Spontaneous Breathing Research Articles

Adaptive high flow oxygen therapy: New concept

Background High-flow oxygen therapy (HFOT) is increasingly utilized in clinical settings due to its potential to improve oxygenation, patient comfort and possibly outcomes in different respiratory failure states. The potential benefits of HFOT include matching the patients’ flow to reduce the work of breathing, creating airway pressure, humidification, and reducing dead space. However, it has some shortcomings including the difficulty of setting the flow to match patients’ efforts, the continuous flow does not represent normal physiologic spontaneous breathing, and the lack of traditional airway pressure monitoring. We are testing a new adaptive high-flow oxygen delivery technique “Auto Positive Airway Pressure” (Auto-PAP) where the flow delivered from the ventilator adapts to patients’ efforts taking into consideration the patients’ dead space Methods A bench study using ASL 5000 simulator, we created a single-compartment active model of a male with IBW 70 kg, with compliance of 40 ml/cmH20 and resistance of 10 cmH2o/L/s. The respiratory rate was set at 20 bpm, with inspiratory time of 1 second. Muscle pressure (Pmus) was gradually increased by increments of 5 cmH2O from 5 to 50. Adaptive high flow mode (Auto PAP) using a Bellavista 1000e ventilator (Zoll MA, USA) using a large bore nasal cannula to an adult-sized mannequin nose that was connected to the lung simulator. Pearson correlation coefficient was used in correlating the Pmus to the maximum, mean flow and pressure, and the simulator to the ventilator flow. Results There was significant strong correlation between the Pmus and the maximum flow R: 0.949, CI (0.794, 0.988) P < 0.001, and mean flow R: 0.955, P < 0.001, CI (0.816, 0.989). There was a significant strong correlation with Pmus and the maximum pressure R: 0.972, P < 0.001, CI (0.883, 0.993) and mean pressure R: 0.942, P < 0.001, CI (0.768, 0.986). There was significant strong correlation between the simulator and the ventilator flow R: 0.961, P < 0.001. There was significant strong correlation between the simulator and the ventilator mean pressure R: 0.951, P < 0.001, CI (0.799, 0.988). There was significant strong correlation between the mean flow from the ventilator to the mean airway pressure measured at the simulator R: 0.936, P < 0.001 CI (0.747, 0.985). Conclusion Results suggest a significant correlation between the flow and pressure from adaptive HFOT and the patient muscle effort, indicating that the flow and pressure increase in response to the patients’ effort. This may reduce respiratory muscle workload compared to traditional high flow oxygen therapies and reduce the need for multiple manual adjustment of the flow. These findings underscore the potential of this technology to enhance respiratory support while minimizing patient effort. Further research is warranted to validate these findings in real patient cohorts in diverse clinical scenarios. Keywords: High flow oxygen therapy, mean flow, mean pressure

Immediate effects of structured and natural deep breathing on heart rate variability and blood pressure in community-dwelling older adults

BackgroundThis study investigated the immediate effects of structured deep breathing (SDB) and natural deep breathing (NDB) on heart rate variability (HRV) and blood pressure (BP) in community-dwelling older adults. MethodsTwenty-six participants were randomly assigned to SDB (n = 14) or NDB (n = 12) groups. HRV parameters (time domain: standard deviation of normal-to-normal intervals [SDNN], root mean square of successive differences [RMSSD]; frequency domain: low frequency [LF], high frequency [HF], LF/HF ratio, total power [TP], normalized low frequency [LFnu], normalized high frequency [HFnu]) and BP were assessed during spontaneous breathing, DB, and post DB. ResultsBoth groups showed significant increases during DB in SDNN (p < 0.001), RMSSD (p = 0.021), LF power (p < 0.001), LFnu (p < 0.001), TP (p < 0.001), and LF/HF ratio (p < 0.001). HFnu decreased significantly during DB (p < 0.001) with no group differences. HF power showed no significant effect in group and time. BP remained stable throughout the protocol, with no significant changes in either systolic or diastolic BP across time points or between groups. ConclusionsThis first direct comparison of structured versus natural DB in healthy older adults demonstrates that both approaches effectively enhance parasympathetic activity. These findings support DB as a cost-effective, accessible intervention for promoting autonomic balance in healthy aging, without requiring specialized equipment or instruction.

