Maximum End-tidal CO2 Research Articles

Risk factors and clinical significance of subcutaneous emphysema after robot-assisted laparoscopic rectal surgery: a single-center experience.

Subcutaneous emphysema (SE) is a complication of laparoscopic surgery, potentially resulting in severe respiratory failure. No reports to date have focused on SE during robot-assisted (RA) rectal surgery. We aimed to reveal the risk factors and clinical significance of SE after RA/laparoscopic rectal surgery. We retrospectively reviewed 221 consecutive patients who underwent RA/laparoscopic rectal surgery. The occurrence of SE was evaluated on postoperative radiographs. Laparoscopic surgery was performed in 120 patients and RA in 101. SE developed in 55 (24.9%) patients. Logistic regression analysis identified RA surgery (odds ratio [OR]: 4.89, 95% confidence interval [CI] 2.13-11.22, p < 0.001), higher age (OR: 1.06, 95% CI 1.03-1.11, p < 0.001), lower body mass index (BMI) (OR: 0.79, 95% CI 0.67-0.93, p = 0.004), thinner subcutaneous layer (OR: 0.88, 95% CI 0.79-0.98, p = 0.02), and lateral lymph node dissection (OR: 9.43, 95% CI 2.44-36.42, p < 0.001) as risk factors for SE. Maximum end-tidal CO2 was significantly higher in the SE than the non-SE cohort (p < 0.001). There was no difference in postoperative complication rate or length of hospital stay. Lower BMI (OR: 0.79, 95% CI 0.62-0.97, p = 0.02) and thinner subcutaneous layer (OR: 0.84, 95% CI 0.71-0.97, p = 0.01) were predictive factors in the RA cohort. SE occurs more frequently in RA compared with laparoscopic surgery. SE has a modest impact on short-term outcomes, but may occasionally cause severe problems. The indication of RA surgery should be considered carefully in high-risk elderly patients.

Relationship between ETCO2 and PaCO2 under Changing Capnogram in Ventilated Infants with NAVA: An Observational Study.

This observational study evaluated the validity of end-tidal CO2 (ETCO2) as a surrogate for arterial PCO2 (PaCO2) in infants on neurally adjusted ventilatory assist (NAVA), particularly considering the influence of variable spontaneous breathing on capnography waveforms. The study involved 16 infants, analyzing 50 paired ETCO2 and PaCO2 values. Deming regression analysis highlighted a notably stronger correlation for maximum ETCO2 (r2 = 0.6783, p <0.0001) compared to mean ETCO2 (r2 = 0.5686, p <0.0001) and demonstrated a significantly weaker association for minimum ETCO2 (r2 = 0.1838). These findings emphasize the superior predictive value of maximum ETCO2 in estimating PaCO2, advocating its reliable use in clinical monitoring, especially given the dynamic capnography associated with NAVA's variable pressures. The results suggest ETCO2's potential to enhance noninvasive respiratory management, reduce the frequency of blood sampling, and improve overall care for infants requiring mechanical ventilation.

