A bench-to-bedside study about trigger asynchronies induced by the introduction of external gas into the non-invasive mechanical ventilation circuit

Treatments that require the introduction of external gas into the non-invasive ventilation (NIV) circuit, such as aerosol and oxygen therapy, may influence the performance of the ventilator trigger system. The aim of the study was to determine the presence and type of asynchronies induced by external gas in the NIV circuit in a bench model and in a group of patients undergoing chronic NIV. Bench study: Four ventilators (one with two different trigger design types) and three gas sources (continuous flow at 4 and 9 l/min and pulsatile flow at 9 l/min) were selected in an active simulator model. The sensitivity of the trigger, the gas introduction position, the ventilatory pattern and the level of effort were also modified. The same ventilators and gas conditions were used in patients undergoing chronic NIV. Bench: the introduction of external gas caused asynchronies in 35.9% of cases (autotriggering 73%, ineffective effort 27%). Significant differences (p < 0.01) were detected according to the ventilator model and the gas source. In seven patients, the introduction of external gas induced asynchrony in 20.4% of situations (77% autotriggering). As in the bench study, there were differences in the occurrence of asynchronies depending on the ventilator model and gas source used. The introduction of external gas produces alterations in the ventilator trigger. These alterations are variable, and depend on the ventilator design and gas source. This phenomenon makes it advisable to monitor the patient at the start of treatment.

Children’s Privilege in COVID-19: The Protective Role of the Juvenile Lung Morphometry and Ventilatory Pattern on Airborne SARS-CoV-2 Transmission to Respiratory Epithelial Barriers and Disease Severity

The incidence of severe COVID-19 in children is low, and underlying mechanisms for lower SARS-CoV-2 susceptibility and self-limiting disease severity are poorly understood. Severe clinical manifestations in adults require SARS-CoV-2 inoculation in the lower respiratory tract, establishing a pulmonary disease phase. This may be either accomplished by direct inoculation of the thoracic region upon exposure to virion-laden aerosols, or by infection of the upper respiratory system and aspiration of virion-laden aerosols originating right there into the lower respiratory tract. The particularities of epithelial barriers as the anatomical site of first viral deposition specifically determine the initial characteristics of an innate immune response, emerging respiratory tissue damage and dysfunctionality, and hence, severity of clinical symptoms. We, thus, investigated by in silico modeling whether the combined effect of juvenile lung morphometry, children’s ventilatory pattern and the peculiarities of the virion-laden aerosols’ properties, render children more resilient to aerosol deposition in the lower respiratory tract. Our study presents evidence for major age-dependent differences of the regional virion-laden aerosol deposition. We identified deposition hotspots in the alveolar–interstitial region of the young adult. Our data reveal that children are void of corresponding hotspots. The inoculum quantum in the alveolar–interstitial region hotspots is found to be considerably related to age. Our results suggest that children are intrinsically protected against SARS-CoV-2 inoculation in the lower respiratory tract, which may help to explain the lower risk of severe clinical manifestations associated with a pulmonary phase.

Four Truths of Mechanical Ventilation and the Ten-Fold Path to Enlightenment

The Four Truths 1. The truth of confusion 2. The truth of the origin of confusion 3. The truth of the cessation of confusion 4. The truth of the path leading to the cessation of confusion The 10-Fold Path 1. A breath is one cycle of positive flow (inspiration) and negative flow (expiration) defined in terms of the flow-time curve. 2. A breath is assisted if the ventilator does work on the patient. 3. A ventilator assists breathing using either pressure control or volume control based on the equation of motion for the respiratory system. 4. Breaths are classified by the criteria that trigger (start) and cycle (stop) inspiration 5. Trigger and cycle events can be initiated by the patient or the machine. 6. Breaths are classified as spontaneous or mandatory based on both the trigger and cycle events. 7. There are 3 breath sequences: Continuous mandatory ventilation (CMV), Intermittent Mandatory Ventilation (IMV), and Continuous Spontaneous Ventilation (CSV). 8. There are 5 basic ventilatory patterns: VC-CMV, VC-IMV, PC-CMV, PC-IMV, and PC-CSV: 9. Within each ventilatory pattern there are several variations that can be distinguished by their targeting scheme(s). 10. A mode of ventilation is classified according to its control variable, breath sequence, and targeting scheme(s). Keywords: Breath. Trigger, Cycle, Breath sequences, Ventilatory patterns, Mode of ventilation

Technology: A Friend or Foe? Do Electronic Health Records Increase Burn Out Amongst Anaesthesiologists?

3D total laparoscopic hysterectomy in progress under general anaesthesia; steep head low, everyone delighted to see the 3D picture on screen with the goggles including the anaesthesia resident. I enter the OT (needless to say that as a senior one has to supervise more than one OT at a time). The high-end Anaesthesia machine standing tall inside the OT with all the sophisticated monitoring gadgets. I look at the ventilatory pattern on monitor: etCO2 graph upsloping with a value of 42mm of Hg, airway pressure 26mm of Hg and rising! I ask a rhetoric question to my resident as to where his attention is and to my dismay, he expresses his dissatisfaction that the monitors neither give us alarms against rising etCO2 or airway pressure nor do they warn us about changing capnograph slopes!! I am appalled. THROWBACK- Not long time ago when we were residents, we used our ‘educated hands’ to monitor the airway pressure with manual ventilation. Differential diagnosis of tight bag used to be one of the favourite questions seniors used to ask us during on-table teaching. We had no etCO2 monitor then (the mandatory minimum monitoring standard); leave alone the hi-tech ventilatory gadgets and associated airway gas monitoring. Sooner the educated hand was replaced by ventilator and arguments will continue whether to declare this as a loss of clinical skill; an unresolved riddle due to paucity of evidence. The least that I can say is with the hand on pulse and bag in hand, we used to ‘stay connected’ to the patient; with the technical advances this connection got lost. Does this make the ventilator and the advances in monitoring evil?? Obviously not. The advances in science and technology are not only for our comfort but they also play a pivotal role in improving patient’s safety and offering better patient care. Over years surgery has advanced enormously and most of these developments are attributed to advances in the field of anaesthesia which has evolved itself from the Stone Age t

