Expiratory Phase Research Articles

Evaluation of alveolar recruitment maneuver on respiratory resistance during general anesthesia: a prospective observational study

BackgroundAlveolar recruitment maneuvers enable easily reopening nonaerated lung regions via a transient elevation in transpulmonary pressure. To evaluate the effect of these maneuvers on respiratory resistance, we used an oscillatory technique during mechanical ventilation. This study was conducted to assess the effect of the alveolar recruitment maneuvers on respiratory resistance under routine anesthesia. We hypothesized that respiratory resistance at 5 Hz (R5) after the maneuver would be decreased after the lung aeration.MethodsAfter receiving the ethics committee’s approval, we enrolled 33 patients who were classified with an American Society of Anesthesiologists physical status of 1, 2 or 3 and were undergoing general anesthesia for transurethral resection of a bladder tumor within a 12-month period from 2017 to 2018. The recruitment maneuver was performed 30 min after endotracheal intubation. The maneuver consisted of sustained manual inflation of the anesthesia reservoir bag to a peak inspiratory pressure of 40 cmH2O for 15 s, including 5 s of gradually increasing the peak inspiratory pressure. Respiratory resistance was measured using the forced oscillation technique before and after the maneuver, and the mean R5 was calculated during the expiratory phase. The respiratory resistance and ventilator parameter results were analyzed using paired Student’s t-tests, and p < 0.05 was considered statistically significant.ResultsWe analyzed 31 patients (25 men and 6 women). R5 was 7.3 ± 1.6 cmH2O/L/sec before the recruitment maneuver during mechanical ventilation and was significantly decreased to 6.4 ± 1.7 cmH2O/L/sec after the maneuver. Peak inspiratory pressure and plateau pressure were significantly decreased, and pulmonary compliance was increased, although the values were not clinically relevant.ConclusionThe recruitment maneuver decreased respiratory resistance and increased lung compliance during mechanical ventilation.Trial registrationName of registry: Japan Medical Association Center for Clinical Trials.Trial registration number: reference JMA-IIA00136.Date of registration: 2 September 2013.URL of trial registry record: https://dbcentre3.jmacct.med.or.jp/JMACTR/App/JMACTRE02_04/JMACTRE02_04.aspx?kbn=3&seqno=3582

VANISHING LUNGS IN SARCOID DISEASE

SESSION TITLE: Medical Student/Resident Pulmonary Manifestations of Systemic Disease Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Sarcoidosis is a multi-system disease with an unclear etiology that is characterized by non-caseating granulomas, T lymphocytes and mononuclear phagocytes in involved tissues. Hilar adenopathy is the most common initial manifestation with bullous emphysema being more of a rare outcome with an aggressive course. CASE PRESENTATION: A 39-year-old male smoker presented with recurrent bronchopulmonary infections. He had been prescribed steroids and antibiotics with interval improvement in the past. The patient endorsed shortness of breath on exertion with wheezing and a productive cough with clear phlegm. Vital signs and spot pulse oximetry were within normal range. A physical examination revealed decreased breath sounds throughout all lung fields as well as prolonged expiratory phase however no added sounds were appreciated. Laboratory values were within normal limit. Initial chest x-ray showed hilar adenopathy and follow up computed tomography (CT) scan showed chronic pulmonary nodularity with coalescent regions, predominantly affecting the upper lobes and superior segments of the lower lobes with mediastinal hilar lymphadenopathy. Pulmonary Function Test (PFT) showed severe obstructive disease and hyperinflation with air trapping. He subsequently underwent bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsy. Tissue pathology showed non-caseating granulomatous inflammation confirming sarcoidosis. He was started on oral prednisone with minimal improvement and maximal inhaler therapy was added with initial improvement however later, his symptoms progressed, and he suffered significant decline in lung capacity. The 1 year follow up CT scan revealed early emphysematous changes that progressed quickly over the course of 3 years into severe emphysema and he eventually required supplemental oxygen. DISCUSSION: The bullous form of sarcoidosis was first reported in 1949. The etiology of emphysema is thought to be related to the obstruction of bronchioles from extrinsic pressure due to lymphadenopathy and endobronchial disease, causing peripheral air trapping and alveolar distention. Cavitary lung disease in sarcoidosis may form as a result of infection however true primary cavities formed by sarcoid granulomas of the walls are extremely rare. Most patients had been noted to have bullous changes within 3–4 years of symptom development. The diagnosis of emphysema is made from radiographic appearance, in addition to a decrease in diffusing capacity and lung volumes. Treatment is primarily medical, consisting of corticosteroids and immunosuppressive agents. Bullectomies are performed if disease is localized. In severe disease, lung transplantation is performed as a final option. CONCLUSIONS: Clinicians should be aware of progressive sarcoid with underlying emphysema as managing this group of patients can be particularly challenging given the aggressive nature of the disease. Reference #1: Jeebun V, Forrest IA. Sarcoidosis: An under-recognised cause for bullous lung disease? Eur Respir J. 2009;34(4):999-1001. doi:10.1183/09031936.00084609 Reference #2: Burke RM. Vanishing Lungs: A Case Report of Bullous Emphysema. Radiology. 1937;28(3):367-371. doi:10.1148/28.3.367 Reference #3: Miller A. The vanishing lung syndrome associated with pulmonary sarcoidosis. Br J Dis Chest. 1981;75(2):209-214. DISCLOSURES: No relevant relationships by Mohammed Al-Ourani, source=Web Response No relevant relationships by Yasmeen Obeidat, source=Web Response No relevant relationships by Batarseh Rami, source=Admin input