0820 Integrated Polysomnographic and Sleep Symptom-Based Cluster Subtypes Associated with Incident Atrial Fibrillation

Abstract Introduction While sleep disorders are implicated in atrial fibrillation (AF), the interplay and overlap of these disorders in AF risk remains unclear and a risk stratification challenge. Sleep-based clusters associated with AF can account for this complexity and translate to actionable approaches to identify at-risk patients. We hypothesized discrete phenotypes of symptoms and polysomnography (PSG)-based data differ in relation to incident AF. Methods Cleveland Clinic patients (age&amp;gt;18) who underwent PSG 11/27/2004-12/30/2015 were retrospectively examined. Clusters were identified using latent class analysis of 23 symptoms (e.g. related to sleep disordered breathing (SDB), sleepiness, REM intrusion, NREM parasomnias), Epworth Sleepiness Scale (ESS) score, and 24 measures of SDB and sleep architecture from PSG reports. Outcome was 5-year incident AF. Cox-proportional hazards models were adjusted for age, sex, race, body mass index, cardiovascular disease and risk factors, tobacco use, chronic obstructive pulmonary disease, anti-arrhythmic medication use, and positive airway pressure use. Results The sample included 43,433 patients: age 51.8±14.5, 51.9% (n=22,548) male, 74.4% (n=32,313) White, 7.3% (n=3,151) with baseline AF, and 4.3% (n=1,875) developed 5-year incident AF. Five clusters were identified and ranked by strength of AF association: 1) Hypoxemic (n=3,245): highest %time SaO2&amp;lt; 90% (T90), 2) Apneas+Arousals (n=4,592): most witnessed apneas, highest apnea hypopnea index (AHI), highest arousal index, least hypopneas, 3) Short sleep+NREM (n=6,126): shortest sleep time, longest REM latency, lowest %REM, 4) Hypopneas (n=2,661): most hypopneas, 5) Long sleep+REM (n=26,809): longest sleep time, shortest REM latency, highest %REM. Compared to ‘Long sleep+REM’, ‘Hypoxemic’ had 47% higher AF risk (HR=1.47,95%CI=1.27-1.69), and ‘Hypopneas’ did not differ (HR=1.05,95%CI=0.86-1.28). Conclusion Of five clusters identified, the ‘Hypoxemic’ subtype conferred the strongest AF risk with the highest degree of hypoxemia (highest T90, lowest minimum and mean SaO2), maximum end-tidal CO2, heart rate, and ESS score. Consistent with prior evidence of hypoxemia as an AF driver and cardiovascular risk of the sleepy phenotype, this constellation of symptoms and physiologic alterations illustrates risk in the clinical setting, providing potential value as a risk prediction tool. Future investigation should focus on external validation of these findings. Support (if any) Cleveland Clinic Neurological Institute Center for Outcomes Research &amp; Evaluation Pilot Grant, Transformative Research Resource Development Award

Visceral adiposity is related to insulin sensitivity and inflammation in adolescents with obesity and mild sleep disordered breathing.

To evaluate the relationships between adipose tissue distribution, insulin secretion and sensitivity, sleep-disordered breathing, and inflammation in obese adolescents. Cross-sectional study of 56 obese adolescents who underwent anthropometric measures, dual-energy X-ray absorptiometry, overnight polysomnography, oral glucose tolerance test (OGTT) and frequently sampled intravenous glucose tolerance test. Correlation and regression analyses were used to assess relationships between adiposity, insulin secretion and sensitivity, measures of sleep-disordered breathing (oxyhemoglobin nadir, SpO2; apnea hypopnea index, AHI; arousal index, AI; maximum end-tidal CO2; non-REM sleep duration), and inflammation (high-sensitivity C-reactive protein, hsCRP). Subjects (55% female) were mean (SD) 14.4 (2.1)years, with BMI Z-score of 2.3 (0.4). AHI was >5 in 10 (18%) subjects and 1< AHI≤5 in 22 (39%). Visceral adipose tissue area (VAT) was positively correlated with OGTT 1 and 2h insulin and 1h glucose, and hsCRP (r=0.3-0.5, p≤0.007 for each). VAT was negatively correlated with sensitivity to insulin (r=-0.4, p=0.005) and SpO2 nadir (r=-0.3, p=0.04) but not with other sleep measures. After adjustment for BMI-Z, sex, population ancestry, age, and sleep measures, VAT remained independently associated with insulin measures and 1h glucose, but no other measures of glycemia. SAT was not associated with measures of glycemia or insulin resistance. Among adolescents with obesity, visceral adiposity was associated with insulin resistance, SpO2 nadir, and inflammation. The independent association of visceral adiposity with insulin resistance highlights the potential role of VAT in obesity-related chronic disease.

