Breathing pattern during and after exercise of different intensities

Training Specificity of Inspiratory Muscle Training Methods: A Randomized Trial

Introduction

Inspiratory muscle training (IMT) protocols are typically performed using pressure threshold loading with inspirations initiated from residual volume (RV). We aimed to compare effects of three different IMT protocols on maximal inspiratory pressures (PImax) and maximal inspiratory flow (V̇Imax) at three different lung volumes. We hypothesized that threshold loading performed from functional residual capacity (FRC) or tapered flow resistive loading (initiated from RV) would improve inspiratory muscle function over a larger range of lung volumes in comparison with the standard protocol.

Methods

48 healthy volunteers (42% male, age: 48 ± 9 years, PImax: 110 ± 28%pred, [mean ± SD]) were randomly assigned to perform three daily IMT sessions of pressure threshold loading (either initiated from RV or from FRC) or tapered flow resistive loading (initiated from RV) for 4 weeks. Sessions consisted of 30 breaths against the highest tolerable load. Before and after the training period, PImax was measured at RV, FRC, and midway between FRC and total lung capacity (1/2 IC). V̇Imax was measured at the same lung volumes against a range of external threshold loads.

Results

While PImax increased significantly at RV and at FRC in the group performing the standard training protocol (pressure threshold loading from RV), it increased significantly at all lung volumes in the two other training groups (all p < 0.05). No significant changes in V̇Imax were observed in the group performing the standard protocol. Increases of V̇Imax were significantly larger at all lung volumes after tapered flow resistive loading, and at higher lung volumes (i.e., FRC and 1/2 IC) after pressure threshold loading from FRC in comparison with the standard protocol (all p < 0.05).

Conclusion

Only training with tapered flow resistive loading and pressure threshold loading from functional residual capacity resulted in consistent improvements in respiratory muscle function at higher lung volumes, whereas improvements after the standard protocol (pressure threshold loading from residual volume) were restricted to gains in PImax at lower lung volumes. Further research is warranted to investigate whether these results can be confirmed in larger samples of both healthy subjects and patients.

Clinical recommendations for cardiopulmonary exercise testing in children with respiratory diseases

INTRODUCTION

Cardiopulmonary exercise testing (CPET) quantitates and qualitates the integrated physiological response of a person to incremental exercise and provides additional information compared to static lung function tests alone.

AREAS COVERED

This review covers rationale for the use of CPET parameters beyond the usual parameters like peak oxygen uptake and peak minute ventilation in children with respiratory disease.

EXPERT OPINION

CPET provides a wealth of data from rest, submaximal and maximal exercise and data during recovery from exercise. In this review, an interpretative approach is described for analyzing CPET data in children with respiratory disease.

Physiological comparison of hemorrhagic shock and V˙ O2max: A conceptual framework for defining the limitation of oxygen delivery

IMPACT STATEMENT

Disturbance of normal homeostasis occurs when oxygen delivery and energy stores to the body's tissues fail to meet the energy requirement of cells. The work submitted in this review is important because it advances the understanding of inadequate oxygen delivery as it relates to early diagnosis and treatment of circulatory shock and its relationship to disturbance of normal functioning of cellular metabolism in life-threatening conditions of hemorrhage. We explored data from the clinical and exercise literature to construct for the first time a conceptual framework for defining the limitation of inadequate delivery of oxygen by comparing the physiology of hemorrhagic shock caused by severe blood loss to maximal oxygen uptake induced by intense physical exercise. We also provide a translational framework in which understanding the fundamental relationship between the body's reserve to compensate for conditions of inadequate oxygen delivery as a limiting factor to V ˙ O2max helps to re-evaluate paradigms of triage for improved monitoring of accurate resuscitation in patients suffering from hemorrhagic shock.

The Study of Laryngoscopic and Autonomic Patterns in Exercise-Induced Laryngeal Obstruction

OBJECTIVES

(1) Identify laryngeal patterns axiomatic to exercise-induced laryngeal obstruction (EILO) and (2) investigate the role of autonomic function in EILO.

METHODS

Twenty-seven athletic adolescents (13 EILO, 14 control) underwent laryngoscopy at rest and exercise. Glottal configurations, supraglottic dynamics, systolic blood pressure responses, and heart rate recovery were compared between conditions and groups.

