Increase In ETCO2 Research Articles

Temporal Trends in End-Tidal Capnography and Outcomes in Out-of-Hospital Cardiac Arrest

While widely measured, the time-varying association between exhaled end-tidal carbon dioxide (EtCO2) and out-of-hospital cardiac arrest (OHCA) outcomes is unclear. To evaluate temporal associations between EtCO2 and return of spontaneous circulation (ROSC) in the Pragmatic Airway Resuscitation Trial (PART). This study was a secondary analysis of a cluster randomized trial performed at multicenter emergency medical services agencies from the Resuscitation Outcomes Consortium. PART enrolled 3004 adults (aged ≥18 years) with nontraumatic OHCA from December 1, 2015, to November 4, 2017. EtCO2 was available in 1172 cases for this analysis performed in June 2023. PART evaluated the effect of laryngeal tube vs endotracheal intubation on 72-hour survival. Emergency medical services agencies collected continuous EtCO2 recordings using standard monitors, and this secondary analysis identified maximal EtCO2 values per ventilation and determined mean EtCO2 in 1-minute epochs using previously validated automated signal processing. All advanced airway cases with greater than 50% interpretable EtCO2 signal were included, and the slope of EtCO2 change over resuscitation was calculated. The primary outcome was ROSC determined by prehospital or emergency department palpable pulses. EtCO2 values were compared at discrete time points using Mann-Whitney test, and temporal trends in EtCO2 were compared using Cochran-Armitage test of trend. Multivariable logistic regression was performed, adjusting for Utstein criteria and EtCO2 slope. Among 1113 patients included in the study, 694 (62.4%) were male; 285 (25.6%) were Black or African American, 592 (53.2%) were White, and 236 (21.2%) were another race; and the median (IQR) age was 64 (52-75) years. Cardiac arrest was most commonly unwitnessed (n = 579 [52.0%]), nonshockable (n = 941 [84.6%]), and nonpublic (n = 999 [89.8%]). There were 198 patients (17.8%) with ROSC and 915 (82.2%) without ROSC. Median EtCO2 values between ROSC and non-ROSC cases were significantly different at 10 minutes (39.8 [IQR, 27.1-56.4] mm Hg vs 26.1 [IQR, 14.9-39.0] mm Hg; P < .001) and 5 minutes (43.0 [IQR, 28.1-55.8] mm Hg vs 25.0 [IQR, 13.3-37.4] mm Hg; P < .001) prior to end of resuscitation. In ROSC cases, median EtCO2 increased from 30.5 (IQR, 22.4-54.2) mm HG to 43.0 (IQR, 28.1-55.8) mm Hg (P for trend < .001). In non-ROSC cases, EtCO2 declined from 30.8 (IQR, 18.2-43.8) mm Hg to 22.5 (IQR, 12.8-35.4) mm Hg (P for trend < .001). Using adjusted multivariable logistic regression with slope of EtCO2, the temporal change in EtCO2 was associated with ROSC (odds ratio, 1.45 [95% CI, 1.31-1.61]). In this secondary analysis of the PART trial, temporal increases in EtCO2 were associated with increased odds of ROSC. These results suggest value in leveraging continuous waveform capnography during OHCA resuscitation. ClinicalTrials.gov Identifier: NCT02419573.

Transnasal Humidified Rapid Insufflation Ventilatory Exchange in Endoscopic Esophageal Surgery.

Transnasal humidified rapid insufflation ventilatory exchange (THRIVE) describes apneic oxygenation using humidified high flow nasal-cannula oxygen. Although it has been described as a sole mode of oxygenation in endoscopic laryngotracheal surgery, its use in endoscopic esophageal surgery under general anesthesia with neuromuscular paralysis has not previously been described. The objective of this study is to assess the safety and efficacy of THRIVE in esophagology. We conducted a retrospective review of adult patients undergoing esophageal procedures under general anesthesia who were oxygenated using THRIVE at two academic institutions. Demographic, clinical, and anesthesiologic data were collected and analyzed. 14 cases performed from March 2021 to March 2022 met inclusion criteria. 13/14 (92.9%) of patients were able to maintain oxygenation throughout the entirety of their procedure. The mean apneic time was 17.9 minutes with a maximum of 32 minutes. One patient required "rescue" intubation due to failure to maintain oxygenation. Excluding the sole THRIVE failure, the median SpO2 at the conclusion of surgery was 99% (range 94-100%). A linear regression model yielded an increase in EtCO2 of 0.95 mmHg/min or 0.127 kPa/min. SpO2 was negatively associated with both tobacco pack-year smoking history (R2 = 0.343, P = .014) and BMI (R2 = 0.238, P = .038). THRIVE is a feasible, safe, and efficacious means of apneic oxygenation for patients undergoing esophageal endoscopic surgery under general anesthesia with neuromuscular paralysis, which may be particularly beneficial in patients with airway stenosis, as post-intubation changes can have severe clinical implications for this patient population. Obese patients and tobacco smokers may be at increased risk of oxygen desaturation when using THRIVE.

