Intermittent Mandatory Ventilation Research Articles

Increased Nuchal Translucency Without Aneuploidy in a Fetus: Abnormal Postnatal Radiograph and a Novel Mutation.

Increased Nuchal Translucency Without Aneuploidy in a Fetus: Abnormal Postnatal Radiograph and a Novel Mutation.

The effect of proportional assist ventilation on the electrical activity of the human diaphragm during exercise.

What is the central question of this study? What is the effect of lowering the normally occurring work of breathing on the electrical activity and pressure generated by the diaphragm during submaximal exercise in healthy humans? What is the main finding and its importance? Ventilatory assist during exercise elicits a proportional lowering of both the work performed by the diaphragm and diaphragm electrical activity. These findings have implications for exercise training studies using proportional assist ventilation to reduce diaphragm work in patients with cardiopulmonary disease. We hypothesized that when a proportional assist ventilator (PAV) is applied in order to reduce the pressure generated by the diaphragm, there would be a corresponding reduction in electrical activity of the diaphragm. Healthy participants (five male and four female) completed an incremental cycle exercise test to exhaustion in order to calculate workloads for subsequent trials. On the experimental day, participants performed submaximal cycling, and three levels of assisted ventilation were applied (low, medium and high). Ventilatory parameters, pulmonary pressures and EMG of the diaphragm (EMGdi ) were obtained. To compare the PAV conditions with spontaneous breathing intervals, ANOVA procedures were used, and significant effects were evaluated with a Tukey-Kramer test. Significance was set at P<0.05. The work of breathing was not different between the lowest level of unloading and spontaneous breathing (P=0.151) but was significantly lower during medium (25%, P=0.02) and high (36%, P<0.001) levels of PAV. The pressure-time product of the diaphragm (PTPdi ) was lower across PAV unloading conditions (P<0.05). The EMGdi was significantly lower in medium and high PAV conditions (P=0.035 and P<0.001, respectively). The mean reductions of EMGdi with PAV unloading were 14, 22 and 39%, respectively. The change in EMGdi for a given lowering of PTPdi with the PAV was significantly correlated (r=0.61, P=0.01). Ventilatory assist during exercise elicits a reduction in the electrical activity of the diaphragm, and there is a proportional lowering of the work of breathing. Our findings have implications for exercise training studies using assisted ventilation to reduce diaphragm work in patients with cardiopulmonary disease.

Ventilation Strategies During Extracorporeal Membrane Oxygenation for Neonatal Respiratory Failure: Current Approaches Among Level IV Neonatal ICUs.

Cross-sectional electronic survey. Email-based Research Electronic Data Capture survey. Neonates undergoing ECMO for respiratory failure at level IV NICUs. A 40-question survey was sent to site sponsors of regional referral neonatal ECMO centers participating in the Children's Hospitals Neonatal Consortium. Reminder emails were sent at 2- and 4-week intervals. Twenty ECMO centers responded to the survey. Most primarily use venoarterial ECMO (65%); this percentage is higher (90%) for congenital diaphragmatic hernia. Sixty-five percent reported following protocol-based guidelines, with neonatologists primarily responsible for ventilator management (80%). The primary mode of ventilation was pressure control (90%), with synchronized intermittent mechanical ventilation (SIMV) comprising 80%. Common settings included peak inspiratory pressure (PIP) of 16-20 cm H2O (55%), positive end-expiratory pressure (PEEP) of 9-10 cm H2O (40%), I-time 0.5 seconds (55%), rate of 10-15 (60%), and Fio2 22-30% (65%). A minority of sites use high-frequency ventilation (HFV) as the primary mode (5%). During ECMO, 55% of sites target some degree of lung aeration to avoid complete atelectasis. Fifty-five percent discontinue inhaled nitric oxide (iNO) during ECMO, while 60% use iNO when trialing off ECMO. Nonventilator practices to facilitate decannulation include bronchoscopy (50%), exogenous surfactant (25%), and noninhaled pulmonary vasodilators (50%). Common ventilator thresholds for decannulation include PEEP of 6-7 (45%), PIP of 21-25 (55%), and tidal volume 5-5.9 mL/kg (50%). The majority of level IV NICUs follow internal protocols for ventilator management during neonatal respiratory ECMO, and neonatologists primarily direct management in the NICU. While most centers use pressure-controlled SIMV, there is considerable variability in the range of settings used, with few centers using HFV primarily. Future studies should focus on identifying respiratory management practices that improve outcomes for neonatal ECMO patients.