Management of Cough

Cough is the most frequent symptom for which patients consult with their health care provider throughout the world. This symptom could be happened not only in sick individuals but also healthy individuals. At some stage, it is distressing, inhibits normal social activities, and reduces quality of life. Besides these detrimental effects, cough is the most effective defense mechanism to eliminate foreign materials, including various pathogens, from the respiratory tract. It begins with a series of breathing maneuvers which triggers sudden expulsion of air which is divided into three phases, i.e. inspiration, compression, and expiration phase. Cough occurs due to activation of mechanical or chemical sensory receptors in the larynx and lower respiratory tract which stimulates reflex arc complex. This stimulus is then transmitted to the afferent pathway to the cough center in the medulla through the vagus nerve to trigger expiration muscles to produce cough. It is important to know the cause of cough because cough is an indicator for patients and doctors for early diagnosis and therapy of disease. Therefore, cough is classified into acute, subacute, and chronic according to its duration. Available medications for symptomatic management of cough are inadequate due to lack of proven efficacy and/or their undesirable or intolerable side effects. This article aims to provide information on cough management to improve therapeutic effectiveness and patient quality of life.

Tumor phase recognition using cone-beam computed tomography projections and external surrogate information.

Directly extracting the respiratory phase pattern of the tumor using cone-beam computed tomography (CBCT) projections is challenging due to the poor tumor visibility caused by the obstruction of multiple anatomic structures on the beam's eye view. Predicting tumor phase information using external surrogate also has intrinsic difficulties as the phase patterns between surrogates and tumors are not necessary to be congruent. In this work, we developed an algorithm to accurately recover the primary oscillation components of tumor motion using the combined information from both CBCT projections and external surrogates. The algorithm involved two steps. First, a preliminary tumor phase pattern was acquired by applying local principal component analysis (LPCA) on the cropped Amsterdam Shroud (AS) images. In this step, only the cropped image of the tumor region was used to extract the tumor phase pattern in order to minimize the impact of pattern recognition from other anatomic structures. Second, by performing multivariate singular spectrum analysis (MSSA) on the combined information containing both external surrogate signal and the original waveform acquired in the first step, the primary component of the tumor phase oscillation was recovered. For the phantom study, a QUASAR respiratory motion phantom with a removable tumor-simulator insert was employed to acquire CBCT projection images. A comparison between LPCA only and our method was assessed by power spectrum analysis. Also, the motion pattern was simulated under the phase shift or various amplitude conditions to examine the robustness of our method. Finally, anatomic obstruction scenarios were simulated by attaching a heart model, PVC tubes, and RANDO® phantom slabs to the phantom, respectively. Each scenario was tested with five real-patient breathing patterns to mimic real clinical situations. For the patient study, eight patients with various tumor locations were selected. The performance of our method was then evaluated by comparing the reference waveform with the extracted signal for overall phase discrepancy, expiration phase discrepancy, peak, and valley accuracy. In tests of phase shifts and amplitude variations, the overall peak and valley accuracy was -0.009±0.18sec, and no time delay was found compared to the reference. In anatomical obstruction tests, the extracted signal had 1.6±1.2 % expiration phase discrepancy, -0.12±0.28sec peak accuracy, and 0.01±0.15sec valley accuracy. For patient studies, the extracted signal using our method had -1.05±3.0 % overall phase discrepancy, -1.55±1.45% expiration phase discrepancy, 0.04±0.13sec peak accuracy, and -0.01±0.15sec valley accuracy, compared to the reference waveforms. An innovative method capable of accurately recognizing tumor phase information was developed. With the aid of extra information from the external surrogate, an improvement in prediction accuracy, as compared with traditional statistical methods, was obtained. It enables us to employ it as the ground truth for 4D-CBCT reconstruction, gating treatment, and other clinic implementations that require accurate tumor phase information.

