Hypertensive pulmonary vascular disease in states of chronic hypoxia

Management of combined pre- and post-capillary pulmonary hypertension in advanced heart failure with reduced ejection fraction

Management of pulmonary hypertension (PH) has remained an unmet need in advanced left heart failure with reduced ejection fraction. In fact, patients are frequently denied heart transplant due to untreated pulmonary hypertension. The availability of mechanically circulatory devices and PH therapies has provided a ray of hope. PH specific therapies are currently not FDA approved for patients with left heart failure with reduced ejection fraction. However, clinicians have used these medications in anecdotal manner. With this review, we want to highlight the expanding use of PH specific therapy and mechanical circulatory devices in the management of PH in the setting of advanced heart failure with reduced ejection fraction.

Melatonin Attenuates Pulmonary Hypertension in Chronically Hypoxic Rats

Chronic hypoxia induces pulmonary hypertension and vascular remodeling, which are clinically relevant to patients with chronic obstructive pulmonary disease (COPD) associated with a decreased level of nitric oxide (NO). Oxidative stress and inflammation play important roles in the pathophysiological processes in COPD. We examined the hypothesis that daily administration of melatonin (10 mg/kg) mitigates the pulmonary hypertension and vascular remodeling in chronically hypoxic rats. The right ventricular systolic pressure (RVSP) and the thickness of pulmonary arteriolar wall were measured from normoxic control, vehicle- and melatonin-treated hypoxic rats exposed to 10% O₂ for 14 days. Levels of markers for oxidative stress (malondialdhyde) and inflammation (tumor necrosis factor-α (TNFα), inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2)) and the expressions of total endothelial NO synthase (eNOS) and phosphorylated eNOS at serine1177 (ser1177) were determined in the lung tissue. We found that the RVSP and the thickness of the arteriolar wall were significantly increased in the vehicle-treated hypoxic animals with elevated levels of malondialdhyde and mRNA expressions of the inflammatory mediators, when compared with the normoxic control. In addition, the phosphorylated eNOS (ser1177) level was significantly decreased, despite an increased eNOS expression in the vehicle-treated hypoxic group. Melatonin treatment significantly attenuated the levels of RVSP, thickness of the arteriolar wall, oxidative and inflammatory markers in the hypoxic animals with a marked increase in the eNOS phosphorylation in the lung. These results suggest that melatonin attenuates pulmonary hypertension by antagonizing the oxidative injury and restoration of NO production.

The role and potential of imaging in COPD

Chronic obstructive pulmonary disease is a heterogeneous condition of the lungs and body. Techniques in chest imaging and quantitative image analysis provide novel in vivo insight into the disease and potentially examine divergent responses to therapy. This article reviews the strengths and limitations of the leading imaging techniques: computed tomography, magnetic resonance imaging, positron emission tomography, and optical coherence tomography. Following an explanation of the technique, each section details some of the useful information obtained with these examinations. Future clinical care and investigation will likely include some combination of these imaging modalities and more standard assessments of disease severity.

Pulmonary and cardiovascular complications of obesity: an autopsy study of 76 obese subjects

CONTEXT

Obesity is associated with sleep disordered breathing and cardiovascular morbidity, but the relationship between pulmonary hypertension, heart disease, and obesity is unknown.

OBJECTIVE

To determine the prevalence of pulmonary and cardiovascular disease in obese subjects undergoing autopsy at a large medical center.

DESIGN

A search through autopsy records from an 11-year period identified 76 subjects with a body mass index greater than 30 kg/m(2) and 46 age-matched, nonobese controls. Clinical data were collected from medical charts and autopsy records. Formalin-fixed, paraffin-embedded sections of lungs and heart were reviewed for each subject. The presence of pulmonary edema, hemorrhage, diffuse alveolar damage, thrombi, and pulmonary hypertensive changes, including intimal fibrosis, medial hypertrophy, muscularization of arterioles, alveolar capillary hemangiomatosis, hemosiderosis, and iron encrustation were documented. Hearts were examined for the presence of cardiomegaly, ventricular hypertrophy, coronary artery atherosclerosis, acute infarction, fibrosis, and inflammation. Differences between the obese and control groups were compared using a statistical software program.

RESULTS

The obese group demonstrated a greater occurrence of diabetes mellitus, systemic hypertension, pulmonary edema, hemorrhage, and pulmonary hypertensive changes compared with the control group. Alveolar capillary hemangiomatosis was exclusively observed in the obese subjects. Cardiomegaly and left ventricular hypertrophy were present in all obese subjects; approximately one third of the obese subjects had no coronary atherosclerosis.

