Effect of UVB 311 nm irradiation on normal human skin

OBJECTIVE: To determine the relative efficacy and morbidity of Ho:YAG versus Nd:YAG laser treatment of bullous lung disease in an animal model. SUMMARY BACKGROUND DATA: Laser coagulation procedures for treatment of emphysematous pulmonary bullae and heterogeneous emphysema continue to evolve. The role of lasers in lung volume reduction surgery remains controversial due to issues of relative efficacy and morbidity. The Nd:YAG laser is most commonly used for these procedures. We hypothesized that the shallower penetration of the Ho:YAG laser may be better suited for laser bullae coagulation and emphysema lung volume reduction with increased efficacy and reduced lung injury. METHODS: Thirty New Zealand White rabbits (15 normal rabbits; 15 with bullous lung disease) were evaluated with Ho:YAG compared to Nd:YAG laser exposures. Bullae were coagulated by either Ho:YAG or Nd:YAG treatment. In all animals (bullous-induced and normals), unaffected lung tissue in the upper lobes and contralateral lungs were treated with 5 spot exposures of Nd:YAG and Ho:YAG, each to assess depth of lung injury. Animals were sacrificed at Days 0, 7, and 21 and their lungs were examined histologically. RESULTS: Ho:YAG and Nd:YAG exposures caused equivalent lung injury to normal lung tissue. In the acute phase, parenchymal necrosis depth was similar for both Ho:YAG and Nd:YAG (850 +/- 273 microns vs. 900 +/- 270 microns respectively, p = 0.7). By Day 7, lung necrosis depth was 925 +/- 133 microns Ho:YAG vs. 1225 +/- 235 microns Nd:YAG (p = 0.33), and lung fibrosis depth was 300 +/- 134 microns Ho:YAG vs. 558 +/- 127 microns Nd:YAG (p = 0.11). By Day 21, pulmonary parenchymal necrosis was not seen. Pleural fibrosis depth was maximal at Day 21, reaching 250 +/- 102 microns for Ho:YAG vs. 300 +/- 156 microns Nd:YAG (P = 0.88). Pleural necrosis depth was 67 +/- 42 microns Ho:YAG vs 48 +/- 34 microns Nd:YAG (p = 0.42) on Day 7 and resolved by Day 21. During surgical coagulation procedures, the Ho:YAG laser was dramatically more efficient in coagulating bullae. The Ho:YAG laser required less exposure at equivalent power and resulted in immediate desiccation of bullae, in sharp contrast to the Nd:YAG laser. CONCLUSIONS: Because the Ho:YAG was more effective and did not result in more acute lung injury than the standard Nd:YAG laser in this study, Ho:YAG lasers may have improved potential for laser treatment of bullae or lung volume reduction surgery (LVRS) compared to Nd:YAG lasers.     

Respiratory mechanics in patients with tense cirrhotic ascites

Lung volumes are decreased by tense ascites and increase after large volume paracentesis (LVP). The overall effect of ascites and LVP on the respiratory function is poorly understood. We studied eight cirrhotic patients with tense ascites before and after LVP. Inspiratory muscle force (maximal transdiaphragmatic pressure (Pdi,max), and the lowest pleural pressure (Pp1,min)) was assessed while the patients were seated. Rib cage and abdominal volume displacements, as well as pleural and gastric pressures were measured during quiet breathing while the patients were supine. Pdi,max and Ppl,min were normal and did not change after LVP (from 84.2+/-19.7 to 85.2+/-17.0 cmH2O and from 68.3+/-19.7 to 74+/-15.9 cmH2O, respectively). The abdominal contribution to the generation of tidal volume was greater than that of the rib cage (79 vs 21%), a pattern which did not change after LVP (73 and 27%). Before LVP, tidal swings both of pleural pressure (Ppl,sw) and transdiaphragmatic pressure (Pdi,sw) were large (15.3+/-4.3 and 18.5+/-3.9 cmH2O, respectively) and the load on inspiratory muscles was increased as a consequence of elevated dynamic elastance of the lung (El,dyn) (11.4+/-2.6 cmH2O x L(-1)) and ("intrinsic") positive end-expiratory pressure (PEEPi) (4.3+/-3.5 cmH2O). LVP reduced the load on the inspiratory muscles, as shown by the significant decrease in Ppl,sw (10.6+/-2.0 cmH2O), Pdi,sw (12.8+/-3.0 cmH2O), El,dyn (10.0+/-2.0 cmH2O x L(-1)) and PEEPi (1.1+/-1.3 cmH2O). The amount of fluid removed was closely related to changes in Ppl,sw and PEEPi. We conclude that the strength of the inspiratory muscles is normal or reduced in seated cirrhotic patients. In the supine position, tense ascites results in an increase in lung elastic load and development of positive end-expiratory pressure, with a consequent overload and increased activation of inspiratory muscles. Large volume paracentesis decreases overloading and activation, but does not change the strength of the inspiratory muscles.     

