Respiratory Gas Exchange Research Articles

Immunohistochemical and ultrastructural study of the immune cell system and epithelial surfaces of the respiratory organs in the bimodally breathing African sharptooth catfish (Clarias gariepinus Burchell, 1822).

Acetylcholine (Ach) represents the old neurotransmitter in central and peripheral nervous system. Its muscarinic and nicotinic receptors (mAChRs and nAChRs) constitute an independent cholinergic system that is found in immune cells and play a key role in the regulation of the immune function and cytokine production. Gas exchanging surfaces of the gills and air-breathing organs (ABOs) of the sharptooth catfish Clarias gariepinus were investigated using ultrastructural and confocal immunofluorescence techniques. This study was predominantly focused on the structure of the immune cell types, the expression of their neurotransmitters, including the antimicrobial peptide piscidin 1, and the functional significance of respiratory gas exchange epithelia. A network of immune cells (monocytes, eosinophils, and mast cells) was observed in the gill and the ABO epithelia. Eosinophils containing 5-hydroxytryptamine (5-HT) immunoreactivity were seen in close association with mast cells expressing acetylcholine (Ach), 5-HT, neuronal nitric oxide synthase, and piscidin 1. A rich and dense cholinergic innervation dispersing across the islet capillaries of the gas exchange barrier and the localization of Ach in the squamous pavement cells covering the capillaries were evidenced byVAChT antibodies. We report for the first time that piscidin 1 (Pis 1)-positive mast cells interact with Pis 1-positive nerves found in the epithelia of the respiratory organs. Pis 1 immunoreactivity was also observed in the covering respiratory epithelium of the ABOs and associated with a role in local mucosal immune defense. The above results anticipate future studies on the neuro-immune interactions at mucosal barrier surfaces, like the gill and the skin of fish, areas densely populated by different immune cells and sensory nerves that constantly sense and adapt to tissue-specific environmental challenges.

Sequential lateral positioning as a new lung recruitment maneuver: an exploratory study in early mechanically ventilated Covid-19 ARDS patients

BackgroundA sequential change in body position from supine-to-both lateral positions under constant ventilatory settings could be used as a postural recruitment maneuver in case of acute respiratory distress syndrome (ARDS), provided that sufficient positive end-expiratory pressure (PEEP) prevents derecruitment. This study aims to evaluate the feasibility and physiological effects of a sequential postural recruitment maneuver in early mechanically ventilated COVID-19 ARDS patients.MethodsA cohort of 15 patients receiving lung-protective mechanical ventilation in volume-controlled with PEEP based on recruitability were prospectively enrolled and evaluated in five sequentially applied positions for 30 min each: Supine-baseline; Lateral-1st side; 2nd Supine; Lateral-2nd side; Supine-final. PEEP level was selected using the recruitment-to-inflation ratio (R/I ratio) based on which patients received PEEP 12 cmH2O for R/I ratio ≤ 0.5 or PEEP 15 cmH2O for R/I ratio > 0.5. At the end of each period, we measured respiratory mechanics, arterial blood gases, lung ultrasound aeration, end-expiratory lung impedance (EELI), and regional distribution of ventilation and perfusion using electric impedance tomography (EIT).ResultsComparing supine baseline and final, respiratory compliance (29 ± 9 vs 32 ± 8 mL/cmH2O; p < 0.01) and PaO2/FIO2 ratio (138 ± 36 vs 164 ± 46 mmHg; p < 0.01) increased, while driving pressure (13 ± 2 vs 11 ± 2 cmH2O; p < 0.01) and lung ultrasound consolidation score decreased [5 (4–5) vs 2 (1–4); p < 0.01]. EELI decreased ventrally (218 ± 205 mL; p < 0.01) and increased dorsally (192 ± 475 mL; p = 0.02), while regional compliance increased in both ventral (11.5 ± 0.7 vs 12.9 ± 0.8 mL/cmH2O; p < 0.01) and dorsal regions (17.1 ± 1.8 vs 18.8 ± 1.8 mL/cmH2O; p < 0.01). Dorsal distribution of perfusion increased (64.8 ± 7.3% vs 66.3 ± 7.2%; p = 0.01).ConclusionsWithout increasing airway pressure, a sequential postural recruitment maneuver improves global and regional respiratory mechanics and gas exchange along with a redistribution of EELI from ventral to dorsal lung areas and less consolidation.Trial registration ClinicalTrials.gov, NCT04475068. Registered 17 July 2020, https://clinicaltrials.gov/ct2/show/NCT04475068

Percentage of Age-Predicted Cardiorespiratory Fitness and Risk of Incident Hypertension: A PROSPECTIVE COHORT STUDY.