Physiological effects of providing supplemental air for avalanche victims. A randomised trial

BackgroundSurvival from avalanche burial is dependent on time to extraction, breathing ability, air pocket oxygen content, and avoiding rebreathing of carbon dioxide (CO2). Mortality from asphyxia increases rapidly after burial. Rescue services often arrive too late. Our objective was to evaluate the physiological effects of providing personal air supply in a simulated avalanche scenario as a possible concept to delay asphyxia. We hypothesize that supplemental air toward victim’s face into the air pocket will prolong the window of potential survival. MethodsA prospective randomized crossover experimental field study enrolled 20 healthy subjects in Hemsedal, Norway in March 2019. Subjects underwent in randomized order two sessions (receiving 2 litres per minute of air in front of mouth/nose into the air pocket or no air) in a simulated avalanche scenario with extensive monitoring serving as their own control. ResultsA significant increase comparing Control vs Intervention were documented for minimum and maximum end-tidal CO2 (EtCO2), respiration rate, tidal volume, minute ventilation, heart rate, invasive arterial blood pressures, but lower peripheral and cerebral oximetry. Controls compared to Intervention group subjects had a lower study completion rate (26% vs 74%), and minutes in the air pocket before interruption (13.1 ± 8.1 vs 22.4 ± 5.6 vs), respectively. ConclusionsParticipants subject to simulated avalanche burial can maintain physiologic parameters within normal levels for a significantly longer period if they receive supplemental air in front of their mouth/nose into the air pocket. This may extend the time for potential rescue and lead to increased survival.

Intrathoracic Airway Closure Impacts CO2 Signal and Delivered Ventilation during Cardiopulmonary Resuscitation.

End-tidal CO2 (EtCO2) is used to monitor cardiopulmonary resuscitation (CPR), but it can be affected by intrathoracic airway closure. Chest compressions induce oscillations in expired CO2, and this could reflect variable degrees of airway patency. To understand the impact of airway closure during CPR, and the relationship between the capnogram shape, airway closure, and delivered ventilation. This study had three parts: 1) a clinical study analyzing capnograms after intubation in patients with out-of-hospital cardiac arrest receiving continuous chest compressions, 2) a bench model, and 3) experiments with human cadavers. For 2 and 3, a constant CO2 flow was added in the lung to simulate CO2 production. Capnograms similar to clinical recordings were obtained and different ventilator settings tested. EtCO2 was compared with alveolar CO2 (bench). An airway opening index was used to quantify chest compression-induced expired CO2 oscillations in all three clinical and experimental settings. A total of 89 patients were analyzed (mean age, 69 ± 15 yr; 23% female; 12% of hospital admission survival): capnograms exhibited various degrees of oscillations, quantified by the opening index. CO2 value varied considerably across oscillations related to consecutive chest compressions. In bench and cadavers, similar capnograms were reproduced with different degrees of airway closure. Differences in airway patency were associated with huge changes in delivered ventilation. The opening index and delivered ventilation increased with positive end-expiratory pressure, without affecting intrathoracic pressure. Maximal EtCO2 recorded between ventilator breaths reflected alveolar CO2 (bench). During chest compressions, intrathoracic airway patency greatly affects the delivered ventilation. The expired CO2 signal can reflect CPR effectiveness but is also dependent on airway patency. The maximal EtCO2 recorded between consecutive ventilator breaths best reflects alveolar CO2.

End-Tidal CO2-Guided Chest Compression Delivery Improves Survival in a Neonatal Asphyxial Cardiac Arrest Model.

To determine whether end-tidal CO2-guided chest compression delivery improves survival over standard cardiopulmonary resuscitation after prolonged asphyxial arrest. Preclinical randomized controlled study. University animal research laboratory. 1-2-week-old swine. After undergoing a 20-minute asphyxial arrest, animals received either standard or end-tidal CO2-guided cardiopulmonary resuscitation. In the standard group, chest compression delivery was optimized by video and verbal feedback to maintain the rate, depth, and release within published guidelines. In the end-tidal CO2-guided group, chest compression rate and depth were adjusted to obtain a maximal end-tidal CO2 level without other feedback. Cardiopulmonary resuscitation included 10 minutes of basic life support followed by advanced life support for 10 minutes or until return of spontaneous circulation. Mean end-tidal CO2 at 10 minutes of cardiopulmonary resuscitation was 34 ± 8 torr in the end-tidal CO2 group (n = 14) and 19 ± 9 torr in the standard group (n = 14; p = 0.0001). The return of spontaneous circulation rate was 7 of 14 (50%) in the end-tidal CO2 group and 2 of 14 (14%) in the standard group (p = 0.04). The chest compression rate averaged 143 ± 10/min in the end-tidal CO2 group and 102 ± 2/min in the standard group (p < 0.0001). Neither asphyxia-related hypercarbia nor epinephrine administration confounded the use of end-tidal CO2-guided chest compression delivery. The response of the relaxation arterial pressure and cerebral perfusion pressure to the initial epinephrine administration was greater in the end-tidal CO2 group than in the standard group (p = 0.01 and p = 0.03, respectively). The prevalence of resuscitation-related injuries was similar between groups. End-tidal CO2-guided chest compression delivery is an effective resuscitation method that improves early survival after prolonged asphyxial arrest in this neonatal piglet model. Optimizing end-tidal CO2 levels during cardiopulmonary resuscitation required that chest compression delivery rate exceed current guidelines. The use of physiologic feedback during cardiopulmonary resuscitation has the potential to provide optimized and individualized resuscitative efforts.

