Improve Gas Exchange Research Articles

Benefits of intratracheal and extrathoracic high-frequency percussive ventilation in a model of capnoperitoneum.

Abdominal inflation with CO2 is used to facilitate laparoscopic surgeries, however, providing adequate mechanical ventilation in this scenario is of major importance during anesthesia management. We characterized high-frequency percussive ventilation (HFPV) in protecting from the gas exchange and respiratory mechanical impairments during capnoperitoneum. In addition, we aimed to assess the difference between conventional pressure-controlled mechanical ventilation (CMV) and HFPV modalities generating the high-frequency signal intratracheally (HFPVi) or extrathoracally (HFPVe). Anesthetized rabbits (n = 16) were mechanically ventilated by random sequences of CMV, HFPVi, and HFPVe. The ventilator superimposed the conventional waveform with two high-frequency signals (5 Hz and 10 Hz) during intratracheal HFPV (HFPVi) and HFPV with extrathoracic application of oscillatory signals through a sealed chest cuirass (HFPVe). Lung oxygenation index ([Formula: see text]/[Formula: see text]), arterial partial pressure of carbon dioxide ([Formula: see text]), intrapulmonary shunt (Qs/Qt), and respiratory mechanics were assessed before abdominal inflation, during capnoperitoneum, and after abdominal deflation. Compared with CMV, HFPVi with additional 5-Hz oscillations during capnoperitoneum resulted in higher [Formula: see text]/[Formula: see text], lower [Formula: see text], and decreased Qs/Qt. These improvements were smaller but remained significant during HFPVi with 10 Hz and HFPVe with either 5 or 10 Hz. The ventilation modes did not protect against capnoperitoneum-induced deteriorations in respiratory tissue mechanics. These findings suggest that high-frequency oscillations combined with conventional pressure-controlled ventilation improved lung oxygenation and CO2 removal in a model of capnoperitoneum. Compared with extrathoracic pressure oscillations, intratracheal generation of oscillatory pressure bursts appeared more effective. These findings may contribute to the optimization of mechanical ventilation during laparoscopic surgery.NEW & NOTEWORTHY The present study examines an alternative and innovative mechanical ventilation modality in improving oxygen delivery, CO2 clearance, and respiratory mechanical abnormalities in a clinically relevant experimental model of capnoperitoneum. Our data reveal that high-frequency oscillations combined with conventional ventilation improve gas exchange, with intratracheal oscillations being more effective than extrathoracic oscillations in this clinically relevant translational model.

Silicon attenuates aluminum toxicity in sugarcane plants by modifying growth, roots morphoanatomy, photosynthetic pigments, and gas exchange parameters.

Aluminum (Al) inhibits growth and limits plant productivity in acidic soils. An important strategy to increase Al tolerance is the use of silicon (Si) nutrition. Thus, the aim of this study was to evaluate the interactive role of Si in increasing the growth, physiological and morphoanatomy responses of sugarcane plants under Al toxicity. A 4 × 2 factorial scheme in a completely randomized design was used to study the impact of Si (2mM) on attenuating Al toxicity (0, 10, 15 and 20mgL-1, as Al2(SO4)3·18H2O) in sugarcane seedlings. After 45days, Al toxicity affected sugarcane growth by increasing Al uptake and accumulation, modifying root growth, thickness, and morphoanatomy, and decreasing pigment content, gas exchange parameters, and the number of adaxial and abaxial stomata. However, Si attenuated Al toxicity in the sugarcane seedlings by limiting Al uptake and transport to the shoots, causing positive changes in root morphoanatomy, higher pigment content, improving gas exchange parameters, thereby increased growth. Furthermore, cultivar 'CTC9003' showed beneficial impacts from Si supplementation than 'CTC9002', especially under Al toxicity. The findings of this study suggest that Si plays a notable role in improving anatomical and physiological aspects, particularly the growth of sugarcane seedlings under Al toxicity.

