Measurement of thoraco-abdominal synchrony using respiratory inductance plethysmography: technical aspects and a proposal to overcome its limitations.

BACKGROUND: Thoraco-abdominal asynchrony (TAA) is usually assessed by respiratory inductance plethysmography. The main parameter used for its assessment is the calculation of the phase angle based on Lissajous plots. However, there are some mathematical limitations to its use. RESEARCH DESIGN AND METHODS: Sequences of five breaths were selected from a) normal subjects, b) COPD patients, both at rest and during exercise, and c) patients with obstructive apnea syndrome. Automated analysis was performed calculating phase angle, loop rotation (clockwise or counterclockwise), global phase delay and loop area. TAA severity was estimated quantitatively and in subgroups. RESULTS: 2290 cycles were analyzed (55% clockwise rotation). Phase angle ranged from -86.90 to + 88.4 degrees, while global phase delay ranged from -179.75 to + 178.54. Despite a good correlation with global phase delay (p < 0.01, ANOVA test), phase angle and loop area were not able to correctly classify breaths with severe deviation and paradoxical movements (p=ns, Bonferroni post hoc test). CONCLUSIONS: Global phase delay covers the whole spectrum of TAA situations in a single value. It may be a relevant parameter for diagnosis and follow-up of clinical conditions leading to TAA. CLINICAL TRIAL REGISTRATION: The trial from which the traces were obtained was registered at ClinicalTrials.gov ;(identifier: NCT04597606).

Ventilators, Settings, Autotitration Algorithms.

The choice of a ventilator model for a single patient is usually based on parameters such as size (portability), presence or absence of battery and ventilatory modes. However, there are many details within each ventilator model about triggering, pressurisation or autotitration algorithms that may go unnoticed, but may be important or may justify some drawbacks that may occur during their use in individual patients. This review is intended to emphasize these differences. Guidance is also provided on the operation of autotitration algorithms, in which the ventilator is able to take decisions based on a measured or estimated parameter. It is important to know how they work and their potential sources of error. Current evidence on their use is also provided.

Higher mortality and intubation rate in COVID-19 patients treated with noninvasive ventilation compared with high-flow oxygen or CPAP.

The effectiveness of noninvasive respiratory support in severe COVID-19 patients is still controversial. We aimed to compare the outcome of patients with COVID-19 pneumonia and hypoxemic respiratory failure treated with high-flow oxygen administered via nasal cannula (HFNC), continuous positive airway pressure (CPAP) or noninvasive ventilation (NIV), initiated outside the intensive care unit (ICU) in 10 university hospitals in Catalonia, Spain. We recruited 367 consecutive patients aged ≥ 18 years who were treated with HFNC (155, 42.2%), CPAP (133, 36.2%) or NIV (79, 21.5%). The main outcome was intubation or death at 28 days after respiratory support initiation. After adjusting for relevant covariates and taking patients treated with HFNC as reference, treatment with NIV showed a higher risk of intubation or death (hazard ratio 2.01; 95% confidence interval 1.32-3.08), while treatment with CPAP did not show differences (0.97; 0.63-1.50). In the context of the pandemic and outside the intensive care unit setting, noninvasive ventilation for the treatment of moderate to severe hypoxemic acute respiratory failure secondary to COVID-19 resulted in higher mortality or intubation rate at 28 days than high-flow oxygen or CPAP. This finding may help physicians to choose the best noninvasive respiratory support treatment in these patients.Clinicaltrials.gov identifier: NCT04668196.

Does the Efficacy of High Intensity Ventilation in Stable COPD Depend on the Ventilator Model? A Bench-to-Bedside Study.

PURPOSE: The European Task Force for chronic non-invasive ventilation in stable COPD recommends the use of high pressure-support (PS) level to maximize the decrease in PaCO2. It is possible that the ventilator model can influence the need for higher or lower pressure levels. RESEARCH QUESTION: To determine the differences between ventilators in a bench model with an increased inspiratory demand; and to compare the degree of muscular unloading measured by parasternal electromyogram (EMGpara) provided by the different ventilators in real patients with stable COPD. PATIENTS AND METHODS: Bench: four levels of increasing progressive effort were programmed. The response of nine ventilators to four levels of PS and EPAP of 5 cm H2O was studied. The pressure-time product was determined at 300 and 500 msec (PTP 300/500). CLINICAL STUDY: The ventilators were divided into two groups, based on the result of the bench test. Severe COPD patients with non-invasive ventilation (NIV) were studied, randomly comparing the performance of one ventilator from each group. Muscle unloading was measured by the decrease in EMGpara from its baseline value. RESULTS: There were significant differences in PTP 300 and PTP 500 in the bench study. Based on these results, home ventilators were classified into two groups; group 1 included four models with higher PTP 300. Ten COPD patients were recruited for the clinical study. Group 1 ventilators showed greater muscle unloading at the same PS than group 2. CONCLUSION: The scale of pressure support in NIV for high intensity ventilation may be influenced by the ventilator model. CLINICAL TRIALSGOV: NCT03373175.

