Impact of the pulmonary ventilation function on the prognosis of suspected asthma patients: a retrospective observational study.

OBJECTIVE: Asthma is a common chronic respiratory diseases, and the relationship between pulmonary ventilation function and the prognosis of patients with suspected asthma is not well understood. This study aims to explore the impact of pulmonary ventilation functions on the prognosis of patients with suspected asthma. METHODS: This retrospective observational study included patients with suspected asthma who were diagnosed and treated at the Guangdong Provincial Hospital of Traditional Chinese Medicine between August 2015 and January 2020. The primary outcome of interest was improvement in asthma symptoms, as measured by bronchial provocation test (BPT) results within one year after diagnosis. The impact of pulmonary ventilation functions on prognosis was explored by multivariable logistic regression analysis. RESULTS: Seventy-two patients were included in the study. Patients with normal (OR = 0.123, p = .004) or generally normal (OR = 0.075, p = .039) pulmonary ventilation function were more likely to achieve improvement in asthma symptoms compared with patients with mild obstruction. There were no significant differences between the improvement and non-improvement groups in baseline characteristics. CONCLUSION: These results suggest that suspected asthma patients with normal or generally normal pulmonary ventilation function are more likely to achieve improvement in asthma symptoms within one year compared to patients with mild obstruction.

The effect of an airflow restriction mask (ARM) on metabolic, ventilatory, and electromyographic responses to continuous cycling exercise.

This study analyzed the physiological adjustments caused by the use of the Elevation training mask® (2.0), an airflow restriction mask (ARM) during continuous exercise. Eighteen physically active participants (12 men and 6 women) were randomized to two protocols: continuous exercise with mask (CE-ARM) and continuous exercise without mask (CE). Exercise consisted of cycling for 20 minutes at 60% of maximum power. Metabolic variables, lactate, and gas concentration were obtained from arterialized blood samples at pre and post exercise. Continuous expired gases and myoelectric activity of the quadriceps were performed at rest and during the test. We observed no reduction in oxygen saturation in CE-ARM, leading to lower pH, higher carbon dioxide, and greater hematocrit (all p <0.05). The expired gas analysis shows that the CE-ARM condition presented higher oxygen uptake and expired carbon dioxide concentrations (p <0.05). The CE-ARM condition also presented lower ventilatory volume, ventilatory frequency, and expired oxygen pressure (p <0.05). No changes in electromyography activity and lactate concentrations were identified. We conclude that using ARM does not induce hypoxia and represents an additional challenge for the control of acid-base balance, and we suggest the use of ARM as being suitable for respiratory muscle training.

Adenosine in the lateral hypothalamus/perifornical area does not participate on the CO2 chemoreflex.

The Lateral Hypothalamus/Perifornical Area (LH/PFA) has been shown to be involved with the hypercapnic ventilatory response, in a state-dependent manner. We have demonstrated that purinergic signaling through ATP in the LH/PFA has an excitatory effect in ventilatory response to CO2 in awake rats in the dark phase of the diurnal cycle, but it is unknown whether the ATP metabolite adenosine, acting in the LH/PFA, modulates the ventilatory responses to hypercapnia. Here, we studied the effects of the microdialysis of adenosine (A1/A2 adenosine receptors agonist; 17 mM) and an A1 receptor antagonist (DPCPX; 0.1 mM) into the LH/PFA of conscious rats on ventilation in room air and in 7% CO2 during the light and the dark phases of the diurnal cycle. The microdialysis of adenosine and DPCPX caused no change in the CO2 ventilatory responses of rats during wakefulness or NREM sleep in either the dark or light period. Our data suggest that adenosine in the LH/PFA does not contribute to the hypercapnic ventilatory response in conscious rats.

Investigation into Deep Breathing through Measurement of Ventilatory Parameters and Observation of Breathing Patterns.