There are inverse and independent associations between cardiorespiratory fitness (CRF) and several adverse cardiometabolic outcomes including hypertension (HTN). The prospective relationship between percentage of age-predicted CRF and risk of HTN has not been previously investigated. We aimed to assess the association of percentage of age-predicted CRF with incident HTN in a long-term prospective cohort study. Cardiorespiratory fitness, as measured by peak oxygen uptake, was assessed using the gold standard respiratory gas exchange analyzer in 1602 men who underwent cardiopulmonary exercise testing. The age-predicted CRF estimated from a regression equation for age was converted to percentage of age-predicted CRF ([achieved CRF/age-predicted CRF] × 100). The HR with 95% CI were estimated for HTN. During a median follow-up of 26.8 yr, 308 HTN cases were recorded. There was a linear relationship between age-predicted CRF and incident HTN ( P value for nonlinearity = .68). A 1-SD increase in percentage of age-predicted CRF was associated with a decreased risk of HTN in analysis adjusted for established risk factors (HR = 0.79: 95% CI, 0.69-0.90), which remained consistent on further adjustment for several other potential confounders including alcohol consumption, physical activity, socioeconomic status, and inflammation (HR = 0.83: 95% CI, 0.72-0.95). The corresponding adjusted HRs were 0.55 (95% CI, 0.38-0.80) and 0.63 (95% CI, 0.43-0.91), respectively, when comparing extreme quartiles of percentage of age-predicted CRF levels. Percentage of age-predicted CRF is linearly, inversely, and independently associated with risk of incident HTN, and it is comparable to absolute CRF as a risk indicator for HTN in a general population of middle-aged men.

Cardiorespiratory Fitness, Inflammation, and Risk of Chronic Obstructive Pulmonary Disease in Middle-Aged Men: A COHORT STUDY.

Chronic obstructive pulmonary disease (COPD) is characterized by chronic lung inflammation. The relationship between cardiorespiratory fitness (CRF) and COPD has not been well characterized. We aimed to evaluate the independent and joint associations of inflammation (high-sensitivity C-reactive protein [hsCRP]) and CRF with COPD risk in a cohort of White men. Among 2274 men aged 42-61 yr at baseline, serum hsCRP level was measured using an immunometric assay and CRF was assessed using a respiratory gas exchange analyzer. The level of hsCRP was categorized as normal and high (≤3 and >3 mg/L, respectively) and CRF as low and high. We corrected for within-person variability in exposures using repeat measurements taken several years apart. A total of 116 COPD cases occurred during a median follow-up of 26.0 yr. The age-adjusted regression dilution ratio of hsCRP and CRF was 0.57 (95% CI, 0.50-0.64) and 0.58 (95% CI, 0.53-0.64), respectively. Comparing high versus normal hsCRP levels, the multivariable-adjusted HR for COPD was 1.79 (95% CI, 1.20-2.68). The COPD risk decreased linearly with increasing CRF. The multivariable-adjusted HR for COPD per 1-SD increase in CRF was 0.75 (95% CI, 0.60-0.95). Compared with men with normal hsCRP-low CRF, high hsCRP-low CRF was associated with an increased COPD risk, 1.80 (95% CI, 1.12-2.89), with no evidence of an association for high hsCRP-high CRF and COPD risk, 1.35 (95% CI, 0.68-2.69). Both hsCRP and CRF are associated with COPD risk in middle-aged men. However, high CRF levels attenuate the increased COPD risk related to high hsCRP levels.