Pressure-controlled, inverse ratio ventilation that avoids air trapping in the adult respiratory distress syndrome

OBJECTIVES: To investigate physiologic and outcome data in patients switched from volume-cycled conventional ratio ventilation to pressure-controlled inverse ratio ventilation that did not produce air trapping and intrinsic positive end-expiratory pressure (PEEP). SETTING: Medical intensive care unit. DESIGN: Retrospective analysis of crossover data and outcome. PATIENTS: Fourteen patients with the adult respiratory distress syndrome who were receiving mechanical ventilation with volume-cycled, conventional ratio ventilation followed by pressure-controlled, inverse ratio ventilation. INTERVENTIONS: Our approach to pressure-controlled, inverse ratio ventilation was to use tidal volumes and applied PEEP values comparable to those volumes and values used on volume-cycled, conventional ratio ventilation, use inspiratory times to increase mean airway pressure instead of additional applied PEEP, and avoid air trapping (intrinsic PEEP). MEASUREMENTS AND MAIN RESULTS: With this approach, there was a reduction in peak airway pressure from 53 +/- 8.5 (SD) to 40 +/- 5.9 cm H2O (p < .01), and an increase in mean airway pressure from 20 +/- 3.9 to 30 +/- 5.2 cm H2O (p < .01). Tidal volume, mean inflation pressure, and compliance did not change. Oxygenation (PaO2) improved from 57 +/- 11.3 torr (7.6 +/- 1.5 kPa) to 94 +/- 40.2 torr (12.5 +/- 5.4 kPa) (p = .01) but the oxygenation index (mean airway pressure x FIO2 x 100/PaO2) did not change significantly (25.9 +/- 10.3 to 27.2 +/- 12.2). There was no significant change in PaCO2 or pH even though delivered minute ventilation decreased from 17.4 +/- 4.3 to 14.8 +/- 5.8 L/min (p = .02). Cardiac index slightly decreased, but hemodynamic values were otherwise stable. Only three of the 14 study patients survived. CONCLUSIONS: These data demonstrate that oxygenation is primarily a function of mean airway pressure, and that longer inspiratory times can be used as an alternative to applied PEEP to increase this oxygenation. If no air trapping develops, lung inflation pressures and delivered volumes remain constant with this approach. Because the technique was used only in patients refractory to conventional techniques, the poor outcome is not surprising.     

