Development of the obstetric unanticipated difficult video-laryngoscopy algorithm through a quality improvement randomized open-label in situ simulation study.

BACKGROUND: Video-laryngoscopy is increasingly used during general anesthesia for emergency cesarean deliveries. Given the heightened risk of difficult tracheal intubation in obstetrics, addressing challenges in airway management is crucial. In this simulation study, we hypothesized that using a flexible bronchoscope would lead to securing the airway faster than the Eschmann introducer when either device is used in addition to video-laryngoscopy. METHODS: Twenty-eight anesthesia trainees (n=14/group) were randomized to use either one of the rescue devices and video-recorded in a simulated scenario of emergency cesarean delivery. The primary outcome was the time difference in establishing intubation; secondary outcomes were the differences in incidence of hypoxemia, need for bag and mask ventilation, and failed intubation between the two rescue devices. RESULTS: Mean (±SD) time to intubation using flexible bronchoscopy was shorter compared to using an Eschmann introducer (24 ±â€¯10 vs 86 ±â€¯35 s; P<0.0001; difference in mean 62 seconds, 95% CI 42 to 82 seconds). In the fiberoptic bronchoscopy group, there were no episodes of hypoxemia or need for bag and mask ventilation; in contrast both such events occurred frequently in the Eschmann introducer group (71%, 10/14); P=0.0002). All flexible bronchoscopy-aided intubations were established on the first attempt. The incidence of failed intubation was similar in both groups. CONCLUSIONS: Our data from simulated emergency tracheal intubation suggest that flexible bronchoscopy combined with video-laryngoscopy results in faster intubation time than using an Eschmann introducer combined with video-laryngoscopy.

Role of cosyntropin in the management of postpartum post-dural puncture headache: a two-center retrospective cohort study.

BACKGROUND: Research suggests that postpartum post-dural puncture headache (PDPH) might be prevented or treated by administering intravenous cosyntropin. METHODS: In this retrospective cohort study, we questioned whether prophylactic (1 mg) and therapeutic (7 µg/kg) intravenous cosyntropin following unintentional dural puncture (UDP) was effective in decreasing the incidence of PDPH and therapeutic epidural blood patch (EBP) after birth. Two tertiary-care American university hospitals collected data from November 1999 to May 2017. Two hundred and fifty-three postpartum patients who experienced an UDP were analyzed. In one institution 32 patients were exposed to and 32 patients were not given prophylactic cosyntropin; in the other institution, once PDPH developed, 36 patients were given and 153 patients were not given therapeutic cosyntropin. The primary outcome for the prophylactic cosyntropin analysis was the incidence of PDPH and for the therapeutic cosyntropin analysis in exposed vs. unexposed patients, the receipt of an EBP. The secondary outcome for the prophylactic cosyntropin groups was the receipt of an EBP. RESULTS: In the prophylactic cosyntropin analysis no significant difference was found in the risk of PDPH between those exposed to cosyntropin (19/32, 59%) and unexposed patients (17/32, 53%; odds ratio (OR) 1.37, 95% CI 0.48 to 3.98, P = 0.56), or in the incidence of EBP between exposed (12/32, 38%) and unexposed patients (6/32, 19%; OR 2.6, 95% CI 0.83 to 8.13, P = 0.095). In the therapeutic cosyntropin analysis, in patients exposed to cosyntropin the incidence of EBP was significantly higher (20/36, 56% vs. 43/153, 28%; OR 3.20, 95% CI 1.52 to 6.74, P = 0.002). CONCLUSIONS: Our data show no benefits from the use of cosyntropin for preventing or treating postpartum PDPH.

A comparison of fentanyl, sufentanil, and remifentanil for fast-track cardiac anesthesia.