Effect of hydrogen sulfide on cabbage photosynthesis under black rot stress

Hydrogen sulfide (H2S), as a potential gaseous signaling molecule, is involved in mediating biotic and abiotic stress in plants. Currently, there are no studies investigating the mechanism by which H2S improves photosynthesis under black rot (BR) stress caused by Xanthomonas campestris pv. Campestris (Xcc). In this study, we investigated the effect of exogenous H2S on Xcc induced photosynthetic impairment in cabbage seedlings. BR has an inhibitory effect on the photosynthetic ability of cabbage seedlings. Xcc infection can significantly reduce the chlorophyll content, photosynthetic characteristics, chlorophyll fluorescence, Calvin cycle related enzyme activity and gene expression in cabbage leaves. The use of H2S can alleviate this inhibitory effect, reduce chlorophyll decomposition, improve gas exchange, enhance the activity of Calvin cycle related enzymes, and increase the expression of related genes. Transcriptome analysis showed that all differential genes related to photosynthesis were up regulated under H2S treatment compared to normal inoculation. Therefore, spraying exogenous H2S can improve the photosynthetic capacity of cabbage seedlings, reduce Xcc induced photoinhibition, and improve plant resistance.

Alleviation of salinity stress by EDTA chelated-biochar and arbuscular mycorrhizal fungi on maize via modulation of antioxidants activity and biochemical attributes

Salinity stress adversely affects agricultural productivity by disrupting water uptake, causing nutrient imbalances, and leading to ion toxicity. Excessive salts in the soil hinder crops root growth and damage cellular functions, reducing photosynthetic capacity and inducing oxidative stress. Stomatal closure further limits carbon dioxide uptake that negatively impact plant growth. To ensure sustainable agriculture in salt-affected regions, it is essential to implement strategies like using biofertilizers (e.g. arbuscular mycorrhizae fungi = AMF) and activated carbon biochar. Both amendments can potentially mitigate the salinity stress by regulating antioxidants, gas exchange attributes and chlorophyll contents. The current study aims to explore the effect of EDTA-chelated biochar (ECB) with and without AMF on maize growth under salinity stress. Five levels of ECB (0, 0.2, 0.4, 0.6 and 0.8%) were applied, with and without AMF. Results showed that 0.8ECB + AMF caused significant enhancement in shoot length (~ 22%), shoot fresh weight (~ 15%), shoot dry weight (~ 51%), root length (~ 46%), root fresh weight (~ 26%), root dry weight (~ 27%) over the control (NoAMF + 0ECB). A significant enhancement in chlorophyll a, chlorophyll b and total chlorophyll content, photosynthetic rate, transpiration rate and stomatal conductance was also observed in the condition 0.8ECB + AMF relative to control (NoAMF + 0ECB), further supporting the efficacy of such a combined treatment. Our results suggest that adding 0.8% ECB in soil with AMF inoculation on maize seeds can enhance maize production in saline soils, possibly via improvement in antioxidant activity, chlorophyll contents, gas exchange and morphological attributes.

Impacts of temperature and turbidity on the gill physiology of darter species

Fish gills are complex organs that have direct contact with the environment and perform numerous functions including gas exchange and ion regulation. Determining if gill morphometry can change under different environmental conditions to maintain and/or improve gas exchange and ion regulation is important for understanding if gill plasticity can improve survival with increasing environmental change. We assessed gill morphology (gas exchange and ion regulation metrics), hematocrit and gill Na+/K+ ATPase activity of wild-captured blackside darter (Percina maculata), greenside darter (Etheostoma blennioides), and johnny darter (Etheostoma nigrum) at two temperatures (10 and 25 °C) and turbidity levels (8 and 94 NTU). Samples were collected August and October 2020 in the Grand River to assess temperature differences, and August 2020 in the Thames River to assess turbidity differences. Significant effects of temperature and/or turbidity only impacted ionocyte number, lamellae width, and hematocrit. An increase in temperature decreased ionocyte number while an increase in turbidity increased lamellae width. Hematocrit had a species-specific response for both temperature and turbidity. Findings suggest that the three darter species have limited plasticity in gill morphology, with no observed compensatory changes in hematocrit or Na+/K+ ATPase activity to maintain homeostasis under the different environmental conditions.