Out-of-hospital cardiac arrest treated with prehospital double sequential external defibrillation during eCPR in refractory VF — a case report

BackgroundDouble sequential external defibrillation (DSED) has demonstrated increased survival with good neurological outcome in a recent randomized controlled trial. DSED has not been studied in patients with extracorporeal cardiopulmonary resuscitation (eCPR).CaseWe present the first case of prehospital eCPR with ongoing refractory ventricular fibrillation (VF), terminated by DSED. After six shocks, return of spontaneous circulation was initially achieved; however, the patient went into recurrent VF. ECPR was performed prehospital, with VF still refractory after three more shocks. DSED successfully terminated VF and showed a further increase in etCO2 and near-infrared spectroscopy cerebral oximetry values.ConclusionDSED can be a sufficient strategy for patients in refractory VF while on eCPR and should be evaluated in further studies.

Effect of Tourniquet Deflation on Intracranial Pressure Measured by Ultrasound of the Optic Nerve Sheath Diameter in Patients Undergoing Orthopedic Surgery Under Spinal Anesthesia: An Observational Study.

Background Orthopedic surgeries of the lower extremities frequently require exsanguination and the use of pneumatic tourniquets. However, the deflation of the tourniquet is accompanied by predominant metabolic changes such as an increase in PaCO2. Prior studies have reported the existence of a correlation between tourniquet deflation and an increase in intracranial pressure in patients undergoing surgery under general anesthesia. However, there is a dearth of literature demonstrating such relationships among patients undergoing surgery under subarachnoid block in the Indian setting. The present research was conducted to study the variations in intracranial pressure after the deflation of the tourniquet by measuring the optic nerve sheath diameter (ONSD) using ultrasound among patients undergoing orthopedic surgery of the lower limb under spinal anesthesia at a tertiary care hospital in eastern India. Methodology After obtaining clearance from the Institutional Ethics Committee, this prospective observational study was conducted among 45 patients undergoing orthopedic surgeries of the lower limb using a pneumatic tourniquet. Changes in intracranial pressure following tourniquet deflation were recorded by measuring ONSD by ultrasound in these patients. Heart rate (HR), mean arterial pressure (MAP), SpO2, EtCO2, and ONSD were noted 15 minutes before administration of subarachnoid block (T0), just before tourniquet deflation (T1) and at 5, 10, and 15 minutes after tourniquet deflation (T5, T10, and T15, respectively). Results The ONSD varied significantlyat each point of observation (p < 0.05). The ONSDs at 5 and 10 minutes after the deflation of the tourniquet were significantly greater than that at T0 (p = 0.002). EtCO2 showed a significant increase compared to baseline values at every point of observation intraoperatively whereas MAP showed a significant decrease (p < 0.05).For all parameters (ONSD, HR, systolic blood pressure, diastolic blood pressure, MAP, and EtCO2), the most significant change in observation was noted at T10, i.e., 10 minutes after the deflation of the tourniquet. Conclusions The significant findingin thisstudy was that the ONSD measurements recorded by ultrasound were increased after the deflation of the tourniquet and that this change can be attributed to an increase in EtCO2. However, the results obtained cannot be validated outside the present research owing to the observational nature of the study and limited sample size. Thus, it is difficult to arrive at a definitive conclusion. Further large-scale multicentric studiesmaybe needed to substantiate the findings of thisstudy.

A Study on Points of Respiratory Assist Devices Using in Pre-Hospital Care Respiratory Assist Devices in Pre-Hospital Care.