UNLABELLED: Cardiac surgery is estimated to cost $27 billion annually in the United States. In an attempt to decrease the costs of cardiac surgery, fast-track programs have become popular. The purpose of this study was to compare the effects of three different opioid techniques for cardiac surgery on postoperative pain, time to extubation, time to intensive care unit discharge, time to hospital discharge, and cost. Ninety adult patients undergoing cardiac surgery were randomized to a fentanyl-based, sufentanil-based, or remifentanil-based anesthetic. Postoperative pain was measured at 30 min after extubation and at 6:30 AM on the first postoperative day. Pain scores at both times were similar in all three groups (P > 0.05). Median ventilator times of 167, 285, and 234 min (P > 0.05), intensive care unit stays of 18.8, 19.8, and 21.5 h (P > 0.05), and hospital stays of 5, 5, and 5 days (P > 0.05) for the Fentanyl, Sufentanil, and Remifentanil groups did not differ. Three patients needed to be tracheally reintubated: two in the Sufentanil group and one in the Fentanyl group. Median anesthetic costs were largest in the Remifentanil group ($140.54 [$113.54-$179.29]) and smallest in the Fentanyl group ($43.33 [$39.36-$56.48]) (P < or = 0.01), but hospital costs were similar in the three groups: $7841 (Fentanyl), $5943 (Sufentanil), and $6286 (Remifentanil) (P > 0.05). We conclude that the more expensive but shorter-acting opioids, sufentanil and remifentanil, produced equally rapid extubation, similar stays, and similar costs to fentanyl, indicating that any of these opioids can be recommended for fast-track cardiac surgery. IMPLICATIONS: To conserve resources for cardiac surgery, fentanyl-, sufentanil-, and remifentanil-based anesthetics were compared for duration of mechanical ventilation, intensive care unit length of stay, hospital length of stay, and cost. The shorter-acting anesthetics, sufentanil and remifentanil, produced equally rapid extubation, similar stays, and similar costs to fentanyl; thus, any of these opioids can be recommended for fast-track cardiac surgery.

Effects of body size on operative, intermediate, and long-term outcomes after coronary artery bypass operation.

BACKGROUND: To investigate the role of body size, if any, on operative and longer term outcomes following coronary artery surgery. METHODS: A total of 3,560 consecutive patients undergoing coronary artery bypass grafting from 1991 to 1997, including 2,401 (67%) males and a mean +/- SD age of 63 +/- 10 years were ranked based on their body mass index (BMI). The association in these patients of preoperative, long-term, and economic data with variations in BMI were studied using regression analyses. Long-term survival was studied using 5-year Kaplan-Meier survival analysis. RESULTS: Operative mortality, myocardial infarction, cerebrovascular accidents, blood transfusions, and length of hospital stay were all increased in the smallest patients (BMI < or = 24 kg/m2). Obesity did not increase adverse operative outcomes except for a greater rate of sternal wound infections occurring with increasing severity of obesity. Direct variable costs were lowest in patients clustered around normal BMI, with cost increasing similarly at low and high extremes. This effect was correlated with similar BMI effects on ventilatory and intensive care requirements. Excluding operative mortality, 5-year survival trends were similarly worse for the smallest (BMI < or = 24) and most severely obese (BMI > 34) patients. Mild obesity (BMI > or = 30 to BMI < 34) did not affect long-term survival. CONCLUSIONS: Among study patients, immediate operative outcomes were adversely affected by small body size, which reflected older age (66 +/- 10 years) and an exaggerated adverse impact of cardiopulmonary bypass. Younger age and smaller effects of cardiopulmonary bypass lead to better operative outcomes in the obese. Long-term outcomes were, however, suboptimal in severely obese patients although that group was the youngest (60 +/- 10 years). In addition to their large body habitus, other factors, including substantial prevalence of diabetes, insulin dependence and hypertension, probably played a significant role in the poor long-term outcome in the severely obese.

Tension pneumothorax and contralateral presumed pneumothorax from endobronchial intubation via cricothyroidotomy.

Cricothyroidotomy can be a life-saving procedure for the "can't intubate, can't ventilate" patient who has upper-airway obstruction. The procedure is usually fast and easy to do; however, complications have been reported. We report two cases in which cricothyroidotomy with an endotracheal tube led to unrecognized endobronchial intubation, ipsilateral tension pneumothorax, contralateral presumed pneumothorax, and unnecessary emergency surgery. Additionally, these led to the triad of hypotension, hypoxemia, and, probably, elevated intracranial pressure, which can worsen cerebral injury. We discuss methods to avoid these complications.

Patient perception of monetary value to avoiding unpleasant side effects of anesthesia and surgery.

