Physiological Impacts and Medical Applications of the Inspiratory Gasp Vascular Reflex.

Measurement of skin blood flow in the hand, foot, finger, or toe reveals a transient decrease in response to a rapid, deep inspiration, a phenomenon termed the inspiratory gasp vascular reflex (IGVR). The use of the IGVR as a test in future research and clinical applications requires knowledge of the method, its prior applications, its limitations and advantages, and the identification of clinically relevant knowledge gaps. The goal of this review is to consolidate and critically evaluate the findings of early workers, as well as the continuum of evolving prior knowledge regarding key aspects of this reflex. This report is derived from information obtained from an analysis of published material secured via literature searches of four major electronic databases and, in part, based on the author's experience with the method. The literature search covered all years up to 2026 and used the primary search string: ("inspiratory gasp" OR "inspiratory gasp vascular reflex" OR "inspiratory gasp reflex"). Studies considered relevant for inclusion were those that evaluated the IGVR in healthy persons or persons with underlying conditions. The overriding evidence from the literature indicates that the IGVR can provide useful information about the status of peripheral neural function. However, its application and interpretation may be deceptively simple. The measurement methodology is straightforward, using either laser Doppler flowmetry or photoplethysmography to measure changes induced by one or more inspiratory gasps. However, measurement conditions contribute to variability in response magnitude, making it difficult to establish "normal" ranges. It is concluded that the most useful application of the IGVR test is to assess changes in peripheral neurovascular function in individuals following interventions or treatments that target such functions or to track longitudinal changes. Its use in discriminating between patient groups with various peripheral neurovascular dysfunctions and controls is limited by the absence of suitable normal reference ranges and standardized measurement protocols. However, when confounding factors are considered and group differences are sufficiently large, the IGVR can be a useful test.