Hemodynamic response to positive end-expiratory pressure and prone position in COVID-19 ARDS

BackgroundUse of high positive end-expiratory pressure (PEEP) and prone positioning is common in patients with COVID-19-induced acute respiratory failure. Few data clarify the hemodynamic effects of these interventions in this specific condition. We performed a physiologic study to assess the hemodynamic effects of PEEP and prone position during COVID-19 respiratory failure. MethodsNine adult patients mechanically ventilated due to COVID-19 infection and fulfilling moderate-to-severe ARDS criteria were studied. Respiratory mechanics, gas exchange, cardiac output, oxygen consumption, systemic and pulmonary pressures were recorded through pulmonary arterial catheterization at PEEP of 15 and 5 cmH2O, and after prone positioning. Recruitability was assessed through the recruitment-to-inflation ratio. ResultsHigh PEEP improved PaO2/FiO2 ratio in all patients (p = 0.004), and significantly decreased pulmonary shunt fraction (p = 0.012), regardless of lung recruitability. PEEP-induced increases in PaO2/FiO2 changes were strictly correlated with shunt fraction reduction (rho=-0.82, p = 0.01). From low to high PEEP, cardiac output decreased by 18 % (p = 0.05) and central venous pressure increased by 17 % (p = 0.015).As compared to supine position with low PEEP, prone positioning significantly decreased pulmonary shunt fraction (p = 0.03), increased PaO2/FiO2 (p = 0.03) and mixed venous oxygen saturation (p = 0.016), without affecting cardiac output. PaO2/FiO2 was improved by prone position also when compared to high PEEP (p = 0.03). ConclusionsIn patients with moderate-to-severe ARDS due to COVID-19, PEEP and prone position improve arterial oxygenation. Changes in cardiac output contribute to the effects of PEEP but not of prone position, which appears the most effective intervention to improve oxygenation with no hemodynamic side effects.

High fitness levels attenuate the increased risk of heart failure due to low socioeconomic status: A cohort study

High fitness levels attenuate the increased risk of heart failure due to low socioeconomic status: A cohort study

Blood Flow and Respiratory Gas Exchange in the Human Placenta at Term: A Data Update.

Reliable measurements using modern techniques and consensus in experimental design have enabled the assessment of novel data sets for normal maternal and foetal respiratory physiology at term. These data sets include (a) principal factors affecting placental gas transfer, e.g., maternal blood flow through the intervillous space (IVS) (500mL/min) and foeto-placental blood flow (480mL/min), and (b) O2, CO2 and pH levels in the materno-placental and foeto-placental circulation. According to these data, the foetus is adapted to hypoxaemic hypoxia. Despite flat oxygen partial pressure (pO2) gradients between the blood of the IVS and the umbilical arteries of the foetus, adequate O2 delivery to the foetus is maintained by the higher O2 affinity of the foetal blood, high foetal haemoglobin (HbF) concentrations, the Bohr effect, the double-Bohr effect, and high foeto-placental (=umbilical) blood flow. Again, despite flat gradients, adequate CO2 removal from the foetus is maintained by a high diffusion capacity, high foeto-placental blood flow, the Haldane effect, and the double-Haldane effect. Placental respiratory gas exchange is perfusion-limited, rather than diffusion-limited, i.e., O2 uptake depends on O2 delivery.

Basal power reconstruction during cycling using a robust discrete-time PI observer

The basal metabolic rate characterizes the energy consumption of the human body at rest. It can be estimated by using respiratory gas exchange analyzers and indirect calorimetry. During cycling this value could vary due to several adaptation processes such as an increase in breathing and blood circulation, controlling body temperature, among others. In this paper we propose to reconstruct the instantaneous value of this basal metabolic rate, referred here as basal power (measured in Watts), by using a robust discrete-time proportional integral (PI) observer. The observer design is based on a solution of linear matrix inequalities and uses an uncertain linear parameter varying model of the gas exchange dynamics. The proposed methodology allows the reconstruction of the basal power while making the respiratory gas exchange estimation robust to bounded uncertainties and disturbances. The PI observer has been validated in simulation.