CONCLUSIONS

Pulmonary hypertensive changes, including venous hypertension and capillary hemangiomatosis, were observed in 72% of obese subjects. Cardiomegaly with biventricular hypertrophy was present in all obese subjects and was suggestive of obesity cardiomyopathy.

Pulmonary Vascular Disease

The pulmonary vasculature is an anatomic compartment that is frequently overlooked in the histologic review of lung biopsy samples, other than those obtained specifically to assess pulmonary vascular disease.1 Though often of a nonspecific nature, the histologic pattern of vascular remodeling may at times suggest its underlying pathogenesis and provide clues to the cause of pulmonary hypertension.2 Disproportionately severe vascular pathology may further indicate alternate disease processes, such as congestive heart failure or thromboemboli, contributing to the patient’s overall respiratory condition.

Burkholderia cepacia is associated with pulmonary hypertension and increased mortality among cystic fibrosis patients

The aim of the study was to evaluate the impact of Burkholderia cepacia on cardiovascular status and mortality in cystic fibrosis. Seven patients infected with B. cepacia were matched with 31 patients not infected with this organism for gender, age, height, weight, genotype, and percent predicted forced expiratory volume in one second, partial arterial oxygen pressure, and pancreatic sufficiency status. The pulmonary artery systolic pressure, as assessed by transthoracic echocardiography, was significantly higher in patients infected with B. cepacia (61.3 +/- 17.2 mm Hg) than in controls (37.3 +/- 13.9 mm Hg; P = 0.02), and the mean acceleration time was significantly lower (77 +/- 33 ms versus 108 +/- 25 ms; P = 0.02). The 6-month mortality was significantly higher in patients infected with B. cepacia (57% versus 16%; P = 0.02). Six of the seven patients infected with B. cepacia harbored the same ribotype (genomovar II, B. multivorans). Pulmonary hypertension was significantly more frequent in patients infected by B. cepacia and could contribute to the increased mortality rate.

Effects of Intermittent Exposure to High Altitude on Pulmonary Hemodynamics: A Prospective Study

Chronic alveolar hypoxia due to disease or low atmospheric pressure at high altitude results in the development of hypoxic pulmonary hypertension. The effects of intermittent hypoxia on pulmonary hemodynamics in healthy men have not been studied. We aimed to investigate, prospectively, pulmonary hemodynamics in workers commuting between an elevation of 3700 and 4200 m (4-week working shift) and lowland, below 500 m (4 weeks of holiday). Pulmonary hemodynamics has been investigated by Doppler echocardiography in 26 healthy Caucasian males, mean age 42 +/- 9 yr. First at lowland (760 m) and next during the fourth week of work at high altitude. Investigations were repeated in 21 subjects 1 year later at the end of the high-altitude exposure. The third series of investigations was performed 2 yr after the initial ones in 10 subjects who earlier had shown the strongest hypoxic vasoconstriction. At lowland, subjects presented with normal pulmonary hemodynamics. At high altitude, mean pulmonary artery pressure (PAPm) rose from 14.7 +/- 2.7 mmHg to 25.8 +/- 8.3 mmHg. One year later the PAPm remained unchanged in hypoxic conditions (25.0 +/- 7.3 mmHg). At the end of a 2-year follow-up of 10 "hyperreactors," PAPm measured at the end of the hypoxic exposure was the same as at the initial investigation, averaging 28 +/- 4.0, 28 +/- 3.5, and 29 +/- 2.5 mmHg at the beginning and at 1 and after 2 yr of intermittent exposure to high altitude. We concluded that intermittent exposure to 4000 m lasting 3 yr does not lead to development of permanent pulmonary hypertension.

Long term effects of non-invasive mechanical ventilation on pulmonary haemodynamics in patients with chronic respiratory failure

BACKGROUND

It is not known whether long term nocturnal mechanical ventilation (NMV) reduces pulmonary hypertension in patients with chronic respiratory failure (CRF).

METHODS

Pulmonary haemodynamics, spirometric values, and gas exchange were studied in 33 patients requiring NMV due to CRF (20 with thoracic restriction, 13 with chronic obstructive pulmonary disease (COPD)) at baseline and after 1 year of NMV given in the volume cycled mode. Patients with COPD also received supplemental oxygen.

