Peak Expiratory Research Articles

The ventilatory depressant actions but not the antinociceptive effects of morphine are blunted in rats receiving intravenous infusion of L-cysteine ethyl ester

This study demonstrates that intravenous infusion of the cell-penetrant thiol ester, L-cysteine ethyl ester (L-CYSee), to adult male Sprague-Dawley rats elicited (a) minor alterations in frequency of breathing, expiratory time, tidal volume, minute ventilation, or expiratory drive but pronounced changes in inspiratory time, end-inspiratory and expiratory pauses, peak inspiratory and expiratory flows, EF50, relaxation time, apneic pause, inspiratory drive and non-eupneic breathing index, (b) minimal changes in arterial blood-gas (ABG) chemistry (pH, pCO2, pO2, SO2) and Alveolar-arterial (A-a) gradient (index of alveolar gas exchange), and (c) minimal changes in antinociception (tail-flick latency). Subsequent injection of morphine (10 mg/kg, IV) elicited markedly smaller effects on the above parameters, ABG chemistry, and A-a gradient in rats receiving L-CYSee, whereas morphine antinociception was not impaired. Infusions of L-cysteine or L-serine ethyl ester (oxygen rather than sulfur moiety), did not affect morphine actions on ABG chemistry or A-a gradient. L-CYSee (250 μmol/kg, IV) injection elicited dramatic changes in ventilatory parameters given 15 min after injection of morphine in rats receiving L-CYSee. Our findings suggest that (a) L-CYSee acts in neurons that drive ventilation, (b) L-CYSee reversal of the adverse actions of morphine on ventilation, ABG chemistry and A-a gradient may be via modulation of intracellular signaling pathways activated by morphine rather than by direct antagonism of opioid receptors since morphine antinociception was not diminished by L-CYSee, and (c) the thiol moiety of L-CYSee is vital to efficacy, (d) intracellular conversion of L-CYSee to an S-nitrosylated form may be part of its mechanism of action.

Application of whole body plethysmography for assessment of pulmonary function in patients with asthma and obesity

The incidence of asthma and obesity is constantly increasing. It is commonly acknowledged that obesity can make asthma more severe and poorly controlled. Conventional spirometry, despite of being a “gold standard” in diagnostics of lung diseases, cannot provide information on residual lung volume and bronchial resistance, which can be a key to understanding the mechanics of spirometric deviations found in asthma-obesity phenotype.The aim. To evaluate pulmonary function in patients with asthma and obesity by non-invasive and safe clinical method – body plethysmography.Methods. 46 women with asthma were enrolled into the study, of which 21 were obese and 25 had normal body weight. 18 women with obesity and 20 women with normal body weight were selected as controls. All the patients were postmenopausal. Body plethysmography was performed with MasterScreen Body device, CareFusion, Germany.Results. Asthma is associated with a decrease in forced vital lung capacity and an increase in residual volume. Also, Gensler index and peak expiration flows at 25, 50, and 75% expiration were decreased. Interestingly, specific effective resistance in patients with asthma without obesity was 30 – 40% higher than in the control group. In patients with asthma and obesity, specific effective resistance was 2,5 times higher than in the control group. Residual volume and bronchial resistance were found to have a strong positive correlation.Conclusion. despite of similar spirometric changes, only asthma in obesity was marked by an increase of specific bronchial resistance. This finding can be related to higher energy load of breathing process in obese asthma.

The impact of posture correction bands on the respiratory function of healthy adults in their twenties: The difference between men and women.

Recently, interest in posture correction has increased in Korea owing to increased smartphone usage. However, there have been no studies to evaluate the impact of wearing a posture correction band with an abdominal band on breathing and respiratory function. A total of 32 healthy adults, consisting of 16 men (mean age: 23.19 ± 2.88) and 16 women (mean age: 19.69 ± 1.49) participated in this study. Pulmonary function tests were conducted before and after wearing posture correction bands. In all the participants, forced vital capacity decreased significantly (P < .05) after wearing a posture correction band. The forced expiratory volume in 1 second and maximal inspiratory pressure decreased slightly (P > .05). The maximal expiratory pressure (MEP) and peak cough flow (PCF) increased slightly (P > .05). When respiratory functions were monitored separately in men and women after wearing a posture correction band, forced vital capacity and forced expiratory volume in 1 second were significantly reduced in men (P < .05). In women, MEP and PCF increased significantly (P < .05). In this study, we confirmed that the posture correction band had an effect on respiratory function. Lung capacity was statistically significantly reduced but was not clinically significant. In addition, in the case of women, it was confirmed that the abdominal band improved the MEP and PCF.