Efficacy of intravenous immunoglobulin in the treatment of a COVID-19 patient

Introduction. Diabetes mellitus patients are a vulnerable group of people who are prone to getting infected with severe acute respiratory syndrome corona virus 2 (SARS-CoV-2). The virus has a high binding affinity to angiotensin-converting enzyme 2 receptor, which allows efficient host cell entering, prolonged virus retention, and a possibility of insulin resistance and ketoacidosis development. Case outline. We describe a case of a 20-year-old patient with a past medical history of type 1 diabetes mellitus who presented with bilateral COVID-19 pneumonia. Initially, treatment with polyvitamin therapy, corticosteroids, tocilizumab, and convalescent plasma did not improve the patient?s condition, but might have led to the worsening of the underlying disease, high blood glucose level, and ketoacidosis. Patient developed a rapid progression of the disease and severe pneumonia that required intubation and mechanical ventilation. Intravenous immunoglobulin (IVIg) was administrated in order to suppress a hyperactive immune response through its immunomodulatory effect. Forty-eight hours later, respiratory gas exchange was improved, almost complete regression of changes in the lungs was seen, normalization of metabolic and gas exchange parameters was detected. After 14 days of hospitalization, the patient was discharged in good general condition. Conclusion. COVID-19 complicated by diabetes mellitus leads to a poor outcome of the disease, but antiviral and anti-inflammatory activity of IVIg suggests that it may be a useful therapeutic agent in cases of COVID-19. In the presented case, the application of IVIg led to a rapid improvement in the patient?s condition.

Comparative Analysis of the Indirect Calorimetry and the Metabolic Power Method to Calculate Energy Expenditure in Team Handball

Monitoring physical activity, e.g., training load and energy expenditure (EE), is important to optimize the training process in various sports. Especially in team handball, where there is little information about EE in training and competition. The objective of the study was to compare EE in team handball derived from a respiratory gas exchange analysis (spiroergometry) and a local position measurement (LPM) system. Eleven participants completed a validated, team handball game-based performance test and wore a portable spiroergometry system (K5 Cosmed) and an LPM transponder (Catapult ClearSky T6). EE was determined via indirect calorimetry for spiroergometry data and via the metabolic power model for EE for LPM data. EE estimated via the metabolic power model was −66 to −63 ± 12% lower than via indirect calorimetry (p &lt; 0.001, pη2 = 0.97). No correlation was found for the overall test (r = 0.32, p = 0.34), nor for every single heat (r ≤ 0.44, 0.18 ≤ p ≤ 0.99). Therefore, regression analyses predicting spiroergometry data based on LPM data were not feasible. In line with previous studies, the metabolic power model for EE in team handball (including short-distance movements, great accelerations, and non-locomotive actions) is not suitable.

Positive end-expiratory pressure in COVID-19 acute respiratory distress syndrome: the heterogeneous effects

BackgroundWe hypothesized that as CARDS may present different pathophysiological features than classic ARDS, the application of high levels of end-expiratory pressure is questionable. Our first aim was to investigate the effects of 5–15 cmH2O of PEEP on partitioned respiratory mechanics, gas exchange and dead space; secondly, we investigated whether respiratory system compliance and severity of hypoxemia could affect the response to PEEP on partitioned respiratory mechanics, gas exchange and dead space, dividing the population according to the median value of respiratory system compliance and oxygenation. Thirdly, we explored the effects of an additional PEEP selected according to the Empirical PEEP-FiO2 table of the EPVent-2 study on partitioned respiratory mechanics and gas exchange in a subgroup of patients.MethodsSixty-one paralyzed mechanically ventilated patients with a confirmed diagnosis of SARS-CoV-2 were enrolled (age 60 [54–67] years, PaO2/FiO2 113 [79–158] mmHg and PEEP 10 [10–10] cmH2O). Keeping constant tidal volume, respiratory rate and oxygen fraction, two PEEP levels (5 and 15 cmH2O) were selected. In a subgroup of patients an additional PEEP level was applied according to an Empirical PEEP-FiO2 table (empirical PEEP). At each PEEP level gas exchange, partitioned lung mechanics and hemodynamic were collected.ResultsAt 15 cmH2O of PEEP the lung elastance, lung stress and mechanical power were higher compared to 5 cmH2O. The PaO2/FiO2, arterial carbon dioxide and ventilatory ratio increased at 15 cmH2O of PEEP. The arterial–venous oxygen difference and central venous saturation were higher at 15 cmH2O of PEEP. Both the mechanics and gas exchange variables significantly increased although with high heterogeneity. By increasing the PEEP from 5 to 15 cmH2O, the changes in partitioned respiratory mechanics and mechanical power were not related to hypoxemia or respiratory compliance. The empirical PEEP was 18 ± 1 cmH2O. The empirical PEEP significantly increased the PaO2/FiO2 but also driving pressure, lung elastance, lung stress and mechanical power compared to 15 cmH2O of PEEP.ConclusionsIn COVID-19 ARDS during the early phase the effects of raising PEEP are highly variable and cannot easily be predicted by respiratory system characteristics, because of the heterogeneity of the disease.