RESULTS

Long term NMV improved gas exchange while lung function remained unchanged. Mean pulmonary artery pressure at rest before NMV was higher in patients with thoracic restriction than in those with COPD (33 (10) mm Hgv 25 (6) mm Hg). After 1 year of NMV mean pulmonary artery pressure decreased in patients with thoracic restriction to 25 (6) mm Hg (mean change –8.5 mm Hg (95% CI –12.6 to –4.3), p<0.01) but did not change significantly in patients with COPD (mean change 2.2 mm Hg (95% CI –0.3 to 4.8)).

CONCLUSIONS

Long term NMV in CRF improves pulmonary haemodynamics in patients with thoracic restriction but not in patients with COPD.

Long term effects of non-invasive mechanical ventilation on pulmonary haemodynamics in patients with chronic respiratory failure

BACKGROUND

It is not known whether long term nocturnal mechanical ventilation (NMV) reduces pulmonary hypertension in patients with chronic respiratory failure (CRF).

METHODS

Pulmonary haemodynamics, spirometric values, and gas exchange were studied in 33 patients requiring NMV due to CRF (20 with thoracic restriction, 13 with chronic obstructive pulmonary disease (COPD)) at baseline and after 1 year of NMV given in the volume cycled mode. Patients with COPD also received supplemental oxygen.

RESULTS

Long term NMV improved gas exchange while lung function remained unchanged. Mean pulmonary artery pressure at rest before NMV was higher in patients with thoracic restriction than in those with COPD (33 (10) mm Hg v 25 (6) mm Hg). After 1 year of NMV mean pulmonary artery pressure decreased in patients with thoracic restriction to 25 (6) mm Hg (mean change -8.5 mm Hg (95% CI -12.6 to -4.3), p<0.01) but did not change significantly in patients with COPD (mean change 2.2 mm Hg (95% CI -0.3 to 4.8)).

CONCLUSIONS

Long term NMV in CRF improves pulmonary haemodynamics in patients with thoracic restriction but not in patients with COPD.

Generation of oxidative stress contributes to the development of pulmonary hypertension induced by hypoxia

Chronic hypoxia causes pulmonary hypertension and right ventricular hypertrophy associated with pulmonary vascular remodeling. Because hypoxia might promote generation of oxidative stress in vivo, we hypothesized that oxidative stress may play a role in the hypoxia-induced cardiopulmonary changes and examined the effect of treatment with the antioxidant N-acetylcysteine (NAC) in rats. NAC reduced hypoxia-induced cardiopulmonary alterations at 3 wk of hypoxia. Lung phosphatidylcholine hydroperoxide (PCOOH) increased at days 1 and 7 of the hypoxic exposure, and NAC attenuated the increase in lung PCOOH. Lung xanthine oxidase (XO) activity was elevated from day 1 through day 21, especially during the initial 3 days of the hypoxic exposure. The XO inhibitor allopurinol significantly inhibited the hypoxia-induced increase in lung PCOOH and pulmonary hypertension, and allopurinol treatment only for the initial 3 days also reduced the hypoxia-induced right ventricular hypertrophy and pulmonary vascular thickening. These results suggest that oxidative stress produced by activated XO in the induction phase of hypoxic exposure contributes to the development of chronic hypoxic pulmonary hypertension.

The pathology of smoking-related lung diseases

A broad range of non-neoplastic pulmonary lesions is associated with cigarette smoking including airway diseases with airflow limitation, vascular alterations and interstitial lung diseases characterized by diffuse radiographic abnormalities and restricted lung volumes. This article focuses on the pathology of smoking-related emphysema, alterations of large airways, alterations of pulmonary vessels, respiratory bronchiolitis associated interstitial lung disease (RB-ILD), desquamative interstitial pneumonia (DIP), and eosinophilic granuloma (EG).

