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.

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.

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.

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.

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.

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.

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.

Determinants of cerebral blood flow velocity change during squat-stand maneuvers.

The large changes in mean arterial blood pressure (MABP) and cerebral blood flow velocity (CBFV) induced by squat-stand maneuvers (SSM) make this approach particularly suited for studying dynamic cerebral autoregulation (CA). However, the role of other systemic determinants of CBFV has not been described and could provide alternative physiological interpretations of SSM results. In 32 healthy subjects (16 female), continuous recordings of MABP (Finometer), bilateral CBFV (transcranial Doppler, MCA), end-tidal CO2 (EtCO2; capnography), and heart rate (HR; electrocardiogram) were performed for 5 min standing at rest, and during 15 SSM at the frequency of 0.05 Hz. A time-domain, multivariate dynamic model estimated the CBFV variance explained by different inputs, corresponding to significant contributions from MABP (P < 0.00001), EtCO2 (P < 0.0001), and HR (P = 0.041). The autoregulation index (ARI; range 0-9) was estimated from the CBFV response to a step change in MABP. At rest, ARI values (typically 5.7) were independent of the number of model inputs, but during SSM, ARI was reduced compared with baseline (P < 0.0001), and the three input model yielded lower values for the right and left MCA (3.4 ± 1.2, 3.1 ± 1.3) when compared with the single-input MABP-CBFV model (4.1 ± 1.1, 3.9 ± 1.0; P < 0.0001). The high coherence of the MABP-CBFV transfer function at 0.05 Hz (typically 0.98) was considerably reduced (around 0.71-0.73; P < 0.0001) when the contribution of CBFV covariates was taken into account. Not taking into consideration other determinants of CBFV, in addition to MABP, could be misleading and introduce biases in physiological and clinical studies.

Bedside estimates of dead space using end-tidal CO2 are independently associated with mortality in ARDS.

PURPOSE: In acute respiratory distress syndrome (ARDS), dead space fraction has been independently associated with mortality. We hypothesized that early measurement of the difference between arterial and end-tidal CO2 (arterial-ET difference), a surrogate for dead space fraction, would predict mortality in mechanically ventilated patients with ARDS. METHODS: We performed two separate exploratory analyses. We first used publicly available databases from the ALTA, EDEN, and OMEGA ARDS Network trials (N = 124) as a derivation cohort to test our hypothesis. We then performed a separate retrospective analysis of patients with ARDS using University of Chicago patients (N = 302) as a validation cohort. RESULTS: The ARDS Network derivation cohort demonstrated arterial-ET difference, vasopressor requirement, age, and APACHE III to be associated with mortality by univariable analysis. By multivariable analysis, only the arterial-ET difference remained significant (P = 0.047). In a separate analysis, the modified Enghoff equation ((PaCO2-PETCO2)/PaCO2) was used in place of the arterial-ET difference and did not alter the results. The University of Chicago cohort found arterial-ET difference, age, ventilator mode, vasopressor requirement, and APACHE II to be associated with mortality in a univariate analysis. By multivariable analysis, the arterial-ET difference continued to be predictive of mortality (P = 0.031). In the validation cohort, substitution of the arterial-ET difference for the modified Enghoff equation showed similar results. CONCLUSION: Arterial to end-tidal CO2 (ETCO2) difference is an independent predictor of mortality in patients with ARDS.

Respiratory performance of humans exposed to moderate levels of carbon dioxide.

In a business as usual scenario, atmospheric carbon dioxide concentration (CO2 ) could reach 950 parts per million (ppm) by 2100. Indoor CO2 concentrations will rise consequently, given its dependence on atmospheric CO2 levels. If buildings are ventilated following current standards in 2100, indoor CO2 concentration could be over 1300 ppm, depending on specific ventilation codes. Such exposure to CO2 could have physiological and psychological effects on building occupants. We conducted a randomized, within-subject study, examining the physiological effects on the respiratory functions of 15 persons. We examined three exposures, each 150 min long, with CO2 of: 900 ppm (reference), 1450 ppm (decreased ventilation), and 1450 ppm (reference condition with added pure CO2 ). We measured respiratory parameters with capnometry and forced vital capacity (FVC) tests. End-tidal CO2 and respiration rates did not significantly differ across the three exposures. Parameters measured using FVC decreased significantly from the start to the end of exposure only at the reduced ventilation condition (p < 0.04, large effect size). Hence, poor ventilation likely affects respiratory parameters. This effect is probably not caused by increased CO2 alone and rather by other pollutants-predominantly human bioeffluents in this work-whose concentrations increased as a result.