Maximal exercise outcomes with a face mask: the effects of gender and age differences on cardiorespiratory responses.

BackgroundSurgical masks have become an important accessory of physical activity in daily life due to the COVID-19 pandemic.AimsTo determine the effects of the surgical mask on respiratory gas exchange parameters, dyspnoea, and hemodynamic responses during maximal exercise in different age groups and gender.MethodsTwenty-six healthy participants between 18 and 65 years (mean 37.35 ± 15.99) performed a maximal exercise test twice randomly, with and without a mask. To determine the respiratory gas exchange parameters (peak oxygen consumption (VO2peak), minute ventilation (VE), energy expenditure (EE), respiratory rate), and hemodynamic responses, each participant underwent a maximal exercise test with Bruce protocol on the treadmill. The modified Borg scale (MBS) was used to determine the dyspnoea before and after exercise test.ResultsTest duration (min), metabolic equivalents (MET), VO2peak ml/kg/min, respiratory rate, and peak heart rate (HRpeak) of young participants after exercise test with and without a mask were higher than in middle-aged participants (p < 0.01). There was no significant difference between males and females in test duration, VO2peak ml/kg/min, VO2peak ml/min, MET, VE l/min, respiratory rate, MBS, and EE in masked tests (p > 0.05).ConclusionThe surgical mask use affected the maximal exercise capacity of middle-aged participants more than young participants. Although males performed better than females in tests without masks, the decrease in exercise capacity with mask use was greater than in females. Advanced age and male gender may be factors that need more attention during exercise with mask use.Trial registration number and dateNCT04498546—02/17/2021.

Transcriptome-based insights into the calcium transport mechanism of chick chorioallantoic membrane

Chorioallantoic membrane (CAM) is responsible for respiratory gas exchange, eggshell calcium transport, embryonic acid-base equilibrium, allantoic ion, and water reabsorption during avian embryonic development. To further understand the timing of CAM gene expression during chick embryonic development, especially the calcium absorption mechanism, transcriptome quantitative comparative analysis was conducted on chick CAM during the embryonic period (E) of 9, 13, 17, and 20 days. A total of 6378 differentially expressed genes (DEGs) were identified. Functional enrichment analysis of DEGs showed that CAM DEGs were mainly involved in biological processes such as “ion transport regulation”, “immune response” and “cell cycle”. Time series analysis of the differential genes showed that the functional cells of CAM began to proliferate and differentiate at E9 and the calcium content of egg embryo increased significantly at E13. Simultaneously, the observation of the ultrastructure of the eggshell showed that the interstice of the fiber layer was enlarged at E13, and the mastoid layer was partly exposed. Therefore, it is preliminarily inferred that CAM calcium transport starts at E13, and genes such as TRPV6, S100A10, and RANKL cooperate to regulate calcium release and transport.

Abstract 14099: Using a Respiratory Resistance Device as a Therapeutic Modality in Patients With a History of Heart Failure, Preliminary Report

Introduction: Heart failure (HF) is associated with limited blood flow reserve due to reduced cardiac output (Q). HF is also associated with generalized respiratory muscle weakness, despite patients being exposed to an increased work and cost of breathing due primarily to increased flow resistive work from an altered breathing pattern. We hypothesized that the use of a respiratory training device during aerobic exercise training would positively impact patients with HF by training the inspiratory muscles and modifying their respiratory response to exercise. Methods: 15 subjects completed all study visits (age 67.5±10.0 yr, Ht 179.3±6.1cm, BMI 28.8±5.7 m/cm 2 ). Patients diagnosed with HF and currently enrolled in cardiac rehabilitation (CR) completed the Minnesota living with heart failure questionnaire (MLHFQ), pulmonary function testing, and measures during exercise that included Q (soluble gas method), ventilation (V E ) and respiratory gas exchange. Measures were made at baseline and after completion of CR. Participants were randomized to no respiratory resistance (NR) or mild-moderate inspiratory resistance (MR, 15 to 20 cmH 2 O) provided by a respiratory resistance mask (Training Mask Co., Cadillac, MI) worn during aerobic portions of CR. Results: Participants completed on average 23.9 ± 2.5 CR sessions with 10 subjects in the MR group and 5 in the NR group. The MR group had a decrease on the MLHFQ score of 19.9±26.9 and the NR group had a decrease of 6.0±23.4 (p=0.330). At a matched workload of 30 Watts (W), V E declined by 4.0±7.0 L/min and increased by 2.2±13.1 L/min for subjects in the MR and NR groups, respectively (p=0.06). Respiratory rate (RR) decreased in MR by 1.2± 4.9 and decreased in NR by 0.67± 5.9 (p&gt;0.05). Heart rate at 30W decreased with time in both the MR and NR groups 10.4±12.4 and 3.9±8.9 respectively (p=0.036, no difference between groups). Stroke volume at 30W tended to increase for both MR and NR (p&gt;0.05, no difference between groups). Conclusion: The addition of moderate inspiratory resistance to the aerobic training during CR was well tolerated by HF patients and preliminarily suggests trends toward improved ventilatory responses when assessed during submaximal exercise.