STUDY OBJECTIVES: To determine which monetary value patients place on decreasing or eliminating common side effects of anesthesia and surgery. DESIGN: Prospective questionnaire with visual analog scales. SETTING: Preoperative holding area of a tertiary care hospital. PATIENTS: 60 adult patients scheduled for general anesthesia. INTERVENTIONS: None. MEASUREMENTS: Patients' perception of problems with previous general anesthetics and surgery and their concerns about the approaching surgery and anesthesia were recorded. Amounts (in US Dollars) that patients would be willing to pay to decrease by half or to eliminate nausea, emesis, sore throat, headache, and pain were also noted. RESULTS: 95% of the patients had previously undergone a general anesthetic, most without any problems. However, 47% of patients reported at least one problem with a previous general anesthetic, 33% had one or more concerns with the upcoming general anesthetic, and 32% would be willing to pay to decrease or eliminate one or more of these side effects. Patients who were willing to pay were more likely to have had problems or have concerns about side effects. CONCLUSIONS: Some patients would be willing to pay extra to avoid unpleasant side effects. This information can be used in quality and satisfaction surveys to justify to hospitals and payors the use of higher quality but more expensive anesthetic drugs.

Oxygen consumption, carbon dioxide production and lactic acid during normothermic cardiopulmonary bypass.

The objective of this study was to measure oxygen consumption, carbon dioxide production and lactic acid levels during normothermic cardiopulmonary bypass. A prospective study was undertaken in a tertiary care community hospital, involving 20 adults undergoing cardiopulmonary bypass with prolonged (>65 min) crossclamping of the aorta. O2 consumption, CO2 production, hemoglobin and lactic acid levels were measured 5, 35 and 65 min after crossclamping of the aorta. O2 consumption was 79.7 +/- 14.5, 78.8 +/- 15.4 and 81.5 +/- 14.1 ml/min/m2 at 5, 35 and 65 min after crossclamping the aorta. CO2 production was 61.8 +/- 42.9, 60.6 +/- 26.3 and 62.2 +/- 35.9 ml/min/m2 at the same times. Lactic acid levels were 1.6 +/- 0.5 mM/dl at all three times and did not correlate with O2 consumption or CO2 production. In conclusion, although oxygen consumption was low, there was no evidence of abnormal lactate or anaerobic metabolism to suggest tissue ischemia.

Predictors of gastrointestinal complications in cardiac surgery.

Gastrointestinal problems are infrequent but serious complications of cardiac surgery, with high rates of morbidity and mortality. Predictors of these complications are not well developed, and the role of fundamental variables remains controversial. In a retrospective review of our cardiac surgery experience from July 1991 through December 1997 we found that postoperative gastrointestinal complications were diagnosed in 86 of 4,463 consecutive patients (1.9%). We categorized these 86 patients into 2 groups--Surgical and Medical--according to the method of treatment used for their complications. In the Medical group, 9 of 52 patients (17%) died; in the Surgical group, 17 of 34 (50%) died. By logistic multivariate analysis, we identified 8 parameters that predicted gastrointestinal complications: age greater than 70 years, duration of cardiopulmonary bypass, need for blood transfusions, reoperation, triple-vessel disease, New York Heart Association functional class IV, peripheral vascular disease, and congestive heart failure. Postoperative re-exploration for bleeding was a predictor specific to the Surgical group. Use of an intraaortic balloon pump was markedly higher in the Gastrointestinal group than in the Control group (30% vs 10%, respectively), as was the use of inotropic support in the immediate postoperative period (27% vs 5.6%). Our results suggest that intra-abdominal ischemic injury is a likely contributing factor in most gastrointestinal complications. In turn, the ischemia is probably caused by hypoperfusion due to low cardiac output, hypotension due to blood loss, and intra-abdominal atheroemboli. The derived models are useful for identifying patients whose risk of gastrointestinal complications after cardiac surgery may be reduced by clinical measures designed to counter these mechanisms.

Marginal cost of liberating ventilator-dependent patients after cardiac surgery in a stepdown unit.

BACKGROUND: With the recent changes in Medicare reimbursement for ventilator-dependent patients at skilled nursing facilities, hospitals may, by necessity, be required to liberate these patients from mechanical ventilation before discharge. This study sought to determine the marginal cost of liberating ventilator-dependent patients in a cardiac stepdown unit. METHODS: By retrospective analysis, the complete billing records of all 15 ventilator-dependent patients were obtained and abstracted for each item used. The drug or supply acquisition cost and direct variable cost of other items and labor were used to compute the daily and total marginal cost for each patient. RESULTS: Of 15 patients, 13 were discharged alive and liberated from mechanical ventilation. Length of stay was 28 +/- 23 days. Average per diem cost was $438.77 +/- 152.34. Costs were significantly higher in patients who required hemodialysis: $555.31 +/- 491.04 versus $380.54 +/- 272.25 (p < 0.01). CONCLUSIONS: Ventilator-dependent patients can be inexpensively liberated from mechanical ventilation in a stepdown unit.

