Abdominal weight and inspiratory resistance: their immediate effects on inspiratory muscle functions during maximal voluntary breathing in chronic tetraplegic patients.

OBJECTIVE: To study the immediate effects of maximal voluntary (MV) breathing, with and without abdominal weight (AW) or inspiratory resistance (IR), on inspiratory muscle functions in chronic tetraplegic patients. DESIGN: A crossover trial design. SETTING: Rehabilitation department of a university hospital. PARTICIPANTS: Nine tetraplegic men injured at the C4 to T1 levels, with a mean duration of injury of 72.8 months. INTERVENTIONS: Each subject performed MV breathing without and with AW load (AWMV breathing) and IR load (IRMV breathing) separately. MAIN OUTCOME MEASURES: Electromyographic (EMG) activity of the inspiratory muscles, mouth pressure, inspiratory flow, and inspiratory volume. RESULTS: AWMV breathing evoked greater diaphragmatic EMG activity, inspiratory flow, and inspiratory volume than did IRMV breathing, although the increase of diaphragmatic EMG activity was not statistically significant. Conversely, IRMV breathing produced greater sternocleidomastoid EMG activity and negative mouth pressure than did AWMV breathing. Both AWMV and IRMV breathing evoked greater inspiratory muscle EMG activity than did MV breathing. CONCLUSION: AW and IR loads have differential immediate effects on the inspiratory muscle functions during MV breathing in patients with chronic tetraplegia, suggesting that these two breathing maneuvers may have dissimilar mechanisms of training in such patients. The muscle EMG activity evoked during MV breathing with AW or IR is greater than that without a mechanical load, implying that mechanically loaded training in tetraplegic patients results in load compensatory adjustments via their respiratory motor output to improve respiratory function.     

Pursed lips breathing improves ventilation in myotonic muscular dystrophy

OBJECTIVE: To determine the effects of pursed lips breathing on ventilation, chest wall mechanics, and abdominal muscle recruitment in myotonic muscular dystrophy (MMD). DESIGN: Before-after trial. SETTING: University hospital pulmonary function laboratory. PARTICIPANTS: Eleven subjects with MMD and 13 normal controls. INTERVENTION: Pursed lips breathing. OUTCOME MEASURES: Electromyographic (EMG) activity of the transversus abdominis, external oblique, internal oblique, and rectus abdominis was recorded with simultaneous measures of gastric pressure, abdominal plethysmography, and oxygen saturation. Self-reported sensations of dyspnea, respiratory effort, and fatigue were recorded at the end of each trial. RESULTS: Pursed lips breathing and deep breathing led to increased tidal volume, increased minute ventilation, increased oxygen saturation, reduced respiratory rate, and reduced endexpiratory lung volume. Dyspnea, respiratory effort, and fatigue increased slightly with pursed lips breathing. EMG activity of the transversus abdominis and internal oblique muscles increased in MMD only and was associated with an increase in gastric pressure. CONCLUSIONS: Pursed lips breathing and deep breathing are effective and easily employed strategies that significantly improve tidal volume and oxygen saturation in subjects with MMD. Abdominal muscle recruitment does not explain the ventilatory improvements, but reduced end-expiratory lung volume may increase the elastic recoil of the chest wall. Further clinical studies are needed to ascertain if the ventilatory improvements with pursed lips breathing and deep breathing improve pulmonary outcomes in MMD.     

The influence of breathing type, expiration and cervical posture on the performance of the cranio-cervical flexion test in healthy subjects

The cranio-cervical flexion test (CCF-T) is used as a clinical evaluation tool for the deep cervical flexors (DCF). The influence of breathing type, expiration and cervical posture on the performance of the test is evaluated in asymptomatic subjects. Thirty volunteers participated in the study and were classified according to their breathing type: costo-diaphragmatic breathing type and upper costal breathing type. Sternocleidomastoid (SCM) electromyographic (EMG) activity was recorded during five incremental levels of CCF during normal breathing as well as during expiration. The cranio-vertebral angle of each subject was measured to quantify cervical posture. During normal inspiration, higher EMG activity of the SCM muscles was observed in subjects with an upper costal breathing pattern compared to costo-diaphragmatic breathing subjects. This difference was statistically significant (P< 0.05) at the three lowest stages of the test. In the upper costal breathing group a significantly lower EMG activity of the SCM muscles was observed while performing the CCF-T during slow expiration compared to normal breathing. No significant correlation was found between the cranio-vertebral angle and the EMG activity of the SCM muscles. Performing the CCF-T during slow expiration diminishes the activity of the SCM muscles in subjects with a predominantly upper costal breathing pattern. Using a costo-diaphragmatic breathing pattern while performing the test will optimize the performance. Studies on neck pain patients are required to further clarify this issue.     

