Ventilatory Variables Research Articles

Pressure peaking phenomena: Unignited hydrogen releases in confined spaces – Large-scale experiments

The aim of this study was to validate a model for predicting overpressure arising from accidental hydrogen releases in areas with limited ventilation. Experiments were performed in a large-scale setup that included a steel-reinforced container of volume 14.9 m3 and variable ventilation areas and mass flow rates. The pressure peaking phenomenon, characterized as transient overpressure with a characteristic peak in a vented enclosure, was observed during all the experiments. The model description presented the relationship between the ventilation area, mass flow rate, enclosure volume, and discharge coefficient. The experimental results were compared with two prediction models representing a perfect mix and the real mix. The perfect mix assumed that all the released hydrogen was well stirred inside the enclosure during the releases. The real mix prediction s used the hydrogen concentration and temperature data measured during experiments. The prediction results with both perfect mix and real mix showed possible hazards during unignited hydrogen releases.

A Single 60.000 IU Dose of Erythropoietin Does Not Improve Short-Term Aerobic Exercise Performance in Healthy Subjects: A Randomized, Double-Blind, Placebo-Controlled Crossover Trial.

Erythropoietin (EPO) boosts exercise performance through increase in oxygen transport capacity following regular administration of EPO but preclinical study results suggest that single high dose of EPO also may improve exercise capacity. Twenty-nine healthy subjects (14 males/15 females; age: 25 ± 3 years) were included in a randomized, double-blind, placebo-controlled crossover study to assess peak work load and cardiopulmonary variables during submaximal and maximal cycling tests following a single dose of 60.000 IU of recombinant erythropoietin (EPO) or placebo (PLA). Submaximal exercise at 40%/60% of peak work load revealed no main effect of EPO on oxygen uptake (27.9 ± 8.7 ml min–1⋅kg–1/ 37.1 ± 13.2 ml min–1⋅kg–1) versus PLA (25.2 ± 3.7 ml min–1⋅kg–1/ 33.1 ± 5.3 ml min–1⋅kg–1) condition (p = 0.447/p = 0.756). During maximal exercise peak work load (PLA: 3.5 ± 0.6 W⋅kg–1 vs. EPO: 3.5 ± 0.6 W kg–1, p = 0.892) and peak oxygen uptake (PLA: 45.1 ± 10.4 ml⋅min–1 kg–1 vs. EPO: 46.1 ± 14.2 ml⋅min–1 kg–1, p = 0.344) reached comparable values in the two treatment conditions. Other cardiopulmonary variables (ventilation, cardiac output, heart rate) also reached similar levels in the two treatment conditions. An interaction effect was found between treatment condition and sex resulting in higher peak oxygen consumption (p = 0.048) and ventilation (p = 0.044) in EPO-treated males. In conclusion, in a carefully conducted study using placebo-controlled design the present data failed to support the hypothesis that a single high dose of EPO has a measurable impact on work capacity in healthy subjects.

Indoor Air Pollution and the Risk of Cardiovascular Disease

Objective: To measure an association between factors related to indoor air pollution and CVD in the Hail population of Saudi Arabia.
 Methodology: A case control study was conducted in King Khalid hospitals. Convenience and random sampling techniques were used to recruit cases and controls. Structured Questionnaire was used to collect data from 302 CVD cases and 300 controls. Data analysis was carried out using SPSS 24.0 statistical software.
 Results: The bivariate analysis showed significant association between (i) socio-demographic characteristics (ii) air quality and occupation related variables (iii) ventilation and cooking related factors and (iv) exposure of different types of smoke, and CVD (p<0.001). The independent risk factors of CVD by Multivariate logistic regression analysis with adjusted odds ratios of variables are: age groups (25-50 & >50 years) (2.95&22.84); education level (uneducated & primary) (4.39&2.64); cigarette smoking (1.89); shisha smoking (2.12), exposed to cigarette smoke (2.50); burning scented wood (3.09), burning of mosquito repellent (2.18) and kitchen type (2.83) (p<0.001).
 Conclusions: This study shows various sources of air pollutants are associated with CVD. The composition of indoor and outdoor air is same in Hail city but amount of contaminants is high in indoor environments. Future studies longitudinal studies are required to confirm the findings of this study.

