Effect of Hypophosphatemia on Diaphragmatic Contractility in Patients with Acute Respiratory Failure

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Abstract
We studied the effects of hypophosphatemia on diaphragmatic function in eight patients with acute respiratory failure who were artificially ventilated. Their mean serum phosphorus level was 0.55±0.18 mmol per liter (normal value, 1.20±0.10). The contractile properties of the diaphragm were assessed by measuring the transdiaphragmatic pressure generated at functional residual capacity during bilateral supramaximal electrical stimulation of the phrenic nerves. Diaphragmatic function was evaluated in each patient before and after correction of hypophosphatemia, which was achieved by administration of 10 mmol of phosphorus (as KH2P04) as a continuous infusion for four hours. After phosphate infusion, the mean serum phosphorus level increased significantly (1.33±0.21 mmol per liter, P20 as compared with 9.75±3.8 before phosphate infusion, P<0.001). Changes in the serum phosphorus level and transdiaphragmatic pressure were well correlated (r = 0.73).