Long-term survival and health status after prolonged mechanical ventilation after cardiac surgery.

OBJECTIVE: To determine hospital mortality, weaning from mechanical ventilation, long-term survival, and functional health status in patients receiving > or =7 days of mechanical ventilation after cardiac surgery. DESIGN: Retrospective chart review and prospective patient interviews. SETTING: A university-affiliated, tertiary care medical center. PATIENTS: A total of 124 patients that received > or =7 days of mechanical ventilation after cardiac surgery. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Hospital and long-term death, liberation from mechanical ventilation, and functional health status. MEASUREMENTS AND MAIN RESULTS: A total of 19 (15%) patients died in hospital. Of the 105 survivors, 104 (99%) were completely weaned from mechanical ventilation. Patients who died in the hospital were more likely to have had a preoperative stroke or to have a new postoperative stroke, more likely to have postoperative renal failure, and less likely to have chronic obstructive pulmonary disease. Kaplan-Meier survival was 59% at 5 yrs and expected median survival was 6.2 yrs. Patients who died anytime after discharge were more likely to have preoperative renal dysfunction or stroke, took longer to be weaned from mechanical ventilation and to be discharged, and were more likely to have postoperative complications such as stroke or renal dysfunction. Also, they were more likely to be too debilitated to walk or eat. By multivariate analysis, admitting creatinine, aortic valve surgery, number of ventilator days, and discharged on tube feedings remained significant predictors of mortality. A total of 40 of 53 survivors were interviewed. Participants were similar to nonparticipants (p > .10 for all characteristics). A few (16%) had limitations of their activities of daily living (eating, dressing, bathing), and most had limitations of moderate activity (60%) and vigorous activity (94%). Only 36% could climb stairs or walk uphill without limitations, 54% could walk a block, and 41% had no limitations in house or job work. Half the participants had no body pain; 38% had moderate and 4% severe pain. Most (59%) described their general health as good to excellent. Only 10% said it was poor. CONCLUSION: Patients' chances of being liberated from mechanical ventilation are excellent. Their long-term survival and health status are good.

Resource utilization in coronary artery bypass operation: does surgical risk predict cost?

BACKGROUND: Current healthcare trends may render financial risk of cardiac operation a key component of clinical decision making. It has been suggested, based on large cohorts of patients stratified by clinical risk, that the cost of operation can be predicted from models of clinical risk since length of stay (LOS) is highly correlated to clinical risk, and LOS is correlated to hospital costs and charges. Direct correlation of actual surgical costs with surgical risk are lacking. METHODS: Variable direct costs, LOS, and The Society of Thoracic Surgeons predicted mortality risk [STS risk (%)] were collected and analyzed in 628 consecutive patients undergoing coronary artery bypass grafting (CABG) at our institution in 1997. RESULTS: Cost of CABG had a near-normal distribution, and cost in 21 outlier patients (cost > two standard deviations above the mean) was an average 5.3 times normal (median cost). For individual patients, cost was well correlated to LOS (R2 = 0.48) but not with STS risk (R2 = 0.12). LOS was also poorly predicted by STS risk (R2 = 0.09). However, despite its poor prediction of cost, STS risk was an unbiased estimator over the entire population. A result manifested, when patients were grouped into similar risk (<1%, 1-2%, 2+ -3%, 3+ -5%, 5+ -10%, and >10%) cohorts, by high correlation between cost and STS risk (R2 = 0.99), cost and LOS risk (R2 = 0.99), and LOS and STS risk (R2 = 0.97). CONCLUSIONS: Our data demonstrated that, in large CABG cohorts, surgical risk models can accurately predict cost of CABG. However, despite a trend for increasing cost with increasing STS risk, surgical risk models based on preoperative data are poor predictors of cost in individual patients. Use of these models should be limited to analysis of cost trends in cardiac operation, but not for predicting financial risk in individual patients during clinical decision making.

Evaluation of the cuff-leak test in a cardiac surgery population.

OBJECTIVE: The purpose of this study is to determine the accuracy of the cuff-leak test in a cardiovascular ICU. METHODS: Five hundred twenty-four patients were tested immediately before being extubated 531 times. The cuff-leak test was performed with the ventilator set in assist-control mode at a tidal volume (VT) of 10 to 12 mL/kg. The leak was taken to be the difference between the preset inspiratory VT and the average of the three lowest of the subsequent six expiratory VTs. A leak

Variables predicting reintubation after cardiac surgical procedures.