Soluble guanylate cyclase gene expression and localization in rat lung after exposure to hypoxia

The nitric oxide (NO)-cGMP signal transduction pathway plays an important role in the regulation of pulmonary vascular tone and resistance in pulmonary hypertension. A number of studies have demonstrated that endothelial (e) and inducible nitric oxide synthases (NOS) are upregulated in hypoxia-exposed rat lung. These changes in NOS expression have been found to correlate with the process of pulmonary vascular remodeling in hypoxia-induced pulmonary hypertension, and remodeling is increased in the absence of eNOS. In this study, we examined the expression and localization of soluble guanylate cyclase (sGC), the primary receptor for NO, in hypoxia- and normoxia-treated rat lungs. Male Sprague-Dawley rats were exposed to hypoxia (10% O(2), normobaric) or normoxia for 1, 3, 5, and 21 days. The lungs were used for Western analysis of sGC protein, sGC enzyme activity, immunohistochemistry using antiserum against sGC alpha(1)- and beta(1)-subunits, and nonradioactive in situ hybridization (NRISH) using a digoxigenin-labeled sGC alpha(1)-subunit cRNA probe. Western blot analysis revealed a more than twofold increase of sGC protein alpha(1)-subunit in rat lungs exposed to 3, 5, and 21 days of hypoxia, correlating well with sGC enzyme activity. Immunohistochemistry and NRISH demonstrated increased expression of sGC in the smooth muscle cells of the pulmonary arteries and arterioles in the hypoxic rat lungs when compared with normoxic controls. Based on our results, the upregulation of sGC may play an important role in the regulation of smooth muscle tone and pressure in the pulmonary circulation during chronic hypoxia.

Effects of long-term oxygen therapy on pulmonary hemodynamics in COPD patients: a 6-year prospective study

OBJECTIVE

To investigate effects of 6 years of domiciliary oxygen therapy on pulmonary hemodynamics in a large group of COPD patients.

DESIGN

Prospective longitudinal study with serial measurements.

SETTING

Research institute of pulmonary diseases.

PATIENTS

Ninety-five patients (72 men, 23 women), mean age 58+/-9 years, had COPD but were free of any other serious disease. Functional characteristics at entry, mean+/-SD, were as follows: FVC=2.24+/-0.51 L; FEV1=0.84+/-0.31 L; PaO2=55+/-6 mm Hg; PaCO2=48+/-9 mm Hg; mean pulmonary arterial pressure (PAP)=28+/-11 mm Hg; and pulmonary vascular resistance (PVR)=353+/-172 dynexsxcm(-5).

METHODS

Pulmonary hemodynamics were investigated using Swan-Ganz thermodilution catheters. After initial assessment, all patients were started on a regimen of long-term oxygen therapy (LTOT). Follow-up consisted of medical examination, spirometry, and arterial blood gas analysis every 3 months. Pulmonary artery catheterization was repeated every 2 years.

RESULTS

Seventy-three subjects survived 2 years of LTOT. In 39 subjects catheterized after 2 years, PAP fell from 25+/-8 to 23+/-6 mm Hg (not significant [NS]). From 31 patients who completed 4 years of LTOT, hemodynamic data were obtained in 20. In these 20 patients, PAP averaged 24+/-7 mm Hg at entry, and 23+/-5 and 26+/-6 mm Hg after 2 and 4 years, respectively (NS). In 12 patients who completed 6 years of LTOT, PAP was 25+/-7 at entry, and 21+/-4, 26+/-7, and 26+/-6 mm Hg at 2, 4, and 6 years, respectively (p < 0.01 for 2 vs 6 years). PVR was 313+/-159 dynexsxcm(-5) at entry, and 268+/-110, 344+/-82, and 332+/-205 dynexsxcm(-5) at 2, 4, and 6 years, respectively (NS). During 6 years of follow-up, PaO2 decreased from 61+/-3 to 46+/-9 mm Hg (p < 0.001) and PaCO2 increased from 44+/-13 to 49+/-9 mm Hg (p < 0.01).

CONCLUSION

LTOT for 14 to 15 h/d resulted in a small reduction in pulmonary hypertension after the first 2 years followed by a return to initial values and subsequent stabilization of PAP over 6 years. The long-term stabilization of pulmonary hypertension occurred despite progression of the airflow limitation and of hypoxemia.

Cardiopulmonary pathology in patients with sleep apnea/obesity hypoventilation syndrome

