital in Stockholm, Sweden. PATIENTS: In total, 44 critically ill children scheduled for inter-hospital transport by a specialized pediatric transport team were included in the study between January 2014 and January 2019 (convenience sampling). INTERVENTION: No interventions were conducted. MEASUREMENTS: All study patients were monitored with a cerebral NIRS-sensor placed over the forehead and an abdominal NIRS-sensor placed in the infra-umbilical area for cerebral and splanchnic regional oxygen saturation monitoring, rSO(2)-C and rSO(2)-A, respectively. MAIN RESULTS: Complete rSO(2)-C and rSO(2)-A data was obtained in 39 patients. Median age was 12 days. Cyanotic congenital heart malformations were present in 9 patients (23%). In 22 patients (56%) rSO(2)-C decreased at altitude ≥ 5000 feet and in 24 patients (61%) rSO(2)-A decreased at altitude ≥ 5000 feet compared to baseline (p<0.0001). In 25 patients (64%) the rSO(2)-C/rSO(2)-A ratio was greater at altitude ≥ 5000 feet than at baseline. A ratio ≥ 1 was seen in 77% of patients at altitude ≥ 5000 feet compared to in 67% of patients at baseline. CONCLUSION: Both cerebral and splanchnic oxygen saturation decreased at altitude ≥ 5000 feet compared to baseline. In most patients, both cyanotic and non-cyanotic, cerebral oxygen saturation was preserved more than splanchnic oxygen saturation.