Efficacy of CO2 insufflation during thoracoscopic esophagectomy in the left lateral position.

Thoracoscopic esophagectomy (TE) is widely performed as a minimally invasive technique in the management of esophageal cancer. The aim of this study was to estimate the efficacy of intrathoracic carbon dioxide (CO2) insufflation during TE in the left lateral position. From January 2010 to April 2016, 58 patients with esophageal cancer underwent TE without intrathoracic CO2 insufflation (Group N) and 37 patients with esophageal cancer underwent TE with intrathoracic CO2 insufflation (Group C). The operation results and respiratory parameters during the thoracic procedure were compared in both groups. A satisfactory surgical field was obtained by CO2 insufflation. There was no difference in the duration of the thoracic procedure or number of dissected mediastinal lymph nodes between the two groups. The amount of thoracic blood loss in Group C was significantly less than that in Group N (P<0.05). Intrathoracic CO2 insufflation did not affect oxygenation during single-lung ventilation. However, both end-tidal CO2 (ETCO2) 1h after single-lung ventilation and maximum ETCO2 in Group C were significantly higher than those in Group N. Intraoperative hypercapnia in Group C was permissive. The rate of extubation in the operation room, mortality and morbidity were not different between the two groups. Intrathoracic CO2 insufflation is beneficial to make satisfactory surgical field and to reduce thoracic blood loss in TE. Application of intrathoracic CO2 insufflation may contribute to the widespread adoption of TE in the left lateral position.

Effect of Increased Body Mass Index on Complication Rates during Laryngotracheal Surgery Utilizing Jet Ventilation.

Objective Jet ventilation has been used for >30 years as an anesthetic modality for laryngotracheal surgery. Concerns exist over increased risk with elevated body mass index (BMI). We reviewed our experience using jet ventilation for laryngotracheal stenosis to assess for complication rates with substratification by BMI. Study Design Case series with chart review. Setting Tertiary care center. Subjects and Methods A total of 126 procedures with jet ventilation were identified from October 2006 to December 2014. Complications were recorded, including intubation, unplanned admission, readmission, dysphonia, oral trauma, pneumothorax, pneumomediastinum, and tracheostomy. Lowest intraoperative oxygen saturation and maximum end-tidal CO2 (ETCO2) levels were recorded. Results Among 126 patients, 43, 77, and 6 had BMIs of <25, 25-35, and 36-45, respectively. In the BMI <25 group, there was 1 unplanned intubation. Mean maximum ETCO2 was 36.51 with no hypoxemia observed. In the BMI 25-35 group, 2 patients required intubation, and 1 sustained minor oral trauma. The mean maximum ETCO2 was 38.85, with 4 patients having oxygen saturation <90%. In the BMI 36-45 group, 2 patients required intubation. The mean maximum ETCO2 was 41 with no hypoxemia observed. BMI and length of stenosis were statistically significant variables associated with incidence of intraoperative intubation. Conclusion Increased BMI was associated with an increase in highest ETCO2 intraoperatively. However, this was not associated with an increase in major complications. Jet ventilation was performed without significant adverse events in this sample, and it is a viable option if used with an experienced team in the management of laryngotracheal stenosis.