Does the intubation timeline affect the in-hospital mortality of COVID-19 patients? A retrospective cohort study.

BackgroundEffective strategies for managing coronavirus disease 19 (COVID-19) patients suffering from acute respiratory distress are constantly evolving. The timeline and threshold for transitioning from non-invasive ventilation to intermittent mandatory ventilation in critical cases who develop COVID-19-related respiratory distress are undetermined. The present research intends to investigate if emergency room intubations in COVID-19 patients affect mortality.MethodsBetween January 1, 2021 and June 30, 2021, we retrospectively reviewed chart analysis on all patients with confirmed positive COVID-19 screening and who underwent endotracheal intubation. Depending on when the intubation was performed; early in the emergency room or delayed outside the emergency room, patients were separated into two cohorts. In addition to comorbid clinical manifestations, the quick sequential organ failure assessment (qSOFA) score, and in-hospital mortality were all recorded as demographic and clinical information.ResultsFifty-eight of the 224 corona-positive patients who underwent intubation had their intubations performed in the emergency room. Age, sex, alcohol use, and smoking status did not significantly differ between the two categories at the baseline. The mean qSOFA score was higher in the early intubation cohort (3.5; p < 0.000) along with more underlying comorbidities (3.0; p < 0.000). When compared to the late intubation cohort (45.78%), patients treated with early intubation had a significantly greater death rate (67.24%).ConclusionIn summary, we discovered that patients who underwent intubation in the emergency units exhibited a high quick SOFA score as well as maximum co-morbid conditions than patients intubated somewhere else in the hospital. The findings of our investigation imply that intubating patients too early might be risky.

The Evolution of Intermittent Mandatory Ventilation.

Intermittent mandatory ventilation (IMV) is one kind of breath sequence used to classify a mode of ventilation. IMV is defined as the ability for spontaneous breaths (patient triggered and patient cycled) to exist between mandatory breaths (machine triggered or machine cycled). Over the course of more than a century, IMV has evolved into 4 distinct varieties, each with its own advantages and disadvantages in serving the goals of mechanical ventilation (ie, safety, comfort, and liberation). The purpose of this paper is to describe the evolution of IMV, review relevant supporting evidence, and discuss the rationales for each of the 4 varieties. Also included is a brief overview of the background information required for a proper perspective of the purpose and design of the innovations. Understanding these different forms of IMV is essential to recognizing the similarities and differences among many dozens of different modes of ventilation. This recognition is important for clinical application, education of caregivers, and research in mechanical ventilation.

Airway Pressure Release Ventilation for Acute Respiratory Distress Syndrome: An Update

&#x0D; Evidence suggested there was no significant difference in mortality between patients with or at risk of acute respiratory distress syndrome treated with airway pressure release ventilation versus other mechanical ventilation strategies.&#x0D; The evidence of the clinical effectiveness of airway pressure release ventilation in patients with or at risk of acute respiratory distress syndrome is uncertain for several outcomes (length of intensive care unit stay, oxygenation, ventilator-free days, mean arterial pressure). Evidence from some studies suggested there was a significant benefit favouring airway pressure release ventilation versus other mechanical ventilation strategies for these outcomes, other studies suggested there was a significant benefit favouring other mechanical ventilation strategies, and some studies found no significant differences between treatment groups.&#x0D; Results from 1 study suggested there were no significant differences in incidence of acute respiratory distress syndrome between patients treated with airway pressure release ventilation versus pressure-controlled synchronized intermittent mandatory ventilation and pressure support.&#x0D; Evidence suggested there was no significant difference in tracheostomy between patients with or at risk of acute respiratory distress syndrome treated with airway pressure release ventilation versus control. In 1 study significantly more patients treated with airway pressure release ventilation experienced severe hypercapnia than those treated with low tidal volume ventilation.&#x0D; One guideline suggests considering the use of airway pressure release ventilation in patients without severe acute respiratory distress syndrome.&#x0D;

Comparison of the Effectiveness of Shock Index, Modified Shock Index, and Age Shock Index in COPD Exacerbations.