BACKGROUND: This study sought to determine patient characteristics, processes of care, and intermediate outcomes as predictors of reintubation after cardiac surgical procedures. METHODS: We performed a retrospective case-control study that included all patients undergoing cardiac surgical intervention who required reintubation and an equal number of control patients not requiring reintubation. Putative risk factors were analyzed univariately by chi2, Fisher exact, Student's t, or Mann-Whitney tests. A logistic regression model was developed using data from patients requiring reintubation for cardiorespiratory reasons. RESULTS: Of the 1,000 consecutive patients reviewed, 41 (4.1%) required reintubation (30 [3%] for cardiorespiratory reasons and 11 [1.1] for unplanned operations). Univariate predictors of reintubation (p<0.05) were older age, chronic obstructive pulmonary disease, New York Heart Association functional class IV, preoperative renal failure, lower arterial oxygen tension, insertion of intraaortic balloon pump, longer time in the operating room, longer duration of cardiopulmonary bypass times, positive fluid balance, postoperative renal failure, and worse pulmonary mechanics. Patients requiring reintubation also required a longer initial period of mechanical ventilation (median, 16.3 versus 6.0 hours; p<0.05). Excellent prediction was found with a model consisting of four variables: operating room time, respiratory rate, vital capacity, and chronic obstructive pulmonary disease. CONCLUSIONS: Patients who required reintubation were sicker and had worse respiratory function and more comorbidity. Prompt extubation did not contribute to reintubation. Patients identified as having a high risk for reintubation should be followed up closely, and interventions should be directed to treating the problems leading to reintubation.

Approximate entropy of respiratory rate and tidal volume during weaning from mechanical ventilation.

OBJECTIVE: To determine the effects of respiratory failure on respiratory rate pattern and tidal volume pattern. DESIGN: Prospective, clinical study. SETTING: Cardiovascular intensive care unit. PATIENTS: Ten patients within 12 hrs of cardiac surgery, and 21 patients who required prolonged (>7 days) mechanical ventilation. INTERVENTIONS: Patients were placed on spontaneous ventilation for weaning trials. MEASUREMENTS AND MAIN RESULTS: During spontaneous ventilation, each breath's instantaneous respiratory rate and tidal volume were recorded for later analysis. Approximate entropy (ApEn) was calculated for respiratory rate and tidal volume series of the terminal 1000 breaths on each spontaneous ventilation trial in series of 100, 300, and 1000 breaths. Ten patients (controls) were studied and extubated within 12 hrs of cardiac surgery. The other 21 patients were studied during attempts to wean them from mechanical ventilation. These patients passed (Group V-Pass) 59 and failed (Group V-Fail) 14 weaning trials. Mean tidal volume did not vary between groups, but respiratory rate increased progressively from the control group to Group V-Pass to Group V-Fail (p < .017). Conversely, approximate entropy of respiratory rate (ApEn-RR) did not vary among the three groups at any time series length, but approximate entropy of tidal volume (ApEn-VT) increased from the control group to Group V-P (p< .017) to Group V-F (p< .017) at all time series lengths. ApEn-VT was very specific but only moderately sensitive at identifying respiratory failure. CONCLUSION: Respiratory failure causes tidal volume patterns to become increasingly irregular, but increasing respiratory rate has no effect on respiratory rate pattern.

A computer model of gas exchange during cardiopulmonary resuscitation.

This paper presents a computer model of gas exchange during cardiopulmonary resuscitation (CPR) that permits independent adjustment of inspired air content (16% O2 and 4.5% CO2 present in mouth-to-mouth (MTM) ventilation or ambient air), shunt, deadspace, diffusion impairment, cardiac output, and ventilation. The model contains 15500 acini, each with its own blood supply. Gas exchange occurs at each perfused and ventilated acinus. Arterial P(O2) and P(CO2) are calculated from the summed arterial blood flow using standard formulae. The model and simulations show that MTM ventilation provides inadequate oxygenation when the victim is at high altitude or has diffusion impairment. They also show that analysis of inspired and expired gas concentrations to measure gas exchange primarily measures wash in and wash out of gas when cardiac output is low and that this explains the negative oxygen consumption and carbon dioxide production measured in a previous study.

Negative-pressure pulmonary edema with a patent airway.