АБК-МЕТАБОЛИЗИРУЮЩИЕ БАКТЕРИИ ВЛИЯЮТ НА СОДЕРЖАНИЕ АБК, ИУК И ЦИТОКИНИНОВ И СНИЖАЮТ НЕГАТИВНОЕ ВЛИЯНИЕ НА РОСТ РАСТЕНИЙ САЛАТА ПРИ ЗАГУЩЕННОЙ ПОСАДКЕ

With increasing planting density, ABA accumulates in plants and their growth is inhibited even before resource deficit occurs. In this study, an attempt was made to mitigate this negative manifestation of competition by inoculating lettuce plants with ABA degrading bacteria belonging to Pseudomonas. In laboratory experiments simulating planting density by the number of plants in a pot (one and three plants), similar abilities of bacteria, P. plecoglossicida 2.4-D and P. veronii IB K11-1 to level out the decrease in plant weight in dense planting were found. Both strains reduced the content of the ABA hormone accumulating in competing plants in the soil and in the shoot, increased the IAA content in the roots and in the soil, which sharply dropped in plants with dense planting, and reduced the zeatin content in the roots. The main mechanism of the positive effect of ABA-degrading bacteria on the growth of lettuce plants is discussed as an increase in hydraulic conductivity and improvement of gas exchange as a result of a decrease in ABA in plant shoots, which was supplemented by the direct effect of bacteria on the content of auxins that activate root growth.

Organic residue controls Meloidogyne javanica and improves gas exchange and development in the gilo

Organic residue controls Meloidogyne javanica and improves gas exchange and development in the gilo

Comparative analysis of pulmonary ventilation distribution between low-cost and branded incentive spirometers using electrical impedance tomography in healthy adults: Study protocol.

The Incentive Spirometer (IS) increases lung volume and improves gas exchange by visually stimulating patients to take slow, deep breaths. It prevents respiratory complications and treats postoperative atelectasis in patients undergoing abdominal, thoracic, and neurosurgical procedures. Its effectiveness has been validated in studies that support improved lung capacities and volumes in individuals with respiratory complications, postoperative thoracic surgery, upper abdominal surgery, and bariatric surgery. The modified Pachón incentive spirometer (MPIS) is a cost-effective alternative to branded IS. It is crucial to validate whether the MPIS distributes ventilation as effectively as commercial devices do. Ventilation distribution will be measured using electrical impedance tomography. The aim is to compare the distribution of pulmonary ventilation between the MPIS and another commercial IS in healthy adults using electrical impedance tomography. A crossover clinical trial is proposed to evaluate the measurement of pulmonary ventilation distribution using EIT in a sample of healthy adults. All participants will use a commercial flow IS and the MPIS, with the order of assignment randomized. This research will use electrical impedance tomography to validate the operation of the MPIS. This study protocol will compare two incentive spirometers' impact on pulmonary ventilation, potentially endorsing the adoption of a cost-effective device to enhance accessibility for targeted populations. The study was registered in ClinicalTrials.gov (NTC05532748).

Adherence to low tidal volume in the transition to spontaneous ventilation in patients with acute respiratory failure in intensive care units in Latin America (SPIRAL): a study protocol.

Patients with acute respiratory failure often require mechanical ventilation to reduce the work of breathing and improve gas exchange; however, this may exacerbate lung injury. Protective ventilation strategies, characterized by low tidal volumes (≤ 8mL/kg of predicted body weight) and limited plateau pressure below 30cmH2O, have shown improved outcomes in patients with acute respiratory distress syndrome. However, in the transition to spontaneous ventilation, it can be challenging to maintain tidal volume within protective levels, and it is unclear whether low tidal volumes during spontaneous ventilation impact patient outcomes. We developed a study protocol to estimate the prevalence of low tidal volume ventilation in the first 24 hours of spontaneous ventilation in patients with hypoxemic acute respiratory failure and its association with ventilator-free days and survival. We designed a multicenter, multinational, cohort study with a 28-day follow-up that will include patients with acute respiratory failure, defined as a partial oxygen pressure/fraction of inspired oxygen ratio < 300mmHg, in transition to spontaneous ventilation in intensive care units in Latin America. We plan to include 422 patients in ten countries. The primary outcomes are the prevalence of low tidal volume in the first 24 hours of spontaneous ventilation and ventilator-free days on day 28. The secondary outcomes are intensive care unit and hospital mortality, incidence of asynchrony and return to controlled ventilation and sedation. In this study, we will assess the prevalence of low tidal volume during spontaneous ventilation and its association with clinical outcomes, which can inform clinical practice and future clinical trials.

Personalized Noninvasive Respiratory Support in the Perioperative Setting: State of the Art and Future Perspectives.

