Respiratory muscle performance in chronic obstructive lung diseases and interstitial lung fibrosis

ABSTRACT

Respiratory muscle performance and breathing pattern were studied in 10 patients with chronic obstructive pulmonary disease [COPD] and 12 patients with interstitial pulmonary fibrosis [IPF]. Data of the present study revealed that patients with COPD had respiratory muscle weakness and diminished endurance as evidenced by decrease in maximal expiratory pressures [PE max=42% pred., PI max.=53% pred.] and the critical value of the tension time index of the diaphragm [TIdi=0.12]. The pattern of breathing in COPD showed an increase in tidal volume [TV=617 ml], respiratory frequency [F=22/m], minute ventilation [VE=12.8 L/m], and the mean inspiratory flow [VT/Ti=606 ml/sec], while there was a decrease in the inspiratory duty cycle [Ti/Ttot=0.37]. Patients with IPF had also respiratory muscle weakness as manifested by decreased PE max [49% pred.] and PI max [68% pred.], while endurance was not much affected [TIdi=0.1]. Breathing pattern in IPF showed decrease in TV [478 ml], and increase in F [36/m], VE [16 L/m], and VT/Ti [669 ml/sec], while Ti/Ttot was within normal [0.42]. It was concluded that respiratory muscle dysfunction and abnormal breathing pattern are important features in COPD and IPF and therefore should be included in the clinical and physiological evaluation of these patients