Coronary flow analysis during autoperfusion angioplasty

BACKGROUND: Autoperfusion balloons are available for the protection of the myocardium during balloon angioplasty. The aortic pressure is the driving force that delivers blood to the distal vessel during balloon inflation. Autoperfusion balloons can achieve sufficient flow rates in vitro. The use of these devices is recommended in high-risk patients in danger of haemodynamic collapse during balloon inflation. The quantity of the distal blood flow during balloon inflation in vivo is still unknown. OBJECTIVES: To measure distal coronary perfusion using Doppler guidewires during percutaneous transluminal coronary angioplasty (PTCA) with autoperfusion balloons. METHODS: Coronary flow velocity was measured with 0.014-inch Doppler guidewires bypassing the autoperfusion balloon in eight patients undergoing elective PTCA (degree of stenosis 74 +/- 7.2%). We used balloons with diameters of 3.0 and 3.5 mm. The coronary diameter at the location of the flow measurements was obtained by quantitative angiography in two planes. Coronary blood flow was calculated as the luminal area multiplied by the average peak flow velocity of the Doppler wire divided by 2. Coronary flow velocity reserve was measured before and after angioplasty by intracoronary injection of adenosine. RESULTS: Coronary blood flow was 35 +/- 11.6 ml/min before PTCA. During average inflation times of 4.6 +/- 0.9 min, coronary blood flow was 19 +/- 3.8 ml/min (P = 0.002) after withdrawing the guidewire in the autoperfusion balloon. Five minutes after angioplasty it increased to 42 +/- 13.5 ml/min (P < 0.001). Four patients had electrocardiographic changes during balloon inflation; three patients reported chest pain. One patient required a stent because of a local dissection. To achieve satisfactory angiographic results (residual stenosis 11 +/- 8.5%), we performed 2.1 +/- 0.78 inflations on average with a cumulative inflation time of 8.8 +/- 3.35 min. Coronary flow velocity reserve increased from 1.3 +/- 0.20 to 2.2 +/- 0.22 (P < 0.001). CONCLUSIONS: Using the autoperfusion balloon we measured a coronary blood flow during angioplasty of 56 +/- 10.3% of the distal perfusion before PTCA. In high-risk patients dependent on adequate coronary perfusion, autoperfusion balloons are not able to provide sufficient distal coronary blood flow during balloon inflation. In these patients active coronary or circulatory support devices are recommended.     

Physiological determinants of inspiratory effort sensation during CO2 rebreathing in normal subjects

1. The physiological basis of inspiratory effort sensation remains uncertain. Previous studies have suggested that pleural pressure, rather than inspiratory muscle fatigue, is the principal determinant of inspiratory effort sensation. However, only a limited range of inspiratory flows and breathing patterns have been examined. We suspected that inspiratory effort sensation was related to the inspiratory muscle tension-time index developed whatever the breathing pattern or load, and that this might explain the additional rise in sensation seen with hypercapnia. 2. To investigate this we measured hypercapnic rebreathing responses in seven normal subjects (six males, age range 21-38 years) with and without an inspiratory resistive load of 10 cm H2O. Pleural and transdiaphragmatic pressures, mouth occlusion pressure and breathing pattern were measured. Diaphragmatic and ribcage tension-time indices were calculated from these data. Inspiratory effort sensation was recorded using a Borg scale at 30s intervals during each rebreathing run. 3. Breathing pattern and inspiratory pressure partitioning were unrelated to changes in inspiratory effort sensation during hypercapnia. Tension-time indices reached pre-fatiguing levels during both free breathing and inspiratory resistive loading. 4. Stepwise multiple regression analysis using pooled mechanical, chemical and breathing pattern variables showed that pleural pressure was more closely related to inspiratory effort sensation than was transdiaphragmatic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of changes in intraocular pressure on human ocular haemodynamics

PURPOSE: Myogenic autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. Ocular perfusion pressure is defined as the difference between ocular arterial pressure and ocular venous pressure, the latter dependent on intraocular pressure (IOP). The aim of the present study was to investigate the effect of moderate increases in IOP on ocular haemodynamics. METHODS: Changes in IOP (+ 10 mmHg, +20 mmHg) were induced by a suction cup in 10 healthy subjects. Ocular fundus pulsations in the macula and the optic disc were measured by laser interferometry; blood flow velocities in the central retinal artery (CRA) and in the ophthalmic artery (OA) were measured by Doppler sonography. RESULTS: Changes in IOP caused a significant reduction in fundus pulsations, which was more pronounced in the macula (at +10 mmHg: -9 +/- 2%, p < 0.01; at +20 mmHg: -19 +/- 3%, p < 0.001) than in the optic disc (at +10 mmHg: -5 +/- 2% (ns); at +20 mmHg: -9 +/- 3%, p < 0.01). Mean flow velocity in the CRA was reduced by -5 +/- 3% at +10 mmHg (ns) and by -14 +/- 5% at +20 mmHg (p < 0.005), resistive index was increased by +4 +/- 1% at +10 mmHg (p < 0.05) and by +6 +/- 2% at +20 mmHg (p < 0.01). In contrast, a rise in IOP did not affect blood flow parameters in the OA. CONCLUSIONS: Our results from fundus pulsation measurements indicate that choroidal blood flow decreases when IOP is increased. The Doppler sonographic findings in the CRA indicate reduced blood flow velocity in this artery during raised IOP.     