Impact of end-expiratory pressure fluctuation on tidal volume in the trilevel positive airway pressure mode.

In noninvasive positive-pressure ventilation (NPPV), the changes in the expiratory positive airway pressure (EPAP) directly affect the magnitude of the tidal volume. This experimental study aims to verify the precise effects of end-expiratory fluctuation on the body tidal volume to better assist NPPV in clinical practice. We selected the TestChest-simulated lung simulation of different populations, including healthy subjects (normal group), patients with chronic obstructive pulmonary disease (COPD) with emphysema as their primary phenotype (COPD1 group), and patients with COPD with bronchitis as their primary phenotype (COPD2 group). Regarding the tidal volume curves of the three groups under various conditions, sixfold charts revealed that the tidal volume changed with the end-expiratory pressure fluctuations. In addition, regression coefficients for end-expiratory pressure fluctuations, (IPAP-EPAP) and (IPAP-EEPAP) exhibited a significant contribution to the tidal volume. The two coefficients in the normal, COPD1 and COPD2 groups were 52.294 and 10.414, 46.192 and -8.816, and 11.922 and 17.947, respectively. The circuit simulation results showed that the simulation curve fitted the experimental curve better by changing the coefficient of the descending edge of the expiratory phase. The study results suggest that the end-expiratory pressure fluctuation affects the body tidal volume. Compared with the bilevel positive airway pressure (PAP), the trilevel PAP provides additional respiratory support to the body during a respiratory difference in initial respiration and descent.

&lt;p&gt;Evaluation of Exertional Ventilatory Parameters Using Oscillometry in COPD&lt;/p&gt;

BackgroundOscillometry is a tool to measure respiratory impedance that requires minimal patients’ effort. In patients with chronic obstructive pulmonary disease (COPD), the correlation of respiratory impedance at rest with exertional ventilatory parameters, including exercise tolerance, has scarcely been reported. In addition, the utility of oscillometric parameters might differ between the inspiratory and expiratory phases due to airflow obstruction during expiration, but the hypothesis had not been validated. The aim of the present study was to investigate whether oscillometric parameters are associated with exertional ventilatory parameters in patients with COPD.MethodsFifty-five subjects with COPD who attended clinics at the National Hospital Organization Osaka Toneyama Medical Center performed spirometry, oscillometry, and cardiopulmonary exercise testing (CPET) within 2 weeks. The correlations between parameters of spirometry, oscillometry, and CPET were analyzed using Spearman’s rank correlation coefficient, univariate, and multivariate analyses.ResultsRespiratory reactance had better correlations with the CPET parameters than respiratory resistance. Moreover, inspiratory reactance at rest correlated with the CPET parameters stronger than expiratory reactance. In particular, inspiratory resonant frequency (Fres-ins) correlated with peak oxygen uptake (rS=−0.549, p<0.01) and dead space to tidal volume ratio at peak exercise (rS=0.677, p<0.01) and the best predicted expiratory tidal volume (VT ex) at peak exercise of all the oscillometric parameters (rS=−0.679, p<0.01). However, the correlation between Fres-ins and VT ex at peak exercise became weak in subjects with severe and very severe COPD during exercise.ConclusionMeasurement of respiratory reactance is useful for the effortless evaluation of not only exertional ventilatory parameters but exercise tolerance in patients with COPD. The correlation of respiratory impedance with exertional ventilatory parameters can become weak in patients with advanced COPD; thus, the measurement of oscillometry might not be appropriate for evaluating exertional ventilatory parameters of patients with advanced COPD.

