Adequate Gas Exchange Research Articles

Resuscitation of extremely preterm infants - controversies and current evidence.

Despite significant advances in perinatal medicine, the management of extremely preterm infants in the delivery room remains a challenge. There is an increasing evidence for improved outcomes regarding the resuscitation and stabilisation of extremely preterm infants but there is a lack of evidence in the periviable (gestational age 23-25 wk) preterm subgroup. Presence of an experienced team during the delivery of extremely preterm infant to improve outcome is reviewed. Adaptation from foetal to neonatal cardiorespiratory haemodynamics is dependent on establishing an optimal functional residual capacity in the extremely preterm infants, thus enabling adequate gas exchange. There is sufficient evidence for a gentle approach to stabilisation of these fragile infants in the delivery room. Evidence for antenatal steroids especially in the periviable infants, delayed cord clamping, strategies to establish optimal functional residual capacity, importance of temperature control and oxygenation in delivery room in extremely premature infants is reviewed in this article.

Cervical spinal cord injury exacerbates ventilator-induced diaphragm dysfunction.

Cervical spinal cord injury (SCI) can dramatically impair diaphragm muscle function and often necessitates mechanical ventilation (MV) to maintain adequate pulmonary gas exchange. MV is a life-saving intervention. However, prolonged MV results in atrophy and impaired function of the diaphragm. Since cervical SCI can also trigger diaphragm atrophy, it may create preconditions that exacerbate ventilator-induced diaphragm dysfunction (VIDD). Currently, no drug therapy or clinical standard of care exists to prevent or minimize diaphragm dysfunction following SCI. Therefore, we first tested the hypothesis that initiating MV acutely after cervical SCI will exacerbate VIDD and enhance proteolytic activation in the diaphragm to a greater extent than either condition alone. Rats underwent controlled MV for 12 h following acute (∼24 h) cervical spinal hemisection injury at C2 (SCI). Diaphragm tissue was then harvested for comprehensive functional and molecular analyses. Second, we determined if antioxidant therapy could mitigate MV-induced diaphragm dysfunction after cervical SCI. In these experiments, SCI rats received antioxidant (Trolox, a vitamin E analog) or saline treatment prior to initiating MV. Our results demonstrate that compared with either condition alone, the combination of SCI and MV resulted in increased diaphragm atrophy, contractile dysfunction, and expression of atrophy-related genes, including MuRF1. Importantly, administration of the antioxidant Trolox attenuated proteolytic activation, fiber atrophy, and contractile dysfunction in the diaphragms of SCI + MV animals. These findings provide evidence that cervical SCI greatly exacerbates VIDD, but antioxidant therapy with Trolox can preserve diaphragm contractile function following acute SCI.

Nurses' practice concerning weaning from mechanical ventilation in the intensive care unit

Results 423 attendants completed the survey (response rate: 66%) of which 342 ICU nurses were included for further analysis. These are employed in general (73%) or university hospitals (27%) and are working in mixed (66%), surgical (18%) or medical (13%) ICUs. Nurses working in university hospitals reported higher availability of weaning protocols (44% vs 29%; p = 0.016). 22% of nurses reported the availability of both weaning and sedation protocol. Protocols are paper-based (23%) or computer-assisted (5%) and in 20% of the cases never used. Nearly 20% of the nurses got some information or training about use of their protocol. Most frequently chosen weaning modes are CPAP (77%), BiLevel/BIPAP (74%) and PSV (59%). Nurses report to autonomously change ventilation modes (68%), pressure support (PS) level (66%) and respiratory rate (49%). Before starting a spontaneous breathing trial (SBT) evaluation of respiratory status (83%), respiratory capacity (73%) and oxygenation (63%) are considered. Spontaneous breathing on T-tube (58%) is the most frequently chosen SBT approach next to CPAP (57%) and PS ventilation with minimal PS (46%). Duration of first SBT between 30 and 120 minutes was found in nearly 50% of responses but it was not associated with the presence or absence of a weaning protocol (p = 0.57). Less than 30 minutes SBT was reported by 45% of nurses. In majority of the cases is SBT repeated 3 times per day (38%) and mostly at the daytime (99% vs. 37%). SBT is considered successful if adequate gas exchange is maintained during the procedure (89%), and prematurely terminated in case of signs of exhaustion (89%), inadequacy of gas exchange (90%) or hemodynamic instability (66%). Prior to extubation almost all nurses (94%) indicate oxygenation as an important parameter. When it comes to weaning, nurses are generally satisfied about the cooperation with MDs. Decision making in weaning is mostly taken by MDs (91%).

