Comparing online and face-to-face administration of a neuropsychological computerized attention test: Assessment modality does not influence performance

Background

The cognitive impairment associated with the COVID-19 pandemic highlighted the need for teleneuropsychology (1). Moreover, neurologic diseases associated with mental deterioration usually require the use of the same neuropsychological instrument to assess cognitive changes across time. Therefore, in such cases, a learning effect upon retesting is not desired. Attention and its subdomains can be measured using Go/no-go tests, such as, the Continuous Visual Attention Test (CVAT). Here, we administered the CVAT to investigate the effect of modality (online vs. face-to-face) on attentional performance. The variables of the CVAT measures four attention domains: focused-attention, behavioral-inhibition, intrinsic-alertness (reaction time, RT), and sustained-attention (intra-individual variability of RTs, VRT).

Methods

The CVAT was applied face-to face and online in 130 adult Americans and 50 adult Brazilians. Three different study designs were used: (1) Between-subjects design: healthy Americans were tested face-to-face (n = 88) or online (n = 42). We verified if there were any differences between the two modalities. (2) Within-subjects design: Brazilians participants (n = 50) were tested twice (online and face-to-face). For each CVAT variable, repeated measures ANCOVAs were performed to verify whether modality or first vs. second tests differ. Agreement was analyzed using Kappa, intraclass correlation coefficients, and Bland-Altman plots. (3) Paired comparisons: we compared Americans vs. Brazilians, pairing subjects by age, sex, and level of education, grouping by modality.

Results

Assessment modality did not influence performance using two independent samples (between-subjects design) or the same individual tested twice (within-subjects design). The second test and the first test did not differ. Data indicated significant agreements for the VRT variable. Based on paired samples, Americans did not differ from Brazilians and a significant agreement was found for the VRT variable.

Conclusion

The CVAT can be administered online or face-to-face without learning upon retesting. The data on agreement (online vs. face-to-face, test vs. retest, Americans vs. Brazilians) indicate that VRT is the most reliable variable.

Limitations

High educational level of the participants and absence of a perfect balanced within-subjects design.

Outcomes of dexmedetomidine as adjuvant drug in patients undergoing videolaparoscopic cholecystectomy: A randomized and prospective clinical trial

OBJECTIVE

The repercussions of ischemia-reperfusion and inflammatory response to surgical injury may compromise the return of physiologic processes in video-laparoscopic surgeries. Dexmedetomidine, as an adjuvant drug in general anesthesia, alters the neuroinflammatory reaction, provides better clinical outcomes in the perioperative period, and may reduce the excessive use of chronic medication in patients with a history of addiction. This study evaluated the immunomodulatory potential of dexmedetomidine on perioperative organ function in video-laparoscopic cholecystectomy patients.

METHODS

There were two groups: Sevoflurane and Dexmedetomidine A (26 patients) vs. Sevoflurane and Saline 0.9% B (26 patients). Three blood samples were collected three times: 1) before surgery, 2) 4-6h after surgery, and 3) 24h postoperatively. Inflammatory and endocrine mediators were protocolized for analysis. Finally, hemodynamic outcomes, quality upon awakening, pain, postoperative nausea and vomiting, and opioid use were compared between groups.

RESULTS

We have demonstrated a reduction of Interleukin 6 six hours after surgery in group A: 34.10 (IQR 13.88-56.15) vs. 65.79 (IQR 23.13-104.97; p = 0.0425) in group B. Systolic blood pressure, diastolic blood pressure, and mean arterial pressure was attenuated in group A in their measurement intervals (p < 0.0001). There was a lower incidence of pain and opioid consumption in the first postoperative hour favoring this group (p < 0.0001). We noticed better quality upon awakening after the intervention when comparing the values of peripheral oxygen saturation and respiratory rate.

CONCLUSIONS

Dexmedetomidine provided anti-inflammatory benefits and contributed to postoperative analgesia without the depressive side effects on the respiratory and cardiovascular systems commonly observed with opioids.

TRIAL REGISTRATION

Immunomodulatory Effect of Dexmedetomidine as an Adjuvant Drug in Laparoscopic Cholecystectomies, NCT05489900, Registered 5 August 2022-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT05489900?term=NCT05489900&draw=2&rank=1.

The clinical impact of the systolic volume variation guided intraoperative fluid administration regimen on surgical outcomes after pancreaticoduodenectomy: a retrospective cohort study

BACKGROUND

Pancreaticoduodenectomy is associated with high morbidity. Many preoperative variables are risk factors for postoperative complications, but they are primarily non-modifiable. It is not clear whether an intraoperative goal-directed fluid regimen might be associated with fewer postoperative surgical complications compared to current conservative, non-goal-directed fluid practices. We hypothesize that the use of Systolic Volume Variation (SVV)-guided intraoperative fluid administration might be beneficial.

METHODS

Data from 223 patients who underwent pancreaticoduodenectomy in our institution between 2015 and 2019 were reviewed. Patients were classified into two groups based on the use of intraoperative use of SVV to guide the administration of fluids. The decision to use SVV or not was made by the attending anesthesiologist. Subjects were classified into SVV-guided intraoperative fluid therapy (SVV group) and non-SVV-guided intraoperative fluid therapy (non-SVV group). Uni and multivariate regression analyses were conducted to determine if SVV-guided fluid therapy was significantly associated with a lower incidence of postoperative surgical complications, such as Postoperative Pancreatic Fistula (POPF), Delayed Gastric Emptying (DGE), among others, after adjusting for confounders.

RESULTS

Baseline, demographic, and intraoperative characteristics were similar between SVV and non-SVV groups. In the multivariate analysis, the use of SVV guidance was significantly associated with fewer postoperative surgical complications (OR = 0.48; 95% CI 0.25-0.91; p = 0.025), even after adjusting for significant covariates, such as perioperative use of epidural, pancreatic gland parenchyma texture, and diameter of the pancreatic duct.

CONCLUSIONS

VV-guided intraoperative fluid administration might be associated with fewer postoperative surgical complications after pancreaticoduodenectomy.

The clinical impact of the perioperative epidural anesthesia on surgical outcomes after pancreaticoduodenectomy: A retrospective cohort study

Background

Pancreaticoduodenectomy is a highly invasive procedure associated with high morbidity. Several preoperative variables are associated with postoperative complications. The role of perioperative factors is uncertain. The use of perioperative epidural analgesia is potentially associated with fewer postoperative surgical complications. We hypothesize that perioperative epidural analgesia might be associated with fewer surgical complications.

Methods

We reviewed data from 288 cases performed at our institution between 2012 and 2019, classifying patients into 2 groups: perioperative use of epidural analgesia and non-perioperative use of epidural analgesia. The decision to use epidural as an adjunct to general anesthesia was based on the judgment of the attending anesthesiologist. Uni- and multivariate analyses were then performed to determine factors associated with postoperative surgical complications, ie, postoperative pancreatic fistula, delayed gastric emptying, among others, after adjusting for confounders.

Results

Baseline and intraoperative factors were similar between the groups, except for sex and postoperative surgical complications. In the univariate analyses, factors associated with fewer postoperative surgical complications were the diameter of the pancreatic duct ≥ 6 mm, hard pancreatic gland parenchyma texture, younger age (< 65 years), and perioperative use of epidural analgesia. In the multivariate analyses, perioperative use of epidural analgesia was significantly associated with fewer postoperative surgical complications (odds ratio = 0.31; 95% confidence interval: 0.13–0.75; P = .009), even after adjusting for significant covariates.

Conclusion

Perioperative use of epidural analgesia might be associated with fewer postoperative surgical complications after pancreaticoduodenectomy even after adjusting for pancreatic gland parenchyma texture, pancreatic duct size, and age.