In Japan, increasing the number of ambulance requests, the case with the use of respiratory assistance devices in prehospital care by paramedics is also increasing1. When patient experiences respiratory failure, the first responders frequently select a respiratory assist device (RAD) such as Bag Valve Mask (BVM), Jackson Rees (JR), or BVM with Gas Supply Valve® (BVM+GSV). This is based on both evaluation and experience as there is no study indicating which RAD is the best choice at the pre-hospital emergency site. This study clarified the precautions when using BVM, JR, and BVM+GSV in pre-hospital emergency medical care with healthy volunteers. Twenty healthy adults were fitted with a RAD while breathing spontaneously, and changes in vital signs and ETCO2 were observed. The level of ETCO2 became elevated after each RAD was attached. The value was significantly higher in the JR group than in the others. The study showed that even in the presence of spontaneous breathing, ETCO2 increased markedly with the application of respiratory assist devices that are used in pre-hospital care for conditions such as hypoxemia and ventilatory disturbance. The increase in ETCO2 was particularly significant in the JR group, suggesting the need for caution when selecting JRs for pre-hospital care. As the number of subjects was only 20 for each RAD, studies with a larger sample size are needed.

ROLE OF CAPNOGRAPHY IN SAFE SEDATION OF VITRECTOMY PATIENTS

Purpose: To evaluate the efficiency of the capnography monitoring added to routine monitoring on oxygen desaturation, hypoxemia, and other vital parameters. Methods: 100 adult patients who had elective vitrectomy under sedation were included in this study. Patients were divided into “experiment”(capnography added to routine monitoring) and “control”(capnography not added to routine monitoring) groups. Hypoxemia, desaturation, tachycardia, bradycardia, additional maneuvers for the airway were compared. Increase and decrease in end-tidal carbon dioxide (EtCO2) levels, hypoxemia, desaturation, Integrated Pulmonary Index (IPI) levels requiring attention (5-7), and intervention (1-4) were determined in the experiment group, and frequencies of them were assessed. Results: Desaturation and bradycardia rates and counts in the experiment group were significantly lower than the control group. No significant difference was seen between groups in terms of hypoxemia, tachycardia, and additional maneuvers. 76%(38/50) of experiment group patients had decrease in EtCO2, 10%(5/50) increase in EtCO2, 38%(19/50) apnea, 52%(26/50) IPI levels requiring attention, 14%(7/50) IPI levels requiring intervention. Conclusion: With addition of the capnography to routine monitoring of sedated vitrectomy patients, oxygen desaturation and bradycardia can be less likely to occur, and with instant follow-up of the EtCO2, apnea, and IPI levels; respiratory depression can be recognized before oxygen desaturation develops.

Increase in end-tidal carbon dioxide after defibrillation predicts sustained return of spontaneous circulation during out-of-hospital cardiac arrest

IntroductionGuidelines recommend monitoring end-tidal carbon dioxide (ETCO2) during out-of-hospital cardiac arrest (OHCA), though its prognostic value is poorly understood. This study investigated the relationship between ETCO2 and return of spontaneous circulation (ROSC) after defibrillation in intubated non-traumatic OHCA patients. MethodsThis retrospective, observational cohort analysis included adult OHCA patients who received a defibrillation shock during treatment by an urban EMS agency from 2015 to 2021. Peak ETCO2 values were determined for the 90-second periods before and after the first defibrillation in an intubated patient (shock of interest [SOI]). Values were analyzed for association between the change in ETCO2 from pre- to post-shock and the presence of ROSC on the subsequent pulse check. ResultsOf 518 eligible patients, mean age was 61, 72% were male, 50% had a bystander-witnessed arrest, and 62% had at least one episode of ROSC. The most common arrest etiology was medical (92%). Among all patients, peak ETCO2 during resuscitation prior to SOI was 36.8 mmHg (18.6). ETCO2 increased in patients who achieved ROSC immediately after SOI (from 38.3 to 47.6 mmHg; +9.3 CI: 6.5, 12.1); patients with sustained ROSC experienced the greatest increase in ETCO2 after SOI (from 37.8 to 48.2 mmHg; +10.4 CI: 7.2, 13.6), while ETCO2 in patients who did not achieve ROSC after SOI rose (from 36.4 to 37.8 mmHg; +1.4 CI: −0.1, 2.8). ConclusionsETCO2 rises after defibrillation in most patients during cardiac arrest. Patients with sustained ROSC experience larger rises, though the majority experience rises of less than 10 mmHg.