Thoracoscopic part of minimal invasive oesophagectomy in semiprone position: our initial experience.

Surgical resection with curative intent is till the mainstay of treatment for resectable esophageal cancer. Minimal invasive oesophagectomy has the potential to lower morbidity and mortality. In all likelihood, thoracoscopic oesophagectomy in semiprone position gives all the benefits of prone position and can be converted to thoracotomy without change in patient position if needed. The aim of this study is to analyze the feasibility of thoracoscopic oesophagectomy in semiprone position. This is a retrospective analysis of the data of thoracoscopic oesophgeactomy in semiprone position at Kaizen Hospital, a tertiary care center for gastroenterology during the period of December 2011 to December 2012. All surgeries were performed under general anesthesia with a single-lumen endotracheal tube. Esophageal mobilization was done by thoracoscopic approach in a semiprone position and an end-to-end hand-sewn cervical anastomosis was done. Abdominal part was performed by laparoscopic method in 3 patients and by laparotomy in rest of the patients. Total of 12 patients were included in this study. There was 1 conversion to thoracotomy and 1 surgical mortality. Mean operating time for the thoracoscopic part was 103 minutes, mean estimated blood loss for the thoracoscopic part was 110 mL, mean maximum end-tidal CO2 38.5 mm Hg, mean lymph nodes retrieved 14, and all patients had R0 resection. The median intensive care unit stay was 1 day and hospital stay was 8 days. Thoracoscopic part of thoracolaparoscopic oesophagectomy in semiprone position is a feasible option. It gives all advantages of prone position and thoracotomy is possible without change in patient position. However, further large-scale studies are required.

Sustained life-like waveform capnography after human cadaveric tracheal intubation

IntroductionFresh frozen cadavers are effective training models for airway management. We hypothesised that residual carbon dioxide (CO2) in cadaveric lung would be detectable using standard clinical monitoring systems, facilitating detection...

Blinded Measure of Trendelenburg Angle in Pelvic Robotic Surgery

Study ObjectiveTo estimate the Trendelenburg angle needed to perform robotic gynecologic surgical procedures. DesignCross-sectional study (Canadian Task Force classification III). SettingCommunity hospital. PatientsAll women undergoing gynecologic pelvic surgery using the da Vinci surgical robot at a single institution between December 2010 and April 2011. InterventionsThe primary surgeon determined the Trendelenburg angle needed for adequate visualization to perform surgery defined as small bowel and sigmoid colon displaced out of the surgical field. Measurements and Main ResultsThe primary outcome, measured in blinded fashion, was the degree of Trendelenburg positioning needed to complete the surgical procedure robotically. Secondary data collected included body mass index, type of surgery performed, maximum end-tidal CO2, and maximum peak inspiratory pressure. Sixteen surgeons performed a total of 104 robotic gynecologic pelvic surgeries during the study. Data were available for 86 cases. The mean Trendelenburg angle used was 28.0 degrees (95% confidence interval, 26.9–29.1). This was significantly less than the 40 degrees (p < .001) commonly recommended. The Trendelenburg angle used did not correlate with body mass index (r = −0.2; p = .13) or type of surgery performed (p = .41). Neither the maximum end-tidal CO2 or maximum peak inspiratory pressure was influenced by the Trendelenburg angle used when adjusted for age and body mass index. ConclusionsA mean Trendelenburg angle of 28.0 degrees was adequate to complete most gynecologic robotic surgical procedures when compared with historical control angle of 40 degrees.

A comparison of two different ketamine and diazepam combinations with an alphaxalone and medetomidine combination for induction of anaesthesia in sheep

