End-tidal Carbon Dioxide Pressure Research Articles

Comparison of the Effect of Laryngeal Mask Airway Versus Endotracheal Tube on Airway Management in Pediatric Patients with Tonsillar Hypertrophy

PurposeThe laryngeal mask airway (LMA) has become an important choice in both routine and difficult airway management. We aimed to evaluate the safety and effectiveness of LMA use in pediatric patients with tonsillar hypertrophy. DesignThis study was a randomized controlled trial. MethodsThe study included 100 pediatric patients who had first or second degree tonsillar hypertrophy. Pediatric patients undergoing elective laparoscopic inguinal hernia repair were randomly divided into two groups (n = 50): LMA group and the endotracheal tube (ETT) group. The primary outcomes were ventilation leak volume, peak airway pressure, and partial pressure of end-tidal carbon dioxide (PETco2). Data for primary outcomes were collected before and 5-, 15-, and 25-minute after opening pneumoperitoneum, and on closing the pneumoperitoneum. Complications such as laryngospasm, bronchospasm, desaturation, severe coughing, blood on the device after removal, and sore throat were recorded. FindingsA total of 100 pediatric patients were assessed and 97 eligible patients were randomly assigned to receive an LMA (n = 49) or an ETT (n = 48). There was no statistically significant difference in ventilation leak volume and PETco2 between the LMA and ETT groups (P > .05). Compared with T1-4, peak airway pressure was significantly lower in T0 (LMA group 12.6 ± 0.9, 95% confidence interval 12.2 to 13.0; ETT group 12.8 ± 1.2, 95% confidence interval 12.2 to 13.3; P < .05). The incidences of laryngospasm 11 (22.9%), desaturation 18 (37.5%), and severe coughing 13 (27%) were higher in the ETT group (11 [22.9%] vs 3 [6.1%], 18 [37.5%] vs 6 [12.2%], 13 [27%] vs 3 [6.1%]; P < .05). ConclusionsThe application of LMA has a lower incidence of complications. LMA as an airway device is effective and perhaps superior in appropriate patients.

Investigation of the relationship between end-tidal carbon dioxide and partial arterial carbon dioxide pressure in patients with respiratory distress

The Medical Journal of the Islamic Republic of Iran (MJIRI), is a quarterly and an editorially independent publication owned by Iran University of Medical Sciences and aims to be a publication of international repute for reporting current regional and international adventures in all aspects of the medicine. MJIRI welcomes contributions in this field in the form of original research articles, case reports, letter to the editor, review articles, brief communications, debate articles, and study protocols. <script src=

The effect of hypercapnia on regional cerebral blood flow regulation during progressive lower-body negative pressure.

Previous work indicates that dynamic cerebral blood flow (CBF) regulation is impaired during hypercapnia; however, less is known about the impact of resting hypercapnia on regional CBF regulation during hypovolemia. Furthermore, there is disparity within the literature on whether differences between anterior and posterior CBF regulation exist during physiological stressors. We hypothesized: (a) lower-body negative pressure (LBNP)-induced reductions in cerebral blood velocity (surrogate for CBF) would be more pronounced during hypercapnia, indicating impaired CBF regulation; and (b) the anterior and posterior cerebral circulations will exhibit similar responses to LBNP. In 12 healthy participants (6 females), heart rate (electrocardiogram), mean arterial pressure (MAP; finger photoplethosmography), partial pressure of end-tidal carbon dioxide (PETCO2), middle cerebral artery blood velocity (MCAv) and posterior cerebral artery blood velocity (PCAv; transcranial Doppler ultrasound) were measured. Cerebrovascular conductance (CVC) was calculated as MCAv or PCAv indexed to MAP. Two randomized incremental LBNP protocols were conducted (-20, -40, -60 and -80mmHg; three-minute stages), during coached normocapnia (i.e., room air), and inspired 5% hypercapnia (~ + 7mmHg PETCO2 in normoxia). The main findings were: (a) static CBF regulation in the MCA and PCA was similar during normocapnic and hypercapnic LBNP trials, (b) MCA and PCA CBV and CVC responded similarly to LBNP during normocapnia, but (c) PCAv and PCA CVC were reduced to a greater extent at -60mmHg LBNP (P = 0.029; P < 0.001) during hypercapnia. CBF regulation during hypovolemia was preserved in hypercapnia, and regional differences in cerebrovascular control may exist during superimposed hypovolemia and hypercapnia.

Internal carotid and brachial artery shear-dependent vasodilator function in young healthy humans.

