Mechanisms to dyspnoea and dynamic hyperinflation related exercise intolerance in COPD

Expiratory flow limitation can develop in parallel with the progression of COPD, and as a consequence, dynamic hyperinflation and lung mechanical abnormalities can develop. Dynamic hyperinflation can cause increased breathlessness and reduction in exercise tolerance. Achievement of critical inspiratory reserve volume is one of the main factors in exercise intolerance. Obesity has specific lung mechanical effects. There is also a difference concerning gender and dyspnoea. Increased nerve activity is characteristic in hyperinflation. Bronchodilator therapy, lung volume reduction surgery, endurance training at submaximal intensity, and heliox or oxygen breathing can decrease the degree of dynamic hyperinflation

Pathogenesis of hyperinflation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a preventable and treatable lung disease characterized by airflow limitation that is not fully reversible. In a significant proportion of patients with COPD, reduced lung elastic recoil combined with expiratory flow limitation leads to lung hyperinflation during the course of the disease. Development of hyperinflation during the course of COPD is insidious. Dynamic hyperinflation is highly prevalent in the advanced stages of COPD, and new evidence suggests that it also occurs in many patients with mild disease, independently of the presence of resting hyperinflation. Hyperinflation is clinically relevant for patients with COPD mainly because it contributes to dyspnea, exercise intolerance, skeletal muscle limitations, morbidity, and reduced physical activity levels associated with the disease. Various pharmacological and nonpharmacological interventions have been shown to reduce hyperinflation and delay the onset of ventilatory limitation in patients with COPD. The aim of this review is to address the more recent literature regarding the pathogenesis, assessment, and management of both static and dynamic lung hyperinflation in patients with COPD. We also address the influence of biological sex and obesity and new developments in our understanding of hyperinflation in patients with mild COPD and its evolution during progression of the disease

Effect of the expiratory positive airway pressure on dynamic hyperinflation and exercise capacity in patients with COPD: a meta-analysis

Expiratory positive airway pressure (EPAP) is widely applicable, either as a strategy for pulmonary reexpansion, elimination of pulmonary secretion or to reduce hyperinfation. However, there is no consensus in the literature about the real benefts of EPAP in reducing dynamic hyperinfation (DH) and increasing exercise tolerance in subjects with chronic obstructive pulmonary disease (COPD). To systematically review the efects of EPAP application during the submaximal stress test on DH and exercise capacity in patients with COPD. This meta-analysis was performed from a systematic search in the PubMed, EMBASE, PeDRO, and Cochrane databases, as well as a manual search. Studies that evaluated the efect of positive expiratory pressure on DH, exercise capacity, sensation of dyspnea, respiratory rate, peripheral oxygen saturation, sense of efort in lower limbs, and heart rate were included. GRADE was used to determine the quality of evidence for each outcome. Of the 2,227 localized studies, seven studies were included. The results show that EPAP did not change DH and reduced exercise tolerance in the constant load test. EPAP caused a reduction in respiratory rate after exercise (− 2.33 bpm; 95% CI: − 4.56 to− 0.10) (very low evidence) when using a pressure level of 5 cmH2O. The other outcomes analyzed were not signifcantly altered by the use of EPAP. Our study demonstrates that the use of EPAP does not prevent the onset of DH and may reduce lower limb exercise capacity in patients with COPD. However, larger and higher-quality studies are needed to clarify the potential beneft of EPAP in this population

Effect of external PEEP in patients under controlled mechanical ventilation with an auto-PEEP of 5 cmH2O or higher.

