Comparison of the SpO2/FIO2 ratio and the PaO2/FIO2 ratio in patients with acute lung injury or ARDS

BACKGROUND

The diagnostic criteria for acute lung injury (ALI) and ARDS utilize the Pao(2)/fraction of inspired oxygen (Fio(2)) [P/F] ratio measured by arterial blood gas analysis to assess the degree of hypoxemia. We hypothesized that the pulse oximetric saturation (Spo(2))/Fio(2) (S/F) ratio can be substituted for the P/F ratio in assessing the oxygenation criterion of ALI.

METHODS

Corresponding measurements of Spo(2) (values </= 97%) and Pao(2) from patients enrolled in the ARDS Network trial of a lower tidal volume ventilator strategy (n = 672) were compared to determine the relationship between S/F and P/F. S/F threshold values correlating with P/F ratios of 200 (ARDS) and 300 (ALI) were determined. Similar measurements from patients enrolled in the ARDS Network trial of lower vs higher positive end-expiratory pressure (n = 402) were utilized for validation.

RESULTS

In the derivation data set (2,613 measurements), the relationship between S/F and P/F was described by the following equation: S/F = 64 + 0.84 x (P/F) [p < 0.0001; r = 0.89). An S/F ratio of 235 corresponded with a P/F ratio of 200, while an S/F ratio of 315 corresponded with a P/F ratio of 300. The validation database (2,031 measurements) produced a similar linear relationship. The S/F ratio threshold values of 235 and 315 resulted in 85% sensitivity with 85% specificity and 91% sensitivity with 56% specificity, respectively, for P/F ratios of 200 and 300.

CONCLUSION

S/F ratios correlate with P/F ratios. S/F ratios of 235 and 315 correlate with P/F ratios of 200 and 300, respectively, for diagnosing and following up patients with ALI and ARDS.

Histopathologic subsets of fibrosing alveolitis in patients with systemic sclerosis and their relationship to outcome

Fibrosing alveolitis associated with systemic sclerosis (FASSc) has a better prognosis than idiopathic pulmonary fibrosis. In view of recent reports that idiopathic nonspecific interstitial pneumonia (NSIP) has a better prognosis than idiopathic usual interstitial pneumonia (UIP), we classified histologic appearances of surgical lung biopsies performed in 80 patients with FASSc. NSIP (n = 62, 77.5%), subcategorized as cellular NSIP (n = 15) and fibrotic NSIP (n = 47) was much more prevalent than UIP (n = 6), end-stage lung disease (ESL, n = 6), or other patterns (n = 6). There were 25 deaths (NSIP 16/62, 26%; UIP/ESL 6/12, 50%). Five-year survival differed little between NSIP (91%) and UIP/ESL (82%); mortality was associated with lower initial carbon monoxide diffusing capacity (DL(CO)) and FVC levels (p = 0.004 and p = 0.007, respectively). Survival and serial FVC and DL(CO) trends did not differ between cellular and fibrotic NSIP. Increased mortality in NSIP was associated with lower initial DL(CO) levels (p = 0.04), higher BAL eosinophil levels (p = 0.03), and deterioration in DL(CO) levels during the next 3 years (p < 0.005). We conclude that NSIP is the histopathologic pattern in most patients with FASSc. However, outcome is linked more strongly to disease severity at presentation and serial DL(CO) trends than to histopathologic findings.

Airflow limitation and airway dimensions in chronic obstructive pulmonary disease

RATIONALE

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation caused by emphysema and/or airway narrowing. Computed tomography has been widely used to assess emphysema severity, but less attention has been paid to the assessment of airway disease using computed tomography.

OBJECTIVES

To obtain longitudinal images and accurately analyze short axis images of airways with an inner diameter>or=2 mm located anywhere in the lung with new software for measuring airway dimensions using curved multiplanar reconstruction.

METHODS

In 52 patients with clinically stable COPD (stage I, 14; stage II, 22; stage III, 14; stage IV, 2), we used the software to analyze the relationship of the airflow limitation index (FEV1, % predicted) with the airway dimensions from the third to the sixth generations of the apical bronchus (B1) of the right upper lobe and the anterior basal bronchus (B8) of the right lower lobe.

MEASUREMENTS AND MAIN RESULTS

Airway luminal area (Ai) and wall area percent (WA%) were significantly correlated with FEV1 (% predicted). More importantly, the correlation coefficients (r) improved as the airways became smaller in size from the third (segmental) to sixth generations in both bronchi (Ai: r=0.26, 0.37, 0.58, and 0.64 for B1; r=0.60, 0.65, 0.63, and 0.73 for B8).

CONCLUSIONS

We are the first to use three-dimensional computed tomography to demonstrate that airflow limitation in COPD is more closely related to the dimensions of the distal (small) airways than proximal (large) airways.

Respiratory function in patients post-infection by COVID-19: a systematic review and meta-analysis

BACKGROUND

Evidence suggests lungs as the organ most affected by coronavirus disease 2019 (COVID-19). The literature on previous coronavirus infections reports that patients may experience persistent impairment in respiratory function after being discharged. Our objective was to determine the prevalence of restrictive pattern, obstructive pattern and altered diffusion in patients post-COVID-19 infection and to describe the different evaluations of respiratory function used with these patients.

METHODS

A systematic review was conducted in five databases. Studies that used lung function testing to assess post-infection COVID-19 patients were included for review. Two independent reviewers analysed the studies, extracted the data and assessed the quality of evidence.

