Inspiratory-expiratory Ratio Research Articles

Evaluation of three approaches used for respiratory measurement in healthy subjects

Objective. Respiration is one of the critical vital signs of human health status, and accurate respiratory monitoring has important clinical significance. There is substantial evidence that alterations in key respiratory parameters can be used to determine a patient’s health status, aid in the selection of appropriate treatments, predict potentially serious clinical events and control respiratory activity. Although various approaches have been developed for respiration monitoring, no definitive conclusions have been drawn regarding the accuracy of these approaches because each has different advantages and limitations. In the present study, we evaluated the performance of three non-invasive respiratory measurement approaches, including transthoracic impedance (IMP), surface diaphragm electromyography-derived respiration (EMGDR) and electrocardiogram-derived respiration (ECGDR), and compared them with the direct measurement of airflow (FLW) in 33 male and 38 female healthy subjects in the resting state. Approach. The accuracy of six key respiratory parameters, including onset of inspiration (Ion ), onset of expiration (Eon ), inspiratory time (It ), expiratory time (Et ), respiratory rate (RR) and inspiratory–expiratory ratio (I:E), measured from the IMP, EMGDR and ECGDR, were compared with those annotated from the reference FLW. Main results. The correlation coefficients between the estimated inspiratory volume and reference value were 0.72 ± 0.20 for IMP, 0.62 ± 0.23 for EMGDR and 0.46 ± 0.21 for ECGDR (p < 0.01 among groups). The positive predictive value and sensitivity for respiration detection were 100% and 100%, respectively, for IMP, which were significantly higher than those of the EMGDR (97.2% and 95.5%, p < 0.001) and the ECGDR (96.9% and 90.0%, p < 0.001). Additionally, the mean error (ME) for Ion , Eon , It , Et and RR detection were markedly lower for IMP than for EMGDR and ECGDR (p < 0.001). Significance. Compared with EMGDR and ECGDR, the IMP signal had a higher positive predictive value, higher sensitivity and lower ME for respiratory parameter detection. This suggests that IMP is more suitable for dedicated respiratory monitoring and parameter evaluation.

Pleth variability index during preoxygenation could predict anesthesia-induced hypotension: A prospective, observational study

Study objectiveTo determine whether changes in the pleth variability index (PVi) during preoxygenation with forced ventilation for 1 min could predict anesthesia-induced hypotension. DesignProspective, observational study. SettingA tertiary teaching hospital. PatientsNinety-six patients who underwent general anesthesia using total intravenous anesthesia were enrolled. InterventionsUpon the patient's arrival at the preoperative waiting area, a PVi sensor was affixed to their fourth fingertip. For preoxygenation, forced ventilation of 8 breaths/min in a 1:2 inspiratory-expiratory ratio was conducted using the guidance of an audio file. One minute after preoxygenation, anesthetic administration was initiated. Blood pressure was measured for the next 15 min. MeasurementsWe calculated the difference (dPVi) and percentage of change (%PVi) between the PVi values immediately before and after forced ventilation. Anesthesia-induced hypotension was defined as a mean arterial pressure of <60 mmHg within 15 min after the infusion of anesthetics. Main resultsOverall, 87 patients were included in the final analysis. Anesthesia-induced hypotension occurred in 31 (35.6%) of the 87 patients. Receiver operating characteristic curve analyses identified a cut-off value of −2 for dPVi, with an area under the curve of 0.691 (95% confidence interval [CI], 0.564–0.818; P < 0.001) and a cut-off value of −7.6% for %PVi, with an area under the curve of 0.711 (95% CI, 0.589–0.832; P < 0.001). Further, multivariate logistic regression analysis showed that a low %PVi with an odds ratio of 9.856 (95% CI, 3.131–31.032; P < 0.001) was a significant determinant of anesthesia-induced hypotension. ConclusionsHypotension frequently occurs during general anesthesia induction and can impact outcomes. Additionally, the percentage change in the PVi before and after preoxygenation using deep breathing can be used to predict anesthesia-induced hypotension.

