Reduced Rate of Alveolar-Capillary Recruitment and Fall of Pulmonary Diffusing Capacity During Exercise in Patients With Heart Failure

Hemorrhagic shock induced a marked fall in the pulmonary diffusing capacity for carbon monoxide in the dog (Dl) and produced marked nonuniformity of Dl/Va ratios throughout the lung as assessed by the “equilibration technique”. Difficulties in calculating over-all Dl under these conditions are discussed. Induced anemia also produced a fall in Dl, but little change in the uniformity of Dl/Va ratios was noted. In isolated perfused dog lungs where blood flow, pulmonary vascular pressures, lung volume, and ventilation were maintained constant, Dl was found to be proportional to hematocrit, suggesting either: 1) that virtually all resistance to CO diffusion is in the erythrocyte or 2) that the apparent diffusing capacity of the alveolar-capillary membrane is dependent upon hematocrit, carbon monoxide transfer being reduced across portions of membrane which are some distance from a red blood cell. Submitted on January 12, 1962

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An open-circuit method for determining lung diffusing capacity during exercise: comparison to rebreathe

Journal of Applied Physiology ◽

10.1152/japplphysiol.00348.2005 ◽

2005 ◽

Vol 99 (5) ◽

pp. 1985-1991 ◽

Cited By ~ 26

Author(s):

Eric M. Snyder ◽

Bruce D. Johnson ◽

Kenneth C. Beck

Keyword(s):

Cardiac Output ◽

Breathing Pattern ◽

Open Circuit ◽

Diffusing Capacity ◽

External Work ◽

Capillary Recruitment ◽

Single Breath ◽

Circuit Technique ◽

Alveolar Capillary ◽

Rest And Exercise

To avoid limitations associated with the use of single-breath and rebreathe methods for assessing the lung diffusing capacity for carbon monoxide (DlCO) during exercise, we developed an open-circuit technique. This method does not require rebreathing or alterations in breathing pattern and can be performed with little cognition on the part of the patient. To determine how this technique compared with the traditional rebreathe (DlCO,RB) method, we performed both the open-circuit (DlCO,OC) and the DlCO,RB methods at rest and during exercise (25, 50, and 75% of peak work) in 11 healthy subjects [mean age = 34 yr (SD 11)]. Both DlCO,OC and DlCO,RB increased linearly with cardiac output and external work. There was a good correlation between DlCO,OC and DlCO,RB for rest and exercise (mean of individual r2 = 0.88, overall r2 = 0.69, slope = 0.97). DlCO,OC and DlCO,RB were similar at rest and during exercise [e.g., rest = 27.2 (SD 5.8) vs. 29.3 (SD 5.2), and 75% peak work = 44.0 (SD 7.0) vs. 41.2 ml·min−1·mmHg−1 (SD 6.7) for DlCO,OC vs. DlCO,RB]. The coefficient of variation for repeat measurements of DlCO,OC was 7.9% at rest and averaged 3.9% during exercise. These data suggest that the DlCO,OC method is a reproducible, well-tolerated alternative for determining DlCO, particularly during exercise. The method is linearly associated with cardiac output, suggesting increased alveolar-capillary recruitment, and values were similar to the traditional rebreathe method.

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Simultaneous Measurement of Lung Diffusing Capacity and Pulmonary Hemodynamics Reveals Exertional Alveolar‐Capillary Dysfunction in Heart Failure With Preserved Ejection Fraction

Journal of the American Heart Association ◽

10.1161/jaha.120.019950 ◽

2021 ◽

Author(s):

Caitlin C. Fermoyle ◽

Glenn M. Stewart ◽

Barry A. Borlaug ◽

Bruce D. Johnson

Keyword(s):

Heart Failure ◽

Maximal Exercise ◽

Arterial Compliance ◽

Preserved Ejection Fraction ◽

Diffusing Capacity ◽

Pulmonary Capillary ◽

Capillary Membrane ◽

Pulmonary Arterial ◽

Wedge Pressure ◽

Alveolar Capillary

Background Hemodynamic perturbations in heart failure with preserved ejection fraction (HFpEF) may alter the distribution of blood in the lungs, impair gas transfer from the alveoli into the pulmonary capillaries, and reduce lung diffusing capacity. We hypothesized that impairments in lung diffusing capacity for carbon monoxide (DL CO ) in HFpEF would be associated with high mean pulmonary capillary wedge pressures during exercise. Methods and Results Rebreathe DL CO and invasive hemodynamics were measured simultaneously during exercise in patients with exertional dyspnea. Pulmonary pressure waveforms and breath‐by‐breath pulmonary gas exchange were recorded at rest, 20 W, and symptom‐limited maximal exercise. Patients with HFpEF (n=20; 15 women, aged 65±11 years, body mass index 36±8 kg/m 2 ) achieved a lower symptom‐limited maximal workload (52±27 W versus 106±42 W) compared with controls with noncardiac dyspnea (n=10; 7 women, aged 55±10 years, body mass index 30±5 kg/m 2 ). DL CO was lower in patients with HFpEF compared with controls at rest (DL CO 10.4±2.9 mL/min per mm Hg versus 16.4±6.9 mL/min per mm Hg, P <0.01) and symptom‐limited maximal exercise (DL CO 14.6±4.7 mL/min per mm Hg versus 23.8±10.8 mL/min per mm Hg, P <0.01) because of a lower alveolar‐capillary membrane conductance in HFpEF (rest 16.8±6.6 mL/min per mm Hg versus 28.4±11.8 mL/min per mm Hg, P <0.01; symptom‐limited maximal exercise 25.0±6.7 mL/min per mm Hg versus 45.5±22.2 mL/min per mm Hg, P <0.01). DL CO was lower in HFpEF for a given mean pulmonary artery pressure, mean pulmonary capillary wedge pressure, pulmonary arterial compliance, and transpulmonary gradient. Conclusions Lung diffusing capacity is lower at rest and during exercise in HFpEF due to impaired gas conductance across the alveolar‐capillary membrane. DL CO is impaired for a given pulmonary capillary wedge pressure and pulmonary arterial compliance. These data provide new insight into the complex relationships between hemodynamic perturbations and gas exchange abnormalities in HFpEF.

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