The influence of gravity on respiratory kinematics during phonation measured by dynamic magnetic resonance imaging

Respiratory kinematics are important for the regulation of voice production. Dynamic MRI is an excellent tool to study respiratory motion providing high-resolution cross-sectional images. Unfortunately, in clinical MRI systems images can only be acquired in a horizontal subject position, which does not take into account gravitational effects on the respiratory apparatus. To study the effect of body posture on respiratory kinematics during phonation, 8 singers were examined both in an open-configuration MRI with a rotatable gantry and a conventional horizontal MRI system. During dynamic MRI the subjects sang sustained tones at different pitches in both supine and upright body positions. Sagittal images of the respiratory system were obtained at 1–3 images per second, from which 6 anatomically defined distances were extracted to characterize its movements in the anterior, medium and posterior section of the diaphragm as well as the rip cage (diameter at the height of the 3rd and 5th rip) and the anterior–posterior position of the diaphragm cupola. Regardless of body position, singers maintained their general principles of respiratory kinematics with combined diaphragm and thorax muscle activation for breath support. This was achieved by expanding their chest an additional 20% during inspiration when singing in the supine position but not for sole breathing. The diaphragm was cranially displaced in supine position for both singing and breathing and its motion range increased. These results facilitate a more realistic extrapolation of research data obtained in a supine position.

Analysis of Respiratory Kinematics: a method to characterize breaths from motion signals

RationaleBreathing motion (respiratory kinematics) can be characterized by the interval and depth of each breath, and by magnitude-synchrony relationships between locations. Such characteristics and their breath-by-breath variability might be useful indicators of respiratory health.ObjectivesTo enable breath-by-breath characterization of respiratory kinematics, we developed a method to detect breaths using motion sensor signals.MethodsIn 34 volunteers who underwent maximal exercise testing, we used 8 motion sensors to record upper rib, lower rib and abdominal kinematics at 3 exercise stages (rest, lactate threshold and exhaustion). We recorded volumetric air flow signals using clinical exercise laboratory equipment and synchronized them with kinematic signals. Using instantaneous phase landmarks from the analytic representation of kinematic and flow signals, we identified individual breaths and derived respiratory rate signals at 1Hz. To evaluate the fidelity of kinematics-derived respiratory rate signals, we calculated their cross-correlation with the flow-derived respiratory rate signals. To identify coupling between kinematics and flow, we calculated the Shannon entropy of the relative frequency with which kinematic phase landmarks were distributed over the phase of the flow cycle.Measurements and Main ResultsWe found good agreement in the kinematics-derived and flow-derived respiratory rate signals, with cross-correlation coefficients as high as 0.94. In some individuals, the kinematics and flow were significantly coupled (Shannon entropy < 2) but the relationship varied within (by exercise stage) and between individuals. The final result was that the phase landmarks from the kinematic signal were uniformly distributed over the phase of the air flow signals (Shannon entropy close to the theoretical maximum of 3.32).ConclusionsThe Analysis of Respiratory Kinematics method can yield highly resolved respiratory rate signals by separating individual breaths. This method will facilitate characterization of clinically significant breathing motion patterns on a breath-by-breath basis. The relationship between respiratory kinematics and flow is much more complex than expected, varying between and within individuals.

Laryngeal-Respiratory Kinematics are Impaired in Aged Rats

Fatigue and weakness in the elderly are the functional consequences of underlying neuromuscular decline. However, little is known about the manifestations of aging in the larynx. This study evaluated the manner in which laryngeal senescence affects laryngeal-respiratory kinematics by videorecording laryngeal motion in both young and old rats. Recorded images were digitized, and glottal displacement and movement rate were measured. The results indicated that the amplitude of change in glottal angle was significantly diminished, and laryngeal movement durations were prolonged in the old animals. These findings may be due to functional constraints on the respiratory system, impaired laryngeal-respiratory interactions, or decrements in vocal fold tension with age. Because of the serious and pervasive nature of dysphagia and communicative impairments in the elderly, research that specifically examines the manifestations and causes of these impairments is of great importance.

Respiratory Kinematics in Speakers with Cerebellar Disease

The respiratory abilities of a group of 12 speech disordered subjects with cerebellar disease were assessed using both spirometric and kinematic techniques and compared to those of a group of 12 non-neurologically impaired controls matched for age and gender. Results of the spirometric assessment showed that although all of the cerebellar-diseased subjects had normal total lung capacities, almost half had vital capacities below normal limits. All except 1 of the cerebellar-diseased subjects exhibited irregularities in their chest wall movements while performing sustained vowel and syllable repetition tasks. Over half of the cerebellar-diseased subjects also displayed similar rregularities when reading and conversing. The same irregularities were not present in the chest wall movements exhibited by the control subjects suggesting that their presence was caused by the cerebellar disease Results are discussed in terms of the effects of cerebellar disease on neuromuscular function.