Brachial artery (BA) shear-mediated dilatation is a widely used assessment of vascular function with links to coronary artery health and cardiovascular risk. Cerebral vascular health is often interrogated using cerebrovascular (middle cerebral artery velocity) reactivity to carbon dioxide. We show that endothelium-dependent diameter (dilator) responses are not significantly related between the internal carotid artery (ICA) and BA; nor are endothelium-independent responses. Additionally, ICA endothelium-dependent responses are not related to middle cerebral artery velocity or ICA blood flow reactivity responses to carbon dioxide. Therefore, assessment of large extracranial cerebral artery vascular health should be quantified via methods specific to the vessel, not via peripheral endothelial function or cerebrovascular reactivity to carbon dioxide. This study compared internal carotid artery (ICA) and brachial artery (BA) endothelium-dependent and -independent vasodilation. We hypothesized that endothelium-dependent and -independent vasodilation of the ICA and BA would be neither similar in magnitude nor correlated between vessels. In 19 healthy adults (23±6 years, 24±3kg/m2 , six female), endothelium-dependent dilatation in the ICA was determined via Duplex ultrasound during transiently elevated shear stress caused by increased partial pressure of end-tidal carbon dioxide using dynamic end-tidal forcing (+9mmHg; cerebral flow-mediated dilatation, cFMD). BA endothelium-dependent dilatation was assessed via standard flow-mediated dilatation (FMD). Endothelium-independent dilatation in the ICA and BA was assessed concurrently for 10min following administration of 400µg sublingual glyceryl trinitrate (GTN). Endothelium-dependent vasodilation of the ICA (3.4±2.4%) was lower than (P=0.013) and not correlated to that of the BA (7.9±3.3%; r2 =0.00, P=0.93). Including baseline diameter and shear-rate area under the curve as covariates maintained the difference between cFMD and FMD (3.3±4.2% vs. 7.8±3.8%, P=0.03), while including baseline diameter and baseline shear rate-adjusted area under the curve as covariates abolished it (5.9±3.7% vs. 5.9.8±3.5%, P=0.99). GTN-mediated vasodilation of the ICA (14.3±2.9%) was lower than (P=0.002) and not correlated to that of the BA (25.5±8.8%; r2 =0.12, P=0.19). Adjusting for baseline diameter eliminated the differences in GTN-induced vasodilation (ICA: 20.1±5.8% vs. BA: 20.4±5.5%; P=0.93). Differences in endothelium-dependent responses, and the lack of correlations between arteries, indicates that endothelium-dependent function cannot be assumed to be related across cerebral and peripheral vasculatures in young, healthy humans.

Carbon dioxide elimination pattern in assessing the risk of an unfavorable outcome in cardiac surgery

Aim. To assess the influence of resting partial pressure of end-tidal carbon dioxide (PetCO2) levels on the long-term results of cardiac surgery.Materials and methods. This prospective cohort study included 454 patients with coronary artery disease who underwent elective coronary artery bypass graft surgery. Before surgery, all patients underwent pulmonary function tests, including body plethysmography, lung diffusion capacity assessment and cardiopulmonary exercise testing with the determination of ventilatory and gas exchange parameters, including PetCO2 at rest. The endpoint was the 2-year survival rate after surgery.Results. Parameters characterizing the obstructive breathing pattern, the lung diffusion capacity, and resting PetCO2 levels had a significant predictor value in relation to long-term survival after cardiac surgery. Among the baseline clinical and functional characteristics, a significant influence on long-term results was shown by the EuroSCORE II (OR 1,69 (1,26-2,27), p=0,001). The highest sensitivity and specificity in relation to long-term mortality risk after coronary artery bypass grafting was shown by resting PetCO2 value equal to 31 mm Hg (area under the ROC curve 0,74 (0,64-0,86), p&lt;0,001).Conclusion. The resting PetCO2 level below 31 mm Hg in patients with coronary artery disease showed a significant effect on the increased long-term mortality risk after cardiac surgery, which is important for patients with exercise intolerance.

A clinical trial of volume- versus pressure-controlled intraoperative ventilation during laparoscopic bariatric surgeries.