RESULTS

Of the 1973 reports returned by the initial search, seven articles reporting on 380 patients were included in the data synthesis. In the sensitivity analysis, we found a prevalence of 0.39 (CI 0.24-0.56, p < 0.01, I2 = 86%), 0.15 (CI 0.09-0.22, p = 0.03, I2 = 59%), and 0.07 (CI 0.04-0.11, p = 0.31, I2 = 16%) for altered diffusion capacity of the lungs for carbon monoxide (DLCO), restrictive pattern and obstructive pattern, respectively.

CONCLUSION

Post-infection COVID-19 patients showed impaired lung function; the most important of the pulmonary function tests affected was the diffusion capacity.

Significance of pulmonary arterial pressure and diffusion capacity of the lung as prognosticator in patients with idiopathic pulmonary fibrosis

STUDY OBJECTIVES

To evaluate the long-term clinical course of patients with idiopathic pulmonary fibrosis (IPF) complicated with pulmonary arterial hypertension.

DESIGN

Prospective analysis of consecutive IPF patients undergoing initial workup with right-heart catheterization (RHC) and pulmonary function testing (PFT). Pulmonary arterial pressure (PAP) and diffusion capacity of the lung for carbon monoxide (Dlco) were focused on.

SETTING

University hospital.

PATIENTS

Seventy-eight patients with IPF (67 men, 11 women; diagnosis by pathology, n = 59; clinical diagnosis, n = 19) had been followed up after initial workup for a maximum of 14 years.

MEASUREMENTS AND RESULTS

RHC data on 61 patients and PFT data on 52 patients were available. Five-year survival rates were 62.2% in the normal-PAP group (mean PAP < 17 mm Hg, n = 37) and 16.7% in the high-PAP group (mean PAP > 17 mm Hg, n = 24) [p < 0.001]; 70.4% in the preserved-Dlco group (percentage of predicted > 40%, n = 27) and 20.0% in the low-Dlco group (percentage of predicted < 40%, n = 25) [p < 0.001]; and 82.6% in group 1 (normal PAP and preserved Dlco, n = 23) and 15.6% in group 2 (high PAP, low Dlco, or both, n = 32) [p < 0.0001]. The relative risks of mortality within 5 years after RHC were 2.20 (95% confidence interval [CI], 1.40 to 3.45) in the high-PAP group, 2.70 (95% CI, 1.46 to 4.99) in the low-Dlco group, and 4.85 (95% CI, 1.97 to 11.97) in group 2.

CONCLUSION

Dlco was a critical factor for evaluating disease status and prognosis, and PAP status provided feasible information in the initial workup of IPF patients.

Pulmonary lymphangioleiomyomatosis. A study of 69 patients. Groupe d'Etudes et de Recherche sur les Maladies "Orphelines" Pulmonaires (GERM"O"P)

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disorder of unknown cause characterized by peribronchial, perivascular, and perilymphatic proliferation of abnormal smooth muscle cells leading to cystic lesions. The hypothesis of hormonal dependence and the effectiveness of hormonal therapy have not yet been demonstrated conclusively, and the prevalence of extrathoracic manifestations and the survival of patients with LAM are somewhat contradictory. A multicentric retrospective study was conducted in an attempt to describe better the initial features, the diagnostic procedures, the associated lesions, and, above all, the management and course of LAM in a large homogeneous series of 69 stringently selected patients, with a majority of cases diagnosed since 1990. The aim of the study, based on a review of the literature, also was to provide a comprehensive view of this uncommon disease. The clinical features were in keeping with previous studies, but we found that exertional dyspnea and pneumothorax were the most common features, and chylous involvement was less frequent. LAM was diagnosed after menopause in about 10% of cases. The onset of LAM occurred during pregnancy in 20% of cases, and a clear exacerbation of LAM was observed in 14% of cases during pregnancy. Pulmonary LAM was diagnosed on lung histopathology in 83% of cases, but renal angiomyolipoma, observed in 32% of our patients, may be a useful diagnostic criterion when associated with typical multiple cysts on chest CT scan or with chylous effusion. Chest CT scan was more informative than chest X-ray (normal in 9% of cases), and may be indicated in spontaneous pneumothorax or renal angiomyolipoma in women of childbearing age. About 40% of the patients had a normal initial spirometry, while an obstructive ventilatory defect (44%), a restrictive ventilatory defect (23%), was observed in other patients. Initial diffusing capacity for carbon monoxide was frequently decreased (82%). Hormonal therapy was administered in 57 patients, but a clear > or = 15% improvement of FEV1 was observed in only 4 evaluable patients, treated with tamoxifen and progestogens (n = 2), progestogen (n = 1), and oophorectomy (n = 1). Probably 1 of the most urgent needs for clinical research in LAM is to test the currently available hormonal treatments in the context of international multicenter prospective controlled studies. Pleurodesis was performed in 40 patients. Lung transplantation was performed in 13 patients, 7.8 +/- 5.2 years after onset of LAM, in whom the mean FEV1 was 0.57 +/- 0.15 L. After a follow-up of 2.3 +/- 2.2 years, 9 patients were alive. Mean follow-up from onset of disease to either death or closing date was 8.2 +/- 6.3 years. Overall survival was better than usually reported in LAM, and Kaplan-Meier plot showed survival probabilities of 91% after 5 years, 79% after 10 years, and 71% after 15 years of disease duration.

