VENTILATORY MECHANICS AT REST AND DURING EXERCISE IN PATIENTS WITH CYSTIC-FIBROSIS

Ventilatory mechanics were measured at rest and during steady-state (2 5%, 50%, 75%) and maximal exercise (W-Max) on a cycle-ergometer in eig ht adult patients (FEV(1) 22 to 114% of predicted) with cystic fibrosi s (CF). tidal flow-volume loops were measured at rest and during exerc ise and placed within the maximal pre- and postexercise flow-volume lo ops, based on measured end-expiratory lung volume (EELV). The degree o f flow limitation was expressed as the percentage of the tidal flow-vo lume loop that met the expiratory boundary of the maximal loop (TFVL%) . Pressure-volume relationships were assessed by measurement of transp ulmonary pressure (Prp). Peak inspiratory PTP was compared with maxima l inspiratory pressures at rest and during exercise (Pcap(i)) at the e quivalent lung volume. The maximal effective expiratory pressure (Pmax (e)) was determined using the orifice technique. Three patients with m ilder disease (FEV(1) 114, 98, 89% of predicted) did not show any flow limitation at rest or 50% W-Max but two did show some flow limitation at W-Max (0, 3, 23 TFVL%) with a decrease in EELV (-400, -200, -300 m l). There was considerable reserve for inspiratory and expiratory pres sure generation at W-Max. Flow limitation was noted at rest in three p atients and at 50% W-Max in the five patients with more severe airways obstruction. The increased flow was achieved by an increase in EELV i n all five patients (+400, +430, +330, +150, +700 ml at W-Max). Pcap(i ) was reached in two patients (-28, -36 cm H2O), while Pmax, was excee ded by four patients suggesting inefficient pressure generation. Expir atory Row limitation, hyperinflation, and pressure swings approaching capacity severely compromised the capacity to generate ventilation in some patients with CF.