We reviewed clinical data, autopsy reports, and microscopic slides on 10 patients with sleep apnea/obesity hypoventilation syndrome (SA/OHS) to define the cardiopulmonary pathological features and establish clinicopathologic correlations. Ten obese (>136 kg) patients without SA/OHS were studied as controls. Patients with SA/OHS exhibited biventricular cardiac failure and pulmonary hypertension with a higher prevalence of moderate/severe pulmonary hemosiderosis (8 v 0 patients), alveolar hemorrhage (7 v 4 patients), capillary proliferation (4 v 0 patients), iron encrustation of elastica (1 v 0 patients) and medial hypertrophy of muscular pulmonary arteries (11.9 +/- 2.4 v 9.7 +/- 1.6%) (P < .05). In two patients capillary proliferation resembled capillary hemangiomatosis. Mean right ventricular thickness was higher in the SA/OHS group (0.71 +/- 0.17 v 0.42 +/- 0.1 cm) (P < .01). Four patients with SA/OHS and three controls had moderate/severe myocardial fibrosis. Biventricular cardiac failure caused death in seven patients with SA/OHS. Hypoxia is probably the most important cause of pulmonary hypertension, arterial muscularization, and right ventricular hypertrophy in SA/ OHS. Left ventricular failure in some SA/OHS patients may be the result of hypertensive cardiac disease. In others, the etiology of left ventricular failure was not determined morphologically, suggesting functional abnormalities related to obesity and/or apneic episodes.

Perivascular fibrosis of muscular pulmonary arteries in chronic obstructive pulmonary disease

We performed a morphometric analysis of peribronchiolar and perivascular fibrosis in lungs obtained at autopsy from six patients with chronic bronchitis, six with pulmonary emphysema, and four normal control subjects. The areas of fibrosis outside the smooth muscle layer of bronchioles and outside the external elastic lamina of muscular pulmonary arteries were measured and their thickness was then calculated by assuming a round airway or artery. Patients with chronic bronchitis had significantly thicker peribronchiolar fibrosis in bronchioles of 1 mm or less in diameter and also thicker perivascular fibrosis of the adjacent muscular pulmonary arteries than the other two groups. The extent of perivascular fibrosis was significantly correlated with peribronchiolar fibrosis only in the muscular pulmonary arteries adjacent to the bronchioles but not in those away from the bronchioles. These findings suggest direct extension of chronic inflammation from bronchioles to the adjacent muscular pulmonary arteries in chronic bronchitis but not in pulmonary emphysema. Such perivascular fibrosis might lead to sustained pulmonary hypertension.

Short- and long-term hemodynamic effects of oral nifedipine in patients with pulmonary hypertension secondary to COPD and lung fibrosis. Deleterious effects in patients with restrictive disease

STUDY OBJECTIVE

The present study was undertaken to evaluate at rest the short- and long-term effects of oral nifedipine (N) in patients with pulmonary hypertension (PH).

DESIGN AND SETTING

A prospective study with ten consecutive cases during two years in a setting of a district acute hospital.

PATIENTS OR PARTICIPANTS

Seven patients with advanced COPD and three with severe lung fibrosis (LF) during a period of stable condition. Three patients with COPD were eligible for the long-term investigation.

INTERVENTIONS

Right heart catheterization with a 7F Swan-Ganz triple-lumen thermodilution catheter and radial cannulation with a 3F arterial catheter.

MEASUREMENTS AND RESULTS

Measurement of CO, MAP, RAP, PAP, PWP, HR, and ABG and calculation of CI, TSR, PAR, and DO2 before and after 20 mg of N sublingually at rest. For the group as a whole, N induced a reduction in MAP and TSR, with a significant increase in CI and DO2. There were no significant changes in PAP, PAR (magnitude of the reduction: -10 percent), HR, and PaO2. The individual analysis of the driving pressures (PAP-PWP) in function of the cardiac output demonstrated that a real vasodilating effect in the pulmonary circulation occurred in only three COPD patients (magnitude of the PAR reduction: -43 percent), while in the three patients with LF, N induced a deleterious increase in PAP and PAR. After long-term treatment (10 mg of N daily every 4 h; average 12 months) in the former, despite a persistent beneficial hemodynamic effect (magnitude of the PAR reduction: -36 percent), there was the usually expected clinical worsening.

CONCLUSIONS

N in small doses may be able in some patients with severe COPD to induce a beneficial short- and long-term hemodynamic effect on the pulmonary circulation when PH is present. On the other hand, N should not be used in patients with PH and advanced LF.

Vascular invasion in non-small cell lung carcinoma

AIMS

To determine if there is any correlation between vascular invasion and prognosis in non-small cell carcinoma of the lung; and to look specifically at invasion of vascular channels by tumour cells.

METHODS

Eighty seven patients undergoing lobectomy or pneumonectomy for adenocarcinoma or squamous carcinoma were followed up for five years. The histological sections were studied for evidence of vascular invasion using an elastic van Gieson stain. The incidence of intimal fibrosis in arteries and veins was noted and the proportion with vascular invasion evaluated using a scoring system. The presence or absence of lymphatic permeation and tumour necrosis were noted. Survival data were analysed using the log rank test.