Multi-domain analysis of ultra-short-term HRV for breathing pattern classification in wearable health devices

This research paper introduces an innovative approach to classify heart rate variability (HRV) time series into paced and spontaneous breathing patterns to reflect changes in the autonomic nervous system. This type of classification is beneficial in wearable devices for stress/relaxation level detection and in deciding therapeutic interventions. The “Multi-Domain Approach” methodology integrates three different techniques: standard HRV features, fuzzy recurrence plot (FRP)-based FRP_GLCM, and empirical mode decomposition-based IMF_FRP_GLCM. The study concentrates on analyzing HRV time series within shorter data segments, aligning with the requirements of contemporary wearable health devices and biofeedback systems. HRV data collected during spontaneous and slow-paced breathing were analyzed across data segments of 5, 4, 3, 2, and 1 min, incorporating feature selection and reduction methods. Results demonstrated that standard HRV features yielded optimal performance for 5-min segments, achieving an average accuracy of 90%. Interestingly, IMF_FRP features achieved comparable accuracy even for 1-min segments. As segment duration decreased, standard HRV feature accuracy declined while IMF_FRP accuracy stayed intact, eventually matching 5-min segment accuracy levels. The study underscores the surging demand for shorter data segment HRV analysis, driven by advancements in wearable smart watches technology and mobile applications for monitoring health and managing stress.

Noise-sensitivity during sleep in non-sedated mechanically ventilated patients is associated with weaning duration: a polysomnographic study.

Poor sleep is a major concern in intensive care units (ICUs), particularly in mechanically ventilated patients, because it is associated with longer duration of the weaning phase and higher mortality. High noise levels in ICUs are frequently reported by patients as one of the most disturbing sleep-disrupting factors but would be responsible for less than 20% of arousals. This suggests major inter-individual variability in noise sensitivity. Our objectives were to define and assess noise sensitivity in mechanically ventilated patients and to explore its association with sleep duration, sleep quality and weaning duration. We retrospectively re-analyzed polysomnographies (PSGs) recorded in 29 non-sedated patients, mechanically ventilated for at least 24h and difficult to wean (i.e. ≥ 1 spontaneous breathing trial failure). All the arousals were identified on all the PSGs. We calculated mean noise level and identified all noise peaks (an abrupt increase of noise intensity of more than 10 decibels (dBA)) preceding each arousal. Each 21-second period preceding each arousal was divided into seven 3-second bins. We built a pre-event time histogram for each PSG by counting the total number of noise peaks in each bin. If the total number of noise peaks in one bin exceeded the average of the seven bins plus 2 SD, we considered that there was a significant relationship between the number of noise peaks in this bin and the arousal. The patient was then considered as noise-sensitive. Presence of atypical sleep, proportion of sleep stages, and weaning duration were assessed. Nineteen out of 29 patients (66%) were noise-sensitive. Duration of weaning from ventilator was significantly longer in noise-insensitive patients (median [interquartile range] 2 [1-2] versus 5 [2-8] days; p < 0.01). Proportion of N1, N2, N3 sleep stages and rapid eye movement sleep were similar in noise-sensitive and noise-insensitive patients. In contrast, the proportion of patients displaying atypical sleep was higher in noise-insensitive patients. Our results report for the first time that most ICU patients were noise-sensitive. Lower noise sensitivity was associated with atypical sleep and could reflect lower brain reactivity to environment.

PRECORDIAL THUMP AS A LIFE-SAVING RESUSCITATION MEASURE IN OBESE PATIENTS DURING OUT-OF-HOSPITAL CARDIAC ARREST

Introduction: The precordial thump (PT) was until recently recognized as a life-saving measure for confirmed and monitored shockable rhythm cardiac arrest (CA) cases when a defibrillator is not immediately vailable, but cardiopulmonary resuscitation guidelines no longer mention it. Objectives: We present the PT as a life-saving measure during CA in obese patient. Case report: The emergency medical team intervened on a 69-year-old man, with, complaining of chest pain lasting &gt;1h. He was dyspneic, pale and clammy skin. RR 18/min, SatO2 89%, HR 76 bpm, BP of 80/50 mmHg. ECG: anterior ST elevation myocardial infarction with right bundle branch block. He was allergic to aspirin. He was treated with 180mg of oral ticagrelor, a 500ml saline solution IV and 4 l/min O2 by mask and then went into CA. Before the defibrillator became available, patient was treated with three PTs, an oropharyngeal airway placement, bag valve mask ventilation with 100% oxygen and the initiation of chest compressions. When the biphasic defibrillator arrived, the monitor showed coarse ventricular fibrillation. One DC shock with 200J of energy was delivered. After the shock, the patient regained consciousness, a pulse and spontaneous breathing. The ECG monitor showed a sinus rhythm of 143 bpm, BP 80/50 mmHg, and SatO2 89%. Conclusion: Although CPR guidelines no longer mention the PT, the question remains whether it could be an initial life-saving procedure during CA in obese patients.