Time-Controlled Adaptive Ventilation Does Not Induce Hemodynamic Impairment in a Swine ARDS Model.

BackgroundThe current standard of care during severe acute respiratory distress syndrome (ARDS) is based on low tidal volume (VT) ventilation, at 6 mL/kg of predicted body weight. The time-controlled adaptive ventilation (TCAV) is an alternative strategy, based on specific settings of the airway pressure release ventilation (APRV) mode. Briefly, TCAV reduces lung injury, including: (1) an improvement in alveolar recruitment and homogeneity; (2) reduction in alveolar and alveolar duct micro-strain and stress-risers. TCAV can result in higher intra-thoracic pressures and thus impair hemodynamics resulting from heart-lung interactions. The objective of our study was to compare hemodynamics between TCAV and conventional protective ventilation in a porcine ARDS model.MethodsIn 10 pigs (63–73 kg), lung injury was induced by repeated bronchial saline lavages followed by 2 h of injurious ventilation. The animals were then randomized into two groups: (1) Conventional protective ventilation with a VT of 6 mL/kg and PEEP adjusted to a plateau pressure set between 28 and 30 cmH2O; (2) TCAV group with P-high set between 27 and 29 cmH2O, P-low at 0 cmH2O, T-low adjusted to terminate at 75% of the expiratory flow peak, and T-high at 3–4 s, with I:E > 6:1.ResultsBoth lung elastance and PaO2:FiO2 were consistent with severe ARDS after 2 h of injurious mechanical ventilation. There was no significant difference in systemic arterial blood pressure, pulmonary blood pressure or cardiac output between Conventional protective ventilation and TCAV. Levels of total PEEP were significantly higher in the TCAV group (p < 0.05). Driving pressure and lung elastance were significantly lower in the TCAV group (p < 0.05).ConclusionNo hemodynamic adverse events were observed in the TCAV group compared as to the standard protective ventilation group in this swine ARDS model, and TCAV appeared to be beneficial to the respiratory system.

Analysis of Respiratory Muscle Training in Basketball Athletes from APAB Blumenau

The present study has as main objective to analyze the effects of respiratory muscle training on pulmonary function of basketball players in the city of Blumenau-SC. Respiratory muscle training (RMT) improves strength and endurance, and consequently improves athlete performance. However, few studies have analyzed the effects of RMT on the pulmonary function of athletes, especially in non-aquatic sports. Participating in the sample were 10 male athletes, between 19 and 26 years old, mean age of 23 years old, of the basketball team of the Association of Parents and Friends of Basketball (APAB). They were evaluated before and after the RMT application through a Clement Clarke brand One Flow portable digital spirometer. RMT was performed two to four times a week for eight weeks, totaling 16 sessions. Based on the results, it can be concluded that the RMT in basketball athletes presented a significant increase in the pulmonary function assessed by the Expiratory Flow Peak (EFP). Because EFP is related to expiratory force, training has proven to be very effective on expiratory muscles. However, it had no effect on the Forced Expiratory Volume in the first second (FEV1) and Forced Vital Capacity (FVC) variables.

