• diaphragm plication
• phrenic nerve injury

We read with great interest the paper by Simansky et al¹ describing the good results of plication of the diaphragm following phrenic nerve injury. The authors conclude that pulmonary function tests (PFTs) in combination with quantitative perfusion scans are helpful in selecting patients for this procedure. In table 4 they present the PFTs they were using and, in addition, they suggest that more sophisticated tests such as ultrasonography or fluoroscopy can also be useful in assessing diaphragmatic paralysis. Although we agree that all these tests are very helpful, assessment of vital capacity (VC) in both sitting and supine positions was omitted. This is a very simple test that gives important information about the function of the diaphragm, with a decrease in VC of >30% from the sitting to the supine position suggesting diaphragmatic paralysis.

The practical value of this test is clearly shown in the following patient in whom we initiated non-invasive positive pressure ventilation (NIPPV) because of a right sided diaphragmatic paralysis due to a coronary bypass. At the start of NIPPV there was a gap between the VC in the sitting and supine positions of 0.8 l (30%; VC sitting 2.7 l, VC supine 1.9 l). We started NIPPV and the patient became less dyspnoeic and less tired. After 18 months the clinical situation was still improving, with an increase in VC both in the sitting and supine positions to 3.5 l and 2.8 l, respectively. After 36 months the gap between VC in the two positions had almost disappeared (3.6 l and 3.5 l, respectively). In addition, the radiograph of the thorax showed a downward shift and normalisation of the position of the right diaphragm. We therefore stopped NIPPV and after several weeks the patient slept well without ventilatory support. This case illustrates that the assessment of VC in both the sitting and supine positions can be very helpful in the diagnosis and follow up of patients with diaphragmatic paralysis.