Influence of inflation and atelectasis on the hypoxic pressor response in isolated dog lung lobes

Apnoeic left lower lobes of dog lungs were inflated by increasing alveolar pressure or decreasing pleural pressure, or the lobes were collapsed and exposed to decreasing pleural pressure with the bronchus occluded. Under each of these conditions the lobe could be made 'hypoxic' by perfusion with mixed venous blood or 'normoxic' by perfusion with systemic arterial blood. Inflation of the lobes diminished the hypoxic presor response. The relative influence of decreasing pleural pressure on inflated and collapsed lobes was such that at low pleural pressures resistance to flow through the hypoxic atelectatic lobe was no greater than that through the inflated normoxic lobe. The results indicated that the level of lung inflation can alter the effectiveness of the hypoxic pressor response in reducing perfusion to underventilated regions.     

Effect of a novel prosthetic anal neosphincter on human colonic blood flow

BACKGROUND: An artificial anal sphincter has been developed which aimed to simulate the normal physiology of the anorectum. As a prelude to human implantation the present study reports the effect of inflation of this device on colonic perfusion in patients undergoing colectomy, which was assessed by using a laser Doppler scanner. METHODS: Eleven patients (median age 49.8 (range 24.3-78.7) years) were studied. Five patients had inflammatory bowel disease (IBD). The neosphincter was placed around the bowel and progressively inflated. The model was designed so that blood flow changes to the colon under the neosphincter would be reflected in the distal segment of the bowel, which could be scanned by the laser Doppler scanner. RESULTS: The blood flow in the colon distal to the device was significantly higher in patients with IBD (mean(s.e.m.) 288.6(71.9) versus 211.1(57.6) perfusion units; P < 0.001). The mean(s.e.m.) 'biological zero' value was 46(14) perfusion units. Blood flow distal to the neosphincter decreased progressively with increased sphincteric compression by 0.66 per cent per mmHg applied pressure in controls and 0.35 per cent per mmHg in patients with IBD (P < 0.05). CONCLUSION: These results suggest that at the planned operating occlusion pressure (less than 45 mmHg) this neosphincter should not put the vascularity of the human colon at risk.     

The minimal sequence needed to define a functional DNA terminator in Bacillus subtilis

BACKGROUND: We wished to determine whether transcutaneous oximetry or laser Doppler flowmetry (LDF) could identify patients at risk for wound failure after conservative, limb-sparing surgery for extremity sarcomas. METHODS: Studies were performed on postoperative days (PODs) 1, 4/5, 7, and 9. Measurements of transcutaneous oxygen pressure (tcPO2) were taken at breathing room air (BL) and 100% oxygen (rate tcPO2). LDF measurements were taken at multiple sites along the wound, and a perfusion index was calculated. RESULTS: Twenty-four patients were studied. Four (17%) had nonhealing wounds. There was no difference in tcPO2 (BL) values between healed and nonhealing wounds. Measurement of rate tcPO2 on POD 1 was significantly lower in the nonhealing wounds than in those with normal healing (28.5 +/- 12.1 mm Hg vs 14.3 +/- 16.2 mm Hg, mean +/- SD, p = 0.03). Rate tcPO2 values increased significantly in healing wounds from POD 1 to PODs 7 and 9 (p = 0.006, p = 0.009). This increase was absent in nonhealing wounds. A clear separation was noted in rate tcPO2 values between groups, with a minimum rate tcPO2 value recorded in a healed wound of 9 mm Hg/min, compared with the maximum value in a nonhealing wound of 7 mm Hg/min. The LDF perfusion index failed to predict wound healing at any of the measured time points. CONCLUSIONS: This study showed that measurement of tcPO2 during oxygen inhalation can accurately predict wound healing in patients after excision of an extremity sarcoma.     