Dissociation between respiratory effort and dyspnoea in a subset of patients with stroke

Dyspnoea is not a prominent complaint of resting patients with recent hemispheric stroke (RHS). We hypothesized that, in patients with RHS presenting abnormalities in respiratory mechanics, increased respiratory motor output could translate into an increased perception of dyspnoea. We studied eight wheelchair-bound patients with RHS (mean age 62.4 years), previously evaluated by computerized tomography scanning, and a control group of normal subjects, matched for age and sex. We assessed routine spirometry, inspiratory and expiratory muscle pressures, breathing pattern and dyspnoea using a modified Borg scale. In six patients, we also measured oesophageal pressure during the maximal sniff manoeuvre and tidal inspiratory swing, and mechanical characteristics of the lung in terms of dynamic elastance during both quiet breathing and a hypercapnic/hyperoxic rebreathing test. During room air breathing, ventilation and tidal volume were similar in patients and controls, while tidal inspiratory swings of oesophageal pressure, an index of inspiratory motor output, were greater in patients ( P =0.005). Patients also exhibited a greater dynamic elastance ( P =0.013). During rebreathing, dynamic elastance remained higher ( P =0.01) and a greater than normal inspiratory motor output was found ( P =0.03). Responses of ventilation and tidal volume to carbon dioxide tension were normal, and in all patients but one a lower Borg score for the unit change in carbon dioxide tension and ventilation was found. In conclusion, a higher than normal inspiratory motor output was unexpectedly associated with a blunted perception of dyspnoea in this subset of RHS patients. This is likely to be due to the modulation of the integration process of respiratory sensation.     

Evaluation of Respiratory Function During Reeves Stretcher Use

Objective. We were aware of a small number of cases in our EMS system where patients in respiratory distress had a worsening of their condition after being removed from the home on a Reeves® stretcher (RS). We sought to determine if this prehospital lifting device causes additional respiratory effort used in normal subjects by describing changes in heart rate, pulse oximetry, tidal volume, minute ventilation, andrespiratory rate. Methods. Forty-nine subjects were entered into this study. Data were collected while the subject was supine on the floor in the RS andonce while suspended over the floor in the device. A randomized crossover design was used. Ten subjects were excluded because of inadvertent omission of a nose plug during spirometry. Data points were recorded in the final minute of a 3-minute exposure. Three minutes was chosen to simulate a prehospital transport time from the scene to the ambulance. Minute ventilation, tidal volume, heart rate, pulse oximetry, andrespiratory rate were recorded for each subject during each phase. Subjects were also asked to rate the difficulty of breathing using the modified Borg scale. Results. Data were obtained for 39 subjects. The mean respiratory rate while suspended was 9.9 ± 3.0 breaths per minute compared to 9.1 ± 2.5 breaths per minutes supine on the floor (p = 0.007). The mean minute ventilation while suspended in a RS was 8.17 ± 3.25 L/min versus 7.37 ± 2.37 while lying flat (p = 0.03). There was no difference in tidal volume, heart rate, pulse oximetry, or subjective modified Borg scale ratings. Conclusions. Subjects suspended in a RS for 3 minutes had statistically higher respiratory rates andminute ventilation than the same subjects lying flat. Although these modest changes are clinically insignificant in normal subjects, they could present a significant challenge to subjects in respiratory distress.     

La commande diaphragmatique

The control of breathing results from a complex interaction involving different respiratory centers, which feed signals to a central control mechanism that, in turn, provides output to the effector muscles. The dilators of the upper airway contract first, followed by the inspiratory muscles of the chest, including the diaphragm. This distribution of contraction of all the inspiratory muscles differs from rest to exercise. Afferent inputs arising from chemo- and mechanoreceptors, related to the physical status of the respiratory system and to the activation of the respiratory muscles, constantly modulate the respiratory command to adapt ventilation to the needs. We review the various components of this system, focusing on the respiratory muscles and diaphragm. We discuss the differential inspiratory muscles contribution to breathing during the effort. We outline clinically relevant aspects of breathing control in two conditions, including the control of tidal volume under proportional assist ventilation and during respiratory entrainment called reverse triggering.     

