Measurement of intrabronchial pressure in man

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Abstract
By measuring total and lateral airway pressures in intact normal man, simultaneously with esophageal pressure, volume, and flow, it was possible to estimate the pressure difference across the wall of the airway, the pressure-flow curves of various segments of the airway, and the compliance of the airway. The results showed that: 1 Expiratory airway compression only occurs between the segmental bronchi and the glottis at volumes between 75 and 25% VC. 2) Expiratory flow is limited by compression of these airways. 3) The resistance of airways between segmental bronchi and trachea is variable, being markedly affected both by lung volume and pleural pressure. Tracheal resistance varies little with lung volume, but considerably with pleural pressure. The resistance of the airways between alveoli and segmental bronchi varies with lung volume but little with pleural pressure. These are probably the major resistance airways during quiet breathing. 4) Airway compliance is inversely related to lung volume. 5) The Bernouilli effect is large in large airways and helps to limit expiratory flow. bronchial pressure; airway resistance; airway compliance; maximal expiratory flow; equal pressure point; lung mechanics; airway compression Submitted on November 5, 1964