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.

Integrated 3D printing solution to mitigate shortages of airway consumables and personal protective equipment during the COVID-19 pandemic.

BACKGROUND: To cope with shortages of equipment during the COVID-19 pandemic, we established a nonprofit end-to-end system to identify, validate, regulate, manufacture, and distribute 3D-printed medical equipment. Here we describe the local and global impact of this system. METHODS: Together with critical care experts, we identified potentially lacking medical equipment and proposed solutions based on 3D printing. Validation was based on the ISO 13485 quality standard for the manufacturing of customized medical devices. We posted the design files for each device on our website together with their technical and printing specifications and created a supply chain so that hospitals from our region could request them. We analyzed the number/type of items, petitioners, manufacturers, and catalogue views. RESULTS: Among 33 devices analyzed, 26 (78·8%) were validated. Of these, 23 (88·5%) were airway consumables and 3 (11·5%) were personal protective equipment. Orders came from 19 (76%) hospitals and 6 (24%) other healthcare institutions. Peak production was reached 10 days after the catalogue was published. A total of 22,135 items were manufactured by 59 companies in 18 sectors; 19,212 items were distributed to requesting sites during the busiest days of the pandemic. Our online catalogue was also viewed by 27,861 individuals from 113 countries. CONCLUSIONS: 3D printing helped mitigate shortages of medical devices due to problems in the global supply chain.

Relationship between the respiratory microbiome and the severity of airflow limitation, history of exacerbations and circulating eosinophils in COPD patients.

BACKGROUND: The respiratory microbiome is altered in COPD patients but its relationship with core components of the disease, such as the severity of airflow limitation, the frequency of exacerbations or the circulating levels of eosinophils, is unclear. METHODS: Cross-sectional study comprising 72 clinically stable COPD patients (mean age 68 [SD 7.9] years; FEV1 48.7 [SD 20.1]% of reference) who provided spontaneous sputum samples for 16S rRNA gene amplification and sequencing. The microbiome composition was analysed with QIIME. RESULTS: We observed that: (1) more severe airflow limitation was associated with reduced relative abundance (RA) of Treponema and an increase in Pseudomonas; (2) patients with ≥2 exacerbations the previous year showed a significantly different bacterial community with respect to non-exacerbators (p = 0.014), with changes in 13 genera, including an increase of Pseudomonas, and finally, (3) peripheral eosinophils levels ≥2% were associated with more diverse microbiome [Chao1 224.51 (74.88) vs 277.39 (78.92) p = 0.006; Shannon 3.94 (1.05) vs 4.54 (1.06) p = 0.020], and a significant increase in the RAs of 20 genera. CONCLUSION: The respiratory microbiome in clinically stable COPD patients varies significantly according to the severity of airflow limitation, previous history of exacerbations and circulating eosinophils levels.

Titration of Mechanical Insufflation-Exsufflation Optimal Pressure Combinations in Neuromuscular Diseases by Flow/Pressure Waveform Analysis / Titulación de las combinaciones de presión óptima de insuflación-exuflación mecánica en las enfermedades neuromusculares mediante análisis de la onda de fujo/presión

Introduction: The aim of this study was to assess several air-pressure settings for MI-E to determine their effect on peak cough flow (PCF), and to compare the best pressures with those are more common used in the literature (±40cmH2O) in patients with neuromuscular disorders (NMD). Methods: Adults with NMD in whom MI-E was indicated were recruited. Assisted PCF was measured by an external pneumotachograph. The protocol included 9 PCF measures per patient: 1 baseline (non-assisted), 4 with increasing inspiratory pressures without negative pressure (10, 20, 30 and 40cmH2O or maximum tolerated), and then 4 adding expiratory pressures (-10, -20, -30 and -40cm H2O or maximum tolerated) with maximum inspiratory pressure previously achieved. Results: Twenty one patients were included, 61% with amyotrophic lateral sclerosis (ALS). Mean PCFs with recommended pressures (± 40 cmH2O) were lower than the scored in the individualized steps of the titration protocol (197.7 ± 67l/min vs 214.2 ± 60 l/min, p < 0.05). Regarding subgroups, mean PCFmax values in ALS patients with bulbar symptoms were significantly higher than those achieved with recommended pressures (163.6 ± 80 vs 189 ± 66l/min, p < 0.05). Conclusion: The PCFmax obtained with the protocol did not always match the recommended settings. It may be advisable to perform MI-E titration assessed by non-invasive PCF monitoring in patients with NMD, especially in ALS with bulbar involvement to improve the therapy detecting airway collapse induced by high pressures