Intra-operative ventilation is often challenging in patients with morbid obesity undergoing bariatric surgery. To test the noninferiority of pressure-controlled ventilation (PCV) to volume-controlled ventilation (VCV) in respiratory mechanics. Bariatric Surgery Center, Iran. In a randomized open-labeled clinical trial, 66 individuals with morbid obesity undergoing laparoscopic bariatric surgeries underwent intraoperative ventilation with either PCV or VCV. The measurements taken were peak and mean airway pressures (H2O), partial pressure of arterial oxygen (PaO2), partial pressure of arterial carbon dioxide (PaCO2) and end-tidal carbon dioxide (CO2). We additionally collected pulse-oximetric oxygen saturation, inspiratory concentration of oxygen (FiO2), and hemodynamic variables. Data were analyzed with repeated measures over the time of intubation, after peritoneal insufflation, and every 15 minutes, thereafter up to one hour. PCV mode was successful to sustain adequate ventilation in 97% of the patients, which was similar to the 94% success rate of the VCV mode. Peak airway pressure increased 6 cmH2O and end-tidal CO2 rose by 5 mm Hg after abdominal insufflation in both groups (P = .850 and .376). Alveolar-arterial oxygen gradient similarly increased within 30 minutes after tracheal intubation both in PCV and VCV groups, with small trend of being higher in the VCV group. The ratio of dead space to tidal volumes (VD/VT) did not have a meaningful change (P = .724). PCV was noninferior to VCV during laparoscopic bariatric surgery. Either mode of ventilation could be alternatively used during the anesthesia care of these patients.

Music performance anxiety from the challenge and threat perspective: psychophysiological and performance outcomes

BackgroundAlthough many musicians perceive music performance anxiety (MPA) as a significant problem, studies about the psychobiological and performance-related concomitants of MPA are limited. Using the biopsychosocial model of challenge and threat as theoretical framework, we aim to investigate whether musicians’ changes in their psychobiological responses and performance quality from a private to a public performance are moderated by their general MPA level. According to the challenge and threat framework, individuals are in a threat state when the perceived demands of a performance situation outweigh the perceived resources, whereas they are in a challenge state when the perceived resources outweigh the perceived demands. The resources-demands differential (resources minus demands) and the cardiovascular challenge-threat index (sum of cardiac output and reverse scored total peripheral resistance) are the main indices of these states. We postulate that the relationship between general MPA level and performance quality is mediated by these challenge and threat measures.MethodsWe will test 100 university music students reporting general MPA levels ranging from low to high. They will perform privately (i.e., without audience) and publicly (i.e., with an audience) on two separate days in counterbalanced order. During each performance session, we will record their cardiovascular and respiratory activity and collect saliva samples and self-reported measures. Measures of primary interest are self-reported anxiety, the resources-demands differential, the cardiovascular challenge-threat index, sigh rate, total respiratory variability, partial pressure of end-tidal carbon dioxide and the salivary biomarkers cortisol, dehydroepiandrosterone, and alpha-amylase. Both, the participants and anonymous experts will evaluate the performance quality from audio recordings.DiscussionThe results of the planned project are expected to contribute to a more comprehensive understanding of the psychobiology of MPA and of the processes that influence musicians’ individual reactions to performance situations. We also anticipate the findings of this project to have important implications for the development and implementation of theory-based interventions aimed at managing musicians’ anxiety and improving performance quality. Thanks to the use of multimethod approaches incorporating psychobiology, it might be possible to better assess the progress and success of interventions and ultimately improve musicians’ chance to have a successful professional career.Trial registrationNot applicable.

Powered Air Purifying Respirator (PAPR) restores the N95 face mask induced cerebral hemodynamic alterations among Healthcare Workers during COVID-19 Outbreak

Background and aimCOVID-19 pandemic has resulted in an unprecedented increased usage of Personal protective equipment (PPE) by healthcare-workers. PPE usage causes headache in majority of users. We evaluated changes in cerebral hemodynamics among healthcare-workers using PPE. MethodsFrontline healthcare-workers donning PPE at our tertiary center were included. Demographics, co-morbidities and blood-pressure were recorded. Transcranial Doppler (TCD) monitoring of middle cerebral artery was performed with 2-MHz probe. Mean flow velocity (MFV) and pulsatility index (PI) were recorded at baseline, after donning N95 respirator-mask, and after donning powered air-purifying respirator (PAPR), when indicated. End-tidal carbon-dioxide (ET-CO2) pressure was recorded for participants donning PAPR in addition to the N95 respirator-mask. ResultsA total of 154 healthcare-workers (mean age 29 ± 12 years, 67% women) were included. Migraine was the commonest co-morbidity in 38 (25%) individuals while 123 (80%) developed de-novo headache due to N95 mask. Donning of N95 respirator-mask resulted in significant increase in MFV (4.4 ± 10.4 cm/s, p < 0.001) and decrease in PI (0.13 ± 0.12; p < 0.001) while ET-CO2 increased by 3.1 ± 1.2 mmHg (p < 0.001). TCD monitoring in 24 (16%) participants donning PAPR and N95 respirator mask together showed normalization of PI, accompanied by normalization of ET-CO2 values within 5-min. Combined use of N95 respirator-mask and PAPR was more comfortable as compared to N95 respirator-mask alone. ConclusionUse of N95 respirator-mask results in significant alterations in cerebral hemodynamics. However, these effects are mitigated by the use of additional PAPR. We recommend the use of PAPR together with the N95 mask for healthcare-workers doing longer duties in the hospital wards.

