Compartmental chest wall volume changes during volitional normocapnic hyperpnoea

Ventilation asymmetry, diaphragmatic mobility and exercise capacity in men with traumatic brachial plexus injury

OBJECTIVE

To investigate the repercussions of traumatic brachial plexus injury (TBPI) on diaphragmatic mobility and exercise capacity, compartmental volume changes, as well as volume contribution of each hemithorax and ventilation asymmetry during different respiratory maneuvers, and compare with healthy individuals. The velocity of shortening of the diaphragm, inspiratory, and expiratory muscles were also assessed.

PARTICIPANTS

The cross-sectional study was conducted with 40 male individuals (20 with TBPI who have not undergone nerve transfer surgery [mean age 30.1 ± 5.3] and 20 healthy paired by age and body mass index). Only patients with C8-T1 root avulsion were studied.

MAIN OUTCOME

Compartmental and hemithoracic volumes, as well as asymmetry between the affected and unaffected sides were assessed using optoelectronic plethysmography. The 6 minute walking test was performed to evaluate exercise capacity, while diaphragm mobility was assessed during quiet breathing (QB) using an ultrasound device.

RESULTS

TBPI patients with mean lesion time of 174 ± 45.24 days showed a decreased pulmonary function, respiratory muscle strength, exercise capacity, and diaphragm mobility (all p < .001) compared with healthy. The pulmonary ribcage compartment of the affected side was the main contributor to the reduction in volume during inspiratory capacity, vital capacity, and inspiratory load imposition (all p < .05). This compartment also exhibited a higher ventilation asymmetry with reduced shortening velocity of the inspiratory ribcage muscles.

CONCLUSION

Compared with healthy, TBPI patients who have not undergone nerve transfer surgery present low exercise capacity and diaphragmatic mobility, as well as reduced volume of the upper ribcage compartment on the affected side that leads to reduced shortening velocity and ventilation asymmetry.

Acute and daily effects of repeated voluntary hyperpnea on pulmonary function in healthy adults

PURPOSE

Hyperpnea training has been used as a method for both improving exercise performance in healthy persons and improving ventilatory capacity in patients with pulmonary disease. However, voluntary hyperpnea causes acute declines in pulmonary function, but the effects of repeated days of hyperpnea on airway function are not known. The purpose of this study was to determine the effects of repeated normocapnic hyperpnea on daily and post-hyperpnea pulmonary function in healthy adults.

METHODS

Ten healthy adults (21 years; 170 cm; 66 kg) completed ten hyperpnea training sessions within 17-days (TR). Training sessions consisted of 20-minutes of normocapnic hyperpnea with gradually increased minute ventilation over the 10 days. Spirometry was assessed at baseline and serially following hyperpnea during each experimental day. A control group (24 years; 171 cm; 66 kg) completed 10 days of spirometry with no hyperpnea training (CON).

RESULTS

In both CON and TR subjects, baseline pulmonary function was unchanged during the 10 days. In TR subjects, pulmonary function was decreased at 5 mins after hyperpnea but thereafter increased to pre-hyperpnea values by 30 mins. Furthermore, these changes in pulmonary function were consistent during the 10 training days. In TR subjects, maximal voluntary ventilation decreased by 10.4 ± 8.9% (168-150 L min^-1) over the 10 days (P < 0.05), whereas it was unchanged in CON subjects.

CONCLUSIONS

These findings demonstrate that voluntary hyperpnea acutely decreases airway function in healthy subjects. However, there does not appear to be a cumulative effect of repeated hyperpnea, as daily pulmonary function was unchanged.

Respiratory muscle activity in voluntary breathing tracking tasks: Implications for the assessment of respiratory motor control

How the involuntary (bulbospinal) and voluntary (corticospinal) pathways interact in respiratory muscle control is not established. To determine the role of excitatory corticobulbar pathways in humans, studies typically compare electromyographic activity (EMG) or evoked responses in respiratory muscles during hypercapnic and voluntary tasks. Although ventilation is matched between tasks by having participants track signals of ventilation, these tasks may not result in matched respiratory muscle activity. The aim of this study was to describe respiratory muscle activity and ribcage and abdominal excursions during two different voluntary conditions, compared to hypercapnic hyperventilation. Ventilation was matched in the voluntary conditions via (i) a simple target of lung volume ('volume tracking') or (ii) targets of both ribcage and abdominal excursions, adjusted to end-expiratory lung volume in hypercapnic hyperventilation ('bands tracking'). Compared to hypercapnic hyperventilation, respiratory parameters such as tidal volume were similar, but the ratio of ribcage to abdominal excursion was higher for both voluntary tasks. Inspiratory scalene and parasternal intercostal muscle activity was higher in volume tracking, but diaphragm and abdominal muscle activity showed little to no change. There were no differences in muscle activity in bands tracking for any muscle, compared to hypercapnic hyperventilation. An elevated ratio of ribcage to abdominal excursion in the bands tracking task indicates that participants could not accurately match the targets in this condition. Inspiratory muscle activity is altered in some muscles in some voluntary tasks, compared to hypercapnia. Therefore, differences in muscle activity should be considered in interpretation of studies that use these protocols to investigate respiratory muscle control.

Similar Airway Function after Volitional Hyperpnea in Mild-Moderate Asthmatics and Healthy Controls

BACKGROUND

The beneficial effects of exercise training for asthmatics might relate to repetitive airway stretching. Thus, a training with more pronounced airway stretch using isolated, volitional hyperpnea (HYP) might be similarly or more effective. However, in healthy subjects, a bout of HYP training is known to cause an acute FEV1 decline.

OBJECTIVE

The aim of the present study was therefore to test whether these changes are more pronounced in asthmatics, possibly putting them at risk with HYP training.

METHODS

Nine subjects with mild-moderate asthma (confirmed by mannitol challenge) and 11 healthy subjects performed six 5-min bouts (with 6-min breaks; HYP1) and one 30-min bout (HYP2) of normocapnic HYP at 60% of maximal voluntary ventilation using warm and humid air. FEV1 and airway resistance (R5) were measured before, in breaks (HYP1), and immediately after HYP, and during 60 min of recovery.

RESULTS

In both groups, a significant and similar decrease in FEV1 during HYP1 (asthmatics: -3 ± 3%; healthy subjects: -2 ± 3%), after HYP1 (asthmatics: -2 ± 5%; healthy subjects: -1 ± 4%), and after HYP2 (asthmatics: -4 ± 5%; healthy subjects: -3 ± 3%), and an increase in R5 during and after both HYPs were observed. Maximal changes in FEV1 and R5 did not correlate with baseline lung function or responsiveness to mannitol.

CONCLUSIONS

A bout of HYP does not lead to relevant bronchoconstriction and the observed changes in lung function and airway resistance are neither of the magnitude of clinical relevance, nor do they differ from responses in healthy individuals. Thus, HYP training can safely be tested as an airway-specific exercise training alternative (or add-on) modality to regular aerobic exercise training.