In this protocol, two deep breathing patterns were shown to 15 participants to determine an easy yet effective method of breathing exercise for future application in a clinical setting. The women in their twenties were seated comfortably in a chair with back support. They were fitted with an airtight mask connected to a gas analyzer. Three electrodes were placed on the chest connected to a wireless transmitter for relaying to the electrocardiograph. They executed a 5 min rest phase, followed by 5 min of deep breathing with a natural breathing pattern, terminating with a 5 min rest phase. This was followed by a 10 min intermission before commencing the second instruction phase of substituting the natural breathing pattern with the diaphragmatic breathing pattern. Simultaneously, the following took place: a) continuous collection, measurement and analysis of the expired gas to assess the ventilatory parameters on a breath-by-breath basis; b) measurement of the heart rate by an electrocardiograph; and c) videotaping of the participant's thoracoabdominal movement from a lateral aspect. From the video capture, the investigators carried out visual observation of the fast-forward motion-images followed by classification of the breathing patterns, confirming that the participants had carried out the method of deep breathing as instructed. The amount of oxygen uptake revealed that, during deep breathing, the work of breathing decreased. The results from the expired minute ventilation, respiration rate and tidal volume confirmed increased ventilatory efficiency for deep breathing with the natural breathing pattern compared to that with the diaphragmatic breathing pattern. This protocol suggests a suitable method of instruction for assessing deep breathing exercises on the basis of oxygen consumption, ventilatory parameters, and chest wall excursion.

Influence of inspiratory threshold load on cardiovascular responses to controlled breathing at 0.1 Hz.

Slow, deep breathing is being used as a self-management intervention for various health conditions including pain and hypertension. Stimulation of the arterial baroreceptors and increased vagal modulation are among the proposed mechanisms for the therapeutic effects of slow, deep breathing. We investigated whether adding inspiratory threshold load can enhance the cardiovascular responses to controlled breathing at the frequency of 0.1 Hz, a common form of slow, deep breathing. Healthy volunteers (N = 29) performed controlled breathing at 0.1 Hz (6 breaths/minute) without load and with inspiratory threshold loads of 5 cmH2 O and 10 cmH2 O. Respiratory airflow, heart rate, and blood pressure were continuously recorded. The amplitude of the systolic blood pressure variation during respiratory cycles increased with increasing loads. Respiratory sinus arrhythmia was higher during controlled breathing at 0.1 Hz with the load of 10 cmH2 O compared to without load. Baroreflex sensitivity was not affected by loads. The effect of loads on respiratory sinus arrhythmia was mediated by increasing the amplitude of systolic blood pressure variation during respiratory cycles. These results suggest that applying small inspiratory threshold loads during controlled breathing at 0.1 Hz increases cardiac vagal modulation by this breathing exercise. This effect seems to be mediated by stronger stimulation of the arterial baroreceptors because of larger systolic blood pressure swings along the respiratory cycle. The potential benefit of long-term practice of controlled breathing at 0.1 Hz with inspiratory threshold loads on baroreflex function and cardiac vagal control needs to be investigated, particularly in pain and hypertension patients.

The effects of five days of intensive preoperative inspiratory muscle training on postoperative complications and outcome in patients having cardiac surgery: a randomized controlled trial.

OBJECTIVE: To determine the prophylactic efficacy of short-term intensive preoperative inspiratory muscle training on the incidence of postoperative pulmonary complications in patients scheduled for cardiac surgery. DESIGN: Single-blind, randomized controlled pilot study. SETTING: TEDA International Cardiovascular Hospital, China. SUBJECTS: In total, 197 subjects aged ⩾50 years scheduled for cardiac surgery were selected. INTERVENTION: The intervention group ( n = 98) received five days of preoperative inspiratory muscle training on top of the usual care received by the patients in the control group ( n = 99). MAIN MEASURES: The primary outcome variable was the occurrence of postoperative pulmonary complications. The secondary outcome variables were inspiratory muscle strength, lung function and length of hospitalization. RESULTS: After cardiac surgery, a total of 10 (10.2%) of the 98 patients in the intervention group and 27 (27.3%) of 99 patients in the control group had postoperative pulmonary complications (risk ratio, 0.23; 95% confidence interval (CI), 0.09-0.58, P = 0.002). The study revealed that, compared with the control group, the intervention group had a significant increase in inspiratory muscle strength (by 10.48 cm H2O, P < 0.001), forced expiratory volume in the first second of expiration (FEV1) %predicted (by 3.75%, P = 0.030), forced vital capacity (FVC) %predicted (by 4.15%, P = 0.008) and maximal voluntary ventilation (MVV) %predicted (by 6.44%, P = 0.034). Length of hospital stay was 7.51 (2.83) days in the intervention group and 9.38 (3.10) days in the control group ( P = 0.039). CONCLUSION: A five-day intensive pattern of preoperative inspiratory muscle training reduced the incidence of postoperative pulmonary complications and duration of postoperative hospitalization in patients undergoing cardiac surgery.