Incidence of Postoperative Cognitive Dysfunction Following Inhalational vs Total Intravenous General Anesthesia: A Systematic Review and Meta-Analysis

Postoperative cognitive dysfunction (POCD) has been increasingly recognized as a contributor to postoperative complications. A consensus-working group recommended that POCD should be distinguished between delayed cognitive recovery, ie, evaluations up to 30 days postoperative, and neurocognitive disorder, ie, assessments performed between 30 days and 12 months after surgery. Additionally, the choice of the anesthetic, either inhalational or total intravenous anesthesia (TIVA) and its effect on the incidence of POCD, has become a focus of research. Our primary objective was to search the literature and conduct a meta-analysis to verify whether the choice of general anesthesia may impact the incidence of POCD in the first 30 days postoperatively. As a secondary objective, a systematic review of the literature was conducted to estimate the effects of the anesthetic on POCD between 30 days and 12 months postoperative. For the primary objective, an initial review of 1913 articles yielded ten studies with a total of 3390 individuals. For the secondary objective, four studies with a total of 480 patients were selected. In the first 30 days postoperative, the odds-ratio for POCD in TIVA group was 0.46 (95% CI = 0.26-0.81; p = 0.01), compared to the inhalational group. TIVA was associated with a lower incidence of POCD in the first 30 days postoperatively. Regarding the secondary objective, due to the small number of selected articles and its high heterogeneity, a metanalysis was not conducted. Given the heterogeneity of criteria for POCD, future prospective studies with more robust designs should be performed to fully address this question.

Ductal Dilatation of ≥5 mm in Intraductal Papillary Mucinous Neoplasm Should Trigger the Consideration for Pancreatectomy: A Meta-Analysis and Systematic Review of Resected Cases

Simple Summary

Intraductal papillary mucinous neoplasms (IPMN) are common but difficult to manage since accurate tools for diagnosing malignancy are unavailable. This study evaluates the diagnostic value of main pancreatic duct (MPD) diameter for detecting IPMN malignancy, using a meta-analysis of published data. The result suggests that malignancy is highly prevalent in IPMN with ductal dilatation of >5 mm.

Abstract

Intraductal papillary mucinous neoplasms (IPMN) are common but difficult to manage since accurate tools for diagnosing malignancy are unavailable. This study tests the diagnostic value of the main pancreatic duct (MPD) diameter for detecting IPMN malignancy using a meta-analysis of published data of resected IPMNs. Collected from a comprehensive literature search, the articles included in this analysis must report malignancy cases (high-grade dysplasia (HGD) and invasive carcinoma (IC)) and MPD diameter so that two MPD cut-offs could be created. The sensitivity, specificity, and odds ratios of the two cutoffs for predicting malignancy were calculated. A review of 1493 articles yielded 20 retrospective studies with 3982 resected cases. A cutoff of ≥5 mm is more sensitive than the ≥10 mm cutoff and has pooled sensitivity of 72.20% and 75.60% for classification of HGD and IC, respectively. Both MPD cutoffs of ≥5 mm and ≥10 mm were associated with malignancy (OR = 4.36 (95% CI: 2.82, 6.75) vs. OR = 3.18 (95% CI: 2.25, 4.49), respectively). The odds of HGD and IC for patients with MPD ≥5 mm were 5.66 (95% CI: 3.02, 10.62) and 7.40 (95% CI: 4.95, 11.06), respectively. OR of HGD and IC for MPD ≥10 mm cutoff were 4.36 (95% CI: 3.20, 5.93) and 4.75 (95% CI: 2.39, 9.45), respectively. IPMN with MPD of >5 mm could very likely be malignant. In selected IPMN patients, pancreatectomy should be considered when MPD is >5 mm.

Multifocal/diffuse pancreatic serous cystic neoplasms: Systematic review with a new case

BACKGROUND/OBJECTIVES

Pancreatic cystic neoplasms (PCNs) are common, among which 13%-23% are serous cystic neoplasms (SCNs). However, diffuse and multifocal variants of SCNs are extremely rare. The differential diagnosis of SCNs from other PCNs is important as the former entities are benign and do not become invasive.

OBJECTIVE

This study analyzes the clinical characteristics of multifocal/diffuse SCN through a systematic review of the literature and a case report.

METHODS

A comprehensive literature search was executed in the Ovid MEDLINE, Embase, and Google Scholar databases. The search strategy was designed to capture the concept of multifocal/diffuse SCN cases with sufficient clinical information for detailed analysis. Using the final included articles, we analyzed tumor characteristics, diagnostic modalities used, initial management and indications, and patient outcomes.

RESULTS

A review of 262 articles yielded 19 publications with 22 cases that had detailed clinical information. We presented an additional case from our institution database. The systematic review of 23 cases revealed that the diffuse variant is more common than the multifocal variant (15 vs 8 cases, respectively). Patients were managed with surgical intervention, conservative treatment, or conservative treatment followed by surgical intervention. Indications for surgery following conservative management mainly included new onset or worsening of symptoms. Only one case reported significant tumor growth after attempting an observational approach. No articles reported recurrence of SCN after pancreatectomy, and no articles reported mortality related to multifocal/diffuse SCNs.

CONCLUSION

Despite their expansive-growing and space-occupying characteristics, multifocal/diffuse SCNs should be treated similarly to their more common unifocal counterpart.

Cancer During Pregnancy: The Oncologist Overview

Although a rare and challenging condition, cancer during pregnancy should promptly be identified and treated. Not only standards of care guidelines for the underlying disease are taken into account, but also fetal safety might be weighted for clinical decisions. Frequent lack of experience and knowledge about this condition could lead to late diagnosis, imprecise management, suboptimal treatment and fetal and maternal harm. Therefore, this review aims to summarize the current evidence regarding the epidemiology, clinical presentation, diagnostic workup, staging and treatment, including novel treatment modalities for patients diagnosed with cancer during pregnancy.

Pleural function and lymphatics

The pleural space plays an important role in respiratory function as the negative intrapleural pressure regimen ensures lung expansion and in the mean time maintains the tight mechanical coupling between the lung and the chest wall. The efficiency of the lung-chest wall coupling depends upon pleural liquid volume, which in turn reflects the balance between the filtration of fluid into and its egress out of the cavity. While filtration occurs through a single mechanism passively driving fluid from the interstitium of the parietal pleura into the cavity, several mechanisms may co-operate to remove pleural fluid. Among these, the pleural lymphatic system emerges as the most important one in quantitative terms and the only one able to cope with variable pleural fluid volume and drainage requirements. In this review, we present a detailed account of the actual knowledge on: (a) the complex morphology of the pleural lymphatic system, (b) the mechanism supporting pleural lymph formation and propulsion, (c) the dependence of pleural lymphatic function upon local tissue mechanics and (d) the effect of lymphatic inefficiency in the development of clinically severe pleural and, more in general, respiratory pathologies.

Impact of respiratory pattern on lung mechanics and interstitial proteoglycans in spontaneously breathing anaesthetized healthy rats

AIM

The aim of this study was to investigate the effect of different pattern of spontaneous breathing on the respiratory mechanics and on the integrity of the pulmonary extracellular matrix.

METHODS

Experiments were performed on adult healthy rats in which different spontaneously breathing pattern was elicited through administration of two commonly used anaesthetic mixtures: pentobarbital/urethane (P/U) and ketamine/medetomidine (K/M). The animals (five per group) were randomized and left to spontaneously breath for 10 min (P/U-sham; K/M-sham) or for 4h (P/U-4h; K/M-4h), targeting the anaesthesia level to obtain a tidal volume of about 8 mL kg(-1) body wt. At the end of the experiment, lung matrix integrity was assessed through determination of the glycosaminoglycans (GAGs) content in the lung parenchyma.

RESULTS

Compared with K/M, anaesthesia with P/U cocktail induced: (1) a higher respiratory rate and minute ventilation attained with lower P(a) CO(2) ; (2) a higher pressure-time-product and work of breathing per minute; (3) a lower static lung compliance; (4) an increased activation of lung tissue metalloproteases; and (5) greater extraction of pulmonary interstitial GAGs.

CONCLUSIONS

This study suggests that the breathing pattern induced by the different anaesthetic regimen may damage the pulmonary interstitium even during spontaneous breathing at physiological tidal volumes.