Mechanisms underlying CO2 retention during flow-resistive loading in patients with chronic obstructive pulmonary disease.

The present study examined the respiratory responses involved in the maintenance of eucapnea during acute airway obstruction in 12 patients with chronic obstructive disease (COPD) and 3 age-matched normal subjects. Acute airway obstruction was produced by application of external flow-resistive loads (2.5 to 30 cm H2O/liter per s) throughout inspiration and expiration while subjects breathed 100% O2. Application of loads of increasing severity caused progressive increases in PCO2 in the patients, but the magnitude of the increase in PCO2 varied substantially between subjects. On a resistance of 10 cm H2O/liter per s, the highest load that could be tolerated by all COPD patients, the increase in PCO2 ranged from 1 to 11 mm Hg, while none of the normal subjects retained CO2. Based on the magnitude of the increase in PCO2 the patients could be divided into two groups: seven subjects whose PCO2 increased by less than or equal to 3 mm Hg (group I) and five subjects whose PCO2 increased by greater than 6 mm Hg (group II). Base-line ventilation and the pattern of breathing were similar in the two groups. During loading group I subjects maintained or increased tidal volume while all group II patients decreased tidal volume (VT). The smaller tidal volume in group II subjects was mainly the result of their shorter inspiratory time as the changes in mean inspiratory flow were similar in the two groups. The magnitude of CO2 retention during loading was inversely related to the magnitude of the change in VT (r = -0.91) and inspiratory time (Ti) (r = -0.87) but only weakly related to the change in ventilation (r = -0.53). The changes in PCO2, VT, and Ti during loading correlated with the subjects' maximum static inspiratory pressure, which was significantly lower in group II as compared with group I patients. These results indicate that the tidal volume and respiratory timing responses to flow loads are impaired in some patients with COPD. This impairment, presumably due to poor inspiratory muscle function, appears to lead to CO2 retention during loaded breathing.     

Ventilatory effects of biceps vibration during leg exercise in healthy humans

Summary. The ventilatory effects of biceps tendon vibration were studied in healthy human subjects at rest and at two levels of light leg exercise. This was performed with intent to add the ventilatory effects of selective stimulation of muscle spindles to nervous and humoral respiratory inputs from contracting muscles. Tendon vibration performed in individuals at rest elicited a marked increase in respiratory frequency and in the ratio between inspiratory time and total breath duration with variable changes in tidal volume; this was in agreement with previous results (Jammes et al., 1981). When stimulation of biceps proprioceptors was performed during steady state exercise, the changes in ventilatory timing were attenuated, but variations in tidal volume often occurred. These results suggest that, when respiratory centers are being entrained by performance of work, further activation of muscle receptors exerts complex effects on the breathing pattern with a lack of facilitatory influences in ventilation and gas exchange.     

Thoracocardiography: Noninvasive monitoring of left ventricular stroke volume

Thoracocardiography noninvasively monitors global stroke volume by inductive plethysmographic recording of ventricular volume curves as previously validated by thermodilution. Our purpose was to investigate the potential of thoracocardiography to individually assess stroke volume of the left ventricle. We hypothesized that curves predominantly reflecting left ventricular volume could be obtained by recording waveforms from thoracocardiographic transducers placed at various levels around the chest, and by identifying their origin as the left ventricle if mean expiratory exceeded mean respiratory stroke volumes during spontaneous breathing. Stroke volumes obtained by thoracocardiography in normal subjects were compared beat by beat with estimates derived from simultaneous measurements of left ventricular cavity stroke area by echocardiography with automatic boundary detection. Changes in respiratory variations of stroke volumes were analyzed during spontaneous breathing at fixed rate and tidal volume, during mechanical ventilation, and resistive loaded breathing. In 170 comparisons of beat-by-beat stroke volumes, 89% of thoracocardiographic fell within ±20% of echocardiographic estimates. Changes in tidal volume, resistive loaded breathing, and mechanical ventilation induced respiratory variations of thoracocardiographic derived stroke volumes consistent with the known effect of respiratory changes in intrapleural pressure on left ventricular stroke volumes. The results suggest that thoracocardiography noninvasively tracks changes in left ventricular stroke volumes. Their absolute value may also be monitored if an initial calibration by an independent technique, such as echocardiography, is performed.     

