Ventilator Settings Research Articles

Improved ventilation efficiency due to continuous gas flow compared to decelerating gas flow in mechanical ventilation: results of a porcine trial.

In pressure-controlled ventilation (PCV), a decelerating gas flow pattern occurs during inspiration and expiration. In contrast, flow-controlled ventilation (FCV) guarantees a continuous gas flow throughout the entire ventilation cycle where the inspiration and expiration phases are simply performed by a change of gas flow direction. The aim of this trial was to highlight the effects of different flow patterns on respiratory variables and gas exchange. Anesthetized pigs were ventilated with either FCV or PCV for 1 h and thereafter for 30 min each in a crossover comparison. Both ventilation modes were set with a peak pressure of 15 cmH2O, positive end-expiratory pressure of 5 cmH2O, a respiratory rate of 20/min, and a fraction of inspired oxygen at 0.3. All respiratory variables were collected every 15 min. Tidal volume and respiratory minute volume were significantly lower in FCV (n = 5) compared with PCV (n = 5) animals [4.6 vs. 6.6, MD -2.0 (95% CI -2.6 to -1.4) mL/kg; P < 0.001 and 7.3 vs. 9.5, MD -2.2 (95% CI -3.3 to -1.0) L/min; P = 0.006]. Notwithstanding these differences, CO2-removal as well as oxygenation was not inferior in FCV compared with PCV. Mechanical ventilation with identical ventilator settings resulted in lower tidal volumes and consecutive minute volume in FCV compared with PCV. This finding can be explained physically by the continuous gas flow pattern in FCV that necessitates a lower alveolar pressure amplitude. Interestingly, gas exchange was comparable in both groups, which is suggestive of improved ventilation efficiency at a continuous gas flow pattern.NEW & NOTEWORTHY This study examined the effects of a continuous (flow-controlled ventilation, FCV) vs. decelerating (pressure-controlled ventilation, PCV) gas flow pattern during mechanical ventilation. It was shown that FCV necessitates a lower alveolar pressure amplitude leading to reduced applied tidal volumes and consequently minute volume. Notwithstanding these differences, CO2-removal as well as oxygenation was not inferior in FCV compared with PCV, which is suggestive of improved gas exchange efficiency at a continuous gas flow pattern.

Nasopharyngeal Ventilation Compared to Facemask Ventilation: A Prospective, Randomized, Crossover Trial in Two Different Elective Cohorts.

Facemask ventilation is routinely used to preoxygenate patients before endotracheal intubation during anesthesia induction or to secure ventilation in patients with respiratory insufficiency. Occasionally, facemask ventilation cannot be performed adequately. The placement of a regular endotracheal tube through the nose into the hypopharynx may be a valid alternative to improve ventilation and oxygenation before endotracheal intubation (nasopharyngeal ventilation). We tested the hypothesis that nasopharyngeal ventilation is superior in its efficacy compared to traditional facemask ventilation. In this prospective, randomized, crossover trial, we enrolled surgical patients requiring either nasal intubation (cohort #1, n = 20) or patients who met "difficult to mask ventilate" criteria (cohort #2, n = 20). Patients in each cohort were randomly assigned to receive pressure-controlled facemask ventilation followed by nasopharyngeal ventilation or vice versa. The ventilation settings were kept constant. The primary outcome was tidal volume. The secondary outcome was the difficulty of ventilation, measured using the Warters grading scale. Tidal volume was significantly increased by nasopharyngeal ventilation in cohort #1 (597 ± 156 ml vs.462 ± 220 ml, p = 0.019) and cohort #2 (525 ± 157 ml vs.259 ± 151 ml, p < 0.01). Warters grading scale for mask ventilation was 0.6 ± 1.4 in cohort #1, and 2.6 ± 1.5 in cohort #2. Patients at risk for difficult facemask ventilation may benefit from nasopharyngeal ventilation to maintain adequate ventilation and oxygenation before endotracheal intubation. This ventilation mode may offer another option for ventilation at induction of anesthesia and during the management of respiratory insufficiency, especially in the setting of "unexpected" ventilation difficulty.