Effect of ventilator-induced lung injury on blood-brain barrier permeability in rats

To observe the effect of ventilator-induced lung injury (VILI) on blood-brain barrier permeability in rats. Forty-eight healthy clean male Sprague-Dawley (SD) rats were randomly divided into sham operation (Sham) group, low tidal volume (LVT) mechanical ventilation group (LVT group), normal tidal volume (NVT) mechanical ventilation group (NVT group) and high tidal volume (HVT) mechanical ventilation group (HVT group) with 12 rats in each group. After anesthesia, rats in the Sham group were intubated and kept spontaneous breathing. The rats in different tidal volume (VT) groups were mechanically ventilated by endotracheal intubation with VT of 6 mL/kg (LVT group), 10 mL/kg (NVT group), and 20 mL/kg (HVT group), respectively. The inspiration-expiration ratio of the three groups was 1:1, the ventilation frequency was 40 times/min, and the ventilation time was 3 hours. At the end of the experiment, the bronchoalveolar lavage fluid (BALF) of rats was collected, and the levels of pro-inflammatory factors [tumor necrosis factor-α (TNF-α), interleukins (IL-1β and IL-6)] in BALF were detected by enzyme-linked immunosorbent assay (ELISA). The lung tissues of rats were collected, and the lung wet/dry weight (W/D) ratio was calculated. The pathological changes of lung tissues were observed under light microscopy after hematoxylin-eosin (HE) staining, and lung injury scores were performed. The brain tissue of rats was taken to measure the brain water content, and the Evans blue (EB) content of brain tissue was measured to reflect the permeability of the blood-brain barrier. The tight junction proteins in the brain tissues were detected by Western blotting. After 3 hours of mechanical ventilation, with the increase of VT, the degree of lung injury in VILI rats gradually increased. When VT reached 20 mL/kg, lung tissue structure was significantly injured, alveolar wall edema, alveolar congestion, lung interstitial thickening, a large number of inflammatory cells infiltrated, and the lung injury score, lung W/D ratio, and the levels of TNF-α, IL-1β and IL-6 in BALF were significantly higher than those in the Sham group [lung injury score: 10.6±1.1 vs. 1.4±1.0, lung W/D ratio: 6.6±0.8 vs. 3.7±0.6, TNF-α (ng/L): 832.9±97.9 vs. 103.8±23.3, IL-1β (ng/L): 68.9±14.1 vs. 15.7±2.6, IL-6 (ng/L): 70.8±16.4 vs. 20.3±5.4, all P < 0.05]. Lung injury in rats was accompanied by aggravating brain injury. When VT reached 20 mL/kg, brain water content and EB content in brain tissue were significantly higher than those in the Sham group [brain water content: (85.4±3.6)% vs. (68.7±2.7)%, EB content in brain tissue (μg/g): 887±78 vs. 97±14, both P < 0.05], and the protein expressions of claudin-5, occluding and zonula occluden-1 (ZO-1) in the brain tissue were significantly lower than those in the Sham group [claudin-5 protein (claudin-5/β-actin): 0.67±0.12 vs. 1.45±0.19, occludin protein (occludin/β-actin): 0.48±0.11 vs. 0.99±0.21, ZO-1 protein (ZO-1/β-actin): 0.13±0.03 vs. 0.63±0.12, all P < 0.05]. VILI can induce brain edema and increase blood-brain barrier permeability in rats, which may be related to the down-regulation of tight junction protein expression in the brain tissue.

A Multivent System for Non-Invasive Ventilation: Solving the Problem of Ventilator Shortage During the COVID-19 Pandemic

The COVID-19 pandemic has caused a severe global problem of ventilator shortage. Placing multiple patients on a single ventilator (ventilator sharing) or dual patient ventilation has been proposed and conducted to increase the cure efficiency for ventilated patients. However, the ventilator-sharing method needs to use the same ventilator settings for all the patients, which cannot meet the ventilation needs of different patients. Therefore, a novel multivent system for non-invasive ventilation has been proposed in this study. The close loop system consists of the proportional valve and the flow-pressure sensor can regulate the airway pressure and flow for each patient. Multiple ventilation circuits can be combined in parallel to simultaneously meet patients’ ventilation demands. Meanwhile, the mathematical model of the multivent system is established and validated through experiments. The experiments for different inspired positive airway pressure (IPAP), expired positive airway pressure (EPAP), inspiratory expiratory ratio (I:E), and breath per minute (BPM) have been conducted and analyzed to test the performance of the multivent system. The results show that the multivent system can realize the biphasic positive airway pressure (BIPAP) ventilation mode in non-invasive ventilation without interfering among the three ventilation circuits, no matter the change of IPAP, EPAP, I:E, and BPM. However, pressure fluctuation exists during the ventilation process because of the exhaust valve effect, especially in EPAP control. The control accuracy and stability need to be improved. Nevertheless, the novel designed multivent system can bring innovation to the current mechanical ventilation system and solve the problem of ventilator shortage for major, new, and emerging respiratory infectious diseases in the future.

