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Connie C W Hsia - One of the best experts on this subject based on the ideXlab platform.
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nitric oxide Diffusing Capacity and alveolar microvascular recruitment in sarcoidosis
American Journal of Respiratory and Critical Care Medicine, 2004Co-Authors: Anagha R Phansalkar, Robert L Johnson, Chad M Hanson, Ahmed R Shakir, Connie C W HsiaAbstract:We measured Diffusing capacities for carbon monoxide (DLCO) and nitric oxide, lung volume, and cardiac output by a rebreathing technique at two alveolar O2 tensions (PAO2) at rest and exercise. Membrane Diffusing Capacity for CO (DMCO) and VC were estimated from DLCO by the Roughton-Forster (RF) method and also from simultaneous lung Diffusing Capacity for NO and DLCO measured at one O2 tension (modified RF method). Estimates by these methods agreed closely in normal subjects (Tamhane et al., Chest 2001;120:1850–1856). Using these methods, we studied patients with stages II–III pulmonary sarcoidosis to determine (1) whether the modified RF method accurately estimates DMCO and VC in parenchymal disease and (2) whether sarcoidosis alters recruitment of Diffusing Capacity with respect to cardiac output. In patients, DMCO and VC estimated by the two methods agreed closely. DMCO was disproportionately reduced relative to VC at any given cardiac output, and the slope of the relationship between DLCO and cardiac...
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recruitment of lung Diffusing Capacity update of concept and application
Chest, 2002Co-Authors: Connie C W HsiaAbstract:Lung Diffusing Capacity (Dl) for carbon monoxide (Dlco), nitric oxide (Dlno) or oxygen (Dlo2) increases from rest to peak exercise without reaching an upper limit; this recruitment results from interactions among alveolar volume (Va), and cardiac output (Q˙), as well as changing physical properties and spatial distribution of capillary erythrocytes, and is critical for maintaining a normal arterial oxygen saturation. Dlco and Dlno can be used to interpret the effectiveness of diffusive oxygen transport and track structural alterations of the alveolar-capillary barrier, providing sensitive noninvasive indicators of microvascular integrity in health and disease. Clinical interpretation of Dl should take into account Q˙ in addition to Va and hemoglobin concentration.
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pulmonary membrane Diffusing Capacity and capillary blood volume measured during exercise from nitric oxide uptake
Chest, 2001Co-Authors: Rahul M Tamhane, Robert L Johnson, Connie C W HsiaAbstract:Study objectives: To validate lung Diffusing Capacity for nitric oxide (DLNO) as an index of conductance of the alveolar-capillary membrane during exercise, we compared DLNO to lung Diffusing Capacity for carbon monoxide (DLCO) and pulmonary membrane Diffusing Capacity for carbon monoxide (DMCO), and compared pulmonary capillary blood volume (Vc) calculated by two methods. Setting and participants: The study was performed at a university medical center involving 12 nonsmoking healthy volunteers (age range, 23 to 79 years). DLCO ,D LNO, cardiac output (Qc), and lung volume were measured simultaneously at rest and during graded ergometer exercise by a rebreath- ing technique. Pulmonary membrane Diffusing Capacity and Vc were compared by (1) the classic technique of Roughton and Forster from DLCO measured at two alveolar oxygen tension (PAO2) levels, and (2) from DLNO and DLCO assuming negligible erythrocyte resistance to nitric oxide (NO) uptake, ie ,D LNO approximately equal to pulmonary membrane Diffusing Capacity for nitric oxide. Results: In all subjects, DLNO increased linearly from rest to exercise; age, Qc, and lung volume were the major determinants of DLNO by stepwise regression analysis. The DLNO/DLCO ratio averaged 3.98 0.38 ( SD) and the DLNO/DMCO ratio averaged 2.49 0.28 irrespective of exercise intensity. Changing PAO2 did not alter DLNO. Brief exposure to 40 ppm of inhaled NO during 16 s of rebreathing did not alter either DLCO or Qc. Estimates of pulmonary membrane Diffusing Capacity and Vc by the two methods showed a strong correlation. Conclusion: Results support DLNO as a direct measure of pulmonary membrane Diffusing Capacity, allowing the estimation of Vc in a single rebreathing maneuver during exercise. The DLNO-DLCO rebreathing technique can be applied clinically in the investigation of pulmonary microvascular regulation. (CHEST 2001; 120:1850-1856)
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red cell distortion and conceptual basis of Diffusing Capacity estimates finite element analysis
Journal of Applied Physiology, 1997Co-Authors: Connie C W Hsia, C J C Chuong, Robert L JohnsonAbstract:Hsia, C. C. W., C. J. C. Chuong, and R. L. Johnson, Jr.Red cell distortion and conceptual basis of Diffusing Capacity estimates: finite element analysis. J. Appl. Physiol. 83(4): 1397–1404, 1997.—T...