Age-related cerebrovascular carbon dioxide reactivity in children with ventricular septal defect younger than 3years.

Impaired cerebrovascular reactivity to carbon dioxide was proposed to contribute to neurological morbidity in children undergoing cardiac surgery. The objective of this study was to assess carbon dioxide reactivity and regional cerebral oxygen saturation in children younger than 3years. This study enrolled children younger than 3years undergoing ventricular septal defect repair. The cohort was divided into three age groups: younger than 6months, 6-12months, and 12-36months. Under steady-state anesthesia, carbon dioxide reactivity was calculated by measuring changes in middle cerebral artery blood flow velocity using transcranial Doppler sonography. Regional cerebral oxygen saturation changes were measured by near-infrared spectroscopy while endtidal carbon dioxide pressure was adjusted from 30 to 45mmHg. Carbon dioxide reactivity showed a statistically significant increasing relationship with age (younger than 6months group: 4.42%±2.73%, 6-12months group: 5.86%±1.91%, 12-36months group: 7.58%±1.49%; P<.001). Regional cerebral oxygen saturation showed a statistically significant increasing relationship with age (younger than 6months group: 65%±6%, 6-12months group: 68%±5%, 12-36months group: 70%±5%; P=.027). Regional cerebral oxygen saturation showed a statistically significant increasing relationship with endtidal carbon dioxide pressure in all children (P<.001). Abnormal carbon dioxide reactivity is prevalent in children younger than 3years and the degree varies according to age.

Evaluation of the Integrated Pulmonary Index\xae during non-anesthesiologist sedation for percutaneous endoscopic gastrostomy

Standard monitoring of heart rate, blood pressure and arterial oxygen saturation during endoscopy is recommended by current guidelines on procedural sedation. A number of studies indicated a reduction of hypoxic (art. oxygenation < 90% for > 15 s) and severe hypoxic events (art. oxygenation < 85%) by additional use of capnography. Therefore, U.S. and the European guidelines comment that additional capnography monitoring can be considered in long or deep sedation. Integrated Pulmonary Index® (IPI) is an algorithm-based monitoring parameter that combines oxygenation measured by pulse oximetry (art. oxygenation, heart rate) and ventilation measured by capnography (respiratory rate, apnea > 10 s, partial pressure of end-tidal carbon dioxide [PetCO2]). The aim of this paper was to analyze the value of IPI as parameter to monitor the respiratory status in patients receiving propofol sedation during PEG-procedure. Patients reporting for PEG-placement under sedation were randomized 1:1 in either standard monitoring group (SM) or capnography monitoring group including IPI (IM). Heart rate, blood pressure and arterial oxygen saturation were monitored in SM. In IM additional monitoring was performed measuring PetCO2, respiratory rate and IPI. Capnography and IPI values were recorded for all patients but were only visible to the endoscopic team for the IM-group. IPI values range between 1 and 10 (10 = normal; 8–9 = within normal range; 7 = close to normal range, requires attention; 5–6 = requires attention and may require intervention; 3–4 = requires intervention; 1–2 requires immediate intervention). Results on capnography versus standard monitoring of the same study population was published previously. A total of 147 patients (74 in SM and 73 in IM) were included in the present study. Hypoxic events occurred in 62 patients (42%) and severe hypoxic events in 44 patients (29%), respectively. Baseline characteristics were equally distributed in both groups. IPI = 1, IPI < 7 as well as the parameters PetCO2 = 0 mmHg and apnea > 10 s had a high sensitivity for hypoxic and severe hypoxic events, respectively (IPI = 1: 81%/81% [hypoxic/severe hypoxic event], IPI < 7: 82%/88%, PetCO2: 69%/68%, apnea > 10 s: 84%/84%). All four parameters had a low specificity for both hypoxic and severe hypoxic events (IPI = 1: 13%/12%, IPI < 7: 7%/7%, PetCO2: 29%/27%, apnea > 10 s: 7%/7%). In multivariate analysis, only SM and PetCO2 = 0 mmHg were independent risk factors for hypoxia. IPI (IPI = 1 and IPI < 7) as well as the individual parameters PetCO2 = 0 mmHg and apnea > 10 s allow a fast and convenient conclusion on patients’ respiratory status in a morbid patient population. Sensitivity is good for most parameters, but specificity is poor. In conclusion, IPI can be a useful metric to assess respiratory status during propofol-sedation in PEG-placement. However, IPI was not superior to PetCO2 and apnea > 10 s.

Evaluating a novel formula for noninvasive estimation of arterial carbon dioxide during post-resuscitation care.