Weaning of non COPD patients at high-risk of extubation failure assessed by lung ultrasound: the WIN IN WEAN multicentre randomised controlled trial

BackgroundPostextubation respiratory failure (PRF) frequently complicates weaning from mechanical ventilation and may increase morbidity/mortality. Noninvasive ventilation (NIV) alternating with high-flow nasal oxygen (HFNO) may prevent PRF.MethodsVentilated patients without chronic obstructive pulmonary disease (COPD) and at high-risk of PRF defined as a lung ultrasound score (LUS) ≥ 14 assessed during the spontaneous breathing trial, were included in a French-Chinese randomised controlled trial. PRF was defined by 2 among the following signs: SpO2 < 90%; Respiratory rate > 30 /min; hypercapnia; haemodynamic and/or neurological disturbances of respiratory origin. In the intervention group, prophylactic NIV alternating with HFNO was administered for 48 h following extubation. In the control group, conventional oxygen was used. Clinicians were informed on the LUS in the intervention group, those in the control group remained blind. The primary outcome was the incidence of PRF 48 h after extubation. Secondary outcomes were incidence of PRF and reintubation at day 7, number of ventilator-free days at day 28, length of ICU stay and mortality at day 28 and 90.ResultsTwo hundred and forty patients were randomised and 227 analysed (intervention group = 128 and control group = 99). PRF at H48 was reduced in the intervention group compared to the control group: relative risk 0.52 (0.31 to 0.88), p = 0.01. The benefit persisted at day 7: relative risk 0.62 (0.44 to 0.96), p = 0.02. Weaning failure imposing reconnection to mechanical ventilation was not reduced. In patients who developed PRF and were treated by rescue NIV, reintubation was avoided in 44% of control patients and in 12% of intervention patients (p = 0.008). Other secondary outcomes were not different between groups. From a resource utilisation standpoint, prophylactic NIV alternating with HFNO was more demanding and costly than conventional oxygen with rescue NIV to achieve same clinical outcome.ConclusionsCompared to conventional oxygenation, prophylactic NIV alternating with HFNO significantly reduced postextubation respiratory failure but failed to reduce reintubation rate and mortality in patients without COPD at high risk of extubation failure. Prophylactic NIV alternating with HFNO was as efficient as recue NIV to treat postextubation respiratory failure.

Caudal versus regional block with the use of ultrasound in pediatric analgesia: a systematic review of the main clinical results

Introduction: Regional anesthesia has been gaining prominence in recent decades. A variety of peripheral and central nerve blocks have been developed to ensure that perioperative pain can be effectively controlled. Caudal block is one of the most widely administered techniques of regional anesthesia, and the use of ultrasound has enabled the optimization and precision of the techniques. Objective: This study aimed to analyze the main clinical considerations and outcomes of ultrasound-guided caudal and regional block for pediatric analgesia. Methods: The systematic review rules of the PRISMA Platform were followed. The search was carried out from May to July 2024 in the Web of Science, Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 120 articles were found. 75 articles were evaluated and 27 were included in this systematic review. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 5 studies with a high risk of bias and 21 studies that did not meet GRADE. Most studies showed homogeneity in their results, with I2 = 18.7% &lt; 50%. All these techniques protect children from perioperative pain and, combined with periprocedural sedation, allow surgical interventions with spontaneous breathing in groups of patients with maximum risk of difficult airways. We consider this specific point the main advantage of regional anesthesia in pediatric patients. Ultrasound-guided caudal epidural, performed under sedation with a non-instrumented airway, is an effective technique in daily clinical routine; however, higher body weight and surgical procedures in the mid-abdomen are risk factors for pain-related block failure. Patients who, regardless of chronological age, were born as extremely premature infants have a higher risk of respiratory events. For bilateral inguinal hernia surgeries, ultrasound-guided caudal epidural block and transversus abdominis plane block showed similar analgesic efficacy in the first six hours postoperatively. Furthermore, ultrasound-guided lower limb peripheral nerve block is a simple and safe method to provide adequate and longer-lasting analgesia compared with ultrasound-guided caudal block for pediatric lower limb surgeries. Ultrasound-guided erector spinae block was safe and effective in pediatric patients undergoing unilateral lower abdominal surgery, as it provided longer-lasting analgesia and fewer analgesic requirements than caudal block and fewer side effects. In children undergoing regional anesthesia, the incidence of infection, hematoma, and local anesthetic toxicity is low.