Prehospital end-tidal CO2 as an early marker for transfusion requirement in trauma patients.

OBJECTIVE: Below normal end-tidal carbon dioxide measurement (ETCO2) is associated with worse outcomes in sepsis and trauma patients as compared to patients with normal ETCO2. We sought to determine if ETCO2 can be used in the prehospital setting to predict transfusion requirement, operative hemorrhage control, or mortality in the first 24 h after admission for trauma. METHODS: This is a retrospective cohort study at a suburban, academic Level 1 Trauma Center. Patients were sequentially identified as prehospital trauma alerts from a single EMS system which requires, per policy, ETCO2 for all traumas. One year of prehospital data was collected and paired with hospital trauma registry data. Comparisons were made between ETCO2 values for patients who required transfusion, operative blood loss control, or who died, and those who did not. RESULTS: Two hundred thirty-five trauma patients were transported via the study EMS system, of which 105 (44.7%) had documented ETCO2 values. Patient mean age was 60 (SD24) years with 59 (56.2%) male. Three patients were intubated prehospital and seven were intubated in the trauma bay. Mean prehospital ETCO2 for those who needed transfusion, surgery, or died (n = 11) was 25.7 (9.1) compared to 30.6 (7.8) for those who did not (p = 0.049). Optimal cutoff for our population was EtCO2 ≤ 27 with a sensitivity of 72.7% (95% CI 32-93) and specificity of 72.2% (62-81). CONCLUSION: Below normal ETCO2 values were associated with increase need for transfusion, operative intervention, and death. Further study is warranted to determine if ETCO2 outperforms other predictors of severe trauma.

Wearable Transcutaneous CO2 Monitor Based on Miniaturized Nondispersive Infrared Sensor.

Transcutaneous oxygen and carbon dioxide provide the status of pulmonary gas exchange and are of importance in diagnosis and management of respiratory diseases. Though significant progress has been made in oximetry, not much has been explored in developing wearable technologies for continuous monitoring of transcutaneous carbon dioxide. This research reports the development of a truly wearable sensor for continuous monitoring of transcutaneous carbon dioxide using miniaturized nondispersive infrared sensor augmented by hydrophobic membrane to address the humidity interference. The wearable transcutaneous CO2 monitor shows well-behaved response curve to humid CO2 with linear response to CO2 concentration. The profile of transcutaneous CO2 monitored by the wearable device correlates well with the end-tidal CO2 trend in human test. The feasibility of the wearable device for passive and unobstructed tracking of transcutaneous CO2 in free-living conditions has also been demonstrated in field test. The wearable transcutaneous CO2 monitoring technology developed in this research can be widely used in remote assessment of pulmonary gas exchange efficiency for patients with respiratory diseases, such as COVID-19, sleep apnea, and chronic obstructive pulmonary disease (COPD).

Comparison of arterial CO2 estimation by end-tidal and transcutaneous CO2 measurements in intubated children and variability with subject related factors.

