A B S T R A C T To investigate the mechanisms which enable the diaphragm to preserve ventilation when the work of breathing is elevated, we measured diaphragmatic blood flow (0 di) and oxygen consumption (Vo2 di) in lightly anesthetized dogs. The animals were studied when they breathed quietly, when they inhaled 5% CO2 in 21% or 14% 02, or when they inhaled these gas mixtures through moderate to severe inspiratory resistances. Q di was determined from the integrated diaphragmatic arteriovenous difference of krypton-85, by the Kety-Schmidt technique. V02 di was calculated as the product of Q di and the diaphragmatic arteriovenous oxygen difference ([A-Vy02 di). Alteration in these parameters consequent to augmentation of ventilatory effort were compared with concomitant alterations in diaphragmatic electrical activity (EMG di) and an inspiratory pleural pressure-time index (PPTI).Addition of inspiratory resistances combined with inhalation of CO2 usually increased Q di and consistently increased V02 di, EMG di, and PPTI, the maximum increases being approximately 400-1,600% above control levels. In individual animals, as inspiratory resistance was increased, V0o, di, EMG di, and PPTI rose in direct proportion to each other.In the group as a whole, during resistance breathing the oxygen requirements of the diaphragm were met by a combination of increased [A-Vy02 di and Q di. Unlike other skeletal muscles, oxygen extraction tended to plateau at peak loads, whereas blood flow continued to rise as PPTI and Vo2 di increased. We conclude that augmentation of perfusion permits the diaphragm to sustain high levels of contractile effort when the work of breathing is increased.

Objective. To reduce the radiation dose, reduced time CT perfusion (CTp) acquisitions are tested to measure permeability surface (PS) with a deconvolution method. Methods and Materials. PS was calculated with repeated measurements (n = 305) while truncating the time density curve (TDC) at different time values in 14 CTp studies using CTp 4D software (GE Healthcare, Milwaukee, WI, US). The median acquisition time of CTp studies was 59.35 sec (range 49–92 seconds). To verify the accuracy of the deconvolution algorithm, a variation of the truncated PS within the error measurements was searched, that is, within 3 standard deviations from the mean nominal error provided by the software. The test was also performed for all the remaining CTp parameters measured. Results. PS maximum variability happened within 25 seconds. The PS became constant after 40 seconds for the majority of the active tumors (10/11), while for necrotic tissues it was consistent within 1% after 50 seconds. A consistent result lasted for all the observed CTp parameters, as expected from their analytical dependance. Conclusion. 40-second acquisition time could be an optimal compromise to obtain an accurate measurement of the PS and a reasonable dose exposure with a deconvolution method.

Background: The diagnostic algorithm for idiopathic pulmonary fibrosis (IPF) guidelines has some shortcomings. The aim of the present study was to develop a novel software, "IPFdatabase", that could readily apply the diagnostic criteria per IPF guidelines and make a 'virtual' diagnosis of IPF. Methods: Software was developed as a step-by-step compilation of necessary information according to guidelines to enable a diagnosis of IPF. Software accuracy was validated primarily by comparing software diagnoses to those previously made at a Center for Interstitial Lung Diseases. Results: Clinical validation on 98 patients (68 male, age 61.0 ± 8.5 years), revealed high software accuracy for IPF diagnosis when compared to historical diagnoses (sensitivity 95.5%, specificity 96.2%; positive predictive value 95.5%, negative predictive value 96.2%). A general radiologist and a general pathologist reviewed relevant data with and without the new software: interobserver agreement increased when they used the IPFdatabase (kappa 0.18 to 0.64 for radiology, 0.13 to 0.59 for pathology). Conclusion: IPFdatabase is a useful diagnostic tool for typical cases of IPF, and potentially restricts the need for MDDs to atypical and complex cases. We propose this web-designed software for instant accurate diagnosis of IPF by virtual means and for educational purposes; the software is readily accessed with mobile apps, allows incorporation of updated version of guidelines, can be utilized for gathering data useful for future studies and give physicians rapid feedback in daily practice.

Pulmonary hypertension (PH) is defined as an elevated mean pulmonary artery pressure at rest (mPAP ≥ 25 mmHg), evaluated by right heart catheterization (RHC). The aim of the present study was to evaluate HRCT findings in relation to transthoracic echocardiographic data to better characterize PH in IPF patients and to identify a non-invasive composite index with high predictive value for PH in these patients. 37 IPF patients were enrolled in this retrospective study. All patients underwent a complete assessment for PH, including transthoracic Doppler echocardiography, HRCT scan and right heart catheterization. Right heart catheterization was done in 19 patients (51.3%) as pre-lung transplant assessment and in 18 patients (48.6%) to confirm PH, suspected on the basis of echocardiography. Twenty out of 37 patients (54%) were confirmed to have PH by RHC. Multivariate regression showed that the combination of sPAP, PA area measured by HRCT and the ratio of the diameter of the segmental artery to that of the adjacent bronchus in the apicoposterior segment of the left upper lobe was strongly correlated with mPAP (R2 = 0.53; p = 0.0009). The ROC analysis showed that 931.6 was the ULN for PA area, with 86% sensitivity and 61% specificity (0.839 AUC); 20.34 was the ULN for the ratio of PA area to ascending aorta diameter, with 100% sensitivity and 50% specificity (0.804 AUC). The composite index proposed in the present study could help early detection of IPF patients suspected of PH requiring confirmation by RHC (if deemed clinically necessary).

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