Changes in dead space components during pressure-controlled inverse ratio ventilation: A secondary analysis of a randomized trial

Background We previously reported that there were no differences between the lung-protective actions of pressure-controlled inverse ratio ventilation and volume control ventilation based on the changes in serum cytokine levels. Dead space represents a ventilation-perfusion mismatch, and can enable us to understand the heterogeneity and elapsed time changes in ventilation-perfusion mismatch. Methods This study was a secondary analysis of a randomized controlled trial of patients who underwent robot-assisted laparoscopic radical prostatectomy. The inspiratory to expiratory ratio was adjusted individually by observing the expiratory flow-time wave in the pressure-controlled inverse ratio ventilation group (n = 14) and was set to 1:2 in the volume-control ventilation group (n = 13). Using volumetric capnography, the physiological dead space was divided into three dead space components: airway, alveolar, and shunt dead space. The influence of pressure-controlled inverse ratio ventilation and time factor on the changes in each dead space component rate was analyzed using the Mann-Whitney U test and Wilcoxon’s signed rank test. Results The physiological dead space and shunt dead space rate were decreased in the pressure-controlled inverse ratio ventilation group compared with those in the volume control ventilation group (p < 0.001 and p = 0.003, respectively), and both dead space rates increased with time in both groups. The airway dead space rate increased with time, but the difference between the groups was not significant. There were no significant changes in the alveolar dead space rate. Conclusions Pressure-controlled inverse ratio ventilation reduced the physiological dead space rate, suggesting an improvement in the total ventilation/perfusion mismatch due to improved inflation of the alveoli affected by heterogeneous expansion disorder without hyperinflation of the normal alveoli. However, the shunt dead space rate increased with time, suggesting that atelectasis developed with time in both groups.

Verwendung differenzierter Beatmungsstrategien in der präklinischen Notfallmedizin in der Bundesrepublik Deutschland

Zusammenfassung Ziel der Studie Die vorliegende Arbeit untersucht den präklinischen Einsatz differenzierter Beatmungsstrategien in Deutschland. Methodik Onlinebefragung deutscher Notärzte nach Verfügbarkeit moderner Respiratoren, regelhaft verwendeten Beatmungseinstellungen, Monitoring und Zielparametern der Ventilation. Ergebnisse Die Verfügbarkeit moderner Notfallrespiratoren betrug 95%. Regelhafte Abweichungen von den Leitlinien zur Beatmung wurden von 68% angegeben und betrafen positiven endexspiratorischer Druck (19%), Tidalvolumen (13%), Spitzendruck (3%) Atemfrequenz (2%). 90% verwendeten regelmäßig die Kapnografie. 82% steuerten den inspiratorischen Sauerstoffgehalt anhand der Sauerstoffsättigung. Eine Inverse-Ratio-Ventilation wurde regelmäßig von 9% verwendet. Schlussfolgerung Abweichungen von leitliniengerechten Beatmungseinstellungen und -Monitoring sind häufig. Die aus der Intensivmedizin stammenden Empfehlungen sollten präklinisch auf Anwendbarkeit evaluiert und ggf. adaptiert werden.

Inverse Ratio Ventilation for Preventing Intra-Operative Hypercapnia in Children Undergoing Laparoscopic Surgery

BackgroundHigh end-tidal carbon dioxide tension (PETCO2) and respiratory acidosis occurs frequently in patients undergoing laparoscopic surgery. The aim of this study is to be investigate the effect of pressure-controlled inverse ratio ventilation (IRV) with inspiratory to expiratory ratio (I: E) of 2:1 on children undergoing laparoscopic surgery. MethodsEighty children undergoing elective laparoscopic surgery were allocated randomly to the IRV group (1: E=2:1) and the control group (I: E=1:2). Children received pressure-controlled ventilation with I: E ratio of 2:1 or 1:2. Hemodynamic parameters and respiratory mechanics were recorded. Side effects were also recorded. ResultsAt 30 min after CO2 pneumoperitoneum, tidal volume (Vt) and arterial partial pressure of oxygen (PaO2) were greater in the IRV group than the control group (100.6 ± 6.6 vs. 95.1±7.9 ml, 282.7 ± 45.6 vs.246.5 ± 40.1mmHg, respectively) (P < 0.01), but PaCO2 was lower than the control group (43.9 ± 5.45 vs. 46.7 ± 4.90 mmHg, P = 0.013). The incidence of intra-operative hypercapnia was lower in the IRV group (25% vs. 42.5%, P= 0.03). ConclusionIRV may reduce the incidence of intra-operative hypercapnia as well as increasing Vt and thus improving CO2 elimination in children undergoing laparoscopy. (Registration number: ChiCTR2000035589)