Comparison of End-Tidal Carbon Dioxide (ETCO2) Gradient and Vena Cava Collapsibility Index (VCCI) in Response to Intravenous Fluid Therapy in Patients with Moderate and Severe Dehydration and Acute Gastroenteritis

Acute gastroenteritis (AGE) is one of the most common clinical diagnoses globally, and dehydration in severe AGE cases can cause severe morbidity and mortality. Depending on the metabolic acidosis that occurs in dehydration, the respiratory rate per minute is increased, and the carbon dioxide pressure in the arterial blood is decreased. This condition correlates with end-tidal carbon dioxide (ETCO2). Therefore, this study primarily aims to evaluate whether ETCO2 measurement has a role in detecting metabolic fluid deficit, dehydration level, and regression in dehydration level after fluid replacement and its correlation with Vena Cava Collapsibility Index (VCCI). This study included spontaneously breathing patients admitted to the emergency department of a tertiary training and research hospital with symptoms of AGE and were thought to be moderately (6.0%-9.0%) and severely (>10.0%) dehydrated according to the Primary Options of Acute Care (POAC) Clinical Dehydration Scale. After the first evaluation, the patients' vital signs, ETCO2 values, diameters of the inferior vena cava (IVC) in inspiration and expiration, and VCCI were measured and recorded. These measurements were repeated after intravenous (IV) fluid replacement, and finally, a comparison was made between the measurements. A total of 49 patients, as 16 male (32.7%) and 33 female (67.3%), were included in the study. The mean fluid replacement value was calculated as 664.29 (SD = 259.41) ml. The mean increase in ETCO2 was 3.653 (SD = 2.554) mmHg (P <.001). The mean increase in inferior vena cava expirium (IVCexp) was calculated as 0.402 (SD = 0.280) cm (P <.001) and the mean increase in inferior vena cava inspirium (IVCinsp) as 0.476 (SD = 0.306) cm (P <.001). The VCCI (%) decreased by 12.556 (SD = 13.683) (P <.001). Post-replacement vital signs, ETCO2, and VCCI correlations of the patients were examined and no significant correlation was found between ETCO2 and VCCI (%). As a result of this study, a receiver operating characteristic (ROC) curve was established for the ETCO2 values predicting the level of dehydration and fluid response, and the area under the curve was calculated as 0.748. However, to classify the patient as moderately dehydrated, the ETCO2 cutoff value was determined as 28.5mmHg. The sensitivity and specificity of ETCO2 levels were 71.43% and 74.29% in evaluating the level of dehydration, and no correlation was found with VCCI, which is known to have high sensitivity and specificity in previous studies in determining the level of dehydration and fluid response. Hence, VCCI measurement made through ultrasonography (USG) is a method that should be preferred more in determining the level of dehydration. Nevertheless, as per the results of this study, swift ETCO2 measurements may be helpful in monitoring the change in the degree of dehydration with treatment in patients who were admitted to the emergency department with dehydration findings and were administered IV fluid replacement therapy.

Oxygen efficient respiratory Aid (OxEraTM) device: A safety study.

Severe Coronavirus Disease 2019 (COVID-19) can develop pneumonia with severe complications. The Oxygen Efficient Respiratory Aid (OxEraTM) device has been granted SAPHRA approval for emergency COVID-19 pandemic use. The device has the potential to be used widely in the healthcare sector due to its efficient oxygen supply and adjustable wall positive expiratory pressure (PEP). We assessed whether the OxEraTM device was safe to use in a healthy adult volunteer population. Our primary objective was to ensure there was no asphyxiation, as assessed by changes observed from baseline End Tidal Carbon Dioxide (ETCO2) exceeding 6.3mmHg and above the 45mmHg threshold. We also monitored changes in vital organ signs and assessed the pain and comfort of the participant at various intervals with changes in PEPs. This was an experimental safety study of the OxEraTM Device on 30 healthy participants at the ICU training centre of Chris Hani Baragwanath Academic Hospital, Johannesburg, South Africa. Each participant had basic vital-signs, ETCO2, and Oxygen saturation percentages (SpO2%) taken at baseline until the end of 2h. In the first 20min, the PEP was increased by 5cmH20 until 20min, then continued for the rest of the time on a PEP of 5cmH20. At each interval, vital signs, subjective comfort, pain, and visual scores were measured. Thirty healthy participants were enrolled. There was no significant difference in ETCO2 from baseline until 2h. No participant experienced an increase in measured ETCO2 greater than 45mmHg and no increase in ETCO2 from baseline was greater than 6.3mmHg. The median increase in ETCO2 over the study period was 2mmHg. There were no significant changes in respiratory rate and blood pressure. The heart rate decreased significantly (73-68bpm). The VAS and comfort score had a significant increase over the 2h from baseline of 0-2 at maximum; however, the PAS scores showed no significant increase. Overall the OxEraTM device achieved the safety endpoints set out. There was no sign of asphyxiation and there were appropriate physiological responses to changes in PEP once applied. The comfort of the mask did worsen over the 2h; however, the scores were minimally worse on PEP application but improved once-off PEP. No adverse event was recorded at all.

