Similarities between behavior of respiratory muscles in breath-holding and in elastic loading

Dynamic diaphragmatic MRI during apnea struggle phase in breath-hold divers

The purpose of the study was to provide insight in diaphragmatic involuntary breathing movements (IBM) during struggle phase of apnea at total lung capacity (TLC) and functional residual capacity (FRC) using magnetic resonance imaging along with measurements of hemodynamics and arterial oxygenation. The study was performed in eight elite breath-hold divers. There was a similar increase in diaphragmatic cranio-caudal excursions towards the end of TLC and FRC apnea. The greatest diaphragmatic excursion in both apneas and during tidal breathing was in the middle and posterior part of the diaphragm. Diaphragm thickness in elite BHD was within the reference range of normal values suggesting no diaphragmatic hypertrophy in this population. We found that the range of diaphragmatic excursions increases toward the end of apneas. Additionally, our data suggest that the diaphragm participates in IBM occurrence and that various segments of the diaphragm behave nonhomogenously both in tidal breathing and IBMs.

The influence of different modes of ventilation on standing balance of athletes

Background:

The respiratory movements are one of the factors influencing standing balance. Although well-trained athletes have better postural performance compared to untrained men, it's not quite clear, if the formers' upright posture would be more stable during different ventilation modes, maximal voluntary hyperventilation and inspiratory breath-holding. There are no studies on this subject in the available literature.

Objectives:

The aim of this study was to investigate an influence of maximal inspiratory breath-holding and maximal voluntary hyperventilation on the standing balance of athletes.

Patients and Methods:

We assessed the amplitude and the velocity of postural sway in the athletes (n = 38) and untrained subjects (n = 28) by the force platform. The frequency characteristics of the center of pressure (CP) oscillations' were also analyzed. The amplitude and the frequency of respiratory movements were estimated by the strain gauge.

Results:

It was found that during quiet breath velocity and frequency of CP oscillations were lower in the athletes. Breath holding led to an increase of velocity and frequency of CP displacement in both groups, increase of these indices was more pronounced in the athletes. Maximal voluntary hyperventilation caused a significant increase of all stabilographic indices in both groups. Increase of frequency and amplitude of respiratory movements were mainly observed during hyperventilation in athletes and it caused an increase of the velocity of CP displacement. Changes of sway amplitude were the same in both groups.

Conclusions:

Breath holding led to activation of the postural control, which was more pronounced in the athletes. Hyperventilation caused an impairment of the postural stability. The athletes' postural system compensated the impact of hyperventilation more efficiently versus controls, but it was achieved at the expense of greater effort.