Exercise ventilatory inefficiency in heart failure and chronic obstructive pulmonary disease.

BACKGROUND: Dyspnea on exertion is common to both heart failure (HF) and chronic obstructive pulmonary disease (COPD), and it is important to discriminate whether symptoms are caused by HF or COPD in clinical practice. The ventilatory equivalent for carbon dioxide (V̇E/V̇CO2) slope and V̇E intercept (a reflection of pulmonary dead space) are two candidate non-invasive indices that could be used for this purpose. Thus, we compared non-invasive indexes of ventilatory efficiency in patients with HF and preserved or reduced ejection fraction (HFpEF and HFrEF, respectively) or COPD. METHODS: Patients with HFpEF (n = 21), HFrEF (n = 20), and COPD (n = 22) patients performed cardiopulmonary exercise testing to volitional fatigue. V̇E and gas exchange were measured via breath-by-breath open circuit spirometry. All data from rest to peak exercise were used to calculate V̇E/V̇CO2 slope and V̇E intercept using linear regression. Receiver operating characteristic (ROC) curves were constructed to determine optimized cutoffs for V̇E/V̇CO2 slope and V̇E intercept to discriminate HFpEF and HFrEF from COPD. RESULTS: HFrEF patients had a greater V̇E/V̇CO2 slope than HFpEF and COPD patients (HFrEF: 40 ±â€¯9; HFpEF: 32 ±â€¯7; COPD: 32 ±â€¯7) (p < 0.01). COPD patients had a greater V̇E intercept than HFpEF and HFrEF patients (COPD: 3.32 ±â€¯1.66; HFpEF: 0.77 ±â€¯1.23; HFrEF: 1.28 ±â€¯1.19 L/min) (p < 0.01). A V̇E intercept of 2.64 L/min discriminated COPD from HF patients (AUC: 0.88, p < 0.01), while V̇E/V̇CO2 slope did not (p = 0.11). CONCLUSION: These findings demonstrate that V̇E intercept, not V̇E/V̇CO2 slope, may discriminate COPD from both HFpEF and HFrEF patients.

Orexinergic neurons are involved in the chemosensory control of breathing during the dark phase in a Parkinson's disease model.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra compacta (SNpc) and the only risk factor is aging. We showed that in 6-hydroxydopamine (6-OHDA)-model of PD there is a reduction in the neuronal profile within the brainstem ventral respiratory column with a decrease in the hypercapnic ventilatory response. Here we tested the involvement of orexin cells from the lateral hypothalamus/perifornical area (LH/PeF) on breathing in a 6-OHDA PD model. In this model of PD, there is a reduction in the total number of orexinergic neurons and in the number of orexinergic neurons that project to the RTN, without changing the number of CO2-activated orexinergic neurons during the dark phase. The ventilation at rest and in response to hypercapnia (7% CO2) was assessed in animals that received 6-OHDA or vehicle injections into the striatum and saporin anti-Orexin-B or IgG saporin into the LH/PeF during the sleep and awake states. The experiments showed a reduction of respiratory frequency (fR) at rest during the light phase in PD animals only during sleep. During the dark phase, there was an impaired fR response to hypercapnia in PD animals with depletion of orexinergic neurons in awake and sleeping rats. In conclusion, the degeneration of orexinergic neurons in this model of PD can be related to impaired chemoreceptor function in the dark phase.

Control of Ventilation in Health and Disease.

Control of ventilation occurs at different levels of the respiratory system through a negative feedback system that allows precise regulation of levels of arterial carbon dioxide and oxygen. Mechanisms for ventilatory instability leading to sleep-disordered breathing include changes in the genesis of respiratory rhythm and chemoresponsiveness to hypoxia and hypercapnia, cerebrovascular reactivity, abnormal chest wall and airway reflexes, and sleep state oscillations. One can potentially stabilize breathing during sleep and treat sleep-disordered breathing by identifying one or more of these pathophysiological mechanisms. This review describes the current concepts in ventilatory control that pertain to breathing instability during wakefulness and sleep, delineates potential avenues for alternative therapies to stabilize breathing during sleep, and proposes recommendations for future research.

The prefrontal oxygenation and ventilatory responses at start of one-legged cycling exercise have relation to central command.