Physiology of fetal lung fluid clearance and the effect of labor

Respiratory morbidity in near term (> or =34 and <37 weeks) infants delivered spontaneously or by elective cesarean section (ECS) has been well documented in the literature, and accounts for a significant number of admissions to intensive care units among these neonates. Given the high rates of near-term deliveries in the USA and worldwide, the public health and economic impact of morbidity in this subgroup is considerable. Causes of respiratory distress include transient tachypnea of the newborn (TTNB), surfactant deficiency, pneumonia, and pulmonary hypertension. There is considerable evidence that physiologic events in the last few weeks of pregnancy coupled with the onset of spontaneous labor are accompanied by changes in the hormonal milieu of the fetus and its mother, resulting in rapid maturation and preparation of the fetus for delivery and neonatal transition. A surge in endogenous steroids and catecholamines accompanies term gestation and spontaneous vaginal delivery, and is responsible for some of the maturational effects. Rapid clearance of fetal lung fluid clearance plays a key role in the transition to air breathing. The bulk of this fluid clearance is mediated by transepithelial sodium reabsorption through amiloride-sensitive sodium channels in the alveolar epithelial cells with only a limited contribution from mechanical factors and Starling forces. Disruption of this process can lead to retention of fluid in air spaces, setting the stage for alveolar hypoventilation. When infants are delivered near-term, especially by cesarean section (repeat or primary) before the onset of spontaneous labor, the fetus is often deprived of these hormonal changes, making the neonatal transition more difficult. This chapter discusses the physiologic mechanisms underlying fetal lung fluid absorption and explores potential strategies for facilitating neonatal transition.

Comparison of discriminative properties among disease-specific questionnaires for measuring health-related quality of life in patients with chronic obstructive pulmonary disease

Three disease-specific, health-related quality of life (HRQL) questionnaires have been introduced to assess patients with chronic obstructive pulmonary disease (COPD): the St. George's Respiratory Questionnaire (SGRQ), the Breathing Problems Questionnaire (BPQ), and the Chronic Respiratory Disease Questionnaire (CRQ). The purpose of the present study was to make comparisons between the SGRQ, the BPQ, and the CRQ in their discriminative properties, and to clarify the characteristics of each questionnaire. One hundred forty-three patients with mild to severe COPD completed pulmonary function tests, progressive cycle ergometer testing for exercise capacity, assessment of dyspnea, anxiety, and depression, and assessment of HRQL. The frequency distributions of the questionnaire scores showed that the SGRQ and the CRQ were normally distributed and that the BPQ was skewed toward low scores. Relationships between all dimensions of the three questionnaires were significant (correlation coefficients [Rs] = 0.74 to 0.86). The three questionnaires had significant but weak correlations (Rs = -0.24 to -0.36) with some physiologic variables (VC, FEV1, and DL(CO)/VA) and mild to moderate correlations with exercise capacity and assessment of dyspnea, anxiety, and depression. Stepwise multiple regression analyses revealed that the Baseline Dyspnea Index (BDI) score, anxiety by the Hospital Anxiety Depression Scale (HAD), and maximal oxygen uptake (VO2max) accounted for 61% of the variance in the SGRQ and that the BDI and anxiety of the HAD accounted for 53 and 49% of the variance in the BPQ and the CRQ, respectively. Dyspnea and psychologic status impacted the HRQL in patients with COPD. Although no substantial differences between the SGRQ, the BPQ, and the CRQ were evident in the correlations with physiologic parameters and the influential factors, the BPQ was found to be less discriminatory than the SGRQ and the CRQ in evaluating HRQL cross-sectionally.

The physiologic evaluation of patients with lung cancer being considered for resectional surgery

The preoperative physiologic assessment of a patient being considered for surgical resection of lung cancer must consider the immediate perioperative risks from comorbid cardiopulmonary disease, the long-term risks of pulmonary disability, and the threat to survival due to inadequately treated lung cancer. As with any planned major operation, especially in a population predisposed to atherosclerotic cardiovascular disease by cigarette smoking, a cardiovascular evaluation is an important component in assessing perioperative risks. Measuring the FEV(1) and the diffusing capacity of the lung for carbon monoxide (DLCO) measurements should be viewed as complementary physiologic tests for assessing risk related to pulmonary function. If there is evidence of interstitial lung disease on radiographic studies or undue dyspnea on exertion, even though the FEV(1) may be adequate, a DLCO should be obtained. In patients with abnormalities in FEV(1) or DLCO identified preoperatively, it is essential to estimate the likely postresection pulmonary reserve. The amount of lung function lost in lung cancer resection can be estimated by using either a perfusion scan or the number of segments removed. A predicted postoperative FEV(1) or DLCO < 40% indicates an increased risk for perioperative complications, including death, from lung cancer resection. Exercise testing should be performed in these patients to further define the perioperative risks prior to surgery. Formal cardiopulmonary exercise testing is a sophisticated physiologic testing technique that includes recording the exercise ECG, heart rate response to exercise, minute ventilation, and oxygen uptake per minute, and allows calculation of maximal oxygen consumption (.VO(2)max). Risk for perioperative complications can generally be stratified by .VO(2)max. Patients with preoperative .VO(2)max > 20 mL/kg/min are not at increased risk of complications or death; .VO(2)max< 15 mL/kg/min indicates an increased risk of perioperative complications; and patients with .VO(2)max < 10 mL/kg/min have a very high risk for postoperative complications. Alternative types of exercise testing include stair climbing, the shuttle walk, and the 6-min walk. Although often not performed in a standardized manner, stair climbing can predict .VO(2)max. In general terms, patients who can climb five flights of stairs have O(2)max > 20 mL/kg/min. Conversely, patients who cannot climb one flight of stairs have .VO(2)max < 10 mL/kg/min. Data on the shuttle walk and 6-min walk are limited, but patients who cannot complete 25 shuttles on two occasions will have .VO(2)max < 10 mL/kg/min. Desaturation during an exercise test has been associated with an increased risk for perioperative complications. Lung volume reduction surgery (LVRS) for patients with severe emphysema is a controversial procedure. Some reports document substantial improvements in lung function, exercise capability, and quality of life in highly selected patients with emphysema following LVRS. Case series of patients referred for LVRS indicate that perhaps 3 to 6% of these patients may have coexisting lung cancer. Anecdotal experience from these case series suggest that patients with extremely poor lung function can tolerate combined LVRS and resection of the lung cancer with an acceptable mortality rate and good postoperative outcomes. Combining LVRS and lung cancer resection should probably be limited to those patients with heterogeneous emphysema, particularly emphysema limited to the lobe containing the tumor.