Protocolo diagnóstico y terapéutico de la hemoptisis en Urgencias

Hemoptysis is the expectoration of blood from the lower respiratory tract. It is usually a self-limited event, even if mass can be a potentially fatal condition requiring the admission of the patient in an intensive care unit and performing diagnostic tests and emergency treatment. Before assuming that the source of bleeding is the lower respiratory tract, it should consider appropriate blood gastrointestinal or upper airway. The diagnostic evaluation should begin with a medical history and physical examination. The chest radiograph is essential and the first diagnostic test to be performed. Bronchoscopy plays a major role, and chest computed tomography and angiography serve as a complement and extension of diagnostic and therapeutic possibilities. Its management must be done in stages, prioritizing the protection of the airway and respiratory and hemodynamic stabilization of the patient, to ensure adequate gas exchange and cardiovascular function.

Physiological impairment in mild COPD.

Chronic obstructive pulmonary disease (COPD) is a common and often progressive inflammatory disease of the airways, alveoli and microvasculature that is both preventable and treatable. It is well established that smokers with mild airway obstruction, as spirometrically defined, represent the vast majority of patients with COPD, yet this population has not been extensively studied. An insidious preclinical course means that mild COPD is both underdiagnosed and undertreated. In this context, recent studies have confirmed that even patients with mild COPD can have extensive physiological impairment, which contributes to poor perceived health status compared with non-smoking healthy controls. This review describes the heterogeneous pathophysiology that can exist in COPD patients with only mild airway obstruction on spirometry. It exposes the compensatory adaptations that develop in such patients to ensure that the respiratory system fulfils its primary task of maintaining adequate pulmonary gas exchange for the prevailing metabolic demand. It demonstrates that adaptations such as increased inspiratory neural drive to the diaphragm due to combined effects of increased mechanical loading and chemostimulation underscore the increased dyspnoea and exercise intolerance in this population. Finally, based on available evidence, we present what we believe is a sound physiological rationale for earlier diagnosis in this population.

Pulmonary effects of expiratory-assisted small-lumen ventilation during upper airway obstruction in pigs.

Novel devices for small-lumen ventilation may enable effective inspiration and expiratory ventilation assistance despite airway obstruction. In this study, we investigated a porcine model of complete upper airway obstruction. After ethical approval, we randomly assigned 13 anaesthetised pigs either to small-lumen ventilation following airway obstruction (n=8) for 30min, or to volume-controlled ventilation (sham setting, n=5). Small-lumen ventilation enabled adequate gas exchange over 30 min. One animal died as a result of a tension pneumothorax in this setting. Redistribution of ventilation from dorsal to central compartments and significant impairment of the distribution of ventilation/perfusion occurred. Histopathology demonstrated considerable lung injury, predominantly through differences in the dorsal dependent lung regions. Small-lumen ventilation maintained adequate gas exchange in a porcine airway obstruction model. The use of this technique for 30 min by inexperienced clinicians was associated with considerable end-expiratory collapse leading to lung injury, and may also carry the risk of severe injury.