Ventilator associated events:incidence, microbiological profile and outcome in the intensive care unit in a tertiary hospital of eastern Nepal

Ventilator associated events (VAE) refer to new surveillance definition developed by Centre for Disease Control and prevention (CDC)/ National Healthcare Safety Network (NHSN) is in use since the year 2013, switching the focus of surveillance from ventilator associated pneumonia (VAP) to ventilator associated events (VAE). A number of studies have been conducted in the United States and other Western countries to evaluate its practicality. However, information on VAE in Asian countries is scarce. The purpose of this preliminary study was to illuminate the incidence and microbiological profile of VAEs in tertiary hospital in Nepal, as a first step in the effort to determine its practicality.The objective of the study was to determine the incidence, etiological agent and mortality of VAE in patients on mechanical ventilation in medical Intensive care unit (ICU) of a tertiary hospital. Patients admitted in ICU on Mechanical Ventilation were evaluated daily using the VAE surveillance criteria. At least 2 days of stable or decreasing ventilator settings followed by at least 2 days of increased ventilator settings was used as definition of VAE. Three tiered approach of VAE, namely Ventilator-Associated Condition (VAC), Infection-related Ventilator-Associated Complication (IVAC) and Possible VAP (PVAP) was used for the final classification of cases. Of the 313 patients admitted to the ICU over the period of one year, 52 patients received MV for ≥2 days and met baseline criteria for VAEs Surveillance. Out of 52 patients, 14(27%) developed VAC only, 13(25%) developed IVAC only and 25(48%) patients developed PVAP. Endotracheal aspirate culture was positive in 25 patients (48%). The organisms isolated 14(53.84%), 7(26.92%), 4(15.38%), and 1(3.84%). Polymicrobial growth was observed in one Almost all the isolates 25 (96%) being multidrug resistant. Overall mortality rate in patients with VAE was 36.5% with highest mortality rate in PVAP (44%). Early onset PVAP was observed in 9 (36%) where as 16 (64%) had late‑ onset VAP.VAE mostly being health care associated event and prevalence of multidrug resistance in as observed in this study warrant clinician to practices infection control measures and rationale use of antimicrobials as effective measures for infection control.

508 Retrospective Review of Early Pulmonary Mechanics After Inhalation Injury

Abstract Introduction Management of inhalation injury is largely supportive and consists primarily of mechanical ventilation, bronchodilators, muscarinic receptor antagonists, and inhaled mucolytics and anticoagulants. The purpose of this study is to examine the early changes in pulmonary mechanics after inhalation injury and see if the use of NT affects lung function. Methods Retrospective study was done on Inhalation injury patients over a 12 years period from 01/2009 to 01/2021. Patients’ data collected from their medical records, included patient demographics and outcomes, percentage Total Body Surface Area (TBSA), Carboxyhemoglobin level upon admission, Respiratory Treatments (bronchodilator, Mucolytic and Heparin), Tobramycin treatment, Oxygen requirement, Lung compliance (peak airway pressure &amp; Mean airway Pressure), Mode of Ventilation, total Ventilator Day, and number of Hospital Days. Patients with inhalation injury from 2009-2019 were retrospectively reviewed for treatment of inhalation injury. Univariate analysis and multiple logistic regression were performed using Excel and Stata. Results Of 90 patients with inhalation injury, median age was 53.5 (IQR:31-65) with 30% (n=28) women and median TBSA of 15%(IQR:2-38%). The median length of stay was 21 days (IQR:6-47). Median ventilator days was (8.5, IQR:3-21) and median ICU days was 12 (IQR:3-28). After adjusting for grade of inhalation injury, patients who did not receive NT were 2.7 times as likely to get pneumonia compared to patients who received NT (p=0.037). Initial median carboxyhemoglobin was 3.9 (IQR: 2-9.1). Overall mortality was 21%, but the incidence of death increased with grade of injury The Median Mean Airway Pressures were Day 1: 9.5mmHg, Day 2: 11mmHg, Day 3: 13mmHg, Day 4: 12mmHg The median peak pressures were Day 1; 20mmHg, Day 2: 21mmHg; Day 3: 22.5mmHg; Day 4: 21mmHg Conclusions Patients with inhalation injury are susceptible to Acute Respiratory Distress Syndrome, indicated by a decrease in lung compliance and increase in the patient’s oxygenation support. The lung compliance of these patients being to change resulting in an increase in their Peak Airway Pressure and Mean Airway Pressure within the first 72 hours. Moderate hypoxemia is present in these patients with the progress of the smoke inhalation injury. The usage of NT did not have a direct benefit to the pulmonary mechanics for inhalation injury when used as a prophylactic strategy. Additional research and clinical trials are needed to better understand the effect of inhalation injury on pulmonary mechanics. Applicability of Research to Practice Analysis of pulmonary mechanics in patients with inhalation injury can allow clinicians to better tailor ventilator settings to improve clinical outcomes.