Altered Expiratory Flow Dynamics at Peak Exercise in Adult Men With Well-Controlled Type 1 Diabetes

Type 1 diabetes may, in time, cause lung dysfunction including airflow limitation. We hypothesized that ventilatory flow morphology during a cardiopulmonary exercise test (CPET) would be altered in adult men with well-controlled type 1 diabetes. Thirteen men with type 1 diabetes [glycated hemoglobin A1c 59 (9) mmol/mol or 7.5 (0.8)%, duration of diabetes 12 (9) years, and age 33.9 (6.6) years] without diagnosed diabetes-related complications and 13 healthy male controls [age 37.2 (8.6) years] underwent CPET on a cycle ergometer (40 W increments every 3 min until volitional fatigue). We used a principal component analysis based method to quantify ventilatory flow dynamics throughout the CPET protocol. Last minute of each increment, peak exercise, and recovery were examined using linear mixed models, which accounted for relative peak oxygen uptake and minute ventilation. The type 1 diabetes participants had lower expiratory peak flow (P = 0.008) and attenuated slope from expiration onset to expiratory peak flow (P = 0.012) at peak exercise when compared with the healthy controls. Instead, during submaximal exercise and recovery, the type 1 diabetes participants possessed similar ventilatory flow dynamics to that of the healthy controls. In conclusion, men with relatively well-controlled type 1 diabetes and without clinical evidence of diabetes-related complications exhibited attenuated expiratory flow at peak exercise independently of peak oxygen uptake and minute ventilation. This study demonstrates that acute exercise reveals alterations in ventilatory function in men with type 1 diabetes but not until peak exercise.

Expiratory Peak Flow and Minute Ventilation Are Significantly Increased at High Altitude versus Simulated Altitude in Normobaria.

Simulated altitude (normobaric hypoxia, NH) is used to study physiologic hypoxia responses of altitude. However, several publications show differences in physiological responses between NH and hypobaric conditions at altitude (hypobaric hypoxia, HH). The causality for these differences is controversially discussed. One theory is that the lower air density and environmental pressure in HH compared to NH lead to lower alveolar pressure and therefore lower oxygen diffusion in the lung. We hypothesized that, if this theory is correct, due to physical laws (Hagen-Poiseuille, Boyle), resistance respectively air compression (Boyle) at expiration should be lower, expiratory flow higher, and therefore peak flow and maximum expiratory flow (MEF) 75–50 increased in hypobaric hypoxia (HH) vs. normobaric hypoxia (NH). To prove the hypothesis of differences in respiratory flow as a result of lower alveolar pressure between HH and NH, we performed spirography in NH at different simulated altitudes and the corresponding altitudes in HH. In a cross over study, 6 healthy subjects (2 f/4 m, 28.3 ± 8.2 years, BMI: 23.2 ± 1.9) performed spirography as part of spiroergometry in a normobaric hypoxic room at a simulated altitude of 2800 m and after a seven-hour hike on a treadmill (average incline 14%, average walking speed 1.6 km/h) to the simulated summit of Mauna Kea at 4200 m. After a two-month washout, we repeated the spirometry in HH on the start and top of the Mauna Kea hiking trail, HI/USA. Comparison of NH (simulated 4200 m) and HH at 4200 m resulted in increased pulmonary ventilation during exercise (VE) (11.5%, p < 0.01), breathing-frequency (7.8%, p < 0.01), peak expiratory flow PEF (13.4%, p = 0.028), and MEF50 (15.9%, p = 0.028) in HH compared to NH, whereas VO2max decreased by 2%. At 2800 m, differences were only trendy, and at no altitude were differences in volume parameters. Spirography expresses higher mid expiratory flows and peak flows in HH vs. NH. This supports the theory of lower alveolar and small airway pressure due to a lower air density resulting in a lower resistance.

Aerodynamic measures of patients with tracheostomy capping before and after decannulation

BackgroundGradually stepped decannulation, such as capping with fenestrated tubes or tube downsizing, is likely to prolong the decannulation process. The purpose of the study is to determine the differences in laryngeal aerodynamic measures, expiratory peak flow, and dyspnea index when breathing through the upper airway before and after decannulation. The study recruited sixteen adult patients with a tracheostomy who were fit for decannulation. Measurement of peak flow rate, aerodynamic measures, and dyspnea index has been done at two settings: first during capping and second after decannulation by 2 h using finger support to close the stoma and prevent air leak.ResultsChanges in outcome measures after decannulation revealed a significant increase in peak flow rate, vital capacity, maximum phonation, and phonatory speech pressure level; the glottal resistance significantly decreased after decannulation. The dyspnea severity index scores improved from 22.35 during capping to 13.37 after decannulation.ConclusionsThe results of our study showed that tracheostomy tube capping causes a significant reduction in peak flow and aerodynamic measures which improved after tracheostomy decannulation.