Spontaneous Breathing Trial: A Reliable Method for Weaning in Children

Introduction Mechanical ventilation may be lifesaving intervention,It can be associated with complications,Thus,successful weaning is constitutive.One of the factors which is important in successful weaning is method of weaning. It is shown that weaning is conducted successfully by using Spontaneous Breathing Trial (SBT) through T-piece and pressure support (PS) ventilation.But few studies have not accepted it.In this study,we evaluated the role of SBT in extubation of patients in pediatric intensive care. Materials and Methods In a cross sectional and analytical study, three hundred sixty patients with adequate gas exchange (indicated by PaO2 higher than 60 mm/Hg while FIO2 of 0.40 or less (or PaO2 ∕ FIO2ratio> 300) were enrolled. Patients underwent a 2-hours trial of spontaneous breathing with pressure support ventilation.They were monitored during the test for 2 hours and were classified as failing the test if at any time in the 2-hours period ,there was tachypnea , excessive work of breathing,Tachycardia and SPO2<90%.Extubation failure was defind as needing reintubation within 72 hours of extubation. Results 240 patients(66%) of 360 patients successfully underwent SBT and were immediately extubated.In 120 patients(33%) ,the trial of spontaneous breathing was stopped.(trial failure;33% vs. 66% P=0.04). Of the 240 patients with successful SBT,29 patients were re-intubated (extubation failure) and 211 patients had successful extubation.(12% vs. 88% p=o.oo2).For patients experienced successful extubation ,the mortality rate was 5% While the rate of mortality was 27% in patients with needing re-intubation.(5% vs. 27% p= o.oo3) Conclusion The spontaneous breathing trial with pressure support prior to elective extubation may predict successful extubation in ventilated children.

A biomechanical model of pendelluft induced lung injury

Lung ventilation using high frequency oscillatory techniques have been documented to attain adequate gas exchange through various gas transport mechanisms. Among them, the pendelluft flow is considered one of the most crucial mechanisms. In this work, we computationally investigate the induction of abnormal mechanical stresses and a regionally trapped volume of gas due to pendelluft flow. Large eddy simulation was used to model the turbulence in an upper tracheobronchial lung geometry that was derived from CT scans. The pendelluft flow was captured by modeling physiological boundary conditions at the truncated level of the lung model that is sensitive to the coupled resistance and compliance of individual patients. The flow–volume and volume–pressure loops are characterized by irregular shapes and suggest abnormal regional lung ventilation. Incomplete loops were observed indicating gas trapping in these regions signifying a potential for local injury due to incomplete ventilation from a residual volume build-up at the end of the expiration phase. In addition, the gas exchange between units was observed to create a velocity gradient causing a region of high wall shear stress surrounding the carina ridges. The recurrence of the pendelluft flow could cause a rupture to the lung epithelium layer. The trapped gas and wall shear stress were observed to amplify with increasing compliance asymmetry and ventilator operating frequency. In general, despite the significant contribution of the pendelluft flow to the gas exchange augmentation there exists significant risks of localized lung injury, phenomena we describe as pendelluft induced lung injury or PILI.

How to measure alterations in alveolar barrier function as a marker of lung injury.

The alveolar capillary membrane maintains the proper water and solute content of the epithelial lining fluid at the alveolar air-liquid interface, which is critical for adequate gas exchange in the lung. This is possible due to the alveolar fluid clearance (AFC) capacity of this membrane that assists in the removal of salt and water from the alveolar air spaces. The alveolar capillary membrane also provides a barrier that restricts the passage of proteins and water from the interstitial and vascular compartments into the alveolar air spaces. This restricted passage is due to the presence of tight junctions between adjacent alveolar epithelial cells. Severe injury to the alveolar epithelial/endothelial membrane results in increased protein permeability and impairment of AFC, which leads to the formation of protein-rich edema with the consequent deterioration of gas exchange. Many animal models of lung injury, focused on damage of the alveolar-capillary membrane, assess the AFC capacity and the barrier function. We describe a simple method to assess the AFC rate in normal and pathological conditions in mice. We also describe two complementary methods to assess the alveolar-capillary barrier function, which require measuring the concentration of endogenous plasma proteins in bronchoalveolar lavage fluid and detection of tight-junction proteins in lung tissue by immunofluorescence.

