Dyspnea: Don't Just Look, Ask!

Excess ventilation and exertional dyspnoea in heart failure and pulmonary hypertension

Increased ventilation relative to metabolic demands, indicating alveolar hyperventilation and/or increased physiological dead space (excess ventilation), is a key cause of exertional dyspnoea. Excess ventilation has assumed a prominent role in the functional assessment of patients with heart failure (HF) with reduced (HFrEF) or preserved (HFpEF) ejection fraction, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). We herein provide the key pieces of information to the caring physician to 1) gain unique insights into the seeds of patients' shortness of breath and 2) develop a rationale for therapeutically lessening excess ventilation to mitigate this distressing symptom. Reduced bulk oxygen transfer induced by cardiac output limitation and/or right ventricle-pulmonary arterial uncoupling increase neurochemical afferent stimulation and (largely chemo-) receptor sensitivity, leading to alveolar hyperventilation in HFrEF, PAH and small-vessel, distal CTEPH. As such, interventions geared to improve central haemodynamics and/or reduce chemosensitivity have been particularly effective in lessening their excess ventilation. In contrast, 1) high filling pressures in HFpEF and 2) impaired lung perfusion leading to ventilation/perfusion mismatch in proximal CTEPH conspire to increase physiological dead space. Accordingly, 1) decreasing pulmonary capillary pressures and 2) mechanically unclogging larger pulmonary vessels (pulmonary endarterectomy and balloon pulmonary angioplasty) have been associated with larger decrements in excess ventilation. Exercise training has a strong beneficial effect across diseases. Addressing some major unanswered questions on the link of excess ventilation with exertional dyspnoea under the modulating influence of pharmacological and nonpharmacological interventions might prove instrumental to alleviate the devastating consequences of these prevalent diseases.

Relationships between self-reported dyspnea, health conditions and frailty among Brazilian community-dwelling older adults: a cross-sectional study

CONTEXT

Dyspnea is a symptom present in several chronic diseases commonly seen among older adults. Since individuals with dyspnea tend to stay at rest, with consequently reduced levels of physical activity, they are likely to be at greater risk of developing frailty, especially at older ages.

DESIGN AND SETTING

Cross-sectional study at community level, Brazil.

OBJECTIVE

To analyze the relationships between self-reported dyspnea, health conditions and frailty status in a sample of community-dwelling older adults.

METHOD

Secondary data from the follow-up of the Frailty in Brazilian Elderly (FIBRA) study, involving 415 community-dwelling older adults (mean age: 80.3 ± 4.68 years), were used. The variables analyzed were sociodemographic characteristics, reported dyspnea, clinical data and frailty phenotype. Associations between dyspnea and other variables (age, sex, education and body mass index) were verified through the crude (c) and adjusted (a) odds ratios.

RESULTS

The prevalence of dyspnea in the entire sample was 21.0%. Dyspnea was more present in individuals with pulmonary diseases, heart disease, cancer and depression. Older adults with multimorbidities (adjusted odds ratio, ORa = 2.91; 95% confidence interval, CI = 1.41-5.99) and polypharmacy (ORa = 2.02; 95% CI = 1.15-3.54) were more likely to have dyspnea. Those who reported dyspnea were 2.54 times more likely to be frail (ORa = 2.54; 95% CI = 1.08-5.97), and fatigue was their most prevalent phenotype component.

CONCLUSION

Dyspnea was associated with different diseases, multimorbidities, polypharmacy and frailty. Recognizing the factors associated with dyspnea may contribute to its early identification and prevention of its negative outcomes among older adults.

Dyspnea

The clinical term dyspnea (a.k.a. breathlessness or shortness of breath) encompasses at least three qualitatively distinct sensations that warn of threats to breathing: air hunger, effort to breathe, and chest tightness. Air hunger is a primal homeostatic warning signal of insufficient alveolar ventilation that can produce fear and anxiety and severely impacts the lives of patients with cardiopulmonary, neuromuscular, psychological, and end-stage disease. The sense of effort to breathe informs of increased respiratory muscle activity and warns of potential impediments to breathing. Most frequently associated with bronchoconstriction, chest tightness may warn of airway inflammation and constriction through activation of airway sensory nerves. This chapter reviews human and functional brain imaging studies with comparison to pertinent neurorespiratory studies in animals to propose the interoceptive networks underlying each sensation. The neural origins of their distinct sensory and affective dimensions are discussed, and areas for future research are proposed. Despite dyspnea's clinical prevalence and impact, management of dyspnea languishes decades behind the treatment of pain. The neurophysiological bases of current therapeutic approaches are reviewed; however, a better understanding of the neural mechanisms of dyspnea may lead to development of novel therapies and improved patient care.