Evaluation of respiratory muscle strength in patients with interstitial lung changes based on simultaneous measurement of esophageal and mouth pressure

A well know good relation between nasal and oesophageal inspiratory pressures exists in healthy and in COPD patients "sniff manoeuvres. Similar results are obtained using "gasp" maneuvers. The aim of the study was to appreciate the usefulness of "gasp" for evaluation of inspiratory muscles strength in ILD patients. 18 ILD patients were examined: group A consisted of 9 pts (8M+IF) aged 35 +/- 8.6 yrs, with static compliance > 70% pred. (mean 98.6 +/- 16.3), group B consisted of 9 pts (6M + 3F) (aged 52 +/- 13.0) with static compliance < 70% pred. (mean 37.2 +/- 12.0), Pmo and Poe (Milic-Emili method) were measured simultaneously during breathing with Pflex device (1.7 mm diameter). Results were stored in a computer for further analysis. In all patients spirometry, plethysmography and maximal inspiratory (MIP) and maximal expiratory (MEP) pressure measurements were performed. Poe and Pmo in group A were nearly the same (8.16 +/- 1.82 vs. 8.35 +/- 2.74 kPa), but in the group B Pmo was lower than Poe (4.81 +/- 1.59 vs. 6.19 +/- 2.03 kPa; p < 0.0005). We conclude that "gasp" - Pmo is a useful method for inspiratory muscle strength measurement only in ILD patients with normal static compliance but in ILD patients with decreased compliance "gasp" - Poe measurement in necessary.     

The Hering-Breuer reflex in anesthetized infants: end-inspiratory vs. end-expiratory occlusion technique

Both end-inspiratory (EIO) and end-expiratory (EEO) occlusions have been used to measure the strength of the Hering-Breuer inflation reflex (HBIR) in infants. The purpose of this study was to compare both techniques in anesthetized infants. In each infant, HBIR activity was calculated as the relative prolongation of expiratory and inspiratory time during EIO and EEO, respectively. Respiratory drive was assessed from the change in airway pressure during inspiratory effort against the occlusion, both at a fixed time interval of 100 ms (P0.1) and a fixed proportion (10%) of the occluded inspiratory time (P10%). Twenty-two infants [age 14.3 +/- 6. 4 (SD) mo] were studied. No HBIR activity was present during EIO [-11.8 +/- 15.9 (SD) %]. By contrast, there was significant, albeit weak, reflex activity during EEO [HBIR: 27.2 +/- 17.4%]. A strong HBIR (up to 310%) was elicited in six of seven infants in whom EIO was repeated after lung inflation. P0.1 was similar during both types of occlusions, whereas mean +/- SD P10% was lower during EEO than during EIO: 0.198 +/- 0.09 vs. 0.367 +/- 0.15 kPa, respectively (P < 0.01). These data suggest a difference in the central integration of stretch receptor activity in infants during anesthesia compared with during sleep.     

Respiratory effort sensation during exercise with induced expiratory-flow limitation in healthy humans

Nine healthy subjects (age 31 +/- 4 yr) exercised with and without expiratory-flow limitation (maximal flow approximately 1 l/s). We monitored flow, end-tidal PCO2, esophageal (Pes) and gastric pressures, changes in end-expiratory lung volume, and perception (sensation) of difficulty in breathing. Subjects cycled at increasing intensity (+25 W/30 s) until symptom limitation. During the flow-limited run, exercise performance was limited in all subjects by maximum sensation. Sensation was equally determined by inspiratory and expiratory pressure changes. In both runs, 90% of the variance in sensation could be explained by the Pes swings (difference between peak inspiratory and peak expiratory Pes). End-tidal PCO2 did not explain any variance in sensation in the control run and added only 3% to the explained variance in the flow-limited run. We conclude that in healthy subjects, during normal as well as expiratory flow-limited exercise, the pleural pressure generation of the expiratory muscles is equally related to the perception of difficulty in breathing as that of the inspiratory muscles.     