Effect of intraoperative alveolar recruitment maneuver on intraoperative oxygenation and postoperative pulmonary function tests in patients undergoing robotic-assisted hysterectomy: a single-blind randomized study

BackgroundRobotic-Assisted Hysterectomies (RAH) require Trendelenburg positioning and pneumoperitoneum, which further accentuate alteration in respiratory mechanics induced by general anesthesia. The role of Recruitment Maneuver (RM) as a lung-protective strategy during intraoperative surgical settings has not been much studied. We planned this study to evaluate the effect of RM on perioperative oxygenation and postoperative spirometry using PaO2/FiO2 and FEV1/FVC, respectively in patients undergoing RAH. MethodsSixty-six ASA I‒II female patients scheduled for elective RAH were randomized into group R (recruitment maneuver, n = 33) or group C (control, n = 33). Portable spirometry was done one day before surgery. Patients were induced with general anesthesia, and mechanical ventilation started with volume control mode, with Tidal Volume (TV) of 6–8 mL.kg−1, Respiratory Rate (RR) of 12 min, inspiratory-expiratory ratio (I: E ratio) of 1:2, FiO2 of 0.4, and Positive End-Expiratory Pressure (PEEP) of 5 cmH2O. Patients in group R received recruitment maneuvers of 30 cmH2O every 30 minutes following tracheal intubation. The primary objectives were comparison of oxygenation and ventilation between two groups intraoperatively and portable spirometry postoperatively. Postoperative pulmonary complications, like desaturation, pulmonary edema, pneumonia, were monitored. ResultsPatients who received RM had significantly higher PaO2 (mmHg) (203.2+-24.3 vs. 167.8+-27.3, p < 0.001) at T2 (30 min after the pneumoperitoneum). However, there was no significant difference in portable spirometry between the groups in the postoperative period (FVC, 1.40 ± 0.5 L vs. 1.32 ± 0.46 L, p = 0.55). ConclusionThis study concluded that intraoperative recruitment did not prevent deterioration of postoperative spirometry values; however, it led to improved oxygenation intraoperatively.

Parameters of high-frequency jet ventilation using a mechanical lung model

High frequency jet ventilationis a mechanical lung ventilation method which uses a relatively high flow usually through an open system. This work examined the effect of high-frequency jet ventilation on respiratory parameters of an intubated patient simulated using a high-frequency jet ventilator attached to a ventilation monitor for measurements of ventilation parameters. The series of experiments altered specific parameters each time (respiratory rate, inspiratory-expiratory (I:E) ratio, and inspiratory pressure), under different lung compliances. A reduction of minute ventilation was observed alongside a rise in respiratory rate, with low airway pressures over the entire range of lung compliances. In addition, an I:E ratio of 2:1 to 1:1; and the tidal and minute volumes were directly related to the inspiratory pressure over all compliance settings. To conclude, the respiratory mechanics in high-frequency jet ventilation are very different from those of conventional rate ventilation in a lung model. Further studies on patients and/or a biological model are needed to investigate pCO2 and end-tidal carbon-dioxide during high-frequency jet ventilation.

Use of a Viral Filter to Reduce Exposure to Exhaled Aerosol Does Not Affect Methacholine Dose Delivery During Bronchoprovocation Testing.

Methacholine challenge testing (MCT) is a common bronchoprovocation technique used to assess airway hyper-responsiveness. We previously demonstrated that the addition of a viral filter to the nebulizer exhalation limb substantially reduced expelled particles during MCT. Our aim was to evaluate whether this modification affects the delivered dose of methacholine. A mechanical ventilator was connected to a lung simulator with breathing frequency 15 breaths/min, tidal volume 500 mL, inspiratory-expiratory ratio 1:1, with a sinusoidal waveform. We compared methacholine dose delivery using the Hudson Micro Mist or AeroEclipse II BAN nebulizers powered by either a dry gas source or a compressor system. A filter placed in line between the nebulizer and test lung was weighed before and after 1 min of nebulized methacholine delivery. Mean inhaled mass was measured with and without a viral filter on the exhalation limb. Dose delivery was calculated by multiplying the mean inhaled mass by the respirable fraction (particles < 5 μm) and inhalation time. Unpaired t test was used to compare methacholine dose delivery with and without viral filter placement. The addition of a viral filter did not significantly affect methacholine dose delivery across all devices tested. Using a 50-psi dry gas source, dose delivered with or without a viral filter did not differ with the Hudson (422.3 μg vs 282.0 μg, P = .11) or the AeroEclipse nebulizer (563.0 μg vs 657.6 μg, P = .59). Using the compressor, dose delivered with and without a viral filter did not differ with the Hudson (974.0 μg vs 868.0 μg, P = .03) or the AeroEclipse nebulizer (818.0 μg vs 628.5 μg, P = .42). The addition of a viral filter to the nebulizer exhalation limb did not affect methacholine dose during bronchoprovocation testing. Routine use of a viral filter should be considered to improve pulmonary function technician safety and infection control measures during the ongoing COVID-19 pandemic.