Physiological Effects of Wearing N95 Respirator on Medical Staff During Prolong Work Hours in Covid-19 Departments.

The objective of the current study was to determine gas exchange abnormalities and physiological changes among healthcare workers during a 4-hour emergency department (ED) shift while wearing the N95 respirator. Single-center prospective observational study. Comparisons of paired measurements were performed using a non-parametric Wilcoxon matched-pairs signed-rank test. Results: Forty-one subjects were included. Prolonged N95 respirator use was associated with a significant decline in plasma pH (7.35 mmHg vs 7.34 mmHg, P = 0.02), PvO 2 (23.2 mmHg vs 18.6 mmHg, P < 0.001) and a concurrent increase in EtCO 2 (32.5 mmHg vs 38.5 mmHg, P < 0.0001). PvCO 2 and bicarbonate levels did not differ. No significant change was observed for heart rate or oxygen saturation. Using an N95 respirator for prolonged periods by healthcare professionals may provoke changes in gas exchange. The clinical significance of these changes remains to be determined.

Chest compression release velocity: An independent determinant of end-tidal carbon dioxide in out-of-hospital cardiac arrest.

Chest compression (CC) depth, CC rate and ventilatory rate (VR) are known to have an impact on end-tidal carbon dioxide (ETCO2) values. Chest compression release velocity (CCRV) is increasingly acknowledged as a novel metric in cardiopulmonary resuscitation (CPR). The objective of this study was to analyze whether CCRV would have any effect on ETCO2 values. In out-of-hospital cardiac arrests (OHCA), effects of CC depth, CC rate, CCRV and VR on ETCO2 were analyzed through linear mixed effect models. A stratification was made on a CCRV of 300, 400 and 500 mm/s. In these categories, mean ETCO2 values were corrected for CC depth and compared through a one-way ANOVA. A 10 mm increase in CC depth was associated with a 1.5 mmHg increase in ETCO2 (p < 0.001), a 100 mm/s increase in CCRV with a 0.8 mmHg increase (p = 0.010) and a 5 breaths per minute increase in VR with a 2.0 mmHg decrease (p < 0.001). CC depth was strongly correlated with CCRV (Pearson's r = 0.709, p < 0.001). After adjusting for CC depth, ETCO2 was on average 6.5 mmHg higher at a CCRV of 500 than at 400 mm/s (p = 0.005) and 5.3 mmHg higher than at 300 mm/s (p = 0.033). In OHCA patients, higher CCRV values resulted in higher ETCO2 values. This effect is independent of CC depth, despite the strong correlation between CCRV and CC depth.

The association between end-tidal CO2 and return of spontaneous circulation after out-of-hospital cardiac arrest with pulseless electrical activity

IntroductionEnd-tidal carbon dioxide (ETCO2) has been suggested to have prognostic implications during out-of-hospital cardiac arrest (OHCA). Our objective was to determine if the change in ETCO2 (delta ETCO2) during resuscitation was predictive of future return of spontaneous circulation (ROSC) in patients with pulseless electrical activity (PEA) arrests. MethodsWe performed a retrospective, observational study of adult (≥18 years of age) non–traumatic PEA OHCAs in two Canadian EMS systems over a two-year time frame beginning on January 1, 2018. Cases were excluded if there was a Do Not Resuscitate order (DNR), had no advanced airway, or had less than two ETCO2 recordings. We performed multivariable logistic regression to examine the association between ETCO2 measures and ROSC. Second, we examined the prognostic performance (sensitivity, specificity, NPV, PPV) for ETCO2 at specific thresholds for predicting ROSC. ResultsA total of 208 OHCA met inclusion criteria of which 67 (32%) obtained ROSC. After adjusting for pre-determined confounders, there was an association between delta ETCO2 and ROSC (odds ratio [OR] per 10 mmHg increase in ETCO2 of 1.74 (95% confidence interval [CI] 1.35 to 2.24); P value < 0.001). We also found significant associations between both initial ETCO2 and final ETCO2 with ROSC. ConclusionOur analysis indicates that there is a positive linear relationship between delta ETCO2 and ROSC with values of delta ETCO2 > 20 mmHg being highly specific for ROSC in PEA patients. As such, patients with up-trending ETCO2 values should have resuscitation continued unless there is overwhelming clinical evidence to the contrary.