Modulation of pulmonary blood flow in patients with acute respiratory failure

BackgroundImpairment of ventilation and perfusion (V/Q) matching is a common mechanism leading to hypoxemia in patients with acute respiratory failure requiring intensive care unit (ICU) admission. While ventilation has been thoroughly investigated, little progress has been made to monitor pulmonary perfusion at the bedside and treat impaired blood distribution. The study aimed to assess real-time changes in regional pulmonary perfusion in response to a therapeutic intervention. MethodsSingle-center prospective study that enrolled adult patients with ARDS caused by SARS-Cov-2 who were sedated, paralyzed, and mechanically ventilated. The distribution of pulmonary perfusion was assessed through electrical impedance tomography (EIT) after the injection of a 10-ml bolus of hypertonic saline. The therapeutic intervention consisted in the administration of inhaled nitric oxide (iNO), as rescue therapy for refractory hypoxemia. Each patient underwent two 15-min steps at 0 and 20 ppm iNO, respectively. At each step, respiratory, gas exchange, and hemodynamic parameters were recorded, and V/Q distribution was measured, with unchanged ventilatory settings. ResultsTen 65 [56–75] years old patients with moderate (40%) and severe (60%) ARDS were studied 10 [4-20] days after intubation. Gas exchange improved at 20 ppm iNO (PaO2/FiO2 from 86 ± 16 to 110 ± 30 mmHg, p = 0.001; venous admixture from 51 ± 8 to 45 ± 7%, p = 0.0045; dead space from 29 ± 8 to 25 ± 6%, p = 0.008). The respiratory system's elastic properties and ventilation distribution were unaltered by iNO. Hemodynamics did not change after gas initiation (cardiac output 7.6 ± 1.9 vs. 7.7 ± 1.9 L/min, p = 0.66). The EIT pixel perfusion maps showed a variety of patterns of changes in pulmonary blood flow, whose increase positively correlated with PaO2/FiO2 increase (R2 = 0.50, p = 0.049). ConclusionsThe assessment of lung perfusion is feasible at the bedside and blood distribution can be modulated with effects that are visualized in vivo. These findings might lay the foundations for testing new therapies aimed at optimizing the regional perfusion in the lungs.

Ventilatory Effects of Isoflurane Sedation via the Sedaconda ACD-S versus ACD-L: A Substudy of a Randomized Trial.

Devices used to deliver inhaled sedation increase dead space ventilation. We therefore compared ventilatory effects among isoflurane sedation via the Sedaconda ACD-S (internal volume: 50 mL), isoflurane sedation via the Sedaconda ACD-L (100 mL), and propofol sedation with standard mechanical ventilation with heat and moisture exchangers (HME). This is a substudy of a randomized trial that compared inhaled isoflurane sedation via the ACD-S or ACD-L to intravenous propofol sedation in 301 intensive care patients. Data from the first 24 h after study inclusion were analyzed using linear mixed models. Primary outcome was minute ventilation. Secondary outcomes were tidal volume, respiratory rate, arterial carbon dioxide pressure, and isoflurane consumption. In total, 151 patients were randomized to propofol and 150 to isoflurane sedation; 64 patients received isoflurane via the ACD-S and 86 patients via the ACD-L. While use of the ACD-L was associated with higher minute ventilation (average difference (95% confidence interval): 1.3 (0.7, 1.8) L/min, p < 0.001), higher tidal volumes (44 (16, 72) mL, p = 0.002), higher respiratory rates (1.2 (0.1, 2.2) breaths/min, p = 0.025), and higher arterial carbon dioxide pressures (3.4 (1.2, 5.6) mmHg, p = 0.002), use of the ACD-S did not significantly affect ventilation compared to standard mechanical ventilation and sedation. Isoflurane consumption was slightly less with the ACD-L compared to the ACD-S (-0.7 (-1.3, 0.1) mL/h, p = 0.022). The Sedaconda ACD-S compared to the ACD-L is associated with reduced minute ventilation and does not significantly affect ventilation compared to a standard mechanical ventilation and sedation setting. The smaller ACD-S is therefore the device of choice to minimize impact on ventilation, especially in patients with a limited ability to compensate (e.g., COPD patients). Volatile anesthetic consumption is slightly higher with the ACD-S compared to the ACD-L.

Randomized controlled trial of ultra-protective vs. protective ventilation strategy in veno-arterial extracorporeal membrane oxygenation patients with refractory cardiogenic shock: a study protocol for the ultra-ECMO trial.