Immediate effects of ‘Ujjayi Pranayama’ on aerodynamic, acoustic and self perception parameters of voice in teachers

BackgroundVoice plays a major role in communication, and it reveals the speaker's physical and emotional health, personality, and identity. Professional voice users are dependent on their voice for their livelihood. A minimal change or deviation in their voice can interfere with their career. Since respiration is the source for voice production, good lung capacity and the inspiratory-expiratory ratio are very important in maintaining a good voice quality. Ujjayi Pranayama, an effective breathing technique is targeted in this study. ObjectiveTo investigate the immediate effects of Ujjayi pranayama on acoustic, aerodynamic and self-perception parameters of voice in teachers. MethodTwenty normophonic female teachers performed this breathing technique taught by yoga professional. Parameters of aerodynamic, acoustic, and self-perception were analyzed at pre and post-practice. ResultsSignificant differences in the acoustic variables including intensity and jitter were observed. Aerodynamic parameters have shown significant improvements in the variables including Maximum phonation Duration (MPD), Estimated Subglottal Pressure (ESGP), Laryngeal Conductance (LAC), Laryngeal Resistance (LAR) and Sound Pressure Level (SPL). Among the study participants, 80% have rated the Ujjayi pranayama as useful in prepping their voice for the vocal loading tasks. ConclusionIn view of the better objective evidence and significant improvements in the study variables including the participant's self-perception, authors suggest that Ujjayi pranayama can also be used in voice rehabilitation as a vocal warm-up exercise.

Development of Digital Ventilator with Internet of Things for Preparation of the Next Outbreak in Indonesia

The emergency of the healthcare device unit, such as a ventilator, has been experienced during the COVID-19 pandemic in 2020. Therefore, ventilator usage is not hard suggested anymore for COVID-19 patients compared to the outbreak beginning. Despite that, it is still essential to have the ventilator ready, if possible, in each house, for the upcoming respiratory syndrome outbreak. Therefore, in this paper, a digital ventilator development is presented. The digital ventilator is comprised of three main parts, such as respiration mechanism (I), controller Internet of Things (IoT) module (II), and website application (III). The developed digital ventilator has been tested by comparing the measurement of respiratory data between the developed digital ventilator and gas flow analyzer. Results show that the respiratory data, such as Pressure Peak (PPeak), Positive End Respiratory Pressure (PEEP), Inspiratory Expiratory Ratio (IE Ratio), Breath per Minute (BPM), and Tidal Volume can be monitored and controlled both directly and online via website application consistently (standard deviation around 10%) with PPeak absolute error of 1.35 mbar, the PEEP absolute error of 0.16 mbar. Furthermore, the average time response of the digital ventilator to the input command from the website application is 0.23 s. Therefore, it is safe to assume that the doctor can use the website application to control the digital ventilator remotely.

Relationship of breathing pattern with vascular tone and arterial stiffness in young healthy individuals

Objectives: A dynamic interaction exists between respiration, cardiovascular system, and autonomic nervous regulatory mechanisms as demonstrated by respiratory sinus arrhythmia. The vascular tone might also demonstrate a similar variability during inspiration and expiration. The breathing patterns by influencing the sympathetic outflow may have an impact on the vascular tone and hence cardiovascular system at large. The present study was undertaken to assess the quiet breathing pattern and its relation with vascular tone, hemodynamics, and arterial stiffness in normal young healthy individuals. Materials and Methods: The study involved 46 young healthy adults (both males and females) aged 19–25 years. Breathing parameters included were respiratory rate (RR), inspiration time (IT), expiration time (ET), and inspiration-expiration ratio (I/E ratio). Vascular parameters included were reflection index (reflects vascular tone) and stiffness index (reflects arterial stiffness). Blood pressure (BP in mmHg) and heart rate (bpm) were measured. Results: IT and ET were almost equal with no significant difference. ET was weekly correlated with diastolic BP (r = −0.410; P = 0.058) in females but not in males. Breathing pattern was not significantly associated with vascular tone and arterial stiffness. Conclusion: IT, ET, I/E ratio, and RR were not significantly correlated with vascular tone and arterial stiffness suggesting that breathing does not influence the arterial health and function in young healthy individuals. There was a weak negative correlation between ET and diastolic BP in females but not in males, implicating the existence of fundamental differences in basic BP regulation between the sexes.