International Programme for Resource Use in Critical Care (IPOC)--a methodology and initial results of cost and provision in four European countries

BACKGROUND

A standardized top-down costing method is not currently available internationally. An internally validated method developed in the UK was modified for use in critical care in different countries. Costs could then be compared using the World Health Organization's Purchasing Power Parities (WHO PPPs).

METHODS

This was an observational, retrospective, cross-sectional, multicentre study set in four European countries: France, UK, Germany and Hungary. A total of 329 adult intensive care units (ICUs) participated in the study.

RESULTS

The costs are reported in international dollars ($) derived from the WHO PPP programme. The results show significant differences in resource use and costs of ICUs over the four countries. On the basis of the sum of the means for the major components, the average cost per patient day in UK hospitals was $1512, in French hospitals $934, in German hospitals $726 and in Hungarian hospitals $280.

CONCLUSIONS

The reasons for such differences are poorly understood but warrant further investigation. This information will allow us to better adjust our measures of international ICU costs.

The cost of a hospital ward in Europe: is there a methodology available to accurately measure the costs?

Costing health care services has become a major requirement due to an increase in demand for health care and technological advances. Several studies have been published describing the computation of the costs of hospital wards. The objective of this article is to examine the methodologies utilised to try to describe the basic components of a standardised method, which could be applied throughout Europe. Cost measurement however is a complex matter and a lack of clarity exists in the terminology and the cost concepts utilised. The methods discussed in this review make it evident that there is a lack of standardized methodologies for the determination of accurate costs of hospital wards. A standardized costing methodology would facilitate comparisons, encourage economic evaluation within the ward and hence assist in the decision-making process with regard to the efficient allocation of resources.

Pulmonary microvascular and perivascular interstitial geometry during development of mild hydraulic edema

To study pulmonary arteriolar vasomotion in control conditions and in the transition to hydraulic edema, changes in subpleural pulmonary arteriolar diameter and perivascular interstitial volume were evaluated in anesthetized spontaneously breathing rabbits. Images of subpleural pulmonary microvessels were recorded in control conditions and for up to 180 min during a 0.5 ml x kg(-1) x min(-1) intravenous saline infusion through an intact parietal pleural window. Images were digitized and analyzed with a semiautomatic procedure to determine vessel diameter and perivascular interstitial thickness from which interstitial fluid volume was derived. In control vessels, the diameter of approximately 30-, approximately 50-, and approximately 80-microm arterioles and the perivascular interstitial thickness were fairly stable. During infusion, the diameter increased maximally by 20% in approximately 30 microm vessels, was unchanged in approximately 50 microm vessels, and decreased by 25% in approximately 80-microm arterioles; the perivascular interstitial volume increased by 54% only around 30-microm microvessels. In papaverine-treated rabbits, all arterioles dilated and a larger increase in perivascular interstitial thickness was observed. The data suggest that the opposite vasomotor behavior of 30- and 80-microm arterioles during development of mild edema may represent a local specific response of the pulmonary microcirculation to reduce capillary pressure in the face of an increased transendothelial fluid filtration, thus counteracting progression toward severe edema.

Pulmonary interstitial pressure and tissue matrix structure in acute hypoxia

Pulmonary interstitial pressure was measured via micropuncture in anesthetized rabbits in normoxia and after breathing 12% O(2). In normoxia [arterial PO(2) = 88 +/- 2 (SD) mmHg], pulmonary arterial pressure and pulmonary interstitial pressure were 16 +/- 8 and -9.6 +/- 2 cmH(2)O, respectively. After 6 h of hypoxia (arterial PO(2) = 39 +/- 16 mm Hg), the corresponding values were 30+/-8 and 3.5+/-2.5 cm H(2)O (P<0.05). Pulmonary interstitial proteoglycan extractability, evaluated by hexuronate assay after 0.4 M guanidinium hydrochloride extraction, was 12.3, 32.4, and 60.6 microg/g wet tissue in normoxia and after 3 and 6 h of hypoxia, respectively, indicating a weakening of the noncovalent bonds linking proteoglycans to other extracellular matrix components. Gel filtration chromatography showed an increased fragmentation of chondroitin sulfate- and heparan sulfate-proteoglycans during hypoxic exposure, accounting for a loss of extracellular matrix native architecture and basement membrane structure. Gelatin zymography demonstrated increased amounts of the proteolytically activated form of gelatinase B (matrix metalloproteinase-9) after hypoxic exposure, providing evidence that the activation of proteinases may play a role in hypoxia-induced lung injury.

Isolation of pulmonary interstitial fluid in rabbits by a modified wick technique

Interstitial fluid protein concentration (C(protein)) values in perivascular and peribronchial lung tissues were never simultaneously measured in mammals; in this study, perivascular and peribronchial interstitial fluids were collected from rabbits under control conditions and rabbits with hydraulic edema or lesional edema. Postmortem dry wicks were implanted in the perivascular and peribronchial tissues; after 20 min, the wicks were withdrawn and the interstitial fluid was collected to measure C(protein) and colloid osmotic pressure. Plasma, perivascular, and peribronchial C(protein) values averaged 6.4 +/- 0.7 (SD), 3.7 +/- 0.5, and 2.4 +/- 0.7 g/dl, respectively, in control rabbits; 4.8 +/- 0.7, 2.5 +/- 0.6, and 2.4 +/- 0.4 g/dl, respectively, in rabbits with hydraulic edema; and 5.1 +/- 0.3, 4.3 +/- 0.4 and 3.3 +/- 0.6 g/dl, respectively, in rabbits with lesional edema. Contamination of plasma proteins from microvascular lesions during wick insertion was 14% of plasma C(protein). In control animals, pulmonary interstitial C(protein) was lower than previous estimates from pre- and postnodal pulmonary lymph; furthermore, although the interstitium constitutes a continuum within the lung parenchyma, regional differences in tissue content seem to exist in the rabbit lung.

Development of lung edema: interstitial fluid dynamics and molecular structure

Pulmonary interstitium is maintained dehydrated at subatmospheric pressure (-10 cmH(2)O) through low capillary permeability, low tissue compliance, and an efficient lymphatic drainage. Enzymatic degradation of proteoglycans disrupts the endothelial basal membrane and the matrix structure, triggering the development of pulmonary edema.

Subatmospheric pressure in the rabbit pleural lymphatic network

1. Hydraulic pressure in intercostal and diaphragmatic lymphatic vessels was measured through the micropuncture technique in 23 anaesthetised paralysed rabbits. Pleural lymphatic vessels with diameters ranging from 55 to 950 microm were observed under stereomicroscope view about 3-4 h after intrapleural injection of 20 % fluorescent dextrans. 2. Lymphatic pressure oscillated from a minimum (Pmin) to a maximum (Pmax) value, reflecting oscillations in phase with cardiac activity (cardiogenic oscillations) and lymphatic myogenic activity. With intact pleural space, Pmin in submesothelial diaphragmatic lymphatic vessels of the lateral apposition zone was -9.1 +/- 4.2 mmHg, more subatmospheric than the simultaneously recorded pleural liquid pressure amounting to -3.9 +/- 1.2 mmHg. In extrapleural intercostal lymphatic vessels Pmin averaged -1.3 +/- 2. 7 mmHg. 3. Cardiogenic pressure oscillations (Pmax - Pmin), were observed in all recordings; their mean amplitude was about 5 mmHg and was not dependent upon frequency of cardiac contraction, nor lymphatic vessel diameter, nor the Pmin value. 4. Intrinsic contractions of lymphatic vessel walls caused spontaneous pressure waves of about 7 mmHg in amplitude at a rate of 8 cycles min-1. 5. These results demonstrated the ability of pleural lymphatic vessels to generate pressure oscillations driving fluid from the subatmospheric pleural space into the lymphatic network.

The sensitivity of versican from rabbit lung to gelatinase A (MMP-2) and B (MMP-9) and its involvement in the development of hydraulic lung edema

Large chondroitinsulphate-containing proteoglycan (versican) isolated from rabbit lung was cleaved by purified gelatinase A (MMP-2) and gelatinase B (MMP-9), as well as by crude enzyme extract from rabbit lung with hydraulic edema. Gelatine zymography, performed after purification of gelatinases by affinity chromatography, demonstrated that the enzyme extract contained two main gelatinolytic bands at about 92 kDa and 72 kDa, identified by specific antisera as the latent proMMP-9 and proMMP-2, respectively. Moreover, enzyme extract from edematous lung showed an increased amount of the proteolytically activated forms of both gelatinases with respect to normal controls. These results suggest that MMP-2 and MMP-9 are involved in the breakdown of versican occurring in rabbit lung during the development of hydraulic edema.