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critique of conceptual basis of Diffusing Capacity estimates a finite element analysis
Journal of Applied Physiology, 1995Co-Authors: Connie C W Hsia, C J C Chuong, Robert L JohnsonAbstract:We present a simple geometric model of a pulmonary capillary segment containing a variable number of red blood cells. The pattern of CO transfer from alveolar air to capillary red blood cells in this model is accurately computed by a finite element method and used to explore conceptual flaws in the Roughton-Forster (RF) and morphometric methods of estimating pulmonary Diffusing Capacity for CO. The CO uptakes calculated by the finite element method at two alveolar O2 tensions are introduced into the RF model to determine whether the anatomically defined membrane component of Diffusing Capacity for CO (DmCO) and pulmonary capillary blood volume (Vc) are recovered. The same capillary model is also subjected to standard morphometric analysis. Results are compared at different levels of capillary hematocrit (Hct). The RF method accurately recovers DmCO and Vc at a low Hct but modestly overestimates DmCO and underestimates Vc at higher Hct; errors arise because conductance of the tissue-plasma membrane for CO varies with alveolar O2 tension. The morphometric method seriously overestimates DmCO because the true tissue-plasma resistance to diffusion is underestimated and the effective membrane utilized for diffusion is overestimated; these errors are accentuated by a low Hct.
Gerald S Zavorsky - One of the best experts on this subject based on the ideXlab platform.
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the need for race specific reference equations for pulmonary Diffusing Capacity for nitric oxide
BMC Pulmonary Medicine, 2021Co-Authors: Gerald S Zavorsky, Ahmad Saleh Almamary, Mobarak Khalid Alqahtani, Shi Huh Samuel Shan, Douglas S GardenhireAbstract:Few reference equations exist for healthy adults of various races for pulmonary Diffusing Capacity for nitric oxide (DLNO). The purpose of this study was to collect pilot data to demonstrate that race-specific reference equations are needed for DLNO. African Americans (blacks) were chosen as the comparative racial group. In 2016, a total of 59 healthy black subjects (27 males and 32 females) were recruited to perform a full battery of pulmonary function tests. In the development of DLNO reference equations, a white reference sample (randomly drawn from a population) matched to the black sample for sex, age, and height was used. Multiple linear regression equations for DLNO, alveolar volume (VA), and pulmonary Diffusing Capacity for carbon monoxide (DLCO) using a 5–6 s breath-hold were developed. Our models demonstrated that sex, age2, race, and height explained 71% of the variance in DLNO and DLCO, with race accounting for approximately 5–10% of the total variance. After normalizing for sex, age2, and height, blacks had a 12.4 and 3.9 mL/min/mmHg lower DLNO and DLCO, respectively, compared to whites. The lower Diffusing Capacity values in blacks are due, in part, to their 0.6 L lower VA (controlling for sex and height). The results of this pilot data reveal small but important and statistically significant racial differences in DLNO and DLCO in adults. Future reference equations should account for racial differences. If these differences are not accounted for, then the risk of falsely diagnosing lung disease increase in blacks when using reference equations for whites.