In some patients with auto-positive end-expiratory pressure (auto-PEEP), application of PEEP lower than auto-PEEP maintains a constant total PEEP, therefore reducing the inspiratory threshold load without detrimental cardiovascular or respiratory effects. We refer to these patients as complete PEEP-absorbers. Conversely, adverse effects of PEEP application could occur in patients with auto-PEEP when the total PEEP rises as a consequence. From a pathophysiological perspective, all subjects with flow limitation are expected to be complete PEEP-absorbers, whereas PEEP should increase total PEEP in all other patients. This study aimed to empirically assess the extent to which flow limitation alone explains a complete PEEP-absorber behavior (i.e., absence of further hyperinflation with PEEP), and to identify other factors associated with it.One hundred patients with auto-PEEP of at least 5 cmH2O at zero end-expiratory pressure (ZEEP) during controlled mechanical ventilation were enrolled. Total PEEP (i.e., end-expiratory plateau pressure) was measured both at ZEEP and after applied PEEP equal to 80 % of auto-PEEP measured at ZEEP. All measurements were repeated three times, and the average value was used for analysis.Forty-seven percent of the patients suffered from chronic pulmonary disease and 52 % from acute pulmonary disease; 61 % showed flow limitation at ZEEP, assessed by manual compression of the abdomen. The mean total PEEP was 7 ± 2 cmH2O at ZEEP and 9 ± 2 cmH2O after the application of PEEP (p < 0.001). Thirty-three percent of the patients were complete PEEP-absorbers. Multiple logistic regression was used to predict the behavior of complete PEEP-absorber. The best model included a respiratory rate lower than 20 breaths/min and the presence of flow limitation. The predictive ability of the model was excellent, with an overoptimism-corrected area under the receiver operating characteristics curve of 0.89 (95 % CI 0.80-0.97).Expiratory flow limitation was associated with both high and complete PEEP-absorber behavior, but setting a relatively high respiratory rate on the ventilator can prevent from observing complete PEEP-absorption. Therefore, the effect of PEEP application in patients with auto-PEEP can be accurately predicted at the bedside by measuring the respiratory rate and observing the flow-volume loop during manual compression of the abdomen

Effect of portable noninvasive ventilation on thoracoabdominal volumes in recovery from intermittent exercise in patients with COPD

We previously showed that use of portable noninvasive ventilation (pNIV) during recovery periods within intermittent exercise improved breathlessness and exercise tolerance in patients with COPD compared with pursed-lip breathing (PLB). However, in a minority of patients recovery from dynamic hyperinflation (DH) was better with PLB, based on inspiratory capacity. We further explored this using Optoelectronic Plethysmography to assess total and compartmental thoracoabdominal volumes. Fourteen patients with COPD (means ± SD) (FEV1: 55% ± 22% predicted) underwent, in a balanced order sequence, two intermittent exercise protocols on the cycle ergometer consisting of five repeated 2-min exercise bouts at 80% peak capacity, separated by 2-min recovery periods, with application of pNIV or PLB in the 5 min of recovery. Our findings identified seven patients showing recovery in DH with pNIV (DH responders) whereas seven showed similar or better recovery in DH with PLB. When pNIV was applied, DH responders compared with DH nonresponders exhibited greater tidal volume (by 0.8 ± 0.3 L, P = 0.015), inspiratory flow rate (by 0.6 ± 0.5 L/s, P = 0.049), prolonged expiratory time (by 0.6 ± 0.5 s, P = 0.006), and duty cycle (by 0.7 ± 0.6 s, P = 0.007). DH responders showed a reduction in end-expiratory thoracoabdominal DH (by 265 ± 633 mL) predominantly driven by reduction in the abdominal compartment (by 210 ± 494 mL); this effectively offset end-inspiratory rib-cage DH. Compared with DH nonresponders, DH responders had significantly greater body mass index (BMI) by 8.4 ± 3.2 kg/m2, P = 0.022 and tended toward less severe resting hyperinflation by 0.3 ± 0.3 L. Patients with COPD who mitigate end-expiratory rib-cage DH by expiratory abdominal muscle recruitment benefit from pNIV application

Effects of portable non-invasive ventilation on exercise tolerance in patients with COPD