Background: Noninvasive respiratory support (NRS), including high-flow nasal oxygen therapy (HFNOT), noninvasive ventilation (NIV) and continuous positive airway pressure (CPAP), are routinely used in the perioperative period. Objectives: This narrative review provides an overview on the perioperative use of NRS. Preoperative, intraoperative, and postoperative respiratory support is discussed, along with potential future areas of research. Results: During induction of anesthesia, in selected patients at high risk of difficult intubation, NIV is associated with improved gas exchange and reduced risk of postoperative respiratory complications. HFNOT demonstrated an improvement in oxygenation. Evidence on the intraoperative use of NRS is limited. Compared with conventional oxygenation, HFNOT is associated with a reduced risk of hypoxemia during procedural sedation, and recent data indicate a possible role for HFNOT for intraoperative apneic oxygenation in specific surgical contexts. After extubation, "preemptive" NIV and HFNOT in unselected cohorts do not affect clinical outcome. Postoperative "curative" NIV in high-risk patients and among those exhibiting signs of respiratory failure can reduce reintubation rate, especially after abdominal surgery. Data on postoperative "curative" HFNOT are limited. Conclusions: There is increasing evidence on the perioperative use of NRS. Use of NRS should be tailored based on the patient's specific characteristics and type of surgery, aimed at a personalized cost-effective approach.

Unveiling Si’s shield: A holistic examination of Cd stress alleviation in maize through physiological and transcriptomic insights

Cadmium (Cd), present in agricultural soil, poses a substantial threat to public health through the food chain, adversely affecting food crops and yield. This study examined the role of silicon (Si) in alleviating Cd stress in maize (Zea mays L.). Germinated uniform seedlings were transplanted into 20 L pots filled with a low-concentration nutrient solution. At the three fully expanded leaves stage (21 days after transplanting), plants were treated with Si (1000 μΜ as K2SO3) and Cd (10 μM as CdCl2). Plants were assessed 0, 1, and 28 days after treatments. The results demonstrate that Si application leads to a reduction in Cd concentration and content in maize shoot tissue. Additionally, Si treatment positively influences the activity of antioxidant enzymes (peroxidase, superoxidase dismutase, catalase) and plant hormones (abscisic acid, gibberellic acid, salicylic acid) in maize leaves. Furthermore, Si application enhances plant growth, increases levels of antioxidant substances, improves gas exchange parameters, boosts chlorophyll content, and enhances fluorescence. Weighted gene co-expression network analysis (WGCNA) and identification of transcription factors (TFs) and structural genes among differentially expressed genes (DEGs) reveal physiological correlations and enriched signaling pathways, particularly those related to metabolism and biosynthesis. Si actively modulates the formation of metabolites such as arginine and proline, starch and sucrose, as well as biosynthetic pathways for secondary metabolites like benzoxazinoid and carotenoid. Additionally, Si exerts regulatory influence over pathways such as the MAPK signaling pathway and plant hormone signal transduction in plants subjected to Cd stress. These findings unveil the molecular mechanisms underpinning the alleviation of Cd-induced stress in maize leaves due to Si application. Consequently, Si application not only mitigates Cd stress in maize but also reduces the risk of Cd entering the food chain.

The role of Point of Care Ultrasound (POCUS) and focused echocardiography in optimization of non-invasive mechanical ventilation: from diaphragmatic functionality to hemodynamic monitoring

Abstract This case shows the use of ultrasound guidance to optimize non-invasive mechanical ventilation for a 62-year-old patient with a complex medical history. Point-of-care ultrasound (POCUS) was used to assess diaphragmatic function and hemodynamics, leading to adjustments in ventilator setting. The approach improved gas exchange, resolved respiratory acidosis, and enhanced hemodynamics, providing a promising strategy for ventilator management in complex clinical cases. Keywords: Non-Invasive Mechanical Ventilation, Point-of-Care Ultrasound, Diaphragmatic Ultrasound, Focused Echocardiography, Ventilator-Induced Diaphragmatic Dysfunction, Hemodynamics.

