Respiratory muscle training and exercise ventilation while diving at altitude.

Introduction: Pre-dive altitude exposure may increase respiratory fatigue and subsequently augment exercise ventilation at depth. This study examined pre-dive altitude exposure and the efficacy of resistance respiratory muscle training (RMT) on respiratory fatigue while diving at altitude. Methods: Ten men (26±5 years; VO2peak: 39.8±3.3 mL• kg-1•min-1) performed three dives; one control (ground level) and two simulated altitude dives (3,658 m) to 17 msw, relative to ground level, before and after four weeks of resistance RMT. Subjects performed pulmonary function testing (e.g., inspiratory [PI] and expiratory [PE] pressure testing) pre- and post-RMT and during dive visits. During each dive, subjects exercised for 18 minutes at 55% VO2peak, and ventilation (VE), breathing frequency (ƒb,), tidal volume (VT) and rating of perceived exertion (RPE) were measured. Results: Pre-dive altitude exposure reduced PI before diving (p=0.03), but had no effect on exercise VE, ƒb, or VT at depth. At the end of the dive in the pre-RMT condition, RPE was lower (p=0.01) compared to control. RMT increased PI and PE (p<0.01). PE was reduced from baseline after diving at altitude (p<0.03) and this was abated after RMT. RMT did not improve VE or VT at depth, but decreased ƒb (p=0.01) and RPE (p=0.048) during the final minutes of exercise. Conclusion: Acute altitude exposure pre- and post-dive induces decrements in PI and PE before and after diving, but does not seem to influence ventilation at depth. RMT reduced ƒb and RPE during exercise at depth, and may be useful to reduce work of breathing and respiratory fatigue during dives at altitude.

Acute thoracoabdominal and hemodynamic responses to tapered flow resistive loading in healthy adults.

We investigated the acute physiological responses of tapered flow resistive loading (TFRL) at 30, 50 and 70 % maximal inspiratory pressure (PImax) in 12 healthy adults to determine an optimal resistive load. Increased end-inspiratory rib cage and decreased end-expiratory abdominal volumes equally contributed to the expansion of thoracoabdominal tidal volume (captured by optoelectronic plethysmography). A significant decrease in end-expiratory thoracoabdominal volume was observed from 30 to 50 % PImax, from 30 to 70 % PImax, and from 50 to 70 % PImax. Cardiac output (recorded by cardio-impedance) increased from rest by 30 % across the three loading trials. Borg dyspnoea increased from 2.36 ±â€¯0.20 at 30 % PImax, to 3.45 ±â€¯0.21 at 50 % PImax, and 4.91 ±â€¯0.25 at 70 % PImax. End-tidal CO2 decreased from rest during 30, 50 and 70 %PImax (26.23 ±â€¯0.59, 25.87 ±â€¯1.02 and 24.30 ±â€¯0.82 mmHg, respectively). Optimal intensity for TFRL is at 50 % PImax to maximise global respiratory muscle and cardiovascular loading whilst minimising hyperventilation and breathlessness.

Biological variation of resting measures of ventilation and gas exchange in a large healthy cohort.

PURPOSE: Resting measures of ventilation and gas exchange are impacted by a variety of physiological stressors, such as those resulting from a research intervention or an extreme environment. However, the biological variation of these parameters, an important statistical consideration for identifying a meaningful physiological change, has not been quantified. METHODS: We performed a retrospective analysis of 21 studies completed by the U.S. Army Research Institute of Environmental Medicine (USARIEM) from 1985 to present, totaling 411 healthy volunteers. First, we determined the intraindividual, interindividual, and analytic coefficients of variation (CVI, CVG, and CVA, respectively) and subsequently the index of individuality and heterogeneity (II and IH, respectively). Second, when deemed appropriate via these outcomes, we defined the accompanying static and dynamic thresholds, beyond which a significant deviation from normal is indicated. RESULTS: End-tidal partial pressure of oxygen (PETO2) and the respiratory exchange ratio (RER) approached the II threshold required to be considered useful in the static assessment of physiological deviations from normal. PETO2 and peripheral oxygen saturation (SpO2) approached the IH threshold required to be considered useful in the dynamic assessment of physiological deviations from normal. CONCLUSIONS: This analysis identifies RER and PETO2 as parameters that might be most useful when aiming to identify a meaningful ventilatory change following a research intervention or stressor. Alternatively, other parameters of ventilation and gas exchange, such as PETCO2 and VE, may be less useful for observing an anticipated physiological change.