Plasma and Urinary Dopamine: Studies During Fasting and Exercise and in Tetraplegic Man

Dopamine, noradrenaline and adrenaline were measured in plasma and in urine, using double-isotope derivative techniques, in 46 normal subjects and in 17 tetraplegic patients with physiologically complete cervical spinal cord transections above the sympathetic outflow. Dopamine was present in plasma in normal subjects in a concentration of 0.33 μg/1 ± 0.06 (SEM). Twenty-four hour urinary excretion of dopamine averaged 248 yg ± 22. There was a significant correlation between the 24 h urinary excretion of dopamine and of noradrenaline. In the normal subjects plasma dopamine and the urinary excretion of dopamine did not change during three days of fasting while urinary excretion of adrenaline increased twofold. In the normal subjects exercise significantly increased plasma dopamine from 0.25 μg/1 to 0.43 μg/1, but significantly decreased the urinary excretion of dopamine. Exercise significantly increased the excretion of noradrenaline. In the tetraplegic patients the plasma dopamine concentration and the urinary excretion of dopamine were lower but not significantly different from the corresponding values in the normal subjects. Plasma noradrenaline and the urinary excretion of noradrenaline and adrenaline were significantly lower in the tetraplegic patients. It is concluded that dopamine is present in human plasma in concentrations similar to that of noradrenaline. Free dopamine in plasma and urine of normal subjects is not dependent on food intake. Urinary dopamine may be derived from circulating dopamine. Urinary dopamine does not necessarily appear to reflect changes in plasma dopamine. The relationship between plasma dopamine and changes in adrenergic nervous activity deserves further investigation.     

Plasma catecholamines, plasma renin activity and plasma aldosterone in tetraplegic man, horizontal and tilted.

1. Plasma catecholamines, plasma renin activity, plasma aldosterone and haematocrit were measured in four subjects with physiologically complete cervical spinal cord transections, before, during and after head-up tilt to 45 degrees for 30 min. Plasma catecholamines were measured in five normal male volunteers in the supine position and after head-up tilt to 45 degrees for 10 min. 2. After 10 min of head-up tilt, the plasma noradrenaline rose 14% in the tetraplegic patients and 115% in the control subjects. These findings indicate a failure of sympathetic activity in response to head-up tilt in the tetraplegic patients, probably caused by interruption of pathways by which the brain normally controls sympathetic outflow. 3. In the tetraplegic patients the resting plasma renin activities were above normal, and rose more quickly and greater on head-up tilt than in published studies of normal subjects. It is likely that the renal baroreceptors are important in the control of renin release. 4. In the tetraplegic patients, there was a late rise in plasma aldosterone which was probably due to the elevation in plasma renin activity.     

Is low-level respiratory resistive loading during exercise perceived as breathlessness?

1. The effect of adding low-level (2.7 cmH2O 1(-1) s) external respiratory resistive loads on exercise-induced breathlessness has been examined in naive normal subjects; the intensity of this loading was chosen to simulate that confronting an asthmatic subject during exercise. 2. Each of 18 subjects performed two separate tests in which workload was oscillated while the respiratory loading was changed every minute between no loading, inspiratory loading only, and inspiratory plus expiratory loading. Each loading condition was given three times, and both these changes and those in workload were unpredictable as far as the subject was concerned. 3. The purpose was to 'confuse' subjects and obtain subjective estimates of their intensity of breathlessness independent of any expectation associated solely with the readily perceptible changes in external resistances to breathing. The study design was balanced for the group as a whole, both in terms of workload and respiratory loading condition. 4. The addition of these respiratory resistive loads during exercise did not result in a significant increase in the intensity of breathlessness. 5. Estimates of the rate of work of breathing revealed that this increased more with respiratory loading than it did as ventilation rose throughout the test; on the other hand, the intensity of breathlessness increased by a greater extent with continued exercise compared with the changes accompanying the addition of respiratory loads. 6. It is concluded that the intensity of the sensation of breathlessness experienced by normal subjects during exercise is not simple a reflection of an increased rate of work of breathing being performed by the respiratory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of neurally adjusted ventilatory assist and positive end-expiratory pressure on breathing pattern in rabbits with acute lung injury