Effect of dexamethasone on human neutrophil adhesion and concomitant secretion

Neutrophils play a dual role in protecting the body. They are able to penetrate infected tissues and destroy pathogens there, releasing aggressive bactericidal substances. Getting into the surrounding tissues, aggressive secretion products of neutrophils initiate the development of inflammatory processes. Invasion of neutrophils into tissues is observed during the development of pneumonia in patients with lung diseases of various etiologies, including acute respiratory distress syndrome caused by coronavirus disease. The synthetic corticosteroid hormone dexamethasone has a therapeutic effect in the treatment of lung diseases, including reducing mortality in patients with severe Covid-19. The acute (short-term) effect of dexamethasone on neutrophil adhesion to fibrinogen and concomitant secretion was studied. Dexamethasone did not affect either the attachment of neutrophils to the substrate or their morphology. The production of reactive oxygen species (ROS) and nitric oxide (NO) by neutrophils during adhesion also did not change in the presence of dexamethasone. Dexamethasone stimulated the release of metalloproteinases in addition to proteins secreted by neutrophil adhesion under control conditions, and selectively stimulated the release of the free amino acid hydroxylysine, a product of lysyl hydroxylase. Metalloproteinases play a key role and closely interact with lysyl hydroxylase in the processes of rearrangement of the extracellular matrix. The therapeutic effect of dexamethasone may be associated with its ability, by changing the composition of neutrophil secretions, to reorganize the extracellular matrix in tissues, which can lead to improved gas exchange in patients with severe lung diseases.

Electrical Impedance Tomography during Abdominal Laparoscopic Surgery: A Physiological Pilot Study

Background: Both general anesthesia and pneumoperitoneum insufflation during abdominal laparoscopic surgery can lead to atelectasis and impairment in oxygenation. Setting an appropriate level of external PEEP could reduce the occurrence of atelectasis and induce an improvement in gas exchange. However, in clinical practice, it is common to use a fixed PEEP level (i.e., 5 cmH2O), irrespective of the dynamic respiratory mechanics. We hypothesized setting a PEEP level guided by EIT in order to obtain an improvement in oxygenation and respiratory system compliance in lung-healthy patients than can benefit a personalized approach. Methods: Twelve consecutive patients scheduled for abdominal laparoscopic surgery were enrolled in this prospective study. The EIT Timpel Enlight 1800 was applied to each patient and a dedicated pneumotachograph and a spirometer flow sensor, integrated with EIT, constantly recorded respiratory mechanics. Gas exchange, respiratory mechanics and hemodynamics were recorded at five time points: T0, baseline; T1, after induction; T2, after pneumoperitoneum insufflation; T3, after a recruitment maneuver; and T4, at the end of surgery after desufflation. Results: A titrated mean PEEP of 8 cmH2O applied after a recruitment maneuver was successfully associated with the “best” compliance (58.4 ± 5.43 mL/cmH2O), with a low percentage of collapse (10%), an acceptable level of hyperdistention (0.02%). Pneumoperitoneum insufflation worsened respiratory system compliance, plateau pressure, and driving pressure, which significantly improved after the application of the recruitment maneuver and appropriate PEEP. PaO2 increased from 78.1 ± 9.49 mmHg at T0 to 188 ± 66.7 mmHg at T4 (p &lt; 0.01). Other respiratory parameters remained stable after abdominal desufflation. Hemodynamic parameters remained unchanged throughout the study. Conclusions: EIT, used as a non-invasive intra-operative monitor, enables the rapid assessment of lung volume and regional ventilation changes in patients undergoing laparoscopic surgery and helps to identify the “optimal” PEEP level in the operating theatre, improving ventilation strategies.

Effect of Dexamethasone on Adhesion of Human Neutrophils and Concomitant Secretion.

Neutrophils play a dual role in protecting the body. They are able to penetrate infected tissues and destroy pathogens there by releasing aggressive bactericidal substances. While into the surrounding tissues, the aggressive products secreted by neutrophils initiate development of inflammatory processes. Invasion of neutrophils into tissues is observed during the development of pneumonia in the patients with lung diseases of various etiologies, including acute respiratory distress syndrome caused by coronavirus disease. Synthetic corticosteroid hormone dexamethasone has a therapeutic effect in treatment of lung diseases, including reducing mortality in the patients with severe COVID-19. The acute (short-term) effect of dexamethasone on neutrophil adhesion to fibrinogen and concomitant secretion was studied. Dexamethasone did not affect either attachment of neutrophils to the substrate or their morphology. Production of reactive oxygen species (ROS) and nitric oxide (NO) by neutrophils during adhesion also did not change in the presence of dexamethasone. Dexamethasone stimulated release of metalloproteinases in addition to the proteins secreted by neutrophils during adhesion under control conditions, and selectively stimulated release of free amino acid hydroxylysine, a product of lysyl hydroxylase. Metalloproteinases play a key role and closely interact with lysyl hydroxylase in the processes of modification of the extracellular matrix. Therapeutic effect of dexamethasone could be associated with its ability to reorganize extracellular matrix in the tissues by changing composition of the neutrophil secretions, which could result in the improved gas exchange in the patients with severe lung diseases.