Involvement of lung interstitial proteoglycans in development of hydraulic- and elastase-induced edema

We extracted and isolated proteoglycans from lung tissue samples obtained from three groups of anesthetized rabbits: 1) control animals (C; n = 8) killed by overdose after 180 min; 2) animals receiving an intravenous saline infusion (S; n = 4, 1.5 ml . kg-1 . min-1) for 180 min; 3) animals receiving an intravenous bolus of 200 microg of pancreatic elastase (E; n = 4), killed after 200 min. The lung dry weight-to-wet weight ratio in the three groups was 5.2 +/- 0.2, 6.0 +/- 0.4, and 5.6 +/- 0.5, respectively. Gel-filtration analysis showed a massive fragmentation of the versican family of the extracellular matrix (ECM) in the S groups and a marked degradation of heparan sulfate-containing proteoglycans, including perlecan of the basement membrane, in the E group. The binding properties of total proteoglycans to other ECM components were lowered in both groups relative to control. The decrease in proteoglycan binding was more pronounced for collagen type IV in the E group relative to C (-93.5%, P < 0.05) and for hyaluronic acid in the S groups (-85.8%, P < 0.05). These findings suggest that elastase treatment produces a major degree of damage to the organization of basement membrane, whereas saline loading affects more markedly the architecture of interstitial ECM. Qualitative zymography performed on lung extracts showed increased gelatinase activities in both S and E groups, providing direct evidence that the activation of tissue proteinases may play a role in acute lung injury.

Proteoglycan involvement during development of lesional pulmonary edema

We evaluated the effect of pancreatic elastase (7 IU i.v.) on pulmonary interstitial pressure (Pip) in in situ rabbit lungs by a micropuncture technique through the intact parietal pleura. Pip was -10.8 +/- 2.2 (SD) cmH2O in the control condition, increased to +5.1 +/- 1.7 cmH2O at approximately 60 min [condition referred to as mild edema (ME)], and subsequently decreased to -0.15 +/- 0.8 cmH2O, remaining steady from 80 up to 200 min with a marked increase in lung wet-to-dry weight ratio [condition referred to as severe edema (SE)], suggesting an increase in tissue compliance. We functionally correlated the measured Pip to structural modifications of proteoglycans, the major interfibrillar component of the extracellular matrix (ECM). The strength of the noncovalent bonds linking proteoglycans to other ECM components decreased with increasing severity of edema, as indicated by the increased extractability of proteoglycans with guanidine hydrochloride. Total proteoglycan recovery (expressed as microgram hexuronate/g dry tissue) increased from 436.8 +/- 14 in the control condition to 495.3 +/- 23 and 547.0 +/- 10 in ME and SE, respectively. Gel-filtration chromatography showed in ME a fragmentation of heparan sulfate proteoglycans, suggesting that elastase treatment first affected basement membrane integrity, whereas large chondroitin sulfate proteoglycans were degraded only in SE. Elastase caused a fragmentation only of the core protein of proteoglycans, the binding properties of which to collagens, fibronectin, and hyaluronic acid were markedly decreased, as indicated by a solid-phase binding assay. The sequential degradation of heparan sulfate and chondroitin sulfate proteoglycans may account for the initial increase in microvascular permeability, followed by a loss of the native architecture of the ECM, which may be responsible for the increase in tissue compliance.

Respiratory mechanics after 180 days space mission (EUROMIR'95)

The present study reports data on respiratory function of lung and chest wall following the 180 days long European - Russian EuroMir '95 space mission. Data reported refer to two subjects studied before the mission, on day 9 and 175 in flight and on days 1, 10, 12, 27 and 120 after return. In-flight vital capacity (VC) and expiratory reserve volume (ERV) were similar to those in supine posture, namely approximately 5% and approximately 30% less than in sitting posture. On day 1 after return, VC was reduced by approximately 30% in both postures. This reflected a decrease in ERV (approximately 0.5 L) and in IC (inspiratory capacity, approximately 1.7 L) that could be attributed to a marked weakening of the respiratory muscles. Regain of normal preflight values barely occurred 120 days after return. Post-flight pressure-volume curves of the lung, chest wall and total respiratory system are equal to preflight ones. The pressure-volume curve of the lung in supine posture is displaced to the right relative to sitting posture and shows a lower compliance. As far as the lung in-flight condition resembles that occurring in supine posture, this implies a lower compliance, a greater amount of blood in the pulmonary microvascular bed, a more homogeneous lung perfusion and therefore a greater microvascular filtration rate towards lung interstitium.

Pulmonary interstitial pressure and proteoglycans during development of pulmonary edema

In anesthetized adult rabbits, pulmonary perivascular interstitial pressure (P(ip)), measured by micropuncture technique with intact pleural space, averaged -10.5 +/- 1.9 (SD) cmH2O in control conditions, with a wet-to-dry lung weight ratio (W/D) of 4.8 +/- 0.2. Saline infusion (120 ml i.v. over 120 min) induced interstitial edema, increasing P(ip) to 3.62 +/- 1.6 cmH2O with no significant increase in W/D (5.13 +/- 0.1). For intravenous saline infusion exceeding 140 ml, P(ip) decreased to about atmospheric pressure with development of severe edema that was characterized by an increase of W/D ( > 7) with no further change in P(ip). In a separate set of animals, pulmonary interstitial proteoglycans (PGs) were investigated after sequential extraction of the tissue with 0.4 and 4 M guanidinium chloride (GuHCl) under control conditions and with interstitial (100 ml saline load in 100 min) and severe edema ( > 200 ml total infusion). The extractability of PGs increased constantly with increasing W/D. PG content in total extracts was evaluated by determination of hexuronate content which was 195.4 +/- 1.5 micrograms/g dry tissue in control lungs, 217.9 +/- 1.6 in interstitial edema, and 316.4 +/- 2.7 in severe edema. Moreover, edema development was coupled with an increase in efficiency of PG extraction with 0.4 M GuHCl. These findings suggested a weakening of PG interactions with other components of the extracellular matrix (ECM). Electrophoretic and gel-filtration analyses showed that the relative content of PG populations of large molecular size decreased constantly in 0.4 M GuHCl extract with increasing water loading. We propose relating the inflection of P(ip) in the transition from interstitial to severe edema to PG breakdown, which might greatly affect ECM structural organization, including collagen spreading and/or rupture of epithelial layer.

Pulmonary microvascular pressure profile during development of hydrostatic edema

OBJECTIVE

To measure, in intact closed chest, the pressure in the pulmonary microvasculature during transition to mild interstitial edema.

METHODS

In anesthetized spontaneously breathing rabbits, the pulmonary artery and left atrium were cannulated. Pleural windows were prepared to view the superficial pulmonary microvascular network through the intact parietal pleura. After intravenous infusion of 96.4 +/- 12.3 ml of saline at a rate of 0.5 ml/kg h, the hydraulic pressure in the pulmonary microvessels (15-240 microns in diameter) were measured using glass pipettes driven through the pleural window and connected to a servonull system.

RESULTS

After saline, plasma protein concentration decreased from 6 +/- 1 to 4.8 +/- 0.5 g/dl; pulmonary arterial and left atrial pressures averaged 22.3 +/- 6.4 and 2.3 +/- 2 cm H2O in control and 23.1 +/- 4.2 and 4.2 +/- 2 cm H2O after infusion. After saline loading, 16.4% of total pressure drop occurred from pulmonary artery to 80-microns arterioles, 60.3% in 30-80 microns arterioles, 6.9% from 30-microns arterioles to 30-microns venules and 16.4% in the downstream segment.