How to improve CPAP failure prediction in preterm infants with RDS: a pilot study.

We aimed to test the diagnostic accuracy in predicting continuous positive airway pressure (CPAP) failure in premature infants with respiratory distress syndrome (RDS) by integrating oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) (SF ratio) with the measurement of peak velocity of the right diaphragmatic excursions (RD-PV), during the inspiration (I-Peak) and expiratory (E-Peak) phases, performed by pulsed-wave Tissue Doppler imaging. This is a prospective, observational pilot study conducted over a 2-year period. Neonates at ≤ 32 weeks gestation supported by early CPAP were eligible. Natural surfactant was delivered via a minimally invasive technique. We performed serial measurements of SF ratio and RD-PV during the early post-natal hours to test the accuracy in predicting surfactant administration as well as invasive ventilation support within 72 h from birth because of the RDS worsening. Of 56 preterm infants enrolled, 34 (61%) failed CPAP support. SF ratio showed a significant inverse relationship with both Silverman-Andersen score at birth (rho = - 0.417; P = .001) and RD-PV [E-Peak] (rho = - 0.361; P = .007). We achieved a high accuracy in predicting CPAP failure (AUC = 95%; 95% CI, 89-100%) by integrating gender, SF ratio, and RD-PV [E-Peak] at the restricted, multivariate analysis.Conclusions: SF ratio and RD-PV, as measured by pulsed-wave Tissue Doppler, may help physicians to improve their confidence in optimizing therapeutic options in preterm infants with RDS. What is Known: • Continuous positive airway pressure is the recommended first-line treatment for respiratory distress syndrome in preterm infants, but failure rates remain unacceptably high. • Choosing the optimal treatment in terms of non-invasive ventilation effectiveness and timeliness of surfactant administration for these patients is often challenging, also due to our inability to identify a worsening respiratory failure. What is New: • The integration of oxygen saturation, as measured by SpO2/FiO2, with right diaphragm peak motion velocities, as measured by pulsed-wave tissue Doppler, allows for high prediction accuracy of non-invasive ventilation support failure in premature infants at risk of respiratory distress syndrome. • These measurements may help physicians in providing optimal supportive therapy for these patients.

Effects of Positioning on Cough Peak Flow and Muscular Electromyographic Activation in Duchenne Muscular Dystrophy.

Advanced stages of Duchenne muscular dystrophy (DMD) result in muscle weakness and the inability to generate an effective cough. Several factors influence the effectiveness of cough in patients with DMD. The aim of this study was to assess whether differences in positioning affect cough peak flow (CPF) and muscular electromyographic activation in subjects with DMD compared with paired healthy subjects. Optoelectronic plethysmography and surface electromyography were used to assess chest wall volumes, chest wall inspiratory capacity, CPF, breathing pattern, and electromyographic activity of sternocleidomastoid, scalene, rectus abdominis, and external oblique muscles during inspiratory and expiratory cough phases in the supine position, supine position with headrest raised at 45°, and sitting with back support at 80° in 12 subjects with DMD and 12 healthy subjects. Subjects with DMD had lower CPF (P < .01) in comparison to control subjects in all positions; the DMD group also exhibited lower CPF (P = .045) in the supine position versus 80°. Moreover, the relative volume contributions of the rib cage and abdominal compartments to tidal volume modified significantly with posture. The electromyographic activity during inspiratory and expiratory cough phases was lower in subjects with DMD compared to healthy subjects for all evaluated muscles (P < .05), but no significant differences were observed with posture change. In subjects with DMD, posture influenced CPF and the relative contribution of the rib cage and abdominal compartments to tidal volume. However, muscular electromyographic activation was not influenced by posture in subjects with DMD and healthy subjects.

The carotid bodies exercise control over active expiration but not peak performance during high-intensity treadmill running.

The carotid bodies exercise control over active expiration but not peak performance during high-intensity treadmill running.

Effect of Nitric Oxide Delivery Device on Tidal Volume Accuracy During Mechanical Ventilation at Small Tidal Volumes.