Laser Doppler imaging and capillary microscopy in ischemic ulcers

The local distribution of laser Doppler flux (mainly thermoregulatory perfusion) and capillary density (nutritive circulation) within 25 ischemic leg ulcers and their adjacent skin were investigated. For this purpose the technique of laser Doppler imaging and capillary microscopy were applied. In each ulcer a non granulation tissue area (NGTA), a granulation tissue area (GTA) and in adjacent skin a skin area (SA) were defined. In these areas the average laser Doppler area flux (arbitrary units, AU) and the number of capillaries/mm2 were determined for each patient. The mean+/-S.D. of laser Doppler area fluxes were: NGTA 1.30+/-1.93, GTA 2.13+/-1.53 and SA 1.21+/-0.77 AU, respectively. The differences between GTA and NGTA or SA was statistically significant (p < 0.001, each) The mean+/-S.D. of capillary densities were as follows: NGTA: 0.56+/-2.06, GTA 6.76+/-8.39 and SA 16.80+/-7.38 capillaries/mm2, respectively. The following differences were statistically significant: NGTA versus GTA (p < 0.01) and SA versus NGTA or GTA (p < 0.001, each). In conclusion following characteristics of the three areas can be described: In NGTA low laser Doppler area flux is combined with very low capillary density (ulcer area without healing). In GTA the highest laser Doppler area flux of all three areas and an intermediate capillary density (wound healing) is found. In SA an intermediate laser Doppler area flux is associated with the highest capillary density of all three areas with the healing process nearly completed and no granulation tissue.     

Lung volume and effectiveness of inspiratory muscles

We related inspiratory muscle activity to inspiratory pressure generation (Pmus) at different lung volumes in five seated normal subjects. Integrated electromyograms were recorded from diaphragmatic crura (Edi), parasternals (PS), and lateral external intercostals (EI). At 20% increments in the vital capacity (VC) subjects relaxed and then made graded and maximal inspiratory efforts against an occluded airway. At any given level of pressure generation, Edi, PS, and EI increased with increasing lung volume. The Pmus generated at total lung capacity as a fraction of that at a low lung volume (between residual volume and 40% VC) was 0.39 +/- 0.15 (SD) for the diaphragm, 0.20 +/- 0.06 for PS, and 0.22 +/- 0.04 for the lateral EI muscles. Our results indicate a lesser volume dependence of the Pmus-EMG relationship for the diaphragm than for PS and EI muscles. This difference in muscle effectiveness with lung volume may reflect differences in length-tension and/or geometric mechanical advantage between the rib cage muscles and the diaphragm.     

Clinical cancer research in a managed-care environment

PURPOSE: Autoregulation of optic nerve head blood flow (Fonh) in response to decreases in perfusion pressure has been demonstrated in animals and humans. The aim of this study was to determine change in Fonh when systemic blood pressure is increased. METHODS: Blood flow parameters, i.e. relative mean velocity, number, and flux of red blood cells in the ONH tissue (Velonh, Volonh and Fonh, respectively) were measured by laser Doppler flowmetry in one eye of 13 normal subjects (aged 16 to 58 years), at baseline, during, and after isometric exercises consisting of squatting. Brachial artery blood pressure was measured by sphygmomanometry. IOP was measured at baseline and at the end of squatting. RESULTS: During squatting mean arterial pressure increased from 103 +/- 6 mm Hg to 139 +/- 58 mm Hg (average +/- 95% confidence interval), IOP increased from 13 +/- 0.5 to 17 +/- 1 mm Hg. An average increase in PPm from 56 +/- 4 to 80 +/- 7 mm Hg induced no significant (p > 0.05) change in the blood flow parameters. The sensitivity (detection threshold) of the blood flow changes was 8%. CONCLUSION: This study shows for the first time in human autoregulation of Fonh when PPm is increased by increasing the systemic blood pressure.     