When performing exercise arbitrarily, activation of central command should start before the onset of exercise, but when exercise is forced to start with cue, activation of central command should be delayed. We examined whether the in-advance activation of central command influenced the ventilatory response and reflected in the prefrontal oxygenation, by comparing the responses during exercise with arbitrary and cued start. The breath-by-breath respiratory variables and the prefrontal oxygenated-hemoglobin concentration (Oxy-Hb) were measured during one-legged cycling. Minute ventilation (V̇e) at the onset of arbitrary one-legged cycling was augmented to a greater extent than cued cycling, while end-tidal carbon dioxide tension (ETco2) decreased irrespective of arbitrary or cued start. Symmetric increase in the bilateral prefrontal Oxy-Hb occurred before and at the onset of arbitrary one-legged cycling, whereas such an increase was absent with cued start. The time course and magnitude of the increased prefrontal oxygenation were not influenced by the extent of subjective rating of perceived exertion and were the same as those of the prefrontal oxygenation during two-legged cycling previously reported. Mental imagery or passive performance of the one-legged cycling increased V̇e and decreased ETco2 Neither intervention, however, augmented the prefrontal Oxy-Hb. The changes in ETco2 could not explain the prefrontal oxygenation response during voluntary or passive one-legged cycling. Taken together, it is likely that the in-advance activation of central command influenced the ventilatory response by enhancing minute ventilation at the onset of one-legged cycling exercise and reflected in the preexercise increase in the prefrontal oxygenation.

Los efectos cardiopulmonares del Cough Assist(R) son similares a los promovidos por la tos voluntaria en sujetos sanos. Ensayo clínico aleatorizado / Cardiorespiratory effects of Cough Assist(R) are similar to those promoted by voluntary cough in healthy subjects. A randomized clinical trial

Objetivo: Analizar los efectos hemodinámicos y ventilatorios de la aplicación del Cough Assist(R) y compararlos con los efectos promovidos por la tos voluntaria. Material y métodos: Ensayo clínico aleatorizado. La muestra se compuso de 24 sujetos jóvenes sanos, sometidos a 3 protocolos distintos, utilizando Cough Assist(R) con presiones respiratorias comunes a la práctica clínica: 30S - presión I/E de +30/-30 cmH2O; 50S - presión I/E de +50/-50 cmH2O, y tos voluntaria (TV). Los protocolos se aplicaron a todos los sujetos, con un intervalo entre ellos de al menos 24 h. Se valoraron los parámetros de frecuencia cardiaca, presión arterial, saturación periférica de oxígeno capacidad vital lenta y pico de flujo espiratorio previo a la aplicación de los protocolos (PRE), inmediatamente posterior (POST) y en 20 min (20′ POST). Los análisis estadísticos se realizaron mediante ANOVA de io ii vías y Bonferroni post hoc. Se consideró un nivel de significación estadística de p < 0,05. Resultados: Los efectos promovidos por el Cough Assist(R) fueron similares a los promovidos por la tos voluntaria. En las mujeres no hubo repercusiones significativas en los parámetros valorados. En los hombres la aplicación del Cough Assist(R) y la TV condujeron un aumento de la frecuencia cardiaca, y únicamente la utilización del equipo aumentó la saturación periférica de oxígeno. Conclusión: El uso del Cough Assist(R) con presiones medias y altas no conlleva a repercusiones cardiopulmonares relevantes y su uso se puede considerar similar a los efectos fisiológicos promovidos por la tos voluntaria

Objective: To analyse the haemodynamic and ventilatory effects of the application of Cough Assist(R)® and compare them to those caused by the realization of voluntary cough. Material and methods: A randomised clinical trial. The sample consisted of 24 young healthy subjects who underwent three different protocols using Cough Assist(R) with common respiratory pressures into clinical practice: 30S - pressure I/E +30/-30 cmH2O; 50S - pressure I/E +50/-50 cmH2O; and voluntary cough. Protocols apply to all subjects, with a time interval between them of at least 24 hours. The parameters evaluated were heart rate, blood pressure, peripheral oxygen saturation, slow vital capacity and peak expiratory flow prior to application protocols (PRE), immediately after (POST) and 20 minutes after (20’ POST). Statistical analysis was performed by ANOVA of i or ii pathways and post hoc of Bonferroni. For all analysis were considered a level of statistical significance of P<.05. Results: The effects caused by the Cough Assist(R) were similar to those of voluntary coughing. In women, none of them cause significant impact on the evaluated parameters; in men, both machine and voluntary cough led to increased heart rate, and the application of the Cough Assist(R) increased peripheral oxygen saturation. The other variables remained unchanged. Conclusion: The application of the Cough Assist(R) in medium and high pressure does not cause relevant cardiorespiratory repercussions, being similar to the physiological effects caused by the voluntary cough

The effect of consistent practice of yogic breathing exercises on the human cardiorespiratory system.