Controlling arterial carbon dioxide is paramount in mechanically ventilated patients, and an accurate and continuous noninvasive monitoring method would optimize management in dynamic situations. In this study, we validated and further refined formulas for estimating partial pressure of carbon dioxide with respiratory gas and pulse oximetry data in mechanically ventilated cardiac arrest patients. A total of 4741 data sets were collected retrospectively from 233 resuscitated patients undergoing therapeutic hypothermia. The original formula used to analyze the data is PaCO2 -est1=PETCO2 +k[(PIO2 -PETCO2 )-PaO2 ]. To achieve better accuracy, we further modified the formula to PaCO2 -est2=k1 *PETCO2 +k2 *(PIO2 -PETCO2 )+k3 *(100-SpO2 ). The coefficients were determined by identifying the minimal difference between the measured and calculated arterial carbon dioxide values in a development set. The accuracy of these two methods was compared with the estimation of the partial pressure of carbon dioxide using end-tidal carbon dioxide. With PaCO2 -est1, the mean difference between the partial pressure of carbon dioxide, and the estimated carbon dioxide was 0.08kPa (SE ±0.003); with PaCO2 -est2 the difference was 0.036kPa (SE ±0.009). The mean difference between the partial pressure of carbon dioxide and end-tidal carbon dioxide was 0.72kPa (SE ±0.01). In a mixed linear model, there was a significant difference between the estimation using end-tidal carbon dioxide and PaCO2 -est1 (P<.001) and PaCO2 -est2 (P<.001) respectively. This novel formula appears to provide an accurate, continuous, and noninvasive estimation of arterial carbon dioxide.

Intracranial-to-central venous pressure gap predicts the responsiveness of intracranial pressure to PEEP in patients with traumatic brain injury: a prospective cohort study

BackgroundMechanical ventilation (MV) with positive end-expiratory pressure (PEEP) is commonly applied in patients with severe traumatic brain injury (sTBI). However, the individual responsiveness of intracranial pressure (ICP) to PEEP varies. Thus, identifying an indicator detecting ICP responsiveness to PEEP is of great significance. As central venous pressure (CVP) could act as an intermediary to transduce pressure from PEEP to ICP, we developed a new indicator, PICGap, representing the gap between baseline ICP and baseline CVP. The aim of the current study was to explore the relationship between PICGap and ICP responsiveness to PEEP.MethodsA total of 112 patients with sTBI undergoing MV were enrolled in this prospective cohort study. ICP, CVP, cerebral perfusion pressure (CPP), static compliance of the respiratory system (Cst), and end-tidal carbon dioxide pressure (PetCO2) were recorded at the initial (3 cmH2O) and adjusted (15 cmH2O) levels of PEEP. PICGap was assessed as baseline ICP - baseline CVP (when PEEP = 3 cmH2O). The patients were classified into the ICP responder and non-responder groups based on whether ICP increment with PEEP adjusted from 3 cmH2O to 15 cmH2O was greater than 20% of baseline ICP. The above parameters were compared between the two groups, and prediction of ICP responsiveness to PEEP adjustment was evaluated by receiver operating characteristic (ROC) curve analysis.ResultsCompared with the non-responder group, the responder group had lower PICGap (1.63 ± 1.33 versus 6.56 ± 2.46 mmHg; p < 0.001), lower baseline ICP, and higher baseline CVP. ROC curve analysis suggested that PICGap was a stronger predictive indicator of ICP responsiveness to PEEP (AUC = 0.957, 95%CI 0.918–0.996; p < 0.001) compared with baseline ICP and baseline CVP, with favorable sensitivity (95.24, 95%CI 86.91–98.70%) and specificity (87.6, 95%CI 75.76–94.27%), at a cut off value of 2.5 mmHg.ConclusionThe impact of PEEP on ICP depends on the gap between baseline ICP and baseline CVP, i.e. PICGap. In addition, PICGap is a potential predictor of ICP responsiveness to PEEP adjustment in patients with sTBI.

Effects of upper extremity aerobic exercise training on oxygen consumption, exercise capacity, dyspnea and quality of life in patients with pulmonary arterial hypertension