Design and Implementation of Ventilator for Breathing Apparatus

This paper present the design and implementation of a ventilator for a breathing apparatus. The ventilators that developed are the positive pressure ventilation type, the cycled volume mode and the controlled mechanical ventilation method (CMV). The technology that used is the ambu bag. The design and manufacture includes an automatic ambu bag pressing mechanical system and a control system using the arduino microcontroller. The mechanical design that is compact, lightweight, energy saving, low cost, meets aesthetics and is friendly makes this tool attractive so it is not scary for patients. BPM (beep per minute), IER (inspiratory expiratory ratio) and TV (tidal volume) parameters can be controlled via a touch screen or remotely using a mobile phone via 4 buttons remotely to facilitate and avoid transmission of Covid-19 to medical personnel. BPM can be set from 5-20 BPM, IER from 1: 1 to 1: 4 and TV from 40-100%. The results of ventilator testing that have been done show a good response.

Efficacy of Automatic Retention Pressure of a Double-Lumen Tube Cuff: An Artificial Intubation Model

BackgroundThe movement of a double-lumen endotracheal tube (DLT) out of its appropriate position during thoracic surgery can result in the loss of one-lung ventilation (OLV), especially during pulmonary resection and node dissection. Our study aimed to validate the efficacy of automatic retention pressure control of the DLT bronchial cuff in maintaining OLV in an artificial intubation model. Materials and methodsA 35-Fr left-sided DLT was intubated to the left main bronchus in an intubation simulator and connected to an anesthesia machine. The inspiratory volume, respiratory rate, and inspiratory-expiratory ratio were set at 500 mL, 12 times/min, and 1:2, respectively. A 1-kg right main bronchial traction in the lateral right was provided after OLV was established. SmartCuff (Smiths Medical, Minneapolis, Minnesota, USA) was used to maintain cuff pressure. The efficacy of retention pressure with SmartCuff (Group S) and without SmartCuff (Group WS) was compared. The primary outcome was the rate of tidal volume (TV) reduction following bronchial traction in the two groups. ResultsThe TVs were 289.8 ± 28.9 mL and 242.8 ± 31.9 mL in Group S and Group WS, respectively (P = 0.003). The rate of TV reduction after bronchial traction was significantly lower in Group S (29 ± 5%) than in Group WS (43 ± 6%) (P < 0.001). ConclusionsAutomatic retention pressure control of the DLT bronchial cuff improves the rate of TV reduction during right main bronchial traction in an artificial intubation model. Continuous retention cuff pressure may be useful in maintaining OLV during thoracic surgery.

Derivation of Breathing Metrics From a Photoplethysmogram at Rest: Machine Learning Methodology.

BackgroundThere has been a recent increased interest in monitoring health using wearable sensor technologies; however, few have focused on breathing. The ability to monitor breathing metrics may have indications both for general health as well as respiratory conditions such as asthma, where long-term monitoring of lung function has shown promising utility.ObjectiveIn this paper, we explore a long short-term memory (LSTM) architecture and predict measures of interbreath intervals, respiratory rate, and the inspiration-expiration ratio from a photoplethysmogram signal. This serves as a proof-of-concept study of the applicability of a machine learning architecture to the derivation of respiratory metrics.MethodsA pulse oximeter was mounted to the left index finger of 9 healthy subjects who breathed at controlled respiratory rates. A respiratory band was used to collect a reference signal as a comparison.ResultsOver a 40-second window, the LSTM model predicted a respiratory waveform through which breathing metrics could be derived with a bias value and 95% CI. Metrics included inspiration time (–0.16 seconds, –1.64 to 1.31 seconds), expiration time (0.09 seconds, –1.35 to 1.53 seconds), respiratory rate (0.12 breaths per minute, –2.13 to 2.37 breaths per minute), interbreath intervals (–0.07 seconds, –1.75 to 1.61 seconds), and the inspiration-expiration ratio (0.09, –0.66 to 0.84).ConclusionsA trained LSTM model shows acceptable accuracy for deriving breathing metrics and could be useful for long-term breathing monitoring in health. Its utility in respiratory disease (eg, asthma) warrants further investigation.

Laryngeal mask versus facemask in the respiratory management during catheter ablation

BackgroundThe purpose of this study is to investigate if a laryngeal mask could improve respiratory condition during radiofrequency catheter ablation (RFCA).MethodsTwenty-four consecutive patients who underwent RFCA for atrial fibrillation were divided into two groups (Facemask group; n = 10, Laryngeal mask group; n = 14). All patients were completely sedated under intravenous anesthesia and fitted with artificial respirators during the RFCA. The capnography waveforms and their differential coefficients were analyzed to evaluate the changes of end-tidal CO2 (ETCO2) values, respiratory intervals, expiratory durations, and inspiratory durations.ResultsDuring the RFCA, ETCO2 values of the laryngeal mask group were higher than those of the facemask group (36.0 vs. 29.2 mmHg, p = 0.005). The respiratory interval was significantly longer in the laryngeal mask group than those in the facemask group (4.28 s vs.5.25 s, p < 0.001). In both expiratory and inspiratory phases, the mean of the maximum and minimum values of CO2 was significantly higher when using a laryngeal mask than when using a facemask. The inspiratory-expiratory ratio of the laryngeal mask group was significantly larger than that of the facemask group (1.59 vs. 1.27, p < 0.001). The total procedure duration, fluoroscopic duration and the ablation energy were significantly lower in the laryngeal mask group than in the facemask group. The ETCO2 value is the most influential parameter on the fluoroscopic duration during the RFCA procedure (β = − 0.477, p = 0.029).ConclusionsThe use of a laryngeal mask could stabilize respiration during intravenous anesthesia, which could improve the efficiency of RFCA.