Negative pressure is a rarely occurring cause of pulmonary edema. It has previously been reported only in the presence of a closed glottis or obstructed airway. A 64-year-old man with 74% body surface burn without any inhalation injury experienced acute pulmonary edema on hospital day 11 associated with high-minute volume and negative inspiratory pressures at the ventilator. The edema cleared after sedation and paralysis. Workup disclosed pulmonary emboli and normal cardiac-filling pressures. A mechanical model, simulating his breathing, measured intrathoracic pressure of -37 +/- 12 mm Hg, which is sufficiently negative to cause pulmonary edema despite a patent airway. Pulmonary emboli increased his respiratory drive to amounts greater than what the ventilator could deliver, thus leading to the large negative intrathoracic pressure and pulmonary edema.

Propofol-based versus fentanyl-isoflurane-based anesthesia for cardiac surgery.

OBJECTIVE: To evaluate drug costs, time of mechanical ventilation, complications, and hospital length of stay comparing propofol-based with fentanyl-isoflurane-based anesthesia. DESIGN: A prospective, randomized study. SETTING: A university-affiliated, tertiary care community hospital. PARTICIPANTS: Seventy patients undergoing primary coronary artery bypass surgery. INTERVENTIONS: Patients were randomized to either a low-dose fentanyl-isoflurane or a lower-dose fentanyl-isoflurane anesthetic supplemented with a continuous infusion of propofol. MEASUREMENTS AND MAIN RESULTS: Fentanyl-isoflurane anesthesia was significantly less expensive ($50.03+/-$27.26 v $121.69+/-$31.40) for anesthesia drugs and ($58.08+/-$27.39 v $129.91+/-$31.52) for total drug costs. There was also a trend for patients in the fentanyl-isoflurane group to be extubated slightly sooner (388+/-202 v 449+/-252 min) and go home sooner (5.1+/-1.8 v 6.0+/-3.0 days). CONCLUSION: Fentanyl-isoflurane provides an inexpensive anesthetic that permits as prompt an extubation as propofol, thus conserving resources for other patients.

Effects of simulated mouth-to-mouth ventilation during external cardiac compression or active compression-decompression in a swine model of witnessed cardiac arrest.

STUDY OBJECTIVE: To assess the effects of simulated mouth-to-mouth (MTM) ventilation on blood gases, gas exchange, and minute ventilation during external cardiac compression (ECC) or active compression-decompression (ACD) in a swine model of witnessed cardiac arrest and bystander CPR. METHODS: Twenty swine were anesthetized, intubated, ventilated with room air, and monitored for aortic and right atrial pressure and blood gas sampling. After 1 minute of ventricular fibrillation cardiac arrest, ECC or ACD was manually performed at a rate of 100 per minute for 12 minutes. Animals in the room air group had their endotracheal tubes open to air, whereas those in the MTM group were mechanically ventilated with a gas mixture of 16% oxygen and 4% carbon dioxide. Arterial and venous PO2, PCO2, and pH values; oxygen consumption (VO2); carbon dioxide production (VCO2); and minute ventilation (VE) were measured at baseline and 1, 5, 9, and 13 minutes after induction of cardiac arrest. RESULTS: MTM ventilation did not alter arterial or venous PO2 values in comparison with room air but did result in higher arterial PCO2 values at 5 and 9 minutes (although the mean PCO2 was 40 mm Hg or less [5.3 kPa] in all groups) and significant central venous hypercarbic acidosis at 9 and 13 minutes. Arterial PO2 values were greater in the ACD than the ECC groups at 5, 9, and 13 minutes, although all groups maintained acceptable PO2 (mean values > or = 60 mm Hg [8.0 kPa]) through 9 minutes of CPR and through 13 minutes in all but the ECC-room air group. PCO2 values were lower in the ACD groups beyond 1 minute, with the ACD-room air group showing extreme hyperventilation (mean PCO2 < or = 20 mm Hg [2.7 kPa]). MTM ventilation resulted in negative VO2 and VCO2 for the first few minutes, reflecting changes in pulmonary gas stores. As equilibrium was approached, VO2 and VCO2 approached zero in all groups, reflecting low cardiac output. MTM ventilation did not improve VE over room air at any time during ACD. It did improve VE during ECC, but only at the 12th interval. CONCLUSION: In this swine model of witnessed CPR, simulated MTM ventilation was not beneficial for blood gases, gas exchange, or ventilation during ECC or ACD CPR.