Airway nitric oxide diffusion in asthma: Role in pulmonary function and bronchial responsiveness

If the nitric oxide (NO) diffusing capacity of the airways (DNO) is the quantity of NO diffusing per unit time into exhaled gas (q) divided by the difference between the concentration of NO in the airway wall (Cw) and lumen, then DNO and C(w) can be estimated from the relationship between exhaled NO concentration and expiratory flow. In 10 normal subjects and 25 asthmatic patients before and after treatment with inhaled beclomethasone, DNO averaged 6.8 +/- 1.2, 25.5 +/- 3.8, and 22.3 +/- 2.7 nl/s/ppb x 10(-3), respectively; C(w) averaged 149 +/- 31.9, 255.3 +/- 46.4, and 108.3 +/- 14.3 ppb, respectively; and DNOC(w) (the maximal from diffusion) averaged 1,020 +/- 157.5, 6,512 +/- 866, and 2,416 +/- 208.5 nl/s x 10(-3), respectively. DNO and DNOC(w) in the asthmatic subjects before and after steroids were greater than in normal subjects (p < 0.0001), but C(w) was not different. Within asthmatic subjects, steroids caused C(w) and DNOC(w) to fall (p < 0.0001), but DNO was unchanged. DNOC(w) after steroids, presumably reflecting maximal diffusion of constitutive NO, was positively correlated with methacholine PC(20) and FEV(1)/FVC before or after steroids. The increased DNO measured in asthmatic patients may reflect upregulation of nonadrenergic, noncholinergic, NO-producing nerves in airways in compensation for decreased sensitivity of airway smooth muscle to the relaxant effects of endogenous NO.

Subacute and chronic bird breeder hypersensitivity pneumonitis: sequential evaluation with CT and correlation with lung function tests and bronchoalveolar lavage

PURPOSE

To evaluate lung involvement in the subacute (group 1) and chronic (group 2) stages of bird breeder hypersensitivity pneumonitis.

MATERIALS AND METHODS

Computed tomographic (CT) findings in 45 patients were correlated with pulmonary function testing and bronchoalveolar lavage. Twenty-seven patients underwent sequential CT examination 0.3-4 years apart, with functional evaluation in 20 of them.

RESULTS

In group 1, CT showed diffuse micronodules, ground-glass attenuation, focal air trapping or emphysema, and mild fibrotic changes, with normal lung volumes but impaired diffusing capacity and a predominant lymphocyte alveolitis. In group 2, two categories of chronic forms were identified at CT on the basis of presence or absence of honeycombing. After cessation of exposure, CT showed a return to normal or dramatic improvement in group 1 and considerable reduction in ground-glass attenuation and micronodules in group 2. CT depicted no fibrotic or emphysematous changes during follow-up.

CONCLUSION

Subacute bird breeder hypersensitivity pneumonitis may share CT features with other types of hypersensitivity pneumonitis. CT may help in identification of emphysematous and fibrotic forms of chronic disease.

Examination of the carbon monoxide diffusing capacity (DL(CO)) in relation to its KCO and VA components

The single-breath carbon monoxide diffusing capacity (DL(CO)) is the product of two measurements during breath holding at full inflation: (1) the rate constant for carbon monoxide uptake from alveolar gas (kco [minute(-1)]) and (2) the "accessible" alveolar volume (Va). kco expressed per mm Hg alveolar dry gas pressure (Pb*) as kco/Pb*, and then multiplied by Va, equals Dl(CO); thus, Dl(CO) divided by Va (DL(CO)/Va, also called Kco) is only kco/Pb* in different units, remaining, essentially, a rate constant. The notion that DL(CO)/Va "corrects" DL(CO) for reduced Va is physiologically incorrect, because DL(CO)/Va is not constant as Va changes; thus, the term Kco reflects the physiology more appropriately. Crucially, the same DL(CO) may occur with various combinations of Kco and Va, each suggesting different pathologies. Decreased Kco occurs in alveolar-capillary damage, microvascular pathology, or anemia. Increased Kco occurs with (1) failure to expand normal lungs to predicted full inflation (extrapulmonary restriction); or (2) increased capillary volume and flow, either globally (left-to-right intracardiac shunting) or from flow and volume diversion from lost or damaged units to surviving normal units (e.g., pneumonectomy). Decreased Va occurs in (1) reduced alveolar expansion, (2) alveolar damage or loss, or (3) maldistribution of inspired gases with airflow obstruction. Kco will be greater than 120% predicted in case 1, 100-120% in case 2, and 40-120% in case 3, depending on pathology. Kco and Va values should be available to clinicians, as fundamental to understanding the clinical implications of DL(CO). The diffusing capacity for nitric oxide (DL(NO)), and the DL(NO)/DL(CO) ratio, provide additional insights.

