Diagnostic utility of capnography in emergency department triage for screening acidemia: a pilot study.

BACKGROUND: Capnography is a quantitative and reliable method of determining the ventilatory status of patients. We describe the test characteristics of capnography obtained during Emergency Department triage for screening acidemia. RESULTS: We performed an observational, pilot study of adult patients presenting to Emergency Department (ED) triage. The primary outcome was acidemia, as determined by the basic metabolic panel and/or blood gas during the ED visit. Secondary outcomes include comparison of estimated and measured respiratory rates (RR), relationships between end-tidal CO2 (EtCO2) and venous partial pressure of CO2, admission disposition, in-hospital mortality during admission, and capnogram waveform analysis. A total of 100 adult ED encounters were included in the study and acidemia ([Formula: see text] or [Formula: see text]) was identified in 28 patients. The measured respiratory rate (20.3 ± 6.4 breaths/min) was significantly different from the estimated rate (18.4 ± 1.6 breaths/min), and its area under the receiver operating curve (c-statistic) to predict acidemia was only 0.60 (95% CI 0.51-0.75, p = 0.03). A low end-tidal CO2 (EtCO2 < 32 mmHg) had positive (LR+) and negative (LR-) likelihood ratios of 4.68 (95% CI 2.59-8.45) and 0.34 (95% CI 0.19-0.61) for acidemia, respectively-corresponding to sensitivity 71.4% (95% CI 51.3-86.8) and specificity 84.7% (95% CI 74.3-92.1). The c-statistic for EtCO2 was 0.849 (95% CI 0.76-0.94, p = 0.00). Waveform analysis further revealed characteristically abnormal capnograms that were associated with underlying pathophysiology. CONCLUSIONS: Capnography is a quantitative method of screening acidemia in patients and can be implemented feasibly in Emergency Department triage as an adjunct to vital signs. While it was shown to have only modest ability to predict acidemia, triage capnography has wide generalizability to screen other life-threatening disease processes such as sepsis or can serve as an early indicator of clinical deterioration.

Wearing face masks while climbing stairs influences respiratory physiology.

During the COVID-19 pandemic wearing face masks was mandatory. Nowadays, face masks are still encouraged indoors, especially in hospitals. People climbing stairs with masks describe unpredictable dyspnea. In this study, healthy adults climbed 5 floors with and without a mask. Various cardio-respiratory parameters were measured, including O2-saturation (O2-Sat) and end-tidal CO2(EtCO2), at baseline and on the top floor. Subjective indexes, such as Borg's scale, were evaluated. Thirty-two volunteers (16 males), median age 39 years (IQR 32.5-43), median BMI = 23.6 (IQR 21.5-25.1), with good fitness levels, participated. Comparing baseline to end-activity, median (IQR): O2-Sat change was -1.0% (-2-0) without mask, versus -3.0% (-4-0) with mask,p= 0.003; EtCO2+ 7.0 (+3.3-+9) without mask, versus +8.0 (+6-+12) with mask,p= 0.0001. Hypercarbia was seen in 5 (15.6%) participants without mask, median = 48 mmHg (IQR 47.5-51), and in 11 (34%) participants with mask, median = 50 mmHg (IQR 47-54),p< 0.001. Desaturation (O2-Sat < 95%) was seen in 5 (15.6%) participants without mask, median = 94% (IQR 93%-94%), and in 10 (31%) participants with mask, median = 91.5% (IQR 90%-93%),p= 0.06. Regression analysis demonstrated that only male sex was significantly associated with abnormal EtCO2(OR = 26.4, 95% CI = 1.9-366.4,p= 0.005). Ascent duration increased from median (IQR) of 94 s (86-100) without mask to 98 s (89-107) with mask,p< 0.001. Borg's scale of perceived exertion (range 0-10) increased from median (IQR) of 3.0 (2.5-3.87) without mask to 4.0 (3.0-4.37) with mask,p< 0.001. To conclude, during routine daily activities, such as stair-climbing, face masks cause dyspnea, and have measurable influences on ventilation, including true desaturation and hypercapnia, especially in males.

Physiological Variability during Prehospital Stroke Care: Which Monitoring and Interventions Are Used?

