Mechanical ventilation has, since its introduction into clinical practice, undergone a major evolution from controlled ventilation to diverse modes of assisted ventilation. Conventional mechanical ventilators depend on flow sensors and pneumatic pressure and controllers to complete the respiratory cycle. Neurally adjusted ventilatory assist (NAVA) is a new form of assisted ventilation in recent years, which monitors the electrical activity of the diaphragm (EAdi) to provide an appropriately level of pressure support. And EAdi is the best available signal to sense central respiratory drive and trigger ventilatory assist. Unlike other ventilation modes, NAVA breathing instructions come from the center. Therefore, NAVA have the synchronous nature of the breaths and the patient-adjusted nature of the support. Compared with traditional ventilation mode, NAVA can efficiently unload respiratory muscles, relieve the risk of ventilator-induced lung injury (VILI), improve patient-ventilator coordination, enhance gas exchange, increase the success rate of weaning, etc. This article reviews the research progress of NAVA in order to provide theoretical guidance for clinical applications.
Humans ; Interactive Ventilatory Support ; Respiration, Artificial ; Positive-Pressure Respiration ; Diaphragm/physiology* ; Respiratory Muscles/physiology*

Animals ; Diaphragm ; physiopathology ; Electrophysiological Phenomena ; physiology ; Hypoxia ; physiopathology ; Male ; Rats ; Rats, Wistar ; Sleep Apnea Syndromes ; physiopathology

Diaphragmatic electromyographic (EMGdi) signal is a weak biological signal, which contains some significant physiological information of our body respiration system and is susceptible to strong electrocardiography (ECG) signal interference. Based on wavelet transform and theory of information entropy, a new wavelet energy entropy threshold algorithm to remove ECG interference is proposed in this paper. On the base of analysis of wavelet coefficients of each scale, the method sees the information of each scale as a single signal source, equalizes it byzones, and then divides the energy entropy into two categories (i. e., high energy entropy and low energy entropy) through the distribution characteristics of energy entropy of each zone to conduct absolute mean value threshold. In addition, the denoised signal is reconstructed by wavelet coefficients processed. The experimental results showed that the method removed the ECG signal in EMGdi effectively and reserved the available characteristics of EMGdi better.
Algorithms ; Artifacts ; Diaphragm ; physiology ; Electrocardiography ; methods ; Electromyography ; methods ; Entropy ; Humans ; Signal Processing, Computer-Assisted ; Wavelet Analysis

PURPOSE: Studies on the physiology of the transposed stomach as an esophageal substitute in the form of a gastric pull-up or a gastric tube in children are limited. We conducted a study of motility and the pH of gastric esophageal substitutes using manometry and 24-hour pH measurements in 10 such patients. METHODS: Manometry and 24 hour pH studies were performed on 10 children aged 24 to 55 months who had undergone gastric esophageal replacement. RESULTS: Six gastric tubes (4, isoperistaltic; 2, reverse gastric tubes) and 4 gastric pull-ups were studied. Two gastric tubes and 4 gastric pull-ups were transhiatal. Four gastric tubes were retrosternal. The mean of the lowest pH at the midpoint of the substitute was 4.0 (range, 2.8–5.0) and in the stomach remaining below the diaphragm was 3.3 (range, 1.9–4.2). In both types of substitute, the difference between the peak and the nadir pH recorded in the intra-thoracic and the sub-diaphragmatic portion of the stomach was statistically significant (p < 0.05), with the pH in the portion below the diaphragm being lower. The lowest pH values in the substitute and in the remnant stomach were noted mainly in the evening hours whereas the highest pH was noted mainly in the morning hours. All the cases showed a simultaneous rise in the intra-cavitatory pressure along the substitute while swallowing. CONCLUSION: The study suggested a normal gastric circadian rhythm in the gastric esophageal substitute. Mass contractions occurred in response to swallowing. The substitute may be able to effectively clear contents.
Child* ; Circadian Rhythm ; Deglutition ; Diaphragm ; Gastric Stump ; Humans ; Hydrogen-Ion Concentration* ; Manometry* ; Physiology ; Stomach

OBJECTIVETo observe the effects of neurally adjusted ventilatory assist (NAVA) on the patient-ventilator synchrony, gas exchange, and ventilatory parameters in preterm infants with respiratory distress syndrome (RDS) during mechanical ventilation.

METHODSTen preterm infants with RDS received mechanical ventilation in NAVA mode for 60 minutes and in synchronized intermittent mandatory ventilation (SIMV) mode for 60 minutes, and the two modes were given in a random order. The vital signs, patient-ventilator synchrony, blood gas values, and ventilatory parameters were compared between the two ventilation modes.

RESULTSInspiratory trigger delay was significantly shorter with NAVA than with SIMV (P<0.05). There were no significant differences in arterial pH, PaCO2, PaO2 and PaO2/FiO2 between the two modes. The spontaneous respiratory rate, peak inspiratory pressure (PIP), electrical activity of the diaphragm and work of breathing were significantly lower in NAVA than in SIMV (P<0.05).

CONCLUSIONSCompared with SIMV, NAVA appears to improve patient-ventilator synchrony, decrease PIP, and reduce diaphragmatic muscle load and work of breathing in preterm infants with RDS during mechanical ventilation.