Transcutaneous PCO2 (PTCCO2) and end-tidal PCO2 (PETCO2) measurement methods serve as alternatives to arterial PCO2 (PaCO2), providing continuous non-invasive monitoring. The objective of this study was to evaluate the PTCCO2 and PETCO2 methods with actual PaCO2 levels, and to assess the variability of measurements in relation to subject-related factors, such as skin and subcutaneous adipose tissue thickness and presence of pulmonary diseases. PTCCO2, PETCO2 and PaCO2 were measured at the same time in intubated pediatric subjects. Subjects' demographic characteristics, clinical features, laboratory parameters, skin and subcutaneous adipose tissue thickness were identified. The study was carried out on 102 subjects with a total of 1118 values for each method. In patients with non-pulmonary disease, the mean difference between PTCCO2 and PaCO2 was - 0.29 mmHg (± 6.05), while it was 0.44 mmHg (± 6.83) bias between PETCO2 and PaCO2. In those with pulmonary diseases, the mean difference between PTCCO2 and PaCO2 was - 1.27 mmHg (± 8.32), while it was - 4.65 mmHg (± 9.01) between PETCO2 and PaCO2. Multiple linear regression demonstrated that increased subcutaneous adipose tissue thickness, core body temperature and inotropic index were related with higher PTCCO2 values relative to the actual PCO2 values. Other factors, such as skin tissue thickness, presence of pulmonary disease, measurement location and measurement times were non-significant. The PTCCO2 method has higher reliability than the PETCO2 method, and PTCCO2 measurements are not influenced by most subject-related factors; however, core body temperature, inotropic index and subcutaneous adipose tissue thickness can lead to significant differences in PCO2 measurement.

The association between BOLD-based cerebrovascular reactivity (CVR) and end-tidal CO2 in healthy subjects.

Cerebrovascular reactivity (CVR) mapping using CO2-inhalation can provide important insight into vascular health. At present, blood-oxygenation-level-dependent (BOLD) MRI acquisition is the most commonly used CVR method due to its high sensitivity, high spatial resolution, and relatively straightforward processing. However, large variations in CVR across subjects and across different sessions of the same subject are often observed, which can cloud the ability of this promising measure in detecting diseases or monitoring treatment responses. The present work aims to identify the physiological components underlying the observed variability in CVR data. When studying the association between CVR value and the subject's CO2 levels in a total of N = 253 healthy participants, we found that CVR was lower in individuals with a higher basal end-tidal CO2, EtCO2 (slope = -0.0036 ±â€¯0.0008%/mmHg2, p < 0.001), or with a greater EtCO2 change (ΔEtCO2) with hypercapnic condition (slope = -0.0072 ±â€¯0.0018%/mmHg2, p < 0.001). In a within-subject setting, when studying the CVR difference between two repeated scans (with repositioning) in relation to the corresponding differences in basal EtCO2 and ΔEtCO2 (n = 11), it was found that CVR values were lower if the basal EtCO2 or ΔEtCO2 during that particular scan session was greater. The present work suggests that basal physiological state and the level of hypercapnic stimulus intensity should be considered in application studies of CVR in order to reduce inter-subject and intra-subject variations in the data. Potential approaches to use these findings to reduce noise and augment sensitivity are proposed.

Cerebrovascular reactivity mapping using intermittent breath modulation.

Cerebrovascular reactivity (CVR), an index of brain vessel's dilatory capacity, is typically measured using hypercapnic gas inhalation or breath-holding as a vasoactive challenge. However, these methods require considerable subject cooperation and could be challenging in clinical studies. More recently, there have been attempts to use resting-state BOLD data to map CVR by utilizing spontaneous changes in breathing pattern. However, in subjects who have small fluctuations in their spontaneous breathing pattern, the CVR results could be noisy and unreliable. In this study, we aim to develop a new method for CVR mapping that does not require gas-inhalation yet provides substantially higher sensitivity than resting-state CVR mapping. This new method is largely based on resting-state scan, but introduces intermittent modulation of breathing pattern in the subject to enhance fluctuations in their end-tidal CO2 (EtCO2) level. Here we examined the comfort level, sensitivity, and accuracy of this method in two studies. First, in 8 healthy young subjects, we developed the intermittent breath-modulation method using two different modulation frequencies, 6 â€‹s per breath and 12 â€‹s per breath, respectively, and compared the results to three existing CVR methods, specifically hypercapnic gas inhalation, breath-holding, and resting-state. Our results showed that the comfort level of the 6-s breath-modulation method was significantly higher than breath-holding (p â€‹= â€‹0.007) and CO2-inhalation (p â€‹= â€‹0.015) methods, while not different from the resting-state, i.e. free breathing method (p â€‹= â€‹0.52). When comparing the sensitivity of CVR methods, the breath-modulation methods revealed higher Z-statistics compared to the resting-state scan (p â€‹< â€‹0.008) and was comparable to breath-holding results. Next, we tested the feasibility of breath-modulation CVR mapping (6 â€‹s per breath) in 21 cognitively normal elderly participants and compared quantitative CVR values to that obtained with the CO2-inhalation method. Whole-brain CVR was found to be 0.150 â€‹± â€‹0.055 and 0.154 â€‹± â€‹0.032 %ΔBOLD/mmHg for the breath-modulation and CO2-inhalation method, respectively, with a significant correlation between them (y â€‹= â€‹0.97x, p â€‹= â€‹0.007). CVR mapping with intermittent breath modulation may be a useful method that combines the advantages of resting-state and CO2-inhalation based approaches.