Prehospital care is a fundamental component of stroke care that predominantly focuses on shortening the time between diagnosis and reaching definitive stroke management. With growing evidence of the physiological parameters affecting long-term patient outcomes, prehospital clinicians need to consider the balance between rapid transfer and increased physiological-parameter monitoring and intervention. This systematic review explores the existing literature on prehospital physiological monitoring and intervention to modify these parameters in stroke patients. The systematic review was registered on PROSPERO (CRD42022308991) and conducted across four databases with citation cascading. Based on the identified inclusion and exclusion criteria, 19 studies were retained for this review. The studies were classified into two themes: physiological-monitoring intervention and pharmacological-therapy intervention. A total of 14 included studies explored prehospital physiological monitoring. Elevated blood pressure was associated with increased hematoma volume in intracerebral hemorrhage and, in some reports, with increased rates of early neurological deterioration and prehospital neurological deterioration. A reduction in prehospital heart rate variability was associated with unfavorable clinical outcomes. Further, five of the included records investigated the delivery of pharmacological therapy in the prehospital environment for patients presenting with acute stroke. BP-lowering interventions were successfully demonstrated through three trials; however, evidence of their benefit to clinical outcomes is limited. Two studies investigating the use of oxygen and magnesium sulfate as neuroprotective agents did not demonstrate an improvement in patient's outcomes. This systematic review highlights the absence of continuous physiological parameter monitoring, investigates fundamental physiological parameters, and provides recommendations for future work, with the aim of improving stroke patient outcomes.

Colorimetric CO2 Detector to Improve Effective Mask Ventilations in Very Preterm Infants: A Pilot Randomized Controlled Study.

INTRODUCTION: End-tidal CO2 (ETCO2) detector is currently recommended for confirmation of endotracheal tube placement during neonatal resuscitation. Whether it is feasible to use ETCO2 detectors during mask ventilation to reduce risk of bradycardia and desaturations, which are associated with increased risk of death in preterm babies, is unknown. METHODS: This is a pilot randomized controlled trial (NCT04287907) involving newborns 24 + 0/7 to 32 + 0/7 weeks gestation who required mask ventilation at birth. Infants were randomized into groups with or without colorimetric ETCO2 detectors. Combined duration of any bradycardia (<100 bpm) and time below prespecified target oxygen saturation (SpO2) as measured by pulse oximetry were compared. RESULTS: Fifty participants were randomized, 47 with outcomes analysed (2 incomplete data, 1 postnatal diagnosis of trachea-oesophageal fistula). Mean gestational age and birthweight were 28.5 ± 1.9 versus 29.4 ± 1.6 weeks (p = 0.1) and 1,252.7 ± 409.7 g versus 1,334.6 ± 369.1 g (p = 0.5) in the intervention and control arm, respectively. Mean combined duration of bradycardia and desaturation was 276.7 ± 197.7 s (intervention) and 322.7 ± 277.7 s (control) (p = 0.6). Proportion of participants with any bradycardia or desaturation at 5 min were 38.1% (intervention) and 56.5% (control) (p = 0.2). No chest compressions, epinephrine administration, or death occurred in the delivery room. CONCLUSION: This pilot study demonstrates the feasibility of a trial to evaluate colorimetric ETCO2 detectors during mask ventilation of very preterm infants to reduce bradycardia and low SpO2. Further assessment with a larger population will be required to determine if ETCO2 detector usage at resuscitation reduces risk of adverse outcomes, including death and disability, in very preterm infants.

Sports despite masks: no negative effects of FFP2 face masks on cardiopulmonary exercise capacity in children.

