Arterial pressure, end-tidal carbon dioxide, and central venous oxygen saturation in reflecting compression depth.

BACKGROUND: We sought to investigate the utility of arterial pressure, end-tidal carbon dioxide (ETCO2 ), and central venous oxygen saturation (SCVO2 ) to guide compression depth adjustment. Thus, in a pig model of cardiac arrest, we observed these parameters during cardiopulmonary resuscitation (CPR) with optimal and suboptimal compression depths. METHODS: Sixteen pigs underwent three experimental sessions after induction of ventricular fibrillation. First, the animals received two 4-min CPR trials with either optimal (20% of the anteroposterior diameter) or suboptimal (70% of the optimal depth) compression depth. Second, the animals received two 5-min CPR trials with optimal compression depth, in which adrenaline (0.02 mg/kg) or saline placebo was administered. Third, the animals randomly received compression with either optimal or suboptimal depth during advanced cardiovascular life support. RESULTS: The systolic arterial pressure reflected compression depth most accurately and immediately (area under the curve [AUC], 0.895-0.939 without adrenaline and 0.928-1.000 with adrenaline). Although the response of ETCO2 to the change in compression depth was 0.5 min slower than that of the systolic arterial pressure, the performance of ETCO2 was comparable with that of systolic arterial pressure. SCVO2 did not reflect compression depth. Adrenaline administration remarkably increased systolic arterial pressure, diastolic arterial pressure, and coronary perfusion pressure but did not affect the ETCO2 readings. CONCLUSION: In a pig model of cardiac arrest, systolic arterial pressure reflected compression depth immediately and accurately. The performance of ETCO2 was comparable with that of systolic arterial pressure. SCVO2 did not reflect compression depth.

Verification of endotracheal tube placement using electrical stimulation through electrodes placed on the endotracheal tube cuff.

BACKGROUND: Current methods for verification of endotracheal intubation can fail, particularly in emergency settings. We investigated whether a verification method using electrical stimulation through electrodes placed on the endotracheal tube cuff could distinguish endotracheal and esophageal intubations in an experimental setting. METHODS: During three sequential sessions simulating emergency intubation without paralysis, rapid sequence intubation (RSI) with neuromuscular blockade, and intubation during cardiopulmonary resuscitation, eight pigs were intubated with an endotracheal tube fitted with two electrodes exposed on the cuff of the tube, first in the esophagus and next in the trachea or in reverse sequence. Cuff pressure was monitored during a 5-s electrical stimulation (20 mA, 80 Hz, 500 µs), and delta pressure was calculated as the difference between baseline cuff pressure and maximum cuff pressure during the electrical stimulation. RESULTS: Delta pressure was significantly higher in esophageal than in tracheal placements in all three sequential sessions (86.0 [78.3-89.7] vs. 6.5 [2.0-7.9] mmHg, P = 0.001; 16.6 [13.2-22.8] vs. 0.8 [0.3-2.6] mmHg, P = 0.004; 66.1 [60.0-84.7] vs. 2.7 [0.7-9.7] mmHg, P = 0.001). The delta pressure did not overlap between tracheal and esophageal intubations except for the session simulating RSI with neuromuscular blockade, in which one of eight esophageal placements showed a delta pressure within the delta pressure range of tracheal placements. CONCLUSION: Electrical stimulation through electrodes placed on the endotracheal tube cuff produced remarkably greater increases in cuff pressure in esophageal intubations than in tracheal intubations in an experimental setting.

Sustained manual abdominal compression during cardiopulmonary resuscitation in a pig model: a preliminary investigation.

OBJECTIVES: The present study was undertaken to determine whether sustained manual abdominal compression (SMAC) using left paramedian compression technique can improve coronary perfusion pressure (CPP) during cardiopulmonary resuscitation (CPR) and resuscitation outcomes without causing liver laceration. METHODS: Ventricular fibrillation was induced in 14 pigs, and circulatory arrest was maintained for 6 min. Animals were resuscitated either by standard CPR (control group) or by standard CPR with SMAC (SMAC-CPR group). RESULTS: Mean blood pressure, aortic diastolic pressure and right atrial diastolic pressure in the SMAC-CPR group were significantly greater than in the control group throughout simulated basic life support. However, since the increases in aortic and right atrial diastolic pressures were similar, no significant intergroup difference was found in terms of CPP. Return of spontaneous circulation (ROSC) was attained in four of seven animals in the control group and in six of seven animals in the SMAC-CPR group (p = 0.55). Three animals in the control group and four in the SMAC-CPR group survived 24 h after ROSC (p = 1.00). Two of the seven animals in the SMAC-CPR group had a ruptured liver, but no such injury occurred in the control group. CONCLUSIONS: SMAC using left paramedian compression technique failed to improve CPP during CPR and resuscitation outcomes. Furthermore, this method could not avoid liver laceration.