Independent lung ventilation in the management of pneumothorax

Introduction: Independent lung ventilation (ILV) with double lumen endotracheal tube (DLt) or endobroncial blockade has a known role in managing pneumothorax or by isolating the diseased lung. We report a case in which ILV was used along with a bronchial blocker for treatment of severe persistent pneumothorax (PtX). case report: We report a 66-year-old female admitted with septic shock and respiratory failure from right lobar pneumonia who developed a rightsided pneumothorax. Despite the placement of two chest tubes, the patient had persistent acidosis and air leak. she required independent lung ventilation with a double lumen endotracheal tube and a bronchial blocker. this isolated the right lower lobe airleak and provided lung protective concordant positive pressure ventilation to the right middle and upper lobes. conclusion: Persistent air leaks in an intubated patient can be challenging. Our case highlights the concept of anatomical lung separation. With this clinicians can to allow provide isolation of the diseased lung, while using other subsegments to maintain adequate gas exchange. Muna Beg1, Pantea Mahtosh1, Sudhir Rajan1, Hekmat Nasiri1, Vincent Liu1,2 Affiliations: 1Kaiser Permanente Santa Clara Medical Center, Homestead Campus, 3rd floor, Department 384, 710 Lawrence Expressway, Santa Clara, CA 95051, USA; 2Kaiser Permanente Division of Research 2000 Broadway Oakland, CA 94612, USA. Corresponding Author: Muna Beg, MD, 1-562-481-4328, Kaiser Permanente Santa Clara Medical Center, Graduate Medical Education Department, Homestead Campus, 3rd floor, Department 384, 710 Lawrence Expressway, Santa Clara, CA 95051, USA; E-mail: Muna.a.beg@kp.org Received: 26 May 2015 Accepted: 02 June 2015 Published: 03 September 2015

Ventilation strategies in acute asthma

Status asthmaticus is a condition of progressively worsening bronchospasm and respiratory dysfunction due to asthma, which is unresponsive to standard conventional therapy and may progress to respiratory failure. Despite initial aggressive management a small proportion of patients require ventilatory support. Ventilation in asthma is complex and presents a big challenge to the pediatric intensivist, with mortality rates in patients requiring ventilation approaching as high as 10%. It requires careful personalized management. NIV is increasingly being used and its early initiation has shown to improve outcome and avoid endotracheal intubation in some recent studies. During mechanical ventilation, our first goal is to maintain adequate gas exchange and the second goal is to minimize the risk of air trapping and auto PEEP. These goals are best achieved by adopting the strategy of controlled hypoventilation and permissive hypoxemia initially. Once recovery starts the patient is shifted to assisted or spontaneous mode. A cautious application of PEEP up to 80% of auto PEEP can be tried at this stage. Further recovery should prompt the intensivist to rapidly wean and extubate the patient. Intense pharmacotherapy must continue throughout ventilation. Caie should be taken to choose the most appropriate device for delivery of the aerosolized bronchodilators. Higher doses may be required to achieve the desired effect.

Neurally adjusted ventilatory assist.

Purpose of reviewCompared with the conventional forms of partial support, neurally adjusted ventilatory assist was repeatedly shown to improve patient–ventilator synchrony and reduce the risk of overassistance, while guaranteeing adequate inspiratory effort and gas exchange. A few animal studies also suggested the potential of neurally adjusted ventilatory assist in averting the risk of ventilator-induced lung injury. Recent work adds new information on the physiological effects of neurally adjusted ventilatory assist.Recent findingsCompared with pressure support, neurally adjusted ventilatory assist has been shown to improve patient–ventilator interaction and synchrony in patients with the most challenging respiratory system mechanics, such as very low compliance consequent to severe acute respiratory distress syndrome and high resistance and air trapping due to chronic airflow obstruction; enhance redistribution of the ventilation in the dependent lung regions; avert the risk of patient–ventilator asynchrony due to sedation; avoid central apneas; limit the risk of high (injurious) tidal volumes in patients with acute respiratory distress syndrome of varied severity; and improve patient–ventilator interaction and synchrony during noninvasive ventilation, irrespective of the interface utilized.SummarySeveral studies nowadays prove the physiological benefits of neurally adjusted ventilatory assist, as opposed to the conventional modes of partial support. Whether these advantages translate into improvement of clinical outcomes remains to be determined.