A Critical Exploration of the Efficiency Impacts of Demand Response From HVAC in Commercial Buildings

Increasing quantities of renewable energy generation has yielded a need for greater energy storage capacity in power systems. Thermal storage in variable air volume (VAV) heating, ventilation, and air conditioning (HVAC) in commercial buildings has been identified as an inexpensive source of grid storage, but the true costs are not known. Recent literature explores the inefficiency associated with providing grid services from these HVAC-based demand response (DR) resources by employing a battery analogy to calculate round-trip efficiency (RTE). Results vary significantly across studies and in some cases reported efficiencies are strikingly low. This article has three objectives to address these prior results. First, we synthesize and expand on insights into existing literature by systematically exploring the potential causes for the discrepancies in results. We reinforce previous work indicating baseline modeling may drive differences across studies and deduce that control accuracy plays a role in the major differences between experiments and simulation. Second, we discuss why the RTE metric is problematic for DR applications, discuss another proposed metric, additional energy consumption (AEC), and propose an extension, which we call uninstructed energy consumption (UEC), to evaluate DR performance. Finally, we explore the merits of different metrics using experimental data and highlight UEC’s reduced sensitivity to the characteristics of the DR signal than previously proposed metrics.

How can we simulate the Bi-directional flow and time-variant heat exchange ventilation system?

The aim of this study is to analyze the characteristics and performance of a Bi-directional flow and transient or variable heat exchange ventilator by experiment. In addition, a simulation method to describe the features of this system is proposed. The effect of the degree of simulation modeling for Bi-directional flow and transient or variable heat exchange ventilator on energy demand was analyzed by simulation. The adequacy of simulation modeling was verified in comparison with experimental results. The simulation results of time-variant heat exchange efficiency were in good agreement with the experimental results, within an error range of approximately 0.6%.The difference in energy consumption according to the degree of simulation modeling for Bi-directional flow and transient or variable heat exchange ventilator was found to be up to 22% according to the consideration of the energy consumption of the ventilator fan. There is no difference in simulation results between the method considering the time-variant heat exchange efficiency and the method of applying the time-averaged heat exchange efficiency. The consideration of air infiltration in the exhaust mode increased the heating energy consumed by approximately 5.4% but had little effect on the consumption of cooling energy. The results of this study will be helpful in determining the degree of simulation modeling for performance analyses of a Bi-directional flow and transient heat exchange ventilator.

Efeitos da supressão da aspiração endotraqueal na incidência de complicações pulmonares no pós operatório de cirurgia cardíaca

INTRODUÇÃO: Aspiração traqueal é utilizada rotineiramente após cirurgia cardíaca para garantir adequada ventilação. OBJETIVO: Verificar se a ausência da aspiração traqueal antes da extubação em pacientes sem sinais de secreção brônquica influencia na incidência de complicações pulmonares, além de repercussões hemodinâmicas e ventilatórias do procedimento e custos. MÉTODOS: Pacientes foram avaliados entre agosto/2012 e julho/2014, divididos igualmente em Grupo ASP (aspiração traqueal prévia à extubação) e NASP (sem aspiração prévia). Foram incluídos indivíduos com: primeira cirurgia cardíaca, idade entre 18 e 75 anos, IMC ? 30 kg/m² e sem doença pulmonar prévia. Foram excluídos indivíduos com tempo de CEC > 120 minutos, necessidade de assistência circulatória mecânica, relação PaO2/FiO2 < 200, SpO2 < 92%, tempo de intubação > 12 horas, PAM < 60 mmHg e sinais de secreção pulmonar. Variáveis hemodinâmicas, ventilatórias, complicações pulmonares e custos hospitalares foram avaliados. RESULTADOS: Foram analisados 228 pacientes (ASP= 114 NASP= 114). FC, PAS, PAD e PAM elevaram-se após aspiração e pós extubação nos grupos, retornando aos valores basais no decorrer do tempo. Não houve diferença estatística na FR e SpO2. Complicações pulmonares representaram 7,8%, sem diferença entre os grupos. CONCLUSÃO: A supressão da aspiração traqueal nos pacientes em pós-operatório imediato de cirurgia cardíaca não influenciou na incidência de complicações pulmonares e evolução clínica pós-operatória. Durante aspiração, houve alterações hemodinâmicas e respiratórias, sem repercussões clínicas, porém estas mesmas alterações ocorreram no grupo NASP após extubação, em menor intensidade. Aspiração endotraqueal sem indicação mostrou-se custosa e com desperdício de tempo dos profissionais.