Respiratory muscle training in athletes with cervical spinal cord injury: effects on cardiopulmonary function and exercise capacity.

KEY POINTS: The effect of combined inspiratory and expiratory muscle training on resting and reflexive cardiac function, as well as exercise capacity, in individuals with cervical spinal cord injury (SCI) is presently unknown. Six weeks of combined inspiratory and expiratory muscle training enhances both inspiratory and expiratory muscle strength in highly-trained athletes with cervical SCI with no significant effect on lung function. There was a significant decrease in left-ventricular filling and stroke volume at rest in response to 45° head-up tilt, which is irreversible by respiratory muscle training. Combined inspiratory and expiratory muscle training increased peak aerobic work rate and reduced end-expiratory lung volumes during exercise, which may have implications for left-ventricular filling during exercise. ABSTRACT: To investigate the pulmonary, cardiovascular and exercise responses to combined inspiratory and expiratory respiratory muscle training (RMT) in athletes with tetraplegia, six wheelchair rugby athletes (five males and one female, aged 33 ± 5 years) completed 6 weeks of pressure threshold RMT, 2 sessions day-1 on 5 days week-1 . Resting pulmonary and cardiac function, exercise capacity, exercising lung volumes and field-based exercise performance were assessed at pre-RMT, post-RMT and after a 6-week no RMT period. RMT enhanced maximal inspiratory (pre- vs. post-RMT: -76 ± 15 to -106 ± 23 cmH2 O, P = 0.002) and expiratory (59 ± 26 to 73 ± 32 cmH2 O, P = 0.007) mouth pressures, as well as peak expiratory flow (6.74 ± 1.51 vs. 7.32 ± 1.60 L/s, P < 0.04). Compared to pre-RMT, peak work rate was higher at post-RMT (60 ± 23 to 68 ± 22 W, P = 0.003), whereas exercising end-expiratory lung volumes were reduced (P < 0.017). Peak oxygen uptake increased in all athletes at post-RMT (1.24 ± 0.40 vs. 1.40 ± 0.50 l min-1 , P = 0.12). After 6 weeks of no RMT all indices returned towards baseline, with peak work rate (P = 0.037), peak oxygen uptake (P = 0.041) and end-expiratory lung volume (P < 0.034) being significantly lower at follow-up than at post-RMT. There was a significant decrease in left-ventricular end-diastolic volume and stroke volume in response to 45° head-up tilt (P = 0.030 and 0.021, respectively); however, all cardiac indices in both supine and tilted positions were unchanged by RMT. Our findings demonstrate the efficacy of RMT with respect to enhancing respiratory muscle strength, lowering exercising lung volumes and increasing exercise capacity. Although the precise mechanisms by which RMT may enhance exercise capacity remain unclear, our data suggest that it is probably not the result of a direct cardiac adaptation associated with RMT.

Minute ventilation during hypoxia is augmented with capsaicin supplementation in aged mice.

Capsaicin is an agonist for transient receptor potential vanilloid 1 (TRPV1), and acute injection results in an increased frequency and tidal volume in young rats. It is unknown how capsaicin influences breathing in aged mice. We tested the hypothesis that capsaicin supplementation would elicit an augmented pattern of breathing in old mice compared to controls. Male 22-month old C57BL/6 J mice consumed a diet containing capsaicin (50 ppm) or lecithin control for one month. Breathing patterns were obtained prior to/following the dietary supplementation period using unrestrained barometric plethysmography. Frequency, tidal volume (VT), minute ventilation (VE), VE to expelled carbon dioxide ratio (VE/VCO2) and VT divided by inspiratory time (VT/Ti) were analyzed at baseline and during a 15-minute hypoxic exposure (10% O2). Capsaicin supplemented mice showed greater VE, VE/VCO2 and TV/Ti during hypoxic exposure compared to controls, with no change at baseline. Overall, these findings suggest an acute augmented response to hypoxia following capsaicin administration in older mice.