Resuscitative endovascular occlusion of the aorta (REBOA) for refractory out of hospital cardiac arrest. An Utstein-based case series

AimsOut of hospital cardiac arrest (OHCA) is still a leading cause of mortality worldwide. In recent years, resuscitative endovascular balloon occlusion of the aorta (REBOA) has been progressively studied as an adjunct to standard advanced life support (ALS) in both traumatic and non-traumatic refractory OHCA.Since January 2019, the REBOA procedure has been applied to all the patients experiencing both traumatic and non-traumatic refractory OHCA (≥15 min of cardiopulmonary resuscitation) not eligible for ECPR for clinical or logistic reasons.We aimed at describing the feasibility and effects of REBOA performed both in the Emergency Department and in the pre-hospital environment served by the local HEMS for refractory OHCA. MethodsTwenty consecutive patients experiencing refractory OHCA and in whom REBOA was attempted in 2019 and 2020 were included in the study, Utstein data and REBOA specific variables were recorded. ResultsSuccessful catheter placement was achieved in 18 out of 20 patients, 11 of these were non-traumatic OHCAs while 7 were traumatic OHCAs, the 2 failures were related to repeated arterial puncture failure.Median time between the EMS dispatch and REBOA catheter placing attempt was 46 min.An increase in etCO2 over 10 mmHg was observed after balloon inflation in 12 out of 18 patients (8/11 non-traumatic and 4/7 traumatic OHCAs), a sustained ROSC was observed in 5 patients (1 traumatic and 4 non-traumatic OHCA) that were subsequently admitted to the ICU. Four out of the 5 patients reached the criteria for brain death in the subsequent 24 h while one patient experienced another episode of refractory cardiac arrest in ICU and subsequently died. ConclusionOur data confirm the feasibility of REBOA technique as an adjunct to ALS in both the ED and prehospital phase and most of the treated patients experienced a transient ROSC after balloon inflation while 5 out of 18 experienced a sustained ROSC.However, while in the trauma setting increasing evidence suggests an improved survival when REBOA is applied to refractory OHCA, in non-traumatic OHCA this has yet to be demonstrated and large studies are needed.

476 Sleep-Disordered Breathing is More Predictive than Obesity of Increased Left Ventricular Mass Index in Bariatric Surgery Patients

Abstract Introduction Obesity and obstructive sleep apnea (OSA) are associated with left ventricular hypertrophy and increased cardiovascular risk. Alternatively, the “obesity paradox” describes an improved prognosis from heart failure in obesity, though potentially attributable to confounding/bias. We sought to determine the contributions of obesity and sleep-disordered breathing (SDB) to left ventricular function and morphology in bariatric surgery candidates. Methods Patients undergoing polysomnography prior to bariatric surgery from 2011–2018 had demographic (age, gender, race), anthropometric (body mass index [BMI], neck circumference), comorbidities (atrial fibrillation, coronary artery disease, diabetes, hypertension, hyperlipidemia), echocardiographic and sleep-disordered breathing (apnea-hypopnea index [AHI], peak end-tidal CO2 [etCO2]) variables retrospectively examined. The echocardiographic visit closest to polysomnogram within two years was selected with missing values filled by available values within 6 months. Linear regression assessed the relationship of BMI, AHI, and etCO2 with left ventricular mass index (LVMI) after adjustment of demographics and comorbidities. Echocardiographic measures were logarithm transformed before regression analysis. Coefficients and 95% confidence intervals (CI) were calculated by exponential transformation. The analysis was performed based on an overall significance level of 0.05 using SAS software (version 9.4, Cary, NC). Results The total of 832 patients had 24% males, mean age 48.8±12, 60% white, and BMI:49.4±9.5kg/m2. Ejection fraction (%) was 60.0±7.0, and LVMI (g/m2): 80.9±23.7. In adjusted models, LVMI decreased by 2.1% for each 5kg/m2 increase in BMI (coefficient=0.979, 95%CI 0.961–0.997, p=0.022) and increased by 4.3% for each 5 mmHg increase in etCO2 (coefficient=1.043, 95%CI 1.013–1.073, p=0.005). Without adjustment, patients with AHI ≥ 5 had 15.3% higher LVMI than non-OSA group (coefficient=1.153, 95%CI 1.034–1.286, p=0.011) and moderate/severe OSA was associated with a 7.6% higher LVMI than those with AHI&amp;lt;15 (coefficient 1.076, 95%CI 1.003–1.153, p=0.040), but not statistically significant after adjustment. Conclusion In obese patients, nocturnal hypoventilation rather than obesity may have adverse influences on left ventricular morphology. Future studies should focus on clarifying whether obesity is truly protective in terms of LV mass, i.e. reflective of paradox versus a product of bias. The potential benefit of identifying/treating SDB in bariatric surgery candidates to mitigate cardiovascular risk also deserves further investigation. Support (if any) Cleveland Clinic Transformative Resource Neuroscience Award