Reduced alveolar-capillary membrane diffusing capacity in chronic heart failure. Its pathophysiological relevance and relationship to exercise performance

BACKGROUND

The pulmonary diffusing capacity for carbon monoxide (DLCO) is reduced in chronic heart failure (CHF) and is an independent predictor of peak exercise oxygen uptake. The pathophysiological basis for this remains unknown. The aim of this study was to partition DLCO into its membrane conductance (DM) and capillary blood volume components (Vc) and to assess if alveolar-capillary membrane function correlated with functional status, exercise capacity, and pulmonary vascular resistance.

METHODS AND RESULTS

The classic Roughton and Forster method of measuring single-breath DLCO at varying alveolar oxygen concentrations was used to determine DM and Vc in 15 normal subjects and 50 patients with CHF. All performed symptom-limited maximal bicycle exercise tests with respiratory gas analysis; 15 CHF patients underwent right heart catheterization. DLCO was significantly reduced in CHF patients compared with normal subjects, predominantly because of a reduction in DM (7.0 +/- 2.6 versus 12.9 +/- 3.8 versus 20.0 +/- 6.1 mmol.min-1.kPa-1 in New York Heart Association class III, class II, and normal subjects, respectively, P < .0001), even when the reduction in lung volumes was accounted for by the division of DM by the effective alveolar volume. The Vc component of DLCO was not impaired. DM significantly correlated with maximal exercise oxygen uptake (r = .72, P < .0001) and inversely correlated with pulmonary vascular resistance (r = .65, P < .01) in CHF.

CONCLUSIONS

Reduced alveolar-capillary membrane diffusing capacity is the major component of impaired pulmonary gas transfer in CHF, correlating with maximal exercise capacity and functional status. DM may be a useful marker for the alveolar-capillary barrier damage induced by raised pulmonary capillary pressure.

Early emphysematous changes in asymptomatic smokers: detection with 3He MR imaging

PURPOSE

To prospectively compare apparent diffusion coefficient (ADC) measurements derived from diffusion-weighted hyperpolarized helium 3 (3He) magnetic resonance (MR) imaging with functional and structural findings using spirometric tests and thin-section computed tomography (CT) of the lungs in asymptomatic smokers and healthy nonsmokers of similar age.

MATERIALS AND METHODS

All studies were HIPAA compliant and were approved by the institutional review board. Informed consent was obtained. Ventilation and diffusion-weighted 3He MR images were obtained in healthy subjects: 11 smokers (five women, six men; mean age, 47 years+/-18 [standard deviation]; range, 23-73 years) and eight nonsmokers (<100 cigarettes in lifetime) (four women, four men; mean age, 46 years+/-16; range, 23-69 years). Mean ADC values for smokers and nonsmokers were compared with spirometric values, diffusing capacity of the lung for carbon monoxide (Dlco), age, and pack-years with Spearman rank correlation coefficient (rs) and multiple linear regression analysis. Mean ADC value and thin-section CT emphysema index of relative area less than -950 HU (RA950) were compared on a regional basis by using linear mixed-effect models.

RESULTS

Mean ADC values and number of pack-years were significantly correlated (rs=0.60; 95% confidence interval (CI): 0.21, 1.00; P=.007); relationship remained significant after adjustment for age (P=.003). Dlco was strongly correlated with pack-years (rs=-0.63; 95% CI: -0.97, -0.29; P=.004). Negative correlations between mean ADC values and percentage predicted Dlco (rs=-0.79; 95% CI: -0.93, -0.64; P<.001) and the ratio of forced expiratory volume in 1 second to forced vital capacity (rs=-0.72; 95% CI: -0.92, -0.52; P=.001) were statistically significant. Correlations between spirometric values or RA950 and number of pack-years were not significant (.05 level).

CONCLUSION

Correlations between mean ADC values and pulmonary function test measurements for diagnosing emphysema, especially Dlco, were statistically significant.

Pulmonary Hypertension and Pulmonary Function Testing in Idiopathic Pulmonary Fibrosis

BACKGROUND

Pulmonary hypertension (PH) is commonly seen in patients with idiopathic pulmonary fibrosis (IPF). We sought to examine the relationship between pulmonary function tests (PFTs), including the percentage of predicted FVC (FVC%), percentage of predicted total lung capacity, percentage of predicted diffusing capacity of the lung for carbon monoxide (Dlco%), the composite physiologic index (CPI), and PH. The ability of FVC%, Dlco%, and FVC%/Dlco% ratio to predict underlying PH was assessed.

METHODS

Retrospective review of IPF patients seen at a tertiary referral center over an 8-year interval in whom both PFT and right-heart catheterization data were available.

