The Importance of Respiratory Rate Monitoring: From Healthcare to Sport and Exercise

Abstract

Respiratory rate is a fundamental vital sign that is sensitive to different pathological conditions (e.g., adverse cardiac events, pneumonia, and clinical deterioration) and stressors, including emotional stress, cognitive load, heat, cold, physical effort, and exercise-induced fatigue. The sensitivity of respiratory rate to these conditions is superior compared to that of most of the other vital signs, and the abundance of suitable technological solutions measuring respiratory rate has important implications for healthcare, occupational settings, and sport. However, respiratory rate is still too often not routinely monitored in these fields of use. This review presents a multidisciplinary approach to respiratory monitoring, with the aim to improve the development and efficacy of respiratory monitoring services. We have identified thirteen monitoring goals where the use of the respiratory rate is invaluable, and for each of them we have described suitable sensors and techniques to monitor respiratory rate in specific measurement scenarios. We have also provided a physiological rationale corroborating the importance of respiratory rate monitoring and an original multidisciplinary framework for the development of respiratory monitoring services. This review is expected to advance the field of respiratory monitoring and favor synergies between different disciplines to accomplish this goal.

Keywords: breathing control; measurement scenario; patient monitoring; respiratory frequency; respiratory monitoring; sensors; stress; technologies; vital signs; wearables.

Figure 4

A conceptual framework for the development of respiratory monitoring services. The framework is composed of ten steps that are numbered and listed on the left-hand side of the figure. Each of the ten steps is accompanied by a graphical example reported on the right-hand side of the figure. Panel (A) reports the thirteen monitoring goals described in this review. The graph in panel (B) is reproduced from Massaroni et al. [5]. The graph in panel (C) is reproduced from Naranjo-Hernández et al. [157]. Panel (D) provides an example of the output of some of the sensors used to detect apnea events in sleep laboratories. The graph in panel (E) is slightly modified from Massaroni et al. [24]. The graph in panel (F) is slightly modified from Lo Presti et al. [290]. The graph in panel (G) is reproduced from Tomasic et al. [293]. Panel (H) provides an example of data transmission performance evaluation. The graph in panel (I) is slightly modified from Quinten et al. [116]. The graph in panel (J) is slightly modified from Gerry et al. [110].

Figure 1

Schematic representation of the monitoring goals described in this review and related examples of specific measurement scenarios.

Figure 2

Schematic representation of the interactions between respiratory physiology, applied sciences, and technological development. The Figure shows how fruitful synergies between different disciplines are essential for the development of respiratory monitoring services.

Figure 3

Schematic representation of a simple model of ventilatory control (see Nicolò and Sacchetti [22] for further information). While respiratory rate (the behavioral component of minute ventilation) is substantially influenced by non-metabolic stressors, V_T (the metabolic component of minute ventilation) satisfies the metabolic requirements of the human body. As such V_T is fine-tuned according to the levels of respiratory rate and the magnitude of metabolic inputs, while f_R is influenced by V_T to a lesser extent. This model explains why f_R is more sensitive than V_T to a variety of non-metabolic stressors and corroborates the importance of f_R monitoring in different fields of use.

Figure 5

Schematic representation of how respiratory rate (values expressed both in breaths/min and in Hz) may change in response to different stressors. The range of respiratory rate values reported for each stressor has been defined according to the cited references (numbers in square brackets), but these values should only be considered as plausible examples. f_R values refer to adults if not otherwise stated. * it is not unusual to observe f_R values higher than 65 breaths/min. Mos, months.