To evaluate the effectiveness and practicality of shock index (SI), modified shock index (MSI), and age-shock index (Age-SI) in predicting the prognosis, mortality, ICU and service admission, and the need for intermittent mandatory ventilation (IMV) and nasal intermittent mandatory ventilation) (NIMV in the ED patients with chronic obstructive pulmonary disease (COPD) exacerbation. Retrospective study. Balikesir University Faculty of Medicine, Emergency Service, Balıkesir, Turkey, from January 2019 to May 2020. Adult patients, who were admitted to the Emergency Department with diagnosis of COPD exacerbation, were included. Patients with missing data were excluded. SI, MSI, and age-SI values were calculated by using the vital signs. ROC curve analysis was used to evaluate the diagnostic performances of SI, MSI, and age-SI. The study consisted of 201 patients, 152 (75.6%) were males. Six (3%) patients died, 26 (12%) were admitted to ICU, 112 (55.7%) were admitted to the service, 11 (5.5%) needed IMV, and 48 (23.9%) needed NIMV in ED. SI was superior to the MSI and age-SI in predicting mortality, and AUC values of 0.802, 0.727, and 0.704, respectively. SI was also superior to the MSI and age-SI in predicting hospital admissions (SI AUC=0.591, p=0.029; MSI AUC=0.572, p=0.059; and age-SI AUC=0.580, p=0.089). Respectively none of the three indices was independently sufficient in predicting IMV, NIMV, and the need for ICU. SI is a valuable parameter in discriminating the COPD exacerbation. It is superior to the MSI and age-SI in predicting mortality and hospital admissions. It will be useful to evaluate SI for the severity classification, follow-up, and management of the patients with COPD. Age shock index, Chronic obstructive pulmonary disease, Modified shock index, mortality, Shock index.

Rescue high-frequency oscillatory ventilation combined with intermittent mandatory ventilation for infants with acute respiratory distress syndrome after congenital heart surgery.

This study aimed to evaluate the efficacy and safety of high-frequency oscillation ventilation combined with intermittent mandatory ventilation in infants with acute respiratory distress syndrome after congenital heart surgery. We retrospectively analysed the clinical data of 32 infants who were ventilated due to acute respiratory distress syndrome after congenital heart surgery between January, 2020 and January, 2022. We adopted high-frequency oscillation ventilation combined with intermittent mandatory ventilation as the rescue ventilation mode for infants who were failing conventional mechanical ventilation. After rescue high-frequency oscillation ventilation combined with intermittent mandatory ventilation, the dynamic compliance (Cdyn), PaO2 and PaO2/FiO2 ratio of the infants improved compared with conventional mechanical ventilation (p < 0.05). Moreover, high-frequency oscillation ventilation combined with intermittent mandatory ventilation resulted in a significant decrease in arterial-alveolar oxygen difference (AaDO2), FiO2, and oxygenation index (p < 0.05). No significant effect on haemodynamic parameters was observed. Moreover, no serious complications occurred in the two groups. Rescue high-frequency oscillation ventilation combined with intermittent mandatory ventilation significantly improved oxygenation in infants who failed conventional mechanical ventilation for acute respiratory distress syndrome after congenital heart surgery. Thus, this strategy is considered safe and feasible. However, further studies must be conducted to confirm the efficacy and safety of high-frequency oscillation ventilation combined with intermittent mandatory ventilation as a rescue perioperative respiratory support strategy for CHD.

Pathophysiologically Based Ventilatory Management of Severe Bronchopulmonary Dysplasia.

Both “new” and “old” bronchopulmonary dysplasia features overlap in preterm infants with severe bronchopulmonary dysplasia. The optimal ventilation strategy for infants with severe bronchopulmonary dysplasia has not been clarified yet. Principally, the lung is a multi-compartmental heterogeneous tissue with regionally varying compliance and resistance.Generally, 2 critical strategical errors are common while ventilating infants with established bronchopulmonary dysplasia: (i) ventilatory management as if they are still in the acute phase of respiratory distress syndrome and (ii) early extubation attempts with the aim of reducing ventilator-induced lung injury. Considering the heterogeneous character of bronchopulmonary dysplasia, although there is no unique formulation for optimal ventilation, the most physiologically appropriate ventilation mode may be the combined mode of volume-guaranteed synchronized intermittent mechanical ventilation and pressure support ventilation. With the volume-guaranteed synchronized intermittent mechanical ventilation mode, slow compartments of the lung with high resistance and low compliance can be adequately ventilated, while fast compartments having relatively normal resistance and compliance can be ventilated well with the pressure support ventilation mode. The following settings are advisable: frequency = 12-20 breaths per minute, tidal volume = 10-15 mL/min, positive end expiratory pressure = 7-12 cmH2O, and inspiratory to expiratory time ratio = 1 : 5. Higher oxygen saturations such as 92%-95% should be targeted to avoid subsequent pulmonary hypertension.In conclusion, there is no evidence-based ventilation recommendation for infants with severe bronchopulmonary dysplasia. However, given the changing pattern of the disease and the underlying pathophysiology, these infants should not be ventilated as if they were in the acute phase of respiratory distress syndrome.