Face masks were recognized as one of the most effective ways to prevent the spread of the COVID-19 virus in adults. These benefits were extended to children and adolescents. However, the fear of negative consequences from wearing a face mask during physical exercise led to cancellations of physical education lessons. This further decreased the amount of physical activity available to children and adolescents during the pandemic. However, there is little published data on the potential adverse effects of wearing the most effective and partially mandatory FFP2/N95 face masks during PE or physical activity (PA) in this age. Even though the pandemic has been declared as passed by the WHO, the rise of a new pandemic and thus the use of face masks for limiting its spread is inevitable, so we need to be better prepared for alternative options to lockdown and limitation of PA in such a scenario. Twenty healthy children aged 8-10 years performed two identical cardiopulmonary exercise tests as an incremental step test on a treadmill within an interval of 2 weeks, one time without wearing a protective mask and one time wearing an FFP2 mask. The cardiopulmonary exercise parameter and especially the end-expiratory gas exchange for oxygen and carbon dioxide (petO2 and petCO2) were documented for each step, at rest and 1 min after reaching physical exhaustion. Twelve boys (mean age 8.5 ± 1.4 years) and 8 girls (mean age 8.8 ± 1.4 years) showed no adverse events until maximal exertion. The mean parameters measured at peak exercise did not differ significantly between both examinations (mean peak VO2 = 42.7 ± 9.5 vs 47.8 ± 12.9 ml/min/kg, p = 0.097, mean O2pulse 7.84 ± 1.9 ml/min vs. 6.89 ± 1.8, p = 0.064, mean VE/VCO2slope 33.4 ± 5.9 vs. 34.0 ± 5.3, p = 0.689). The only significant difference was the respiratory exchange rate (RER, 1.01 ± 0.08 vs 0.95 ± 0.08, p = 0.004). The measured respiratory gases (end-tidal O2 and CO2) decreased and respectively increased significantly in almost every step when wearing an FFP2 mask. However, these levels were well below hypercapnia and above hypoxia. CONCLUSION:  In this study, no significant differences in the cardiorespiratory function at peak exercise could be discerned when wearing an FFP2/N95 face mask. While the end-tidal values for CO2 increased significantly and the end-tidal values for O2 decreased significantly, these values did never reach levels of hypercapnia or hypoxia. Furthermore, the children terminated the exercise at a lower RER and heart rate (HR) suggesting a subconscious awareness of the higher strain. Since the detrimental effects of limiting sports during the pandemic are well documented, stopping PE lessons altogether because of the minor physiological effects of wearing these masks instead of simply stopping pushing children to perform at their best seems premature and should be reconsidered in the future. WHAT IS KNOWN: • Wearing a face mask has an influence on psychological, social, and physiological functions in adults. • Because of the observed effects of wearing face masks in adults, physical activity in children was limited during the pandemic. WHAT IS NEW: • Wearing an FFP2/N95 mask during physical activity did not lead to hypercapnia or hypoxia in children in this study. • Even though end-tidal CO2 values were significantly higher and end-tidal O2 values significantly lower when wearing an FFP2/N95 face mask, no pathological values were reached.

Elevation of end-tidal CO2 during exercise is attenuated in patients with cardiac amyloidosis.

Reduced exercise tolerance is one of the hallmarks of patients with cardiac amyloidosis (CA), but detailed biological responses during exercise were not investigated. The purpose of this study was to compare the cardiopulmonary exercise test (CPX) parameters between CA patients and propensity-matched heart failure patients. This was a single-center, retrospective, observational study of patients diagnosed with CA. The control group was extracted by propensity score matching from patients who underwent CPX for chronic heart failure during the same period. Clinical data including assessment of biological responses during CPX were compared between the patients with CA (CA group, n = 16) and the control group (non-CA group, n = 16). Echocardiography suggested more impaired diastolic function in the CA group than in the non-CA group. There was no significant difference between groups in the fraction of end-tidal carbon dioxide (FETCO2) at rest. However, the difference between the FETCO2 at rest and the FETCO2 at the respiratory compensation point (ΔFETCO2) was significantly smaller in the CA group than in the non-CA group (0.40% ± 0.37% vs. 0.82% ± 0.33%; p = 0.002). Only in the CA group, there was a significant negative correlation between the ΔFETCO2 and the E/e' ratio on echocardiography (r = - 0.521; p = 0.039) and the serum high-sensitivity troponin T concentration (r = - 0.501; p = 0.048). In conclusion, patients with CA may find it difficult to increase cardiac output during exercise due to severe diastolic dysfunction.

Anaesthetic Management and Physiologic Effects of Pneumoperitoneum in Patients With Chronic Obstructive Pulmonary Disease Undergoing Laparoscopic Cholecystectomy.

OBJECTIVE: This study aimed to assess the physiological changes and clinical outcomes in patients with chronic obstructive pulmonary disease (COPD) undergoing laparoscopic cholecystectomy. METHODS: This prospective cohort study included 50 patients of the American Society of Anesthesiology (ASA) physical status I and II with mild to moderate COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I-II) scheduled for laparoscopic cholecystectomy. We monitored heart rate, mean arterial pressure, end-tidal carbon dioxide (EtCO2), arterial carbon dioxide (PaCO2), and bicarbonate (HCO3) levels at baseline, 30 minutes after induction or 15 minutes post-insufflation, 15 minutes post-deflation, and 60 minutes post-operative. Perioperative complications and post-operative recovery characteristics were also observed. Descriptive statistics were used to summarise the demographic and clinical characteristics of the patients. The correlation between HCO3 and EtCO2 was plotted on a scatterplot, and Pearson's correlation 'r' was calculated. The changes in physiological parameters over time were analysed using a paired t-test. A p-value of less than 0.05 is considered statistically significant. RESULTS: We observed a statistically significant but transient increase in heart rate, mean arterial pressure, and EtCO2 at 30 minutes after induction or 15 minutes post-insufflation, which returned to baseline levels within 15 minutes of deflation. Similarly, arterial CO2 and bicarbonate levels were also significantly increased at 15 minutes post-insufflation, yet remained within the normal physiological range. The study reported no serious perioperative complications, and all patients had an uneventful recovery. CONCLUSION: While patients with mild to moderate COPD can experience transient physiological changes during laparoscopic cholecystectomy, these changes are generally well-tolerated and not associated with adverse clinical outcomes. Therefore, laparoscopic cholecystectomy can be considered a safe procedure in these patients. Future research should focus on the implications and safety of this procedure in patients with severe COPD.

