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Pulmonary Mechanics in Fibrosing Alveolitis
101
Citations
0
References
1977
Year
EngineeringAdvanced Lung DiseasePulmonary Alveolar ProteinosisLung ComplianceBiomechanicsLung HealthLung Recoil PressuresMechanobiologyPulmonary CirculationPulmonary MechanicsAlveolar BiologyPulmonary FibrosisPulmonary MedicineRespiration (Physiology)PhysiologyPulmonary PhysiologyLung MechanicsLung Tissue VolumeMedicine
Fibrosing alveolitis is marked by a substantial loss of functional alveoli and low static compliance, and distinguishing between alveolar loss and abnormal distensibility remains difficult. The authors examined pressure‑volume and flow‑volume relationships in eight patients, showing that replacement of alveolar units by fibrous tissue—while preserving normal function of surviving units, respiratory muscles, chest wall, and airways—explains the abnormal compliance and recoil patterns. Lung recoil pressures were elevated at full inflation but unchanged below functional residual capacity, whereas airway function was normal for recoil but supernormal for absolute lung volume.
Pulmonary and airway mechanics were studied in 8 patients with severe fibrosing alveolitis. In this disease, the number of functioning alveoli is probably considerably decreased, but static compliance was low even when related to the decreased lung volume. Lung recoil pressures toward full inflation were high but were not increased at and below functional residual capacity. Airway function was broadly normal for lung recoil pressure but supernormal for absolute lung volume. Analysis of model pressure-volume and maximal flow-volume curves showed that (2) these features could be produced simply by replacement of some units by indistensible fibrous tissue and retention of normal function of the surviving alveoli, respiratory muscles, chest wall, and airways; (2) increased lung tissue volume may prevent an increase in lung recoil pressures in the lower part of the vital capacity; and (3) the decreased lung volume could result in a decrease in upstream conductance without structural change in the airways. Measurement of lung compliance, even when corrected for the decreased lung volumes, may not distinguish between loss of units (lung “shrinkage”) and abnormal distensibility of the functioning alveoli, but the latter is likely if maximal expiratory flow is excessive in relation to the lung volume expressed as per cent vital capacity.