Update in Critical Care 2015

This review documents important progress made in 2015 in the field of critical care. Significant advances in 2015 included further evidence for early implementation of low tidal volume ventilation as well as new insights into the role of open lung biopsy, diaphragmatic dysfunction, and a potential mechanism for ventilator-induced fibroproliferation. New therapies, including a novel low-flow extracorporeal CO2 removal technique and mesenchymal stem cell-derived microparticles, have also been studied. Several studies examining the role of improved diagnosis and prevention of ventilator-associated pneumonia also showed relevant results. This review examines articles published in the American Journal of Respiratory and Critical Care Medicine and other major journals that have made significant advances in the field of critical care in 2015.

The breath of life. Patients' experiences of breathing during and after mechanical ventilation

INTRODUCTION

Breathlessness is a prevalent and distressing symptom in intensive care, underestimated by nurses and physicians. Therefore, to develop a more comprehensive understanding of this problem, the study had two aims: to compare patients' self-reported scores of breathlessness obtained during mechanical ventilation (MV) with experiences of breathlessness later recalled by patients and: to explore the lived experience of breathing during and after MV.

METHOD

A qualitatively driven sequential mixed method design combining prospective observational breathlessness data at the end of a spontaneous breathing trial (SBT) and follow up data from 11 post-discharge interviews.

FINDINGS

Four out of six patients who reported breathlessness at the end of an SBT did not remember being breathless in retrospect. Experiences of breathing intertwined with the whole illness experience and were described in four themes: existential threat; the tough time; an amorphous and boundless body and getting through.

CONCLUSION

Breathing was not always a clearly separate experience, but intertwined with the whole illness experience. This may explain the poor correspondence between patients' and clinicians assessments of breathlessness. The results suggest patients' own reports of breathing should form part of nursing interventions and follow-up to support patients' quest for meaning.

Validity of a Self-administered Questionnaire Version of the Transition Dyspnea Index in Patients with COPD

The transition dyspnea index (TDI) is among the most widely used instruments in chronic obstructive pulmonary disease (COPD) patients to measure changes in dyspnea over time. In its original version it is used as guideline for a structured interview to assess the impact of daily activities on dyspnea in the three subdomains: functional impairment, magnitude of task, and magnitude of effort. However, the TDI is sometimes used as a self-administered paper-and-pencil questionnaire. The validity of this questionnaire format has not been tested, which was the aim of the present study. We tested 190 patients with COPD at start and end of a 3-week inpatient pulmonary rehabilitation program (PR). Dyspnea was assessed with the modified Medical Research Council Scale (mMRC), a questionnaire version of the TDI, and an interview version of the TDI. Group means for the TDI questionnaire and interview version were widely comparable for the TDI summary score and the three TDI subdomains. The scores of both TDI versions were strongly correlated and showed comparable, but only weak, correlations with changes during PR in spirometric lung function and mMRC. Improvement in dyspnea after PR was observed in 89% of patients when using the summary score of the questionnaire TDI, but only in 34% of patients when using the mMRC. The results suggest that a self-administered questionnaire format of the TDI is an adequate instrument for assessing changes in activity-related dyspnea during PR in patients with COPD. The responsiveness of this instrument to effects of PR appears greater than the responsiveness of the mMRC.

Continuous Positive Airway Pressure and Breathlessness in Obese Patients with Obstructive Sleep Apnea: A Pilot Study

STUDY OBJECTIVES

Continuous positive airway pressure (CPAP) is an effective treatment for obstructive sleep apnea (OSA). However, long-term compliance with CPAP is limited. We tested the hypothesis that CPAP levels routinely used during sleep increase neural respiratory drive (NRD) and breathlessness, which may discourage compliance.

METHODS

This was an observational physiological cohort study in a respiratory physiology and sleep unit, University Hospital. Patients with a body mass index (BMI) > 25 kg/m(2) and confirmed OSA were studied supine and awake on CPAP (4-20 cm H2O, increments of 2 cm H2O/3 min). We measured NRD during awake CPAP titration in obese subjects to quantify the response to the load of the respiratory system and compared it to the CPAP used for nocturnal treatment, with the modified Borg Scale (mBorg) for dyspnea recorded (from 0 to 10 points, with higher numbers indicating more breathlessness).

RESULTS

Fifteen patients (age 48 ± 10 years, 12 male, BMI 38.9 ± 5.8 kg/m(2)) with OSA (AHI 32.2 ± 21.1/h, 95(th) percentile of CPAP 14.1 ± 3.8 cm H2O) were studied and NRD (electromyogram of the parasternal intercostals, EMGpara; EMG of the external oblique, EMGabdomen) was recorded (awake, supine). Awake, EMGpara declined from baseline to 70.2% ± 17.1% when CPAP of 10.7 ± 3.4 cm H2O (P = 0.026) was applied. Further increase in CPAP led to a rise in EMGpara and increased breathlessness (P = 0.02). CPAP compliance (nights used) correlated negatively with mBorg scores (r = -0.738, P = 0.006).

CONCLUSIONS

Awake, the respiratory system is maximally offloaded with lower than therapeutic CPAP levels in obese patients with OSA. Levels of NRD observed at effective CPAP levels while asleep are associated with breathlessness which may limit long-term CPAP compliance.