Arterial versus end-tidal carbon dioxide levels in children with congenital heart disease: a prospective cohort study in patients undergoing pulmonary catheterization.

Capnography has been the standard in the operating room for a long time now. When variable amounts of intrapulmonary shunt and intracardiac shunt are taken into account, arterial carbon dioxide (CO2) and end-tidal CO2 typically match rather well. The gap between arterial and end-tidal CO2 widens in patients with cardiopulmonary disorders. The current study sought to determine how arterial and end-tidal CO2 correlated with each other and with hemoglobin saturation both before and after pulmonary catheterization in a pediatric population with congenital heart disease. Methods: Fifty-seven children with congenital heart disease who underwent cardiopulmonary catheterization between March 2018 and April 2019 were included in a prospective cohort study at Children's Medical Center. Arterial and end-tidal CO2, and hemodynamic variables were assessed prior to the catheterization procedure. Then the patients underwent catheterization, and before being extubated, these variables were again assessed and compared to the baseline levels. Results: End-tidal CO2 increased significantly in cyanotic patients following the catheterization procedure, and the difference between arterial and end-tidal CO2 decreased significantly. End-tidal CO2, arterial CO2, and their difference did not significantly change in non-cyanotic patients following the catheterization procedure. End-tidal and arterial CO2 were not significantly correlated in cyanotic patients (r=0.411, P=0.128), but they were correlated after the catheterization procedure (r=0.617, P=0.014). Conclusions: End-tidal CO2 can estimate arterial CO2 in non-cyanotic patients reasonably. End-tidal CO2 cannot be used to estimate arterial CO2 in cyanotic patients since there is no association. After cardiac defect correction, end-tidal CO2 can be a reliable predictor of arterial CO2.

Toward vendor-independent measurement of cerebral venous oxygenation: Comparison of TRUST MRI across three major MRI manufacturers and association with end-tidal CO2.

Cerebral venous oxygenation (Yv ) is a valuable biomarker for a variety of brain diseases. T2 relaxation under spin tagging (TRUST) MRI is a widely used method for Yv quantification. In this work, there were two main objectives. The first was to evaluate the reproducibility of TRUST Yv measurements across MRI scanners from different vendors. The second was to examine the correlation between Yv and end-tidal CO2 (EtCO2 ) in a multisite, multivendor setting and determine the usefulness of this correlation to account for variations in Yv caused by normal variations and physiological fluctuations. Standardized TRUST pulse sequences were implemented on three scanners from major MRI vendors (GE, Siemens, Philips). These scanners were located at two research institutions. Ten healthy subjects were scanned. On each scanner, the subject underwent two scan sessions, each of which included three TRUST scans, to evaluate the intrasession and intersession reproducibility of Yv . Each scanner was also equipped with a capnograph device to record the EtCO2 of the subject during the MRI scan. We found no significant bias in Yv measurements across the three scanners (P = 0.18). The measured Yv values on the three scanners were also strongly correlated with each other (intraclass correlation coefficients > 0.85, P < 0.001). The intrasession and intersession coefficients of variation of Yv were less than 4% and showed no significant difference among the scanners. In addition, our results revealed that (1) within the same subject, Yv increased with EtCO2 at a rate of 1.24 ± 0.17%/mmHg (P < 0.0001), and (2) across different subjects, individuals with a higher EtCO2 had a higher Yv , at a rate of 0.94 ± 0.36%/mmHg (P = 0.01). These results suggest that (1) the standardized TRUST sequences had similar accuracies and reproducibilities for the quantification of Yv across the scanners, and (2) recording of EtCO2 may be a useful complement to Yv measurement to account for CO2 -related physiological fluctuations in Yv in multisite, multivendor studies.

Physiologic effects of surgical masking in children versus adults.