Effect of low dose nebulized morphine on respiratory function improvement in mustard gas-exposed patients: A double-blind crossover clinical trial study.

Background:Mustard is one of the most destructive chemical gases used in chemical warfare. Several studies showed effectiveness of inhaled morphine as a secondary treatment for the improvement of dyspnea. Therefore, this study aimed at determining the efficacy of low dose inhaled morphine for respiratory function improvement in patients who were exposed to the mustard gas.Methods:This study was designed as a cross-over double-blinded clinical trial. Patients exposed to mustard gas were randomly assigned into two groups: 1) received 0.4 mg of morphine by inhalation and 2) received 5 ml of normal saline serum as a placebo in the same manner. After a washout period of one week, the first group received the placebo and the second group received morphine for 5 days. Spirometric indices, expiratory flow peak, exercise test, severity of dyspnea, and quality of life were evaluated as respiratory function parameters. Data analysis was done using SPSS software Version 16.Results:The mean maximum expiratory flow was significantly higher among cases who used morphine in comparison with the placebo group (p<0.05). Moreover, the severity of dyspnea, quality of life, and the frequency of coughing during the day were significantly improved among the recipients of morphine (p<0.05) while the spirometric indices and exercise tolerance tests were similar between the two groups (p>0.05), but the mean peak expiratory flow (PEFR) was significantly higher among the patients receiving morphine than the placebo patients (p<0.001).Conclusion:The use of inhaled morphine had a significant positive effect on the respiratory system of people exposed to mustard gas. We can use low doses of inhaled morphine to improve the respiratory function of these patients as a secondary therapy.

Post-COVID-19 pulmonary function tests in young health care workers in South Indian population – An observational study

Background: The risk of exposure to COVID-19 pandemic was substantially higher in frontline young health care workers. Due to repeated exposure while treating patients, the viral load is exponentially higher than the other population. Lungs being the earliest organ to be affected carry more risk of long-term morbidity. Thus, pulmonary function tests (PFTs) on post-COVID young health care workers provide a better view on the impact, recovery and residual effects. Aim and Objectives: The objectives of the study are as follows: (i) To assess the PFT in study group who have recovered from COVID-19 within the past 3 months; (ii) to compare their lung function with that of health care workers who have not been infected by COVID-19; and (iii) to determine obstructive, restrictive or mixed pulmonary changes if any in health care workers after 3 months of recovery. Materials and Methods: This study involving 50 young health care workers was done in the department of pulmonary medicine for a period of 4 months between January and April 2021. The study (mild COVID-19 positive) control group involved 25 participants each. PFT and diffusing capacity of lung for carbon monoxide (DLCO) were measured using computerized spirometer and single breath method. Results were analyzed using Shapiro–Wilk test, Independent sample t test, and Chi-square test. Results: A statistically significant difference was observed among the subjects of case and control group with respect to the level of FEV1 (P &lt; 0.05), FEV1/Forced vital capacity (FVC) (P &lt; 0.01), and FEF. FVC, Peak expiratory flow (PEF), forced expiratory time, DLCO, and peak inspiratory flow (PIF) were not statistically different between the study and control group. (P &gt; 0.05).The 3-month post recovery values were high in males when compared to females, except for PIF, PEF and FEV1%. Conclusion: PFT and DLCO values were normal in young health care workers after 3 months of COVID-19 infection except for a decrease in FEF 25–75%.

Robotic versus laparoscopic median arcuate ligament (MAL) release: a retrospective comparative study.

