- Hyperoxia reversibly alters oxygen consumption and metabolism (2012)
- AIM: Ventilation with pure oxygen (hyperoxic ventilation: HV) is thought to decrease whole body oxygen consumption (VO(2)). However, the validity and impact of this phenomenon remain ambiguous; until now, under hyperoxic conditions, VO(2) has only been determined by the reverse Fick principle, a method with inherent methodological problems. The goal of this study was to determine changes of VO(2), carbon dioxide production (VCO(2)), and the respiratory quotient (RQ) during normoxic and hyperoxic ventilation, using a metabolic monitor. METHODS: After providing signed informed consent and institutional acceptance, 14 healthy volunteers were asked to sequentially breathe room air, pure oxygen, and room air again. VO(2), VCO(2), RQ, and energy expenditure (EE) were determined by indirect calorimetry using a modified metabolic monitor during HV. RESULTS: HV reduced VO(2) from 3.4 (3.0/4.0) mL/kg/min to 2.8 (2.5/3.6) mL/kg/min (P < 0.05), whereas VCO(2) remained constant (3.0 [2.6/3.6] mL/kg/min versus 3.0 [2.6/3.5] mL/kg/min, n.s.). After onset of HV, RQ increased from 0.9 (0.8/0.9) to 1.1 (1.0/1.1). Most changes during HV were immediately reversed during subsequent normoxic ventilation. CONCLUSION: HV not only reduces VO(2), but also increases the respiratory quotient. This might be interpreted as an indicator of the substantial metabolic changes induced by HV. However, the impact of this phenomenon requires further study.
- Superimposed high-frequency jet ventilation combined with continuous positive airway pressure/assisted spontaneous breathing improves oxygenation in patients with H1N1-associated ARDS (2012)
- Background: Numerous cases of swine-origin 2009 H1N1 influenza A virus (H1N1)-associated acute respiratory distress syndrome (ARDS) bridged by extracorporeal membrane oxygenation (ECMO) therapy have been reported; however, complication rates are high. We present our experience with H1N1-associated ARDS and successful bridging of lung function using superimposed high-frequency jet ventilation (SHFJV) in combination with continuous positive airway pressure/assisted spontaneous breathing (CPAP/ASB). Methods: We admitted five patients with H1N1 infection and ARDS to our intensive care unit. Although all patients required pure oxygen and controlled ventilation, oxygenation was insufficient. We applied SHFJV/CPAP/ASB to improve oxygenation. Results: Initial PaO2/FiO2 ratio prior SHFJV was 58-79 mmHg. In all patients, successful oxygenation was achieved by SHFJV (PaO2/FiO2 ratio 105-306 mmHg within 24 h). Spontaneous breathing was set during first hours after admission. SHFJV could be stopped after 39, 40, 72, 100, or 240 h. Concomitant pulmonary herpes simplex virus (HSV) infection was observed in all patients. Two patients were successfully discharged. The other three patients relapsed and died within 7 weeks mainly due to combined HSV infection and in two cases reoccurring H1N1 infection. Conclusions: SHFJV represents an alternative to bridge lung function successfully and improve oxygenation in the critically ill.