Fetal Doppler Evaluation to Predict NEC Development.

Antenatal factors play a role in NEC pathogenesis. This study aimed to investigate the predictive value of fetal ductus venosus doppler (DV) for NEC in fetal growth restriction fetuses (FGRF) and to assess the predictive accuracy of IG21 and Fenton curves in NEC development. Data from FGRF, postnatal findings, and Doppler characteristics were collected between 2010 and 2020 at a single center. Patients were then divided into two groups (i.e., with and without NEC). Bivariate and multivariate analyses were performed. We identified 24 cases and 30 controls. Absent or reversed end-diastolic flow (AREDF) and increased resistance in the DV were more impaired in cases (p < 0.05). Although the median birthweight was not different, the Fenton z-score was lower in NEC (p < 0.05). Fetal cardiopulmonary resuscitation, synchronized intermittent mandatory ventilation, neonatal respiratory distress, persistent patent ductus arteriosus (PDA), and inotropic support were more frequent in the NEC group. Furthermore, NEC patients had lower white blood cells (WBC) (p < 0.05). The predictive model for NEC (model 4), including Fenton z-score, WBC, PDA, and DV had an AUC of 84%. Fetal Doppler findings proved effective in predicting NEC in FGR. The Fenton z-score was the most predictive factor considering the fetal growth assessment showing high sensitivity.

The PROMIZING trial enrollment algorithm for early identification of patients ready for unassisted breathing

BackgroundLiberating patients from mechanical ventilation (MV) requires a systematic approach. In the context of a clinical trial, we developed a simple algorithm to identify patients who tolerate assisted ventilation but still require ongoing MV to be randomized. We report on the use of this algorithm to screen potential trial participants for enrollment and subsequent randomization in the Proportional Assist Ventilation for Minimizing the Duration of MV (PROMIZING) study.MethodsThe algorithm included five steps: enrollment criteria, pressure support ventilation (PSV) tolerance trial, weaning criteria, continuous positive airway pressure (CPAP) tolerance trial (0 cmH2O during 2 min) and spontaneous breathing trial (SBT): on fraction of inspired oxygen (FiO2) 40% for 30–120 min. Patients who failed the weaning criteria, CPAP Zero trial, or SBT were randomized. We describe the characteristics of patients who were initially enrolled, but passed all steps in the algorithm and consequently were not randomized.ResultsAmong the 374 enrolled patients, 93 (25%) patients passed all five steps. At time of enrollment, most patients were on PSV (87%) with a mean (± standard deviation) FiO2 of 34 (± 6) %, PSV of 8.7 (± 2.9) cmH2O, and positive end-expiratory pressure of 6.1 (± 1.6) cmH2O. Minute ventilation was 9.0 (± 3.1) L/min with a respiratory rate of 17.4 (± 4.4) breaths/min. Patients were liberated from MV with a median [interquartile range] delay between initial screening and extubation of 5 [1–49] hours. Only 7 (8%) patients required reintubation.ConclusionThe trial algorithm permitted identification of 93 (25%) patients who were ready to extubate, while their clinicians predicted a duration of ventilation higher than 24 h.

TECHNICAL ISSUE &amp; SERVICE SUPPORT OF 7000 ANESTHESIA VENTILATOR MULTI-VOLTAGE ELECTRONIC

Anaesthesia ventilators are an integral part of all modern anaesthesia workstations. Automatic ventilators in the operating rooms, which were very simple with few modes of ventilation when introduced, have become very sophisticated with many advanced ventilation modes. Several systems of classication of anaesthesia ventilators exist based upon various parameters. Modern anaesthesia ventilators have either a double circuit, bellow design or a single circuit piston conguration. In the bellows ventilators, ascending bellows design is safer than descending bellows. Piston ventilators have the advantage of delivering accurate tidal volume. They work with electricity as their driving force and do not require a driving gas. To enable improved patient safety, several modications were done in circle system with the different types of anaesthesia ventilators. Fresh gas decoupling is a modication done in piston ventilators and in descending bellows ventilator to reduce th incidence of ventilator induced volutrauma. In addition to the conventional volume control mode, modern anaesthesia ventilators also provide newer modes of ventilation such as synchronised intermittent mandatory ventilation, pressure-control ventilation and pressure-support ventilation (PSV). PSV mode is particularly useful for patients maintained on spontaneous respiration with laryngeal mask airway. Along with the innumerable benets provided by these machines, there are various inherent hazards associated with the use of the ventilators in the operating room.

