The Impact of Respiratory Exercises on Voice Outcomes: A Systematic Review of the Literature.

INTRODUCTION: The role of respiratory exercises in voice therapy remains unclear as many patients do not need extensive breath support to meet their voice demands. However, since these exercises are commonly used in clinical practice and ubiquitous in voice therapy textbooks, there is a need to determine the evidence for using respiratory exercises to improve vocal function.

OBJECTIVE: The goal of the present review is to determine the state of the evidence regarding the effectiveness of respiratory interventions to improve respiratory and voice outcomes.

METHODS: A review of the literature was conducted using three electronic databases: Pubmed, Scopus, and CINAHL. A search strategy was developed to highlight two main concepts: (1) voice and (2) respiratory exercises.

RESULTS: Out of 650 articles identified through the search, 23 articles met the inclusion criteria, spanning nine types of respiratory exercises: (1) expiratory muscle strength training; (2) inspiratory muscle strength training; (3) incentive spirometry; (4) isocapnic hyperpnea; (5) respiratory effort treatment; (6) abdominal directives; (7) "easy breathing"; (8) stimulation training; and (9) vocalization with abdominal breath support. Respiratory improvements were reported in 12 articles. Nine of 12 articles also reported some voice improvements, although these were limited to subsets of participants.

CONCLUSIONS: The results of this review suggest that the evidence to support using respiratory exercises to improve vocal function is specific to a patient's respiratory and vocal needs. That is, current evidence does not support using respiratory exercises for all patients with voice disorders. Emerging evidence also indicates the importance of generalizing the outcomes of respiratory exercises to voice tasks. It is critical that the mechanism of action through which respiratory exercises can impact voice outcomes be thoroughly understood, and it is hoped that future research will help provide more information in this regard.