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week to week variability of pulmonary capillary blood volume and alveolar membrane Diffusing Capacity in patients with heart failure
Respiratory Physiology & Neurobiology, 2021Co-Authors: A. Magini, Gerald S Zavorsky, M. Contini, A. Apostolo, S. Barbieri, Piergiuseppe AgostoniAbstract:Abstract Background Alveolar-capillary membrane Diffusing Capacity for carbon monoxide (DMCO) and pulmonary capillary volume (Vcap) can be estimated by the multi-step Roughton and Foster (RF, original method from 1957) or the single-step NO–CO double diffusion technique (developed in the 1980s). The latter method implies inherent assumptions. We sought to determine which combination of the alveolar membrane Diffusing Capacity for nitric oxide (DMNO) to DMCO ratio, an specific conductance of the blood for NO (θNO) and CO (θCO) gave the lowest week-to-week variability in patients with heart failure. Methods 44 heart failure patients underwent DMCO and Vcap measurements on three occasions over a ten-week period using both RF and double dilution NO-CO techniques. Results When using the double Diffusing method and applying θNO = infinity, the smallest week-to-week coefficient of variation for DMCO was 10 %. Conversely, the RF method derived DMCO had a much greater week-to-week variability (2x higher coefficient of variation) than the DMCO derived via the NO-CO double dilution technique. The DMCO derived from the double diffusion technique most closely matched the DMCO from the RF method when θNO = infinity and DMCO = DLNO/2.42. The Vcap measured week-to-week was unreliable regardless of the method or constants used. Conclusions In heart failure patients, the week-to-week DMCO variability was lowest when using the single-step NO-CO technique. DMCO obtained from double diffusion most closely matched the RF DMCO when DMCO/2.42 and θNO = infinity. Vcap estimation was unreliable with either method.
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the rise in carboxyhemoglobin from repeated pulmonary Diffusing Capacity tests
Respiratory Physiology & Neurobiology, 2013Co-Authors: Gerald S ZavorskyAbstract:Abstract The purpose of this study determined the rise in carboxyhemoglobin percentage (COHb) from repeated pulmonary Diffusing Capacity tests using 5 or 10 s single breath-hold maneuvers. Five male and four female non-smokers [baseline COHb = 1.2 (SD 0.5%)] performed repeated pulmonary Diffusing Capacity testing on two separate days. The days were randomized to either repeated 10 s (0.28% CO), or 5 s (0.28% CO, 55 ppm NO) breath-hold maneuvers. Twenty-two 5 s breath-hold maneuvers, each separated by 4 min rest, raised COHb to 11.1 (1.4)% and minimally raised the methemoglobin percentage (METHb) by 0.3 (0.2)% to a value of 0.8 (0.2)%. After the 22nd test, pulmonary Diffusing Capacity for carbon monoxide (DLCO) was reduced by about 4 mL/min/mmHg, equating to a 0.44% increase in COHb per 5 s breath-hold maneuver and a concomitant 0.35 mL/min/mmHg decrease in DLCO. Pulmonary Diffusing Capacity for nitric oxide (DLNO) was not altered after 22 tests. On another day, the 10 s single breath-hold maneuver increased COHb by 0.64% per test, and reduced DLCO by 0.44 mL/min/mmHg per test. In conclusion, 5 s breath-hold maneuvers do not appreciably raise METHb or DLNO, and DLCO is only significantly reduced when COHb is at least 6%.