Diaphragm ; physiology ; Female ; Humans ; Infant, Newborn ; Infant, Premature ; Male ; Respiration, Artificial ; methods ; Respiratory Center ; physiology ; Respiratory Distress Syndrome, Newborn ; therapy

Background: Neural respiratory drive (NRD) using diaphragm electromyography through an invasive transesophageal multi-electrode catheter can be used as a feasible clinical physiological parameter in patients with chronic obstructive pulmonary disease (COPD) to provide useful information on the treatment response. However, it remains unknown whether the surface diaphragm electromyogram (EMGdi) could be used to identify the deterioration of clinical symptoms and to predict the necessity of hospitalization in acute exacerbation of COPD (AECOPD) patients. Methods: COPD patients visiting the outpatient department due to acute exacerbation were enrolled in this study. All patients who were subjected to EMGdi and classical parameters such as spirometry parameters, arterial blood gas analysis, COPD assessment test (CAT) score, and the modified early warning score (MEWS) in outpatient department, would be treated effectively in the outpatient or inpatient settings according to the Global Initiative for Chronic Obstructive Lung Disease guideline. When the acute exacerbation of the patients was managed, all the examination above would be repeated. Results: We compared the relationships of admission-to-discharge changes (Δ) in the normalized value of the EMGdi, including the change of the percentage of maximal EMGdi (ΔEMGdi%max) and the change of the ratio of minute ventilation to the percentage of maximal EMGdi (ΔVE/EMGdi%max) with the changes of classical parameters. There was a significant positive association between ΔEMGdi%max and ΔCAT, ΔPaCO, and ΔpH. The change (Δ) of EMGdi%max was negatively correlated with ΔPaO/FiOin the course of the treatment of AECOPD. Compared with the classical parameters including forced expiratory volume in 1 s, MEWS, PaO/FiO, the EMGdi%max (odds ratio 1.143, 95% confidence interval 1.004-1.300) has a higher sensitivity when detecting the early exacerbation and enables to predict the admission of hospital in the whole cohort. Conclusions The changes of surface EMGdi parameters had a direct correlation with classical measures in the whole cohort of AECOPD. The measurement of NRD by surface EMGdi represents a practical physiological biomarker, which may be helpful in detecting patients who should be hospitalized timely.
Diaphragm ; physiopathology ; Electromyography ; methods ; Forced Expiratory Volume ; physiology ; Hospitalization ; Humans ; Pulmonary Disease, Chronic Obstructive ; metabolism ; physiopathology ; Spirometry ; Vital Capacity ; physiology

In order to improve synchrony between a ventilator and its patient, a new method for triggering a ventilator based on diaphragmatic electromyogram (EMG) is introduced. The methods to extract and process diaphragmatic EMG signals are studied. It has been shown that the characteristic parameters of a respiration activity, such as inspiratory beginning point, expiratory beginning point and respiration period, can be detected from diaphragmatic EMG envelop instead of traditional flux curve. A new parameter, designated as diaphragmatic "Intensity of EMG" for short "IEMG", is defined. Repeat respiration tests have disclosed that there is relatively high correlation between the diaphragmatic IEMG curve and its corresponding cubage curve. These results primarily demonstrate that the new synchronization method may be feasible.
Diaphragm ; physiology ; Electromyography ; Humans ; Positive-Pressure Respiration ; methods ; Respiration ; Respiration, Artificial ; methods ; Respiratory Insufficiency ; therapy ; Respiratory Muscles ; physiology ; Work of Breathing ; physiology

Breathing motion is a rule-based motion. The traditional breathing motion is described by mathematical model which can not reflect the different properties of different patients or the different breathing periods of the same patient. So, it can not satisfy the needs of the real-time and accurate analysis. Accordingly, in this paper is proposed a method to establish the breathing model through tracking the cone beam CT images which are gained when the patient is breathing freely. The model obtained by the proposed method is similar to the traditional model, which verifies the feasibility and effectiveness of the proposed method. Simultaneously, the proposed method has "real-time" and "accurate" properties, which make it valuable in clinical application.
Cone-Beam Computed Tomography ; Diaphragm ; diagnostic imaging ; physiology ; Humans ; Models, Biological ; Movement ; Radiographic Image Interpretation, Computer-Assisted ; methods ; Respiration

AIMTo study the possibility that responses of fever and discharge of neurons in PVN to intraperitoneal administration of LPS are mediated by vagal afferents.

METHODSRectal temperature of rat was detected by digital temperature detecting instrument. Glass micropipette placed in PVN was used to record unit discharges of neurons in it, before and after LPS was injected into PVN in normal rats and vagotomy rats.

RESULTSThe rectal temperature change value in vagotomy LPS group was significantly decreased compared with that in sham LPS group, and there was striking difference between them (P < 0.05). The discharges of neurons in PVN was increased in the normal rat in response to LPS. The discharges of neurons in PVN had no significant change in the vagotomy rats in response to LPS.

CONCLUSIONThe results indicate that vagus nerve may be one of the pathways of peripheral LPS signal communicating to CNS.

Animals ; Diaphragm ; innervation ; Fever ; chemically induced ; physiopathology ; Lipopolysaccharides ; Male ; Neurons ; physiology ; Paraventricular Hypothalamic Nucleus ; physiopathology ; Rats ; Rats, Wistar ; Vagotomy, Truncal

Animals ; Calcium ; metabolism ; Diaphragm ; physiology ; ultrastructure ; Male ; Muscle Contraction ; Rats ; Rats, Sprague-Dawley ; Respiration, Artificial ; Sarcoplasmic Reticulum ; metabolism