Chest
Volume 123, Issue 6, June 2003, Pages 2019-2027
Journal home page for Chest

Clinical Investigations
Miscellaneous
Variation in Diaphragm Position and Shape in Adults With Normal Pulmonary Functiona

https://doi.org/10.1378/chest.123.6.2019Get rights and content

Background

Diaphragm position and shape on chest radiographs are routinely used as indicators of normal or abnormal lung volume. However, previous population studies of normal diaphragm position and shape frequently lack objective radiographic measurements and documentation of pulmonary function, and do not account for the observed variability.

Study objectives

To determine the spectrum of diaphragm position and shape on chest radiographs using objective measurements, in patients with normal pulmonary function, and to identify the relationship of diaphragm position and shape to demographic variables and radiographic thoracic dimensions.

Design

Prospective cross-sectional observational study.

Setting

University hospital.

Patients

One hundred fifty-three adults with normal FEV1 (≥ 80% predicted) and normal total lung capacity (80 to 120% predicted).

Measurements and results

Diaphragm position and shape relative to anatomic landmarks were determined from posteroanterior and lateral chest radiographs. We used descriptive statistics to calculate normal values, and linear correlation, two-tailed t tests, and multivariate analysis to relate findings to age, weight, gender, and thoracic dimensions. The right hemidiaphragm dome was positioned at 9.7 ± 0.8 thoracic vertebral levels (body plus disk space) [mean ± SD] below the top of the first thoracic vertebra (range, 7.4 to 11.3 vertebral levels), and the left hemidiaphragm dome was positioned at 10.2 ± 0.8 vertebral levels (range, 8.1 to 11.8 vertebral levels). The right hemidiaphragm radius was 13.8 ± 3.8 cm (range, 7.2 to 29.6 cm), and the ratio between the height and the anteroposterior dimension of the right hemidiaphragm was 0.23 ± 0.05 cm (range, 0.08 to 0.36 cm). The diaphragm tended to be lower with higher age, lower weight, and smaller transverse and anteroposterior thoracic dimensions (r = 0.22 – 0.47, p < 0.05), and flatter (larger radius) with higher age, weight, transverse thoracic dimension, pack-years smoked (r = 0.32 – 0.42, p < 0.0001), and male gender (p < 0.0001). The tested variables accounted for approximately one third of the variability in diaphragm position and shape (multivariate R2 = 0.31 − 0.38).

Conclusions

The substantial variability in normal diaphragm position and shape is related to weight, age, and thoracic dimensions. Consideration of these factors may be useful when evaluating chest radiographs.

Section snippets

Patient Selection

The study protocol was approved by the local human studies committee. From 5,100 patients referred for pulmonary function tests at our institution between January and August of 2000, 492 patients had normal findings, excluding those who underwent lung transplantation. Of these 492 patients, 316 patients had an available two-view chest radiographic examination performed within 2 months of pulmonary function testing and were considered for inclusion. Of these, 78 patients were excluded due to a

Diaphragm Position and Shape

The mean right hemidiaphragm dome position was at 9.7 ± 0.8 vertebral levels. This is slightly above the inferior endplate of the tenth thoracic vertebral body (T10), and 0.9 ± 2.3 cm above the right crossing rib level. The mean left hemidiaphragm dome position was 0.5 vertebral levels lower than the right, 0.3 ± 2.4 cm below the left crossing rib level (Table 2). The mean position of the right and left hemidiaphragm domes was higher in the obese subgroup (Table 2). In the nonobese subgroup,

Discussion

A previous major study defining normal diaphragm position on chest radiographs3used the anterior ribs as an anatomic reference, and this is often recommended to those learning to interpret chest radiographs. However, referencing diaphragm position to the anterior ribs can be difficult, since the contours of the anterior ribs and diaphragm domes are not parallel, and the costal portions of the anterior ribs may not be clearly visible. Relating diaphragm position to the thoracic spine has been

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