Ventilation–perfusion inequality and carbon dioxide sensitivity in hypoxaemic chronic obstructive pulmonary disease (COPD) and effects of 6 months of long‐term oxygen treatment (LTOT)

Abstract

An elevated V mean and probably shunting are important contributing factors for the reduced PaO(2) and hypercapnic ventilatory response is a major determinant of PaCO(2) in eucapnic stable hypoxaemic COPD. Six months of LTOT does not affect blood gases, CO(2) sensitivity or ventilation-perfusion relationships.

Lung ventilation–perfusion imbalance in pulmonary emphysema: assessment with automated V/Q quotient SPECT

“…These results are considered to be due to larger variation of V/Q in more advanced staging of emphysema, and these parameters appear adequate to evaluate the severity of lung V-Q imbalance in patients with emphysema. The previous studies showed that lung gas diffusing capacity was more severely disturbed in advanced stage of chronic obstructive pulmonary diseases [4,16]. As SD of V/Q profile was significantly correlated with A-aDO2 in our patients, it can be a good parameter to evaluate the severity of lung gasexchange impairment in patients with emphysema.…”

“…Regional lung V-Q balance in patients with emphysema should be variously impaired according to the degree of alveolar destruction, airway obstruction, increased lung tissue compliance, air trapping, hyperinflation and resultant compression of bronchioles or small vasculatures, collateral ventilation, and hypoxic vasoconstriction associated with ventilation disturbance [4,[15][16][17][18][19]. Cigarette smoking usually and initially induces inflammatory obstruction of airflow in central and/or peripheral airways, and subsequently induces alveolar destruction [15][16][17][18][19][24][25][26]. Lungs in smokers may have partial lung areas with airway obstruction but without significant alveolar interstitial microvascular destruction, where ventilation may be more disturbed compared with perfusion, resulting in shunt effect.…”

“…V/Q quotient single photon emission computed tomography (SPECT) derived from combined V-Q SPECT study is a useful tool for objective assessment and quantitation of lung V-Q imbalance on cross-sectional lungs [6][7][8][9][10][11][12]. Patients with pulmonary emphysema traditionally had been believed to have grossly matched lung V-Q impairment, but significant V-Q imbalance may be present due to complicated lung pathophysiology such as alveolar destruction, compression of small vasculatures by hyperinflated lung tissue, and hypoxic vasoconstriction [13][14][15][16]. V/Q quotient SPECT may be sensitive to identify emphysematous lungs, as previous animal and clinical SPECT studies showed perfusion and/or ventilation impairment even in normal lungs on high-resolution computed tomography (CT) [4,9,[16][17][18][19].…”

“…Patients with pulmonary emphysema traditionally had been believed to have grossly matched lung V-Q impairment, but significant V-Q imbalance may be present due to complicated lung pathophysiology such as alveolar destruction, compression of small vasculatures by hyperinflated lung tissue, and hypoxic vasoconstriction [13][14][15][16]. V/Q quotient SPECT may be sensitive to identify emphysematous lungs, as previous animal and clinical SPECT studies showed perfusion and/or ventilation impairment even in normal lungs on high-resolution computed tomography (CT) [4,9,[16][17][18][19]. Although emphysematous lung is usually assessed on morphologic CT, this SPECT may more accurately detect it.…”

Diffusion capacity and CT measures of emphysema and airway wall thickness - Relation to arterial oxygen tension in COPD patients

“…In emphysema, a high V/Q ratio, caused by increased physiological dead space due to the destruction of the pulmonary capillary bed, is predominant (20). In a study of 14 patients with severe or very severe COPD, V/Q mismatch was found to be the most important cause of hypoxaemia through 'wasted' ventilation of poorly perfused areas (21). Also, low V/Q ratios can be present in emphysema.…”