Multiple retrospective studies have demonstrated the safety and feasibility of laparoscopic median arcuate ligament division with celiac neurolysis for the definitive management of median arcuate ligament syndrome (MALS). This study queries the clinical equipoise of robotic (RMALR) versus laparoscopic MAL release (LMALR) at a high-volume center. A retrospective analysis of consecutive 26 RMALR and 24 LMALR between March 2018 and August 2019 by a single surgeon at a quaternary academic institution was completed. Primary endpoint was postoperative decrease in celiac trunk expiratory peak systolic velocities (PSVs) measured by mesenteric duplex ultrasonography. Secondary outcomes included reported improvement in MALS-related clinical symptoms, distribution of first assistant seniority level, and involvement of second assistants in RMALR versus LMALR. Mean operative times for LMALR and RMALR were 86 and 134min, respectively (p < 0.0001). There were no open conversions and mean length of hospital stay was 1day for both cohorts. Both groups provided an equally effective decrease in postoperative peak systolic velocities (PSVs) (LMALR p = 0.0011; RMALR p = 0.0022; LMALR vs. RMALR p = 0.7772). While RMALR had significantly higher reduction of chronic abdominal pain postoperatively, there were no significant differences in other postoperative symptom relief between groups. However, RMALR patients reported significant relief of postprandial abdominal pain (p < 0.0001) and chronic nausea (p = 0.0002). RMALR had significantly more junior first assistants (p = 0.0001) and less frequently required second assistants compared to LMALR (p = 0.0381). In this study comparing RMALR to LMALR, postoperative chronic abdominal pain relief was significantly less in the former while other outcomes were equivalent. In comparison with LMALR, RMALR cases were associated with more junior first assistants, fewer second assistants, and longer operative times. Both approaches are safe and feasible for well-selected patients in experienced centers.

Study of Nasal Fractional Exhaled Nitric Oxide (FENO) in Children with Allergic Rhinitis

(1) Background: Exhaled nitric oxide (NO) has been considered as a biomarker of airway inflammation. The measurement of fractional exhaled NO (FENO) is a valuable test for assessing local inflammation in subjects with allergic rhinitis (AR). (2) Objective: To evaluate (a) the correlation between nasal FENO with anthropometric characteristics, symptoms of AR and nasal peak flows in children without and with AR; and (b) the cut-off of nasal FENO for diagnosis of AR in symptomatic children. (3) Methods: The study was a descriptive and cross-sectional study in subjects with and without AR &lt; 18 years old. All clinical and functional characteristics of the study subjects were recorded for analysis. They were divided into healthy subjects for the control group and subjects with AR who met all inclusion criteria. (4) Results: 100 subjects (14 ± 3 years) were included, including 32 control subjects and 68 patients with AR. Nasal FENO in AR patients was significantly higher than in control subjects: 985 ± 232 ppb vs. 229 ± 65 ppb (p &lt; 0.001). In control subjects, nasal FENO was not correlated with anthropometric characteristics and nasal inspiratory or expiratory peak flows (IPF or EPF) (p &gt; 0.05). There was a correlation between nasal FENO and AR symptoms in AR patients and nasal IPF and EPF (p = 0.001 and 0.0001, respectively). The cut-off of nasal FENO for positive AR diagnosis with the highest specificity and sensitivity was ≥794 ppb (96.7% and 92.6%, respectively). (5) Conclusion: The use of nasal FENO as a biomarker of AR provides a useful tool and additional armamentarium in the management of allergic rhinitis.

Evaluation of a mechanical lung model to test small animal whole body plethysmography

Whole-body plethysmography (WBP) is an established method to determine physiological parameters and pathophysiological alteration of breathing in animals and animal models of a variety of diseases. Although frequently used, there is ongoing debate about what exactly is measured by whole-body-plethysmography and how reliable the data derived from this method are. Here, we designed an artificial lung model that enables a thorough evaluation of different predictions about and around whole-body plethysmography. Using our lung model, we confirmed that during WBP two components contribute to the pressure changes detected in the chamber: (1) the increase in the pressure due to heating and moistening of the air during inspiration, termed conditioning; (2) changes in the chamber pressure that depend on airway resistance. Both components overlap and contribute to the temporal pressure-profile measured in the chamber or across the wall of the chamber, respectively. Our data showed that a precise measurement of the breathing volume appears to be hindered by at least two factors: (1) the unknown relative contribution of each of these two components; (2) not only the air in the inspired volume is conditioned during inspiration, but also air within the residual volume and dead space that is recruited during inspiration. Moreover, our data suggest that the expiratory negative pressure peak that is used to determine the enhanced pause (Penh) parameter is not a measure for airway resistance as such but rather a consequence of the animal’s response to the airway resistance, using forced or active expiration to overcome the resistance by a higher thoracic pressure.