RESULTS

The overall five year survival was 32%. There were 64 squamous cell carcinomas and 23 adenocarcinomas. Vascular invasion was seen in 77% of patients and lymphatic invasion in 44%. Neither the presence nor absence nor the proportion of blood vessels showing vascular invasion showed any relation to prognosis. Intimal fibrosis and tumour necrosis were unrelated to prognosis. Patients with lymphatic permeation had recurrence and died earlier than those without.

CONCLUSION

The presence of arterial or venous invasion by adenocarcinoma or squamous carcinoma of the lung was unrelated to survival; lymphatic permeation was associated with poor prognosis. The two common non-small cell lung cancers behaved differently from other solid tumours, where vascular invasion was a significant factor in determination of prognosis. The presence of intimal fibrosis was unrelated to prognosis.

Red cell size and various lung arterial measurements in different strains of domestic fowl

Red cell size and various lung arterial measurements were examined in different strains of young commercial broiler and layer fowls. The broilers were: Marshall, Cobb, Ross 'selected', Ross 'relaxed' and the layers were: Isa Brown, Ross Brown and Hisex Brown. The Ross relaxed bird had a significantly larger red cell than any other strain. Overall, broilers had larger red cells than layers. The internal elastic lamina, a measure of arterial size, was small in the Ross relaxed bird (138 microns) and was at its maximum (163 microns) in the selected Ross strain. The medial area (muscle coat) was least in the Ross relaxed bird (984 microns2) and greatest in the Cobb strain (1516 microns2). In some strains there was a slight correlation among birds between red cell and arterial size but not with the medial area. The results appeared to indicate that red cell size may not be the only important correlating factor in the aetiology of pulmonary hypertension in fowls.

Tissue arrangement in the internal elastic lamina of the rat muscular pulmonary artery

The arrangement of tissue in the internal elastic lamina of muscular pulmonary arteries in rats has been studied. It consists of long plates of elastic tissue joined to each other by side branches, thus forming a continuous branching network. The thick plates are orientated parallel to the long axis of the vessel. This is similar to the arrangement in the saphenous and splenic veins in the dog. Systemic arteries show a different arrangement, usually a single fenestrated sheet. The differences between systemic and pulmonary arteries can be explained by considering the different biomechanical forces acting on them.

Pulmonary veno-occlusive disease. A report of four cases

Four cases of pulmonary veno-occlusive disease are described. Two patients, who were brothers, had respiratory tract infections. The third patient had chronic active hepatitis and coeliac disease suggesting an abnormality of the immune system; the fourth patient had no obvious cause but presented initially with systemic hypertension. Three of the cases had been diagnosed initially as primary pulmonary hypertension either on open lung biopsy or clinically. In all cases the pulmonary arteries were abnormal with medial hypertrophy, intimal fibrosis and, in some cases, thrombosis in elastic pulmonary arteries. These findings suggest that pulmonary veno-occlusive disease is not confined to veins and should be considered as a widespread pulmonary vascular disease. The range of aetiological factors indicate that it should not be considered as a single disease entity.

Method for maximising measurements of muscular pulmonary arteries

Using a digitiser for assessing the media and intima of muscular pulmonary arteries, we have previously shown that the most sensible measurements are those of medial and intimal area and that artery size should be defined in terms of the total length of internal elastic lamina. These measurements do not vary with the collapse or constriction of the artery. A cross sectional cut and a well defined internal elastic lamina are essential for measurement using our technique. This study explores methods for obtaining the above three measurements for cross sectionally cut arteries with an ill defined internal elastic lamina, with a view to increasing the number of arteries measured. The methods were tested on three subjects, using arteries for which the true values of the three variables were known. Acceptable estimates of medial and intimal area could be obtained by simply delineating the boundaries of the intima and media and ignoring the crinkles in the elastic laminae. It was also found that muscular pulmonary arteries may not be uniformly collapsed or constricted round the circumference of their walls and that the overall degree of collapse or constriction seemed to be affected by the size of the artery. An acceptable estimate of the total length of an internal elastic lamina was most readily obtained by multiplying the length of the boundary between intima and media by a crinkle factor based on an optical assessment of the amount of crinkling in that internal elastic lamina.