Pre-clinical Evaluation of an Adult Extracoproreal Carbon Dioxide Removal System for Pediatric Application.

IntroductionAdult extracorporeal carbon dioxide removal (ECCO2R) systems and pediatric ECMO share the common objectives of having a low blood flow rate and low priming volume while safely maintaining sufficient respiratory support. The Hemolung is a highly simplified adult ECCO2R system intended for partial respiratory support in adult patients with acute hypercapnic respiratory failure. The objective of this work was to conduct pre-clinical feasibility studies to determine if a highly efficient, active-mixing, adult ECCO2R system can safely be translated to the pediatric population.Methods14 healthy nonsedated juvenile sheep were used for acute (2 animals) and 7-day chronic (12 animals) in-vivo studies to evaluate treatment safety independently of respiratory related injuries. In all evaluations, we hypothesized that gas exchange capabilities of the Hemolung RAS in this model would be equivalent to the adult configuration performance at similar blood flows - minimum CO2 removal of 50 mL/min at a venous partial pressure of CO2 equal to 45 mmHg. Target blood flow rates were set to a minimum of 280 mL/min. Swan Ganz catheters were used under general anesthesia in the two acute subjects to evaluate blood gas status in the pulmonary artery.ResultsThe Hemolung RAS was found to have adequate gas exchange and pumping capabilities for full respiratory support for subjects weighing 3 – 25 kg. The Hemolung device was estimated to provide a partial respiratory support for subjects weighing 27 – 34 kg. The seven-day studies in juvenile sheep demonstrated that veno-venous extracorporeal support could be provided safely at low flows with no significant adverse reactions related to device operation.ConclusionThe study outcomes suggest the potential use of the Hemolung RAS in a veno-venous pediatric configuration to safely provide respiratory support utilizing a significantly less complex system than traditional pediatric ECMO.

An extracorporeal artificial placenta supports extremely premature lambs for 1 week

PurposeThe treatment of extreme prematurity remains an unsolved problem. We developed an artificial placenta (AP) based on extracorporeal life support (ECLS) that simulates the intrauterine environment and provides gas exchange without mechanical ventilation (MV) and compared it to the current standard of neonatal care. MethodsExtremely premature lambs (110–120days; term=145d) were used. AP lambs (n=9) were cannulated (jugular drainage, umbilical vein reinfusion) for ECLS. Control lambs (n=7) were intubated, ventilated, given surfactant, and transitioned to high-frequency oscillatory ventilation. All lambs received parenteral nutrition, antibiotics, and steroids. Hemodynamics, blood gases, hemoglobin, and circuit flows were measured. ResultsFour premature lambs survived for 1week on the AP, with one surviving 6days. Adequate oxygenation and ventilation were provided by the AP. The MV lambs survived 2–8hours. Each of these lambs experienced a transient improvement with surfactant, but developed progressive hypercapnea and hypoxia despite high airway pressures and HFOV. ConclusionsExtremely premature lambs were supported for 1week with the AP with hemodynamic stability and adequate gas exchange. Mechanically ventilated lambs succumbed within 8hours. Further studies will assess control of fetal circulation and organ maturation on the AP.