The relation between given volume and heart rate during newborn resuscitation.

BACKGROUND: During delivery room resuscitation of depressed newborns, provision of appropriate tidal volume (TV) with establishment of functional residual capacity (FRC) is essential for circulatory recovery. Effective positive pressure ventilation (PPV) is associated with a rapid increase in heart rate (HR). The relationship between delivery of TV and HR responses remains unclear. OBJECTIVES: The study objectives were to determine (1) the relationship between a given TV during initial PPV and HR responses of depressed newborns, and (2) the optimal delivered TV associated with a rapid increase in HR. METHODS: In a Tanzanian rural hospital, ventilation and ECG signals were recorded during neonatal resuscitation and stored in Neonatal Resuscitation Monitors. Resuscitators without positive end-expiratory pressure were used for PPV. No oxygen was used. Perinatal events were observed and recorded by research assistants. RESULTS: 215 newborns of gestational age 37.3±1.9 weeks and birth weight 3115±579g were included. There was a non-linear relationship between delivered TV and HR increase. TV of 9.3ml/kg produced the largest increase in HR during PPV. Frequent interruptions of PPV sequences to provide stimulation/suctioning occurred in all cases and were associated with further HR increases, especially for newborns with initial HR<100 beats/minute. CONCLUSIONS: There was a consistent positive relationship between HR increase and delivered TV. The unanticipated finding of a further increase in HR with PPV pauses to provide stimulation/suctioning suggests that most newborns were in primary rather than secondary apnea.

A Multisite Benchmarking Trial of Capnometry Guided Respiratory Intervention for Panic Disorder in Naturalistic Treatment Settings.

Panic disorder (PD) is associated with hyperventilation. The efficacy of a brief respiratory feedback program for PD has been established. The aim of the present study was to expand these results by testing a similar program with more clinically representative patients and settings. Sixty-nine adults with PD received 4 weeks of Capnometry Guided Respiratory Intervention (CGRI) using Freespira, which provides feedback of end-tidal CO2 (PETCO2) and respiration rate (RR), in four non-academic clinical settings. This intervention is delivered via home use following initial training by a clinician and provides remote monitoring of client adherence and progress by the clinician. Outcomes were assessed post-treatment and at 2- and 12-month follow-up. CGRI was associated with an intent-to-treat response rate of 83% and a remission rate of 54%, and large decreases in panic severity. Similar decreases were found in functional impairment and in global illness severity. Gains were largely sustained at follow-up. PETCO2 moved from the slightly hypocapnic range to the normocapnic range. Benchmarking analyses against a previously-published controlled trial showed very similar outcomes, despite substantial differences in sample composition and treatment settings. The present study confirms prior clinical results and lends further support to the viability of CGRI in the treatment of PD.

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.

