THE EFFECT OF AIR FLOW AND ORAL PRESSURE ON THE MECHANICS OF BREATHING IN PATIENTS WITH ASTHMA AND EMPHYSEMA

Control of the expiratory flow in a lung model and in healthy volunteers with an adjustable flow regulator: a combined bench and randomized crossover study

Background

Pursed-lips breathing (PLB) is a technique to attenuate small airway collapse by regulating the expiratory flow. During mandatory ventilation, flow-controlled expiration (FLEX), which mimics the expiratory flow course of PLB utilizing a digital system for measurement and control, was shown to exert lung protective effects. However, PLB requires a patient’s participation and coordinated muscular effort and FLEX requires a complex technical setup. Here, we present an adjustable flow regulator to mimic PLB and FLEX, respectively, without the need of a patient’s participation, or a complex technical device.

Methods

Our study consisted of two parts: First, in a lung model which was ventilated with standard settings (tidal volume 500 ml, respiratory rate 12 min⁻¹, positive end-expiratory pressure (PEEP) 5 cmH₂O), the possible reduction of the maximal expiratory flow by utilizing the flow regulator was assessed. Second, with spontaneously breathing healthy volunteers, the short-term effects of medium and strong expiratory flow reduction on airway pressure, the change of end-expiratory lung volume (EELV), and breathing discomfort was investigated.

Results

In the lung model experiments, expiratory flow could be reduced from − 899 ± 9 ml·s⁻¹ down to − 328 ± 25 ml·s⁻¹. Thereby, inspiratory variables and PEEP were unaffected. In the volunteers, the maximal expiratory flow of − 574 ± 131 ml·s⁻¹ under baseline conditions was reduced to − 395 ± 71 ml·s⁻¹ for medium flow regulation and to − 266 ± 58 ml·s⁻¹ for strong flow regulation, respectively (p < 0.001). Accordingly, mean airway pressure increased from 0.6 ± 0.1 cmH₂O to 2.9 ± 0.4 cmH₂O with medium flow regulation and to 5.4 ± 2.4 cmH₂O with strong flow regulation, respectively (p < 0.001). The EELV increased from baseline by 31 ± 458 ml for medium flow regulation and 320 ± 681 ml for strong flow regulation (p = 0.033). The participants rated breathing with the flow regulator as moderately uncomfortable, but none rated breathing with the flow regulator as intolerable.

Conclusions

The flow regulator represents an adjustable device for application of a self-regulated expiratory resistive load, representing an alternative for PLB and FLEX. Future applications in spontaneously breathing patients and patients with mandatory ventilation alike may reveal potential benefits.

Trial registration: DRKS00015296, registered on 20th August, 2018; URL: https://www.drks.de/drks_web/setLocale_EN.do.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01886-7.

The physiological rationale of heat and moisture exchangers in post-laryngectomy pulmonary rehabilitation: a review

Total laryngectomy results in a permanent disconnection of the upper and lower airways and inevitably leads to chronic pulmonary complaints like frequent involuntary coughing, increased sputum production and repeated daily forced expectoration to clean the airway. Heat and moisture exchangers (HMEs), applied in an attempt to compensate for the lost functions of the upper respiratory tract, have been found to diminish these symptoms and improve the quality of life significantly. An HME has three physical properties that might be responsible for these improvements. First, its heat and moisture exchanging capacity improves intra-airway preservation of heat and water. Since the condensation and evaporation of moisture are accompanied by the release and uptake of thermal energy, these parameters are inseparable. Secondly, the HME's resistance may reduce dynamic airway compression, thereby improving ventilation. Thirdly, to some extent, an HME might filter out particles, thereby cleaning inspiratory breathing air. This article summarizes our present knowledge of changes in respiratory physiology after total laryngectomy and the influence of the HME by reviewing the physiological impact of these three physical properties separately for in vitro and in vivo data.

Dyspnea: a sensory experience

Dyspnea--an unpleasant or uncomfortable awareness of breathing or need to breathe--is a common symptom of patients with cardiopulmonary disease. Although often thought of as a single symptom, dyspnea probably subsumes many sensations. Experimental conditions used to induce dyspnea are characterized by discrete groups or clusters of descriptive phrases. Similarly, as the language of dyspnea is refined further, different disease states may be distinguishable by the nuances of breathlessness described by patients. Evidence is gathering that the sensations of dyspnea are modified by information from a variety of receptors throughout the respiratory system. The sense of effort, although still important in the breathlessness associated with mechanical loads, is insufficient to explain the dyspnea arising from a number of experimental and clinical conditions. As our understanding of the interactions between effort and afferent information from the respiratory system grows, new therapeutic interventions to alleviate dyspnea are likely to follow.