Extracorporeal CO2removal as bridge to lung transplantation in life-threatening hypercapnia

In patients awaiting lung transplantation (LTX), adequate gas exchange may not be sufficiently achieved by mechanical ventilation alone if acute respiratory decompensation arises. We report on 20 patients with life-threatening hypercapnia who received extracorporeal CO2 removal (ECCO2-R) by means of the interventional lung assist (ILA®, Novalung) as bridge to LTX. The most common underlying diagnoses were bronchiolitis obliterans syndrome, cystic fibrosis, and idiopathic pulmonary fibrosis, respectively. The type of ILA was pumpless arteriovenous or pump-driven venovenous (ILA activve®, Novalung) in 10 patients each. ILA bridging was initiated in 15 invasively ventilated and five noninvasively ventilated patients, of whom one had to be intubated prior to LTX. Hypercapnia and acidosis were effectively corrected in all patients within the first 12h of ILA therapy: PaCO2 declined from 109 (70-146) to 57 (45-64) mmHg, P<0.0001; pH increased from 7.20 (7.06-7.28) to 7.39 (7.35-7.49), P<0.0001. Four patients were switched to extracorporeal membrane oxygenation due to progressive hypoxia or circulatory failure. Nineteen patients (95%) were successfully transplanted. Hospital and 1-year survival was 75 and 72%, respectively. Bridging to LTX with ECCO2-R delivered by arteriovenous pumpless or venovenous pump-driven ILA is feasible and associated with high transplantation and survival rates.

Early non-invasive ventilation for acute respiratory failure in immunocompromised patients (IVNIctus): study protocol for a multicenter randomized controlled trial.

BackgroundAcute respiratory failure (ARF) remains the leading reason for intensive care unit (ICU) admission of immunocompromised patients. In the most severe cases, high-flow oxygen therapy may fail to ensure adequate gas exchange, and mechanical ventilation (MV) must be used. This scenario is associated with high mortality rates of 40 to 60%, depending on the cause of ARF and type of immune deficiency. The use of non-invasive ventilation (NIV) in this situation has been criticized as potentially delaying the initiation of optimal treatment. In contrast, early NIV used prophylactically in patients with ARF who do not meet the criteria for invasive MV (IMV) may obviate the need for IMV, thereby decreasing the morbidity and mortality rates. We aim to demonstrate that a management strategy including early NIV decreases 28-day mortality rates compared to oxygen therapy alone in immunocompromised patients with ARF.Methods/DesignThis is a multicenter parallel-group randomized controlled trial comparing early NIV to oxygen therapy alone in immunocompromised patients with ARF. All immunocompromised adult patients admitted to admission for ARF are eligible for randomization. Patient with ARF onset more than 72 hours earlier or ARF related to cardiogenic pulmonary edema or hypercapnia, or with a need for immediate endotracheal intubation or other organ failure are not eligible.After inclusion patient are allocated to receive early NIV (intervention arm) or oxygen therapy only (control arm).We plan to enroll 374 patients in 29 ICUs. An interim analysis is planned after the inclusion of 187 patients. The main objective is to demonstrate early NIV increases survival as compared to oxygen therapy alone. Other outcomes include the need of IMV, organ failure evolution, nosocomial infections rate, 6 months survival.DiscussionThis study is expected to demonstrate an improved 28-day survival in immunocompromised patients managed with early NIV.Trial registrationRegistration number: Clinicaltrials.gov NCT01915719. Registered on 26 July 2013.Electronic supplementary materialThe online version of this article (doi:10.1186/1745-6215-15-372) contains supplementary material, which is available to authorized users.

Can computer simulators accurately represent the pathophysiology of individual COPD patients?

BackgroundComputer simulation models could play a key role in developing novel therapeutic strategies for patients with chronic obstructive pulmonary disease (COPD) if they can be shown to accurately represent the pathophysiological characteristics of individual patients.MethodsWe evaluated the capability of a computational simulator to reproduce the heterogeneous effects of COPD on alveolar mechanics as captured in a number of different patient datasets.ResultsOur results show that accurately representing the pathophysiology of individual COPD patients necessitates the use of simulation models with large numbers (up to 200) of compartments for gas exchange. The tuning of such complex simulation models ‘by hand’ to match patient data is not feasible, and thus we present an automated approach based on the use of global optimization algorithms and high-performance computing. Using this approach, we are able to achieve extremely close matches between the simulator and a range of patient data including PaO2, PaCO2, pulmonary deadspace fraction, pulmonary shunt fraction, and ventilation/perfusion (V̇/Q) curves. Using the simulator, we computed combinations of ventilator settings that optimally manage the trade-off between ensuring adequate gas exchange and minimizing the risk of ventilator-associated lung injury for an individual COPD patient.ConclusionsOur results significantly strengthen the credibility of computer simulation models as research tools for the development of novel management protocols in COPD and other pulmonary disease states.Electronic supplementary materialThe online version of this article (doi:10.1186/s40635-014-0023-0) contains supplementary material, which is available to authorized users.

