Search

Pulmonary function testing is critical to the diagnosis of equine asthma (EA), an important cause of respiratory disease in the horse, but its clinical use has remained elusive, unfortunately, due to the complexity of reference methods, esophageal balloon/pneumotachography (EBP) and forced oscillatory mechanics (FOM), so we sought a non-invasive, portable method for use in horses through rapid interruption of airflow for equilibration of alveolar pressure with proximal airway pressure, termed flow interruption (FI). Resistance (R INT ) was computed as the relationship between the change in pressure at the nose before and immediately after interruption and flow immediately before interruption. A pilot study in 5 healthy university-owned animals using EBP and FI showed good correspondence between the two methods: R INT (0.33 +/- 0.05 cm H 2 O/l/s) and R L (0.31 +/- 0.06 cm H 2 O/l/s). In 2 separate populations of client-owned horses, with random assignment of methods to FI v EBP (n = 8), R INT showed good correlation with R L in horses, ( r s =.995, p = .0002) and accords with R L , with no significant difference between R INT and R L . Using FOM (n = 12), R INT (0.67 +/- 0.31 cmH 2 O/l/s) has good correlation with R RS measured with FOM ( r =.834, p = .0001), but is consistently smaller than R RS (0.74 +/- 0.33 cmH 2 O/l/s) . Histamine bronchoprovocation (HBP) was performed in a subset of these horses: FI classified one horse in 6 as less reactive than did EBP, and FI classified one horse in 7 as less reactive than did FOM.