A protective or ultra-protective tidal volume strategy is widely applied to patients with acute respiratory distress syndrome (ARDS). The use of very low tidal volume has the potential to further redece ventilation-induced lung injury (VILI) comparde with a "normal" lung protective management. Plus, cardiogenic pulmonary edema (CPE) caused by hydrostatic mechanisms in patients with cardiogenic shock has similar respiratory mechanics to those found in patients with ARDS. And no consensus exists on mechanical ventilation parameter settings in patients with VA-ECMO. The study aimed to investigate the impact of an ultra-protective tidal volume strategy on the 28-day ventilator-free day (VFD) number in VA-ECMO-supported patients with refractory cardiogenic shock, including cardiac arrest. The Ultra-ECMO trial is a randomized controlled, open-label, single-center prospective superiority trial. At the onset of ECMO initiation, we will divide patients randomly into an intervention group and a control group in a 1:1 ratio. The control group will adopt protective ventilation settings [initial tidal volume: 6 ml/kg of predicted body weight (PBW)] for ventilation, and the intervention group will adopt ultra-protective ventilation settings (initial tidal volume: 4 ml/kg of PBW) for ventilation. The procedure is expected to last 72 h, after which the ventilator settings will be at the intensivists' discretion. The primary outcome is the VFD number at 28 days after inclusion. The secondary outcomes will include respiratory mechanics; analgesic/sedation dosage; lung ultrasound score; interleukin-6, interleukin-8, and monocyte chemotactic protein-1 levels in broncho-alveolar lavage fluid at the moment of enrollment (T0), 24, 48, and 72 h (T1, T2, and T3, respectively) after ECMO initiation; total time (in days) required for ECMO weaning; length of stay in the intensive care unit; total cost of hospitalization; amounts of resuscitative fluids; and in-hospital mortality. VA-ECMO-treated patients without ARDS possess abnormal lung function. CPE, thoracic compliance reduction, and poor pulmonary blood perfusion are frequently present, and these patients can more easily progress to ARDS. It seems that targeting the protective tidal volume can lower adverse outcome incidence rates, even in patients without ARDS. This trial seeks to answer the question of whether adopting an ultra-protective tidal volume strategy can lead to superior primary and secondary outcomes compared to adopting a protective tidal volume strategy in patients treated by VA-ECMO. The Ultra-ECMO trial will provide an innovative mechanical ventilation strategy for VA-ECMO-supported patients for improving treatment outcomes at biological and potentially clinical levels. ChiCTR2200067118.

Flexible bronchoscopy in pediatric intensive care unit

Flexible bronchoscopy (FB) is a very rewarding procedure in the evaluation and management of appropriately selected children with respiratory issues in pediatric intensive care unit (PICU). An understanding of the alterations in respiratory physiology (airway resistance, compliance, and air exchange) during FB is absolutely essential for the safety of the child. To reduce discomfort and other side effects of FB it is necessary to optimize the condition of the child including sedation, analgesia, paralysis, ventilator settings, and cardiovascular status. With advancements in technology and instrumentation many interventional procedures can be performed safely and effectively using access to the airway through the endotracheal tube, tracheostomy tube, or Laryngeal Mask Airway (LMA). Close monitoring during and after FB minimizes complications.

Risk Factors for Prolonged Intensive Care Unit Stay in Patients with Hypercapnic Respiratory Failure.

Hypercapnic respiratory failure (HRF) is one of the most frequent reasons for intensive care unit (ICU) admissions. In this study, we aimed to investigate the risk factors for prolonged ICU stay in HRF patients for longer than 7, 10, and 15 days. Impact of demographics, vitals at the admission, comorbid disease severity, respiratory parameters, admission diagnosis, noninvasive mechanical ventilation (NIV) application time and settings, arterial blood gas, and blood biochemistry results were analyzed in patients with HRF to investigate risk factors for longer ICU stay. A total of 210 patients who were admitted to ICU with HRF (PaCO2 values of 45 mmHg and higher) were included in this retrospective cohort study. The mean age of the patients was 69±12 years, and the mean ICU duration was 9±7 days. Forty-five percent of the patients stayed in the ICU for more than one week and %10 of them stayed for more than 15 days. Risk factors for a prolonged stay in ICU for more than 7 days were high SOFA score, acute renal failure (ARF) at admission, low PaO2/FiO2 on the 2nd day of admission, and high TSH level. Low FEV1 and FEV1/FVC ratio, ARF at admission, and low PaO2/FiO2 ratio on the 2nd day of admission were found to be risk factors for prolonged stay in ICU for longer than 10 days. Significant risk factors prolonging the ICU duration for more than 15 days were high SOFA score, low FEV1, low FEV1/FVC ratio (P = 0.008), and hypothyroidism (P = 0.037). FEV1% predicted less than 25.5% and FEV1/FVC% less than 46.5 % were significantly associated with ICU stay longer than 10 days. Earlier diagnosis and treatment of patients with hypothyroidism and severe airflow obstruction could shorten the length of ICU stay of hypercapnic patients.