AIMS: To investigate the perceived adverse effects of a particular batch of ketamine during induction of anaesthesia in sheep and to assess if any adverse effects would make intubation more difficult for the veterinary students. METHODS: Thirty adult sheep (mean bodyweight 74.5 (SD 9.4) kg) were randomly assigned to one of six groups of five sheep. Sheep in Groups A and B received I/V 0.5 mg/kg diazepam and 10 mg/kg ketamine (Ketamine Injection; Parnell Laboratories NZ Ltd, of the suspect batch); those in Groups C and D received I/V 0.5 mg/kg diazepam and 10 mg/kg ketamine (Ketalar; Hospira NZ Ltd.), and those in Groups E and F received I/V 2 μg/kg medetomidine and 2 mg/kg alphaxalone. In Groups A, C and E, intubation was by an experienced anaesthetist, and in Groups B, D and F intubation was by a veterinary student. Time from injection to successful intubation, the ease of intubation, saturation of haemoglobin with oxygen (SpO2) and partial pressure of oxygen in arterial blood (PaO2) were measured before the sheep were connected to an anaesthetic machine and allowed to breath oxygen. Times to extubation, holding its head up and standing, maximum and minimum heart rates, respiratory rates, maximal end tidal CO2, and the quality of recovery were then recorded. RESULTS: There were no measurable differences in outcomes between sheep in Groups A and B compared with C and D. Time to intubation was slightly shorter for the experienced anaesthetist than the student, but the difference was not significant. The sheep in Groups E and F took less time to recover than those in Groups A−D (p<0.05), but there were no significant differences between the groups in either the ease of induction or quality of recovery. Most sheep in Groups E and F showed minor excitatory effects, mainly at induction, which did not interfere with induction. Respiratory rates were lower in Groups E and F than Groups A−D (p<0.01), but SpO2 was higher in Groups E and F than A and B (p<0.05). CONCLUSIONS: The clinical impression that the batch of Parnell ketamine produced unexpected effects was shown to be incorrect. All the combinations produced anaesthesia that allowed intubation by the veterinary student. CLINICAL RELEVANCE: All the drug combinations produced satisfactory anaesthesia in sheep, but the alphaxaloneand medetomidine combination resulted in faster recovery.

Post Cardiac Arrest Syndrome

Out-of-hospital cardiac arrest (OHCA) is a common initial presentation of cardiovascular disease, affecting up to 325 000 people in the United States each year.1 In a recent meta-analysis of >140 000 patients with OHCA, survival to hospital admission was 23.8%, and survival to hospital discharge was only 7.6%.2 In patients who initially achieve return of spontaneous circulation (ROSC) after OHCA, the significant subsequent morbidity and mortality are due largely to the cerebral and cardiac dysfunction that accompanies prolonged whole-body ischemia. This syndrome, called the post cardiac arrest syndrome, comprises anoxic brain injury, post cardiac arrest myocardial dysfunction, systemic ischemia/reperfusion response, and persistent precipitating pathology3,4 (Table 1). The contribution of each of these components in an individual patient depends on various factors, including prearrest comorbidities, duration of the ischemic insult, and cause of the cardiac arrest. This review focuses on therapeutic strategies and recent developments in managing patients who are initially resuscitated from cardiac arrest. View this table: Table 1. Post Cardiac Arrest Syndrome: Pathophysiology and Potential Treatment Strategies There are 3 major aspects that require consideration in the management of the post cardiac arrest patient. After resuscitation, a decision must be made in relation to the appropriate triage of the OHCA patient. The next phase of management concerns the in-hospital treatment, which must address each component of the postarrest syndrome as appropriate for the individual patient. Finally, there are issues relating to prognostication and the deployment of various secondary prevention measures. Our recommended treatment algorithm is summarized in the Figure. This ideally follows from the implementation of basic and advanced life support measures, including effective cardiopulmonary resuscitation and defibrillation when appropriate, which are major determinants of outcome.2 Such an approach to care may be further modified according to the presence of other comorbidities and precipitating factors, which should be assessed …

Does compression-only cardiopulmonary resuscitation generate adequate passive ventilation during cardiac arrest?