Timing of tracheostomy &amp; its outcome in intensive care unit

Background: Tracheostomy is a commonly performed procedure to facilitate prolonged ventilator-based respiratory support in patients with respiratory failure. The side effects of tracheostomy includes tracheal stenosis, increased bacterial colonization and haemorrhage. The present study was conducted to assess timing of Tracheostomy &amp; its outcome in Intensive care unit. Material &amp; Methods: A retrospective study was done to assess timing of tracheostomy -early vs late, its outcome, as a determinant of weaning success in intensive care patients. The weaning process was begun with synchronized intermittent mandatory ventilation with pressure support. Medical records were analyzed for age, sex, underlying disease and cause of intubation, Acute Physiology and Chronic Health Evaluation (APACHE) II score17, duration of mechanical ventilation, complications of tracheostomy, pneumonia after tracheostomy, length of ICU stay, and mortality in the ICU and hospital. The analysis of the data was performed using the Statistical Package for the Social Sciences (SPSS, IBM Corp., Armonk, NY, US) software, version 22. P &lt; 0.05 will be considered statistically significant. Results: In the present study a total population of 100 patient with tracheostomy were included. Successful weaning occurs in 40% patients and 60% patients fail to wean.

Comparison of Airway Pressure Release Ventilation to High-Frequency Oscillatory Ventilation in Neonates with Refractory Respiratory Failure.

Background Airway pressure release ventilation (APRV) is a relatively new mode of ventilation in neonates. We hypothesize that APRV is an effective rescue mode in infants failing conventional ventilation and it is comparable in survival rates to rescue with high-frequency oscillatory ventilation (HFOV). Methods This is a 6-year retrospective cohort study of infants that failed synchronized intermittent mandatory ventilation (SIMV) and were rescued with either APRV or HFOV. For comparison, we divided infants into two groups (28-37 and >37 weeks) based on their corrected gestational age (CGA) at failure of SIMV. Results Ninety infants were included in the study. Infants rescued with APRV (n = 46) had similar survival rates to those rescued with HFOV (n = 44)—28-37 weeks CGA (APRV 78% vs. HFOV 84%, p = 0.68) and >37 weeks CGA (APRV 76% vs. HFOV 72%, p = 0.74). Use of APRV was not associated with an increase in pneumothorax (APRV 0% and HFOV 10%, p = 0.31, in 28-37 weeks CGA, and APRV 0% and HFOV 4%, p = 0.22, in >37 weeks CGA). Conclusion APRV can be effectively used to rescue infants with refractory respiratory failure on SIMV. When compared to HFOV, rescue with APRV is not associated with an increase in mortality or pneumothorax.

Performance Characteristics of a Novel 3D-Printed Bubble Intermittent Mandatory Ventilator (B-IMV) for Adult Pulmonary Support.

The COVID-19 pandemic has brought attention to the need for developing effective respiratory support that can be rapidly implemented during critical surge capacity scenarios in healthcare settings. Lung support with bubble continuous positive airway pressure (B-CPAP) is a well-established therapeutic approach for supporting neonatal patients. However, the effectiveness of B-CPAP in larger pediatric and adult patients has not been addressed. Using similar principles of B-CPAP pressure generation, application of intermittent positive pressure inflations above CPAP could support gas exchange and high work of breathing levels in larger patients experiencing more severe forms of respiratory failure. This report describes the design and performance characteristics of the BubbleVent, a novel 3D-printed valve system that combined with commonly found tubes, hoses, and connectors can provide intermittent mandatory ventilation (IMV) suitable for adult mechanical ventilation without direct electrification. Testing of the BubbleVent was performed on a passive adult test lung model and compared with a critical care ventilator commonly used in tertiary care centers. The BubbleVent was shown to deliver stable PIP and PEEP levels, as well as timing control of breath delivery that was comparable with a critical care ventilator.

