Respiratory monitoring is often required in experimental physiological and pharmacological studies in rodents. Currently, the mostly used techniques are direct measurement of airflow on intubated ...animals and whole body plethysmography.
Although the reliability of these methods has been broadly demonstrated, they also have several drawbacks such as invasiveness, high cost of use or confinement of the animals. Respiratory inductive plethysmography (RIP) is a non-invasive technique already used in medium-sized mammals that has not yet been evaluated in small rodents. The implementation of inductive plethysmography in rats represents an instrumental challenge because of the small inductances that are expected.
A rodent-specific RIP apparatus has been developed and compared to direct airflow measurement provided by a pneumotachograph (PNT) considered as the invasive gold standard for respiratory monitoring. The experiments were carried out on anesthetized rats artificially ventilated at different levels of tidal volumes (V
) covering the whole physiological range.
Based on the Euclidian distance between signals, this study shows that after calibration, signals from RIP fit at 93% with PNT values. The Bland and Altman plot evidences differences between RIP and PNT lower than 20% and the values obtained are highly correlated (R = 0.98, p < 0.001).
This study demonstrates that it is possible to design RIP systems suitable for measurement of tidal volumes and airflow in anesthetized rats. Further studies will now be focused on the validation in extended physiological conditions.
The simultaneous study of the cardiac and respiratory activities and their interactions is of great physiological and clinical interest. For this purpose, we want to investigate if respiratory ...inductive plethysmography (RIP) can be used for cardiac functional exploration. We propose a system, based on RIP technology and time-scale approaches of signal processing, for the extraction of cardiac information. This study focuses on the monitoring of blood volume shift due to heart beat, noted ▵Vtr_c and investigates RIP for the detection of ▵Vtr_c variations by comparison to stroke volume (SV) variations estimated by impedance cardiography (IMP). We proposed a specific respiratory protocol assumed to induce significant variations of the SV. Fifteen healthy volunteers in the seated and supine positions were asked to alternate rest respiration and maneuvers, consisting in blowing into a manometer. A multi-step treatment including a variant of empirical mode decomposition was applied on RIP signals to extract cardiac volume signals and estimate beat-to-beat ▵Vtr_c. These were averaged in quasi-stationary states at rest and during the respiratory maneuvers, and analysed in view of SV estimations from IMP signals simultaneously acquired. Correlation and statistical tests over the data show that RIP can be used to detect variations of the cardiac blood shift in healthy young subjects.
Swallowing disorders (or dysphagia) are common in the elderly and their prevalence is often underestimated. They may result in serious complications including dehydration, malnutrition, airway ...obstruction, aspiration pneumonia (infectious process) or pneumonitis (chemical injury caused by the inhalation of sterile gastric contents). Moreover the repercussions of dysphagia are not only physical but also emotional and social, leading to depression, altered quality of life, and social isolation. While some changes in swallowing may be a natural result of aging, dysphagia in the elderly is mainly due to central nervous system diseases such as stroke, parkinsonism, dementia, medications, local oral and oesophageal factors. To be effective, management requires a multidisciplinary team approach and a careful assessment of the patient's oropharyngeal anatomy and physiology, medical and nutritional status, cognition, language and behaviour. Clinical evaluation can be completed by a videofluoroscopic study which enables observation of bolus movement and movements of the oral cavity, pharynx and larynx throughout the swallow. The treatment depends on the underlying cause, extent of dysphagia and prognosis. Various categories of treatment are available, including compensatory strategies (postural changes and dietary modification), direct or indirect therapy techniques (swallow manoeuvres, medication and surgical procedures).
Based on the hypotheses that (1) a physiological organization exists inside each activity of daily life and (2) the pattern of evolution of physiological variables is characteristic of each activity, ...pattern changes should be detected on daily life physiological recordings. The present study aims at investigating whether a simple segmentation method can be set up to detect pattern changes on physiological recordings carried out during daily life. Heart and breathing rates and skin temperature have been non-invasively recorded in volunteers following scenarios made of “daily life” steps (13 records). An observer, undergoing the scenario, wrote down annotations during the recording time. Two segmentation procedures have been compared to the annotations, a visual inspection of the signals and an automatic program based on a trends detection algorithm applied to one physiological signal (skin temperature). The annotations resulted in a total number of 213 segments defined on the 13 records, the best visual inspection detected less segments (120) than the automatic program (194). If evaluated in terms of the number of correspondences between the times marks given by annotations and those resulting from both physiologically based segmentations, the automatic program was better than the visual inspection. The mean time lags between annotation and program time marks remain <60 s (the precision of annotation times marks). We conclude that physiological variables time series recorded in common life conditions exhibit different successive patterns that can be detected by a simple trends detection algorithm. Theses sequences are coherent with the corresponding annotated activity.
The purpose of this study was to prove the feasibility of 3D reconstructions of the diaphragm during the respiratory cycle using EPI sequences (EPI acquisition, 270 ms/image, on a healthy subject ...breathing spontaneously and at 0.1 Hz). Continuously recorded respiratory signal allowed for retrospective synchronization with respiratory phases for reconstruction of successive diaphragm surfaces using a specifically designed software. Displacements, area and volume changes of the diaphragm were quantified. Our measurements were comparable with the data in the literature. Reconstructed surfaces allowed in vivo diaphragm dynamic evaluation in terms of displacements, area and volume variations. EPI has adequate spatial and temporal resolution for studying diaphragm dynamics during natural breathing.
Résumé La thoracocardiographie mesure de façon non invasive le volume d’éjection du cœur à partir des courbes de volume ventriculaire obtenues par pléthysmographie inductive à l’aide d’un capteur ...placé sur le thorax. Le but de cette étude était d’examiner la possibilité d’évaluer le volume d’éjection par thoracocardiographie lors d’une apnée à glotte ouverte. Nous faisons l’hypothèse que le volume d’éjection serait mieux évalué, quand la glotte est ouverte, si le débit d’air des voies aériennes était pris en compte.
The beating heart naturally oscillates the lung because of the close juxtaposition between these organs producing cardiogenic oscillations in flow that can be measured at the mouth when the glottis ...is open. Correspondingly, if the mouth is occluded, the same phenomenon produces cardiogenic pressure oscillations that can be measured just distal to the site of occlusion. The Fourier-domain ratio of these oscillations in pressure and flow constitutes what we call cardiogenic respiratory impedance (Zc). We calculated Zc between about 1.5 and 10 Hz in relaxed normal subjects at functional residual capacity with open glottis. Zc was insensitive to heart rate changes induced by exercise and had an imaginary part close to zero at all frequencies investigated. Its real part was similar to or smaller than resistance determined by the forced oscillation technique. We speculate that Zc measures the flow resistance of the central and upper airways of the lung. Zc may be useful as a means of obtaining information about lung mechanics without the need for an external source of flow perturbations.
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