Association of chest wall motion and tidal volume responses during CO2 rebreathing

Changes in respiratory activity induced by mastication during oral breathing in humans

We examined the effect of oral breathing on respiratory movements, including the number of respirations and the movement of the thoracic wall at rest and while chewing gum. Forty normal nose breathers were selected by detecting expiratory airflow from the mouth using a CO2 sensor. Chest measurements were recorded using a Piezo respiratory belt transducer, and electromyographic (EMG) activity of the masseter and trapezius muscles were recorded at rest and while chewing gum during nasal or oral breathing. Oral breathing was introduced by completely occluding the nostrils with a nose clip. During oral breathing, the respiration rate was significantly lower while chewing gum than while at rest (P < 0.05). While chewing gum, the respiration rate was significantly lower during oral breathing than during nasal breathing (P < 0.05). During oral breathing, thoracic movement was significantly higher while chewing gum than while at rest (P < 0.05). Thoracic movement was significantly greater during oral breathing than during nasal breathing (P < 0.05). The trapezius muscle exhibited significant EMG activity when chewing gum during oral breathing. The activity of the trapezius muscle coincided with increased movement of the thoracic wall. Chewing food while breathing through the mouth interferes with and decreases the respiratory cycle and promotes unusual respiratory movement of the thoracic wall, which is directed by the activity of accessory muscles of respiration.

Nonlinear model for estimating respiratory volume based on thoracoabdominal breathing movements

BACKGROUND AND OBJECTIVE

Respiratory inductive plethysmography is a non-invasive technique for measuring respiratory function. However, there are challenges associated with using linear methods for calibration of respiratory inductive plethysmography. In this study, we developed two nonlinear models, artificial neural network and adaptive neuro-fuzzy inference system, to estimate respiratory volume based on thoracoabdominal movements, and compared these models with routine linear approaches, including qualitative diagnostic calibration and multiple linear regression.

METHODS

Recordings of spirometry volume and respiratory inductive plethysmography were obtained for 10 normal subjects and 10 asthmatic patients, during asynchronous breathing for 7 min. The first 5 min of recording were used to develop the models; the remaining data were used for subsequent validation of the results.

RESULTS

The results from the nonlinear models fitted the spirometry volume curve significantly better than those obtained by linear methods, particularly during asynchrony (P < 0.05). On a breath-by-breath analysis, estimates of tidal volume, total cycle time and sigh values using the artificial neural network model were accurate by comparison with qualitative diagnostic calibration. In contrast to the artificial neural network model, there was a significant correlation between values for thoracoabdominal asynchrony and increased error of qualitative diagnostic calibration (P < 0.05).

CONCLUSIONS

These results indicate that the nonlinear methods can be adapted to closely simulate variable conditions and used to study the patterns of volume changes during normal and asynchronous breathing.

A telemedicine instrument for Internet-based home monitoring of thoracoabdominal motion in patients with respiratory diseases

Changes in thoracoabdominal motion are highly prevalent in patients with chronic respiratory diseases. Home care services that use telemedicine techniques and Internet-based monitoring have the potential to improve the management of these patients. However, there is no detailed description in the literature of a system for Internet-based monitoring of patients with disturbed thoracoabdominal motion. The purpose of this work was to describe the development of a new telemedicine instrument for Internet-based home monitoring of thoracoabdominal movement. The instrument directly measures changes in the thorax and abdomen circumferences and transfers data through a transmission control protocol∕Internet protocol connection. After the design details are described, the accuracy of the electronic and software processing units of the instrument is evaluated by using electronic signals simulating normal subjects and individuals with thoracoabdominal motion disorders. The results obtained during in vivo studies on normal subjects simulating thoracoabdominal motion disorders showed that this new system is able to detect a reduction in abdominal movement that is associated with abnormal thoracic breathing (p < 0.0001) and the reduction in thoracic movement during abnormal abdominal breathing (p < 0.005). Simulated asynchrony in thoracoabdominal motion was also adequately detected by the system (p < 0.0001). The experimental results obtained for patients with respiratory diseases were in close agreement with the expected values, providing evidence that this instrument can be a useful tool for the evaluation of thoracoabdominal motion. The Internet transmission tests showed that the acquisition and analysis of the thoracoabdominal motion signals can be performed remotely. The user can also receive medical recommendations. The proposed system can be used in a spectrum of telemedicine scenarios, which can reduce the costs of assistance offered to patients with respiratory diseases.

Optoelectronic Plethysmography has Improved our Knowledge of Respiratory Physiology and Pathophysiology

It is well known that the methods actually used to track thoraco-abdominal volume displacement have several limitations. This review evaluates the clinical usefulness of measuring chest wall kinematics by optoelectronic plethysmography [OEP]. OEP provides direct measurements (both absolute and its variations) of the volume of the chest wall and its compartments, according to the model of Ward and Macklem, without requiring calibration or subject cooperation. The system is non invasive and does not require a mouthpiece or nose-clip which may modify the pattern of breathing, making the subject aware of his breathing. Also, the precise assessment of compartmental changes in chest wall volumes, combined with pressure measurements, provides a detailed description of the action and control of the different respiratory muscle groups and assessment of chest wall dynamics in a number of physiological and clinical experimental conditions.

Chest wall kinematics and respiratory muscle coordinated action during hypercapnia in healthy males

The present study was designed to verify whether during hypercapnic stimulation, as we had previously found during exercise or walking, the partitioning of the respiratory motor output is equally distributed to the muscles of chest wall compartments to assist diaphragm function. We studied chest wall kinematics and respiratory muscle recruitment in seven healthy men during rebreathing of a hypercapnic-hyperoxic gas mixture (CO(2) RT). Data were compared with those previously obtained during either cycling exercise or walking. The chest wall volume ( Vcw), assessed by optoelectronic plethysmography (OEP), was modeled as the sum of the volumes of the lung-apposed rib cage ( Vrc,p), diaphragm-apposed rib cage ( Vrc,a) and abdomen ( Vab). Esophageal ( Pes), gastric ( Pga) and transdiaphragmatic ( Pdi= Pga- Pes) pressures were simultaneously recorded. Velocity of shortening ( V') and power ( W'= Px V') of the diaphragm ( W'di), rib cage muscles ( W'rcm) and abdominal muscles ( W'abm) were also calculated. During CO(2) RT the progressive increase in end-inspiratory Vcw resulted from an increase in both end-inspiratory Vrc,p and Vrc,a, while the progressive decrease in end-expiratory Vcw was entirely due to the decrease in end-expiratory Vab. The increase in Vrc,p was proportionally slightly greater than that in Vrc,a. The end-inspiratory increase and end-expiratory decrease in Vcw were accounted for by inspiratory rib cage (RCM,i) and abdominal (ABM) muscle recruitment, respectively. W'di, W'rcm and W'abm progressively increased. However, while most of W'di was expressed in terms of velocity of shortening, most of W'rcm and W'abm was expressed as force or pressure. A comparison of CO(2) results with data obtained during exercise revealed: (1). a gradual vs. an immediate response, (2). a similar decrease in Vab,e and Pabm, (3). an apparent lack of any difference in ABM recruitment, (4). less gradual ABM relaxation, (5). no drop in Pdi but a similar Wdi change and decrease in pressure-to-velocity ratio of the diaphragm. We have found that in healthy humans: (1). the increased motor output with hypercapnia is equally distributed between RCM and ABM to minimize transdiaphragmatic pressure and (2). data on chest wall kinematics and respiratory muscle recruitment are only partly in line with those obtained during walking or cycling exercise.