Contemporary Oyster Reef Restoration: Responding to a Changing World

Globally, there is growing interest in restoring previously widespread oyster reefs to reinstate key ecosystem services such as shoreline protection, fisheries productivity and water filtration. Yet, since peak expiration of oysters in the 1800s, significant and ongoing environmental change has occurred. Estuaries and coasts are undergoing some of the highest rates of urbanization, warming and ocean acidification on the planet, necessitating novel approaches to restoration. Here, we review key design considerations for oyster reef restoration projects that maximize the probability that they will meet biological and socio-economic goals not only under present-day conditions, but into the future. This includes selection of sites, and where required, substrates and oyster species and genotypes for seeding, not only on the basis of their present and future suitability in supporting oyster survival, growth and reproduction, but also based on their match to specific goals of ecosystem service delivery. Based on this review, we provide a road map of design considerations to maximize the success of future restoration projects.

Acute intermittent hypoxia evokes ventilatory long-term facilitation and active expiration in unanesthetized rats

Acute intermittent hypoxia (AIH) modifies the functioning of the respiratory network, causing respiratory motor facilitation in anesthetized animals and a compensatory increase in pulmonary ventilation in freely behaving animals. However, it is still unclear whether the ventilatory facilitation induced by AIH in unanesthetized animals is associated with changes in the respiratory pattern. We found that Holtzman male rats (80–150 g) exposed to AIH (10 × 6% O2 for 30–40 s every 5 min, n = 9) exhibited a prolonged (30 min) increase in baseline minute ventilation (P < 0.05) compared to control animals (n = 13), combined with the occurrence of late expiratory peak flow events, suggesting the presence of active expiration. The increase in ventilation after AIH was also accompanied by reductions in arterial CO2 and body temperature (n = 5–6, P < 0.05). The systemic treatment with ketanserin (a 5-HT2 receptor antagonist) before AIH prevented the changes in ventilation and active expiration (n = 11) but potentiated the hypothermic response (n = 5, P < 0.05) when compared to appropriate control rats (n = 13). Our findings indicate that the ventilatory long-term facilitation elicited by AIH exposure in unanesthetized rats is linked to the generation of active expiration by mechanisms that may depend on the activation of serotonin receptors. In contrast, the decrease in body temperature induced by AIH may not require 5-HT2 receptor activation.

Neonates With Tracheomalacia Generate Auto-Positive End-Expiratory Pressure via Glottis Closure

In pediatrics, tracheomalacia is an airway condition that causes tracheal lumen collapse during breathing and may lead to the patient requiring respiratory support. Adult patients can narrow their glottis to self-generate positive end-expiratory pressure (PEEP) to raise the pressure in the trachea and prevent collapse. However, auto-PEEP has not been studied in newborns with tracheomalacia. The objective of this study was to measure the glottis cross-sectional area throughout the breathing cycle and to quantify total pressure difference through the glottis in patients with and without tracheomalacia. Do neonates with tracheomalacia narrow their glottises? How does the glottis narrowing affect the total pressure along the airway? Ultrashort echo time MRI was performed in 21 neonatal ICU patients (11 with tracheomalacia, 10 without tracheomalacia). MRI scans were reconstructed at four different phases of breathing. All patients were breathing room air or using noninvasive respiratory support at the time of MRI. Computational fluid dynamics simulations were performed on patient-specific virtual airway models with airway anatomic features and motion derived via MRI to quantify the total pressure difference through the glottis and trachea. The mean glottis cross-sectional area at peak expiration in the patients with tracheomalacia was less than half that in patients without tracheomalacia (4.0 ± 1.1mm2 vs10.3 ± 4.4mm2; P= .002). The mean total pressure difference through the glottis at peak expiration was more than 10 times higher in patients with tracheomalacia compared with patients without tracheomalacia (2.88 ± 2.29cm H2O vs0.26 ± 0.16cm H2O; P= .005). Neonates with tracheomalacia narrow their glottises, which raises pressure in the trachea during expiration, thereby acting as auto-PEEP.