BackgroundPulmonary and extrapulmonary impairments are prevalent in pulmonary arterial hypertension (PAH) which is a rare, chronic and progressive disease. ObjectivesTo investigate the effects of upper extremity aerobic exercise training on exercise capacity, oxygen consumption, dyspnea and quality of life in patients with PAH. MethodsIn a prospective, randomized controlled, double-blinded study, eleven patients in training group applied upper extremity aerobic exercise training (50–80% of maximal heart rate), 15–45 min/day, 3 days a week for 6 weeks and 11 patients in control group alternating active upper extremity exercises for the same period. Exercise capacity evaluated using six minute walk test (6MWT), oxygen consumption simultaneously measured during 6MWT using a portable instrument, dyspnea modified Borg scale and Modified Medical Research Council dyspnea scale and quality of life Short Form 36 Health Survey, before and after the exercise training. ResultsBaseline characteristics of groups were similar (p>0.05). Dyspnea (p<0.001) and peak oxygen consumption (p = 0.031) were significantly improved in training group compared the controls. Dyspnea, exercise capacity, peak oxygen consumption, minute ventilation, tidal volume, end tidal carbon-dioxide pressure, and vitality, social functioning and role-physical were significantly improved within training group (p<0.05). Oxygen consumption at anaerobic threshold were significantly decreased within control group (p<0.05). ConclusionsUpper extremity aerobic exercise training improves oxygen consumption, and decreases dyspnea perception. It is a safe and effective intervention in patients with PAH. (ClinicalTrials.gov registration: NCT02371733).

Neurovascular Coupling is Not Attenuated During Reflex‐Mediated Sympathetic Activation via Lower Body Negative Pressure in Humans

IntroductionCerebral blood flow is tightly coupled with local neuronal activation and metabolism (i.e., neurovascular coupling; NVC). Attenuated NVC has been identified in several chronic diseases, including hypertension, but the underlying mechanism(s) remains unknown. Raised peripheral sympathetic vasoconstrictor activity can play a malevolent role in the pathology of hypertension and might also contribute to the blunted NVC as cerebral arteries are autonomic innervated. However, the role of sympathetic nervous system in the regulation of cerebral blood flow remains controversial. Given this, the purpose of the current study was to test the hypothesis that reflex‐mediated sympathetic activation via lower body negative pressure (LBNP) blunts NVC in humans.MethodsNVC was assessed using a visual stimulation protocol (5 cycles of 30 s eyes closed and 30 s of reading) in 10 young and healthy participants (3 women; aged 25 ± 3 years). In a randomized and counterbalanced order, NVC assessments were made under control conditions and during graded sympathetic activation via LBNP at −20 mmHg and −40 mmHg. Posterior (PCA) and middle cerebral artery (MCA) mean blood velocity (vmean) were determined (transcranial Doppler ultrasound). Vertebral artery blood flow (VAflow) was measured using duplex Doppler ultrasound and vessel wall tracking software. Mean arterial pressure (finger photoplethysmography), stroke volume (Modelflow), heart rate (electrocardiogram) and the partial pressure of end‐tidal carbon dioxide (PetCO2; capnograph) were obtained. Data are presented as mean ± SD.ResultsLBNP to −20 mmHg and −40 mmHg evoked an anticipated reduction in stroke volume and increase in heart rate, while mean arterial pressure was unchanged. Prior to visual stimulation, PCAvmean and MCAvmean were not different between control, −20 LBNP and −40 LBNP conditions (P&gt;0.05), while VAflow was reduced at −40 mmHg (P=0.02 vs. control). Under control conditions, the NVC test evoked a robust increase in PCAvmean (Δ22 ± 4%), a modest increase in MCAvmean (Δ10 ± 3%), and a moderate rise in VAflow (Δ14 ± 5%). The magnitude of these responses was unaffected by LBNP at both −20 mmHg and −40mmHg (PCAvmean Δ23 ± 4% and Δ23 ± 4%; MCAvmean Δ10 ± 1% and Δ11 ± 4%; VAflow Δ15 ± 3% and Δ16 ± 6%; P&gt;0.05). PetCO2 decreased at −20 mmHg (37.0 ± 3.1 mmHg) and −40 mmHg (36.3 ± 3.1 mmHg) LBNP trials compared to control (40.2 ± 3.7mmHg; P=0.004).ConclusionIn summary, these findings indicate that reflex‐mediated sympathetic activation via LBNP does not blunt the NVC response in healthy humans.Support or Funding InformationFunding received from Coordination for the Improvement of Higher Education Personnel (Finance Code 001) (MS), the University of Auckland (JPF, JFRP) and the Health Research Council of New Zealand (JPF, JFRP).

