Abstract
Unrecognized endobronchial intubation frequently occurs after emergency intubation. However, no study has evaluated the effect of one-lung ventilation on end-tidal carbon dioxide (ETCO2) during cardiopulmonary resuscitation (CPR). We compared the hemodynamic parameters, blood gases, and ETCO2 during one-lung ventilation with those during conventional two-lung ventilation in a pig model of CPR, to determine the effect of the former on ETCO2. A randomized crossover study was conducted in 12 pigs intubated with double-lumen endobronchial tube to achieve lung separation. During CPR, the animals underwent three 5-min ventilation trials based on a randomized crossover design: left-lung, right-lung, or two-lung ventilation. Arterial blood gases were measured at the end of each ventilation trial. Ventilation was provided using the same tidal volume throughout the ventilation trials. Comparison using generalized linear mixed model revealed no significant group effects with respect to aortic pressure, coronary perfusion pressure, and carotid blood flow; however, significant group effect in terms of ETCO2 was found (P < 0.001). In the post hoc analyses, ETCO2 was lower during the right-lung ventilation than during the two-lung (P = 0.006) or left-lung ventilation (P < 0.001). However, no difference in ETCO2 was detected between the left-lung and two-lung ventilations. The partial pressure of arterial carbon dioxide (PaCO2), partial pressure of arterial oxygen (PaO2), and oxygen saturation (SaO2) differed among the three types of ventilation (P = 0.003, P = 0.001, and P = 0.001, respectively). The post hoc analyses revealed a higher PaCO2, lower PaO2, and lower SaO2 during right-lung ventilation than during two-lung or left-lung ventilation. However, the levels of these blood gases did not differ between the left-lung and two-lung ventilations. In a pig model of CPR, ETCO2 was significantly lower during right-lung ventilation than during two-lung ventilation. However, interestingly, ETCO2 during left-lung ventilation was comparable to that during two-lung ventilation.
Highlights
Unrecognized endobronchial intubation frequently occurs following emergency intubation [1,2,3]
The post hoc analyses showed that the levels of these blood gases did not differ between the left-lung and two-lung ventilations
A significant difference in the PaCO2-ETCO2 gradient was observed between the three types of ventilation (P = 0.020)
Summary
Unrecognized endobronchial intubation frequently occurs following emergency intubation [1,2,3]. Chest radiograph remains one of the definitive means to detect endobronchial intubation This modality is not generally used during cardiopulmonary resuscitation (CPR) because obtaining chest radiograph inevitably requires chest compression interruption. End-tidal carbon dioxide (ETCO2) is a non-invasive measure of pulmonary perfusion during cardiac arrest. Ventilation through an endotracheal tube inadvertently placed into the main stem bronchus would cause a decrease and an increase in alveolar carbon dioxide in the intubated and contralateral lungs, respectively. ETCO2 would decrease following endobronchial intubation because capnography measures the partial pressure of carbon dioxide only in the intubated lung. Several studies performed in a non-arrest animal model reported a decrease in ETCO2 following one-lung ventilation achieved through endobronchial intubation or bronchial occlusion [15,16]. To our knowledge, no study has evaluated the effect of one-lung ventilation on ETCO2 during CPR
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