Cardiorespiratory fitness on a treadmill in an adult cystic fibrosis population

Objectives(1) To describe the cardiorespiratory fitness (CRF) in an adult cystic fibrosis population related to sex and age, (2) to evaluate the cause of low CRF and (3) to study...

Metabolic Profile and Body Composition in Twins Concordant and Discordant for Physical Exercise.

The aim of this study was to evaluate the differences in the metabolic profile and body composition of monozygotic (MZ) twins concordant and discordant for the practice of physical exercise. The sample consisted of 92 MZ twins (72.5% female and 27.5% male, mean age 25.4 ± 5.69 years), registered with the Brazilian Registry of Twins, residing in Natal, Brazil. Data collection was carried out between the years 2016 and 2018. On day 1, subjects underwent a whole-body fitness evaluation, including measures of weight, height, body composition by Dual-Energy X-ray Absorptiometry and the Cardiorespiratory Exercise Test. On day 2, 10 ml blood samples were collected (overnight fasting) to determine the lipid profile and fasting glucose. The sample was separated into three groups: Active Concordant twins (Concordant A, n = 44 subjects), Inactive Concordant twins (Concordant I, n = 22 subjects) and Discordant pairs for Physical Exercise (Discordant PE, n = 26 subjects). The results demonstrated a difference between the discordant twins for exercise and also between the active versus sedentary groups, indicating a causal effect of exercise on the fat percentage, maximum oxygen consumption (VO2max) and second ventilatory threshold variables. Between groups, a difference was also observed between the groups in ventilatory threshold, very low-density lipoprotein and triglycerides. We concluded that, regardless of genetics, the practice of physical exercise was sufficient to generate alterations in body composition and VO2max in MZ twins, but not in the lipid profile or fasting glucose.

Postoperative Pulmonary Complications in the Morbidly Obese: The Role of Tidal Volume and Type of Abdominal Surgery.

The patient who is morbidly obese is not adequately represented in the evidence recommending intraoperative low tidal volume (VT) ventilation. We aimed to explore the association between VT adjusted for ideal body weight (IBW) and the occurrence of postoperative pulmonary complications in subjects who were morbidly obese and undergoing abdominal surgery, as well as its implications on intraoperative ventilatory variables. We included 734 subjects with a body mass index of at least 40 kg/m2, undergoing open or laparoscopic abdominal surgery that lasted for at least 120 min. Clinical variables were obtained to estimate the preoperative pulmonary risk as well as intraoperative ventilator data to perform associations. Outcomes were defined by medical billing code diagnoses and oxygen use. All data were collected electronically by using Structured Query Language. The subjects received a mean VT/IBW of 9.41 mL/kg IBW, and postoperative pulmonary complications occurred in 7.5% of the subjects. The occurrence of complications was correlated with the presence of several preoperative risk factors for postoperative pulmonary complications. VT/IBW was not associated with postoperative pulmonary complications. This finding remained present after separating different levels of VT/IBW. In a multivariate analysis, only laparoscopic surgery was an independent protective factor against postoperative pulmonary complications (odds ratio 0.07, 95% CI 0.01-0.55). VT/IBW was not associated with the occurrence of postoperative pulmonary complications in subjects who were morbidly obese and undergoing prolonged abdominal surgery. Future prospective studies are indicated to guide the optimum ventilation strategy for patients who are morbidly obese.

Impact of Aquatic Exercise on Respiratory Outcomes and Functional Activities in Children with Neuromuscular Disorders: Findings from an Open-Label and Prospective Preliminary Pilot Study.