RESULTS

The study cohort consisted of 118 patients, of whom 48 patients (40.7%) had PH. There was no correlation between measures of lung volumes or the CPI with underlying PH. There was a modest association between Dlco% and PH, with Dlco% < 30 having a twofold-higher prevalence of PH (56.4%) compared to Dlco% >/= 30 (28.6%). Cardiac dysfunction might have played a small role, since 16.1% of the patients had an associated elevated pulmonary capillary wedge pressure. There was a trend to a higher prevalence and greater severity of PH in those patients with FVC% > 70 compared to the group with FVC% < 40.

CONCLUSION

PH is common in patients with IPF. There is a poor correlation between lung function measures and PH, suggesting that factors other than fibrosis may play a role in the etiology. The unexpected high prevalence and severity of PH in patients with well-maintained lung function have implications for the prognosis and management of the disease.

High-resolution CT diagnosis of emphysema in symptomatic patients with normal chest radiographs and isolated low diffusing capacity

To determine the prevalence of "nonobstructive" (impairment of gas transfer) emphysema in a select population of smokers with dyspnea, a retrospective study of patients with emphysema evident at high-resolution computed tomography (HRCT) was undertaken. Four hundred seventy HRCT studies were reviewed. In 47 cases, centrilobular emphysema was the dominant or sole parenchymal abnormality. Concomitant chest radiographs were available in 41 of these cases; 16 of the 41 lacked radiographic findings of emphysema. Among these 16 patients, pulmonary function testing revealed 10 to have normal flow rates (ratio of forced expiratory volume in 1 second to forced vital capacity and forced expiratory volume in 1 second greater than 80% predicted) and impaired gas transfer (single-breath carbon monoxide diffusing capacity [DLCOSB] less than 80% predicted). With the exclusion of one patient with congestive heart failure from the group of 10, the severity of emphysema at HRCT correlated inversely with DLCOSB (r = -.643). These results indicate that HRCT allows detection of emphysema in symptomatic patients when chest radiographs and pulmonary function tests are nondiagnostic.

Long-term durable benefit after whole lung lavage in pulmonary alveolar proteinosis

Whole lung lavage (WLL) is still the gold-standard therapy for pulmonary alveolar proteinosis (PAP). The few studies on the duration of the effect of WLL, belonging to a rather remote period, show significant but transient benefits. In 21 patients with idiopathic PAP, the duration of any benefit and, in 16 of them, the time course of lung function improvement (at baseline, 1 week, 6 months, 1 yr and then every 2 yrs after WLL) were evaluated. The present WLL technique takes longer, is invasively monitored and partially modified with respect to past techniques. More than 70% of patients remained free from recurrent PAP at 7 yrs. The bulk of the improvement in spirometric results was almost completely gained in the immediate post-WLL period due to the efficient clearance of the alveoli. At a median of 5 yrs, recovery of diffusing capacity of the lung for carbon monoxide was incomplete (75 +/- 19% of the predicted value) and there were residual gas exchange abnormalities (alveolar to arterial oxygen tension difference 3.6 +/- 1.5 kPa (27 +/- 11 mmHg)) and exercise limitation, probably explained by engorgement of lymphatic vessels. In conclusion, whole lung lavage for idiopathic pulmonary alveolar proteinosis is currently a safe procedure in an experienced setting, and provides long-lasting benefits in the majority of patients.

Pulmonary function in primary pulmonary hypertension

OBJECTIVES

The study was done to ascertain the degree to which abnormalities in resting lung function correlate with the disease severity of patients with primary pulmonary hypertension (PPH).

BACKGROUND

Patients with PPH are often difficult to diagnose until several years after the onset of symptoms. Despite the seriousness of the disorder, the diagnosis of PPH is often delayed because it is unsuspected and requires invasive measurements. Although PPH often causes abnormalities in resting lung function, these abnormalities have not been shown to be statistically significant when correlated with other measures of PPH severity.

METHODS

Resting lung mechanics and diffusing capacity for carbon monoxide DL(CO) were assessed in 79 patients whose findings conformed to the classical diagnostic criteria of PPH and who had no evidence of secondary causes of pulmonary hypertension. These findings were correlated with severity of disease as assessed by cardiac catheterization, New York Heart Association (NYHA) class, and cardiopulmonary exercise testing.

RESULTS

When PPH patients were first evaluated at our referral clinic, the DL(CO) and lung volumes were decreased in approximately three-quarters and one-half, respectively. The decreases in DL(CO), and to a lesser extent lung volumes, correlated significantly with decreases in peak oxygen uptake (reflecting maximum cardiac output), peak oxygen pulse (reflecting maximum stroke volume), and anaerobic threshold (reflecting sustainable exercise capacity) and higher NYHA class.

CONCLUSIONS

Patients with PPH commonly have abnormalities in lung mechanics and DL(CO) levels that correlate significantly with disease severity. These measurements can be useful in evaluating patients with unexplained dyspnea and fatigue.

Hyperpolarized (129)Xe MRI: a viable functional lung imaging modality?