Inhaled nitric oxide (INO) is used in infants as a therapy for elevated pulmonary vascular resistance. When INO is delivered at low tidal volumes, displayed inspiratory and expiratory volumes vary widely. We hypothesize that volume is removed by the sampling line during the ventilation cycle, and this results in a net volume loss at low tidal volumes. This study aimed to measure the volumes delivered and to assess the accuracy of displayed ventilator values using a test lung. A test lung was connected to a ventilator and an INO delivery system. All tests were performed with stable mode settings across volumes of 18, 30, 42, and 60 mL. Flow measured with a pneumotachometer attached between the test lung and the circuit assessed the percent error between inspiratory and expiratory volumes measured by the pneumotachometer measured and displayed on the ventilator under various INO/sample line conditions to determine where and how much volume was being displaced. Displayed and measured inspiratory volumes had small variations between the INO/sample line conditions and baseline. However, expiratory volumes, with the sample line connected, exhibited large percent error values that increased (-14, -20, -27, and -34) as tidal volume decreased (60, 42, 30, and 18 mL) and error was significantly larger compared to baseline in all tidal volumes (P < .01) with and without INO delivery. We concluded that inspiratory volumes were not affected by INO delivery, but additional removal of volume in the expiratory phase of the breath cycle by the sampling line results in a large error in the displayed expiratory volume.

Investigation of airflow field in the upper airway under unsteady respiration pattern using large eddy simulation method

In this paper, the airflow field in the upper airway under unsteady respiration process is predicted using large eddy simulation. The geometrical model is created by combining a popular cast-based mouth–throat model with tracheo-bronchial airways modeled with a trumpet-shaped conduit. The respiration process is simulated by sinusoidal displacing the bottom surface of the geometrical model. Large eddy simulation with dynamic sub-grid scale model is adopted for modeling the turbulent flow via a commercial CFD software, Converge. This study has found that (1) the secondary vortices in the mouth cavity are much more complex considering the lung expansion than setting the quasi-steady inspiration flow at the mouth-inlet; (2) the properties of secondary vortices in the trachea are not evidently different at the same Reynolds number at the accelerating and decelerating inspiration phases; (3) the reversed pharynx jet as well as recirculation zone is much unsteadier at the accelerating expiration phase than decelerating expiration phase for the same Reynolds number. We conclude that the properties of airflow structures are highly impacted by the respiration pattern and more investigations should be conducted, particularly, on the airflow structures during expiration phase for further understanding the properties of flow field.

Differences Between Central Airway Obstruction and Chronic Obstructive Pulmonary Disease Detected with the Forced Oscillation Technique.

BackgroundObstructive ventilatory disturbances occur in both chronic obstructive pulmonary disease (COPD), a typical disease representative of peripheral airway obstruction, and central airway obstruction (CAO). Pulmonary function tests (PFTs), which depend on patient effort, are traditionally used to evaluate lung function. The forced oscillation technique (FOT) is an effort-independent method for examining lung function during tidal breathing. The FOT is used universally to assess respiratory function in patients with COPD. Several studies have measured FOT to assess ventilatory disturbances in CAO. The results showed that FOT measurements in patients with CAO were similar to those reported in patients with COPD. However, no studies have compared FOT measurements directly between CAO and COPD. The aim of this study was to identify differences in ventilatory disturbances between peripheral and central airway obstructions in COPD and CAO, before patients received pharmacological therapy or bronchoscopic interventions, respectively.Patients and MethodsWe retrospectively included 16 patients with CAO (10 cases of tracheal obstruction and 6 cases of bronchial obstruction) and 75 treatment-naïve patients with COPD (60 cases in Global Initiative for Chronic Obstructive Lung Disease [GOLD] stage II and 15 cases in GOLD stage III) that were admitted from December 2013 to May 2017. Prior to treatment, patients were examined with the FOT and PFTs.ResultsAll parameters measured with the FOT in the inspiratory phase were significantly worse in patients with CAO than in patients with COPD. The PFTs showed that the CAO group had a significantly lower peak expiratory flow rate. In the airway wall thickening phenotype of COPD, a difference between the inspiratory and expiratory phases of the resonance frequency (ΔFres) was the best indicator for distinguishing between peripheral and central airway obstructions.ConclusionThis study compared differences between CAO and COPD (mainly GOLD stage II). We found that the FOT measurement, ΔFres, was the optimal indicator of the difference between the airway wall thickening COPD phenotype and CAO. Thus, the difference might be due to mechanical changes that occur in COPD with airway wall thickening.