Evaluation of abdominal expiratory muscle thickness pattern, diaphragmatic excursion, diaphragmatic thickness fraction and lung ultrasound score in critically ill patients and their association with weaning patterns: A prospective study

Abstract Introduction: Weaning of patient from ventilator and finally extubation is a challenge, especially in critical care setup. Though many parameters are available, based on which, the decision of extubation is taken but still many times, there is failure of weaning. Aim: We conducted a prospective observational study to look for diaphragm and abdominal muscle thickness, contraction, and lung ultrasound as indicator for weaning and extubation. Material and Methods: Patients of either gender aged between 20-50 years, who were on invasive mechanical ventilation for more than 48 hrs. and put on spontaneous breathing trial. A bedside ultrasound examination was performed. Abdominal expiratory muscle thickness, diaphragmatic excursion (DE), diaphragmatic thickness fraction (DTF) and lung ultrasound score (LUS) were measured. Results: 12 patients had simple weaning pattern whereas 5 patients had difficult weaning and 8 patients had prolonged weaning. The mean value of DE was 1.97 cm, DTF- 2.3 mm. The mean value of SOFA score is significant between simple, difficult, prolonged weaning (2.24, 4.56, 7.33 respectively). The DE, which is 2.52, 1.26, 1.81 in simple difficult and prolonged weaning respectively is highly significant. The mean value of LUS was 8.34 and is significant in all weaning patterns. The highest sensitivity is found for SOFA score (84.62) with AUC of 0.88. Conclusion: Evaluation of patient with diaphragm thickness fraction (mean DTF of 26%) and diaphragm excursion (2.52 cm) with mean LUS score of 4.67 opens a new dimension to predict weaning in critically ill patients who are put on spontaneous breathing trial. The sequence of thickness of abdominal expiratory muscles adds to accuracy in successful weaning. Larger muti-center trials are required to make these parameters as a standard practice for weaning patients in critical care setup.

Chemogenetic stimulation of phrenic motor output and diaphragm activity.

Impaired respiratory motor output contributes to morbidity and mortality in many neurodegenerative diseases and neurologic injuries. We investigated if expressing designer receptors exclusively activated by designer drugs (DREADDs) in the mid-cervical spinal cord could effectively stimulate phrenic motor output to increase diaphragm activation. Two primary questions were addressed: 1) does effective DREADD-mediated diaphragm activation require focal expression in phrenic motoneurons (vs. non-specific mid-cervical expression), and 2) can this method produce a sustained increase in inspiratory tidal volume? Wild type (C57/bl6) and ChAT-Cre mice received bilateral intraspinal (C4) injections of an adeno-associated virus (AAV) encoding the hM3D(Gq) excitatory DREADD. In wild-type mice, this produced non-specific DREADD expression throughout the mid-cervical ventral horn. In ChAT-Cre mice, a Cre-dependent viral construct was used to drive neuronal DREADD expression in the C4 ventral horn, targeting phrenic motoneurons. Diaphragm EMG was recorded in isoflurane-anesthetized spontaneously breathing mice at 4-9 weeks post-AAV delivery. The DREADD ligand JHU37160 (J60) caused a bilateral, sustained (>1 hour) increase in inspiratory EMG bursting in both groups; the relative increase was greater in ChAT-Cre mice. Additional experiments in ChAT-Cre rats were conducted to determine if spinal DREADD activation could increase inspiratory tidal volume (VT) during spontaneous breathing, assessed using whole-body plethysmography without anesthesia. Three-to-four months after intraspinal (C4) injection of AAV driving Cre-dependent hM3D(Gq) expression, intravenous J60 resulted in a sustained (>30 min) increase in VT. Subsequently, phrenic nerve recordings performed under urethane anesthesia confirmed that J60 evoked a > 200% increase in inspiratory output. We conclude that targeting mid-cervical spinal DREADD expression to the phrenic motoneuron pool enables ligand-induced, sustained increases in phrenic motor output and VT. Further development of this technology may enable application to clinical conditions associated with impaired diaphragm activation and hypoventilation.