CONCLUSIONS

Mild interstitial edema induced, with respect to control, constriction of small arterioles and capillary recruitment to maintain a low capillary pressure. Hence, in initial edema, pulmonary circulation prevents further fluid filtration, acting like an intrinsic safety factor to delay development of severe edema.

Estimation of in vivo pulmonary microvascular and interstitial geometry using digital image analysis

OBJECTIVE

To determine microvascular diameter and perivascular interstitium thickness at the lung surface in the in situ, in vivo lung.

METHODS

Microscopic images of the lung surface collected through a "pleural window" by a videocamera were digitized with a monochrome frame grabber (512 x 512 pixels, 8 bits per pixels) to be computer analyzed by image processing techniques.

RESULTS

We found that the maxima in the distribution of the standard deviations of gray levels in adjacent neighbors 7 x 7 pixels wide identify the edges between the microvessel lumen and the surrounding perivascular interstitium. Furthermore, the maxima in the distribution of the standard deviation of the standard deviations of gray levels identify the edges between the perivascular interstitium and the lung tissue.

CONCLUSIONS

This technique can be applied to microvessels ranging in diameter from 30 microns to 200 microns and perivascular interstitial thickness of the order of 10-150 microns. Our approach allows for the definition of microvascular geometry even for noisy images and represents an improvement compared to other edge detection methods. The proposed analytical procedure may provide a useful tool to study lung fluid balance and microvascular reactivity in the in situ lung in the normal state and in response to a variety of functional conditions.

Contribution of lymphatic myogenic activity and respiratory movements to pleural lymph flow

In 11 anesthetized spontaneously breathing rabbits, we studied the contribution to total pleural lymph flow of myogenic activity of pleural lymphatics ("intrinsic mechanism") and the effect due to mechanical action of respiratory movements ("extrinsic mechanism"). Isoncotic saline solution (5 ml) containing 100 microCi of 125I-lactate dehydrogenase (LDH) was injected into right pleural space; in all but three control rabbits, injectate contained 1 mM amiloride in dimethyl sulfoxide to induce relaxation of smooth muscle tone. At 3 h, rabbits were killed and pleural fluid was collected and its volume measured. LDH radioactivity in pleural liquid and parietal pleural tissue was counted. In control rabbits, net pleural liquid flow (Jnet) at 3 h was -0.17 +/- 0.04 (SD) ml.kg-1.h-1; LDH concentration (C) and quantity (Q) decreased by 40.3 and 51.1% of initial value, respectively; total pleural lymphatic flow (Jl), calculated from LDH clearance, was 0.58 +/- 0.01 ml.kg-1.h-1. In amiloride-treated rabbits, Jnet was 0.01 +/- 0.1 ml.kg-1.h-1, C decreased by 34.4% and Q by 33.1%, and Jl averaged 0.39 +/- 0.02 ml.kg-1.h-1. C in parietal pleura, rich in lymphatics, was 13-fold higher in control than in amiloride-treated animals. The significant decrease of pleural lymphatic flow observed with amiloride (-40% relative to control) resulted from impairment of intrinsic mechanism, whereas, at comparable breathing frequencies, extrinsic mechanism remained unaltered. The direct effect of topical application of 1 mM amiloride was confirmed on exposed mesenteric collecting lymphatic ducts (data from 5 rats): amiloride reduced lymph flow by 40% by decreasing stroke volume without greatly affecting contraction rate of lymphatic walls.

Permeability of parietal pleura to liquid and proteins

The permselectivity of the parietal pleura was determined in spontaneously breathing anesthetized rabbits and dogs. In rabbits, we injected intrapleurally 5 ml of 1-g/dl albumin solution containing 100 microCi of 131I-labeled albumin plus 100 microCi of either lactate dehydrogenase (LDH) or alpha 2-125I-macroglobulin. Dogs received 100 ml of 1-g/dl albumin solution containing 100 microCi of 131I-albumin plus 100 microCi of alpha 2-125I-macroglobulin. A transpleural pressure gradient was set, lowering the intracapsular pressure to -30 cmH2O. The solvent drag reflection coefficients (sigma f) were calculated as the ratio between tracer concentrations in capsular and pleural liquid collected at 60-180 min. In rabbits sigma f was 0.44 +/- 0.2 (SD) for albumin, 0.84 +/- 0.1 for LDH, and 0.93 +/- 0.05 for alpha 2-macroglobulin. In dogs sigma f was 0.30 +/- 0.19 for albumin and 0.53 +/- 0.15 for alpha 2-macroglobulin. The hydraulic conductivity of the parietal pleura was 2.18 +/- 1.54 microliters.h-1.cmH2O-1.cm-2 in rabbits and 1.22 +/- 1.13 microliters.h-1.cmH2O-1.cm-2 in dogs. The parietal pleura could be modeled by two pore populations with radii of 83-89 and 156-222 A. The permeability coefficient averaged 0.08-0.21 x 10(-6) cm/s for albumin, 0.06-0.09 x 10(-6) cm/s for LDH, and 0.01-0.03 x 10(-6) cm/s for alpha 2-macroglobulin.

Model of pleural fluid turnover

A model of pleural fluid turnover, based on mass conservation law, was developed from experimental evidence that 1) pleural fluid filters through the parietal pleura and is drained by parietal lymphatics and 2) lymph flow increases after an increase in pleural liquid volume, attaining a maximum value 10 times greater than control. From the differential equation describing the time evolution of pleural liquid pressure, we obtained the equation for the steady-state condition ("set point") of pleural liquid pressure: Pss = (KfPi*+KlPzf)/Kf+Kl), where Kf is parietal pleura filtration coefficient, Kl is initial lymphatic conductance, Pzf is lymphatic potential absorption pressure, and Pi* is a factor accounting for the protein reflection coefficient of parietal mesothelium and hydraulic and colloid osmotic pressure of parietal interstitium and pleural liquid. Lymphatics act as a passive negative-feedback control tending to offset increases in pleural liquid volume. Some features of this control are summarized here: 1) lymphatics exert a tight control on pleural liquid volume or pressure so that the set point is maintained close to the potential absorption pressure of lymphatics; 2) a 10-fold increase in Kf would cause only a 2- and 5-fold increase in pleural liquid volume with normal (1.8 g/dl) and increased (3.4 g/dl) protein concentration of the pleural fluid, respectively; and 3) the reduction in maximum lymph flow greatly reduces the range of operation of the control with increased filtration and/or protein concentration of pleural fluid.

Fluid exchanges across the parietal peritoneal and pleural mesothelia

In 31 anesthetized rabbits, after removal of superficial tissues, glass micropipettes filled with 0.5 M NaCl solution and connected to an electrohydraulic servo-null system were used to measure extraperitoneal interstitial fluid pressure (Pi,per) and peritoneal liquid pressure (Pliq,per) at various heights. Linear regressions relating pressure to recording height (H) were Pi,per = 1.07 - 0.27H and Pliq,per = 0.9 - 0.64H, respectively. Protein concentration (Cp;g/dl) and colloid osmotic pressure (II; cmH2O) of plasma and of peritoneal and pleural liquids were 5.48 +/- 0.38 and 24.61 +/- 3.23, 3.07 +/- 0.5 and 13.29 +/- 1.87, and 1.76 +/- 0.42 and 8.45 +/- 2, respectively. The equation relating II to Cp was II = 4.64Cp + 0.0027Cp2. Tissue fluid samples were collected with saline-soaked wicks implanted in vivo or dry wicks inserted postmortem in extraperitoneal and extrapleural interstitial spaces. After 60 and 15 min, respectively, wicks were withdrawn and centrifuged; wick fluid was analyzed in colloid osmometer for small samples. Average extraperitoneal and extrapleural II values were 14.2 +/- 2.49 and 11.94 +/- 1.52 cmH2O, corresponding to Cp of 3.07 and 2.57 g/dl, respectively. The average net pressure gradient, assuming reflection coefficient and hydraulic conductivity (Negrini et al. J. Appl. Physiol. 69: 625-630, 1990; 71: 2543-2547, 1991), was 1.18 and 0.98 cmH2O for parietal peritoneal and pleural mesothelia, respectively, favoring filtration from the extraserosal interstitia into the serosal cavities. Total parietal peritoneal filtration was 1.49 ml.kg-1.h-1, approximately 15-fold higher than that for pleural mesothelium.