Background: Surgical masks remain a focal part of the CDC guidelines to decrease COVID-19 transmission. Evidence refuting significant effects of masking on ventilation is mostly limited to small studies, with a paucity of studies on children, and none comparing children to adults. Methods: A total of 119 subjects were enrolled (71 adults, 49 children) in a prospective interventional study with each subject serving as their own mask-free control. End tidal CO2 (ETCO2), inspired CO2 (ICO2), and respiratory rate were measured by nasal cannula attached to an anesthesia machine D-fend module. Pulse oximetry and heart rate were also followed. After the mask-free period, an ASTM Level 3 disposable surgical mask was donned and 15 min of mask-worn data were collected. Results: A steady state was confirmed for ETCO2 and ICO2 over the masked period, and mean ICO2 levels rose significantly (p < 0.001) after masking in all age groups. The increase in ICO2 for the 2- to 7-year-old group of 4.11 mmHg (3.23-4.99), was significantly higher (p < 0.001) than the final ΔICO2 levels for both the 7- to 14-year-old group, 2.45 mmHg (1.79-3.12), and adults, 1.47 mmHg (1.18-1.76). For the pediatric group there was a negative, significant correlation between age and ΔICO2, r = -0.49, p < 0.001. Masking resulted in a statistically significant (p < 0.01) rise in ETCO2 levels of 1.30 mmHg in adults and 1.36 mmHg in children. The final respective ETCO2 levels, 34.35 (33.55-35.15) and 35.07 (34.13-36.01), remained within normal limits. Pulse oximetry, heart rate, and respiratory rate were not significantly affected. Discussion: The physiology of mechanical dead space is discussed, including the inverse relationship of subject age vs ICO2. The methodology and results are compared to previously published studies which detracted from the physiologic safety of surgical masking. Conclusions: The wearing of a surgical mask results in a statistically significant rise in ICO2 and a smaller rise in ETCO2. Because ETCO2 and other variables remain well within normal limits, these changes are clinically insignificant.

High-intensity exercise does not protect against orthostatic intolerance following bedrest in 55- to 65-yr-old men and women.

Prolonged bedrest provokes orthostatic hypotension and intolerance of upright posture. Limited data are available on the cardiovascular responses of older adults to head-up tilt following bedrest, with no studies examining the potential benefits of exercise to mitigate intolerance in this age group. This randomized controlled trial of head-down bedrest (HDBR) in 55- to 65-yr-old men and women investigated if exercise could avert post-HDBR orthostatic intolerance. Twenty-two healthy older adults (11 female) underwent a strict 14-day HDBR and were assigned to either an exercise (EX) or control (CON) group. The exercise intervention included high-intensity, aerobic, and resistance exercises. Head-up tilt-testing to a maximum of 15 minutes was performed at baseline (Pre-Bedrest) and immediately after HDBR (R1), as well as 6 days (R6) and 4 weeks (R4wk) later. At Pre-Bedrest, three participants did not complete the full 15 minutes of tilt. At R1, 18 did not finish, with no difference in tilt end time between CON (422 ± 287 s) and EX (409 ± 346 s). No differences between CON and EX were observed at R6 or R4wk. At R1, just 1 participant self-terminated the test with symptoms, while 12 others reported symptoms only after physiological test termination criteria were reached. Finishers on R1 protected arterial pressure with higher total peripheral resistance relative to Pre-Bedrest. Cerebral blood velocity decreased linearly with reductions in arterial pressure, end-tidal CO2, and cardiac output. High-intensity interval exercise did not benefit post-HDBR orthostatic tolerance in older adults. Multiple factors were associated with the reduction in cerebral blood velocity leading to intolerance.

High central venous pressure amplitude predicts successful defibrillation in a porcine model of cardiac arrest.

AIM: Increasing venous return during cardiopulmonary resuscitation (CPR) has been shown to improve hemodynamics during CPR and outcomes following cardiac arrest (CA). We hypothesized that a high central venous pressure amplitude (CVP-A), the difference between the maximum and minimum central venous pressure during chest compressions, could serve as a robust predictor of return of spontaneous circulation (ROSC) in addition to traditional measurements of coronary perfusion pressure (CPP) and end-tidal CO2 (etCO2) in a porcine model of CA. METHODS: After 10 min of ventricular fibrillation, 9 anesthetized and intubated female pigs received mechanical chest compressions with active compression/decompression (ACD) and an impedance threshold device (ITD). CPP, CVP-A and etCO2 were measured continuously. All groups received biphasic defibrillation (200 J) at minute 4 of CPR and were classified into two groups (ROSC, NO ROSC). Mean values were analyzed over 3 min before defibrillation by repeated-measures Analysis of Variance and receiver operating characteristic (ROC). RESULTS: Five animals out of 9 experienced ROSC. CVP-A showed a statistically significant difference (p = 0.003) between the two groups during 3 min of CPR before defibrillation compared to CPP (p = 0.056) and etCO2 (p = 0.064). Areas-under-the-curve in ROC analysis for CVP-A, CPP and etCO2 were 0.94 (95% Confidence Interval 0.86, 1.00), 0.74 (0.54, 0.95) and 0.78 (0.50, 1.00), respectively. CONCLUSION: In our study, CVP-A was a potentially useful predictor of successful defibrillation and return of spontaneous circulation. Overall, CVP-A could serve as a marker for prediction of ROSC with increased venous return and thereby monitoring the beneficial effects of ACD and ITD.