Modeling ventilation of patients with interstitial lung disease at rest and exercise: a bench study

BackgroundThe ventilatory physiopathology of patients with interstitial lung disease (ILD) remains poorly understood. We aimed to personalize a mechanical simulator to model healthy and ILD profiles ventilation, and to evaluate the effect of spontaneous breathing on respiratory mechanics at rest and during exercise.MethodsIn a 2-compartment lung simulator (ASL 5000®), we modeled 1 healthy and 3 ILD profiles, at rest and during exercise, based on physiological data from literature and patients. Measurements were: tidal volume, end-expiratory lung volume, driving pressure, transpulmonary driving pressure, dynamic alveolar strain, mechanical power, and time lag of inspiratory flow between compartments 1 and 2.ResultsHealthy and ILD models were validated: maximum differences between real and simulated tidal volume were 5% (96 ml) and 6% (54 ml) at rest and during exercise respectively, considered clinically negligible. When we simulated lung inhomogeneity (compliance in compartment 1 > compartment 2), tidal volume, end-expiratory lung volume, driving pressure and mechanical power increased in compartment 1 and decreased in compartment 2. Driving transpulmonary pressure and dynamic alveolar strain increased in compartment 2 and decreased in compartment 1. Time lag of inspiratory flow between compartments 1 and 2 was positively correlated with a difference of compliance between compartments (r = 0.98, CI95% (0.9106; 0.9962), p < 0.0001).ConclusionIn this bench study, we personalized a mechanical simulator thatmodels the lung inhomogeneity and spontaneous breathing of healthy subjects and ILD patients at rest and during exercise. Our results suggest that lung inhomogeneity could increase lung vulnerability to volo-atelec-trauma mechanisms in ILD. Further physiological studies are needed to evaluate the impact of this vulnerability on acute or chronic ILD worsening.

Effect of high-frequency oscillatory ventilation with intermittent sigh breaths on carbon dioxide levels in neonates.

High-frequency oscillatory ventilation (HFOV) minimizes ventilator-induced lung injuries. Spontaneous sigh breathing may augment the functional residual capacity, increase lung compliance, and recruit atelectatic alveoli. To evaluate the difference in the partial pressure of carbon dioxide (PaCO2) in neonates receiving invasive HFOV as the primary mode of respiratory support before versus after sigh breaths (Sighs). This prospective study was conducted between January and December 2023. Intubated preterm and term neonates who underwent HFOV with an available arterial line were enrolled in this study after informed parental consent was obtained. Sighs were set at a frequency of 3 breaths/min and pressure of 5 cm H2O above the mean airway pressure for 2 hours. Arterial blood gas was collected before and after Sighs and analyzed using two dependent tests. Thirty neonates with a mean gestational age of 33.6±4.1 weeks and median date of intervention of 1.88 (interquartile range, 0.87-3.79) days were enrolled. The mean PaCO2 level was significantly lower in the HFOV with Sighs group (45.2±6.6 mm Hg) versus the HFOV alone group (48.8±3.1 mm Hg) with a mean difference (MD) of -3.6 mm Hg (95% confidence interval [CI], -6.3 to -0.9; P=0.01). Subgroup analyses indicated the ability of Sighs to reduce the PaCO2 level in neonates with respiratory distress syndrome (n=15; MD [95% CI] = -4.2 [-8.2 to -0.2] mm Hg; P=0.04).

Abstract 4135318: Comparison of Right Ventricular Function Changes Between Volume Control and Pressure Support Ventilation Modes: A Prospective Study Using S' Prime Values

Background: This study assesses changes in right ventricular function by measuring S' values during the transition from volume control-assist control (VC-AC) to pressure support ventilation (PSV). Transitioning from VC-AC to PSV reduces the mean airway pressure (P mean) which causes a decrease in right ventricular afterload and also potentially improves venous return and right ventricular preload. PSV allows spontaneous breathing efforts, possibly increasing cardiac output. Thus, we expect a consistent increase in S' value when changing ventilator modes. Methods: This prospective observational study included ICU patients on invasive mechanical ventilation for over 24 hours. The clinical team decided when to switch from VC-AC to PSV. An average of three S' measurements was taken during VC-AC and within 10 minutes of transitioning to PSV. Sedation, vasopressor use, and Richmond Agitation-Sedation Scale scores were consistent throughout the measurements. The study was approved by the Albert Einstein College of Medicine IRB (#2023-15068) Results: Seventeen patients were included in the study, with an average age of 61.29 years (SD 11.39). Of these, 6 (35.3%) were female. The mean S' during VC-AC was 12.79 ± 4.52, and upon transitioning to PSV, it was 14.56 ± 3.89 (p-value 0.47). The intra-observer variability for S' was 5.3%. Of the seventeen patients, 5/17 (29%) showed an S' change of less than 5.3% and were deemed to have no significant variation; 7/17 (41%) experienced a significant decrease in S' (15.41% ± 7.29% SD), while the remaining 5/17 (29%) showed a significant increase (19.31 ± 13.23%). Conclusion: Our study demonstrates that transitioning from VC-AC to PSV results in variable changes in right ventricular systolic function, as indicated by S' values. Contrary to our expectations of a consistent increase, the interplay between S' values and ventilator mode changes appears to be non-linear, suggesting other factors may influence cardiopulmonary interactions in spontaneously breathing ventilated patients. These findings highlight the complexity of these interactions, underscoring the need for individualized patient management and paving the way for further research with a larger cohort.