RESULTS

Inspiratory glottal angles were smaller in the EILO group than the control group with exercise. However, group differences were not statistically significant ( P > .05), likely due to high variability of laryngeal responses in the EILO group. Expiratory glottal patterns showed statistically greater abductory responses to exercise in the control group ( P = .001) but not the EILO group ( P > .05). Arytenoid prolapse occurred variably in both groups. Systolic blood pressure responses to exercise were higher in the control group, and heart rate recovery was faster in the EILO group. However, no significant differences were seen between the 2 groups on either autonomic parameter ( P > .05).

CONCLUSIONS

"Paradoxical" inspiratory and blunted expiratory vocal fold pattern responses to exercise best characterize EILO. Group differences were only seen with exercise challenge, thus highlighting the utility of provocation and control groups to identify EILO.

Underlying Mechanisms in Episodic Laryngeal Breathing Disorders

The study and management of episodic laryngeal breathing disorders (ELBD)—characterized by paradoxical laryngeal movement patterns and dyspnea—has traditionally focused on clinical presentation of these conditions. However, the underlying mechanisms driving these entities are largely unknown. This article provides a review of potential underlying mechanisms driving clinical expression in ELBD and suggests approaches to the future study of ELBD etiology.

Breathing Pattern Adopted by Children with Cystic Fibrosis with Mild to Moderate Pulmonary Impairment during Exercise

BACKGROUND

It is well known that severe lung impairment in cystic fibrosis (CF) may compromise respiratory muscle function at rest. Even though patients with CF and severe obstructive lung disease exhibit an abnormal breathing pattern during exercise (due to expiratory flow limitation), patients with CF and normal lung function reportedly have a normal breathing pattern.

OBJECTIVES

The aim of the study was to assess the precise characteristics of the ventilatory pattern adopted during exercise by children with CF and mild to moderate lung disease.

METHODS

Nine children diagnosed as having mild to moderate CF and 9 healthy children with a similar age distribution participated in this study. Both groups performed a continuous incremental cycling protocol. Breathing and timing components were assessed during exercise.

RESULTS

Differences in the breathing pattern between children with CF and controls during exercise are illustrated in Hey plot which described a rapid shallow breathing pattern in children with CF. During exercise, children with CF showed a significantly lower mean inspiratory flow than healthy children (p < 0.001), whereas the mean expiratory flow was higher (p < 0.001). Children with CF also showed a significant increase in the end-tidal carbon dioxide pressure, which may indicate the emergence of hypercapnia.

CONCLUSIONS

During exercise, children with CF (even those not suffering from advanced disease) showed signs of rapid, shallow breathing and an increase in the ventilatory response. This was essentially due to an increase in the mean inspiratory flow, which in turn suggests an expiratory flow limitation. The children were also predisposed to hypercapnia.

Pulmonary Oedema following Exercise in Humans

Pulmonary physiologists have documented many transient changes in the lung and the respiratory system during and following exercise, including the incomplete oxygen saturation of arterial blood in some subjects, possibly due to transient pulmonary oedema. The large increase in pulmonary arterial pressure during exercise, leading to either increased pulmonary capillary leakage and/or pulmonary capillary stress failure, is likely to be responsible for any increase in extravascular lung water during exercise. The purpose of this article is to summarise the studies to date that have specifically examined lung water following exercise. A limited number of studies have been completed with the specific purpose of identifying pulmonary oedema following exercise or a similar intervention. Of these, approximately 50% have observed a positive change and the remaining have provided results that are either inconclusive or show no change in extravascular lung water. While it is difficult to draw a firm conclusion from these studies, we believe that pulmonary oedema does occur in some humans following exercise. As such, this is a phenomenon of significance to pulmonary and exercise physiologists. This possibility warrants further study in the area with more precise measurement tools than has previously been undertaken.

The effect of sustained heavy exercise on the development of pulmonary edema in trained male cyclists

To determine whether intense, prolonged activity can induce transient pulmonary edema, eight highly trained male cyclists (mean +/- S.D.: age, 26.9 +/- 3.0 years; height, 179.9 +/- 5.7 cm; weight, 76.1 +/- 6.5 kg) performed a 45-min endurance cycle test (ECT). V(O2,max) was determined (4.84 +/- 0.4 L min(-1), 63.7 +/- 2.6 ml min(-1) g(-1)) and the intensity of exercise for the ECT was set at 10% below ventilatory threshold (approximately 76% V(O2, max) 300 +/- 25 W). Pre- and post-exercise pulmonary diffusion (DL(CO)) measurements and magnetic resonance imaging of the lung were made. DL(CO) and pulmonary capillary blood volume (VC) decreased 1h post-exercise by 12% (P = 0.004) and 21% (P = 0.017), respectively, but no significant change in membrane diffusing capacity (DM) was found. The magnetic resonance scans demonstrated a 9.4% increase (P = 0.043) in pulmonary extravascular water 90 min post-exercise. These data support the theory that high intensity, sustained exercise in well-trained athletes can result in transient pulmonary edema.