Relationship between alveolar functional fraction and clinical outcomes in children during postoperative care after surgery for single-ventricular heart.

Background: Optimization of pulmonary to systemic blood flow (Qp: Qs) is the key to postoperative care of children with a single-ventricular heart. The ratio of end-tidal CO2 to partial pressure of CO2 called alveolar functional fraction (AFF) has shown a strong relationship with Qp: Qs in the catheterization lab in this population (with Qp: Qs of 1 correlating with AFF of 0.7). As there are no studies to understand the relationship between AFF and clinical outcomes in the postoperative care of these children, this study was carried out. Methodology and Results: This retrospective cohort study included 29 postoperative periods of children who underwent surgery for a single-ventricular heart. The average AFF was calculated for each early postoperative period. The primary clinical outcome was time in hours to normalize lactate. Other clinical outcomes included duration of mechanical ventilation, duration of milrinone infusion; presence of acute kidney injury (AKI), seizures and necrotizing enterocolitis (NEC); need for tracheostomy, need for extra-corporeal support, and mortality in the first 60 days postoperatively. The study population was divided into Group 1 with AFF ≤0.7 and Group 2 with AFF >0.7, to compare the outcome differences between the groups. Time to normalize the lactate had a modest negative correlation with the AFF, with Pearson's r = -0.49 (P = 0.007) for the entire cohort. The clinical outcomes were not statistically different for groups with AFF ≤0.7 and with AFF >0.7, although the group with AFF ≤0.7 had a higher incidence of NEC and higher mortality, whereas the group with AFF >0.7 had a higher incidence of AKI. Conclusions: In this small study, the AFF showed a modest negative correlation with the time to normalize lactate in postoperative care after surgery for a single-ventricle heart. There were the trends with some other important clinical outcomes but not statistically significant. A larger, multi-center study is needed to delineate these relationships further.

The Use of End-Tidal CO2 and Integrated Pulmonary Index to Predict Postspinal Hypotension in Cesarean Section.

Early diagnosis and treatment of postspinal hypotension (PSH) in obstetric anaesthesia reduces the risk of maternofetal complications. In this study, the effect of EtCO2 and the integrated pulmonary index (IPI) in predicting PSH was investigated. Patients scheduled for cesarean section under spinal anaesthesia were included. The Capnostream 35 respiratory monitor (Medtronic, Inc., Dublin, Ireland) was used for EtCO2 and IPI. PSH developed in 52 (63.4%) of the 82 patients. EtCO2 and IPI values decreased significantly compared with baseline values in patients who developed PSH. There were statistically significant differences in EtCO2 (p = 0.001) and the IPI change (p = 0.045) in patients who developed PSH compared with those who did not. It was found that the EtCO2 difference had an independent effect on predicting PSH (p < 0.05), whereas the IPI difference did not (p > 0.05). One unit decrease in EtCO2 from the baseline increased the risk of PSH by 3.3 times. ROC curve analysis showed that the magnitude of change in EtCO2 was diagnostic for predicting PSH (AUC: 0.90 (0.83-0.97; p < 0.001)). IPI showed no predictive value for postspinal hypotension in cesarean section. However, EtCO2 monitoring, which is non-invasive and real-time monitoring, can be used to predict postspinal hypotension.

Effect of perioperative intravenous amiodarone on cardioversion of atrial fibrillation early after video-assisted thoracoscopic surgical ablation: Study protocol for a double-blind randomized controlled trial.

Introduction: Video-assisted thoracoscopic surgical (VATS) ablation is widely performed in surgical areas to treat atrial fibrillation (AF), which is minimally invasive and highly effective. Amiodarone, known as a class III antiarrhythmic agent, has the greatest potential to maintain sinus rhythm of AF. At present, few studies focused on the efficacy of perioperative intravenous amiodarone in the VATS ablation of AF. Therefore, the trial is designed to investigate the effect of perioperative amiodarone infusion on cardioversion of AF early after VATS ablation. Methods: and analysis: This will be a prospective, randomized, double-blind, controlled trial. The trial is to enroll 182 patients aged 18-70 years who will undergo VATS ablation of AF. All eligible participants will be randomly allocated to either the amiodarone or placebo group by using the block randomization in a 1:1 ratio. The primary endpoint will be freedom from atrial arrhythmias 24 h after the VATS procedure and be assessed using the Kaplan-Meier method. All data will be analyzed in accordance with the intention-to-treat principle. Discussion: The clinical trial has been designed to investigate the efficacy of perioperative intravenous amiodarone on cardioversion of AF early after VATS ablation. We are hoping to demonstrate that perioperative infusion of amiodarone could improve the maintenance of sinus rhythm 24 h after VATS ablation.

