Diaphragm Ultrasonography as an Alternative to Whole-Body Plethysmography in Pulmonary Function Testing

• Published in: Journal of ultrasound in medicine 2006-02, Vol.25 (2), p.225-232
• Main Authors: Scott, Samantha, Fuld, Jonathan P, Carter, Roger, McEntegart, Margaret, MacFarlane, Niall G
• Format: Article
• Language: English
• Subjects: Adrenergic beta-Agonists; Albuterol; diaphragm; Diaphragm - diagnostic imaging; Female; Humans; Linear Models; Male; Middle Aged; plethysmography; Plethysmography, Whole Body; Prospective Studies; Respiratory Function Tests - methods; Sensitivity and Specificity; Ultrasonography
• ISSN: 0278-4297; 1550-9613
• DOI: 10.7863/jum.2006.25.2.225

Objective. Whole‐body plethysmography is a common method of measuring pulmonary function. Although this technique provides a sensitive measure of pulmonary function, it can be problematic and unsuitable in some patients. The development of more accessible techniques would be beneficial. Methods. A prospective study was performed to validate diaphragm ultrasonography as an alternative to whole‐body plethysmography in patients referred for pulmonary function testing. Diaphragm movement and position were assessed by ultrasonography after standard pulmonary function testing using whole‐body plethysmography. Results. A wide range of lung function was observed. Standard lung volumes were as follows: total lung capacity, 5.57 ± 1.31 L, residual volume, 2.27 ± 0.56 L; and vital capacity, 3.30 ± 0.98 L (mean ± SD). The ratio of forced expiratory volume in 1 second to forced vital capacity was calculated as 0.69 ± 0.08. Ultrasonography showed that mean diaphragm excursion values were 11.1 ± 3.8 mm (2‐dimensional), 14.7 ± 4.1 mm during quiet breathing (M‐mode), and 14.8 ± 3.9 mm during a maximal sniff (M‐mode). The velocity of diaphragm movement rose sharply during the sniff maneuver from 15.2 ± 5.8 mm/s during quiet breathing to 104.0 ± 33.4 mm/s. Static 2‐dimensional measures of diaphragm position at the end of quiet inspiration or expiration correlated with standard measures of lung volume on plethysmography (eg, a correlation coefficient of 0.83 was obtained with end inspiration and vital capacity). All measures of diaphragm movement (whether by 2‐dimensional or M‐mode techniques) were poorly correlated with any lung volumes measured. Conclusions. These data suggest that dynamic measurements using diaphragm ultrasonography provide a relatively poor measure of pulmonary function in relation to whole‐body plethysmography.