Comparison of advanced closed-loop ventilation modes with pressure support ventilation for weaning from mechanical ventilation in adults: A systematic review and meta-analysis.

To compare neurally adjusted ventilatory assist (NAVA), proportional assist ventilation (PAV), adaptive support ventilation (ASV) and Smartcare pressure support (Smartcare/PS) with standard pressure support ventilation (PSV) regarding their effectiveness for weaning critically ill adults from invasive mechanical ventilation (IMV). Electronic databases were searched to identify parallel-group randomized controlled trials (RCTs) comparing NAVA, PAV, ASV, or Smartcare/PS with PSV, in adult patients under IMV through July 28, 2021. Primary outcome was weaning success. Secondary outcomes included weaning time, total MV duration, reintubation or use of non-invasive MV (NIMV) within 48h after extubation, in-hospital and intensive care unit (ICU) mortality, in-hospital and ICU length of stay (LOS) (PROSPERO registration No:CRD42021270299). Twenty RCTs were finally included. Compared to PSV, NAVA was associated with significantly lower risk for in-hospital and ICU death and lower requirements for post-extubation NIMV. Moreover, PAV showed significant advantage over PSV in terms of weaning rates, MV duration and ICU LOS. No significant differences were found between ASV or Smart care/PS and PSV. Moderate certainty evidence suggest that PAV increases weaning success rates, shortens MV duration and ICU LOS compared to PSV. It is also noteworthy that NAVA seems to improve in-hospital and ICU survival.

Newborn with Microcephaly.

Newborn with Microcephaly.

Utility of non-invasive synchronized intermittent mandatory ventilation in acute cardiogenic pulmonary edema

BackgroundsAcute cardiogenic pulmonary edema (ACPE), one of the outcomes of acute heart failure (AHF), is a common reason in a critical condition with respiratory distress. Non-invasive synchronized intermittent mandatory ventilation(nSIMV) mode, which includes inspiratory pressure in addition to positive end expiratory pressure with/without pressure support provided in the non-invasive continuous positive airway pressure plus/pressure support(nCPAP/PS) mode can be effective in hypercarbia and the associated changes in consciousness. This study aimed to demonstrate the efficacy of nSIMV in ACPE. MethodsPatients who presented with clinical acute respiratory failure and were admitted to the critical care unit of the emergency department with the diagnosis of ACPE were included. Patients were placed on non-invasive mechanical ventilators with an oronasal mask under the nCPAP/PS and nSIMV modes. Pulse and respiratory rate, systolic and diastolic blood pressure and Glasgow Coma Scores(GCS), HACOR(heart rate, acidosis, consciousness, oxygenation and respiratory rate) scores, pH, PaCO2, PaO2/FiO2 and lactate at the time of admission and at 30 and 60 min were evaluated. ResultsTwenty-two patients were recruited, nCPAP/PS mode was 10 and nSIMV mode was 12. Although there was no statistically significant difference between the two groups in terms of the change in the relevant parameters from admission to 60 min, the decreases in PaCO2 and lactate levels (31.4% vs. 21.2%, p = 0.383; 68.8% vs. 47.1%, p = 0.224; respectively) and the increase in PaO2 and PaO2/FiO2 values (34% vs. 14.2%, p = 0.710 and 132.1% vs. 52.7%, p = 0.073; respectively) were higher in the nSIMV group. ConclusionThe nSIMV mode is as effective as the nCPAP/PS mode in the treatment of patients with ACPE. We believe that the nSIMV mode can be preferable, particularly in patients with hypercarbia who have relatively lower GCS and oxygenation.

History of Intermittent Mandatory Ventilation 1971 to present. Part two

Medical history is often overlooked as advances keep moving forward. Seldom is it that advances in medicine are truly new, unique ideas, but rather built on ideas that have been considered before. Even our latest developments will become history or forgotten as science and medicine advance. This history of intermittent mandatory ventilation (IMV) is a two-part article in which the first part attempts to show that the concepts and apparatus that involve the now common mode of ventilation have been considered and described for nearly 200 years, if not earlier. This older history is not brought forward to diminish what has been done in the last 50 years, but to enhance awareness of how ideas and even mechanical ventilators change over time. This second part will describe how those ideas and mechanics changed into what we now call IMV in its many forms.