Abstract 4137205: Management Patterns and Outcomes in the Use of Invasive Mechanical Ventilation for Patients with Cardiogenic Shock

Background: Approximately half of all patients with cardiogenic shock (CS) require invasive mechanical ventilation (IMV). While there have been significant advances in the management of patients requiring IMV based on data primarily derived from medical intensive care patients with respiratory failure, little is known regarding the management and outcomes of IMV in patients with CS. Methods: We conducted an analysis of patients treated for CS who required IMV at an academic safety net hospital from 2017-2023. Indications for IMV, ventilator settings, and medications were obtained from the medical record. The primary outcome was unsuccessful extubation, defined as reintubation within 48 hours of extubation. Results: A total of 110 patients with CS who received IMV were identified. Median age was 60yo; 28% of the cohort was female, 39% of Hispanic ethnicity, and 38% of Black race. Primary reasons for intubation included ongoing cardiac arrest (35%) and hypoxic respiratory failure (34%). Most patients were on minimal ventilator support at 24 hours after intubation (median FiO2 40% [IQR 30-50%], post-end expiratory pressure [PEEP] 5cm H2O [IQR 5-8]). Mechanical circulatory support (MCS) was present in 40% of patients at 24 hours post-intubation. Protocolized spontaneous breathing trials (SBTs) were delayed in 77% of patients, primarily due to hemodynamic instability (88%). Planned or unplanned extubation occurred in 63% of patients after a median of 4.8 days [IQR 2.1-8.0]. Ten percent of patients transferred hospitals while on IMV, while 27% were palliatively extubated or died on IMV. The majority (58%) of patients undergoing non-palliative extubation were on vasoactive medications preceding extubation, with only 2% on MCS. Most patients (58%) were extubated to nasal cannula or room air. A total of 13% of patients experienced unsuccessful extubation. Conclusions: In a cohort of patients with CS requiring IMV, most patients were on minimal ventilator settings within 24 hours yet remained intubated with SBTs delayed due to hemodynamic instability. Rates of failed extubation were comparable to published data from other forms of critical illness. Further work is necessary to determine optimal approaches to ventilator liberation and circulatory support in intubated patients with CS where hemodynamic derangements rather than respiratory insufficiency represent the primary barrier to extubation.

Spontaneous breathing-induced lung injury in mechanically ventilated patients.

Recent experimental and clinical studies have suggested that spontaneous effort can potentially injure the lungs. This review summarizes the harmful effects of spontaneous breathing on the lungs during mechanical ventilation in ARDS and suggests potential strategies to minimize spontaneous breathing-induced lung injury. Recent clinical and experimental studies have shown that vigorous spontaneous breathing during mechanical ventilation can potentially injure the lungs due to high transpulmonary pressure, the Pendelluft phenomenon, increased pulmonary perfusion, and patient-ventilator asynchrony. A definitive approach to minimize spontaneous breathing-induced lung injury is the systemic use of neuromuscular blocking agents; however, there is a risk of muscle atrophy. Alternatively, partial paralysis, bilateral phrenic nerve blockade, and sedatives may be useful for decreasing force generation from the diaphragm while maintaining muscle function. A higher positive end-expiratory pressure (PEEP) and prone positioning may reduce force generation from the diaphragm by decreasing neuromechanical efficiency. Several potential strategies, including neuromuscular blockade, partial paralysis, phrenic nerve blockade, sedatives, PEEP, and prone positioning, could be useful to minimize spontaneous breathing-induced lung injury.