Clinical application of adaptive minute ventilation + IntelliCycle ventilation mode in patients with mild-to-moderate acute respiratory distress syndrome

To verify the clinical safety and efficacy of new intelligent ventilation mode adaptive minute ventilation (AMV)+IntelliCycle ventilation in patients with mild-to-moderate acute respiratory distress syndrome (ARDS). The patients with mild-to-moderate ARDS, admitted to intensive care unit (ICU) of the First Affiliated Hospital of Jinzhou Medical University from February 2018 to February 2019, were enrolled in the study. The patients were divided into synchronous intermittent mandatory ventilation+pressure support ventilation (SIMV+PSV) group and AMV+IntelliCycle group according to the random number table method. All patients were given mechanical ventilation, anti-infection, analgesia and sedation, nutritional support and symptomatic treatment of primary disease after admission. SV800 ventilator was used for mechanical ventilation. In the AMV+IntelliCycle group, after setting the minute ventilation volume (VE), inhaled oxygen concentration (FiO2) and positive end expiratory pressure (PEEP), the ventilator was turned on the full-automatic mode, and the preset value of VE percentage was 120%. In the SIMV+PSV group, the ventilator parameters were set as follows: the ventilation frequency was 12-20 times/min, the inspiratory expiratory ratio was 1:1-2, the peak inspiratory pressure (PIP) limit level was 35-45 cmH2O (1 cmH2O = 0.098 kPa), and the setting of FiO2 and PEEP was as the same as that of AMV+IntelliCycle group, the triggering flow was set to 2 L/min. All of the clinical parameters between the two groups were compared. The main outcomes were duration of mechanical ventilation, ventilator alarm times, manual operation times, and the mechanical power; the secondary outcomes were respiratory rate (RR), VE, tidal volume (VT), PIP, mouth occlusion pressure (P0.1), static compliance (Cst), work of breathing (WOB), and time constant at 0, 6, 12, 24, 48, 72, and 120 hours; and the blood gas analysis parameters of patients before and after ventilation were recorded. A total of 92 patients with mild-to-moderate ARDS were admitted during the study period, excluding those who quit the study due to death, abandonment of treatment, accidental extubation of tracheal intubation and so on. Eighty patients were finally enrolled in the analysis, with 40 patients in SIMV+PSV group and AMV+IntelliCycle group respectively. (1) Results of main outcomes: compared with the SIMV+PSV mode, AMV+IntelliCycle ventilation mode could shorten the duration of mechanical ventilation (hours: 106.35±55.03 vs. 136.50±73.78), reduce ventilator alarm times (times: 10.35±5.87 vs. 13.93±6.87) and the manual operations times (times: 4.25±2.01 vs. 6.83±3.75), and decrease the mechanical power (J/min: 12.88±4.67 vs. 16.35±5.04, all P < 0.05). But the arterial partial pressure of carbon dioxide (PaCO2) of AMV+IntelliCycle group was significantly higher than that of SIMV+PSV group [mmHg (1 mmHg = 0.133 kPa): 41.58±6.81 vs. 38.45±5.77, P < 0.05]. (2) Results of secondary outcomes: the RR of both groups was improved significantly with the prolongation of ventilation time which showed a time effect (F = 4.131, P = 0.005). Moreover, compared with SIMV+PSV mode, AMV+IntelliCycle mode could maintain a better level of RR, with intervention effect (F = 5.008, P = 0.031), but no interaction effect was found (F = 2.489, P = 0.055). There was no significant difference in VE, PIP, P0.1 or Cst between the two groups, without intervention effect (F values were 3.343, 2.047, 0.496, 1.456, respectively, all P > 0.05), but they were significantly improved with the prolongation of ventilation time in both groups, with time effect (F values were 2.923, 12.870, 23.120, 7.851, respectively, all P < 0.05), but no interaction effect was found (F values were 1.571, 1.291, 0.300, 0.354, respectively, all P > 0.05). The VT, WOB or time constant in both groups showed no significant changes with the prolongation of ventilation time, and no significant difference was found between the two groups, there was neither time effect (F values were 0.613, 1.049, 2.087, respectively, all P > 0.05) nor intervention effect (F values were 1.459, 0.514, 0.923, respectively, all P > 0.05). AMV+IntelliCycle ventilation mode can shorten the ventilation time of patients with mild-to-moderate ARDS, reduce mechanical power, and reduce the workload of medical care, but PaCO2 in the patients with AMV+IntelliCycle mode is higher than that in the patients with SIMV+PSV mode.