Pulmonary interstitial pressure in intact in situ lung: transition to interstitial edema

In anesthetized rabbits (n = 25) subject to slow intravenous saline loading (0.4 ml.min-1.kg-1) for 3 h, we measured pulmonary interstitial pressure (Pip) in intact in situ lungs with glass micropipettes inserted directly into the lung parenchyma via a "pleural window." Measurements were done in apneic animals at the end-expiratory volume with O2 delivered in the trachea. Pip was -10 +/- 1.5 (SD) cmH2O in control and increased to 0.6 +/- 3.8 and 5.7 +/- 3.3 cmH2O at 66 and 180 min, respectively. The wet-to-dry weight ratio (W/D) of the lung was 5.04 +/- 0.2 in the control group and 5.34 +/- 0.7 at 180 min (+6%); the corresponding W/D for intercostal muscles were 3.25 +/- 0.03 and 4.19 +/- 0.5 (+28%). Pulmonary interstitial compliance was 0.47 ml.mmHg-1.100 g wet wt-1. Pulmonary arterial and left atrial pressures were 18.4 +/- 2 and 3 +/- 1 cmH2O in control and increased to 19.5 +/- 2.9 and 4.6 +/- 1.7 cmH2O at 180 min, respectively. Aortic flow (cardiac output) increased from 103 +/- 35 to 131 +/- 26 ml/min; pulmonary resistance fell from 0.17 +/- 0.06 to 0.14 +/- 0.05 cmH2O.min.ml-1 (-18%), suggesting that the increase in Pip did not limit blood flow. The pulmonary capillary-to-interstitium filtration pressure gradient decreased sharply from a control value of 10 cmH2O to 0 cmH2O within 60 min because of the increase in Pip and remained unchanged for < or = 180 min. Data suggest that the pulmonary interstitial matrix can withstand fluid pressures above atmospheric, preventing the development of pulmonary alveolar flooding.

Intrapleural fluid movements described by a porous flow model

We injected technetium-labeled albumin (at a concentration similar to that of the pleural fluid) in the costal region of anesthetized dogs (n = 13) either breathing spontaneously or apneic. The decay rate of labeled activity at the injection site was studied with a gamma camera placed either in the anteroposterior (AP) or laterolateral (LL) projection. In breathing animals (respiratory frequency approximately 10 cycles/min), 10 min after the injection the activity decreased by approximately 50% on AP and approximately 20% on LL imaging; in apneic animals the corresponding decrease in activity was reduced to approximately 15 and approximately 3%, respectively. We considered label translocation from AP and LL imaging as a result of bulk flows of liquid along the costomediastinal and gravity-dependent direction, respectively. We related intrapleural flows to the hydraulic pressure gradients existing along these two directions and to the geometry of the pleural space. The pleural space was considered as a porous medium partially occupied by the mesh of microvilli protruding from mesothelial cells. Solution of the Kozeny-Carman equation for the observed flow velocities and pressure gradients yielded a mean hydraulic radius of the pathways followed by the liquid ranging from 2 to 4 microns. The hydraulic resistivity of the pleural space was estimated at approximately 8.5 x 10(5) dyn.s.cm-4, five orders of magnitude lower than that of interstitial tissue.

Distribution of diaphragmatic lymphatic lacunae

The morphology of the submesothelial lymphatic lacunae on the pleural and peritoneal surface over the tendinous and muscular portion of the diaphragm was studied in 10 anesthetized rabbits. The lymphatic network was evidenced by injecting 1 ml of colloidal carbon solution in the pleural (n = 5) or the peritoneal (n = 5) space. After 1 h of spontaneous breathing, the animal was killed and the diaphragm was fixed in situ by injection of approximately 5 ml of fixative in pleural and peritoneal spaces. Then both cavities were opened and the diaphragm was excised and pinned to a support. According to which cavity had received the injection, the peritoneal or the pleural side of the diaphragm was scanned by sequential imaging of the whole surface by use of a video camera connected to a stereomicroscope and to a video monitor. The anatomic design appeared as a network of lacunae running either parallel or perpendicular to the major axis of the tendinous or muscular fibers. The lacunae were more densely distributed on the tendinous peritoneal area than on the pleural one. Scanty lacunae were seen on the muscular regions of both diaphragmatic sides, characterized by large areas without lacunae. The average density of lacunae on tendinous and muscular regions was 6 and 1.7/cm2 for the pleural side and 25 and 3.4/cm2 for the peritoneal side, respectively. The average width of lacunae was 137.9 +/- 1.6 and 108.8 +/- 1.7 microns on the tendinous pleural and the peritoneal side, respectively, and 163 +/- 1.8 microns on the muscular portion of the pleural and peritoneal surfaces.

Microvascular pressure profile in intact in situ lung

We measured the microvascular pressure profile in lungs physiologically expanded in the pleural space at functional residual capacity. In 29 anesthetized rabbits a caudal intercostal space was cleared of its external and internal muscles. A small area of endothoracic fascia was surgically thinned, exposing the parietal pleura through which pulmonary vessels were clearly detectable under stereomicroscopic view. Pulmonary microvascular pressure was measured with glass micropipettes connected to a servo-null system. During the pressure measurements the animal was kept apneic and 50% humidified oxygen was delivered in the trachea. Pulmonary arterial and left atrial pressures were 22.3 +/- 1.5 and 1.6 +/- 1.5 (SD) cmH2O, respectively. The segmental pulmonary vascular pressure drop expressed as a percentage of the pulmonary arterial to left atrial pressure was approximately 33% from pulmonary artery to approximately 130-microns-diam arterioles, 4.5% from approximately 130- to approximately 60-microns-diam arterioles, approximately 46% from approximately 60-microns-diam arterioles to approximately 30-microns-diam venules, approximately 9.5% from 30- to 150-microns-diam venules, and approximately 7% for the remaining venous segment. Pulmonary capillary pressure was estimated at approximately 9 cmH2O.

Permeability-surface area product and reflection coefficient of the parietal pleura in dogs

The parameters describing the permeability of the parietal pleura to liquid and total plasma proteins were measured in five anesthetized adult dogs. Small areas of parietal pleura (approximately 1 cm2) and the underlying endothoracic fascia were exposed through resection of the skin and the intercostal muscles. The portion of the thorax containing the pleural windows was removed from the chest and fixed over a bath of whole autologous plasma, the inner parietal pleural surface facing the bath. Small hemispheric Perspex capsules (surface area 0.28 cm2) connected to a pressure manometer were glued to the pleural windows; a subatmospheric pressure was set into the capsule chamber to create step hydraulic transpleural pressure gradients (delta P) ranging from 5 to 60 cmH2O. Transpleural liquid flows (Jv) and protein concentration of the capsular filtrate (Cfilt) and of the plasma bath were measured at each delta P. The transpleural protein flux (Js) at each delta P was calculated by multiplying Jv by the corresponding Cfilt. The hydraulic conductivity (Lp) of the parietal pleura was obtained from the slope of the Jv vs. delta P linear regression. The average Lp from 14 capsules was 9.06 +/- 4.06 (SD) microliters.h-1.cmH2O-1.cm-2. The mathematical treatment of the Js vs. Jv relationship allowed calculation of the unique Peclet number at the maximal diffusional protein flux and a corresponding osmotic permeability coefficient for plasma protein of 1 x 10(-5) +/- 0.97 x 10(-5) cm/s. The reflection coefficient calculated from the slope of the linear phase of the Js vs. Jv relationship was 0.11 +/- 0.05.(ABSTRACT TRUNCATED AT 250 WORDS)

Parenchymal stress affects interstitial and pleural pressures in in situ lung

After resecting the intercostal muscles and thinning the endothoracic fascia, we micropunctured the lung tissue through the intact pleural space at functional residual capacity (FRC) and at volumes above FRC to evaluate the effect of increasing parenchymal stresses on pulmonary interstitial pressure (Pip). Pip was measured at a depth of approximately 230 microns from the pleural surface, at 50% lung height, in 12 anesthetized paralyzed rabbits oxygenated via a tracheal tube with 50% humidified O2. Pip was -10 +/- 1.5 cmH2O at FRC. At alveolar pressure of 5 and 10 cmH2O, lung volume increased by 8.5 and 19 ml and Pip decreased to -12.4 +/- 1.6 and -12.3 +/- 5 cmH2O, respectively. For the same lung volumes held by decreasing pleural surface pressure to about -5 and -8.5 cmH2O, Pip decreased to -17.4 +/- 1.6 and -23.8 +/- 5 cmH2O, respectively. Because Pip is more negative than pleural pressure, the data suggest that in intact pulmonary interstitium the pressure of the liquid phase is primarily set by the mechanisms controlling interstitial fluid turnover.