Pattern of ventilation during exercise in chronic heart failure

OBJECTIVE

To determine the pattern of the abnormal ventilatory response in heart failure and how it relates to symptoms by looking at tidal volume (VT) and frequency (f) during exercise.

METHODS

45 patients with heart failure and 21 controls underwent maximal treadmill based exercise testing with metabolic gas exchange analysis. The relation of ventilation (VE) to VT was plotted to look for an inflection point where VT failed to increase further. The slope of the relation before this inflection point was documented. Time to the inflection point, VT, and f at the inflection point were recorded. The relation of symptom scores to f and E was also examined.

RESULTS

Peak oxygen consumption (PVO2) (mean (SD)) was lower (19.7 (4.5) v 37.9 (8.6) ml/kg/min; p < 0001) and the ventilation to carbon dioxide production (VE/VCO2) slope was steeper (40.0 (6.5) v 26.0 (1.6); p < 0.0001) in patients with heart failure than in the control group. The patients reached the inflection point of the VE/VT slope sooner during exercise than the controls (271 (110) v 502 (196) seconds; p < 0.0001). Patients had a higher f and a smaller VT at that point and throughout exercise until the peak where f was the same for patients and controls. VT at the inflection point correlated with PVO2 (r = 0.67; p < 0.0001). Despite having an increased sensation of breathlessness for a given E, patients were less symptomatic of f than controls.

CONCLUSIONS

Patients with heart failure breathe at a higher f throughout exercise, reaching an apparent maximal VT earlier. The VT at an inflection point on the VE/VT slope predicts PVO2.

Pattern of breathing during progressive exercise in chronic heart failure

This descriptive study analyzed serial, individual changes in the exercise pattern of breathing (POB) of patients with stable chronic heart failure (CHF). Twenty-two CHF patients underwent maximal, symptom-limited cardiopulmonary exercise test on a treadmill. Minute ventilation (VE), tidal volume (VT), breathing frequency (f), the ventilatory equivalent for carbon dioxide (VE/VCO2) and estimated dead-space to tidal volume ratio (VD/VT) were continuously recorded. The VE/VCO2 slope was calculated in every subject as the slope of the regression line relating VE to VCO2 during exercising testing. Pattern of breathing was investigated by constructing the individual VT-f relationship for each patient separately. In 16 (73%) patients (group 1), the VT-f plot was initially linear, but subsequently exhibited an inflection point at which VT stopped increasing with further increases in f. In six (27%) patients (group 2) no inflection point was evident on the VT-f relation; in four of these patients the VT-f relation remained linear but shifted to the right throughout testing, and two patients decreased VT before peak exercise achieving high breathing frequencies. Comparing group 1 to group 2 patients, they had higher VEmax (68+/-23 vs. 44+/-10 l/min, P=0.02) and VO2max (17+/-5 vs. 12+/-3 ml/min/kg, P=0.01). In contrast, the two groups did not differ in terms of age, weight, height, diagnosis, ejection fraction or VE/VCO2 slope. In conclusion, patients with CHF adopt variable breathing patterns during exercise; specific patterns are associated with greater impairment in functional capacity.

The relationship between test protocol and the development of exercise-induced hypoxemia (EIH) in highly trained athletes

Healthy male endurance-trained cyclists [n = 11, age = 27.3 (3.9) years; mass = 73.0 (9.3) kg; height = 180.5 (6.9) cm; maximal oxygen consumption (VO2max) = 71.1 (5.8) ml.kg-1.min-1, mean +/- (SD)] were recruited to assess the relationship between test protocol and the development of desaturation of arterial hemoglobin with oxygen, during incremental exercise tests to maximal aerobic capacity (VO2max). All subjects demonstrated resting pulmonary function within normal limits [forced vital capacity (FVC) = 6.0 (0.9); forced expiratory volume (FEV1.0) = 4.9 (0.6); FEV1.0/FVC = 0.8 (0.1)] and completed three ramped VO2max tests (Mijnhardt KEM-3 electronically braked cycle ergometer) beginning at 0 W with increments of either 20,30 or 40 W.min-1. All periods of testing were separated by a minimum of 72 h. VO2max, peak minute ventilation (VEpeak) (Medical Graphics, CPX-D), peak heart rate (fcpeak), peak power output (Wpeak), and minimum percentage arterial oxyhemoglobin saturation (% SaO2min) (Omeda Biox 3740 pulse oximeter) were determined. There were no significant differences (p > 0.05) in VEpeak [191.5 (26.2), 196.0 (24.4), 194.3 (23.9) l.min-1] fcpeak [191.4 (7.0), 190.3 (5.5), 187.8 (5.9) beats.min-1], VO2max [5.0 (0.5), 5.1 (0.4), 5.1 (0.5) l.min-1] or %SaO2min [89.5 (1.5), 89.6 (1.3), 90.0 (2.3)] between protocols. The 20-W protocol [417 (27) W] demonstrated significantly lower Wpeak (P < 0.05) than the 30-W [434 (36) W] and 40-W [453 (38) W] protocols, indicating that peripheral fatigue may play an important factor in response to these tests. The results of this study demonstrate that arterial desaturation occurs as a result of intense exercise in highly trained athletes independent of the rate of attainment of VO2max.