Laparoscopic Repair of Duodenal Atresia in a Low Birth Weight Neonate

The small volume of the infant abdomen limits the application of laparoscopic procedures. We successfully repaired a duodenal atresia in a 2-kg female infant using a standard diamond-shaped anastomosis and intracorporeal suturing and knot-tying techniques. Anesthesia and positive pressure ventilation assured adequate gas exchange during pneumoperitoneum during the procedure.

Heat stress protects against mechanical ventilation-induced diaphragmatic atrophy.

Mechanical ventilation (MV) is a life-saving intervention in patients who are incapable of maintaining adequate pulmonary gas exchange due to respiratory failure or other disorders. However, prolonged MV is associated with the development of respiratory muscle weakness. We hypothesized that a single exposure to whole body heat stress would increase diaphragm expression of heat shock protein 72 (HSP72) and that this treatment would protect against MV-induced diaphragmatic atrophy. Adult male Wistar rats (n = 38) were randomly assigned to one of four groups: an acutely anesthetized control group (CON) with no MV; 12-h controlled MV group (CMV); 1-h whole body heat stress (HS); or 1-h whole body heat stress 24 h prior to 12-h controlled MV (HSMV). Compared with CON animals, diaphragmatic HSP72 expression increased significantly in the HS and HSMV groups (P < 0.05). Prolonged MV resulted in significant atrophy of type I, type IIa, and type IIx fibers in the costal diaphragm (P < 0.05). Whole body heat stress attenuated this effect. In contrast, heat stress did not protect against MV-induced diaphragm contractile dysfunction. The mechanisms responsible for this heat stress-induced protection remain unclear but may be linked to increased expression of HSP72 in the diaphragm.

Mechanical ventilation in acute hypoxemic respiratory failure: a review of new strategies for the practicing hospitalist.

The goal of mechanical ventilation in acute hypoxemic respiratory failure is to support adequate gas exchange without harming the lungs. How patients are mechanically ventilated can significantly impact their ultimate outcomes. This review focuses on emerging evidence regarding strategies for mechanical ventilation in patients with acute hypoxemic respiratory failure including: low tidal volume ventilation in the acute respiratory distress syndrome (ARDS), novel ventilator modes as alternatives to low tidal volume ventilation, adjunctive strategies that may enhance recovery in ARDS, the use of lung-protective strategies in patients without ARDS, rescue therapies in refractory hypoxemia, and an evidence-based approach to weaning from mechanical ventilation. Once a patient is intubated and mechanically ventilated, low tidal volume ventilation remains the best strategy in ARDS. Adjunctive therapies in ARDS include a conservative fluid management strategy, as well as neuromuscular blockade and prone positioning in moderate-to-severe disease. There is also emerging evidence that a lung-protective strategy may benefit non-ARDS patients. For patients with refractory hypoxemia, extracorporeal membrane oxygenation should be considered. Once the patient demonstrates signs of recovery, the best approach to liberation from mechanical ventilation involves daily spontaneous breathing trials and protocolized assessment of readiness for extubation. Prompt recognition of ARDS and use of lung-protective ventilation, as well as evidence-based adjunctive therapies, remain the cornerstones of caring for patients with acute hypoxemic respiratory failure. In the absence of contraindications, it is reasonable to consider lung-protective ventilation in non-ARDS patients as well, though the evidence supporting this practice is less conclusive.