Polysomnographic outcomes of revision adenoidectomy in children with obstructive sleep apnea and recurrent/residual adenoidal hypertrophy.

Recurrent/residual adenoidal hypertrophy after adenotonsillectomy in children can result in obstructive sleep apnea (OSA). We aimed to assess the polysomnographic (PSG) outcomes of revision adenoidectomy in children with recurrent/residual adenoidal hypertrophy and OSA. This was a single-center retrospective study that included children with sleep studies that confirmed OSA and known history of adenotonsillectomy who were diagnosed with adenoidal hypertrophy and subsequently underwent revision adenoidectomy. Pre- and postoperative PSG variables of revision adenoidectomy were included in the analysis. A total of 20 children were included in the study. The cohort included 13 males and 7 females with a mean age of 7.8 years (± 3.6 years). The mean BMI z score was 1.96 [1.31, 2.43]. The median duration from adenotonsillectomy performance was 2.3 years [1.4, 4.0]. Overall, revision adenoidectomy resulted in significant improvements in multiple respiratory parameters, including AHI 6.6 [1.4, 13. 7] vs 14.8 [7.4, 20.7], p = 0.02; oxygen desaturations nadir 88.0 [84.0, 93.0] vs 80.0 [72.2, 88.9], p = 0.01; supine AHI 8.6 [1.5, 14.3] vs 17.6 [8.3, 30.2], p = 0.02; and arousal index 12.2 [9.6, 15.7] vs 18.9 [13.4, 24.9], p = 0.04. Children with recurrent/residual adenoidal hypertrophy after adenotonsillectomy who undergo revision adenoidectomy experience improvements in respiratory event, gas exchange, and arousal index.

Physiological effects of high flow oxygen therapy use in adult patients.

Background: Oxygen therapy is the first line treatment in patients with acute respiratory failure. It can be administered from high and low flow devices. High-flow oxygen therapy through nasal prongs (HFONC2) has gained attention in recent years as an alternative means of respiratory support for critically ill patients. Currently, several clinical trials have evaluated its effectiveness in different clinical situations and its different mechanisms of action that support its clinical benefits. Material and methods: Systematic review based on a bibliographic search in the following databases: Google Scholar, TripDatabase, PubMed, Cochrane Central Register of Controlled Trials. Using the following MeSH terms: Oxygen Inhalation Therapy, Cannula, Positive Pressure Respiration). It was limited by seniority of 10 years”, “age 19 years or more”. It included healthy volunteers and ARI patients. A total of 10 articles were selected to be reviewed. Results: CNAFO2 improves gas exchange, decreases RR, produces CO2 washout, significantly reduces respiratory effort indices in adult patients, this effect is associated with better tolerance and comfort compared to COT. In turn, the PEEP effect increases the overall EELI, meaning an increase in EELV. Conclusion: The use of CNAFO2 achieves potentially beneficial physiological and clinical effects in patients with IRAH that justify its use as first-line therapy when compared to conventional oxygen therapy.

Nebulised granulocyte-macrophage colony-stimulating factor (GM-CSF) in autoimmune pulmonary alveolar proteinosis: a systematic review and meta-analysis.