Spirometrically controlled quantitative CT for assessing diffuse parenchymal lung disease

OBJECTIVE: Assessment of lung attenuation by CT reflects changes in the air-to-tissue ratio of the lung. We have analyzed the interdependence of intrathoracic gas volume, lung morphology, and functional disorder by high resolution CT (HRCT) to assess quantitative disease threshold in obstructive and restrictive diffuse lung disease. MATERIALS AND METHODS: Pulmonary HRCT was performed on 24 healthy volunteers, 11 patients with chronic obstructive pulmonary disease (COPD), and 16 patients with idiopathic lung fibrosis (IPF). HRCT measurement was standardized by taking three scans at the carina +/- 5 cm and by defining inspiration levels by percent vital capacity (VC) via spirometrically gating to the scanner. RESULTS: The mean lung density at 50% VC (DL50) for healthy subjects was -819 +/- 3.8 (mean +/- SEM) HU. In contrast, COPD DL50 was lower, averaging -861 +/- 6.4 HU, and the IPF DL50 was considerably higher (-731 +/- 17.7 HU), both significantly different (p < 0.001) compared with the control group. The accuracy of quantitative HRCT at different inspiration levels was evaluated by scanning the basal layer at 20, 50, and 80% VC. The control values were -747 +/- 5.6, -816 +/- 3.6, and -855 +/- 3.0 HU, respectively, which were significantly higher (p < 0.001) than those seen in COPD patients at 20 and 50% VC. Again, the IPF patients exhibited increased lung density (p < 0.001) at all inspiratory levels. Discrimination power was best among all cohorts at 20 and 50% VC. Position-dependent artifacts on lung density were quantified by the anteroposterior density gradient (APG). Irrespective of the underlying disease, APG at 50 and 80% VC was similar, but was up to twofold higher at 20% VC, indicating that quantitative estimates near RV may misrepresent mean lung density. CONCLUSION: Our data indicate that quantitative HRCT measurements should be performed not near full inspiration or expiration, but at an intermediate degree of lung inflation, e.g., 50% VC, for reasons of accuracy, intra- and intersubjective comparability, and feasibility. We conclude quantitative HRCT to be a sensitive tool for the evaluation of diffuse parenchymal lung disease.     

Effects of static lung inflation on sympathetic activity in human muscle nerves at rest and during asphyxia

Muscle sympathetic activity is inhibited during the second half of phasic lung inflation associated with normal (negative pressure) breathing or artificial ventilation with intermittent positive-pressure, and this inspiratory inhibition appears unrelated to the associated changes in arterial pressure. In this present study we tested the hypothesis that a static inflation of the lungs would cause a sustained inhibition of muscle sympathetic activity. Microneurographic techniques were used to record muscle sympathetic activity from the peroneal nerve, and arterial pressure was monitored continuously by finger-pulse photoplethysmography (Finapres). In nine subjects static lung inflation, brought about either actively or passively, caused a pronounced and sustained increase in sympathetic activity (not the predicted decrease) that could not be explained by changes in arterial pressure. When delivered at the end of a voluntary end-expiratory apnoea, static lung inflation caused an initial inhibition of the large chemoreceptor-induced sympathetic bursts and a subsequent excitation that was sustained for the duration of the lung inflation. These observations indicate that respiration can affect muscle sympathetic activity in humans in two opposing ways: inhibition during phasic increases in lung volume, and excitation during large static increases in lung volume. Neither phenomenon depends on changes in arterial pressure, and hence influences of carotid arterial and aortic (high-pressure) baroreceptors can be excluded. We suggest that the initial inhibition is evoked from lung or chest-wall receptors and the static exitation from unloading of cardiopulmonary (low pressure) baroreceptors.     