Trigger Asynchronies Induced by the Introduction of External Gas Into the Non-Invasive Mechanical Ventilation Circuit: A Bench-to-Bedside Study

Background and objective: Treatments that require the introduction of external gas into the non-invasive ventilation (NIV) circuit, such as aerosol and oxygen therapy, may influence the performance of the ventilator trigger system. The aim of the study was to determine the presence and type of asynchronies induced by external gas in the NIV circuit in a bench model and in a group of patients undergoing chronic NIV.Methods: Bench study: Four ventilators (one with two different trigger design types) and three gas sources (continuous flow at 4 and 9 l/min and pulsatile flow at 9 l/min) were selected in an active simulator model. The sensitivity of the trigger, the gas introduction position, the ventilatory pattern and the level of effort were also modified.Clinical study: The same ventilators and gas conditions were used in patients undergoing chronic NIV.Results: Bench: The introduction of external gas caused asynchronies in 35.9% of cases (autotriggering 73%, ineffective effort 27%). Significant differences (p<0.01) were detected according to the ventilator model and the gas source.Clinical study: In seven patients, the introduction of external gas induced asynchrony in 20.4% of situations (77% autotriggering). As in the bench study, there were differences in the occurrence of asynchronies depending on the ventilator model and gas source used.Conclusion: The introduction of external gas produces alterations in the ventilator trigger. These alterations are variable, and depend on the ventilator design and gas source. This phenomenon makes it advisable to monitor the patient at the start of treatment.

Lung Function Impairment in Construction Workers – Influence of Smoking and Exposure Duration

AIM: The objective of the study was to assess the influence of exposure duration and smoking on ventilatory impairment among construction workers. METHODS: A cross-sectional study was performed, including 83 construction workers aged 18–64 years, compared to equivalent number of office controls matched by age, workplace exposure duration, and smoking status. Data on chronic respiratory symptoms, work history, and smoking status were collected by standardized questionnaire, while lung functional testing of the examined subjects was performed by spirometry. RESULTS: Mean values of spirometric parameters were lower in construction workers compared to controls with statistical significance registered for maximal expiratory flow (MEF25), MEF50, and MEF75. Lung functions of construction workers have been found to decrease in relation to exposure duration but reached significance only for small airways changes. There was a significant difference in detected ventilatory impairment between exposed workers and controls for any type of ventilatory impairment, as well as obstructive and combined ventilatory pattern and obstructive ventilatory pattern in small airways. Obstructive ventilatory impairment was significantly associated with life-time smoking in construction workers, while obstructive ventilatory pattern in small airways was significantly associated with life-time smoking. The combined effect of daily smoking, life-time smoking, and number of cigarettes smoked daily was shown to have a significant influence in their development. The risk for obstructive ventilatory pattern in small airways among exposed subjects was about 4 fold higher in those exposed more than 20 years (odds ratio [OR] = 3.68 [1.01–14.59] confidence interval [CI] 95%), and about 2.5 fold higher in smokers (OR = 2.57 [0.92-7.25] CI 95%). Exposure duration, smoking and age had independent effect only on small airways changes and force expiratory volume in the 1st s/force vital capacity %. CONCLUSION: Our data suggest the importance of the joint effect of job exposure in construction and daily smoking on the development of lung function impairment and airflow limitation, being dominant, especially on small airways.

Autonomous control of ventilation through closed-loop adaptive respiratory pacing

Mechanical ventilation is the standard treatment when volitional breathing is insufficient, but drawbacks include muscle atrophy, alveolar damage, and reduced mobility. Respiratory pacing is an alternative approach using electrical stimulation-induced diaphragm contraction to ventilate the lung. Oxygenation and acid–base homeostasis are maintained by matching ventilation to metabolic needs; however, current pacing technology requires manual tuning and does not respond to dynamic user-specific metabolic demand, thus requiring re-tuning of stimulation parameters as physiological changes occur. Here, we describe respiratory pacing using a closed-loop adaptive controller that can self-adjust in real-time to meet metabolic needs. The controller uses an adaptive Pattern Generator Pattern Shaper (PG/PS) architecture that autonomously generates a desired ventilatory pattern in response to dynamic changes in arterial CO2 levels and, based on a learning algorithm, modulates stimulation intensity and respiratory cycle duration to evoke this ventilatory pattern. In vivo experiments in rats with respiratory depression and in those with a paralyzed hemidiaphragm confirmed that the controller can adapt and control ventilation to ameliorate hypoventilation and restore normocapnia regardless of the cause of respiratory dysfunction. This novel closed-loop bioelectronic controller advances the state-of-art in respiratory pacing by demonstrating the ability to automatically personalize stimulation patterns and adapt to achieve adequate ventilation.