Airway-pressure challenge during spontaneous breathing: a conceptual framework for interpreting hemodynamic vulnerability to positive-pressure ventilation in dogs and cats.

Positive-pressure ventilation can precipitate an immediate fall in arterial blood pressure during general anesthesia, but this response is usually recognized only after controlled ventilation has already been initiated and is then interpreted retrospectively. We propose a different framework for dogs and cats: a brief airway-pressure challenge during spontaneous breathing may serve as a deliberate, reversible bedside probe of hemodynamic vulnerability to subsequent positive-pressure ventilation. The aim of this article is to articulate an interpretive, hypothesis-generating framework rather than to provide a validated protocol or an immediately deployable clinical test. In this view, the immediate arterial pressure response is interpreted not as a specific diagnostic sign or a simple test of circulating volume adequacy, but as an integrated cardiopulmonary stress response. Its meaning may be shaped by preload sensitivity, right ventricular afterload sensitivity, tricuspid regurgitation, pulmonary vascular burden, anesthetic state, myocardial reserve, and respiratory mechanics. Framing the maneuver in this way shifts attention from incidental observation to proactive interpretation and may help clinicians anticipate whether positive-pressure exposure is likely to be well tolerated or to warrant greater caution, closer monitoring, and more deliberate circulatory preparation. The framework also gives additional conceptual value to preserving spontaneous breathing before mandatory controlled ventilation, because this phase provides an interpretive window before the circulation is fully exposed to sustained positive-pressure ventilation. At the same time, this concept is not presented as a validated diagnostic test or treatment algorithm. Nor is it intended to recommend routine clinical implementation of the airway-pressure challenge as a ventilation method prior to technical standardization and prospective validation. Its clinical interpretation is context dependent and is best suited to settings in which immediate arterial pressure changes can be followed continuously, preferably with invasive arterial pressure monitoring. By reframing airway-pressure-associated hypotension as a structured challenge rather than a purely incidental event, this conceptual model provides a basis for future physiologic validation while supporting more deliberate bedside interpretation of cardiopulmonary vulnerability in veterinary anesthesia.