Severe hypoxemia: which strategy to choose.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is characterized by a noncardiogenic pulmonary edema with bilateral chest X-ray opacities and reduction in lung compliance, and the hallmark of the syndrome is hypoxemia refractory to oxygen therapy. Severe hypoxemia (PaO2/FiO2 < 100 mmHg), which defines severe ARDS, can be found in 20-30 % of the patients and is associated with the highest mortality rate. Although the standard supportive treatment remains mechanical ventilation (noninvasive and invasive), possible adjuvant therapies can be considered. We performed an up-to-date clinical review of the possible available strategies for ARDS patients with severe hypoxemia. MAIN RESULTS: In summary, in moderate-to-severe ARDS or in the presence of other organ failure, noninvasive ventilatory support presents a high risk of failure: in those cases the risk/benefit of delayed mechanical ventilation should be evaluated carefully. Tailoring mechanical ventilation to the individual patient is fundamental to reduce the risk of ventilation-induced lung injury (VILI): it is mandatory to apply a low tidal volume, while the optimal level of positive end-expiratory pressure should be selected after a stratification of the severity of the disease, also taking into account lung recruitability; monitoring transpulmonary pressure or airway driving pressure can help to avoid lung overstress. Targeting oxygenation of 88-92 % and tolerating a moderate level of hypercapnia are a safe choice. Neuromuscular blocking agents (NMBAs) are useful to maintain patient-ventilation synchrony in the first hours; prone positioning improves oxygenation in most cases and promotes a more homogeneous distribution of ventilation, reducing the risk of VILI; both treatments, also in combination, are associated with an improvement in outcome if applied in the acute phase in the most severe cases. The use of extracorporeal membrane oxygenation (ECMO) in severe ARDS is increasing worldwide, but because of a lack of randomized trials is still considered a rescue therapy. CONCLUSION: Severe ARDS patients should receive a holistic framework of respiratory and hemodynamic support aimed to ensure adequate gas exchange while minimizing the risk of VILI, by promoting lung recruitment and setting protective mechanical ventilation. In the most severe cases, NMBAs, prone positioning, and ECMO should be considered.

Retention of perceptual generalization of fear extinction.

Fear reduction obtained during a fear extinction procedure can generalize from the extinction stimulus to other perceptually similar stimuli. Perceptual generalization of fear extinction typically follows a perceptual gradient, with increasing levels of fear reduction the more a stimulus resembles the extinction stimulus. The current study aimed to investigate whether perceptual generalization of fear extinction can be observed also after a retention interval of 24h. Fear was acquired to three geometrical figures of different sizes (CS(+), CS1(+) and CS2(+)) by consistently pairing them with a short-lasting suffocation experience (US). Three other geometrical figures that were never followed by the US served as control stimuli (CS(-), CS1(-), CS2(-)). Next, only the CS(+) was extinguished by presenting it in the absence of the US. One day later, fear responses to all stimuli were assessed without any US-presentation. Outcome measures included startle blink EMG, skin conductance, US expectancy, respiratory rate and tidal volume. On day 2 spontaneous recovery of fear was observed in US expectancy and tidal volume, but not in the other outcomes. Evidence for the retention of fear extinction generalization was present in US expectancy and skin conductance, but a perceptual gradient in the retention of generalized fear extinction could not be observed.

Correlational analysis of electroencephalographic and end-tidal carbon dioxide signals during breath-hold exercise.

The central mechanism of breathing control is not totally understood. Several studies evaluated the correlation between electroencephalographic (EEG) power spectra and respiratory signals by performing resting state tasks or adopting hypercapnic/hypoxic stimuli. The observation of brain activity during voluntary breath hold tasks, might be an useful approach to highlight the areas involved in mechanism of breath regulation. Nevertheless, studies of brain activity with EEG could present some limitations due to presence of severe artifacts. When artifact rejection methods, as independent component analysis, cannot reliably clean EEG data, it is necessary to exclude noisy segments. In this study, global field power in the delta band and end-tidal CO2 were derived from EEG and CO2 signals respectively in 4 healthy subjects during a breath-hold task. The cross correlation function between the two signals was estimated taking into account the presence of missing samples. The statistical significance of the correlation coefficients at different time lags was assessed using surrogate data. Some simulations are introduced to evaluate the effect of missing data on the correlational analysis and their results are discussed. Results obtained on subjects show a significant correlation between changes in EEG power in the delta band and end-tidal CO2. Moreover, the changes in end-tidal CO2 were found to precede those of global field power. These results might help to better understand the cortical mechanisms involved in the control of breathing.

Preoperative therapy restores ventilatory parameters and reduces length of stay in patients undergoing myocardial revascularization.