Neuromuscular disorders (NMD) lead to the progressive loss of motor and respiratory functions and a decline in daily activities and participation. We aimed to evaluate respiratory changes and functional outcomes in children attending an aquatic therapy program. Eleven patients diagnosed with NMD (4–18 years, Vignos scale 1–9) were involved in a 10-week aquatic exercise program. The ventilation variables were: peak cough flow, volumes (forced expiratory volume in one second-FEV1 and inspiratory volume) and respiratory pressures to evaluate strength and oxygen saturation (O2 sat). Functional skills were measured in the aquatic environment (Water Orientation Test Alyn 1) and on dry land, (Pediatric Evaluation of Disability Inventory), together with quality of life (Pediatric Quality of Life Inventory). Our evaluation included several 2 × 6 mixed-model repeated measures analysis of covariance (ANCOVA) with time (baseline, post 1 session, pre-post at five weeks and pre-post at 10 weeks). Important improvements in functional skills were observed in and out of the water and children under the age of 11 displayed a significant difference for inspirational volume (p = 0.002) and O2 sat (p = 0.029). Clinical, statistically insignificant changes were found for peak cough flow and expiratory pressures values after aquatic exercise. These results may support a relationship between aquatic exercise in NMD, respiratory outcomes and functional activities in water and on land.

Apnea Testing Using Continuous Positive Airway Pressure When Determining Death by Neurologic Criteria in Children: Retrospective Analysis of Potential Adverse Events.

To determine the prevalence of adverse events during apnea testing for determination of death by neurologic criteria using continuous positive airway pressure in children. Single-center retrospective descriptive study. Academic children's hospital. Children evaluated for death by neurologic criteria in the PICU from 2013 to 2018. None. For each patient evaluated for death by neurologic criteria, we abstracted the number of apnea tests performed, vital signs and arterial blood gases during apnea testing, and outcome from the medical record. Adverse events were defined as oxygen-hemoglobin desaturation (arterial oxygen saturation < 85%), hypotension, or other significant event (e.g. arrhythmia, cardiac arrest) based on documentation in the medical record. We determined which adverse events resulted in early termination of the apnea test. We used oxygenation index, ventilator variables, and presence of vasopressors to determine preapnea test cardiopulmonary dysfunction. Seventy-two patients (age 7 yr [2.7-13.2 yr]; 48% male) underwent 121 apnea tests. Nine patients (12%) had 13 potential apnea tests deferred due to concern for cardiopulmonary instability as determined by the attending physician. Patients who underwent apnea testing had an oxygenation index of 3.5 (2.5-4.8) and were receiving vasopressors at the time of 108 apnea tests (89%). Hypotension was reported during seven apnea tests (6%) and resulted in the early termination of one apnea test (<1%). No other adverse events were reported. One hundred and twenty apnea tests (99%) were consistent with death by neurologic criteria. Apnea testing following a protocol that uses continuous positive airway pressure for apneic oxygenation has a low rate of adverse events in children meeting prerequisite criteria and determined by a pediatric intensivist to be physiologically appropriate for testing.

Comparative effects of neurally adjusted ventilatory assist and variable pressure support on lung and diaphragmatic function in a model of acute respiratory distress syndrome: A randomised animal study.