Contribution of chest compressions to end-tidal carbon dioxide levels generated during out-of-hospital cardiopulmonary resuscitation.

AIM: Characterise how changes in chest compression depth and rate affect variations in end-tidal CO2 (ETCO2) during manual cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrest (OHCA). METHODS: Retrospective analysis of adult OHCA monitor-defibrillator recordings having concurrent capnogram, compression depth, transthoracic impedance and ECG, and with atleast 1,000 compressions. Within each patient, during no spontaneous circulation, nearby segments with changes in chest compression depth and rate were identified. Average ETCO2 within each segment was standardised to compensate for ventilation rate variability. Contributions of relative variations in depth and rate to relative variations in standardised ETCO2 were characterised using linear and non-linear models. Normalisation between paired segments removed intra and inter-patient variation and made coefficients of the model independent of the scale of measurement and therefore directly comparable. RESULTS: A total of 394 pairs of segments from 221 patients were analysed (33% female, median (IQR) age 66 (55-74) years). Chest compression depth and rate were 50.4 (43.2-57.0)mm and 111.1 (106.5-116.1)compressions per minute. ETCO2 before and after standardization was 32.1 (23.0-41.4)mmHg and 28.5 (19.4-38.7)mmHg. Linear model coefficient of determination was 0.89. Variation in compression depth mainly explained ETCO2 variation (coefficient 0.95, 95% confidence interval (CI): 0.93-0.98) while changes in compression rate did not (coefficient 0.04, 95% CI: 0.01-0.07). Non-linear trend analysis confirmed the results. CONCLUSION: This study quantified the relative importance of chest compression characteristics in terms of their impact on CO2 production during CPR. With ventilation rate standardised, variation in chest compression depth explained variations in ETCO2 better than variation in chest compression rate.

An Educational Intervention to Improve Comfort with Applying and Interpreting Transcutaneous CO2 and End-tidal CO2 Monitoring in the PACU.

PURPOSE: The purpose of this study was to assess the effectiveness of an educational program about measuring ventilation using devices that assess carbon dioxide levels in patients recovering from a surgical procedure. DESIGN: A pre-post survey of knowledge attainment from an educational intervention about measuring ventilation using end-tidal carbon dioxide (EtCO2) and transcutaneous carbon dioxide (tcPCO2) devices in the postanesthesia care unit (PACU) was distributed to current members of the American Society of PeriAnesthesia Nurses. METHODS: Participants received a 12-question pre-intervention (five were related to demographics) and a five-question post-intervention survey. Non-demographic survey questions used a one to five Likert scale to assess comfortability or confidence. The intervention created was a voice-over presentation designed to improve PACU RN's comfort and confidence with using and interpreting tcPCO2 or EtCO2 in the PACU. FINDINGS: PACU RNs (N = 108) reported they 'never' or 'rarely' used EtCO2 (n = 57, 52.7%) monitoring or tcPCO2 (n = 93, 86.1%) monitoring in the PACU. A paired t test revealed statistically significant differences in the PACU RN's pre-survey and posttest comfortability of applying and interpreting EtCO2 or tcPCO2 monitors (P < .05). CONCLUSIONS: Capnography monitoring should be considered a standard of care for PACU patients. Education of registered nurses working in the PACU is critical before implementing EtCO2 or tcPCO2 monitoring.

Assessment of a new volumetric capnography-derived parameter to reflect compression quality and to predict return of spontaneous circulation during cardiopulmonary resuscitation in a porcine model.