Pleural Lymphatics as Regulators of Pleural Fluid Dynamics

Pleural fluid is filtered across the parietal mesothelium in the top of the pleural cavity and removed by lymphatic stomatas in the more dependent mediastinal and diaphragmatic regions. The pleural lymphatics act as a feedback system that regulates pleural liquid volume and its protein composition around a low volume set point.

Distribution of diaphragmatic lymphatic stomata

In seven anesthetized rabbits we measured the size, shape, and density of lymphatic stomata on the peritoneal and pleural sides of the diaphragm. The diaphragm was fixed in situ and processed for scanning electron microscopy. Results are from 2,902 peritoneal and 3,086 pleural fields (each 1,620 microns 2) randomly chosen from the various specimens. Stomata were seen in 9% of the fields examined, and in 30% of the cases they appeared grouped in clusters with 2-14 stomata/field. Stoma density was 250 +/- 242 and 72 +/- 57 (SD) stomata/mm2 on peritoneal and pleural sides, respectively, and it was similar over the muscular and tendinous portion of the two surfaces. The maximum diameter ranged from less than 1 to approximately 30 microns, with an average value of 1.2 +/- 3.1 micron. The ratio of the maximum to the minimum diameter and the surface area averaged 2 +/- 1.4 and 0.7 +/- 2.4 micron 2, respectively. The maximum and minimum diameter and surface area values followed a lognormal frequency distribution, suggesting that stomata geometry is affected by diaphragmatic tension.

Regional blood flow to canine parietal pleura and internal intercostal muscle

Transcapillary Starling forces in the parietal pleura and the underlying interstitium may potentially contribute to the exchange of fluid across this barrier. However, the extent of blood flow to the parietal pleura has not been measured. Thus, using standard microsphere techniques, we compared blood flow to the parietal pleura, including the subpleural interstitium, with blood flow to the adjacent internal intercostal muscle, as well as with flows to other serous tissues, including mediastinal pleura, pericardium, and parietal peritoneum, in anesthetized dogs that were either breathing spontaneously (n = 9) or ventilated to control arterial PCO2 (n = 5). Blood flow (ml.min-1.g-1) was measured after 20 min of equilibration in four successive body positions: right lateral decubitus, supine, left lateral decubitus, and prone. Overall, flow to parietal pleura was not different in spontaneous [1.07 +/- 0.14 (SE)] and mechanically ventilated animals (0.74 +/- 0.11). Flow to the internal intercostal muscle was significantly less than pleural blood flow, averaging 0.24 +/- 0.03 and 0.16 +/- 0.03 in the same groups, although again there was no effect of ventilation mode. Blood flow to other serous tissues in the thoracic cavity, specifically the mediastinal pleura (0.67 +/- 0.14) and pericardium (0.88 +/- 0.22), was similar to parietal pleural flow, whereas that to the parietal peritoneum was an order of magnitude lower (0.09 +/- 0.02, P less than 0.05). Changing body position had no effect on blood flow to any of the sampled tissues. Blood flow to the dorsal aspect of the chest wall muscle in spontaneously breathing animals tended to be greater than that to lateral or ventral portions of the chest wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct measurement of interstitial pulmonary pressure in in situ lung with intact pleural space

We developed an experimental approach to measure the pulmonary interstitial pressure with the micropuncture technique in in situ lungs with an intact pleural space. Experiments were done in anesthetized paralyzed rabbits that were oxygenated via an endotracheal tube with 50% humidified oxygen and kept in either the supine or the lateral position. A small area of an intercostal space was cleared of the intercostal muscles down to the endothoracic fascia. Subsequently a "pleural window" was opened by stripping the endothoracic fascia over a 0.2-cm2 surface and leaving the parietal pleura (approximately 10 microns thick). Direct micropuncture through the pleural window was performed with 2- to 3-microns-tip pipettes connected to a servo-null pressure-measuring system. We recorded pleural liquid pressure and, after inserting the pipette tip into the lung, we recorded interstitial pressure from subpleural lung tissue. Depth of recording for interstitial pressure averaged 263 +/- 122 (SD) microns. We report data gathered at 26, 53, and 84% lung height (relative to the most dependent portion of the lung). For the three heights, interstitial pressure was -9.8 +/- 3, -10.1 +/- 1.6, and -12.5 +/- 3.7 cmH2O, respectively, whereas the corresponding pleural liquid pressure was -3.4 +/- 0.5, -4.4 +/- 1, and -5.2 +/- 0.3 cmH2O, respectively.

Hydraulic conductivity of canine parietal pleura in vivo

The hydraulic conductivity (Lp) of the parietal pleura was measured in vivo in spontaneously breathing anesthetized dogs in either the supine (n = 8) or the prone (n = 7) position and in an excised portion of the chest wall in which the pleura and its adjacent tissue were intact (n = 3). A capsule was glued to the exposed parietal pleura after the intercostal muscles were removed. The capsule was filled with either autologous plasma or isotonic saline. Transpleural fluid flow (V) was measured at several transpleural hydrostatic pressures (delta P) from the rate of meniscus movement within a graduated pipette connected to the capsule. Delta P was defined as the measured difference between capsule and pleural liquid pressures. The Lp of the parietal pleura was calculated from the slope of the line relating V to delta P by use of linear regression analysis. Lp in vivo averaged 1.36 X 10(-3) +/- 0.45 X 10(-3) (SD) ml.h-1.cmH2O-1.cm-2, regardless of whether the capsule was filled with plasma or saline and irrespective of body position. This value was not significantly different from that measured in the excised chest wall preparation (1.43 X 10(-3) +/- 1.1 X 10(-3) ml.h-1.cmH2O-1.cm-2). The parietal pleura offers little resistance to transpleural protein movement, because there was no observed difference between plasma and saline. We conclude that because the Lp for intact parietal pleura and extrapleural interstitium is approximately 100 times smaller than that previously measured in isolated stripped pleural preparations, removal of parietal pleural results in a damaged preparation.

Transperitoneal fluid dynamics in rabbit liver

The peritoneal cavity of 18 anesthetized spontaneously breathing supine rabbits was opened through a midline section. One or two hollow capsules (surface area 0.8 cm2) were glued to the exposed liver surface, filled with whole or 25% diluted plasma, and connected to a transducer and a graduated pipette. Various hydraulic pressures (Pcap) were set in the capsule; at each Pcap the liquid flow per unit surface area (V/S) between the Disse's interstitial space and the capsule was measured from the rate of liquid displacement in the pipette. The slope of the V/S vs. Pcap linear regression was utilized to estimate the hydraulic conductivity of the Glissonian-peritoneal membrane and averaged 5.1 x 10(-3) +/- 4.7 x 10(-3) (SD) ml.h-1.cmH2O-1.cm-2 (n = 25). Hydraulic pressure in the Disse's space (Pd) was measured by closing the capsule against the transducer disconnected from the pipette. At portal and hepatic venous pressures of 7.6 +/- 2.9 and 2.6 +/- 1 cmH2O, respectively, Pd was 2.05 +/- 2 cmH2O. Physiologically, Starling pressure gradients cause fluid transfer from the sinusoids to the Disse's space; transperitoneal fluid filtration only occurs through the liver surface that faces the diaphragm, which corresponds to one-fifth of the total hepatic surface.