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alveolar membrane Diffusing Capacity improves in the morbidly obese after bariatric surgery
Obesity Surgery, 2008Co-Authors: Gerald S Zavorsky, Do Jun Kim, Jeanloup Sylvestre, Nicolas V ChristouAbstract:Morbidly obese individuals may have impaired alveolar-membrane Diffusing Capacity (DmCO). The purpose of this study was to measure pulmonary Diffusing Capacity for NO (DLNO) as an index of DmCO pre- and postbariatric surgery in the morbidly obese. Twenty-one patients [age = 40 ± 9 years, body mass index (BMI) = 48.5 ± 7.2 kg/m2] with an excess weight of 72 ± 17 kg scheduled for bariatric surgery were recruited. Pulmonary function and arterial blood-gases were measured pre- and postsurgery. DmCO was 88 ± 23% of predicted before surgery (p < 0.05). There was loss in BMI and excess weight of 7.7 ± 2.0 kg/m2 and 31 ± 8%, respectively. Because DmCO = DLNO/2.42, the increase in DLNO postsurgery resulted in a normalization of the predicted DmCO to 97 ± 29% predicted, or an improvement of DLNO by 11 ± 18 (95% CI = 3.5, 19.1; p = 0.01) milliliters per minute per millimeter of mercury without any improvement in DLCO. The DLNO/DLCO ratio and alveolar volume both increased, respectively (p < 0.05), and pulmonary capillary blood volume to DmCO ratio decreased postsurgery (p < 0.01). Multiple linear regression revealed that the change in DLNO was most strongly associated with changes in alveolar volume and the waist-to-hip ratio (adjusted r 2 = 0.76; p < 0.001) and was not related to the reduction in the alveolar-to-arterial PO2 difference. Alveolar-membrane diffusion normalizes within 10 weeks after bariatric surgery. This is likely due to the increase in alveolar volume from the reduction in the waist-to-hip ratio.
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a small amount of inhaled nitric oxide does not increase lung Diffusing Capacity
European Respiratory Journal, 2006Co-Authors: Gerald S Zavorsky, Juan M MuriasAbstract:The aim of the present study was to determine: 1) whether 40-50 ppm nitric oxide (NO) increases Diffusing Capacity of the lung for NO (DL,NO) and carbon monoxide (DL,CO), membrane Diffusing Capacity for CO (Dm,CO) and pulmonary capillary blood volume (Vc); 2) the actual number of tests required to provide a reasonable estimate of DL,NO, DL,CO, Dm,CO and Vc; and 3) repeatability of these parameters using the single-breath DL,NO-DL,CO method. In total, 31 subjects performed five single-breath hold manoeuvres at rest, inhaling 43i3 ppm NO together with a standard diffusion mixture. DL,NO (Dm,CO) remained unchanged from the first to fifth trial. However, compared with the first trial, DL,CO and Vc had decreased by the fourth (-4i5%; 95% confidence interval (CI)5-5- -2%) and third trial (-5i7%; 95% CI5-7- -2%), respectively. Repeatability over five trials was 17, 3 and 7m L?min -1 ?mmHg -1 for DL,NO, DL,CO and Dm,CO, respectively, and 13 mL for Vc when Dm,CO5DL,NO/2.42. In conclusion, nitric oxide inhaled during sequential single-breath manoeuvres has no effect on Diffusing Capacity of the lung for nitric oxide and, thus, membrane Diffusing Capacity for carbon monoxide. Since more than two and three trials will lower pulmonary capillary blood volume and Diffusing Capacity of the lung for carbon monoxide, respectively, the average value of only two properly performed trials is suggested.
Robert L Johnson - One of the best experts on this subject based on the ideXlab platform.
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nitric oxide Diffusing Capacity and alveolar microvascular recruitment in sarcoidosis
American Journal of Respiratory and Critical Care Medicine, 2004Co-Authors: Anagha R Phansalkar, Robert L Johnson, Chad M Hanson, Ahmed R Shakir, Connie C W HsiaAbstract:We measured Diffusing capacities for carbon monoxide (DLCO) and nitric oxide, lung volume, and cardiac output by a rebreathing technique at two alveolar O2 tensions (PAO2) at rest and exercise. Membrane Diffusing Capacity for CO (DMCO) and VC were estimated from DLCO by the Roughton-Forster (RF) method and also from simultaneous lung Diffusing Capacity for NO and DLCO measured at one O2 tension (modified RF method). Estimates by these methods agreed closely in normal subjects (Tamhane et al., Chest 2001;120:1850–1856). Using these methods, we studied patients with stages II–III pulmonary sarcoidosis to determine (1) whether the modified RF method accurately estimates DMCO and VC in parenchymal disease and (2) whether sarcoidosis alters recruitment of Diffusing Capacity with respect to cardiac output. In patients, DMCO and VC estimated by the two methods agreed closely. DMCO was disproportionately reduced relative to VC at any given cardiac output, and the slope of the relationship between DLCO and cardiac...