Expiratory airflow obstruction due to tracheostomy tube: A spirometric study in 50 patients

Tracheostomy is commonly used in intensive care units and in head and neck departments. Airway obstruction due to occluded cuffless tracheostomy tubes themselves remains unknown, although capping trials are commonly used before decannulation. The aim of this study was to evaluate the extent to which airway obstruction can be caused by occluded cuffless tubes in patients who underwent head and neck surgery. Prospective Research Outcome. University teaching hospital. Fifty patients requiring transient tracheostomy after head and neck surgery. A flow-volume loop (FVL) through the mouth using a portable spirometer, with the occluded fenestrated cuffless tube, was measured before and immediately after decannulation, by obstructing the orifice of tracheostomy tube. The measurement of FVL recorded the forced vital capacity (FVC), forced expiratory volume in 1second (FEV1 ), peak expiratory flow (PEF), forced expiratory flow at 50% of FVC, peak inspiratory flow (PIF) and forced inspiratory flow at 50% of FVC. A statistically significant difference between all spirometric parameters was found. Mean PEF and PIF, respectively, increased from 2.8 to 4.5L/s (P<.0001) and 2.3 to 2.7L/s (P<.01) before and after decannulation, with a strong positive correlation (r=0.7; P<.05). A mean expiratory (34%) and inspiratory (9%) airflow reduction was observed due to cannula. Occluded cuffless tracheostomy tubes cause a dramatic airflow obstruction, mainly in the expiratory phase of FVL. This should be taken into account during capping trials.

Correspondence between Capnovolumetric and Conventional Lung Function Parameters in the Diagnosis of Obstructive Airway Diseases

Background: Capnovolumetry is of interest as a method for the diagnosis of obstructive airway diseases, requiring little cooperation from the patient. Objective: To help in the interpretation of capnovolumetric parameters, we aimed to identify their correspondence to conventional lung function indices. Methods: We studied 978 patients from a diagnostic study with complete functional data and the clinical diagnosis of asthma, chronic obstructive pulmonary disease (COPD), or no respiratory disease. Using path analysis, four capnovolumetric parameters (slope of expiratory phase 3, ratio of slopes of phases 3 and 2, volume of phase 2, and the ratio area/volume of phase 3) previously identified as predictors of airway obstruction in terms of spirometry and body ple­thysmography, were analyzed regarding their relationship to each other and the diagnostic categories of asthma or COPD versus control, or obstruction versus no obstruction. We then identified four lung function parameters showing relationships as much as possible isomorphic to those between capnovolumetric parameters. Results: The four capnovolumetric parameters were related to COPD and obstruction via both direct and indirect influences, but only two of them to asthma. Regarding the correspondence to lung function parameters, the slope of expiratory phase 3 corresponded best to the ratio of residual volume to total lung capacity, the ratio of slopes of phases 3 and 2 to forced expiratory volume in 1 s, the volume of phase 2 to forced expired flow at 50% of vital capacity, and the ratio area/volume of phase 3 to forced vital capacity. Conclusions: Our results indicated an intricate relationship of capnovolumetric parameters to each other and to airway obstruction, asthma, or COPD. The correspondence to conventional lung function measures seemed to reflect the entities lung hyperinflation, overall ventilatory impairment, bronchoconstriction, and ventilated lung volume, in that order. These findings might be helpful for clinicians in the interpretation of capnovolumetry.