Size-related differences in parietal extrapleural and pleural liquid pressure distribution

The hydraulic pressure in the extrapleural parietal interstitium (Pepl) and in the pleural space over the costal side (Pliq) was measured in anesthetized spontaneously breathing supine adult mammals of increasing size (rats, dogs, and sheep) using saline-filled catheters and cannulas, respectively. From the Pliq and Pepl vs. lung height regressions it appears that in all species Pliq was significantly more subatmospheric than Pepl simultaneously measured at the same lung height. The vertical pleural liquid pressure gradient increased with size, amounting to -1, -0.69, and -0.44 cmH2O/cm in rats, dogs, and sheep, respectively. The vertical extrapleural liquid pressure gradient also increased with size, being -0.6, -0.52, and -0.33 cmH2O/cm in rats, dogs, and sheep, respectively. With increasing body size, the transpleural hydraulic pressure gradient (Ptp = Pepl - Pliq) at the level of the right atrium increased from 1.45 to 5.6 cmH2O going from rats to sheep. In all species Ptp increased, with lung height being greatest in the less dependent part of the pleural space.

Liquid drainage through the peritoneal diaphragmatic surface

In 14 spontaneously breathing anesthetized rabbits, we used cyanoacrylate to glue a hollow capsule, at end expiration or at end inspiration, to the peritoneal surface of the tendinous portion of the diaphragm. The capsule was connected to a pressure transducer and a pipette calibrated in microliters. We filled the system with fluid and measured flow into the diaphragmatic surface facing the capsule (Fcap, microliter/cm2), from liquid displacement in the pipette at different hydraulic pressures in the system (Pcap). Pleural liquid pressure was simultaneously measured in the supraphrenic region (Psup). Fcap was positively correlated to transdiaphragmatic pressure gradient (Psup-Pcap) and breathing frequency but was unaffected by protein concentration of capsular fluid. For a breathing frequency of 30 cycles/min and a Psup - Pcap = -2 cmH2O, Fcap was 0.54 microliter.min-1.cm-2 for capsules applied at end expiration and 10-fold greater for capsules applied at end inspiration. Data indicate that the diaphragmatic tendinous portion in rabbits is a draining site for peritoneal fluid and that the conductance of the draining pathways (lymphatic stomata) is related to diaphragmatic tension. In the intact rabbit the average peritoneal fluid drainage through the tendinous portion of the diaphragm (approximately 16 cm2) was estimated at 43 microliters/min.

Pleural and extrapleural interstitial liquid pressure measured by cannulas and micropipettes

In 15 anesthetized apneic, oxygenated rabbits we simultaneously measured pleural liquid and interstitial extrapleural parietal pressures by using catheters and/or cannulas and micropipettes connected to a servonull system. With the animal in lateral posture, at an average recording height of 4.4 +/- 0.9 (SD) cm from the most dependent part of the cavity, the extrapleural catheter and the pleural cannula yielded -2.5 +/- 0.6 and -5.5 +/- 0.2 cmH2O; the corresponding values for micropipette readings in the two compartments were -2.4 +/- 0.6 and -5.4 +/- 0.4 cmH2O, respectively (not significantly different from those measured with catheters and cannulas). In the supine animal, interstitial extrapleural catheter pressure data obtained at recording heights ranging from 15 to 80% of pleural cavity lay on the identity line when plotted vs. the micropipette pressure values simultaneously gathered from the same tissues. We conclude that 1) micropipettes and catheters-cannulas yield similar results when recording from the same compartment and 2) the hydraulic pressure in the parietal extrapleural interstitium is less negative than that in the pleural space.

Intrapleural liquid flow down a gravity-dependent hydraulic pressure gradient

We studied the vertical movement of 2 mg technetium-labeled albumin injected intrapleurally in 0.5 ml saline (15% of pleural liquid volume) in eight spontaneously breathing anesthetized dogs subject to a sudden change in posture (prone to supine or vice versa). The albumin movements were evaluated through a large field gamma camera placed laterally to the animal and detecting total (AT) and regional activities from two superimposed equal areas (At and Ab, top and bottom, respectively). The At/Ab ratio decreased from 2.1 to 1.3 in four animals up to 20 min from the change in posture and from 0.9 to 0.5 in four more animals studied from 50 to 90 min from turning maneuver. The rate of change in At and Ab was similar in the two groups of animals and unaffected by the acquisition posture. AT decreased by 7.7 and 3.5% for the two groups, respectively, reflecting albumin clearance from the pleural space. The opposite time course of regional activities and the independence of their rate of change of the At/Ab ratio and of the animal posture suggest a top-to-bottom albumin transfer occurring through a bulk flow of liquid estimated at 0.006 ml.kg-1.h-1. The data are consistent with a measured vertical pleural liquid pressure gradient that does not reflect a hydrostatic condition.

Gravity-dependent distribution of parietal subpleural interstitial pressure

Using liquid-filled catheters, we recorded, in 30 anesthetized, spontaneously breathing supine rabbits, the hydraulic pressure from the parietal subpleural interstitial space (Pspl). Through a small exposed area of parietal pleura a plastic catheter (1 mm ED), with a closed and smooth tip and several holes on the last centimeter, was carefully advanced between the muscular layer and the parietal pleura, tangentially to the pleural surface to reach the submesothelial layer. Simultaneous measurements of pleural liquid pressure (Pliq) were obtained from intrapleurally placed cannulas. End-expiratory Pspl decreased (became more negative) with increasing height (LH) according to the following: Pspl (cmH2O) = -1 - 0.4 LH (cm), the corresponding equation for Pliq being Pliq (cmH2O) = -1.5 - 0.7 LH (cm). Thus at end expiration a transpleural hydraulic pressure difference (Pliq-Pspl) developed at any height, increasing from the bottom to the top of the cavity as Pliq - Pspl (cmH2O) = -0.5 - 0.3 LH (cm). The Pliq-Pspl difference increased during inspiration due to the much smaller tidal change in Pspl than in Pliq. By considering the gravity-dependent distribution of the functional hydrostatic pressure in the systemic capillaries of the pleura (Pc) and the Pspl and Pliq values integrated over the respiratory cycle we estimated that on the average, the Pc-Pspl difference is sevenfold larger than the Pspl-Pliq difference.

Contribution of Starling and lymphatic flows to pleural liquid exchanges in anesthetized rabbits

We studied the time course of volume and protein reabsorption of a 2-ml hydrothorax using whole (WP) or diluted (DP) homologous plasma injected into the right pleural cavity in anesthetized spontaneously breathing supine rabbits. Animals were killed at 5 (WP, n = 4; DP, n = 3), 36 (WP, n = 3; DP, n = 4), 55 (WP, n = 4), 90 (WP, n = 8; DP, n = 4), and 150 (WP, n = 4; DP, n = 5) min after the injection. The volume and protein content of the pleural liquid in control conditions (n = 12) amounted to 0.35 +/- 0.015 (SE) ml/kg and 1.8 +/- 0.27 g/100 ml, respectively, which are not significantly different at 90 min (n = 7). Pleural liquid volume decreased at a similar rate during WP or DP reabsorption according to the equation V = 0.84 +/- 0.05 X e-0.02t, with net reabsorptive flow expressed as dV/dt. The globulin quantity (Q) of the pleural liquid for WP and DP, respectively, decreased according to the equations Qwp = 1 + 1.5 X e-0.04t and Qdp = 0.7 + 0.6 X e-0.03t. Assuming a major lymphatic globulin clearance and no filtration into the cavity, we obtained lymph flow using the equation VL = dQ/dt X l/C where dQ/dt is calculated from the equations for Qwp and Qdp and C represents globulin concentration. The Starling flow (Vs) was then calculated by the equation Vs = dV/dt-VL. With increasing time, lymph flow was found to decrease progressively and was not significantly different from net flow with DP, which implied a Starling flow value of zero. During WP reabsorption, lymph flow initially exceeded the net flow, with the difference disappearing at approximately 60 min; accordingly, Starling filtration flow decreased progressively, becoming zero at the same time.