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pulmonary membrane Diffusing Capacity and capillary blood volume measured during exercise from nitric oxide uptake
Chest, 2001Co-Authors: Rahul M Tamhane, Robert L Johnson, Connie C W HsiaAbstract:Study objectives: To validate lung Diffusing Capacity for nitric oxide (DLNO) as an index of conductance of the alveolar-capillary membrane during exercise, we compared DLNO to lung Diffusing Capacity for carbon monoxide (DLCO) and pulmonary membrane Diffusing Capacity for carbon monoxide (DMCO), and compared pulmonary capillary blood volume (Vc) calculated by two methods. Setting and participants: The study was performed at a university medical center involving 12 nonsmoking healthy volunteers (age range, 23 to 79 years). DLCO ,D LNO, cardiac output (Qc), and lung volume were measured simultaneously at rest and during graded ergometer exercise by a rebreath- ing technique. Pulmonary membrane Diffusing Capacity and Vc were compared by (1) the classic technique of Roughton and Forster from DLCO measured at two alveolar oxygen tension (PAO2) levels, and (2) from DLNO and DLCO assuming negligible erythrocyte resistance to nitric oxide (NO) uptake, ie ,D LNO approximately equal to pulmonary membrane Diffusing Capacity for nitric oxide. Results: In all subjects, DLNO increased linearly from rest to exercise; age, Qc, and lung volume were the major determinants of DLNO by stepwise regression analysis. The DLNO/DLCO ratio averaged 3.98 0.38 ( SD) and the DLNO/DMCO ratio averaged 2.49 0.28 irrespective of exercise intensity. Changing PAO2 did not alter DLNO. Brief exposure to 40 ppm of inhaled NO during 16 s of rebreathing did not alter either DLCO or Qc. Estimates of pulmonary membrane Diffusing Capacity and Vc by the two methods showed a strong correlation. Conclusion: Results support DLNO as a direct measure of pulmonary membrane Diffusing Capacity, allowing the estimation of Vc in a single rebreathing maneuver during exercise. The DLNO-DLCO rebreathing technique can be applied clinically in the investigation of pulmonary microvascular regulation. (CHEST 2001; 120:1850-1856)
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red cell distortion and conceptual basis of Diffusing Capacity estimates finite element analysis
Journal of Applied Physiology, 1997Co-Authors: Connie C W Hsia, C J C Chuong, Robert L JohnsonAbstract:Hsia, C. C. W., C. J. C. Chuong, and R. L. Johnson, Jr.Red cell distortion and conceptual basis of Diffusing Capacity estimates: finite element analysis. J. Appl. Physiol. 83(4): 1397–1404, 1997.—T...
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critique of conceptual basis of Diffusing Capacity estimates a finite element analysis
Journal of Applied Physiology, 1995Co-Authors: Connie C W Hsia, C J C Chuong, Robert L JohnsonAbstract:We present a simple geometric model of a pulmonary capillary segment containing a variable number of red blood cells. The pattern of CO transfer from alveolar air to capillary red blood cells in this model is accurately computed by a finite element method and used to explore conceptual flaws in the Roughton-Forster (RF) and morphometric methods of estimating pulmonary Diffusing Capacity for CO. The CO uptakes calculated by the finite element method at two alveolar O2 tensions are introduced into the RF model to determine whether the anatomically defined membrane component of Diffusing Capacity for CO (DmCO) and pulmonary capillary blood volume (Vc) are recovered. The same capillary model is also subjected to standard morphometric analysis. Results are compared at different levels of capillary hematocrit (Hct). The RF method accurately recovers DmCO and Vc at a low Hct but modestly overestimates DmCO and underestimates Vc at higher Hct; errors arise because conductance of the tissue-plasma membrane for CO varies with alveolar O2 tension. The morphometric method seriously overestimates DmCO because the true tissue-plasma resistance to diffusion is underestimated and the effective membrane utilized for diffusion is overestimated; these errors are accentuated by a low Hct.
