Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Results (3)

Expiratory muscle strength was within normal limits in all five patients studied and changed little in any patient on successive retesting after surgery. The average percentage increase in PEmax was 13 percent, compared with a mean increase of 84 percent in Pimax. Buy Asthma Inhalers Online
A restrictive pattern was noted on spirometric measurements in four of five patients on the initial study (FVC range, 62 to 79 percent predicted [Fig 1]). The vital capacity was within the normal range for the patient (patient 1) who had phrenic paresis rather than paralysis when first studied 150 days postoperatively. The vital capacity and FEV, were within normal limits in four of five patients at the time of final study. The sole exception (patient 2) was the individual who had the most marked phrenic paresis at the study conclusion.
The time course of recovery of the phrenic nerve for the five patients is shown in Table 2 and for two representative patients in Figure 2. In two patients (patients 2 and 3), the left hemidiaphragm continued to move paradoxically on sniff testing when a hemidia-phragmatic EMG was first elicited after phrenic stimulation. In these patients on subsequent follow-up examinations and in all other patients, the left diaphragm descended normally during sniff maneuvers when a CDAP was elicited.
The left phrenic recovery was incomplete in most patients by the time of final study (Table 2). In only one patient had the phrenic nerve latency unequivocally returned to normal (patient 1). In two patients the left phrenic nerve latencies were within predicted limits but were still longer than the right phrenic nerve latencies (patients 3 and 4). A definite left phrenic nerve paresis was present in the remaining two patients (No. 2 and 5), since there was still a prolongation of phrenic nerve latency and a reduction in CDAP amplitude on the final study.


Figure 2. Representative sequential phrenic nerve electrophysiologic studies for patients 3 and 4 from 60 to 440 and 60 to 490 days, respectively, after CAB surgery. For both patients, left phrenic nerve stimulation is on the left. Phrenic nerve latency is the time from stimulus onset to the onset of the CDAP and is measured in milliseconds. The CDAP amplitude is from baseline to the peak of the positive CDAP tracing and is measured in microvolts.