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Abstract

Objective—To validate the use of noninvasive pulmonary function testing in sedated and nonsedated llamas and establish reference range parameters of respiratory mechanical function.

Animals—10 healthy adult llamas.

Procedures—Pulmonary function testing in llamas included the following: measurement of functional residual capacity (FRC) via helium dilution, respiratory inductance plethysmography (RIP) to assess breathing pattern and flow limitations, esophageal-balloon pneumotachography, and a monofrequency forced oscillatory technique (FOT; 1 to 7 Hz) before and after IM administration of xylazine (0.2 mg/kg).

Results—The following mean ± SD measurements of respiratory function were obtained in nonsedated llamas: FRC (5.60 ± 1.24 L), tidal volume (1.03 ± 0.3 L), dynamic compliance (0.83 ± 0.4 L/cm H2O), pulmonary resistance (RL; 1.42 ± 0.54 cm H2O/L/s), and respiratory system resistance (2.4 ± 0.9, 2.3 ± 0.7, 2.2 ± 0.6, 2.7 ± 0.7, and 2.5 ± 0.5 cm H2O/L/s at 1, 2, 3, 5, and 7 Hz, respectively) by use of FOT. Measurements of flow limitations via RIP were comparable to other species. Sedation with xylazine induced significant increases in RL and maximum change in transpulmonary pressure. Following sedation, a mean 127% increase in RL and mean 116% increase in respiratory system resistance were observed across 1 to 7 Hz. The magnitude of change in respiratory system resistance increased with decreasing impulse frequency, suggesting bronchoconstriction.

Conclusions and Clinical Relevance—Noninvasive pulmonary function testing is well tolerated in untrained unsedated llamas. These techniques have clinical applications in the diagnosis and treatment of respiratory tract disease, although testing should not be performed after sedation with xylazine.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To qualitatively describe lung CT images obtained from sedated healthy equine neonates (≤ 14 days of age), use quantitative analysis of CT images to characterize attenuation and distribution of gas and tissue volumes within the lungs, and identify differences between lung characteristics of foals ≤ 7 days of age and foals > 7 days of age.

Animals—10 Standardbred foals between 2.5 and 13 days of age.

Procedures—Foals were sedated with butorphanol, midazolam, and propofol and positioned in sternal recumbency for thoracic CT. Image analysis software was used to exclude lung from nonlung structures. Lung attenuation was measured in Hounsfield units (HU) for analysis of whole lung and regional changes in attenuation and lung gas and tissue components. Degree of lung attenuation was classified as follows: hyperinflated or emphysema, −1,000 to −901 HU; well aerated, −900 to −501 HU; poorly aerated, −500 to −101 HU; and nonaerated, > −100 HU.

Results—Qualitative evidence of an increase in lung attenuation and patchy alveolar patterns in the ventral lung region were more pronounced in foals ≤ 7 days of age than in older foals. Quantitative analysis revealed that mean ± SD lung attenuation was greater in foals ≤ 7 days of age (−442 ± 28 HU) than in foals > 7 days of age (−521 ± 24 HU). Lung aeration and gas volumes were lower than in other regions ventrally and in the mid lung region caudal to the heart.

Conclusions and Clinical Relevance—Identified radiographic patterns and changes in attenuation were most consistent with atelectasis and appeared more severe in foals ≤ 7 days of age than in older neonatal foals. Recognition of these changes may have implications for accurate CT interpretation in sedated neonatal foals with pulmonary disease.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate use of single manual alveolar recruitment maneuvers (ARMs) to eliminate atelectasis during CT of anesthetized foals.

ANIMALS 6 neonatal Standardbred foals.

PROCEDURES Thoracic CT was performed on spontaneously breathing anesthetized foals positioned in sternal (n = 3) or dorsal (3) recumbency when foals were 24 to 36 hours old (time 1), 4 days old (time 2), 7 days old (time 3), and 10 days old (time 4). The CT images were collected without ARMs (all times) and during ARMs with an internal airway pressure of 10, 20, and 30 cm H2O (times 2 and 3). Quantitative analysis of CT images measured whole lung and regional changes in attenuation or volume with ARMs.

RESULTS Increased attenuation and an alveolar pattern were most prominent in the dependent portion of the lungs. Subjectively, ARMs did not eliminate atelectasis; however, they did incrementally reduce attenuation, particularly in the nondependent portion of the lungs. Quantitative differences in lung attenuation attributable to position of foal were not identified. Lung attenuation decreased significantly (times 2 and 3) and lung volume increased significantly (times 2 and 3) after ARMs. Changes in attenuation and volume were most pronounced in the nondependent portion of the lungs and at ARMs of 20 and 30 cm H2O.

CONCLUSIONS AND CLINICAL RELEVANCE Manual ARMs did not eliminate atelectasis but reduced attenuation in nondependent portions of the lungs. Positioning of foals in dorsal recumbency for CT may be appropriate when pathological changes in the ventral portion of the lungs are suspected.

Full access
in American Journal of Veterinary Research