The need for rescue breaths in bystander CPR has been questioned after several studies have shown that omitting ventilation does not worsen outcome. Chest compression may produce passive tidal volumes large enough to provide adequate ventilation in animal studies, but no recent clinical studies have examined this phenomenon. We measured passive ventilation during optimal chest compression to determine whether compression-only CPR provides adequate gas exchange during cardiac arrest. Adult cardiac arrest patients were treated according to European Resuscitation Council guidelines. Chest compressions were performed using a mechanical chest compression device (LUCAS) with active decompression disabled to mimic manual compression. Respiratory variables were measured during periods of compression-only CPR. Emergency Department data were collected during compression-only CPR from 17 patients (11 male) aged 47-82 years who had suffered an out-of-hospital cardiac arrest. Median tidal volume per compression was 41.5 ml (range 33.0-62.1 ml), being considerably less than measured deadspace in all patients. Maximum end-tidal CO2 was 0.93 kPa (range 0.0-4.6 kPa). Minute volume CO2 was 19.5 ml (range 15.9-33.8; normal range 150-180 ml). At an advanced stage of cardiac arrest, passive ventilation during compression-only CPR is limited in its ability to maintain adequate gas exchange, with gas transport mechanisms associated with high frequency ventilation perhaps generating a very limited gas exchange. The effectiveness of passive ventilation during the early stages of CPR, when chest and lung compliance is greater, remains to be investigated.

Part 7.4: Monitoring and Medications

This section provides an overview of monitoring techniques and medications that may be useful during CPR and in the immediate prearrest and postarrest settings. ### Assessment During CPR At present there are no reliable clinical criteria that clinicians can use to assess the efficacy of CPR. Although end-tidal CO2 serves as an indicator of cardiac output produced by chest compressions and may indicate return of spontaneous circulation (ROSC),1,2 there is little other technology available to provide real-time feedback on the effectiveness of CPR. ### Assessment of Hemodynamics #### Coronary Perfusion Pressure Coronary perfusion pressure (CPP = aortic relaxation [diastolic] pressure minus right atrial relaxation phase blood pressure) during CPR correlates with both myocardial blood flow and ROSC (LOE 3).3,4 A CPP of ≥15 mm Hg is predictive of ROSC. Increased CPP correlates with improved 24-hour survival rates in animal studies (LOE 6)5 and is associated with improved myocardial blood flow and ROSC in animal studies of epinephrine, vasopressin, and angiotensin II (LOE 6).5–7 When intra-arterial monitoring is in place during the resuscitative effort (eg, in an intensive care setting), the clinician should try to maximize arterial diastolic pressures to achieve an optimal CPP. Assuming a right atrial diastolic pressure of 10 mm Hg means that the aortic diastolic pressure should ideally be at least 30 mm Hg to maintain a CPP of ≥20 mm Hg during CPR. Unfortunately such monitoring is rarely available outside the intensive care environment. #### Pulses Clinicians frequently try to palpate arterial pulses during chest compressions to assess the effectiveness of compressions. No studies have shown the validity or clinical utility of checking pulses during ongoing CPR. Because there are no valves in the inferior vena cava, retrograde blood flow into the venous system may produce femoral vein pulsations.8 Thus palpation of a pulse in the femoral triangle may indicate venous rather than arterial …

Reduction in Ventilator Response to CO2 With Relaxation Feedback During CO2 Rebreathing in Normal Adults

Previous studies have shown that relaxation biofeedback reduced time on the ventilator for the difficult-to-wean patients. To test the hypothesis that the underlying mechanism of biofeedback ventilator weaning was the reduction of neural respiratory drive (NRD). Prospective, linear regression analysis. Critical care medicine department in tertiary health care hospital. Fifteen healthy adult volunteers were randomly assigned to the biofeedback group, and 15 healthy adult volunteers were randomly assigned to a control group. Relaxation feedback was administered while a single variable, PaCO2, was inputted to the respiratory control system and the output measured. While rebreathing 7% CO2/93% O2, the biofeedback group received a baseline session and a relaxation feedback session and the control group received a baseline session and a no feedback session. During relaxation feedback, there was a significant (p < 0.001 to p < 0.05) reduction in the slope of minute ventilation (VI), mean inspiratory flow (VT/TI), occlusion pressure in 0.1 s from onset of inspiration (P100), respiration rate (RR), and diaphragm (DA) EMG compared to baseline. We also found the above breathing parameters decreased significantly for relaxation feedback (p < 0.001-0.05), compared to baseline, at maximum end-tidal CO2 (64 +/- 1.2 mm Hg) (all data are expressed as mean +/- SE). The decrease for VI = -4.65 +/- 1.17 L/min, DA EMG = -0.4 +/- 0.21 microV, P100 = -1.13 +/- 0.56 cm H2O, VT/ TI = -144 +/- 82.91 ml/s, and RR = -3.1 +/- 0.79 breaths/min. No significant changes occurred in these parameters for the control group. We conclude that the addition of the behavioral input of relaxation feedback results in decreasing the values of respiratory parameters that reflect NRD.