OBJECTIVE: To evaluate the influence of neurally adjusted ventilatory assist (NAVA) and positive end-expiratory pressure (PEEP) on the control of breathing in rabbits with acute lung injury. DESIGN: Prospective animal study. SETTING: Experimental laboratory in a university hospital. SUBJECTS: Male White New Zealand rabbits (n = 18). INTERVENTION: Spontaneously breathing rabbits with hydrochloric acid-induced lung injury were ventilated with NAVA and underwent changes in NAVA gain and PEEP (six nonvagotomized and five vagotomized). Seven other nonvagotomized rabbits underwent 4 hrs of ventilation with hourly titration of PEEP, Fio2, and NAVA gain. MEASUREMENTS AND MAIN RESULTS: We studied diaphragm electrical activity, respiratory pressures, and breathing pattern. After lung injury, 0 cm H2O of PEEP resulted in high tonic and no discernible phasic diaphragm electrical activity in the nonvagotomized rabbits; stepwise increases in PEEP (up to 11.7 +/- 2.6 cm H2O) reduced tonic but increased phasic diaphragm electrical activity. Increasing the NAVA gain reduced phasic diaphragm electrical activity to almost half and abolished esophageal pressure swings. Tidal volume remained at 4-5 mL/kg, and respiratory rate did not change. In the vagotomized group, lung injury did not induce tonic activity, and phasic activity and tidal volume were several times higher than in the nonvagotomized rabbits. Four hours of breathing with NAVA restored breathing pattern and neural and mechanical breathing efforts to pre-lung injury levels. CONCLUSIONS: Acute lung injury can cause a vagally mediated atypical diaphragm activation pattern in spontaneously breathing rabbits. Modulation of PEEP facilitates development of phasic diaphragm electrical activity, whereupon implementation of NAVA can efficiently maintain unloading of the respiratory muscles without delivering excessive tidal volume in rabbits with intact vagal function.     

Ventilatory responses to exercise and to carbon dioxide in mitral stenosis before and after valvulotomy: causes of tachypnoea

1. The ventilation and cardiac frequency during progressive exercise and the respiratory responses to breathing carbon dioxide have been measured in 33 female patients with mitral stenosis and in 31 control subjects. Compared with the control subjects, the patients' exercise ventilation and cardiac frequency were increased; the exercise tidal volume at standard minute volume, the vital capacity and the ventilatory response to carbon dioxide were reduced. The extent to which the standardized tidal volume was lower during exercise than during breathing carbon dioxide was correlated with the severity of the stenosis, as gauged by the increase in exercise cardiac frequency above the level predicted from anthropometric measurements. 2. Twenty patients were studied postoperatively. In the 12 who showed clinical improvement the exercise ventilation and cardiac frequency were reduced and the exercise tidal volume at a given minute ventilation was increased. The latter change occurred despite a reduction in vital capacity, which was probably a residual effect of thoractomy. There was no significant change in the response to breathing carbon dioxide. No material change in function was observed in the patients whose condition was not improved by the operation. 3. It is suggested that in mitral stenosis the tachypnoea which occurs during exercise, whilst mainly a mechanical consequence of the reduced vital capacity, is also partly due to pulmonary congestion stimulating intrapulmonary receptors.     

Physiological responses to arm exercise in difficult to wean patients with chronic obstructive pulmonary disease

Objectives To evaluate the effects of arm exercise with or without support of mechanical ventilation on breathing pattern, respiratory muscle pressure output, and ratings of dyspnea and arm discomfort in difficult-to-wean patients with COPD. Design and setting Prospective, controlled, physiological study in a respiratory ICU.Patients Eight tracheostomized difficult-to-wean patients.Intervention Patients performed an incremental and an endurance arm exercise while breathing through a trach collar or while receiving pressure support ventilation.Measurements and results Breathing pattern, mechanics, arterial saturation, heart rate, and subjective ratings of dyspnea and arm discomfort were measured at baseline, at the end, and 30 min after exercise. Exercise during pressure support ventilation was found to result in higher peak workload (incremental testing) than exercise during trach collar. Moreover, compared to incremental and endurance testing during trach collar, incremental and endurance testing during pressure support ventilation resulted in greater tidal volume, and lower respiratory rate, lower pressure output from the respiratory muscles, and lower work of breathing. Exercise-induced worsening of dyspnea and arm discomfort during trach collar was similar to the corresponding values recorded during pressure support ventilation. Conclusion In tracheostomized difficult-to-wean patients with COPD arm exercise performed during unassisted respiration (trach collar) causes greater increases in respiratory rate and in respiratory muscle pressure output than arm exercise performed during pressure support ventilation. Exercise-induced dyspnea and arm discomfort are similar during assisted and nonassisted respiration.     