Management of sedation during weaning from mechanical ventilation.

Critically ill patients frequently require mechanical ventilation and often receive sedation to control pain, reduce anxiety, and facilitate patient-ventilator interactions. Weaning from mechanical ventilation is intertwined with sedation management. In this review, we analyze the current evidence for sedation management during ventilatory weaning, including level of sedation, timing of sedation weaning, analgesic and sedative choices, and sedation management in acute respiratory distress syndrome (ARDS). Despite a large body of evidence from the past 20 years regarding the importance of light sedation and paired spontaneous awakening and spontaneous breathing trials (SATs/SBTs) to promote ventilator weaning, recent studies show that implementation of these strategies lag in practice. The recent WEAN SAFE trial highlights the delay between meeting weaning criteria and first weaning attempt, with level of sedation predicting both delays and weaning failure. Recent studies show that targeted interventions around evidence-based practices for sedation weaning improve outcomes, though long-term sustainability remains a challenge. Light or no sedation strategies that prioritize analgesia prior to sedatives along with paired SATs/SBTs promote ventilator liberation. Dexmedetomidine may have a role in weaning for agitated patients. Further investigation is needed into optimal sedation management for patients with ARDS.

Rapid Shallow Breathing Index and Ultrasonographic Diaphragmatic Parameters as Predictors of Weaning Outcome in Critically Ill Patients on Mechanical Ventilation.

Successful weaning is a crucial element in care toward critically ill patients on mechanical ventilation. An attempt was made to propose and assess a reliable predictor of weaning outcome. A prospective observational study was conducted on 76 patients on mechanical ventilation, assessed by Acute Physiology and Chronic Health Evaluation II (APACHE II) score. For all these patients we calculate Rapid shallow breathing index (RSBI), Ultrasonographic diaphragmatic parameters namely diaphragmatic excursion (DEx), diaphragmatic thickening fraction (DTF) and diaphragmatic contraction velocity (DCV). Values were compared among patients with two groups of successful and failed weaning outcomes, respectively, and statistically analyzed. Of 76 patients included in the study, with ultrasonographic diaphragmatic parameters being measured 30 min into SBT, 71 patients tolerated spontaneous breathing test (SBT) for 2 h and were extubated. Of these, 61 patients did not require reintubation or any form of ventilatory support within 48 h after extubation. There was a statistically significant difference in APACHE II scores, duration of ventilation, oxygen saturation levels, RSBI, DEx, DTF, and DCV between groups of patients who showed successful and failed weaning from mechanical ventilation. There were a significant positive correlation between the duration of ventilation and the RSBI and a significant negative correlation between DEx, DCV, DTF, and duration of ventilation. As predictors of weaning outcome, RSBI showed the best validity, followed by DCV, DTF, and DEx. RSBI can be reliably used as a predictor of weaning outcome in critically ill patients on mechanical ventilation.

Humidified Noninvasive Ventilation versus High-Flow Therapy to Prevent Reintubation in Obese Patients: A Randomized Clinical Trial.

The optimal strategy to prevent reintubation in obese patients remains uncertain. We aimed to determine whether noninvasive ventilation (NIV) with active humidification is superior to high-flow nasal cannula (HFNC) in preventing reintubation in obese patients at intermediate risk. Randomized controlled trial in two intensive care units in Spain (June 2020‒June 2021). We included patients ready for planned extubation with a body mass index (BMI) >30 and ≤3 risk factors for reintubation. Patients with hypercapnia at the end of the spontaneous breathing trial were excluded. Patients were randomized to undergo NIV with active humidification or HFNC for 48 hours after extubation. The primary outcome was reintubation rate within 7 days after extubation. As a secondary analysis, we performed a post hoc Bayesian analysis using three different priors. Of 144 patients (median age, 61 [p25-p75 61-67] years; 65 [45%] men), 72 received NIV and 72 HFNC. Reintubation was required in 17 (23.6%) patients receiving NIV and in 24 (33.3%) patients receiving HFNC (difference between groups 9.7 (95%CI: -4.9 ‒ 24.4)). All the secondary analysis showed non-significant differences. In the exploratory Bayesian analysis, the probability of a reduction in reintubation with NIV was 99% (data-driven prior), 90% (minimally informative prior), or 89% (skeptical prior). Among adult obese critically ill patients at intermediate risk for extubation failure, the rate of reintubation was not significantly lower with NIV than with HFNC. Nevertheless, there is a risk for underpowered results. Clinical trial registration available at www. gov, ID: NCT04125342.