We aimed to evaluate a volumetric capnography (Vcap)-derived parameter, the volume of CO2 eliminated per minute and per kg body weight (VCO2/kg), as an indicator of the quality of chest compression (CC) and to predict the return to spontaneous circulation (ROSC) under stable ventilation status. Twelve male domestic pigs were utilized for the randomized crossover study. After 4 min of untreated ventricular fibrillation (VF), mechanical cardiopulmonary resuscitation and ventilation were administered. Following 5-min washout periods, each animal underwent two sessions of experiments: three types of CC quality for 5 min stages in the first session, followed by advanced life support, consecutively in two sessions. Different CC quality had a significant effect on the partial pressure of end-tidal carbon dioxide (PetCO2), VCO2/kg, aortic pressure (mean), aortic systolic pressure, aortic diastolic pressure, right atrial pressure (mean), and carotid blood flow (P < 0.05). With the improvement in CC quality, the values of PetCO2 and VCO2/kg also increased, and the difference between the groups was statistically significant (P < 0.05). The Spearman rank test revealed a significant correlation between the Vcap-derived parameters and hemodynamics. PetCO2 and VCO2/kg have similar capabilities for discriminating survivors from non-survivors, and the area under the curve for both was 0.97. VCO2/kg had similar performance as PetCO2 in reflecting the quality of CC and prediction of achieving ROSC under stable ventilation status in a porcine model of VF-related cardiac arrest. However, VCO2/kg requires a longer time to achieve a stable state after adjusting for quality of CC than PetCO2.

Accuracy of a battery-powered portable capnometer in premature infants.

Carbon dioxide measurement is useful for confirmation of successful tracheal intubation and ensuring adequate ventilation. There are two types of CO2 detectors, i.e., single-use-only colorimetric devices and capnometers. Although portable capnometers are widely used for resuscitation, there have been no reports regarding their clinical utility in neonates. The correspondence between end-tidal CO2 (PetCO2) level determined using a battery-powered portable capnometer and arterial CO2 (PaCO2) was investigated using paired data obtained simultaneously from 26 neonates weighing 1262 ± 589 g at examination on mechanical ventilation. PetCO2 level and PaCO2 showed a strong correlation (r = 0.839, P < 0.001), and the correlation equation was: PetCO2 = 0.8 × PaCO2 + 1.1. Therefore, PetCO2 readings obtained with a battery-powered portable capnometer were likely to be underestimated. This became more pronounced with decreasing infant body weight at examination as the net difference in measurements of PaCO2 and PetCO2 was significantly positively correlated with infant body weight at examination (r = 0.451, P < 0.001). The observations presented here may be helpful in the use of battery-powered portable capnometers in neonates requiring controlled ventilation with tracheal intubation.

Multi-vendor and multisite evaluation of cerebrovascular reactivity mapping using hypercapnia challenge.

Cerebrovascular reactivity (CVR), which measures the ability of cerebral blood vessels to dilate or constrict in response to vasoactive stimuli such as CO2 inhalation, is an important index of the brain's vascular health. Quantification of CVR using BOLD MRI with hypercapnia challenge has shown great promises in research and clinical studies. However, in order for it to be used as a potential imaging biomarker in large-scale and multi-site studies, the reliability of CO2-CVR quantification across different MRI acquisition platforms and researchers/raters must be examined. The goal of this report from the MarkVCID small vessel disease biomarkers consortium is to evaluate the reliability of CO2-CVR quantification in three studies. First, the inter-rater reliability of CO2-CVR data processing was evaluated by having raters from 5 MarkVCID sites process the same 30 CVR datasets using a cloud-based CVR data processing pipeline. Second, the inter-scanner reproducibility of CO2-CVR quantification was assessed in 10 young subjects across two scanners of different vendors. Third, test-retest repeatability was evaluated in 20 elderly subjects from 4 sites with a scan interval of less than 2 weeks. In all studies, the CO2 CVR measurements were performed using the fixed inspiration method, where the subjects wore a nose clip and a mouthpiece and breathed room air and 5% CO2 air contained in a Douglas bag alternatively through their mouth. The results showed that the inter-rater CoV of CVR processing was 0.08 ± 0.08% for whole-brain CVR values and ranged from 0.16% to 0.88% in major brain regions, with ICC of absolute agreement above 0.9959 for all brain regions. Inter-scanner CoV was found to be 6.90 ± 5.08% for whole-brain CVR values, and ranged from 4.69% to 12.71% in major brain regions, which are comparable to intra-session CoVs obtained from the same scanners on the same day. ICC of consistency between the two scanners was 0.8498 for whole-brain CVR and ranged from 0.8052 to 0.9185 across major brain regions. In the test-retest evaluation, test-retest CoV across different days was found to be 18.29 ± 17.12% for whole-brain CVR values, and ranged from 16.58% to 19.52% in major brain regions, with ICC of absolute agreement ranged from 0.6480 to 0.7785. These results demonstrated good inter-rater, inter-scanner, and test-retest reliability in healthy volunteers, and suggested that CO2-CVR has suitable instrumental properties for use as an imaging biomarker of cerebrovascular function in multi-site and longitudinal observational studies and clinical trials.