The majority of researchers investigating hyperpolarized gas MRI as a candidate functional lung imaging modality have used (3)He as their imaging agent of choice rather than (129)Xe. This preference has been predominantly due to, (3)He providing stronger signals due to higher levels of polarization and higher gyromagnetic ratio, as well as its being easily available to more researchers due to availability of polarizers (USA) or ease of gas transport (Europe). Most researchers agree, however, that hyperpolarized (129)Xe will ultimately emerge as the imaging agent of choice due to its unlimited supply in nature and its falling cost. Our recent polarizer technology delivers vast improvements in hyperpolarized (129)Xe output. Using this polarizer, we have demonstrated the unique property of xenon to measure alveolar surface area noninvasively. In this article, we describe our human protocols and their safety, and our results for the measurement of the partial pressure of pulmonary oxygen (pO(2)) by observation of (129)Xe signal decay. We note that the measurement of pO(2) by observation of (129)Xe signal decay is more complex than that for (3)He because of an additional signal loss mechanism due to interphase diffusion of (129)Xe from alveolar gas spaces to septal tissue. This results in measurements of an equivalent pO(2) that accounts for both traditional T(1) decay from pO(2) and that from interphase diffusion. We also provide an update on new technological advancements that form the foundation for an improved compact design polarizer as well as improvements that provide another order-of-magnitude scale-up in xenon polarizer output.

Simultaneous measurement of nitric oxide production by conducting and alveolar airways of humans

Human airways produce nitric oxide (NO), and exhaled NO increases as expiratory flow rates fall. We show that mixing during exhalation between the NO produced by the lower, alveolar airways (VL(NO)) and the upper conducting airways (VU(NO)) explains this phenomenon and permits measurement of VL(NO), VU(NO), and the NO diffusing capacity of the conducting airways (DU(NO)). After breath holding for 10-15 s the partial pressure of alveolar NO (PA) becomes constant, and during a subsequent exhalation at a constant expiratory flow rate the alveoli will deliver a stable amount of NO to the conducting airways. The conducting airways secrete NO into the lumen (VU(NO)), which mixes with PA during exhalation, resulting in the observed expiratory concentration of NO (PE). At fast exhalations, PA makes a large contribution to PE, and, at slow exhalations, NO from the conducting airways predominates. Simple equations describing this mixing, combined with measurements of PE at several different expiratory flow rates, permit calculation of PA, VU(NO), and DU(NO). VL(NO) is the product of PA and the alveolar airway diffusion capacity for NO. In seven normal subjects, PA = 1.6 +/- 0.7 x 10(-6) (SD) Torr, VL(NO) = 0.19 +/- 0.07 microl/min, VU(NO) = 0.08 +/- 0.05 microl/min, and DU(NO) = 0.4 +/- 0.4 ml. min(-1). Torr(-1). These quantitative measurements of VL(NO) and VU(NO) are suitable for exploring alterations in NO production at these sites by diseases and physiological stresses.

Human pulmonary imaging and spectroscopy with hyperpolarized 129Xe at 0.2T

RATIONALE AND OBJECTIVES

Using a novel (129)Xe polarizer with high throughput (1-2 L/hour) and high polarization (approximately 55%), our objective was to demonstrate and characterize human pulmonary applications at 0.2T. Specifically, we investigated the ability of (129)Xe to measure the alveolar surface area per unit volume of gas, S(A)/V(gas).

MATERIALS AND METHODS

Variable spin echo time (TE) gradient and radiofrequency (RF) echoes were used to obtain estimates of the lung's contribution to both T(2)* and T(2). Standard multislice ventilation images were obtained and signal-to-noise ratio (SNR) determined. Whole-lung, time-dependent measurements of (129)Xe diffusion from gas to septal tissue were obtained with a chemical shift saturation recovery (CSSR) method. Four healthy subjects were studied, and the Butler et al CSSR formalism (J Phys Condensed Matter 2002; 14:L297-L304) was used to calculate S(A)/V(gas). A single-breath version of the xenon transfer contrast (SB-XTC) method was implemented and used to image (129)Xe diffusion between alveolar gas and septal tissue. A direct comparison of CSSR and SB-XTC was performed.

RESULTS

T(2)*=135+/-29 ms amd T(2)=326.2+/-9.5 ms. Maximum SNR=36 for ventilation images from inhalation of 1L 86% (129)Xe and voxel volume =0.225 mL. CSSR analysis showed S(A)/V(gas) decreased with increasing lung volume in a manner very similar to that observed from histology measurements; however, the absolute value of S(A)/V(gas) was approximately 40% smaller than histology values. SB-XTC images in different postures demonstrate gravitationally dependent values. Initial comparison of CSSR with XTC showed fairly good agreement with expected ratios.

CONCLUSIONS

Hyperpolarized (129)Xe human imaging and spectroscopy are very promising methods to provide functional information about the lung.

Cardiac involvement and treatment-related mortality after non-myeloablative haemopoietic stem-cell transplantation with unselected autologous peripheral blood for patients with systemic sclerosis: a retrospective analysis

BACKGROUND

Autologous haemopoietic stem-cell transplantation (HSCT) benefits patients with systemic sclerosis but has been associated with significant treatment-related mortality and failure to improve diffusion capacity of carbon monoxide (DLCO). We aimed to assess efficacy of HSCT and use of rigorous cardiac screening in this group.

METHODS

We assessed patients with diffuse systemic sclerosis or limited systemic sclerosis and interstitial lung disease who were treated with HSCT as part of a study or on a compassionate basis at Northwestern University (Chicago, IL, USA) or the University of São Paulo (Ribeirão Preto, Brazil). Unselected peripheral blood stem cells were harvested with cyclophosphamide (2 g/m(2)) and filgrastim. The transplant regimen was a non-myeloablative regimen of cyclophosphamide (200 mg/kg) and rabbit anti-thymocyte globulin (rATG; 4·5-6·5 mg/kg). We followed patients up to 5 years for overall survival, relapse-free survival, modified Rodnan skin score, and pulmonary function tests.