Transcutaneous blood gas monitoring among neonatal intensive care units in Japan.

BACKGROUND: This study aimed to investigate the utility of transcutaneous (tc) measurements of partial pressure of oxygen (tcPO2 ) and carbon dioxide (tcPCO2 ) monitoring in neonatal intensive care units (NICUs) in Japan. METHODS: At the end of 2016,we sent a survey questionnaire on tc monitoring to all 106 NICUs registered with the Japanese Neonatologist Association. The questions included usage, subjects, methods, management, and the practical usefulness of tc monitoring. RESULTS: The questionnaire was returned by 69 NICUs (65.1% of response rate). Seventeen institutions (24.6%) measured both tcPCO2 and tcPO2 , and 42 (60.9%) measured tcPCO2 alone. Transcutaneous PCO2 or tcPO2 monitoring was applied for "pre-viable" infants born at 22-23 weeks' gestational age (18.6% vs 23.5%), and infants of <500 g birthweight (30.5% vs 17.6%). The tcPCO2 and tcPO2 monitoring was started at birth in 49.2% and 70.6% of the newborn infants, respectively. The temperature of the sensor was set at <38°C for tcPCO2 in 54.3% and >42°C for tcPO2 in 58.9% of NICUs. The accuracy for tcPO2 was rated as good in 35.3% or moderate in 64.7%, of institutions but or for tcPCO2 as 1.7% or 93.2%of institutions , respectively. CONCLUSION: Transcutaneous monitoring was widely, but limitedly, used for preterm infants. The lower temperature of the tcPCO2 sensor compared to that reported in other developed countries might compromise the accuracy but increase the feasibility of tc monitoring in Japan.

Ultrasound-Guided Chest Compressions in Out-of-Hospital Cardiac Arrests.

BACKGROUND: There is a significant variability in survival rates for cardiopulmonary resuscitation (CPR) in out of-hospital cardiac arrest (OHCA), and some data indicate that ultrasound improves CPR. OBJECTIVES: We evaluated the feasibility of ultrasound for monitoring chest compressions in OHCA. METHODS: We planned a prospective study in patients with an ultrasound-integrated CPR for OHCA. Chest compressions were performed on the intermammillary line (IML), but the position was changed according to the quality of the heart squeezing, evaluated by ultrasound. End-tidal carbon dioxide (ETCO2) was used as the control parameter. Then we compared the area with the highest squeezing with the position of the heart in the chest computed tomography (CT) scans of 20 hospitalized patients. RESULTS: Chest compressions were good, partial, and inadequate on the IML in 58.4%, 48.9%, and 2.8% of cases, respectively. These percentages were 75%, 25%, and 0% after these modifications: none (47.2%), increased depth (8.3%), hands moved on the lower third of the sternum (27.8%), on left parasternal line of the lower part of the sternum (13.9%), and on the center of the sternum (1 case). Accordingly, ETCO2 improved significantly (20.37 vs. 37.10, p < 0.0001). The CT scans showed that the larger biventricular area (BVA) was under the parasternal line of the lower third of the sternum, and the mean distance IML-BVA was 5.7 cm. CONCLUSIONS: Our study has demonstrated that CPR in OHCA can be improved using ultrasound and changing the position of the hands. This finding was connected with the ETCO2 and confirmed by chest CT scans.