The purpose of this investigation was to quantify the cardiovascular, respiratory, and cerebrovascular effects of two common yogic breathing exercises (YBE): bhastrika and chaturbhuj; and to determine the effect of their consistent practice on chemosensitivity. The first study was cross-sectional and compared experienced yogic breathers (YB) with matched controls; whereas the second was a 10-week longitudinal training study. The results support four major findings. First chaturbhuj resulted in a hypoxic stimulus in experienced YB compared to control [end-tidal oxygen tension (PETO2), YB: 77.5±5.7mmHg, P<0.05; control: 94.3±12.0mmHg]. Second, performance of chaturbhuj resulted in cyclic oscillations of mean arterial pressure (MAP), heart rate (HR), and middle cerebral artery velocity (MCAv) consistent with the phases of respiration. Third, post training, performance of bhastrika reduced PETO2 (end breath-hold: 90.8 8±12.1mmHg) compared to rest (100.1±7.4, P<0.05); it also resulted in significantly increased MAP at end breath-hold (96.7±13.0mmHg) compared to rest (83.0±6.6mmHg, P<0.05) and significantly increased mean MCAv (end breath-hold: 87.4±23.0cm/s, P<0.05; rest: 55.8±26.3cm/s). Fourth, experienced YB had lower central chemosensitivity than controls (YB: 3.4±0.4; control: 4.6±1.2L/min/mmHg; P<0.05). In conclusion, YBE significantly alter end-tidal gases, resulting in complex oscillations of cardiovascular and cerebrovascular variables, and if practiced consistently, may reduce chemosensitivity.

Effect of Regular Yoga Practice on Respiratory Regulation and Exercise Performance.

Yoga alters spontaneous respiratory regulation and reduces hypoxic and hypercapnic ventilatory responses. Since a lower ventilatory response is associated with an improved endurance capacity during whole-body exercise, we tested whether yogic subjects (YOGA) show an increased endurance capacity compared to matched non-yogic individuals (CON) with similar physical activity levels. Resting ventilation, the ventilatory response to hypercapnia, passive leg movement and exercise, as well as endurance performance were assessed. YOGA (n = 9), compared to CONTROL (n = 6), had a higher tidal volume at rest (0.7±0.2 vs. 0.5±0.1 l, p = 0.034) and a reduced ventilatory response to hypercapnia (33±15 vs. 47±15 l·min(-1), p = 0.048). A YOGA subgroup (n = 6) with maximal performance similar to CONTROL showed a blunted ventilatory response to passive cycling (11±2 vs. 14±2 l·min(-1), p = 0.039) and a tendency towards lower exercise ventilation (33±2 vs. 36±3 l·min(-1), p = 0.094) while cycling endurance (YOGA: 17.3±3.3; CON: 19.6±8.5 min, p = 0.276) did not differ. Thus, yoga practice was not associated with improved exercise capacity nor with significant changes in exercise ventilation despite a significantly different respiratory regulation at rest and in response to hypercapnia and passive leg movement.

Effects of a nasal ventilator restriction device on lung ventilation and gas exchange during exercise in healthy subjects / Efectos de un dispositivo de restricción ventilatoria nasal sobre la ventilación pulmonar e intercambio gaseoso durante el ejercicio en personas sanas

Introduction and objectives: A device called FeelBreathe® (FB) has been designed, developed and patented for inspiratory muscle training (IMT). In order to examine the effects of FB on lung ventilation and gas exchange during exercise, 27 trained male healthy volunteers (age: 32.5 ± 7.2 years) were measured. Methods: Maximum static inspiratory pressure (PImax) and spirometry to determine lung capacity were measured at baseline. We continued with an incremental cycloergometer to determine the VO2 peak. Three days later, each subject performed randomly three identical submaximal cycloergometer tests at 50% between ventilatory thresholds under three different breathing conditions: a) oronasal breathing (ONB), b) nasal breathing (NB) and c) nasal breathing through the FB. Results: FB trial showed lower minute ventilation (VE) and breathing frequency (BF) than NB, which had lower BF, but similar VE than ONB (p < 0.001). The percentage of inspiration time (Ti/Tot) was 7% greater in FB compared to NB and ONB (p < 0.001). Increased end-tidal pressure of CO2 (PETCO2 ) and reduced end-tidal pressure of O2 (PETO2 ) and fraction of O2 expiration (FEO2 ) were found only in FB. Conclusions: FeelBreathe is a new nasal restriction device that stimulates the inspiratory muscles to produce a breathing pattern more efficiency during exercise in well-trained humans (AU)