Pulmonary gas exchange and breathing pattern during and after exercise in highly trained athletes

Highly trained athletes (HT) have been found to show arterial hypoxaemia during strenuous exercise. A lack of compensatory hyperpnoea and/or a limitation of pulmonary diffusion by pulmonary interstitial oedema have been suggested as causes, but the exact role of each is not clear. It is known, however, that interstitial pulmonary oedema may result in rapid shallow breathing (RSB). The purpose of this study was therefore twofold: firstly, to determine the exact role of a lack of compensatory hyperpnoea versus a widened in ideal alveolar minus arterial oxygen partial pressure difference [PA(i)-aO2] in the decrease in partial pressure of oxygen in arterial blood (PaO2) and, secondly, to detect RSB during recovery in HT. Untrained subjects (UT) and HT performed exhausting incremental exercise. During rest, exercise testing, and recovery, breathing pattern, respiratory gas exchange, and arterial blood gases were measured. The PA(i)-aO2 and the difference in tidal volume (VT) between exercise and recovery for the same level of ventilation, normalized to vital capacity of the subject [delta VT(%VC)], were then calculated. A large positive delta VT(%VC) was considered to be the sign of RSB. HT showed a marked hypoxaemia (F = 11.6, P < 0.0001), higher partial pressure of carbon dioxide in arterial blood (F = 3.51, P < 0.05), and lower ideal partial pressure of oxygen in alveolar gas (P < 0.001). The relationship between PA(i)-aO2 and oxygen consumption was the same for the two groups. The widening PA(i)-aO2 persisted throughout recovery for both HT and UT. The RSB was observed in HT during recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term modulation of the exercise ventilatory response in goats

1. To test the hypothesis that repeated associations of exercise and increased respiratory dead space elicit mechanisms that augment future ventilatory responses to exercise alone, experiments were conducted on normal adult goats familiarized with experimental procedures. 2. Measurements of ventilation, arterial blood gases and CO2 production were made at rest, during mild steady-state exercise (4 km h-1; 5% grade) and with increased dead space at rest in seven goats before and after training. In Series I experiments, training consisted of fourteen to twenty exercise trials explicitly paired with increased dead space (0.8 l) over 2 days. Increased dead space predominantly represents a CO2 chemoreceptor stimulus with only mild hypoxic stimulation. Post-training measurements were made 1-6 h and 1 week after training was completed. 3. The same goats repeated a slightly modified protocol several months later (Series II; 6 trials per day for 4 days) to determine if responses were both repeatable and reversible, and to investigate training effects on dynamic ventilatory responses at the onset of exercise. 4. In Series I experiments, resting minute ventilation and breathing frequency were elevated 1-6 h post-training compared to baseline (44 and 74% respectively), whereas resting tidal volume decreased (14%). One week post-training, resting values had returned to baseline. Series II training had no significant effects on resting measurements. 5. Relative to baseline, arterial partial pressure of CO2 (Pa,CO2) values decreased significantly more from rest to exercise 1-6 h post-training in both Series I (2.7 +/- 0.2 vs. 1.8 +/- 0.9 mmHg) and Series II (3.4 +/- 0.6 vs. 2.0 +/- 0.6 mmHg). The exercise ventilatory response increased 25-28% 1-6 h post-training (both series), largely due to a greater exercise frequency response, but returned to baseline 1 week post-training. Training had no effect on ventilatory responses to CO2 at rest, suggesting that decreases in CO2 chemoreceptor responsiveness did not cause the greater exercise ventilatory response. Model estimates indicate that the net feedforward exercise ventilatory stimulus was increased 40-50% by training. 6. Training had no discernable effects on ventilatory dynamics at the onset of exercise. However, post-training differences in Pa,CO2 regulation and ventilation were established early in exercise, prior to steady state. 7. Collectively, these experiments suggest a previously unsuspected degree of repeatable and reversible plasticity in the control system subserving the exercise ventilatory response. Such plasticity may contribute to the development of normal exercise hyperpnoea and to adaptive responses of the ventilatory control system in adult animals.