INTRODUCTION: The frequency of surgical procedures has increased steadily in recent decades, including the myocardial revascularization. OBJECTIVES: To demonstrate the importance of physiotherapy in the preoperative period of cardiac surgery in relation to the reduction of hospital stay, changes in lung volumes and respiratory muscle strength. METHODS: We conducted a prospective study with patients undergoing myocardial revascularization, the Hospital das Clínicas da Universidade Estadual Paulista (UNESP)/Botucatu - SP. We evaluated 70 patients of both genders, aged between 40 and 75 years, subdivided into two groups: group I - 35 patients of both genders, who received a written protocol guidance, breathing exercises and respiratory muscle training in the preoperative period and group II - 35 patients of both genders, who received only orientation of the ward on the day of surgery. This study was approved by the Ethics Committee of UNESP / Botucatu - SP. RESULTS: Maximal inspiratory pressure in third postoperative day and fifth postoperative day and significant difference between groups, being better for the intervention group. Expiratory pressure was significant in fifth postoperative day in the intervention group compared to controls. The difference of length of hospital stay in the postoperative was found between the groups with shorter hospital stay in the group receiving preoperative therapy. CONCLUSION: Physical therapy plays an important role in the preoperative period, so that individuals in the intervention group more readily restored the parameters evaluated before surgery, in addition, there was a decrease in the time of the postoperative hospital stay. Thus, it is thought the cost-effectiveness of a program of preoperative physiotherapy.

Consciously controlled breathing decreases the high-frequency component of heart rate variability by inhibiting cardiac parasympathetic nerve activity.

Heart rate variability (HRV), the beat-to-beat alterations in heart rate, comprises sympathetic and parasympathetic nerve activities of the heart. HRV analysis is used to quantify cardiac autonomic regulation. Since respiration could be a confounding factor in HRV evaluation, some studies recommend consciously controlled breathing to standardize the method. However, it remains unclear whether controlled breathing affects HRV measurement. We compared the effects of controlled breathing on HRV with those of spontaneous breathing. In 20 healthy volunteers, we measured respiratory frequency (f), tidal volume, and blood pressure (BP) and recorded electrocardiograms during spontaneous breathing (14.8 ± 0.7 breaths/min) and controlled breathing at 15 (0.25 Hz) and 6 (0.10 Hz) breaths/min. Compared to spontaneous breathing, controlled breathing at 0.25 Hz showed a higher heart rate and a lower high-frequency (HF) component, an index of parasympathetic nerve activity, although the f was the same. During controlled breathing at 0.10 Hz, the ratio of the low frequency (LF) to HF components (LF/HF), an index of sympathetic nerve activity, increased greatly and HF decreased, while heart rate and BP remained almost unchanged. Thus, controlled breathing at 0.25 Hz, which requires mental concentration, might inhibit parasympathetic nerve activity. During controlled breathing at 0.10 Hz, LF/HF increases because some HF subcomponents are synchronized with f and probably move into the LF band. This increment leads to misinterpretation of the true autonomic nervous regulation. We recommend that the respiratory pattern of participants should be evaluated before spectral HRV analysis to correctly understand changes in autonomic nervous regulation.

Preoperative therapy restores ventilatory parameters and reduces length of stay in patients undergoing myocardial revascularization / Fisioterapia pré-operatória restabelece parâmetros ventilatórios e reduz tempo de internação após revascularização do miocárdio