Different particle flow patterns from the airways after recruitment manoeuvres using volume-controlled or pressure-controlled ventilation

ObjectivesNoninvasive online monitoring of different particle flows from the airways may serve as an additional tool to assess mechanical ventilation. In the present study, we used a customised PExA, an optical particle counter for monitoring particle flow and size distribution in exhaled air, to analyse airway particle flow for three subsequent days. We compared volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) and performed recruitment manoeuvres (RM).MethodsSix animals were randomised into two groups: half received VCV before PCV and the other half received PCV before VCV. Measurements were taken daily for 1 h in each mode during three subsequent days in six fully anaesthetised domestic pigs. A RM was performed twice daily for 60 s at positive end-expiratory pressure (PEEP) of 10, 4 breaths/min and inspiratory-expiratory ratio (I:E) of 2:1. Measurements were taken for 3 min before the RM, 1 min during the RM and for 3 min after the RM. The particle sizes measured were between 0.48 and 3.37 μm.ResultsA significant stepwise decrease was observed in total particle count from day 1 to day 3, and at the same time, an increase in fluid levels was seen. Comparing VCV to PCV, a significant increase in total particle count was observed on day 2, with the highest particle count occurring during VCV. A significant increase was observed comparing before and after RM on day 1 and 2 but not on day 3. One animal developed ARDS and showed a different particle pattern compared to the other animals.ConclusionsThis study shows the safety and useability of the PExA technique used in conjunction with mechanical ventilation. We detected differences between the ventilation modes VCV and PCV in total particle count without any significant changes in ventilator pressure levels, FiO2 levels or the animals’ vital parameters. The findings during RM indicate an opening of the small airways, but the effect is short lived. We have also showed that VCV and PCV may affect the lung physiology differently during recruitment manoeuvres. These findings might indicate that this technique may provide more refined information on the impact of mechanical ventilation.

An in vitro evaluation of the influence of neonatal endotracheal tube diameter and length on the work of breathing

Neonates, particularly premature babies, are often managed with endotracheal intubation and subsequent mechanical ventilation to maintain adequate pulmonary gas exchange. There is no consensus on the standard length of endotracheal tube. Although a short tube reduces resistance and respiratory dead space, it is believed to increase the risk of accidental extubation. There are not entirely coherent data regarding the effect of endotracheal tube length on work of breathing in infants. The aim of this study was to evaluate the impact of neonatal endotracheal tube diameter and length on the work of breathing using an infant in vitro lung model. We assessed the work of breathing index and mechanical ventilation settings with various endotracheal tube diameters and lengths using the JTR100 invitro infant lung model. The basic parameters of the model were breathing frequency of 20 per minutes, inspiratory-expiratory ratio of 1:3, and positive end-expiratory pressure of 5cmH2 O. In addition, the diaphragm driving pressure to maintain the set tidal volume was measured as the work of breathing index. The JTR100 was connected to the Babylog 8000plus through the endotracheal tube. Finally, we monitored the peak inspiratory pressure generated during assist-control volume guarantee mode with a targeted tidal volume of 10-30mL. The diaphragm driving pressure using a 2.0-mm inner diameter tube was twice as high as that using a 4.0-mm inner diameter tube. To maintain the targeted tidal volume, a shorter tube reduced both the diaphragm driving pressure and ventilator-generated peak inspiratory pressure. The difference in the generated peak inspiratory pressure between the shortest and longest tubes was 5cmH2 O. In our infant lung model, a shorter tube resulted in a lower work of breathing and lower ventilator-generated peak inspiratory pressure.

The effect of pressure-controlled inverse ratio ventilation on lung protection in obese patients undergoing gynecological laparoscopic surgery.