Effect of hyperoxia and hypoxia on exercise-induced breathlessness in normal subjects

1. The subjective changes accompanying alterations in inspired oxygen concentration during heavy exercise have been investigated single blind, in normal subjects. 2. In particular, the intensity of the sensation of breathlessness was quantified using a visual analogue scale and changes were compared with those in objective ventilatory measures. 3. Eleven subjects performed three steady-state work-load exercise tests on different days and 100% O2, 15% O2 or air were randomly administered for a fixed interval during each test. 4. Compared with air breathing, all subjects felt less breathless during 100% O2 breathing, and ten of them felt more breathless when inspiring 15% O2; these changes were reversed on return to air breathing. 5. During and after 100% O2, the time course of changes in breathlessness was similar to those for ear arterial oxygen saturation and minute ventilation such that it could be a secondary response to either. However, during and after inspiration of 15% O2, changes in breathlessness occurred relatively more quickly than those in ventilation, more closely reflecting changes in oxygen saturation; this suggests that hypoxia, per se, could contribute to the genesis of this sensation. 6. Individual variability in breathlessness responses to exercise and changes in inspired oxygen concentration did not correlate with objective ventilatory changes; neither were changes in breathlessness in the group particularly associated with changes in respiratory frequency or tidal volume.     

Does Intercostal Stretch Alter Breathing Pattern and Respiratory Muscle Activity in Conscious Adults?

The effects of intercostal (IC) stretch on breathing patterns and respiratory muscle activity were monitored in nine healthy subjects. Tidal volume (V_t), breathing frequency (F_b), and inspiratory (T_i) and expiratory (T_e) durations were determined from a pneumotachometer. Peak amplitudes and burst durations of activity in the diaphragm, parasternal ICs and external abdominal oblique muscles were determined from surface EMGs.The third and eighth IC spaces were stretched in phase with inspiration or expiration when supine and 60° semi recumbent. V_t increased and T_i and T_e were prolonged, resulting in a decreased F_b, independent of site of stretch, phase of breathing, or body position, during IC stretch compared to controls.Peak amplitudes and burst durations of diaphragmatic EMG and burst durations of parasternal ICs were greater when the third and eighth IC spaces were stretched during inspiration compared to controls. Peak amplitudes of parasternal ICs increased only when the third IC space was stretched during inspiration. When applied during expiration, IC stretch increased only parasternal activity in the supine position. Intercostal stretch applied in phase with inspiration resulted in a slower, deeper breathing pattern with increased activity of the diaphragm and parasternal IC muscles. IC stretch may alter breathing sufficiently to improve gas exchange in some patients with pulmonary disorders.     

Breathing exercises: influence on breathing patterns and thoracoabdominal motion in healthy subjects

BACKGROUND:

The mechanisms underlying breathing exercises have not been fully elucidated.

OBJECTIVES:

To evaluate the impact of four on breathing exercises (diaphragmatic breathing, inspiratory sighs, sustained maximal inspiration and intercostal exercise) the on breathing pattern and thoracoabdominal motion in healthy subjects.

METHOD:

Fifteen subjects of both sexes, aged 23±1.5 years old and with normal pulmonary function tests, participated in the study. The subjects were evaluated using the optoelectronic plethysmography system in a supine position with a trunk inclination of 45° during quiet breathing and the breathing exercises. The order of the breathing exercises was randomized. Statistical analysis was performed by the Friedman test and an ANOVA for repeated measures with one factor (breathing exercises), followed by preplanned contrasts and Bonferroni correction. A p<0.005 value was considered significant.

RESULTS:

All breathing exercises significantly increased the tidal volume of the chest wall (V_cw) and reduced the respiratory rate (RR) in comparison to quiet breathing. The diaphragmatic breathing exercise was responsible for the lowest V_cw, the lowest contribution of the rib cage, and the highest contribution of the abdomen. The sustained maximal inspiration exercise promoted greater reduction in RR compared to the diaphragmatic and intercostal exercises. Inspiratory sighs and intercostal exercises were responsible for the highest values of minute ventilation. Thoracoabdominal asynchrony variables increased significantly during diaphragmatic breathing.

CONCLUSIONS:

The results showed that the breathing exercises investigated in this study produced modifications in the breathing pattern (e.g., increase in tidal volume and decrease in RR) as well as in thoracoabdominal motion (e.g., increase in abdominal contribution during diaphragmatic breathing), among others.