Introduction: The frequency of surgical procedures has increased steadily in recent decades, including the myocardial revascularization. Objectives: To demonstrate the importance of physiotherapy in the preoperative period of cardiac surgery in relation to the reduction of hospital stay, changes in lung volumes and respiratory muscle strength. Methods: We conducted a prospective study with patients undergoing myocardial revascularization, the Hospital das Clínicas da Universidade Estadual Paulista (UNESP)/Botucatu - SP. We evaluated 70 patients of both genders, aged between 40 and 75 years, subdivided into two groups: group I - 35 patients of both genders, who received a written protocol guidance, breathing exercises and respiratory muscle training in the preoperative period and group II - 35 patients of both genders, who received only orientation of the ward on the day of surgery. This study was approved by the Ethics Committee of UNESP / Botucatu - SP. Results: Maximal inspiratory pressure in third postoperative day and fifth postoperative day and significant difference between groups, being better for the intervention group. Expiratory pressure was significant in fifth postoperative day in the intervention group compared to controls. The difference of length of hospital stay in the postoperative was found between the groups with shorter hospital stay in the group receiving preoperative therapy. Conclusion: Physical therapy plays an important role in the preoperative period, so that individuals in the intervention group more readily restored the parameters evaluated before surgery, in addition, there was a decrease in the time of the postoperative hospital stay. Thus, it is thought the cost-effectiveness of a program of preoperative physiotherapy. .

Introdução: Procedimentos cirúrgicos aumentaram progressivamente nas últimas décadas, inclusive a revascularização do miocárdio(RM). Objetivos: Demonstrar a importância da fisioterapia no préoperatório de cirurgia cardíaca, em relação à redução do tempo de internação hospitalar, alteração de volumes pulmonares e força muscular respiratória. Métodos: Foi realizado estudo clínico prospectivo, com pacientes submetidos à revascularização do miocárdio, no Hospital das Clínicas da Universidade Estadual PaulistaUNESP / Botucatu - SP. Foram avaliados 70 pacientes de ambos os gêneros, com faixa etária entre 40 a 75 anos, randomizados por meio programa computadorizado em dois grupos: Grupo I - 35 pacientes de ambos os sexos, que receberam um protocolo de orientação por escrito, exercícios respiratórios e treinamento muscular respiratório no pré-operatório e Grupo II - 35 pacientes de ambos os gêneros, que receberam apenas orientação de rotina da enfermaria no dia da cirurgia. Trabalho foi aprovado pelo Comitê de Ética da Universidade Estadual PaulistaUNESP / Botucatu - SP. Resultados: A avaliação das pressões inspiratórias máximas evidenciou aumento significativo no terceiro dia pós-operatório e quinto dia pós-operatório para o grupo de intervenção e análise das pressões expiratórias máximas apresentou valores significativos apenas no quinto dia pós-operatório para o grupo intervenção em relação ao grupo controle, observando-se ainda que o grupo submetido ao protocolo de tratamento fisioterapêutico pré-operatório apresentou menor tempo de internação hospitalar. Conclusão: A fisioterapia ...

Acute effects of volume-oriented incentive spirometry on chest wall volumes in patients after a stroke.

BACKGROUND: The aim of the present study was to assess how volume-oriented incentive spirometry applied to patients after a stroke modifies the total and compartmental chest wall volume variations, including both the right and left hemithoraces, compared with controls. METHODS: Twenty poststroke patients and 20 age-matched healthy subjects were studied by optoelectronic plethysmography during spontaneous quiet breathing (QB), during incentive spirometry, and during the recovery period after incentive spirometry. RESULTS: Incentive spirometry was associated with an increased chest wall volume measured at the pulmonary rib cage, abdominal rib cage and abdominal compartment (P = .001) and under 3 conditions (P < .001). Compared with healthy control subjects, the tidal volume (VT) of the subjects with stroke was 24.7, 18.0, and 14.7% lower during QB, incentive spirometry, and postincentive spirometry, respectively. Under all 3 conditions, the contribution of the abdominal compartment to VT was greater in the stroke subjects (54.1, 43.2, and 48.9%) than in the control subjects (43.7, 40.8, and 46.1%, P = .039). In the vast majority of subjects (13/20 and 18/20 during QB and incentive spirometry, respectively), abdominal expansion precedes rib cage expansion during inspiration. Greater asymmetry between the right and left hemithoracic expansions occurred in stroke subjects compared with control subjects, but it decreased during QB (62.5%, P = .002), during incentive spirometry (19.7%), and postincentive spirometry (67.6%, P = .14). CONCLUSIONS: Incentive spirometry promotes increased expansion in all compartments of the chest wall and reduces asymmetric expansion between the right and left parts of the pulmonary rib cage; therefore, it should be considered as a tool for rehabilitation.