Evaluation of cardiorespiratory parameters in dogs undergoing laparoscopic versus open gonadectomy with spontaneous ventilation anaesthesia: a pilot study

This pilot study aims to compare cardiorespiratory parameters in female dogs that underwent either laparoscopic or open elective gonadectomy with spontaneous ventilation anaesthesia. Records of 77 client-owned female dogs were reviewed. Patients were divided into two groups: laparoscopic surgery (L group, n 47) and open abdominal surgery (O group, n 30). The end-tidal carbon dioxide, respiratory rate, oxygen saturation, heart rate, non-invasive arterial blood pressure and length of procedure were recorded and statistically evaluated. Once normality of the sample data has been assessed, equality between the groups was analysed with two-sample Student’s or Welch’s t-test, whether the hypothesis of variance equality, through an F-test, was verified or not. A value of p &lt;0.05 was considered statistically significant. No statistically significant difference was found between groups regarding the end-tidal carbon dioxide, oxygen saturation, respiratory rate, heart rate, systolic and medium arterial pressure values. Mean diastolic pressure was lower in the L group. The procedure length between the two groups was statistically different: laparoscopy was shorter than open surgery. In spontaneously ventilating female dogs, the cardiorespiratory parameters evaluated seem not to be affected by the presence of pneumoperitoneum when intrabdominal pressure is kept between 8 and 10 mmHg. The pilot nature of the study and the shorter laparoscopic surgery length could bias these results. However, in the author’s opinion, these findings confirm the interest of laparoscopy and the small impact of this mini-invasive technique in healthy patients.

Positional Changes in Arterial Oxygen Saturation and End-Tidal Carbon Dioxide at High Altitude: Medex 2015.

Background: Body position alters aspects of pulmonary function in health and disease. Although studies have assessed positional effects on the heart and lungs, little is known about positional changes in gas exchange parameters at high altitude. We hypothesized that following ascent, supine positioning would cause lower oxygen saturation than sitting, partially due to decreased ventilation and increased partial pressure of end-tidal carbon dioxide (Petco2). Materials and Methods: Twenty-eight healthy subjects were studied at sea level and following gradual ascent to 5150 m. After 10 minutes of sitting rest, subjects were studied for 5 minutes each in the sitting, supine, and prone positions with the order randomly assigned. Pulse oximeter oxygen saturation (SpO2), minute ventilation (VE), end-tidal O2 (Peto2) and Petco2, oxygen consumption, and CO2 production were continuously measured. Alveolar ventilation (VA) was calculated from the measured parameters. Results: At high altitude, VE was not affected by body position (12.96 ± 3.09 and 11.54 ± 3.45 L/min in the sitting and supine positions, respectively, p = 0.255). Petco2 increased from sitting to supine (22.8 ± 3.1 to 23.5 ± 3.3 mm Hg, p < 0.005), but VE and Petco2 were not different between the supine and prone positions. Calculated VA was not significantly affected by body position at either sea level or high altitude. SpO2 decreased from 81.3% ± 4.4% sitting to 78.8% ± 6.0% supine (p = 0.025), with a mean positional SpO2 difference of 2.5% ± 4.9% (95% confidence interval 0.6%-4.4%). SpO2 was not different between the supine and prone positions. Twenty-two of 28 subjects had lower SpO2 supine compared with sitting. Conclusions: These results extend earlier low-altitude studies and demonstrate the importance of postural regulation in different environments. As 79% of subjects had lower SpO2 while supine than sitting, control of body position is necessary for SpO2 comparisons at altitude to be meaningful.

The effect of lower intra-abdominal pressure on intracranial pressure measured by optic nerve sheath diameter during laparoscopic surgery

The aim of this study was to show different optic nerve sheath diameters (ONSD) using ultrasonography under different intra-abdominal pressures (IAPs) and to investigate the association between intracranial pressure (ICP) elevation and perioperative hemodynamic parameters. One hundred patients aged 18-80 years with ASA scores I&II were included. All patients received the same anesthesia protocol and were divided into two groups depending on their IAP, Group A (10 mmHg) and Group B (15 mmHg). ONSD, peak (Ppeak) and plateau (Pplateau) airway pressures, end-tidal volume carbon dioxide (ETCO2), heart rate (HR), and mean arterial blood pressure (MAP) were measured before pneumoperitoneum (T0), at the 10th minute of pneumoperitoneum (T1), and at the end of pneumoperitoneum (T2). No differences were determined between the groups in terms of age, gender, anthropometric measurements, ASA scores, underlying disorders, or duration of pneumoperitoneum, surgery, and anesthesia. Group B patients had higher ONSD values at T2 than Group A (5.0±0.2 vs 5.2±0.2) (p

A Comparison of Two Proportions of Remifentanil–Propofol Mixture Administered with Target-Controlled Infusion for Patients Undergoing Colonoscopy