Efficacy of an Automated Secretion Removal Technology at Different Inspiratory Pressures.

Endotracheal suctioning is resource demanding, causes patient discomfort, and is associated with adverse effects. A new artificial cough method has been developed for automated secretion removal by using rapid deflation and inflation of the endotracheal tube cuff during the inspiratory phase of mechanical ventilation. This method has been evaluated in a bench model and in animals but not in human subjects. The aim of this study was to investigate whether this method can remove the need for endotracheal suctioning in subjects and whether this is dependent on ventilator settings. This prospective, non-controlled study recruited 20 subjects on invasive mechanical ventilation. On the clinical need for endotracheal suctioning, the automatic cough procedure was applied 3 times over 30 s, with this repeated at higher ventilatory pressure and lower respiratory frequency if considered unsuccessful. Success was determined by removal of the clinical need for suctioning. Subject safety and comfort was measured by using the Critical-Care Pain Observation Tool before and after the procedure, and negative effects were recorded. To assess intra-subject variability, the procedure was performed on 3 different occasions for each subject. The procedure was successful in 18 of 20 subjects (90%), with mean subject success rates of 53% at low settings (peak inspiratory pressure 21.8 ± 3.8 cm H2O) and 83% at high settings (peak inspiratory pressure 25.6 ± 3.6 cm H2O). The Critical-Care Pain Observation Tool category remained unchanged in 30 procedures (77%), improved in 7 (18%), and deteriorated in 2 (5%). This study illustrated the potential for significant reduction in the clinical need for endotracheal suctioning after the use of an automated artificial cough procedure at both low and high peak inspiratory pressures, and that was well tolerated.

Implementation of Fuzzy Logic in Managing Common Anesthesia

Using fuzzy sets for reasoning is what we mean when we talk about fuzzy logic. Contradictory natures are prevalent phenomena in the medical field. Guidelines are used by anesthesiologists when taking care of patients. After gauging the patient’s vitals, he may make adjustments to the flow of medication and fluids, or even the ventilator settings. Knowledge about the real world is typically sketchy, inaccurate, and inconsistent. Due to the inherent representation of subjective human conceptions used in much medical decision making, fuzzy logic seems well-suited for use in anaesthesia. We have developed a fuzzy expert system using fuzzy methodology for the aim of fluid management during general anaesthesia. The desired intravenous fluid rate (IFR) is the defuzzified value that is output by the fuzzy expert system. Fuzzy inputs serve as antecedent parts of rules for a fuzzy expert system, and some examples of such inputs are mean arterial pressure (HUO), hourly urine output (HUO), and central venous pressure (CVP). It would only cost a little sum to have a human operator sometimes enter MAP, HUO, and CVP values into a personal computer for this purpose. The study’s overarching goal was to devise a method for approximating IFR by making use of a linguistic description of MAP and HUO. Fuzzy sets, including decreasing, constant, and growing MAP and HUO rates of change, would assist to illustrate the trend in a patient’s fluid state. To regulate fluid levels more precisely would be possible. Expert guidance in addition to the calculated use of fuzzy methods are essential for achievement of the desired outcome. Patients must be in generally good health before this mode may be used on them, and they must be undergoing minimally invasive surgery. Moderate to severe blood loss after surgery need more complex modalities involving more factors.

Getting It Right in Obstructive Lung Disease.

Chronic hypercapnic respiratory failure in obstructive lung diseases may benefit from nocturnal Home non-invasive ventilation (HNIV). It has been shown that in patients with persistence of hypercapnia after an acute episode of chronic obstructive pulmonary disease (COPD) exacerbation requiring mechanical ventilation, HNIV may improve the risk for new admission and survival. The ability to reach these aims depends on the correct timing of enrolling patients, as well as a correct definition of ventilatory needing and setting of the ventilator. This review tries to define a possible home treatment path of hypercapnic respiratory failure in COPD by analyzing the main studies published in recent years.