Ventilation-perfusion matching during exercise

In normal subjects, exercise widens the alveolar-arterial PO2 difference (P[A-a]O2) despite a more uniform topographic distribution of ventilation-perfusion (VA/Q) ratios. While part of the increase in P(A-a)O2 (especially during heavy exercise) is due to diffusion limitation, a considerable amount is caused by an increase in VA/Q mismatch as detected by the multiple inert gas elimination technique. Why this occurs is unknown, but circumstantial evidence suggests it may be related to interstitial pulmonary edema rather than to factors dependent on ventilation, airway gas mixing, airway muscle tone, or pulmonary vascular tone. In patients with lung disease, the gas exchange consequences of exercise are variable. Thus, arterial PO2 may increase, remain the same, or fall. In general, patients with advanced chronic obstructive pulmonary disease (COPD) or interstitial fibrosis who exercise show a fall in PO2. This is usually not due to worsening VA/Q relationships but mostly to the well-known fall in mixed venous PO2, which itself results from a relatively smaller increase in cardiac output than VO2. However, in interstitial fibrosis (but not COPD), there is good evidence that a part of the fall in PO2 on exercise is caused by alveolar-capillary diffusion limitation of O2 transport; in COPD (but not interstitial fibrosis), a frequent additional contributing factor to the hypoxemia of exercise is an inadequate ventilatory response, such that minute ventilation does not rise as much as does CO2 production or O2 uptake, causing arterial PCO2 to increase and PO2 to fall.

Tuberculous pericarditis: long-term outcome in patients who received medical therapy alone

A conservative approach to operative intervention in the treatment of active tuberculous pericarditis was adopted and only 4 of 16 consecutive patients underwent pericardiectomy, all within 2 months of diagnosis. One patient died of constrictive pericarditis despite pericardiectomy, and one died of acute bronchopneumonia after 8 months of otherwise successful medical management. All 14 long-term survivors were reevaluated to exclude chronic constrictive pericarditis and other potential sequelae of tuberculous pericarditis. Reevaluation included physical examination, chest radiograph, electrocardiogram, M-mode and two-dimensional echocardiogram, computed tomography (CT) scan, and in patients less than or equal to 75 years of age, incremental cycle exercise to maximum oxygen consumption. None were found to have chronic constrictive pericarditis or convincing evidence of other recognized complications of tuberculous pericarditis. Our results suggest that when pericardiectomy is not required for the relief of cardiac compression during the acute phase of tuberculous pericarditis and patients are treated with medical therapy alone, an excellent long-term outcome may be anticipated.

Ventilatory and occlusion-pressure responses to exercise in trained and untrained children

Pattern of breathing and mouth occlusion pressure were investigated during an incremental and exhaustive ergocycle test in untrained and trained 11 to 13 year old boys. At each level of exercise, the trained group had lower ventilation, a lower respiratory equivalent, and a lower respiratory rate. These results suggest that trained subjects have more efficient ventilation. Lower ventilation coincided with a smaller mean inspiratory flow (VT/TI), while the ratio of inspiratory to total breath (TI/TTOT) was unchanged. In contrast, mouth occlusion pressure and the index of neuromuscular inspiratory drive were the same up to 60 W for the two groups, and tended to be slightly lower in the trained boys above this level.

The effects of beta-adrenoceptor blockade on breathing during progressive exercise in normal man

1 We have studied the effects of single oral doses of 80 mg propranolol and 100 mg atenolol on breathing during progressive exercise in nine healthy men in a double-blind, placebo-controlled experiment. As judged by their effects on exercise heart rate significant levels of beta-adrenoceptor blockade were achieved. 2 At the two lower levels of work rate (50 watts and 100 watts) minute ventilation on atenolol was lower than on placebo while at the highest level of work (200 watts) minute ventilation was higher on atenolol than on placebo. The regression of VE atenolol on VE placebo was 1.28 which is significantly different from unity (P less than 0.001). The results with propranolol were more scattered and failed to reach the 5% level of significance. 3 Effects on the pattern of breathing are small but when minute ventilation is matched with placebo, atenolol results in larger tidal volumes and prolonged inspiratory and expiratory time. 4 These observations are discussed in relation to other work in the literature.