The influence of smoking on the formation of occupational lung diseases in workers who come into contact with industrial aerosols

The formation of a healthy lifestyle is one of the most important tasks of disease prevention. Among the factors that negatively affect the health of the population, smoking is of great importance. The influence of smoking on the formation of occupational diseases in workers in harmful and (or) dangerous working conditions has not been sufficiently studied. Based on the knowledge of the pathogenesis of common diseases, it can be assumed with a high degree of probability that smoking can provoke the development of occupational pathology of the respiratory organs, malignant neoplasms, vascular pathology.The aim of the work was to study the clinical manifestations of chronic bronchitis, characterizing the state of the bronchopulmonary system, in smokers and non-smokers who had long-term contact with industrial dust, as well as to analyze the literature data on the impact of smoking on the development of occupational lung diseases in workers exposed to asbestos dust.Materials and methods of research. In the clinic “Research Institute of Occupational Medicine named after Academician N.F. Izmerov”, 55 workers were examined under the influence of industrial aerosols of fibrogenic action. The group of smokers consisted of 45 people: 25 people were coal miners, 20 people were foundry workers. The group of non-smokers consisted of 10 people: 6 coal miners and 4 foundry workers. The severity of the course of professional and non-professional chronic bronchitis in patients was assessed taking into account the clinical manifestations and frequency of exacerbations of the disease, as well as taking into account the severity of respiratory disorders and gas exchange disorders.Results and discussion. In the group of smoking patients, 93,3% had occupational chronic bronchitis, 6.7% had no such pathology. In the group of non-smoking patients with and without occupational chronic bronchitis, there were equally – 50,0%. In the group of smoking patients, 55,5 of the examined patients had respiratory insufficiency of the II degree; 15,5% were diagnosed with respiratory insufficiency of the III degree; cases without respiratory function impairment (DN0 art.) were only 8,8%. In the group of non-smoking patients, grade II DN was more than three times less frequent, amounting to 20,0%, while 40,0% had grade 0 DN and 40,0% had grade I DN; grade III DN was never diagnosed in this group of patients.Conclusion. Smoking, as an independent factor, can play a significant, and in some cases, obviously, a determining role in the development and progression of chronic bronchitis in people exposed to industrial aerosols.The health risks associated with tobacco should be taken into account as an integral part of the assessment of the risks of developing occupational diseases.

The "Dolphin" Prone Position in Awake COVID-19 Patients.

The "Dolphin" Prone Position in Awake COVID-19 Patients.

Different Inspiratory Flow Waveform during Volume-Controlled Ventilation in ARDS Patients.

The most used types of mechanical ventilation are volume- and pressure-controlled ventilation, respectively characterized by a square and a decelerating flow waveform. Nowadays, the clinical utility of different inspiratory flow waveforms remains unclear. The aim of this study was to assess the effects of four different inspiratory flow waveforms in ARDS patients. Twenty-eight ARDS patients (PaO2/FiO2 182 ± 40 and PEEP 11.3 ± 2.5 cmH2O) were ventilated in volume-controlled ventilation with four inspiratory flow waveforms: square (SQ), decelerating (DE), sinusoidal (SIN), and trunk descending (TDE). After 30 min in each condition, partitioned respiratory mechanics and gas exchange were collected. The inspiratory peak flow was higher in the DE waveform compared to the other three waveforms, and in SIN compared to the SQ and TDE waveforms, respectively. The mean inspiratory flow was higher in the DE and SIN waveforms compared with TDE and SQ. The inspiratory peak pressure was higher in the SIN and SQ compared to the TDE waveform. Partitioned elastance was similar in the four groups; mechanical power was lower in the TDE waveform, while PaCO2 in DE. No major effect on oxygenation was found. The explored flow waveforms did not provide relevant changes in oxygenation and respiratory mechanics.