Ventilatory response to CO2 with Read's rebreathing method in normal infants.

Methods of evaluating the ventilatory response to CO2 (VRCO2 ) of the respiratory center include the steady-state and the rebreathing method. Although the rebreathing method can evaluate the ventilatory response continuously to gradually increasing CO2 , the rebreathing method has been rarely performed in infants. The aim of this study was to investigate whether we could perform the VRCO2 with the rebreathing method in normal infants. The subjects were 80 normal infants. The gestational age was 39.9 (39.3-40.3) weeks, and the birth body weight was 3142 (2851-3451) grams. We performed the VRCO2 with Read's rebreathing method, measuring the increase in minute volume (MV) in response to the increase in EtCO2 by rebreathing a closed circuit. The value of VRCO2 was calculated as follow: VRCO2 (ml/min/mmHg/kg) = ΔMV/ΔEtCO2 /body weight. We performed the examination without adverse events. The age in days at examination was 3 (2-4), and the examination time was 150 ± 38 s. The maximum EtCO2 was 51.1 (50.5-51.9) mmHg. The value of VRCO2 was 34.6 (29.3-42.8). The intraclass correlation coefficient of the VRCO2 of cases with multiple measurements was 0.79. This study suggests that the rebreathing method can evaluate the ventilatory response to high blood CO2 in a short examination time. We conclude that the rebreathing method is useful even in infants. In the future, we plan to measure the VRCO2 of preterm infants, and evaluate the respiratory center of infants in more detail.

Effect of wearing a face mask on fMRI BOLD contrast

International spread of the coronavirus SARS-CoV-2 has prompted many MRI scanning facilities to require scan subjects to wear a facial covering (“mask”) during scanning as a precaution against transmission of the virus. Because wearing a mask mixes expired air with the subject's inspired air stream, the concentration of inspired carbon dioxide [CO2] is elevated, resulting in mild hypercapnia. Changes in the inspired gas mixture have been demonstrated to alter R2*-weighted Blood Oxygen Dependent (BOLD) contrast. In this study, we investigate a potential for face masking to alter BOLD contrast during a sensory-motor task designed to activate visual, auditory, and sensorimotor cortices in 8 subjects. We utilize a nasal cannula to supply air to the subject wearing a surgical mask in on-off blocks of 90s to displace expired CO2, while the subject performs the sensory-motor task. While only a small fraction (2.5%) of the sensory-motor task activation is related to nasal air modulation, a 30.0% change in gray matter BOLD signal baseline is found due to air modulation. Repeating the scan with mask removed produces a small subject-specific bias in BOLD baseline signal from nasal air supply, which may be due to cognitive influence of airflow or cannula-induced hypoxia. Measurements with capnography demonstrate wearing a mask induces an average increase in ETCO2 of 7.4%. Altogether, these results demonstrate that wearing a face mask during gradient-echo fMRI can alter BOLD baseline signal but minimally affects task activation.

Return to training in the COVID‐19 era: The physiological effects of face masks during exercise

COVID‐19 outbreak has a profound impact on almost every aspect of life. Universal masking is recommended as a means of source control. Routinely exercising in a safe environment is an important strategy for healthy living during this crisis. As sports clubs and public spaces may serve a source of viral transmission, masking may become an integral part of physical activity. This study aimed to assess the physiological effects of wearing surgical masks and N95 respirators during short‐term strenuous workout. This was a multiple cross‐over trial of healthy volunteers. Using a standard cycle ergometry ramp protocol, each subject performed a maximal exercise test without a mask, with a surgical mask, and with an N95 respirator. Physiological parameters and time to exhaustion were compared. Each subject served his own control. Sixteen male volunteers (mean age and BMI of 34 ± 4 years and 28.72 ± 3.78 kg/m2, respectively) completed the protocol. Heart rate, respiratory rate, blood pressure, oxygen saturation, and time to exhaustion did not differ significantly. Exercising with N95 mask was associated with a significant increase in end‐tidal carbon dioxide (EtCO2) levels. The differences were more prominent as the load increased, reaching 8 mm Hg at exhaustion (none vs N95, P = .001). In conclusion, in healthy subjects, short‐term moderate‐strenuous aerobic physical activity with a mask is feasible, safe, and associated with only minor changes in physiological parameters, particularly a mild increase in EtCO2. Subjects suffering from lung diseases should have a cautious evaluation before attempting physical activity with any mask.