Variable assisted mechanical ventilation has been shown to improve lung function and reduce lung injury. However, differences between extrinsic and intrinsic variability are unknown. To investigate the effects of neurally adjusted ventilatory assist (NAVA, intrinsic variability), variable pressure support ventilation (Noisy PSV, extrinsic variability) and conventional pressure-controlled ventilation (PCV) on lung and diaphragmatic function and damage in experimental acute respiratory distress syndrome (ARDS). Randomised controlled animal study. University Hospital Research Facility. A total of 24 juvenile female pigs. ARDS was induced by repetitive lung lavage and injurious ventilation. Animals were randomly assigned to 24 h of either: 1) NAVA, 2) Noisy PSV or 3) PCV (n=8 per group). Mechanical ventilation settings followed the ARDS Network recommendations. The primary outcome was histological lung damage. Secondary outcomes were respiratory variables and patterns, subject-ventilator asynchrony (SVA), pulmonary and diaphragmatic biomarkers, as well as diaphragmatic muscle atrophy and myosin isotypes. Global alveolar damage did not differ between groups, but NAVA resulted in less interstitial oedema in dorsal lung regions than Noisy PSV. Gas exchange and SVA incidence did not differ between groups. Compared with Noisy PSV, NAVA generated higher coefficients of variation of tidal volume and respiratory rate. During NAVA, only 40.4% of breaths were triggered by the electrical diaphragm signal. The IL-8 concentration in lung tissue was lower after NAVA compared with PCV and Noisy PSV, whereas Noisy PSV yielded lower type III procollagen mRNA expression than NAVA and PCV. Diaphragmatic muscle fibre diameters were smaller after PCV compared with assisted modes, whereas expression of myosin isotypes did not differ between groups. Noisy PSV and NAVA did not reduce global lung injury compared with PCV but affected different biomarkers and attenuated diaphragmatic atrophy. NAVA increased the respiratory variability; however, NAVA yielded a similar SVA incidence as Noisy PSV. This trial was registered and approved by the Landesdirektion Dresden, Germany (AZ 24-9168.11-1/2012-2).

Relationships Between Ventilatory And Heart Rate Responses To Hypobaric Hypoxia: Influences Of Acetazolamide

Acetazolamide (AZ) is often used for prevention and/or treatment of acute mountain sickness (AMS), particularly during rapid ascent to altitudes > 3000 m. Although it is known that AZ augments ventilation (VE), it is unclear how this may affect chemoreflex relationships among ventilatory variables and control of heart rate (HR). PURPOSE: The purpose of the study was two-fold: 1), establish the effect of AZ and hypobaric hypoxia (HH) on VE and HR; and 2), estimate the effect of AZ on the chemoreflex relationship between VE and HR. METHODS: After completing familiarization testing at sea level (SL), 10 male volunteers (22 ± 3 yr; height: 176.0 ± 7.1 cm; weight: 77.5 ± 11.5 kg) completed two 30 hr HH exposures (~ 3500 m); one while taking AZ (500 mg/day) and one while taking a placebo, in a single-blind crossover design in random order. Ventilation and gas exchange, including HR, VE, and end-tidal partial pressure of carbon dioxide (PetCO2), were measured three times at rest, once at SL and then at ~2 and 24 hours into exposure to simulated altitude. A linear mixed model with a random intercept per subject was utilized to evaluate the influences of AZ and HH on HR, VE, and PetCO2. RESULTS: VE increased and PetCO2 decreased (p<0.05 for all) with both HH and AZ. HR increased with HH (p<0.001), but there was no further effect of AZ (p=0.15). HR was related to both VE (p=0.009) and PetCO2 (p<0.001) in all subjects. AZ shifted the relationships between HR, VE, and PetCO2, but there was no interaction between AZ and HH (p>0.10 for both). Overall, while AZ augmented VE it did not affect the slope of the relationship between HR and VE, but rather shifted the relationship to lower VE values. CONCLUSION: During exposure to HH, activation of the chemoreflex augments both ventilation and sympathetic outflow to the heart causing increased HR. Our present findings that VE tended to be lower for a given level of HR during AZ trials, suggest that AZ may have an influence to shift the relationship between these two chemoreflex-mediated events. Funded by USAMRMC; author views not official US Army or DOD policy.

The Effect of Acidic Water Composition on Removal Efficiency of Air Ammonia in a Spray Tower

Introduction: One of the major factors that affect the employees' health and productivity in industries is the air quality of work environments. One of these pollutants is ammonia gas, which is very important from an economic and environmental points of view. Therefore, this study aimed to investigate the effect of using acidic water compound on the removal efficiency of air ammonia in a spray tower.&#x0D; Materials and Methods: In this study, airflow was provided by variable ventilation and water pressure through a class electropump. The rate of ammonia removal from the air stream was investigated by a spray tower with changes in water pressure, inlet gas density, and number of nozzles. For this purpose, at different inlet densities, different liquid pressures and different nozzles with water washing liquid with 0.01 mM sulfuric acid were used as the washing liquid.&#x0D; Results: Increased number of nozzles from one to three had a significant effect on ammonia removal (P-Value = 0.021). Increase of the inlet ammonia gas density from 24.1 to 68 parts per million significantly reduced the efficiency (P-Value = 0.058). Increase of the spray pressure from 9 bar to 12 bar also significantly increased the removal of ammonia gas from the spray tower outlet (P-Value = 0.052).&#x0D; Conclusion: Increased number of nozzles, increased spray pressure, and decreased density of the ammonia gas inlet gas will increase removal efficiency.&#x0D;