Follow your breath: respiratory interoceptive accuracy in experienced meditators.

Attention to internal bodily sensations is a core feature of mindfulness meditation. Previous studies have not detected differences in interoceptive accuracy between meditators and nonmeditators on heartbeat detection and perception tasks. We compared differences in respiratory interoceptive accuracy between meditators and nonmeditators in the ability to detect and discriminate respiratory resistive loads and sustain accurate perception of respiratory tidal volume during nondistracted and distracted conditions. Groups did not differ in overall performance on the detection and discrimination tasks; however, meditators were more accurate in discriminating the resistive load with the lowest ceiling effect. Meditators were also more accurate during the nondistracted tracking task at a lag time of 1 s following the breath. Results provide initial support for the notion that meditators have greater respiratory interoceptive accuracy compared to nonmeditators.

Different patterns of respiration in rat lines selectively bred for high or low anxiety.

In humans, there is unequivocal evidence of an association between anxiety states and altered respiratory function. Despite this, the link between anxiety and respiration has been poorly evaluated in experimental animals. The primary objective of the present study was to investigate the hypothesis that genetic lines of rats that differ largely in their anxiety level would display matching alterations in respiration. To reach this goal, respiration was recorded in high-anxiety behavior (HAB, n = 10) and low-anxiety behavior (LAB, n = 10) male rats using whole-body plethysmography. In resting state, respiratory rate was higher in HABs (85 ± 2 cycles per minute, cpm) than LABs (67 ± 2 cpm, p<0.05). During initial testing into the plethysmograph and during a restraint test, HAB rats spent less time at high-frequency sniffing compared to LAB rats. In addition, HAB rats did not habituate in terms of respiratory response to repetitive acoustic stressful stimuli. Finally, HAB rats exhibited a larger incidence of sighs during free exploration of the plethysmograph and under stress conditions. We conclude that: i) HAB rats showed respiratory changes (elevated resting respiratory rate, reduced sniffing in novel environment, increased incidence of sighs, and no habituation of the respiratory response to repetitive stimuli) that resemble those observed in anxious and panic patients, and ii) respiratory patterns may represent a promising way for assessing anxiety states in preclinical studies.

Inspiratory muscle training did not accelerate weaning from mechanical ventilation but did improve tidal volume and maximal respiratory pressures: a randomised trial.

QUESTION: Does inspiratory muscle training accelerate weaning from mechanical ventilation? Does it improve respiratory muscle strength, tidal volume, and the rapid shallow breathing index? DESIGN: Randomised trial with concealed allocation and intention-to-treat analysis. PARTICIPANTS: 92 patients receiving pressure support ventilation were included in the study and followed up until extubation, tracheostomy, or death. INTERVENTION: The experimental group received usual care and inspiratory muscle training using a threshold device, with a load of 40% of their maximal inspiratory pressure with a regimen of 5 sets of 10 breaths, twice a day, 7 days a week. The control group received usual care only. OUTCOME MEASURES: The primary outcome was the duration of the weaning period. The secondary outcomes were the changes in respiratory muscle strength, tidal volume, and the rapid shallow breathing index. RESULTS: Although the weaning period was a mean of 8 hours shorter in the experimental group, this difference was not statistically significant (95% CI -16 to 32). Maximal inspiratory and expiratory pressures increased in the experimental group and decreased in the control group, with significant mean differences of 10cmH2O (95% CI 5 to 15) and 8cmH2O (95% CI 2 to 13), respectively. The tidal volume also increased in the experimental group and decreased in the control group (mean difference 72 ml, 95% CI 17 to 128). The rapid shallow breathing index did not differ significantly between the groups. CONCLUSION: Inspiratory muscle training did not shorten the weaning period significantly but it increased respiratory muscle strength and tidal volume.