Introducción: El objetivo del estudio fue evaluar varios ajustes de presión para insuflación-exuflación mecánica (IEM) para determinar su efecto sobre el flujo pico de tos (FPT), y comparar las mejores presiones con aquellas que son habitualmente utilizadas en la literatura (± 40 cmH2O) en pacientes con enfermedades neuromusculares (ENM). Métodos: Se reclutaron adultos con ENM en los que se indicó IEM. Se midió el FPT asistido mediante un neumotacógrafo externo, y se registraron las curvas de presión y flujo/tiempo. El protocolo incluía 9 medidas de FPT por paciente: una basal (no asistida), 4 con presiones inspiratorias crecientes sin presión negativa (10, 20, 30 y 40 cmH2O o máximo tolerado), y luego 4 presiones espiratorias (-10, -20, -30, -40 cmH2O o máxima tolerada) con la presión inspiratoria máxima conseguida. Resultados: Se incluyeron 21 pacientes, 61% con esclerosis lateral amiotrófica (ELA). Las altas presiones (>±35 cmH2O) lograron el mejor FPT solo en el 50% de los sujetos. Los FPT medios con presiones recomendadas de ± 40 cmH2O (197,7 ± 67 l/min) fueron más bajos que los conseguidos con presiones de titulación individualizadas con el protocolo (214,2 ± 60 l/min, p < 0,05). Con respecto a los subgrupos, los valores medios de FPT máximos en los pacientes con ELA con síntomas bulbares fueron significativamente mayores que los logrados con las presiones recomendadas (163,6±80 frente a 189 ± 66 l/min p < 0,05). Conclusión: El FPT máximo obtenido con el protocolo no siempre coincide con las presiones más altas. Puede ser aconsejable realizar una valoración de IEM evaluada mediante monitorización no invasiva de FPT en pacientes con ENM, especialmente en ELA con afectación bulbar, para mejorar la terapia que detecta el colapso de la vía aérea inducida por altas presiones

Basic Concepts for Tidal Volume and Leakage Estimation in Non-Invasive Ventilation.

Non-invasive ventilation (NIV) aims to maintain sufficient alveolar ventilation, improve pulmonary gas exchange, assist respiratory muscles, and decrease work of breathing. Monitoring variables such as leaks, tidal volume, and minute ventilation during therapy is crucial to assess the effectiveness of NIV. However, most of the time, leaks and tidal volume are not measured but estimated by NIV devices. Moreover, there are limited data for the accuracy and reliability of these estimations. Herein, we address some technical considerations for tidal volume and leakage estimation during NIV and its impact in clinical practice.

Titration of Mechanical Insufflation-Exsufflation Optimal Pressure Combinations in Neuromuscular Diseases by Flow/Pressure Waveform Analysis.

INTRODUCTION: The aim of this study was to assess several air-pressure settings for MI-E to determine their effect on peak cough flow (PCF), and to compare the best pressures with those are more common used in the literature (±40cmH2O) in patients with neuromuscular disorders (NMD). METHODS: Adults with NMD in whom MI-E was indicated were recruited. Assisted PCF was measured by an external pneumotachograph. The protocol included 9 PCF measures per patient: 1 baseline (non-assisted), 4 with increasing inspiratory pressures without negative pressure (10, 20, 30 and 40cmH2O or maximum tolerated), and then 4 adding expiratory pressures (-10, -20, -30 and -40cmH2O or maximum tolerated) with maximum inspiratory pressure previously achieved. RESULTS: Twenty one patients were included, 61% with amyotrophic lateral sclerosis (ALS). Mean PCFs with recommended pressures (±40cmH2O) were lower than the scored in the individualized steps of the titration protocol (197.7±67l/min vs 214.2±60l/min, p<0.05). Regarding subgroups, mean PCFmax values in ALS patients with bulbar symptoms were significantly higher than those achieved with recommended pressures (163.6±80 vs 189±66l/min, p<0.05). CONCLUSION: The PCFmax obtained with the protocol did not always match the recommended settings. It may be advisable to perform MI-E titration assessed by non-invasive PCF monitoring in patients with NMD, especially in ALS with bulbar involvement to improve the therapy detecting airway collapse induced by high pressures.