Breathlessness is the dominant symptom that limits exercise tolerance in patients with COPD. Several ergogenic approaches have been employed to improve exercise tolerance in this population including bronchodilators, oxygen and heliox supplementation, intermittent exercise and non-invasive ventilation (NIV). Although application of NIV during exercise is beneficial for increasing exercise capacity in patients with COPD, there are several disadvantages that limit its wider application during exercise, including lack of compliance with the equipment, and the time required to set up and supervise the equipment in the setting of pulmonary rehabilitation. Recent advances in technology have facilitated the development of portable non-invasive ventilation (pNIV) devices aiming to alleviate breathlessness during activities of daily living. The VitaBreath (Philips, Respironics) was developed in 2016 as a portable, handheld, battery powered, bi-level, NIV device, providing fixed positive inspiratory and expiratory airway pressure support (IPAP:18 and EPAP: 8 cmH2O, respectively). Accordingly, this dissertation aimed to investigate the physiological effects of pNIV application during controlled laboratory exercise conditions and activities of daily living, in patients with advanced COPD. As the VitaBreath device is no longer commercially available, but similar devices may come to market, the present dissertation provides proof of concept on how pNIV can be applied intermittently during exercise in patients with COPD, and how to select patients most likely to respond to pNIV. This in turn may encourage the development of more suitable devices. Intermittent exercise was chosen to evaluate the effects of pNIV in comparison to the commonly adopted pursed lip breathing (PLB) technique, as this type of exercise allowed regular application of the pNIV device or the PLB technique during recovery periods. Patients retained the device for 3 months to investigate the acceptability, comfort and usability of the device during activities of daily living. Twenty-four COPD patients were randomised to perform two intermittent exercise protocols sustained at different work intensities (60% WRpeak for 6-min and 80% WRpeak for 2-min) alternated with 2-min rest periods. Within each intermittent exercise modality, patients performed two identical exercise tests using either pNIV or the PLB technique in a balanced order sequence, during the recovery phases of intermittent exercise. The findings of this study showed that with both intermittent protocols average endurance time was greater when pNIV was applied compared to PLB. Improvements in exercise tolerance were due to lower degrees of dynamic hyperinflation (DH) and breathlessness with pNIV compared to PLB. An important finding of the aforementioned study was that a subgroup of patients (8/24) failed to show a clinical important improvement in DH with pNIV compared to PLB and did not improve exercise tolerance. Analysis identified that these 8 patients experienced greater resting lung hyperinflation, greater exercise-induced DH and breathlessness, secondary to the adoption of a tachypnoeic breathing pattern with pNIV compared to PLB. Interestingly, these patients also reported less benefit from using the device at home, in terms of anxiety around breathlessness and recovery time from breathlessness. Considering the variation of response reported in the present thesis it is important that clinicians assess the response to pNIV on an individual basis. As with any new method, it was important to appreciate the physiological consequences of the acute application of pNIV on thoracoabdominal volume regulation and respiratory muscle recruitment (assessed by optoelectronic plethysmography), and central hemodynamic responses. Compared to PLB, acute application of pNIV was associated, in the majority of patients, with increased end-inspiratory and end-expiratory rib cage volumes and greater rib cage muscle recruitment, as well as decreased end-expiratory abdominal volumes reflecting reduced expiratory abdominal recruitment. Measurement of cardiac output revealed no adverse circulatory responses with the application of positive airway pressures provided by pNIV during the recovery periods. However, the pattern of thoracoabdominal volume regulation and respiratory muscle kinematics confirmed the findings of the original studies, thereby identifying responders and non-responders to pNIV. Interestingly, responders to pNIV exhibited greater recruitment of the expiratory abdominal muscles compared to non-responders, thereby facilitating them to combat end-expiratory rib cage dynamic hyperinflation effectively. When patients used the VitaBreath device during their daily physical activities, the majority of patients felt less anxious about becoming breathless and felt that their breathlessness recovered faster when using the device at home for 3 months. Moreover, almost all patients used the device at least weekly and all patients rated the ease of VitaBreath use to be between good and excellent. Additionally, most patients felt that using the device had benefited them and that they would recommend the device to other patients. The main disadvantage of the device was reported to be the high cost and its portability. The pNIV method provided fixed IPAP and EPAP. This represents a very important disadvantage of this particular pNIV device, which clearly mitigated the beneficial impact it had on some patients. Future research into pNIV devices should examine how best to identify patients who benefit from a pNIV method in everyday life. On-going development of auto-adjusted ventilators would facilitate a larger fraction of COPD patients to be physically active and experience a better quality of life

Lung volumes identify an at-risk group in persons with prolonged secondhand tobacco smoke exposure but without overt airflow obstruction.