Use of calcium channel blockers in hypoxic lung disease

COPD patients who are hypoxic develop pulmonary hypertension primarily because alveolar hypoxia induces muscular hypertrophy of pulmonary arteries. This muscular hypertrophy will regress in animals if they receive continuous oxygen therapy. Since many COPD patients refuse to use oxygen continuously, calcium channel blockers, which inhibit hypoxic pulmonary vasoconstriction, may be effective adjuvant therapy. Nifedipine lowers pulmonary vascular resistance during rest and exercise in hypoxic COPD patients.

Vascular changes in radiation bowel disease

A series of 20 cases of radiation bowel disease (RBD) was studied qualitatively and the arterial changes were studied quantitatively. A control series of 45 cases was studied. In the control cases there were positive correlations between the medial thickness of all vessels studied and the diastolic blood pressure as well as the incidence of intimal fibrosis in both intramural and extramural arteries. The medial thickness in all the arteries in cases of RBD was significantly higher than in the controls. This was probably due to the large number of fibrin thrombi which increased the vascular resistance. The degree of intimal fibrosis of the intramural arteries and arterioles was significantly greater than in the controls. Similarly the incidence of intimal fibrosis in all arterioles and intramural arteries was greater than the control group. The degree of intimal fibrosis was related to the dose of radiation received. The effect of radiation was an on-going process since the percentage of arterioles with intimal fibrosis increased with the time after radiotherapy. Blood pressure and age played no part in these correlations in RBD. The most consistently observed qualitative changes in RBD were in the arteries, arterioles and to a lesser extent the veins. These showed fibrin thrombi, fibrinoid necrosis, subendothelial oedema and fibrin. Various stages of healing were seen in the vessels. We believe that the blood vessels are the main site of injury in RBD and that the endothelial cell is the initial target for radiation damage.

Calcium channel blockers in hypoxic pulmonary hypertension

Hypoxia is the major cause of pulmonary hypertension and right ventricular hypertrophy in chronic obstructive pulmonary disease, cystic fibrosis, kyphoscoliosis, chronic mountain sickness, and the obesity-hypoventilation and sleep apnea syndromes. Pulmonary hypertension develops in these patients because the long-standing vasoconstriction produced by hypoxia causes muscular hypertrophy of the pulmonary arteries and arterioles. These pathologic changes may regress if alveolar hypoxia is corrected and hypoxic pulmonary vasoconstriction is continuously inhibited. Intermittent inhibition of hypoxic pulmonary vasoconstriction does not reverse these pathologic changes. Since patient noncompliance with oxygen therapy makes it difficult to achieve continual relief of alveolar hypoxia, a drug that inhibits hypoxic vasoconstriction may be useful. Experimental findings indicate that hypoxic pulmonary vasoconstriction requires calcium influx and can be inhibited by certain slow-channel calcium blockers. Studies also demonstrate that slow-channel calcium antagonists can attenuate the pulmonary hypertension and right ventricular hypertrophy produced in rats by chronic hypoxia. Recently, two studies have shown that nifedipine inhibits hypoxic pulmonary vasoconstriction in patients with chronic obstructive pulmonary disease. If further studies demonstrate that these short-term effects are sustained, certain slow-channel calcium blockers may become a useful adjuvant to low-flow oxygen therapy in the treatment of hypoxic pulmonary hypertension.

Histometrical investigation of the pulmonary artery in severe hepatic disease

Histological changes of the pulmonary vasculature in comparison with that of the portal vein in necropsy cases of severe hepatic injury that had not been associated with clinical pulmonary hypertension were analysed qualitatively and quantitatively. The main changes of the intra-hepatic portal vein were dilatation (88.3 per cent), thickening of the wall (58.5 per cent) and thrombi (22.3 per cent). The changes of the pulmonary vasculature were limited to muscular type arteries, which showed dilatation (31.9 per cent), thickening of the wall (30.9 per cent) and thrombi (10.6 per cent). Association of wall thickening of the portal vein and the small pulmonary artery was observed in 30.9 per cent, these associations being statistically significant. Coincidence of thrombus formation in the portal vein and pulmonary vasculature was observed only in 4.3 per cent, which was not statistically significant. After the circumferences of the internal and external elastic laminae of small pulmonary arteries and the cross-sectional area of the media were measured, the anatomical radius and wall thickness of each artery were calculated according to Furuyama 's method. The relations between the anatomical radii and wall thickness of small pulmonary arteries in controls and hepatic cirrhosis groups were investigated by analysis of covariance to compare the equality of the two corresponding regression lines. The wall thickness and the ratio of wall thickness to the anatomical radius of small pulmonary arteries were significantly larger in the cirrhotic group than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Longitudinal smooth muscle in pulmonary arteries. Occurrence in congenital heart disease

