Effect of unilateral diaphragm paralysis on branch pulmonary artery flow

Respiration is known to be a significant contributor to pulmonary flow in patients who have had Glenn or Fontan procedures.

The purpose of this study was to evaluate the effect of respiration on branch pulmonary artery flow in normal participants, in those with uncomplicated Glenn or Fontan procedures, and in those with uncomplicated biventricular (2V) repairs, and to compare them with similar groups of postoperative patients who had unilateral diaphragm paralysis.

Twenty-one normal infants and children were studied, along with 10 who had undergone uncomplicated bidirectional Glenn or Fontan palliation. Also studied were 10 patients with uncomplicated 2V repairs and 17 patients having ultrasound demonstration of diaphragm paralysis. Nine had undergone Glenn or Fontan procedures and 8 had undergone 2V repair. With the use of conventional pulsed Doppler, branch right and left pulmonary artery waveforms were recorded during spontaneous respiration. The velocity time integral (VTI); heart rate (HR); and systolic, diastolic, and mean velocities were measured at end-expiration and during inspiration. The pulsatility index (PI) (PI = systolic velocity - diastolic velocity/mean velocity) was calculated for each condition.

In normal participants PI was 1.69 with a 4.7% increase with inspiration; VTI x HR was 1859. In patients who had undergone uncomplicated Glenn/Fontan procedures PI was 1.06 with a 27.5% increase with inspiration; VTI x HR was 1303, all P =.001 versus normal participants. In patients with 2V repairs PI was 1.7 with a 5.6% increase with inspiration; VTI x HR was 1850, all P = ns versus normal participants. Patients with Glenn/Fontan connections and diaphragm paralysis had lower PI (0.81), inspiratory increase (7.9%), and VTI x HR (610) on the affected side, all P =.001 versus the normal side, and versus patients who had undergone uncomplicated Glenn/Fontan procedures. Patients with 2V repair with a pulsatile source of pulmonary flow had a smaller significant difference in the measured indices. Three patients underwent diaphragm plication with improvement in PI, inspiratory increase in PI, and VTI x HR postplication.

In normal participants and patients with uncomplicated 2V repair, inspiration has little effect on PI in branch pulmonary arteries. In patients who have undergone uncomplicated Glenn/Fontan procedures, PI is less than that of normal participants and the effect of inspiration is approximately 5-fold greater. This significant effect of inspiration on pulmonary flow is lost on the affected side in patients with Glenn/Fontan connections and diaphragm paralysis, and is blunted on the affected side in patients with 2V repair and diaphragm paralysis. Loss of diaphragm function is associated with redistribution of pulmonary flow away from the affected side.