Introducción y objetivos: un dispositivo llamado FeelBreathe® (FB) se ha diseñado, desarrollado y patentado para el entrenamiento de la musculatura inspiratoria (IMT). Para examinar los efectos de FB en la ventilación pulmonar y el intercambio gaseoso durante el ejercicio, se tomaron medidas de 27 voluntarios varones sanos entrenados (edad: 32,5 ± 7,2 años). Métodos: al inicio del estudio se midieron tanto la presión inspiratoria máxima estática (PIM) y la capacidad pulmonar mediante espirometría. Seguidamente, se realizó un test incremental en cicloergómetro para determinar el VO2 pico. Cada sujeto, tres días más tarde, realizó aleatoriamente tres pruebas idénticas submáximas en cicloergómetro a una intensidad comprendida al 50% entre los umbrales ventilatorios bajo tres condiciones de respiración diferentes: a) respiración oronasal (ONB), b) respiración nasal (NB) y c) la respiración nasal a través del FB. Resultados: la prueba con FB mostró una ventilación minuto (VE) y una frecuencia respiratoria (BF) inferior que en las pruebas de NB, la cual a su vez tenía menor BF, pero similar VE que ONB (p < 0,001). A pesar de esto, FB obtuvo valores similares de VO2 , cociente respiratorio (RER), frecuencia cardiaca (HR) y saturación de oxígeno capilar periférica (SpO2) en comparación con NB y ONB. Esto último puede ocurrir debido en parte al aumento del volumen tidal (VT) y el tiempo de expiración (Tex) en FB hasta el mismo nivel que en la prueba de NB, los cuales fueron un 15% y 14% en ambas pruebas, respectivamente, superiores a ONB (p < 0,001). El porcentaje de tiempo de inspiración (Ti/Tot) fue 7% mayor en la prueba de FB en comparación con NB y ONB (p < 0,001). Solamente en la prueba de FB se encontró un aumento de la presión final de la espiración de CO2 (PETCO2 ) y la reducción de la presión final de la espiración de O2 (PETO2 ) y la fracción de expiración de O2 (FEO2 ). Conclusiones: FeelBreathe es un nuevo dispositivo de restricción nasal que estimula los músculos inspiratorios para producir un patrón de respiración más eficiente durante el ejercicio en los seres humanos bien entrenados (AU)

Using Pre-Exercise Photobiomodulation Therapy Combining Super-Pulsed Lasers and Light-Emitting Diodes to Improve Performance in Progressive Cardiopulmonary Exercise Tests.

CONTEXT: Skeletal muscle fatigue and exercise performance are novel areas of research and clinical application in the photobiomodulation field, and positive outcomes have been reported in several studies; however, the optimal measures have not been fully established. OBJECTIVE: To assess the acute effect of photobiomodulation therapy (PBMT) combining superpulsed lasers (low-level laser therapy) and light-emitting diodes (LEDs) on muscle performance during a progressive cardiopulmonary treadmill exercise test. DESIGN: Crossover study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty untrained male volunteers (age = 26.0 ± 6.0 years, height = 175.0 ± 10.0 cm, mass = 74.8 ± 10.9 kg). INTERVENTION(S): Participants received PBMT with either combined superpulsed lasers and LED (active PBMT) or placebo at session 1 and the other treatment at session 2. All participants completed a cardiopulmonary test on a treadmill after each treatment. For active PBMT, we performed the irradiation at 17 sites on each lower limb (9 on the quadriceps, 6 on the hamstrings, and 2 on the gastrocnemius muscles), using a cluster with 12 diodes (four 905-nm superpulsed laser diodes with an average power of 0.3125 mW, peak power of 12.5 W for each diode, and frequency of 250 Hz; four 875-nm infrared LED diodes with an average power of 17.5 mW; and four 640-nm red LED diodes with an average power of 15 mW) and delivering a dose of 30 J per site. MAIN OUTCOME MEASURE(S): Distance covered, time until exhaustion, pulmonary ventilation, and dyspnea score. RESULTS: The distance covered (1.96 ± 0.30 versus 1.84 ± 0.40 km, t19 = 2.119, P < .001) and time until exhaustion on the cardiopulmonary test (780.2 ± 91.0 versus 742.1 ± 94.0 seconds, t19 = 3.028, P < .001) was greater after active PBMT than after placebo. Pulmonary ventilation was greater (76.4 ± 21.9 versus 74.3 ± 19.8 L/min, t19 = 0.180, P = .004) and the score for dyspnea was lower (3.0 [interquartile range = 0.5-9.0] versus 4.0 [0.0-9.0], U = 184.000, P < .001) after active PBMT than after placebo. CONCLUSIONS: The combination of lasers and LEDs increased the time, distance, and pulmonary ventilation and decreased the score of dyspnea during a cardiopulmonary test.