FINDINGS

Five (6%) of 90 patients died from treatment-related causes. Despite standard guidelines that recommend echocardiogram for screening before transplantation, four treatment-related deaths occurred because of cardiovascular complications (one constrictive pericarditis, two right heart failures without underlying infection, and one heart failure during mobilisation), and one death was secondary to sepsis without documented underlying heart disease. Kaplan-Meier analysis showed survival was 78% at 5 years (after eight relapse-related deaths) and relapse-free survival was 70% at 5 years. Compared with baseline, we noted improvements after HSCT in modified Rodnan skin scores at 1 year (58 patients; p<0·0001), 2 years (42 patients; p<0·0001), and 3 years (27 patients; p<0·0001) and forced vital capacity at 1 year (58 patients; p=0·009), 2 years (40 patients; p=0·02), and 3 years (28 patients; p=0·004), but total lung capacity and DLCO were not improved significantly after HSCT. Overall mean DLCO was significantly improved in patients with normal baseline echocardiograms (p=0·005) or electrocardiographs (p=0·05).

INTERPRETATION

Autologous HSCT with a non-myeloablative regimen of cyclophosphamide and rATG with a non-selected autograft results in sustained improvement in skin thickness and forced vital capacity. DLCO is affected by baseline cardiac function. Guidelines for cardiac screening of patients with systemic sclerosis to assess treatment-related risk from pulmonary artery hypertension, primary cardiac involvement, or pericardial disease should be reconsidered and updated.

FUNDING

None.

Loss of CO from the intravascular bed and its impact on the optimised CO-rebreathing method

Total haemoglobin mass can be easily measured by applying the optimised CO-rebreathing method (oCOR-method). Prerequisite for its accurate determination is a homogenous CO distribution in the blood and the exact knowledge of the CO volume circulating in the vascular space. The aim of the study was to evaluate the mixing time of CO in the blood after inhaling a CO-bolus and to quantify the CO volume leaving the vascular bed due to diffusion to myoglobin and due to exhalation during processing the oCOR-method. The oCOR-method was also compared to a former commonly used CO-rebreathing procedure. In ten subjects, the time course of carboxy-haemoglobin (HbCO) formation was analysed simultaneously in capillary and venous blood for a period of 15 min after inhaling a CO bolus. The volume of CO diffusing from haemoglobin to myoglobin was calculated via the decrease of HbCO. As part of this decrease is due to CO exhalation, this volume was quantified by collecting the exhaled air in a Douglas bag system. Equal HbCO values in capillary and venous blood were reached at min 6 indicating complete mixing of CO. The loss of CO out of the vascular bed due to exhalation and due to diffusion to myoglobin was 0.32 +/- 0.12% min(-1) (0.25 +/- 0.09 ml min(-1)) and 0.32 +/- 0.18% min(-1) (0.24 +/- 0.13 ml min(-1)) of the administered CO volume, respectively. The loss of CO due to exhalation and diffusion to myoglobin is of minor impact. It should, however, be considered by using correction factors to obtain high accuracy when determining total haemoglobin mass.

Morphometric model for pulmonary diffusing capacity. I. Membrane diffusing capacity

The pulmonary diffusing capacity is related to the quantitative design characteristics of the pulmonary gas exchanger. The current model for estimating DLO2 from morphometric data breaks the diffusion path for O2 into four steps, three of which represent the membrane part of DLO2. A critique of this model on the basis of newer evidence leads to a modification of the model where the path from the alveolar surface to the erythrocyte membrane is considered as a single step. The structural determinant of this model for DMO2 is the ratio of effective diffusion surface to effective total barrier thickness. The effective surface is formulated as a fraction of the alveolar surface area, the most robust measure of lung design, whereas the effective barrier thickness is the harmonic mean distance--or mean proximity--between alveolar surface and erythrocyte surface. The methods for obtaining the morphometric measurements are discussed. The results show that the new morphometric estimates of DMO2 are 33% lower than those obtained with the old model, resulting in a reduction of the estimates of DLO2 by 10-20%.

How common is sleep-disordered breathing in patients with idiopathic pulmonary fibrosis?

BACKGROUND AND AIM

The frequency of obstructive sleep apnea-hypopnea syndrome (OSAHS) in patients with idiopathic pulmonary fibrosis (IPF) remains controversial. The aim of this study was to assess the frequency of OSAHS in newly diagnosed IPF patients and to identify possible correlations with body mass index and pulmonary function testing parameters.

MATERIALS AND METHODS

Thirty-four newly diagnosed IPF patients were included. All subjects underwent attended overnight PSG. None of the included subjects was under any of the currently available IPF treatments or nocturnal supplemental oxygen therapy.

RESULTS

Total apnea-hypopnea index (AHI) was <5, 5-15, and ≥ 15/h of sleep in 14 (41%), 15 (44%), and five patients (15%), respectively. REM AHI was statistically significant correlated with TLC [Total lung capacity] (p=0.03, r= -0.38). Diffusing capacity of the lung for carbon monoxide was correlated with mean oxygen saturation during sleep (p=0.02, r=0.39).

CONCLUSIONS

Sleep-disordered breathing seems frequent, although remains usually under diagnosed in IPF patients. A decrease in TLC, reflecting the severity of pulmonary restriction, might predispose IPF patients in SDB, especially during the vulnerable REM sleep period.