Optogenetic stimulation of respiratory related neurons modulates swallow and swallow‐breathing coordination

Swallow and breathing are tightly coordinated behaviors in which disruption of this coordination leads to aspiration pneumonia, the leading cause of death in many adult and pediatric diseases. Little is known about the neural coordination of these two behaviors. Previous work in the respiratory column has shown activity in swallow‐related and breathing‐related neurons, as well as neurons active during both swallow and breathing, suggesting coordination at a central network level. Evidence in the intermediate reticular nucleus (postinspiratory Complex, PiCo) suggest involvement in swallow behavior but not swallow‐breathing coordination. We hypothesize that swallow predominately occurs during the expiratory phase of breathing due to inspiratory related neurons suppressing swallow activity. Thus, inhibition of excitatory neurons within the Pre‐Bötzinger complex will increase swallow excitability, while exciting glutamatergic neurons within this network will have the opposite effect. To evaluate swallow circuitry and its coordination with respiratory related networks we use optogenetic approaches to manipulate the activity of inhibitory (Vgat‐Cre) and excitatory (Dbx1‐ERT2Cre, Vglut2‐Cre) neuron populations within the ventral respiratory centers as well as modulation of PiCo (ChAT‐Cre) in the presence of light stimulation. Optogenetic activation (blue laser, 447nm) of Dbx1 cells was performed in adult Dbx1‐ERT2Cre/Ai32(ChR2) mice after exposing the ventral surface of the brainstem in vivo, and placing bilateral glass fiber optics over the ventral surface in the region of the Pre‐Bötzinger complex. Swallow activity was measured by monopolar suction electrodes of the hypoglossal (XII) and vagus (X) nerves as well as cervical sympathetic nerve (cSNA). Phases of breathing was measured via monopolar electromyogram (EMG) of the diaphragm and swallow was stimulated orally by injection of 0.1cc of 2.5% citric acid water. Our preliminary data suggest that stimulating Dbx1 cells decreased the frequency and duration of swallows. Interestingly, we observed in the presence of light stimulation multiple swallow attempts (oral phase without the pharyngeal phase) resulting in hyoid elevation but failure to induce pharyngeal phase. The average swallow in the absence of light stimulation had a duration of 1025ms whereas swallow during light stimulation was 809ms. We believe that activation of Dbx1 neurons in the Pre‐Bötzinger complex suppresses swallow activity and decouples oral and pharyngeal phases of swallow.Support or Funding InformationNIH: P01 HL090554, R01 HL144801 and R01 HL126523

A Review on Cough Augmentation Techniques: Assisted Inspiration, Assisted Expiration and Their Combination

Cough is an important mechanism of airway clearance. In patients who present weak and ineffective cough, augmentation techniques aim to assist or simulate the maneuver. These techniques target different phases of the cough cycle, mainly the inspiratory and expiratory phases, through assisted inspiration, assisted expiration and their combination. They include the manual hyperinflation, ventilator hyperinflation, glossopharyngeal breathing, manually assisted cough and mechanical insufflator-exsufflator, each applied individually or in different combinations. The aim of this review is to investigate the effectiveness and safety of cough augmentation techniques. Findings support that all commonly used techniques can theoretically improve airway clearance, as they generate higher cough peak flows compared to unassisted cough. Still, the studies assessing cough augmentation present considerable limitations and the direct comparison of different techniques is challenging. Current evidence indicate that cough peak flow shows higher increase with the combination of assisted inspiration and expiration, and improvement is greater in patients with lower unassisted values. Associated adverse events are infrequent.

A Systematic Review of the Influence of Bolus Characteristics on Respiratory Measures in Healthy Swallowing.

There have been a number of studies on the effect of bolus volume, consistency, texture, temperature and taste on the oropharyngeal swallowing physiology. However, its influence on the respiratory function associated with swallow is not well understood. This study aimed at systematically analysing and documenting the prevailing research literature on respiratory functions before, during, and after healthy swallows of boluses with varied characteristics. The PRISMA guidelines were followed for retrieval of relevant research. From among the 48,329 reports screened for inclusion criteria, 25 articles were included for data extraction. Each of these reports was evaluated for its design, methodology and reporting quality and also the level of evidence provided by them. The results revealed that the scientific evidence in this regard was restricted to level II. Majority of the studies included considered bolus volume as the variable than bolus consistency, taste or temperature. Expiratory phase was preferred surrounding the apnea irrespective of volume, consistency or taste but changed with temperature variations across age groups. The reports are equivocal on the duration of respiratory apnea, and length of respiratory cycles before and after the apnea. The temporal coordination of pharyngeal swallow events was found to be independent of bolus volume. This review concluded that bolus characteristics have differential effects on the respiratory functions during swallow beyond a 'central sensory threshold' level. Objective standardization of bolus characteristics may be the immediate requirement for generalization of future research findings in this direction.