Utilization of mechanical power and associations with clinical outcomes in brain injured patients: a secondary analysis of the extubation strategies in neuro-intensive care unit patients and associations with outcome (ENIO) trial

BackgroundThere is insufficient evidence to guide ventilatory targets in acute brain injury (ABI). Recent studies have shown associations between mechanical power (MP) and mortality in critical care populations. We aimed to describe MP in ventilated patients with ABI, and evaluate associations between MP and clinical outcomes.MethodsIn this preplanned, secondary analysis of a prospective, multi-center, observational cohort study (ENIO, NCT03400904), we included adult patients with ABI (Glasgow Coma Scale ≤ 12 before intubation) who required mechanical ventilation (MV) ≥ 24 h. Using multivariable log binomial regressions, we separately assessed associations between MP on hospital day (HD)1, HD3, HD7 and clinical outcomes: hospital mortality, need for reintubation, tracheostomy placement, and development of acute respiratory distress syndrome (ARDS).ResultsWe included 1217 patients (mean age 51.2 years [SD 18.1], 66% male, mean body mass index [BMI] 26.3 [SD 5.18]) hospitalized at 62 intensive care units in 18 countries. Hospital mortality was 11% (n = 139), 44% (n = 536) were extubated by HD7 of which 20% (107/536) required reintubation, 28% (n = 340) underwent tracheostomy placement, and 9% (n = 114) developed ARDS. The median MP on HD1, HD3, and HD7 was 11.9 J/min [IQR 9.2–15.1], 13 J/min [IQR 10–17], and 14 J/min [IQR 11–20], respectively. MP was overall higher in patients with ARDS, especially those with higher ARDS severity. After controlling for same-day pressure of arterial oxygen/fraction of inspired oxygen (P/F ratio), BMI, and neurological severity, MP at HD1, HD3, and HD7 was independently associated with hospital mortality, reintubation and tracheostomy placement. The adjusted relative risk (aRR) was greater at higher MP, and strongest for: mortality on HD1 (compared to the HD1 median MP 11.9 J/min, aRR at 17 J/min was 1.22, 95% CI 1.14–1.30) and HD3 (1.38, 95% CI 1.23–1.53), reintubation on HD1 (1.64; 95% CI 1.57–1.72), and tracheostomy on HD7 (1.53; 95%CI 1.18–1.99). MP was associated with the development of moderate-severe ARDS on HD1 (2.07; 95% CI 1.56–2.78) and HD3 (1.76; 95% CI 1.41–2.22).ConclusionsExposure to high MP during the first week of MV is associated with poor clinical outcomes in ABI, independent of P/F ratio and neurological severity. Potential benefits of optimizing ventilator settings to limit MP warrant further investigation.

External airway splint placement for severe pediatric tracheobronchomalacia

ObjectiveTo present external airway splinting with bioabsorbable airway supportive devices (ASD) for severe, life-threatening cases of pediatric tracheomalacia (TM) or tracheobronchomalacia (TBM). MethodsA retrospective cohort was performed for 5 pediatric patients with severe TM or TBM who underwent ASD placement. Devices were designed and 3D-printed from a bioabsorbable material, polycaprolactone (PCL). Pre-operative planning included 3-dimensional airway modeling of tracheal collapse and tracheal suture placement using nonlinear finite element (FE) methods. Pre-operative modeling revealed that triads along the ASD open edges and center were the most effective suture locations for optimizing airway patency. Pediatric cardiothoracic surgery and otolaryngology applied the ASDs by suspending the trachea to the ASD with synchronous bronchoscopy. Respiratory needs were trended for all cases. Data from pediatric patients with tracheostomy and diagnosis of TM or TBM, but without ASD, were included for discussion. ResultsFive patients (2 Females, 3 Males, ages 2–9 months at time of ASD) were included. Three patients were unable to wean from respiratory support after vascular ring division; all three weaned to room air post-ASD. Two patients received tracheostomies prior to ASD placement, but continued to experience apparent life-threatening events (ALTE) and required ventilation with supraphysiologic ventilator settings. One patient weaned respiratory support successfully after ASD placement. The last patient died post-ASD due to significant respiratory co-morbidity. ConclusionASD can significantly benefit patients with severe, unrelenting tracheomalacia or tracheobronchomalacia. Proper multidisciplinary case deliberation and selection are key to success with ASD. Pre-operative airway modeling allows proper suture placement to optimally address the underlying airway collapse.

Stratifying Severity of Acute Respiratory Failure Severity in Cyanotic Congenital Heart Disease.