Treinamento muscular melhora o volume corrente e a capacidade vital no pós-operatório de revascularização do miocárdio / Inspiratory muscle training improves tidal volume and vital capacity after CABG surgery

OBJETIVO: Avaliar a função pulmonar e força da musculatura respiratória no período pós-operatório e verificar o efeito do treinamento muscular inspiratório sobre as medidas de desempenho da musculatura respiratória em pacientes submetidos à revascularização do miocárdio. MÉTODOS: Estudo randomizado, incluindo 47 pacientes submetidos à revascularização do miocárdio com circulação extracorpórea. Os pacientes foram divididos em grupo controle (GC), 24 pacientes, e grupo estudo (GE) 23 pacientes, com idade média de 66,33 ± 10,20 anos e 61,83 ± 8,61 anos, respectivamente. O GE foi submetido à fisioterapia convencional e ao treinamento muscular inspiratório com threshold® IMT e o GC à fisioterapia convencional. Foram comparadas as pressões respiratórias máximas (Pimáx e Pemáx), volume corrente (VC), capacidade vital (CV) e pico de fluxo expiratório (Peak Flow) no pré-operatório (Pré-OP), 1º e 3º dias de pós-operatório (PO1) e (PO3). RESULTADOS: Observou-se redução significativa em todas as variáveis mensuradas no PO1, quando comparadas ao pré-operatório, nos dois grupos estudados, Pimáx (P<0,0001), Pemáx (P<0,0001), VC: GE (P<0,0004) e GC: (P< 0,0001) e CV GE: (P<0,0001) e GC: (P<0,0001) e peak flow (P<0,0001). No PO3, o GE apresentou em comparação ao GC, maior valor de CV, GE 1230,4 ± 477,86 ml vs. GC 919,17 ± 394,47 ml (P= 0,0222) e VC GE 608,09 ± 178,24 ml vs. GC 506,96 ± 168,31 ml (P=0,0490). CONCLUSÃO: Pacientes submetidos à cirurgia cardíaca sofrem redução da CV e da força muscular respiratória após a cirurgia. O treinamento muscular realizado foi eficaz em recuperar o VC e a CV no PO3, no grupo treinado.

OBJECTIVE: To evaluate lung function and respiratory muscle strength in the postoperative period and investigate the effect of inspiratory muscle training on measures of respiratory muscle performance in patients undergoing coronary artery bypass grafting. METHODS: A randomized study with 47 patients undergoing coronary artery bypass grafting with cardiopulmonary bypass. They were divided into study group (SG) 23 patients and control group (CG) 24 patients, mean age 61.83 ± 8.61 and 66.33 ± 10.20 years, EuroSCORE SG 0.71 ± 0.0018 and CG 0.76 ± 0.0029, respectively. The study group underwent physical therapy and inspiratory muscle training with threshold IMT® and CG underwent conventional physiotherapy. We compared the maximal respiratory pressures (MIP and MEP), tidal volume (TV), vital capacity (VC) and peak expiratory flow (peak flow) preoperatively (Pre-OP), 1st (PO1) and 3rd (PO3) postoperative day. RESULTS: There was a significant reduction in all variables measured on PO1 compared to preoperative values in both groups, MIP (P <0.0001), MEP (P <0.0001), TV SG (P <0.0004) and CG (P <0.0001) and VC SG (P <0.0001) and CG (P <0.0001) and peak flow (P <0.0001). At PO3, SG presented higher value of VC, GE 1230.4 ± 477.86 ml vs. GC 919.17 ± 394.47 ml (P=0.0222) and TV SG 608.09 ± 178.24 ml vs. CG 506.96 ± 168.31 ml (P= 0.0490). CONCLUSION: Patients undergoing cardiac surgery experience reduced ventilatory capacity and respiratory muscle strength after surgery. Muscle training was performed to retrieve TV and VC in the PO3, in the trained group.