C-MAC video laryngoscopy in a difficult airway in a child with nephrotic syndrome with croup and severe neck oedema.

Sir, A 10-year-old boy, a known case of focal segmental glomerulosclerosis, presented to the paediatric emergency with generalised anasarca, neck swelling for seven days, and severe respiratory distress for one day. On examination, the child was conscious, preferentially adopted the sitting posture, and had neck swelling extending up to the sternal angle. His peripheral oxygen saturation (SpO2) was 96% on room air. His neck girth was 40 cm (normal: 26.4-27.2 cm).[1] His height and weight were appropriate for age and sex. Air entry was reduced in bilateral subscapular and interscapular regions. Shifting dullness was present on abdominal examination. The provisional diagnosis was nephrotic syndrome with relapse with bilateral pleural effusion, ascites, and fluid collection in the neck with a probable local-site infection. His investigations revealed hypoproteinaemia, hypercholesterolemia and heavy proteinuria. Frontal view of the chest radiogram revealed the ‘steeple sign’ which was consistent with the diagnosis of acute laryngotracheobronchitis [Figure 1a]. The neck ultrasound showed subcutaneous oedema with fluid extension into the muscular plane. Needle aspirate of the neck swelling, diagnostic pleural and ascitic tap were transudate in nature.Figure 1: (a) Frontal chest X-ray showing ‘steeple sign’ (black solid arrow) with neck oedema till T4 (white arrows) and bilateral pleural effusion (black open arrows); (b) Resolution of ‘steeple sign’, neck oedema and pleural effusion in the index caseDue to increasing neck oedema, impending respiratory failure and anticipated difficult airway, the child was planned for tracheal intubation, in the operating theatre (OT), by a multidisciplinary team consisting of paediatricians, intensivists and otorhinolaryngologist. Tracheostomy consent was taken prior to the procedure. Intravenous glycopyrrolate 0.1 mg was given 30 min before shifting to the OT. SpO2 in the OT was recorded as 86% on room air and 98% on oxygen supplementation. On direct laryngoscopy, mouth opening was equal to 2.5 finger breadths. After opening of mouth and maximum protrusion of the tongue, only soft palate and base of uvula could be seen. Floor of the mouth was not elevated. There was severe glottic oedema with a narrow glottic opening. These findings suggested difficult intubation (Mallampati class III). Pre-oxygenation was done for 3 min, and intravenous midazolam and fentanyl were administered. Injection propofol followed by succinylcholine was given. Four to five low tidal volume breaths were given by face mask ventilation with ease. An attempt at conventional intubation by direct laryngoscopy failed due to poor visibility and narrow glottis. However, he was successfully intubated using C-MAC video laryngoscope (Karl Storz, Tuttlingen, Germany) with acute angle D-blade in combination with Frova introducer with cuffed endotracheal tube of 5 mm internal diameter. The child was shifted to paediatric intensive care unit and put on synchronised intermittent mandatory ventilation mode. Additionally, he was given corticosteroids, albumin infusions and supportive care. He recovered fully after few weeks [Figure 1b]. Neck girth normalised to 27 cm at discharge. The child was regularly followed-up and did well. Croup or laryngotracheobronchitis, a common paediatric emergency, is usually managed with steroids and adrenaline nebulisation. However, less than 2% children with croup require intubation.[2] In our child, glottic oedema due to croup and neck oedema due to relapse of nephrotic syndrome contributed to the difficult airway. Difficult direct laryngoscopy is encountered in 0.06 to 3% children.[3] Failed intubation, a life-threatening situation for the patient, requires anticipation and preparedness. Video laryngoscope is a newer generation device for management of the difficult airway. The presence of a camera at the light source helps in better visualisation of glottis for intubation.[4] Additionally, a Frova introducer aids in entry into the glottis due to its flexible distal tip with a 30° anterior angulation and has an adaptor that allows to oxygenate. It also reduces the risk of tissue damage and bleeding with video laryngoscope.[5] Awake fibreoptic bronchoscopy was not an option in this case due to excessive irritability and age of the child.[56] To conclude, clinical parameters like increased neck circumference of 40 cm or more, and progressive worsening signs like worsening SpO2, and respiratory distress helped us to anticipate a difficult airway and arrange a backup of video laryngoscope.[13] Alternative approaches of securing the airway like video laryngoscopy may be useful in cases of an anticipated difficult airway in children. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.