A model for the central control of airflow patterns within the human nasal cycle.

BACKGROUND: The nasal cycle exhibits mainly reciprocal changes in nasal airflow that may be controlled from centres in the hypothalamus and brainstem. This study aims to gather new knowledge about the nasal cycle to help develop a control model. METHOD: Right and left nasal airflow was measured in healthy human subjects by rhinomanometry. This was performed over 7-hour periods on 2 study days separated by approximately 1 week. The correlation coefficient for nasal airflow was calculated for day 1 and day 2. RESULTS: Thirty subjects (mean age, 22.7 years) completed the study. The correlation coefficient for nasal airflow varied between r = 0.97 with in-phase changes in airflow and r = -0.89 with reciprocal changes in airflow. The majority of r values were negative, indicating reciprocal changes in airflow (50 out of 60). There was a tendency for r values to become more negative between day 1 and day 2 (p < 0.001). CONCLUSION: A control model involving a hypothalamic centre and two brainstem half centres is proposed to explain both the in-phase and reciprocal changes in airflow associated with the nasal cycle.

Metabolic and Ventilatory Changes During and After High-Frequency Yoga Breathing.

BACKGROUND Practicing high-frequency yoga breathing (HFYB) induced a hypermetabolic state in a single subject during the practice but the effect has not been studied in multiple practitioners. MATERIAL AND METHODS Healthy male volunteers (n=47, group mean age ± S.D., 23.2 ± 4.1 years) were recruited as an experimental group and another twenty volunteers were recruited as a control group. The experimental group practiced either HFYB (Breath rate 1.0 Hz) or breath awareness (BAW) on two separate days. The sequence was reversed for alternate participants. The control group was assessed under similar conditions while sitting at ease. The breath rate (RR), tidal volume (VT), ventilation (VE), VO2, VCO2, arterial PCO2 and energy expenditure (EE Kcal/day) were assessed for 35 minutes using an open circuit oxygen consumption analyzer. The assessment period was divided into before, during and after conditions. Repeated measures analyses of variance (ANOVA) were used to compare data recorded during and after the two practices with data recorded before. Before-After comparisons in the control group were with paired t-tests. RESULTS The most relevant significant changes were increases in VE, VO2, VCO2 and EE during HFYB, while the same variables decreased during the control period. However after HFYB there was no change in VO2 or EE, although VE decreased as it did after the control period. CONCLUSIONS HFYB induces a hypermetabolic state for the duration of the practice which returns to baseline after HFYB suggesting a possible application for HFYB in hypometabolic states.

Effect of Creatine Loading on Oxygen Uptake during a 1-km Cycling Time Trial.

PURPOSE: For the first time, we investigated the effects of altering cellular metabolic capacitance, via a 5-d creatine (Cr) loading protocol (20 g·d⁻¹), on oxygen uptake (VO2), accumulated oxygen deficit, muscle recruitment, and performance during a 1-km cycling time trial. METHODS: In a double-blind, randomized, placebo-controlled design, 19 amateur cyclists were allocated to a Cr (n = 10, VO2peak = 56.0 ± 7.8 mL·kg⁻¹·min⁻¹) or placebo (n = 9, VO2peak = 56.0 ± 8.4 mL·kg⁻¹·min⁻¹) group, and performed a 1-km cycling time trial before and after the supplementation period. RESULTS: Body mass was significantly increased in the Cr group (P < 0.05), but not in the placebo group. Participants adopted an "all-out" pacing strategy in both groups. However, Cr loading reduced VO2 immediately after the beginning (12th to 23th seconds), and this was accompanied by a reduced aerobic and increased anaerobic contribution. The VO2 mean response time was slower (pre: 17.2 ± 5.6 s vs post: 19.9 ± 4.6 s), the total O2 uptake was reduced (pre: 4.64 ± 0.59 L vs post: 4.47 ± 0.53 L), and the oxygen deficit was increased (pre: 0.82 ± 0.27 L vs post: 0.98 ± 0.25 L) after Cr loading. No differences were observed in the placebo group for these variables. Plasma lactate and integrated electromyography were not altered in either group, nor was the time to complete the trial (Cr group: pre: 89.1 ± 6.7 s vs post 89.1 ± 6.2 s and placebo group: pre 85.9 ± 4.9 s vs post 87.0 ± 5.4 s). CONCLUSION: Cr loading slows the V˙O2 response and increases the anaerobic contribution during a 1-km cycling time trial.