Hypoventilation patterns during bronchoscopic sedation and their clinical relevance based on capnographic and respiratory impedance analysis.

Capnography involves the measurement of end-tidal CO2 (EtCO2) values to detect hypoventilation in patients undergoing sedation. In a previous study, we reported that initiating a flexible bronchoscopy (FB) examination only after detecting signs of hypoventilation could reduce the risk of hypoxemia without compromising the tolerance of the patient for this type of intervention. We hypothesize that hypoventilation status could be determined with greater precision by combining thoracic impedance-based respiratory signals, RESP, and EtCO2 signals obtained from a nasal-oral cannula. Retrospective analysis was conducted on RESP and EtCO2 waveforms obtained from patients during the induction of sedation using propofol for bronchoscopic examination in a previous study. EtCO2 waveforms associated with hypoventilation were then compared with RESP patterns, patient variables, and sedation outcomes. Signals suitable for analysis were obtained from 44 subjects, 42 of whom presented indications of hypoventilation, as determined by EtCO2 waveforms. Two subtypes of hypoventilation were identified by RESP: central-predominant (n = 22, flat line RESP pattern) and non-central-predominant (n = 20, RESP pattern indicative of respiratory effort with upper airway collapse). Compared to cases of non-central-predominant hypoventilation, those presenting central-predominant hypoventilation during induction were associated with a lower propofol dose (40.2 ± 18.3 vs. 60.8 ± 26.1 mg, p = 0.009), a lower effect site concentration of propofol (2.02 ± 0.33 vs. 2.38 ± 0.44 µg/ml, p = 0.01), more rapid induction (146.1 ± 105.5 vs. 260.9 ± 156.2 s, p = 0.01), and lower total propofol dosage (96.6 ± 41.7 vs. 130.6 ± 53.4 mg, p = 0.04). Hypoventilation status (as revealed by EtCO2 levels) could be further classified by RESP into central-predominant or non-central-predominant types. It appears that patients with central-predominant hypoventilation are more sensitive to propofol during the induction of sedation. RESP values could be used to tailor sedation management specifically to individual patients.

Two-site regional oxygen saturation and capnography monitoring during resuscitation after cardiac arrest in a swine pediatric ventricular fibrillatory arrest model.

ABSTARCT: To investigate the use of two-site regional oxygen saturations (rSO2) and end tidal carbon dioxide (EtCO2) to assess the effectiveness of resuscitation and return of spontaneous circulation (ROSC). Eight mechanically ventilated juvenile swine underwent 28 ventricular fibrillatory arrests with open cardiac massage. Cardiac massage was administered to achieve target pulmonary blood flow (PBF) as a percentage of pre-cardiac arrest baseline. Non-invasive data, including, EtCO2, cerebral rSO2 (C-rSO2) and renal rSO2 (R-rSO2) were collected continuously. Our data demonstrate the ability to measure both rSO2 and EtCO2 during CPR and after ROSC. During resuscitation EtCO2 had a strong correlation with goal CO with r = 0.83 (p < 0.001) 95% CI [0.67-0.92]. Both C-rSO2 and R-rSO2 had moderate and statistically significant correlation with CO with r = 0.52 (p = 0.003) 95% CI (0.19-0.74) and 0.50 (p = 0.004) 95% CI [0.16-0.73]. The AUCs for sudden increase of EtCO2, C-rSO2, and R-rSO2 at ROSC were 0.86 [95% CI, 0.77-0.94], 0.87 [95% CI, 0.8-0.94], and 0.98 [95% CI, 0.96-1.00] respectively. Measurement of continuous EtCO2 and rSO2 may be used during CPR to ensure effective chest compressions. Moreover, both rSO2 and EtCO2 may be used to detect ROSC in a swine pediatric ventricular fibrillatory arrest model.