Hypoxemia is used to stratify severity in acute respiratory failure (ARF) but is less useful in cyanotic congenital heart disease (CCHD) due to an inability to differentiate hypoxemia from lung injury versus cardiac shunting. Therefore, we aimed to determine whether variables related to respiratory mechanics were associated with outcomes to assist in stratifying ARF severity in pediatric CCHD. We performed a retrospective cohort study from a single cardiac intensive care unit enrolling children with CCHD with ARF requiring mechanical ventilation between 2011 and 2019. Time-averaged ventilator settings and oxygenation data in the first 24h of ARF were screened for association with the primary outcome of 28-day mortality. Of 344 eligible patients, peak inspiratory pressure (PIP) and driving pressure (ΔP) were selected as candidate variables to stratify ARF severity. PIP (OR 1.10, 95% CI 1.02-1.19) and ΔP (1.11, 95% CI 1.01-1.24) were associated with higher mortality and fewer ventilator-free days (VFDs) at 28days after adjusting for age, severity of cardiac history, and FiO2. A three-level (mild, moderate, severe) severity stratification was established for both PIP (≤ 20, 21-29, ≥ 30) andΔP (≤ 16, 17-24, ≥ 25), showing increasing mortality (both P < 0.01), decreasing VFDs and increasing ventilator days in survivors (all P < 0.05) across increasing pressures. Overall, we found that higher PIP and ΔP were associated with mortality and duration of ventilation across a three-level severity stratification system in pediatric CCHD with ARF, providing a practical method to prognosticate in subjects with multifactorial etiologies for hypoxemia.

Alveolar target ventilation and dead space in children under anaesthesia: The proventiped cohort study.

Ventilator settings in children under anaesthesia remain difficult because of the changes in the physiology and the high dead space. To determine the alveolar minute-volume to sustain normocapnia in children under mechanical ventilation. A prospective observational study. This study was performed between May and October 2019 in a tertiary care children's hospital. Children between 2 months and 12 years, weighing between 5 and 40 kg, admitted for general anaesthesia. Volumetric capnography was used to estimate the alveolar and dead space volume (Vd). Total and alveolar minute ventilation in (ml kg-1 min-1) over 100 breaths. Sixty patients were included comprising 20 per group: 5 to 10 kg (group 1), 10 to 20 kg (group 2), 20 to 40 kg (group 3). Seven patients were excluded for aberrant capnographic curves. After normalisation to weight, the median [IQR] tidal volume per kilogram was similar between the three groups: 6.5 ml kg-1 [6.0 to 7.5 ml kg-1], 6.4 ml kg-1 [5.7 to 7.3 ml kg-1], 6.4 ml kg-1 [5.3 to 6.8 ml kg-1]; P = 0.3. Total Vd (in ml kg-1) was negatively correlated to weight (r = -0.62, 95% confidence interval -0.41 to -0.76, P < 0.001). The total normalised minute ventilation (ml kg-1 min-1) to obtain normocapnia was higher in group 1 than in group 2 and in group 3; 203 ml kg-1 min-1 [175 to 219 ml kg-1 min-1], 150 ml kg-1 min-1 [139 to 181 ml kg-1 min-1] and 128 ml kg-1 min-1 [107 to 157 ml kg-1 min-1]; P < 0.001 (mean ± SD), but (mean ± SD) alveolar minute ventilation was similar between the three groups; 68 ± 21 ml kg-1 min-1. Total dead space volume (including apparatus dead space) represents a major component of tidal volume in children less than 30 kg, when using large heat and moisture exchanger filters. The total minute ventilation necessary to achieve normocapnia decreased with increasing weight, while the alveolar minute ventilation remained constant. ClinicalTrials.gov, identifier: NCT03901599.

Clinical risk factors for increased respiratory drive in intubated hypoxemic patients

BackgroundThere is very limited evidence identifying factors that increase respiratory drive in hypoxemic intubated patients. Most physiological determinants of respiratory drive cannot be directly assessed at the bedside (e.g., neural inputs from chemo- or mechano-receptors), but clinical risk factors commonly measured in intubated patients could be correlated with increased drive. We aimed to identify clinical risk factors independently associated with increased respiratory drive in intubated hypoxemic patients.MethodsWe analyzed the physiological dataset from a multicenter trial on intubated hypoxemic patients on pressure support (PS). Patients with simultaneous assessment of the inspiratory drop in airway pressure at 0.1-s during an occlusion (P0.1) and risk factors for increased respiratory drive on day 1 were included. We evaluated the independent correlation of the following clinical risk factors for increased drive with P0.1: severity of lung injury (unilateral vs. bilateral pulmonary infiltrates, PaO2/FiO2, ventilatory ratio); arterial blood gases (PaO2, PaCO2 and pHa); sedation (RASS score and drug type); SOFA score; arterial lactate; ventilation settings (PEEP, level of PS, addition of sigh breaths).ResultsTwo-hundred seventeen patients were included. Clinical risk factors independently correlated with higher P0.1 were bilateral infiltrates (increase ratio [IR] 1.233, 95%CI 1.047–1.451, p = 0.012); lower PaO2/FiO2 (IR 0.998, 95%CI 0.997–0.999, p = 0.004); higher ventilatory ratio (IR 1.538, 95%CI 1.267–1.867, p < 0.001); lower pHa (IR 0.104, 95%CI 0.024–0.464, p = 0.003). Higher PEEP was correlated with lower P0.1 (IR 0.951, 95%CI 0.921–0.982, p = 0.002), while sedation depth and drugs were not associated with P0.1.ConclusionsIndependent clinical risk factors for higher respiratory drive in intubated hypoxemic patients include the extent of lung edema and of ventilation-perfusion mismatch, lower pHa, and lower PEEP, while sedation strategy does not affect drive. These data underline the multifactorial nature of increased respiratory drive.