Naloxone Injections into the Parabrachial Nucleus/ Kölliker‐Fuse Complex, the preBötzinger Complex and the Caudal Medullary Raphe Reverse Remifentanil‐Induced Respiratory Depression

Background We have shown that naloxone microinjections into the Parabrachial Nucleus/ Kölliker-Fuse (PBN/KF) complex and the preBötzinger Complex (preBC) partially reversed remifentanil-induced respiratory rate depression (1). The magnitude of reversal was dose dependent. The goal of this study was to determine whether additional naloxone injection into the caudal medullary raphe (CMR (2)) could completely reverse the opioid effect. Methods The study was approved by the local Animal Care Committee and conformed to NIH standards. Adult New Zealand White rabbits (3-4kg) were anesthetized, tracheotomized, ventilated, decerebrated and vagotomized. Phrenic nerve activity was recorded from the c5 rootlet, time averaged and used to calculate inspiratory and expiratory duration and peak phrenic activity (PPA). Gridwise localized pressure microinjections of AMPA (50 μM, 70 nl) with a multibarrel glass pipette were used to functionally identify the PBN/KF and preBC. The CMR was defined as the area between 2.0mm caudal and 1.5mm rostral to preBC in the midline. We then injected an “apneic” remifentanil IV bolus (12±2mcg), which interrupted inspiratory activity for at least 60 sec. Next, a remifentanil infusion was started at an “analgesic” dose-rate, defined to achieve respiratory rate depression of 50% of control. At steady-state, we sequentially injected naloxone (1mM, 700nl) into the bilateral PBN/KF, the preBC, and the CMR. We repeated the “apneic” remifentanil bolus after naloxone injection into each area. To determine whether injection order affected the naloxone reversal, in separate sets of animals we microinjected naloxone in the reverse order, or solely into the preBC and CMR. Drug effects were compared with Paired t-tests. Results Figure 1 illustrates the effects of sequential naloxone microinjection into the bilateral PBN/KF, preBC, and CMR. At the end of the naloxone injection sequence, respiratory rate depression was completely reversed (A+B) or even increased above baseline (C). Depression of PPA was completely reversed (p=0.756). Conclusion Naloxone injection into the CMR reversed remifentanil-induced respiratory depression in addition to the reversal achieved in the PBN/KF and preBC at “analgesic” and “apneic” remifentanil doses. Further research is needed to determine whether the naloxone effect in the CMR was partially due to reversal of endogenous opioid-receptor activation (see Palkovic B, Endogenous Opioid-Receptor Activation in the Caudal Medullary Raphe Depresses Respiratory Rate in Decerebrate Rabbits, EB 2021). (1) Palkovic et al., Anesthesiology 2020, A3038 (2) Zhang et al., Anesthesiology 2007, 107: 288-97

Diaphragmatic Kinetics Assessment by Tissue Doppler Imaging and Extubation Outcome.

The assessment of diaphragmatic kinetics through tissue Doppler imaging (dTDI) was recently proposed as a means to describe diaphragmatic activity in both healthy individuals and intubated patients undergoing weaning from mechanical ventilation. Our primary aim was to investigate whether the diaphragmatic excursion velocity measured with dTDI at the end of a spontaneous breathing trial (SBT) was different in subjects successfully extubated versus those who passed the trial but exhibited extubation failure within 48 h after extubation. We enrolled 100 adult subjects, all of whom had successfully passed a 30-min SBT conducted in CPAP of 5 cm H2O. In cases of extubation failure within 48 h after liberation from invasive mechanical ventilation, subjects were re-intubated or supported through noninvasive ventilation. dTDI was performed at the end of the SBT to assess excursion, velocity, and acceleration. Extubation was successful in 79 subjects, whereas it failed in 21 subjects. The median (interquartile range [IQR]) inspiratory peak excursion velocity (3.1 [IQR 2.0-4.3] vs 1.8 [1.3-2.6] cm/s, P < .001), mean velocity (1.6 [IQR 1.2-2.4] vs 1.1 [IQR 0.8-1.4] cm/s, P < .001), and acceleration (8.8 [IQR 5.0-17.8] vs 4.2 [IQR 2.4-8.0] cm/s2, P = .002) were all significantly higher in subjects who failed extubation compared with those who were successfully extubated. Similarly, the median expiratory peak relaxation velocity (2.6 [IQR 1.9-4.5] vs 1.8 [IQR 1.2-2.5] cm/s, P < .001), mean velocity (1.1 [IQR 0.7-1.7] vs 0.9 [IQR 0.6-1.0] cm/s, P = .002), and acceleration (11.2 [IQR 9.1-19.0] vs 7.1 [IQR 4.6-12.0] cm/s2, P = .004) were also higher in the subjects who failed extubation. In our setting, at the end of SBT, subjects who developed extubation failure within 48 h after extubation experienced a greater diaphragmatic activation compared with subjects who were successfully extubated. (ClinicalTrials.gov registration NCT03962322.).