Background: Previous studies have demonstrated the feasibility of a remifentanil–propofol (RP) mixture use in sedation for medical examinations. However, delivery of an RP mixture by target-controlled infusion (TCI) for colonoscopy has not been described. Here, we investigate the appropriate proportion of RP mixed regimens, prepared in two different ratios for colonoscopy. Methods: A retrospective study including patients who received a colonoscopy between May 2018 and January 2019 was conducted. Group 1 and Group 2 were, respectively, administered a mixture of RP at concentrations of 2.5 μg/mL-10 mg/mL and 5.0 μg/mL-10 mg/mL by adjusting a TCI pump with Schneider model to keep the Observer's Assessment of Alertness/Sedation scale between 1 and 2. The primary outcome was to determine the appropriate proportion of RP for the procedure in terms of hemodynamic conditions and adverse events. The secondary endpoints included the total dosage of anesthetics and total times of TCI pump adjustments. Results: A total of 120 patients in Group 1 and 116 patients in Group 2 were eligible for analysis. Several parameters were significantly different between Group 1 and Group 2, with Group 1 having a higher respiratory rate, a lower end-tidal carbon dioxide pressure, fewer patients with hypotension (mean arterial pressure

Lung ventilation impairment in asthma patients with obesity

BA is characterized by more severe course, worse response to standard therapy in obese patients, therefore asthma with obesity is considered not just as comorbidity but as a distinct BA phenotype. Aim. To study the lung ventilation impairment in asthma patients with obesity using capnometry. The tasks are to study parameters of lung ventilation in asthma patients and healthy persons and to compare these parameters in asthma patients depending on the presence of obesity. Materials and methods. The study involved 60 participants (29 men and 31 women) aged 24 to 74 years, the mean age was 52.3 ± 2.7 years, including 30 patients with asthma and 30 healthy subjects. For all participants, body plethysmography and capnometry were performed. Results. The respiratory minute volume and alveolar ventilation volume were higher in asthma patients with obesity, and the volume of dead space ventilation and its fraction in the tidal volume were not substantially different among the groups of patients with BA. Specifically in relation to the gas exchange parameters, it was found that in obese asthmatics, the end-tidal carbon dioxide pressure was significantly increased – 4.8 ± 0.1 kPa compared with non-obese patients 4.3 ± 0.1 kPa, P < 0.05. The end-tidal oxygen concentration was significantly decreased – 15.3 ± 0.2 % compared to normal weight patients 16.0 ± 0.2 %, P < 0.05. Conclusions . Asthma patients with obesity have characteristics that include reduced total lung capacity, inspiratory capacity and forced vital capacity with a higher degree of airways obstruction. These changes lead to lung ventilation impairment with a tendency to carbon dioxide retention, which may be an unfavorable factor for the process of gas exchange with increased oxygen demands for the entire organism in obesity.

Implications of habitual endurance and resistance exercise for dynamic cerebral autoregulation.

What is the central question of this study? Does habitual resistance and endurance exercise modify dynamic cerebral autoregulation? What is the main finding and its importance? To the authors' knowledge, this is the first study to directly assess dynamic cerebral autoregulation in resistance-trained individuals, and potential differences between exercise training modalities. Forced oscillations in blood pressure were induced by repeated squat-stands, from which dynamic cerebral autoregulation was assessed using transfer function analysis. These data indicate that dynamic cerebral autoregulatory function is largely unaffected by habitual exercise type, and further document the systemic circulatory effects of regular exercise. Regular endurance and resistance exercise produce differential but desirable physiological adaptations in both healthy and clinical populations. The chronic effect of these different exercise modalities on cerebral vessels' ability to respond to rapid changes in blood pressure (BP) had not been examined. We examined dynamic cerebral autoregulation (dCA) in 12 resistance-trained (mean±SD, 25±6years), 12 endurance-trained (28±9years) and 12 sedentary (26±6years) volunteers. The dCA was assessed using transfer function analysis of forced oscillations in BP vs. middle cerebral artery blood velocity (MCAv), induced via repeated squat-stands at 0.05 and 0.10Hz. Resting BP and MCAv were similar between groups (interaction: both P≥0.544). The partial pressure of end-tidal carbon dioxide ( ) was unchanged (P=0.561) across squat-stand manoeuvres (grouped mean for absolute change +0.6±2.3mmHg). Gain and normalized gain were similar between groups across all frequencies (both P≥0.261). Phase showed a frequency-specific effect between groups (P=0.043), tending to be lower in resistance-trained (0.63±0.21 radians) than in endurance-trained (0.90±0.41, P=0.052) and -untrained (0.85±0.38, P=0.081) groups at slower frequency (0.05Hz) oscillations. Squat-stands induced mean arterial pressure perturbations differed between groups (interaction: P=0.031), with greater changes in the resistance (P<0.001) and endurance (P=0.001) groups compared with the sedentary group at 0.05Hz (56±13 and 49±11vs. 35±11mmHg, respectively). The differences persisted at 0.1Hz between resistance and sedentary groups (49±12vs. 33±7mmHg, P<0.001). These results indicate that dCA remains largely unaltered by habitual endurance and resistance exercise with a trend for phase to be lower in the resistance exercise group at lower fequencies.