BACKGROUND: Although mainly described in patients with chronic obstructive pulmonary disease, pursed lip breathing (PLB) could prove useful in patients with interstitial lung disease (ILD) by improving exertional tachypnea and respiratory control. This prospective, randomized, crossover trial aimed at evaluating the impact of PLB on dyspnea and walking distance in ILD patients. METHODS: ILD patients with total lung capacity of <80% predicted were randomized to 6-min walk tests using either PLB or usual breathing. Patients were crossed over for the second 6-min walk tests and served as their own controls. Ventilatory and metabolic variables were recorded using a portable metabolic cart and were compared at 1-min intervals. RESULTS: Thirty-five patients were included (mean forced vital capacity of 64 +/- 10% predicted). Use of PLB resulted in lower mean respiratory rates and larger tidal volumes (both p < 0.001), worsened dyspnea ratings (post-6-min walk test Borg score: 5.2 +/- 2.6 versus 4.2 +/- 2.3, p < 0.001), and walking distance (403 +/- 102 m versus 429 +/- 93 m, p < 0.001). Twenty-nine patients (83%) described PLB as less comfortable than usual breathing. Both groups had similar total ventilation and oxygen saturation (all p > 0.05), but PLB resulted in higher mean oxygen uptake (13.9 +/- 3.6 versus 12.9 +/- 3.2 mL/kg/min, p = 0.02), even when corrected for walking distance (p < 0.001). CONCLUSION: In ILD patients, acute exposure to PLB did not improve exertional dyspnea, walking distance, or gas exchange, and was associated with higher metabolic demands than usual breathing. These results cast doubt on the usefulness of this technique in ILD patients and should be taken into account when tailoring pulmonary rehabilitation programs to this population.
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