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estimation of diffusion limitation after pneumonectomy from carbon monoxide Diffusing Capacity
Respiration Physiology, 1991Co-Authors: Connie C W Hsia, J I Carlin, M Ramanathan, Sharon S Cassidy, Robert L JohnsonAbstract:Abstract In three foxhounds, Diffusing Capacity for carbon monoxide (D l CO ) was reduced by 25–30% after left pneumonectomy. Based on previous morphometric data in animals and physiologic data in humans, this reduction should not result in any impairment in gas exchange. However, experimental evidence indicates that diffusion limitation develops during exercise after pneumonectomy. Our objective is to determine whether this diffusion limitation to gas exchange can be predicted from physiologic measurements of D l CO . D l CO measured by the rebreathing technique was translated into Diffusing Capacity for O 2 (D l O 2 ) using an average conversion factor for canids obtained morphometrically (Weibel et al., Respir. Physiol. 54: 173–188, 1983). Arterial O 2 saturation (Sa O 2 ) at various intensities of stead state exercise was calculated from D l O 2 and measured values of O 2 consumption, alveolar P O 2 , hemoglobin and arterial pH, and compared to observed Sa O 2 . After pneumonectomy, Sa O 2 declined progressively with increasing exercise load. In all dogs, the observed pattern of arterial O 2 saturation could be predicted from D l CO measured at similar work loads. The relationship between predicted (Pr) and observed (Ob) Sa O 2 is: Sa O 2 (Pr) = 22.73 + 0.77Sa O 2 (Ob) , r = 0.92. The slope is significantly less than 1.0 ( P l CO is a meaningful indicator of diffusion limitation to gas exchange. In the foxhound, a modest reduction in D l CO significantly impairs O 2 transport during exercise; but other gas exchange abnormalities, e.g. ventilation perfusion inhomogeneity, must also develop.
Michael K Stickland - One of the best experts on this subject based on the ideXlab platform.
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are there sex differences in the capillary blood volume and Diffusing Capacity response to exercise
Journal of Applied Physiology, 2017Co-Authors: Melissa M Bouwsema, Vincent Tedjasaputra, Michael K SticklandAbstract:Women demonstrate lower Diffusing Capacity-to-cardiac output ratio (DlCO/Q), pulmonary capillary blood volume (Vc), and membrane Diffusing Capacity (Dm) compared with height-matched men during exe...
Serpil C Erzurum - One of the best experts on this subject based on the ideXlab platform.
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loss of alveolar membrane Diffusing Capacity and pulmonary capillary blood volume in pulmonary arterial hypertension
Respiratory Research, 2013Co-Authors: Samar Farha, Daniel Laskowski, Deepa George, Margaret M Park, W Wilson H Tang, Raed A Dweik, Serpil C ErzurumAbstract:Reduced gas transfer in patients with pulmonary arterial hypertension (PAH) is traditionally attributed to remodeling and progressive loss of pulmonary arterial vasculature that results in decreased capillary blood volume available for gas exchange. We tested this hypothesis by determination of lung Diffusing Capacity (DL) and its components, the alveolar capillary membrane Diffusing Capacity (Dm) and lung capillary blood volume (Vc) in 28 individuals with PAH in comparison to 41 healthy individuals, and in 19 PAH patients over time. Using single breath simultaneous measure of diffusion of carbon monoxide (DLCO) and nitric oxide (DLNO), DL and Dm were respectively determined, and Vc calculated. Dm and Vc were evaluated over time in relation to standard clinical indicators of disease severity, including brain natriuretic peptide (BNP), 6-minute walk distance (6MWD) and right ventricular systolic pressure (RVSP) by echocardiography. Both DLCO and DLNO were reduced in PAH as compared to controls and the lower DL in PAH was due to loss of both Dm and Vc (all p < 0.01). While DLCO of PAH patients did not change over time, DLNO decreased by 24 ml/min/mmHg/year (p = 0.01). Consequently, Dm decreased and Vc tended to increase over time, which led to deterioration of the Dm/Vc ratio, a measure of alveolar-capillary membrane functional efficiency without changes in clinical markers. The findings indicate that lower than normal gas transfer in PAH is due to loss of both Dm and Vc, but that deterioration of Dm/Vc over time is related to worsening membrane diffusion.