Dyspnea

Detection and perception of inspiratory resistive loads in older adults with and without chronic obstructive pulmonary disease

Impairments in the detection and perception of resistive loads in healthy aging and chronic obstructive pulmonary disease (COPD) have implications for airway protection and breathlessness. This study investigated load detection and perception in 18 participants with COPD, 17 older adults [i.e., age-matched controls (AMCs)] and 23 young adults [i.e., young controls (YCs)]. Load detection was assessed as the minimal change in airway resistance that could be detected and load perception as the perceived level of effort to breathe through a series of suprathreshold resistive loads, rated on a modified Borg scale. Young and older adults, with and without COPD, could detect similar changes in resistance (∼0.7 cmH2O/L/s) and inspiratory pressure (∼0.5 cmH2O), although this equated to a smaller proportion of predicted maximal inspiratory pressure (MIPpred) for young adults (∼0.5% MIPpred) compared with older adults with and without COPD (∼1.0% MIPpred; P < 0.001). For load perception, the relationship between Borg ratings and resistance was steeper in older adult controls compared with both young adults (P < 0.001) and older adults with COPD (P < 0.01). Borg rating slopes were comparable across all participant groups with changes in inspiratory pressure. There was no correlation between load detection threshold and load perception. In older adults, heightened perception of loaded breaths with large changes in breathing resistance may be due to an increased effort to breathe at these loads.NEW & NOTEWORTHY We demonstrated that young adults could detect a smaller change in pressure (as a proportion of predicted maximal inspiratory pressure) than older adults. The perceived effort to breathe with increases in the resistance of breathing was heightened in older, compared with young adults. There was no further impairment in chronic obstructive pulmonary disease. Heightened dyspnea perception related to the effort to breathe was not associated with load detection thresholds in older adults.

The occurrence mechanism, assessment, and non-pharmacological treatment of dyspnea

Dyspnea is a subjective sensation often described as a feeling of respiratory effort, tightness, or air hunger. The underlying mechanisms of this symptom are multifaceted and involve factors such as respiratory centers, cardiovascular system, airways, neuromuscular components, and metabolic factors, although not fully elucidated. The classical theory of imbalance between inspiratory neural drive (IND) and the simultaneous dynamic responses of the respiratory system posits that the disruption of a normal and harmonious relationship fundamentally shapes the expression of respiratory discomfort. Assessment and comprehensive treatment of dyspnea are crucial for patient rehabilitation, including subjective self-reporting and objective clinical measurements. Non-pharmacological interventions, such as pulmonary rehabilitation, fan therapy, exercise, chest wall vibration, virtual reality technology, traditional Chinese medicine (acupuncture and acupressure), and yoga, have shown promise in alleviating dyspnea symptoms. Additionally, oxygen therapy, has demonstrated short-term benefits for patients with pre-hospital respiratory distress and hypoxemia. This review provides a comprehensive overview of dyspnea, emphasizing the importance of a multifaceted approach for its assessment and management, with a focus on non-pharmacological interventions that contribute to enhanced patient outcomes and quality of life.

Proposed Clinical Algorithm for Pleuroparenchymal Fibroelastosis (PPFE)

Pleuroparenchymal fibroelastosis (PPFE) is characterized by fibrosis involving the pleura and subpleural lung parenchyma, predominantly in the upper lobes. As PPFE appears to occur in patients with heterogeneous etiologies, the disease course is thus also heterogenous, with some patients showing rapid progression while others have slow progression. Therefore, it is very difficult to predict prognosis with PPFE. Needless to say, this problematic matter has influenced the treatment strategy of PPFE patients. In fact, until now no evidence has been shown for use in creating an appropriate management algorithm for PPFE. We speculate that "uncoordinated breathing" is the most important reason for dyspnea in PPFE patients. Because monitoring of physique and not just pulmonary function and radiological evaluation is also very important, particularly in PPFE patients, this review focused on the characteristics of PPFE through an overview of previous studies in this field, and we proposed an algorithm as precision medicine based on the current evidence. Multiple views by the pulmonologist are needed to standardize a clinical algorithm that is necessary to correctly assess PPFE patients under the premise of maintenance of physique by providing appropriate nutritional care and pulmonary rehabilitation.

Research progress on the pathogenesis of chest tightness variant asthma characterized by chest tightness

Chest tightness variant asthma (CTVA) is an atypical form of asthma with chest tightness as the sole or predominant symptom. The underlying receptors for chest tightness are bronchial C-fibers or rapidly adapting receptors. The nerve impulses are transmitted via the vagus nerve and processed in different regions of the cerebral cortex. Chest tightness is associated with sensory perception, and CTVA patients may have heightened ability to detect subtle changes in lung function, but such sensory perception is unrelated to respiratory muscle activity, lung hyperinflation, or mechanical loading of the respiratory system. Airway inflammation, pulmonary ventilation dysfunction (especially involving small airways), and airway hyperresponsiveness may underlie the sensation of chest tightness. CTVA patients are prone to comorbid anxiety and depression, which share similar central nervous system processing pathways with dyspnea, suggesting a possible neurological basis for the development of CTVA. This article examines the recognition and mechanisms of chest tightness, and explores the pathogenesis of CTVA, focusing on its association with airway inflammation, ventilation dysfunction, airway hyperresponsiveness, and psychosocial factors.

Multiple sensor theory in airway mechanosensory units

Two conventional doctrines govern airway mechanosensory interpretation: One-Sensor Theory (OST) and Line-Labeled Theory (LLT). In OST, one afferent fiber connects to a single sensor. In LLT, a different type of sensor sends signals via its specific line to a particular brain region to evoke its reflex. Thus, airway slowly adapting receptors (SARs) inhibit breathing and rapidly adapting receptors (RARs) stimulate breathing. However, recent studies show many different mechanosensors connect to a single afferent fiber (Multiple-Sensor Theory, MST). That is, SARs and RARs may send different types of information through the same afferent pathway, indicating different information has been integrated at the sensory unit level. Thus, a sensory unit is not merely a transducer (textbook concept), but also a processor. MST is a conceptual shift. Data generated over last eight decades under OST require re-interpretation.