respiratory physiology

The clinical expression of idiopathic pulmonary fibrosis (IPF) is directly related to multiple alterations in lung function. These alterations derive from a complex disease process affecting all compartments of the lower respiratory system, from the conducting airways to the lung vasculature. In this article we review the profound alterations in lung mechanics (reduced lung compliance and lung volumes), pulmonary gas exchange (reduced diffusing capacity, increased dead space ventilation, chronic arterial hypoxaemia) and airway physiology (increased cough reflex and increased airway volume), as well as pulmonary haemodynamics related to IPF...

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The loss of pulmonary vessels has been shown to be related to the severity of pulmonary hypertension in patients with chronic obstructive pulmonary disease (COPD). The severity of hypoxaemia is also related to pulmonary hypertension and pulmonary vascular resistance in these patients, suggesting that the hypoxic condition probably plays an important role in this form of pulmonary hypertension. However, pulmonary hypertension also develops in patients with mild COPD without hypoxaemia. Oxygen supplementation therapy often fails to reverse the pulmonary hypertension in these COPD patients, thus suggesting that the pulmonary vascular alterations in those patients may involve different sites of the pulmonary vasculature or a different form of vascular remodelling...

This review provides an overview of the relationship between ventilation/perfusion ratios and gas exchange in the lung, emphasising basic concepts and relating them to clinical scenarios. For each gas exchanging unit, the alveolar and effluent blood partial pressures of oxygen and carbon dioxide (PO2 and PCO2) are determined by the ratio of alveolar ventilation to blood flow (V'A/Q') for each unit. Shunt and low V'A/Q' regions are two examples of V'A/Q' mismatch and are the most frequent causes of hypoxaemia...

We review the substantial recent progress made in understanding the underlying mechanisms controlling breathing and the applicability of these findings to selected human diseases. Emphasis is placed on the sites of central respiratory rhythm and pattern generation as well as newly described functions of the carotid chemoreceptors, the integrative nature of the central chemoreceptors, and the interaction between peripheral and central chemoreception. Recent findings that support critical contributions from cortical central command and muscle afferent feedback to exercise hyperpnoea are also reviewed...