Variations in respiratory rate do not reflect changes in tidal volume or minute ventilation after major abdominal surgery

Monitoring of postoperative pulmonary function usually includes respiratory rate and oxygen saturation measurements. We hypothesized that changes in postoperative respiratory rate do not correlate with changes in tidal volume or minute ventilation. In addition, we hypothesized that variability of minute ventilation and tidal volume is larger than variability of respiratory rate. Respiratory rate and changes in tidal volume and in minute ventilation were continuously measured in 27 patients during 24 h following elective abdominal surgery, using an impedance-based non-invasive respiratory volume monitor (ExSpiron, Respiratory Motion, Waltham, MA, US). Coefficients of variation were used as a measure for variability of respiratory rate, tidal volume and minute ventilation. Data of 38,149 measurements were analyzed. We found no correlation between respiratory rate and tidal volume or minute ventilation (r2 = 0.02 and 0.01). Mean respiratory rate increased within the first 24 h after abdominal surgery from 13.9 ± 2.5 to 16.2 ± 2.4 breaths/min (p = 0.008), while tidal volume and minute ventilation remained unchanged (p = 0.90 and p = 0.18). Of interest, variability of respiratory rate (0.21 ± 0.06) was significantly smaller than variability of tidal volume (0.37 ± 0.12, p < 0.001) and minute ventilation (0.41 ± 0.12, p < 0.001). Changes in postoperative respiratory rate do not allow conclusions about changes in tidal volume or minute ventilation. We suggest that postoperative alveolar hypoventilation may not be recognized by monitoring respiratory rate alone. Variability of respiratory rate is smaller than variability in tidal volume and minute ventilation, suggesting that adaptations of alveolar ventilation to metabolic needs may be predominately achieved by variations in tidal volume.

Accuracy of volume and pressure delivery by mechanical ventilators in use in neonatal intensive care units: A quality control study.

Despite technical specifications of neonatal mechanical ventilators (MVs) guarantee clinically irrelevant discrepancies between the set and the delivered values of ventilation parameters, previous studies reported large deviations. Most studies characterized performances of a given model/brand by studying a single device, disregarding possible intramodel differences, and leaving the accuracy of the ventilation parameters effectively delivered in clinical settings unknown. The aim of this study was to evaluate the real-life accuracy of pressure and volume parameters delivered by neonatal ventilators ready to be used on patients in neonatal intensive care units (NICUs). In vitro study. Neonatal ventilators (n = 33 of 8 different models) available in four European NICUs. The MVs were connected to a test lung (resistance = 50 cmH2 O*s/L, compliance = 0.35 mL/cmH2 O) provided with pressure and flow sensors. MVs were tested over two different ventilation modes randomly: (a) pressure controlled (PC) with a peak inspiratory pressure (PIP) of 22 cmH2 O, and (b) PC with volume targeted ventilation (VTV) with a tidal volume (VT ) of 6 mL. In all tests, positive end-expiratory pressure (PEEP) was set to 6 cmH2 O, respiratory rate to 45 breaths/min, inspiratory time to 0.33 seconds, and oxygen fraction to 0.3. During PC the median (min-max) values delivered were: PEEP = 5.84(4.95-6.48) cmH2 O, PIP = 21.63(20.04-22.62) cmH2 O. During VTV, VT was 5.94(4.63-8.01) mL. VT was considerably variable, ranging from -22% to +33% of the set and displayed values. Differences in accuracy among devices of the same model were comparable to those found among different models. Our findings suggest that loss of accuracy in ventilation variables is likely related to daily use of the devices rather than weakness in the design or manufacturing process, urging the improvement of maintenance and quality control procedures to preserve the performances of neonatal MVs during their entire lifespan.