Current practice and evolution of pediatric respiratory management of Duchenne muscular dystrophy in Canada

RATIONALE: Respiratory management practices for Duchenne muscular dystrophy (DMD) vary across Canada, according to a web-based survey conducted in 2010. Since then, new guidelines for respiratory management of DMD have been published. OBJECTIVES: This study aimed to describe current respiratory management practices of Canadian Pediatric Respirologists for children with DMD across the country. METHODS: A web-based survey on timing and indications for respiratory diagnostic tests and interventions was sent to all practicing Pediatric Respirologists at tertiary care centers in Canada who are involved in the longitudinal management of boys with DMD (N = 20). MEASUREMENTS AND MAIN RESULTS: Responses were received from 17 (85%) Pediatric Respirologists. Pulmonary function testing is regularly performed at least twice yearly after 5-6 years of age or after a patient becomes nonambulatory (13/17, 76%). Maximal expiratory pressures (15/17, 88%) and peak cough flow (12/17, 71%) are used to assess respiratory muscle strength. Sleep evaluation is most commonly performed with polysomnography (14/17, 82%), and is requested with the onset of symptoms (14/17, 82%) or with a forced vital capacity (FVC) < 60% predicted (6/9, 67%). At least once-daily lung volume recruitment exercises are prescribed by 94% (16/17) of respondents during periods of clinical stability, with the most common indication being an FVC < 80% predicted (9/17, 53%). CONCLUSIONS: The majority of Canadian Pediatric Respirologists are providing respiratory care to boys with DMD according to the current guidelines. The greatest change over time is the increased usage of regular LVR/airway clearance during periods of clinical stability.

Research on the Accuracy and Speed of Three-Dimensional Reconstruction of Liver Surface Based on Binocular Structured Light

In view of the problem that the doctor cannot quickly obtain the three-dimensional information of the liver surface during the traditional open resection of liver tumor without radiation, a new three-dimensional reconstruction system of liver surface based on binocular structured light is proposed in this paper to obtain three-dimensional information of liver surface rapidly. The hardware construction and software module design of the three-dimensional reconstruction system of the liver surface are carried out. The multi-frequency heterodyne method is proposed to solve the problem of the lack of three-dimensional reconstruction of the liver surface. A GPU-CPU collaborative acceleration method is proposed to speed up the three-dimensional reconstruction of intraoperative liver surface. On this basis, a human respiratory platform is built to simulate the effect of human respiration on three-dimensional reconstruction of the liver surface in a real surgical environment. The accuracy and speed of the system are verified by the liver experiments: The errors of three-dimensional reconstruction of liver surface at expiratory peak and inspiratory peak are 0.78 ± 0.18mm and 0.92 ± 0.21 mm, respectively. The average time required for three-dimensional reconstruction of liver surface based on GPU-CPU collaborative calculation is 3.93s. The speed of three-dimensional reconstruction of liver surface based on GPU-CPU collaborative calculation is 52% faster than that of three-dimensional reconstruction of liver surface based on CPU. It can be seen that the system has high accuracy and fast speed, which can meet the basic needs of the doctor in surgery.