High fitness levels offset the increased risk of chronic obstructive pulmonary disease due to low socioeconomic status: A cohort study

ObjectiveEvidence suggests that higher cardiorespiratory fitness (CRF) levels can offset the increased risk of adverse outcomes due to other risk factors. The impact of high CRF levels on the increased risk of chronic obstructive pulmonary disease (COPD) due to low socioeconomic status (SES) is unknown. We aimed to assess the combined effects of SES and CRF on the future risk of COPD. MethodsWe employed a prospective cohort of 2312 Finnish men aged 42–61 years at study entry. Socioeconomic status was self-reported and CRF was objectively assessed using respiratory gas exchange analyzers. Both exposures were categorized as low and high based on median cutoffs. Multivariable-adjusted hazard ratios (HRs) with confidence intervals (CIs) were estimated. ResultsDuring 26.0 years median follow-up, 120 COPD cases occurred. Low SES was associated with increased COPD risk and high CRF was associated with reduced COPD risk. Compared with high SES-low CRF, low SES-low CRF was associated with an increased COPD risk 2.36 (95% CI: 1.44–3.87), with no evidence of an association for low SES-high CRF and COPD risk 1.46 (95% CI:0.82–2.60). ConclusionIn middle-aged Finnish men, SES and CRF are each independently associated with COPD risk. However, high CRF levels offset the increased COPD risk related to low SES.

Structural changes to the brood pouch of male pregnant seahorses (Hippocampus abdominalis) facilitate exchange between father and embryos.

Embryonic growth and development require efficient respiratory gas exchange. Internal incubation of developing young thus presents a significant physiological challenge, because respiratory gas diffusion to embryos is impeded by the additional barrier of parental tissue between the embryo and the environment. Therefore, live-bearing species exhibit a variety of adaptations facilitating respiratory gas exchange between the parent (usually the mother) and embryos. Syngnathid fishes are the only vertebrates to exhibit male pregnancy, allowing comparative studies of the biology and evolution of internal incubation of embryos, independent of the female reproductive tract. Here, we examine the fleshy, sealed, seahorse brood pouch, and provide the first quantification of structural changes to this gestational organ across pregnancy. We used histological analysis and morphometrics to quantify the surface area for exchange across the brood pouch epithelium, and the structure of the vascular bed of the brood pouch. We show dramatic remodelling of gestational tissues as pregnancy progresses, including an increase in tortuosity of the gestational epithelium, an increase in capillary density, and a decrease in diffusion distance between capillaries and the pouch lumen. These changes produce an increased surface area and expansion of the vascular bed of the placenta that likely facilitates respiratory gas exchange. These changes mirror the remodelling of gestational tissue in viviparous amniotes and elasmobranchs, and provide further evidence of the convergence of adaptations to support pregnancy in live-bearing animals.

Uterine cellular changes during mammalian pregnancy and the evolution of placentation†.

There are many different forms of nutrient provision in viviparous (live-bearing) species. The formation of a placenta is one method where the placenta functions to transfer nutrients from mother to fetus (placentotrophy), to transfer waste from the fetus to the mother, and to perform respiratory gas exchange. Despite having the same overarching function, there are different types of placentation within placentotrophic vertebrates, and many morphological changes occur in the uterus during pregnancy to facilitate formation of the placenta. These changes are regulated in complex ways but are controlled by similar hormonal mechanisms across species. This review describes current knowledge of the morphological and molecular changes to the uterine epithelium preceding implantation among mammals. Our aim is to identify the commonalities and constraints of these cellular changes to understand the evolution of placentation in mammals and to propose directions for future research. We compare and discuss the complex modifications to the ultrastructure of uterine epithelial cells (UEC) and show that there are similarities in the changes to the cytoskeleton and gross morphology of the UEC, especially of the apical and lateral plasma membrane of the cells during the formation of a placenta in all eutherians and marsupials studied to date. We conclude that further research is needed to understand the evolution of placentation among viviparous mammals, particularly concerning the level of placental invasiveness, hormonal control, and genetic underpinnings of pregnancy in marsupial taxa.