A Magnetic Resonance-Compatible Wearable Device Based on Functionalized Fiber Optic Sensor for Respiratory Monitoring

There is a growing demand of comfortable and unobtrusive wearable systems for monitoring a variety of physiological parameters and in particular the respiratory frequency ( f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> ). The most popular techniques for f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> monitoring cannot be used in several clinical applications and in unstructured environment. These issues have fostered a dramatic growth of interest for wearable systems devoted to monitor f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> . In this arena, fiber Bragg grating (FBG) sensors have gained due to a variety of benefits. In this work, we designed and fabricated an FBG-based wearable device for f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> monitoring from the nasal airflow. The proposed design does not require a mask to improve the comfortability and acceptability of the system. The sensing element was functionalized by a hygroscopic coating material to make the FBG sensitive to relative humidity changes. This feature allows calculating f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> starting from the discrimination between the inspiration and expiration phases. A pilot study on 6 volunteers was designed to assess the system during three different breathing stages (i.e., slow, normal and fast breathing). Results showed high performance of the proposed wearable device in detecting mean and breath-by-breath f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> values (i.e., mean percentage errors ≤ 2.29 % and bias ≤ 0.31 breaths per minute) during slow breathing, normal breathing, and fast breathing.

Effect of expiratory phase for radiographic detection of left heart enlargement in dogs with mitral regurgitation.

Radiography is a standard diagnostic test for characterizing left heart enlargement in dogs however limited information is available on the effects of respiratory phases. This prospective and retrospective method comparison study investigated the respiratory effect on the size and shape of the left heart in dogs to determine the usefulness of expiratory radiographs to detect enlargements in the left atrium (LA) and left ventricle (LV). Thoracic radiographs taken at full inspiration and expiration were evaluated in 20 normal beagles and 100 dogs diagnosed with mitral regurgitation (MR). Vertebral heart score (VHS), vertebral left atrial size, elevation of the carina, and dorsal bulging of LA on lateral view and lateral bulging of the left auricular appendage and LV on ventrodorsal view were assessed. In normal dogs, there were no significant differences in the evaluative factors between inspiration and expiration. In dogs with MR, VHS did not change according to respiration. However, bulging of the LA, left auricular appendage, and LV had sharp margin during expiration compared with inspiration. The expiratory radiographic finding of LA bulging had a higher correlation with the LA to aorta ratio compared with LA bulging in the inspiratory radiography. Using a LA to aorta echocardiographic ratio greater than 1.5 as the gold standard, the radiographic sensitivity for LA enlargement was higher during expiration than inspiration. These findings of our study indicated that expiratory radiography can be helpful to support the detection of left heart enlargement, although it can overestimate LA enlargement in dogs with MR.

Effects of Manual Rib Cage Compressions on Mucus Clearance in Mechanically Ventilated Pigs.

Manual rib cage compression is a chest physiotherapy technique routinely used in clinical practice. However, scientific evidence remains scarce on the effects of manual rib cage compression on airway clearance and oxygenation in mechanically ventilated patients. Anesthetized pigs were intubated via the trachea and mechanically ventilated. To create atelectasis, artificial mucus was infused into the airway. Each pig was randomly assigned to 1 of 2 groups: closed suctioning alone (control group, 7 pigs), or manual rib cage compression combined with closed suctioning (manual rib cage compression group, 8 pigs). Hard and brief rib cage compression synchronized with early expiratory phase was tested. Mucus clearance and oxygenation were assessed after the intervention. Sequential changes of hemodynamics were assessed after the intervention. During hard manual rib cage compression, the mean ± SD peak expiratory flow increased to 44 ± 7 L/min compared with 31 ± 7 L/min without treatment (P < .001). Manual rib cage compression combined with endotracheal suctioning increased mucus clearance compared with closed suctioning alone (mucus amounts, 5.5 [3.4-9.4] g vs 0.7 [0.5-2.0] g; P = .004); however, it did not improve gas exchange and radiologic findings. There were no significant differences in hemodynamic variables between the 2 groups. Our findings indicated that hard and brief manual rib cage compression combined with closed suctioning was safe and led to improvement of mucus clearance; however, no effectiveness was confirmed with regard to oxygenation and ventilation.