To examine the effects of pressure-controlled inverse ratio ventilation (PCIRV) and volume-control ventilation (VCV) on arterial oxygenation, pulmonary function, hemodynamics, levels of surfactant protein A (SP-A), and tumor necrosis factor-α (TNF-α) in obese patients undergoing gynecological laparoscopic surgery. Sixty patients, body mass index (BMI) ≥30kg/m2, scheduled for elective gynecological laparoscopic surgery were enrolled in the study. Patients were randomly allocated to receive either PCIRV with an inspiratory-expiratory (I:E) ratio of 1.5:1 (PCIRV group n=30) or VCV with an I:E ratio of 1:2 (VCV group n=30). Ventilation variables, viz. tidal volume (V T), dynamic respiratory-system compliance (C RS), driving pressure (ΔP=V T/C RS), arterial blood oxygen partial pressure/fraction of inspiration oxygen (PaO2/FiO2) and arterial blood carbon dioxide partial pressure (PaCO2), were measured. Hemodynamic variables, viz. mean arterial pressure (MAP), heart rate (HR), and serum levels of SP-A and TNF-α, were also measured. When compared to patients in the VCV group, patients in the PCIRV group had higher V T, dynamic CRS, and PaO2/FiO2, and lower ΔP and PaCO2 at 20 and 60min after the start of pneumoperitoneum (p<0.05). Patients in the PCIRV group had lower SP-A and TNF-α levels at 24 and 48h after surgery than those in the VCV group (p<0.05). In obese patients undergoing gynecological laparoscopic surgery, PCIRV can improve ventilation, promote gas exchange and oxygenation, and is associated with decreased levels of SP-A and TNF-α. These effects demonstrate improved lung protection provided by PCIRV in this patient population.

In-vitro/in-vivo comparison of inhaled salbutamol dose delivered by jet nebulizer, vibrating mesh nebulizer and metered dose inhaler with spacer during non-invasive ventilation

ABSTRACTBackground: Patients receiving noninvasive ventilation (NIV) may benefit from medical aerosol, but most guidance on dosing with different aerosol devices is limited to in-vitro studies. The study was designed to in-vitro, ex-vivo, and in-vivo compare aerosol delivery during bilevel NIV with three types of aerosol generators: metered dose inhaler with AeroChamber-MV spacer (AC), Aerogen Pro vibrating mesh nebulizer (PRO), and Sidestream jet nebulizer (SIDE). Materials and Method: A bilevel ventilator with dry single limb circuit and fixed expiratory port was set in spontaneous mode with initial inspiratory and expiratory pressures of 20 and 5 cmH20, 1:3 inspiratory-expiratory ratio, and 15 breaths.min−1. Aerosol generators were placed proximal to facial mask of NIV chronic obstructive pulmonary disease (COPD) patients. 1 mL salbutamol nebulizer solution (5 mg/mL) was nebulized using PRO and SIDE. 12MDI doses, containing 100μg salbutamol each, were delivered using AC. In-vitro aerosol fate and aerodynamic droplet characteristics, in-vivo amount of salbutamol excreted 30 mins and pooled up to 24 h post inhalation in urine from 12 COPD patients (as indices of pulmonary deposition and systemic absorption, respectively) and amount of salbutamol deposited on ex-vivo filters (expected inhalable amount) was determined. Results: The in-vitro, in-vivo and ex-vivo testing showed that PRO had better aerosol delivery compared to SIDE (p < 0.01). However, with smaller nominal dose MDI with AC resulted in similar aerosol delivery to PRO suggesting better aerosol delivery stress on careful attention and proper delivery by health care provider. Conclusions: These similarities and differences between the three aerosol generators tested suggest that aerosol delivery methods should be carefully chosen or substituted in non-invasive ventilated patients.

In vitro aerodynamic characteristics of aerosol delivered from different inhalation methods in mechanical ventilation

Aerodynamic characteristics of aerosol delivery during invasive mechanical ventilation (IMV) are mostly determined by inserting cascade impactor in the circuit. Impactor might have some effect on airflow within IMV. Hence, the aim of the present study was to develop and evaluate new in vitro aerodynamic characterization methodology without affecting airflow in IMV. Breathing simulator was set in standard adult IMV circuit with inspiratory and expiratory pressures of 20 and 5 cm H2O, 1:3 inspiratory–expiratory ratio, 15 breaths min−1, and tidal volume of 500 ml. Two ml of salbutamol solution containing 10,000 μg was nebulized using three different vibrating mesh nebulizers (VMNs) and Sidestream jet nebulizer (JET). Sixteen-metered doses, containing 100 μg salbutamol each, were delivered using three different spacers. Each device was placed in inspiration limb of Y-piece of ventilator tubing. Aerodynamic characteristics of aerosol delivered were measured using cooled Andersen cascade impactor, with mixing inlet connected to it. VMNs used had significantly more total mass in the impactor (p < .001) and fine particle dose (p < .001) compared to JET. Spacers used had higher total mass in the impactor percent (p < .001) and fine particle fraction compared to nebulizers. The in vitro IMV methodology setting suggested here showed encouraging results in comparison of different aerosol delivery systems in intubated patient.