Brainstem inflammation modulates the ventilatory pattern and its variability after acute lung injury in rodents.

Compared with sham rats, rats a week after acute lung injury (ALI) express more pro-inflammatory cytokines in their brainstem respiratory control nuclei, exhibit a higher respiratory frequency (fR) and breathe with a more predictable pattern. These characteristics of the respiratory pattern persist in insitu preparations even after minimizing pulmonary and chemo-afferent inputs. Interleukin (IL)-1β microinjected in the nucleus tractus solitarii increases fR and the predictability of the ventilatory pattern similar to rats with ALI. Intracerebroventricular infusion of indomethacin, an anti-inflammatory drug, mitigates the effect of ALI on fR and ventilatory pattern variability. We conclude that changes in the ventilatory pattern after ALI result not only from sensory input due to pulmonary damage and dysfunction but also from neuro-inflammation. Acute lung injury (ALI) increases respiratory rate (fR) and ventilatory pattern variability (VPV), but also evokes peripheral and central inflammation. We hypothesized that central inflammation has a role in determining the ventilatory pattern after ALI. In rat pups, we intratracheally injected either bleomycin to induce ALI or saline as a sham control. One week later, we recorded the ventilatory pattern of the rat pups using flow-through plethysmography, then formed insitu preparations from these pups and recorded their 'fictive' patterns from respiratory motor nerves. Compared with the ventilatory pattern of the sham rat pups, injured rat pups had increased fR and predictability. Surprisingly, the fictive patterns of the insitu preparations from ALI pups retained these characteristics despite removing their lungs to eliminate pulmonary sensory inputs and perfusing them with hyperoxic artificial cerebral spinal fluid to minimize peripheral chemoreceptor input. Histological processing revealed increased immunoreactivity of the pro-inflammatory cytokine Interleukin-1β (IL-1β) in the nucleus tractus solitarii (nTS) from ALI but not sham rats. In subsequent experiments, we microinjected IL-1β in the nTS bilaterally in anaesthetized naïve adult rats, which increased fR and predictability of ventilatory pattern variability (VPV) after 2h. Finally, we infused indomethacin intracerebroventricularly during the week of survival after ALI. This did not affect sham rats, but mitigated changes in fR and VPV in ALI rats. We conclude that neuro-inflammation has an essential role in determining the ventilatory pattern of ALI rats.

Performance and recovery: effects of caffeine on a 2000-m rowing ergometer

This study investigated the effects of caffeine on subsequent performance and recovery from a 2000-m rowing ergometer. Nine trained male rowers (18.3 ± 1.1 years) consumed 3 or 6 mg kg−1 of caffeine or placebo. In three sequential time trials (TT), 30-min after (Trial1) and 6.5 h after (Trial2) caffeine intervention, participants performed a 2000-m ergometer effort. Power output (PO), stroke rate (SR), and time were monitored during the TTs. Ventilatory variables, serum creatine kinase (CK), blood lactate (BLa), and heart rate (HR) were recorded in Trial1 and Trial2, 30 min after Trial1 (1st recovery) and 30-min before Trial2 (2nd recovery). After ingesting 6 mg kg−1 of caffeine, PO was significantly greater in Trial1 (8.2%) compared to the placebo. Also significant increases in $$\dot{V}{\text{O}}_{{ 2 {\text{peak}}}}$$ during Trial1 (10.1%) and 2 (13.9%), HR at $$\dot{V}{\text{O}}_{{ 2 {\text{peak}}}}$$ (5.5%), $${\text{HR}}_{{V{\text{O}}_{{ 2 {\text{peak}}}} }}$$ during Trial1 (10.0%) and 2 (11.3%), $$\dot{V}{\text{O}}_{ 2}$$ /HRpeak in Trial1 (19.6%) and 2 (17.3%), $$\dot{V}{\text{O}}_{ 2}$$ at lactate threshold (LT) in Trial1 (24.6%), and significant decrease in ventilatory evaluation ( $$\dot{V}_{\text{E}}$$ ) (9.0%) were shown in 6 mg kg−1 compared to placebo. In recovery phase, minute ventilation (MV) was significantly higher in 1st (17.1%) and 2nd recovery (28.7%) and RER increased in 1st recovery (9.9%, P = 0.04) in 6 mg kg−1 compared to placebo. CK increased significantly in 2nd recovery (14.1%). BLa in 6 mg kg−1 was higher than placebo in Trial1 (18.6%) and Trial2 (24.4%). Based on improvements in ventilatory variables, and decreased CK and BLa levels after 6 mg kg−1 caffeine ingestion in performance and recovery, this study provides novel data by demonstrating that pre-exercise caffeine ingestion improves performance and subsequent recovery from rowing effort.