Autoimmune pulmonary alveolar proteinosis (aPAP) results from impaired macrophage-mediated clearance of alveolar surfactant lipoproteins. Whole lung lavage has been the first-line treatment but recent reports suggest the efficacy of granulocyte-macrophage colony-stimulating factor (GM-CSF). We aimed to review the efficacy and safety of nebulised GM-CSF in aPAP. We conducted a systematic review and meta-analysis searching Embase, CINAHL, MEDLINE and Cochrane Collaborative databases (1946-1 April 2022). Studies included patients aged >18 years with aPAP receiving nebulised GM-CSF treatment and a comparator cohort. Exclusion criteria included secondary or congenital pulmonary alveolar proteinosis, GM-CSF allergy, active infection or other serious medical conditions. The protocol was prospectively registered with PROSPERO (CRD42021231328). Outcomes assessed were St George's Respiratory Questionnaire (SGRQ), 6-min walk test (6MWT), gas exchange (diffusing capacity of the lung for carbon monoxide (D LCO) % predicted) and arterial-alveolar oxygen gradient. Six studies were identified for review and three for meta-analysis, revealing that SGRQ score (mean difference -8.09, 95% CI -11.88- -4.3, p<0.0001), functional capacity (6MWT) (mean difference 21.72 m, 95% CI -2.76-46.19 m, p=0.08), gas diffusion (D LCO % predicted) (mean difference 5.09%, 95% CI 2.05-8.13%, p=0.001) and arterial-alveolar oxygen gradient (mean difference -4.36 mmHg, 95% CI -7.19- -1.52 mmHg, p=0.003) all significantly improved in GM-CSF-treated patients with minor statistical heterogeneity (I2=0%). No serious trial-related adverse events were reported. Patients with aPAP treated with inhaled GM-CSF demonstrated significant improvements in symptoms, dyspnoea scores, lung function, gas exchange and radiology indices after treatment with nebulised GM-CSF of varying duration. There is an important need to review comparative effectiveness and patient choice in key clinical outcomes between the current standard of care, whole lung lavage, with the noninvasive treatment of nebulised GM-CSF in aPAP.

Venovenous extracorporeal membrane oxygenation for respiratory failure refractory to high frequency percussive ventilation

BackgroundHigh frequency percussive ventilation (HFPV) has demonstrated improvements in gas exchange, but not in clinical outcomes. ObjectivesWe utilize HFPV in patients failing conventional ventilation (CV), with rescue venovenous extracorporeal membrane oxygenation (VV ECMO) reserved for failure of HFPV, and we describe our experience with such a strategy. MethodsAll adult patients (age >18 years) placed on HFPV for failure of CV at a single institution over a 10-year period were included. Those maintained on HFPV were compared to those that failed HFPV and required VV ECMO. Survival was compared to expected survival after upfront VV ECMO as estimated by VV ECMO risk prediction models. ResultsSixty-four patients were placed on HFPV for failure of CV over a 10-year period. After HFPV initiation, the P/F ratio rose from 76mmHg to 153.3mmHg in the 69 % of patients successfully maintained on HFPV. The P/F ratio only rose from 60.3mmHg to 67mmHg in the other 31 % of patients, and they underwent rescue ECMO with the P/F ratio rising to 261.6mmHg. The P/F ratio continued to improve in HFPV patients, while it declined in ECMO patients, such that at 24 h, the P/F ratio was greater in HFPV patients. The strongest independent predictor of failure of HFPV requiring rescue VV ECMO was a lower pO2 (p = .055). Overall in-hospital survival (59.4 %) was similar to that expected with upfront ECMO (RESP score: 57 %). ConclusionsHFPV demonstrated significant and sustained improvements in gas exchange and may obviate the need for ECMO and its associated complications.

Cardiorespiratory adaptations in small cetaceans and marine mammals.

The dive response, or the 'master switch of life', is probably the most studied physiological trait in marine mammals and is thought to conserve the available O2 for the heart and brain. Although generally thought to be an autonomic reflex, several studies indicate that the cardiovascular changes during diving are anticipatory and can be conditioned. The respiratory adaptations, where the aquatic breathing pattern resembles intermittent breathing in land mammals, with expiratory flow exceeding 160litres s-1 has been measured in cetaceans, and where exposure to extreme pressures results in alveolar collapse (atelectasis) and recruitment upon ascent. Cardiorespiratory coupling, where breathing results in changes in heart rate, has been proposed to improve gas exchange. Cardiorespiratory coupling has also been reported in marine mammals, and in the bottlenose dolphin, where it alters both heart rate and stroke volume. When accounting for this respiratory dependence on cardiac function, several studies have reported an absence of a diving-related bradycardia except during dives that exceed the duration that is fuelled by aerobic metabolism. This review summarizes what is known about the respiratory physiology in marine mammals, with a special focus on cetaceans. The cardiorespiratory coupling is reviewed, and the selective gas exchange hypothesis is summarized, which provides a testable mechanism for how breath-hold diving vertebrates may actively prevent uptake of N2 during routine dives, and how stress results in failure of this mechanism, which results in diving-related gas emboli.