IntroductionExposure to secondhand smoke (SHS) is associated with occult obstructive lung disease as evident by abnormal airflow indices representing small airway disease despite having preserved spirometry (normal forced expiratory volume in 1 s-to-forced vital capacity ratio, FEV1/FVC). The significance of lung volumes that reflect air trapping in the presence of preserved spirometry is unclear.MethodsTo investigate whether lung volumes representing air trapping could determine susceptibility to respiratory morbidity in people with SHS exposure but without spirometric chronic obstructive pulmonary disease, we examined a cohort of 256 subjects with prolonged occupational SHS exposure and preserved spirometry. We elicited symptom prevalence by structured questionnaires, examined functional capacity (maximum oxygen uptake, VO2max) by exercise testing, and estimated associations of those outcomes with air trapping (plethysmography-measured residual volume-to-total lung capacity ratio, RV/TLC), and progressive air trapping with exertion (increase in fraction of tidal breathing that is flow limited on expiration during exercise (per cent of expiratory flow limitation, %EFL)).ResultsRV/TLC was within the predicted normal limits, but was highly variable spanning 22%±13% and 16%±8% across the increments of FEV1/FVC and FEV1, respectively. Respiratory complaints were prevalent (50.4%) with the most common symptom being ≥2 episodes of cough per year (44.5%). Higher RV/TLC was associated with higher OR of reporting respiratory symptoms (n=256; r2=0.03; p=0.011) and lower VO2max (n=179; r2=0.47; p=0.013), and %EFL was negatively associated with VO2max (n=32; r2=0.40; p=0.017).ConclusionsIn those at risk for obstruction due to SHS exposure but with preserved spirometry, higher RV/TLC identifies a subgroup with increased respiratory symptoms and lower exercise capacity

Effects of the components of positive airway pressure on work of breathing during bronchospasm

INTRODUCTION: Partial assist ventilation reduces work of breathing in patients with bronchospasm; however, it is not clear which components of the ventilatory cycle contribute to this process. Theoretically, expiratory positive airway pressure (EPAP), by reducing expiratory breaking, may be as important as inspiratory positive airway pressure (IPAP) in reducing work of breathing during acute bronchospasm. METHOD: We compared the effects of 10 cmH(2)O of IPAP, EPAP, and continuous positive airwaypressure (CPAP) on inspiratory work of breathing and end-expiratory lung volume (EELV) in a canine model of methacholine-induced bronchospasm. RESULTS: Methacholine infusion increased airway resistance and work of breathing. During bronchospasm IPAP and CPAP reduced work of breathing primarily through reductions in transdiaphragmatic pressure per tidal volume (from 69.4 ± 10.8 cmH(2)O/l to 45.6 ± 5.9 cmH(2)O/l and to 36.9 ± 4.6 cmH(2)O/l, respectively; P < 0.05) and in diaphragmatic pressure–time product (from 306 ± 31 to 268 ± 25 and to 224 ± 23, respectively; P < 0.05). Pleural pressure indices of work of breathing were not reduced by IPAP and CPAP. EPAP significantly increased all pleural and transdiaphragmatic work of breathing indices. CPAP and EPAP similarly increased EELV above control by 93 ± 16 ml and 69 ± 12 ml, respectively. The increase in EELV by IPAP of 48 ± 8 ml (P < 0.01) was significantly less than that by CPAP and EPAP. CONCLUSION: The reduction in work of breathing during bronchospasm is primarily induced by the IPAP component, and that for the same reduction in work of breathing by CPAP, EELV increases more

Physiopathological rationale of using high-flow nasal therapy in the acute and chronic setting: A narrative review

Chronic lung disease and admissions due to acute respiratory failure (ARF) are becoming increasingly common. Consequently, there is a growing focus on optimizing respiratory support, particularly non-invasive respiratory support, to manage these conditions. High flow nasal therapy (HFNT) is a noninvasive technique where humidified and heated gas is delivered through the nose to the airways via small dedicated nasal prongs at flows that are higher than the rates usually applied during conventional oxygen therapy. HFNT enables to deliver different inspired oxygen fractions ranging from 0.21 to 1. Despite having only recently become available, the use of HFNT in the adult population is quite widespread in several clinical settings. The respiratory effects of HNFT in patients with respiratory failure may be particularly relevant for clinicians. In this narrative review, we discuss the main pathophysiological mechanism and rationale for using HFNT in the acute and chronic setting