Pericardial Fenestration With Monitored Anesthesia Care Using Diluted Remifentanil: A Series of 10 Cases.

Introduction Monitored anesthesia care (MAC) is an anesthesia management method in which anesthesiologists use the minimum necessary intravenous anesthetics to achieve sedation and pain relief while maintaining spontaneous breathing. The challenge for the anesthesiologist is to find the correct balance between inhibiting the patient's stress response to invasive treatment, maintaining intraoperative hemodynamic stability, and doing so as quickly as possible. We hypothesized that diluting remifentanil (D-remi) to 10 μg/mL and increasing the rate of administration would increase the responsiveness of the syringe pump and allow for better control of anesthetic depth. In this study, we aimed to evaluate the efficacy of MAC with D-remi in critically ill patients. Materials We investigated 10 cases in which anesthesia was managed by MAC with D-remi during emergency pericardial fenestration after cardiovascular surgery at our institution. Each parameter related to the patients' background and circulatory dynamics was extracted retrospectively from the electronic medical records and anesthesia records. The target depth of anesthesia was set at Richmond Agitation-Sedation Scale (RASS) -3 to -4 on MAC with spontaneous breathing. We increased the infusion rate of this analgesic during more invasive procedures. Results In all cases, the emergency pericardial fenestration could be performed with stable hemodynamics throughout the procedure. Spontaneous respiration never disappeared in any case. Although there were six cases in which airway maintenance by mandibular elevation was required due to glossoptosis, the minimum intraoperative SpO2was as high as 94% (92-100%), and none of the cases dropped below 92%. Conclusions The improved responsiveness of syringe pumps through the use of D-remi may be advantageous in situations where the infusion rate of anesthetic needs to be adjusted frequently and quickly. Since this is a small case study, we view our results cautiously and hope that further investigation of the usefulness of D-remi in MAC, including large-scale randomized studies, will be conducted in the future.

Short (30 Minutes) versus long (120 Minutes) spontaneous breathing trial among patients with difficult weaning (SL-SBT Trial)

BackgroundThe optimal duration of spontaneous breath trial (SBT) for patients with difficult extubation from mechanical ventilation is unknown. ObjectiveThis study compared extubation success with two different durations of SBT in patients who failed their first SBT. MethodsThis single-center randomized controlled trial included adults on mechanical ventilation who had failed their first SBT. The participants were randomized to receive pressure support ventilation (PSV) for either 30 or 120 min. Our primary outcome was the rate of successful extubation (without reintubation within 48 h). Key secondary outcomes were the length of intensive care unit (ICU) and hospital stay and in-hospital and 90-day mortality. ResultsA total of 119 patients (62.2 % male) with a mean age of 53.9 years were randomized to undergo SBT for either 30 min (n = 60) or 120 min (n = 59). Among them, 82.4 % of patients had hypercapnic respiratory failure. The rates of successful extubation were similar with SBT of 30 min and 120 min (58.3 % vs. 59.3 %, respectively; p = 0.91). There were no significant differences between the two groups in terms of the durations of ICU and hospital stay or in-hospital and 90-day mortality. ConclusionsExtubation success and other clinically important outcomes were comparable between short (30 min) and long (120 min) SBT in difficult weaning. A 30-minute SBT may be acceptable in this setting.

How to prevent postextubation respiratory failure.

Postextubation respiratory support treatment approaches, indications, and subgroups of patients with different responses to those therapies are rapidly changing. Planning optimal therapy in terms of choosing devices, timing of application and selecting settings with the goal of minimizing extubation failure is becoming a challenge. This review aims to analyze all the available evidence from a clinical point of view, trying to facilitate decision making at the bedside. There is evidence for high flow nasal cannula support in patients at low risk of extubation failure. Noninvasive ventilation based strategies should be prioritized in patients at very high risk, who are obese or are hypercapnic at the end of a spontaneous breathing trial. Patients not included in the previous groups merit a tailored decision based on more variables.Optimizing the timing of therapy can include facilitation of extubation by transitioning to noninvasive respiratory support or prolonging a planned preventive therapy according to clinical condition. Planning postextubatin respiratory support must consider the risk for failing and the presence of some clinical conditions favoring noninvasive ventilation.Extubation can be safely accelerated by modifying screening criteria and spontaneous breathing trial settings, but there is room to increase the role of postextubation noninvasive respiratory support for this indication, always keeping in mind the dangers of delaying a needed intubation.