Effects of spinal immobilization at 20° on end-tidal carbon dioxide

ObjectiveThe aim was to determine the effect on end-tidal carbon dioxide (ETCO2) of spinal immobilization (SI) at a conventional 0° angle and to investigate the usefulness of immobilization at a 20° angle for preventing possible hypoventilation. MethodsThe study included 80 healthy volunteers, randomly divided into two groups. Spinal backboards and cervical collars were applied in Group 1 using a 0° angle and in Group 2 using a 20° angle, with the head up. SI was continued for 1 h, and ETCO2 values were measured at the 0th, 30th and 60th minute. ResultsThere were no significant differences between the groups in 0th and 30th minute ETCO2. However, after 60th minute, results showed a statistically significant increase in ETCO2 in Group 1 (35.5 mmHg [IQR 25–75:35–38]) compared to Group 2 (34 mmHg [IQR 25–75:33–36]) (p < 0.001). During SI, there was a statistically significant increase in ETCO2 in Group 1 (35 mmHg [IQR 25–75:34–36], 35.5 mmHg [IQR 25–75:34–37] and 36 mmHg [IQR 25–75:35–38] respectively at the 0th, 30th and 60th minute after SI) (p < 0.001) and no change in Group 2. Also, we found statistically significant differences between ΔETCO2 levels in Groups 1 and 2 at all 3 time intervals. ConclusionConventional SI with an angle of 0° led to an increase in ETCO2 while subjects immobilization at a 20° angle maintained their initial ETCO2 values. Immobilization at 20° may prevent decompensation in patients who have thoracic trauma or lung diseases or those who are elderly, pregnant, or obese.

Ventilation Is an Important Confounding Variable When End-Tidal Carbon Dioxide Is Used to Help Guide Cardiopulmonary Resuscitation

Ventilation Is an Important Confounding Variable When End-Tidal Carbon Dioxide Is Used to Help Guide Cardiopulmonary Resuscitation

Cardiorespiratory Stress-Response in Youth with Persistent Post-Concussion Symptoms

ObjectiveTo evaluate cardiorespiratory response to a cognitive/emotional stressor in youth with persistent post-concussion symptoms (PPCS).BackgroundThe mechanisms of PPCS (symptoms lasting &gt; 2 months) are poorly understood, but recent studies have emphasized the interactive effect of biopsychosocial factors during recovery. In particular, emerging evidence points to anomalies in autonomic functioning as a key player in PPCS. Autonomic functioning is best measured under conditions of stress; however, there are no current studies that examine autonomic functioning in response to cognitive/emotional stressors in youth with PPCS. Therefore, the present study sought to examine the autonomic response to a cognitive/emotional stressor as measured by a cardiorespiratory outcome (end-tidal CO2 fraction [ETCO2]) as well as cognitive performance metrics in youth with PPCS.Design/MethodsParticipants included 7 patients diagnosed with concussion and 7 non-injured controls between the ages of 13–25. Participants were administered a modified version of the Paced Auditory Serial Addition Test (PASAT), a neuropsychological task that is known to induce autonomic arousal. ETCO2 data were collected via continuous capnometry recording throughout the task and for 10 minutes after.ResultsAfter the PASAT, PPCS patients’ ETCO2 concentration remained stable over the 10’ post-stress period compared to controls who demonstrated a significant increase in ETCO2 (p &lt; 0.05) after the cognitive/emotional stressor. In general, patients with PPCS performed more poorly on the middle trials of the PASAT compared to controls but comparisons were not significant.ConclusionsPPCS patients demonstrate abnormal cardiorespiratory functioning following a cognitive/emotional stressor in that their ETCO2 concentrations remain chronically low after stress. Results suggest autonomic dysregulation is a promising avenue for future research into the etiology of PPCS.