Mechanical Ventilation and Predictors of In-Hospital Mortality in Fibrotic Interstitial Lung Disease With Acute Respiratory Failure: A Cohort Analysis Through the Paradigm of Acute Respiratory Distress Syndrome.

Prior studies report significant mortality in fibrotic interstitial lung disease patients undergoing mechanical ventilation. Little is known about baseline characteristics or ventilator strategies that might improve outcomes. We analyzed the ventilator characteristics of a large cohort of fibrotic interstitial lung disease patients from the perspective of an acute respiratory distress syndrome paradigm to see if any specific mechanical ventilation strategies might improve in-hospital mortality. Retrospective cohort study. Single-center, multihospital medical ICUs. Consecutive fibrotic interstitial lung disease patients who experienced mechanical ventilation for acute respiratory failure. Interstitial lung disease characteristics, demographics, and ventilator variables were analyzed for univariable and multivariable predictors of in-hospital mortality, adjusted for confounding with an a priori causation model. A total of 111 patients accounted for 114 admissions. Idiopathic pulmonary fibrosis comprised 34% with idiopathic acute exacerbation (65%) being the most common admission type. Ninety-five percent were initiated on mandatory volume-control ventilation with only 50% achieving a low tidal volume strategy (plateau pressure ≤ 30 cm H2O) within 3 hours of intubation. Unadjusted clinical predictors of in-hospital mortality included age (unit odds ratio, 1.05; 1.01-1.10; p = 0.015), time from admission to intubation (hr) (unit odds ratio, 1.01; 1.01-1.03; p = 0.017), and use of paralytics (relative risk, 1.54; 1.26-1.90, p < 0.001). Adjusted mechanical ventilation-related predictors of in-hospital mortality included achieving early targeted plateau pressures (odds ratio, 0.23; 0.07-0.76; p = 0.016), PaO2/FIO2 ratio at 3 (unit odds ratio, 0.98; 0.96-0.99, p = 0.002) and 48 hours (unit odds ratio, 0.98; 0.97-0.99, p = 0.018), initial mean airway pressure (unit odds ratio, 1.13; 1.02-1.28, p = 0.019), and total net fluid status (mL) (unit odds ratio, 1.01; 1.001-1.02, p = 0.0001). Several factors predict in-hospital mortality in fibrotic interstitial lung disease-associated mechanical ventilation when viewed through an acute respiratory distress syndrome model. Further research is needed to refine strategies that may perhaps improve survival if mechanical ventilation is pursued in this set of patients.

Lifestyle interventions reduce exercise ventilatory variability in healthy individuals: a randomized intervention study.

Aim: Variation of exercise ventilation confers poor prognosis in heart failure. Sedentary men have higher exercise ventilatory variability than athletes. However, the impact of lifestyle intervention on exercise ventilatory variability in sedentary people is unknown and this is the aim of this study. Materials & methods: Prospective controlled single-blinded interventional study that randomly assigned healthy sedentary individuals to diet and exercise (intervention group, n = 12) or no intervention (control group, n = 12) for 12weeks. Exercise ventilatory variability was accessed before and after intervention. Results: Despite similar values at baseline, there was a 15% reduction in respiratory rate variability (root mean square of the successive differences/n) in intervention group. Conclusion: Diet and exercise training reduced exercise ventilatory variability.