Clinical assessment of gas exchange in mature horses.

There are limited methods of assessing pulmonary function in horses at rest. We developed clinical techniques to measure gas exchange efficiency in horses and evaluated 3 groups of horses that were 1) asymptomatic based on auscultation with rebreathing, transtracheal aspirate cytology, and thoracic radiographs (n = 6), 2) asymptomatic at rest but symptomatic with rebreathing (n = 11) and 3) symptomatic at rest (n = 9). Blood samples were obtained from the transverse facial artery and jugular vein. Maximal end-tidal CO2 tension (PETCO2) was measured by an infrared capnograph through a facemask. Alveolar O2 tension, dead space fraction (V(D)/V(T)), and physiological shunt fraction (Q(S)/Q(T)) were calculated using standard formulae. Arterial O2 tension in Group 1 horses (mean +/-s.d.103+/-3 mmHg) was significantly higher than in Group 2 or Group 3 horses. Q(S)/Q(T) in Group 1 horses (0.37+/-0.98%) was significantly lower than in Group 2 and Group 3 horses. Mean +/-s.d.V(D)/V(T) in Group 1 horses (-18.2+/-3.1) was significantly lower than Group 3 horses but not Group 2 horses.

Human Malignant Hyperthermia Associated with Desflurane Anesthesia

Human Malignant Hyperthermia Associated with Desflurane Anesthesia

End-tidal carbon dioxide during cardiopulmonary resuscitation in humans presenting mostly with asystole: a predictor of outcome.

To determine whether continuous semiquantitative assessment of end-tidal CO2 could provide a highly sensitive predictor of return of spontaneous circulation during cardiopulmonary resuscitation (CPR). Prospective, clinical study. Prehospital CPR. One hundred twenty patients, during nontraumatic cardiac arrest. End-tidal CO2 values were measured continuously after tracheal intubation, and were categorized as the initial value, and as minimal and maximal values during the first 20 mins. Presenting rhythm was asystole in 22 of the first 24 patients. Return of spontaneous circulation occurred in eight patients. Initial, minimal, and maximal end-tidal CO2 values were significantly (p < .01) higher in these patients than in the patients without return of spontaneous circulation. Cutoff values providing a 100% sensitivity and the highest specificity in predicting return of spontaneous circulation were found to be 10 torr for initial and maximal end-tidal CO2 values, and 2 torr for the minimal end-tidal CO2 value. The number of patients required to reject (with a risk error of <.05) the hypothesis of an actual sensitivity of < or = 90% for an observed sensitivity of 100% was found to be 95. In the second part of the study, this hypothesis was prospectively tested for initial and maximal end-tidal CO2 values in the subsequent 96 patients. Presenting cardiac rhythm was asystole in 87 patients. Return of spontaneous circulation was obtained in 30 patients. The cutoff value of 10 torr for maximal end-tidal CO2 during the first 20 mins after tracheal intubation provided an observed sensitivity of 100% in predicting return of spontaneous circulation with a specificity of 67%. This result allows rejection of the hypothesis of an actual sensitivity of < or = 90% (p = .042). By contrast, the observed sensitivity of initial end-tidal CO2 was only 87%. End-tidal CO2 represents a valuable tool for monitoring patients presenting with asystole during prehospital CPR. Fluctuations in end-tidal CO2 during CPR and the utility of end-tidal CO2 in detecting return of spontaneous circulation justify its continuous measurement. In addition, a high sensitivity (>90%) in predicting return of spontaneous circulation is prospectively demonstrated using the maximal end-tidal CO2 during the first 20 mins after tracheal intubation, with a cutoff value of 10 torr. Such a prognostic indicator could be used for a more rational approach to prolonged CPR.