Measurement of lung expansion with computed tomography and comparison with quantitative histology

The total and regional lung volumes were estimated from computed tomography (CT), and the pleural pressure gradient was determined by using the milliliters of gas per gram of tissue estimated from the X-ray attenuation values and the pressure-volume curve of the lung. The data show that CT accurately estimated the volume of the resected lobe but overestimated its weight by 24 +/- 19%. The volume of gas per gram of tissue was less in the gravity-dependent regions due to a pleural pressure gradient of 0.24 +/- 0.08 cmH2O/cm of descent in the thorax. The proportion of tissue to air obtained with CT was similar to that obtained by quantitative histology. We conclude that the CT scan can be used to estimate total and regional lung volumes and that measurements of the proportions of tissue and air within the thorax by CT can be used in conjunction with quantitative histology to evaluate lung structure.     

Functional consequences of acute collagen degradation studied in crystalloid perfused rat hearts

OBJECTIVES: The impact of acute collagen disruption by the disulfide donor, 5,5'-dithio-2-nitrobenzoic acid (DTNB) on ventricular properties was tested in rat hearts. METHODS: Collagen was degraded acutely in 13 isolated, isovolumically contracting rat hearts by perfusion with 1 mM DTNB added to Krebs-Henseleit solution for 1 hour followed by 2-hour perfusion with normal solution. Another 13 hearts were perfused with normal solution for 3 hours (Control). RESULTS: Collagen content was 3.5 +/- 0.5% of ventricular dry weight in control group compared with 2.1 +/- 0.4% in DTNB group (decrease by 40%, p < 0.01). Scanning electron micrographs revealed loss of the delicate collagen network surrounding muscle fibers in DTNB treated hearts. Developed pressure at a fixed volume decreased to 86 +/- 17% of the baseline value after 3-hour perfusion in the control group, whereas in DTNB treated hearts developed pressure fell to 68 +/- 13% (p < 0.01). End-diastolic pressure was set at 5 mmHg at the beginning of the experiment and rose to 15 +/- 8 mmHg in control and 30 +/- 13 mmHg (p < 0.01) in the treated hearts. Concomitantly, wet-to-dry weight ratio increased from 5.63 +/- 0.26 in control to 6.07 +/- 0.11 (p < 0.05) in the DTNB treated hearts. A separate set of experiments on isolated myocytes excluded the possibility of a direct effect of DTNB on myocyte contractile function. CONCLUSIONS: These data suggested that with 40% collagen disruption by DTNB there is a significant increase in tissue edema that results in a decrease in chamber capacitance; in addition, there is a significant decrease in systolic performance which reflects the combined effect of edema and loss of collagen.     

The effects of pulmonary rehabilitation combined with inspiratory muscle training on pulmonary function and inspiratory muscle strength in elderly patients with chronic obstructive pulmonary disease]

It has been suggested that pulmonary rehabilitation compined with inspiratory muscle training (IMT) might improve pulmonary function and respiratory muscle strength in elderly patients with chronic obstructive pulmonary disease (COPD). To test this hypothesis, inspiratory muscle strength (PImax), expiratory muscle strength (PEmax) and resting pulmonary function were measured in 13 elderly patients with COPD (aged 70.3 +/- 2.7 years). Inspiratory muscle training (IMT) was performed for 15 min twice a day, using a pressure threshold device, for a total of 12 weeks. The inspiratory threshold was set at 15% of maximal inspiratory pressure (PImax) for each individual. Pulmonary rehabilitation was performed for 12-h sessions over a 12-week period. Patients with COPD were assigned randomly to two groups: pulmonary rehabilitation combined with IMT (group A) (n = 7), and conventional pulmonary rehabilitation only (group B) (n = 6). Functional residual capacity (FRC) decreased significantly from 4.3 +/- 0.4 L at baseline to 3.9 +/- 0.4 L after rehabilitation (p < 0.01), Vp significantly increased from 4.6 +/- 0.8 L/sec at baseline to 5.1 +/- 0.7 L/sec after rehabilitation (p < 0.05) and the PImax increased significantly from 51.5 +/- 5.4 cmH2O at baseline to 80.9 +/- 7.0 cmH2O after rehabilitation (p < 0.02) in group A. However, these variables did not change in group B. There was no improvement in the 10-minutes walking distance of group A, but there was a significant increase in that of group B. It can be concluded that pulmonary rehabilitation combined with IMT improves pulmonary function and inspiratory muscle strength in elderly patients with COPD.