Portable chest radiography in mechanically ventilated ICU patients: does synchronizing with end-inspiration improve the quality of films?

Introduction

The quality of portable chest radiographs (CXRs) taken in the ICU is inferior to films taken in the radiology department. The inability of sedated, ventilated patients to hold their breath during CXR will also affect the degree of lung inflation and contribute to lack of correlation between serial CXR changes and clinical status [1]. We studied the effect on CXR quality by manually synchronizing the ventilator to end-inspiration in mechanically ventilated ICU patients.

Methods

A pair of CXRs was taken after recruiting intubated, ventilated patients within 24 hours of emergency ICU admission. Intubated post-elective surgical patients were excluded due to the high likelihood of normal lungs. The control film was taken in the usual way, at a random phase of the ventilator cycle. For the synchronized film, the investigator wore a lead apron and dosimeter, stood 1 to 1.5 meters away from the patient, and pressed the inspiratory hold button. The sequence of the paired films was computer-randomized. The ventilator model, settings, patient position and portable X-ray machine settings were kept constant between films. Patients served as their own controls. Films were independently scored (1 = not clear/poorly inflated, 5 = very clear/well inflated) by two specialist radiologists based on five criteria: (i) clarity of lines and tubes, (ii) definition of pulmonary vasculature, (iii) visibility of mediastinum, (iv) definition of the diaphragm and (v) degree of lung inflation. Linear regression, taking two radiologists' scores of each patient into account, was used to examine whether there were any differences in the criteria ratings between random and synchronized films. Radiologists and statistician were blinded.

Results

We recruited 110 patients; there were no complications from the breath-hold maneuver. Dosimeter readings were negligible. Synchronized films had higher total scores and mean scores for criteria (ii) to (v), 95% confidence interval. P values were statistically significant: for total score, P < 0.001; and for criteria (ii), P = 0.001; (iii), P < 0.001; (iv), P < 0.01; and (v), P < 0.001.

Conclusion

Synchronizing the CXR to end-inspiration improves the quality of the film and is safe.