Mouth breathing, "nasal disuse," and pediatric sleep-disordered breathing.

BACKGROUND: Adenotonsillectomy (T&A) may not completely eliminate sleep-disordered breathing (SDB), and residual SDB can result in progressive worsening of abnormal breathing during sleep. Persistence of mouth breathing post-T&As plays a role in progressive worsening through an increase of upper airway resistance during sleep with secondary impact on orofacial growth. METHODS: Retrospective study on non-overweight and non-syndromic prepubertal children with SDB treated by T&A with pre- and post-surgery clinical and polysomnographic (PSG) evaluations including systematic monitoring of mouth breathing (initial cohort). All children with mouth breathing were then referred for myofunctional treatment (MFT), with clinical follow-up 6 months later and PSG 1 year post-surgery. Only a limited subgroup followed the recommendations to undergo MFT with subsequent PSG (follow-up subgroup). RESULTS: Sixty-four prepubertal children meeting inclusion criteria for the initial cohort were investigated. There was significant symptomatic improvement in all children post-T&A, but 26 children had residual SDB with an AHI > 1.5 events/hour and 35 children (including the previous 26) had evidence of "mouth breathing" during sleep as defined [minimum of 44 % and a maximum of 100 % of total sleep time, mean 69 ± 11 % "mouth breather" subgroup and mean 4 ± 3.9 %, range 0 and 10.3 % "non-mouth breathers"]. Eighteen children (follow-up cohort), all in the "mouth breathing" group, were investigated at 1 year follow-up with only nine having undergone 6 months of MFT. The non- MFT subjects were significantly worse than the MFT-treated cohort. MFT led to normalization of clinical and PSG findings. CONCLUSION: Assessment of mouth breathing during sleep should be systematically performed post-T&A and the persistence of mouth breathing should be treated with MFT.

Comparison of cardiorespiratory responses during aquatic and land treadmill exercise in patients with coronary artery disease.

PURPOSE: To investigate cardiorespiratory responses during exercise stress tests using an aquatic treadmill and a land-based treadmill in patients with coronary artery disease (CAD). METHODS: Twenty-one stable CAD patients were enrolled. All patients participated in 2 symptom-limited incremental exercise tests, using both an aquatic and a land treadmill. For the aquatic treadmill protocol, patients were submerged to the upper waist in 28°C water. The treadmill speed started at 2.0 km/h and increased 0.5 km/h every minute thereafter. For the land treadmill protocol, the speed and gradient were started at 2.4 km/h and 1.5%, respectively. The speed was increased by 0.3 km/h and grade by 1% every minute thereafter. Oxygen consumption ((Equation is included in full-text article.)O2), heart rate (HR), and respiratory exchange ratio were measured continuously and peak values recorded. Rating of perceived exertion, percentage of age-predicted maximal HR, and total exercise duration were also recorded. RESULTS: Peak cardiorespiratory responses during both protocols were compared. The peak (Equation is included in full-text article.)O2 and peak HR did not show any significant differences. The peak respiratory exchange ratio was significantly greater using the land treadmill than the aquatic treadmill protocol. Rating of perceived exertion, age-predicted maximal HR percentage, and total exercise duration were similar for both protocols. There was a significant linear relationship between HR and (Equation is included in full-text article.)O2 with both protocols. CONCLUSIONS: This study demonstrated that aquatic treadmill exercise elicits similar peak cardiorespiratory responses compared with land treadmill exercise, suggesting that aquatic treadmill exercise may be effective for CAD patients in cardiac rehabilitation.