Biomarkers as predictors of mortality in critically ill obese patients with COVID-19 at high altitude

BackgroundObesity is a common chronic comorbidity of patients with COVID-19, that has been associated with disease severity and mortality. COVID-19 at high altitude seems to be associated with increased rate of ICU discharge and hospital survival than at sea-level, despite higher immune levels and inflammation. The primary aim of this study was to investigate the survival rate of critically ill obese patients with COVID-19 at altitude in comparison with overweight and normal patients. Secondary aims were to assess the predictive factors for mortality, characteristics of mechanical ventilation setting, extubation rates, and analytical parameters.MethodsThis is a retrospective cohort study in critically ill patients with COVID-19 admitted to a hospital in Quito-Ecuador (2,850 m) from Apr 1, 2020, to Nov 1, 2021. Patients were cathegorized as normal weight, overweight, and obese, according to body mass index [BMI]).ResultsIn the final analysis 340 patients were included, of whom 154 (45%) were obese, of these 35 (22.7%) were hypertensive and 25 (16.2%) were diabetic. Mortality in obese patients (31%) was lower than in the normal weight (48%) and overweight (40%) groups, but not statistically significant (p = 0.076). At multivariable analysis, in the overall population, older age (> 50 years) was independent risk factor for mortality (B = 0.93, Wald = 14.94, OR = 2.54 95%CI = 1.58–4.07, p < 0.001). Ferritin and the neutrophil/lymphocyte ratio were independent predictors of mortality in obese patients. Overweight and obese patients required more positive and-expiratory pressure compared to normal-weight patients. In obese patients, plateau pressure and mechanical power were significantly higher, whereas extubation failure was lower as compared to overweight and normal weight.ConclusionsThis preliminary study suggests that BMI was not associated with mortality in critically ill patients at high altitude. Age was associated with an increase in mortality independent of the BMI. Biomarkers such as ferritin and neutrophils/lymphocytes ratio were independent predictors of mortality in obese patients with COVID-19 at high altitude.

The Effects of Automatic Inspiratory Rise Time and Flow Termination on Operation of Closed-Loop Ventilation.

Adaptive ventilation mode (AVM) is a automated mode of mechanical ventilation. AVM is comprable to adaptive support ventilation (ASV). Both recommend a tidal volume (VT) and breathing frequency (f) combination based on lung mechanics, but AVM also automatically adjusts rise time and flow termination of pressure support breaths. How these added features of AVM affect VT and f recommendations compared to ASV is not clear. The present study compared these 2 modes in a test lung with obstructive and restrictive mechanics. The experiment was performed in a simulated lung model in which the compliance (C) and resistance (R) could be altered independently. The ventilatory parameters at different minute volumes (MinVol%) in AVM or ASV mode were recorded. When MinVol% was set at 100%, AVM provided a similar VT and f combination compared to ASV with decreasing compliance or increasing resistance. However, when MinVol% was increased to 250% simulating hyperventilation, for the severely obstructive lung (C60, R70) model, AVM provided a significantly higher f (26 ± 0.6 breaths/min vs 7.00 ± 0 breaths/min in ASV) and lower VT (240 ± 80 mL vs 491 ± 131 mL in ASV). The addition of automatic control of rise time and flow termination functions did not affect recommended ventilator settings in AVM in the noncompliant or obstructive lung when minute ventilation (V̇E) was low. At higher V̇E, AVM compared to ASV recommended a ventilatory strategy with lower VT and higher f. These results need to be validated in patients.

Positive End-Expiratory Pressure Levels in Adult Patients With Acute Lung Injury and Acute Respiratory Distress Syndrome

Positive End-Expiratory Pressure Levels in Adult Patients With Acute Lung Injury and Acute Respiratory Distress Syndrome