In lung biopsy specimens of 19 patients with congenital heart disease and pulmonary hypertension, in addition to the common features of plexogenic arteriopathy, longitudinal smooth muscle cells were found in small pulmonary arteries. These cells were arranged in bundles or layers, particularly in the intima but sometimes within the media or adventitia of the arteries. They often caused severe narrowing of the lumen. Corrective surgery of the cardiac defect was performed in 14 patients. The results suggested that even when these changes are wide-spread and severe, they do not stand in the way of a favourable post-operative course. In one patient who underwent a banding procedure of the pulmonary artery, virtually complete regression of the smooth muscle layers could be demonstrated in a second biopsy, taken 5 years later during a corrective operation.

Adult respiratory distress syndrome--a review

Adult respiratory distress syndrome (ARDS) represents a common pathway of damage to the lungs by a wide variety of different agents. The important aetiological factors and mechanisms of lung injury are considered. Electron microscopic features as well as light microscopy are described. Factors that may modify the pathological picture are discussed. Probably the most important of these is oxygen. This gas is said to produce interstitial pulmonary fibrosis but this concept is once again questioned.

Pulmonary veins in high-altitude residents: a morphometric study

The thickness of the media of pulmonary veins and arteries was morphometrically assessed in 12 normal adults resident at altitudes over 3000 m and 12 resident at sea level. The pulmonary veins in the latter group were very thin walled. The average thickness of the pulmonary venous media in the group of highlanders was significantly thicker but this appeared to be due to prominent medial hypertrophy in seven individuals, five others having normal or near-normal pulmonary veins. In six of the 12 highlanders bundles of longitudinal smooth muscle cells occurred in the venous intima. There was close correlation between the thickness of the venous and that of the arterial media, suggesting an individual reactivity with a simultaneous response of all pulmonary vascular smooth muscle to high-altitude hypoxia. Hypertrophy of the media of pulmonary veins is likely to be an expression of venoconstriction and narrowing of the venous lumen may be enhanced by the development of longitudinal smooth muscle cells in the intima. Possibly venoconstriction is one of the factors responsible for high-altitude pulmonary oedema.

Small pulmonary arteries in some natives of La Paz, Bolivia

A histological study was made of the small pulmonary blood vessels in pieces of lung obtained at necropsy from 19 long-term residents of La Paz, Bolivia (3800 m). There was variation in the response of the pulmonary vasculature of these subjects to the chronic hypoxia of high altitude. The most characteristic finding, seen in seven of the 16 cases beyond infancy, was distal extension of vascular smooth muscle into pulmonary arterioles as small as 20 micrometer in diameter. Medial hypertrophy of the muscular pulmonary arteries occurred in only three of these seven subjects. Intimal fibrosis was seen in eight of the 19 cases and was ascribed to age; such fibrotic proliferation may affect the reversibility of hypoxic pulmonary hypertension and associated vascular changes in highlanders.

Intermittent high altitude hypoxia

The effect of intermittent high altitude (IHA) hypoxia on the myocardium and lesser circulation was investigated in adult male Wistar rats. IHA can induce intermittent pulmonary hypertension and right ventricular hypertrophy in a relatively short time. Even marked pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular changes can be normalized when rats are removed from the hypoxic atmosphere. At the beginning of the exposure to IHA acute myocardial necrotic changes were found; prolongation of IHA did not lead to further acute lesions. Experimentally induced CO polycythemia leads to mild pulmonary hypertension; IHA-induced pulmonary hypertension may, thus, be partly due to polycythemia. Beta blocking agents are able to decrease chronic hypoxic pulmonary hypertension, hypertensive changes in the pulmonary circulation, the degree of right ventricular hypertrophy, and necrotic myocardial changes.

The effect of acute and chronic hypoxia on thoracic gas volume in anaesthetized rats

1. Thoracic gas volume at end expiration (functional residual capacity, FRC) was measured in chronically and acutely hypoxic anaesthetized rats by a plethysmograph method. 2. FRC, measured during air breathing, was 34-62% larger in rats which had been kept in an environmental chamber in 8, 10 or 12% O2 for 3 weeks than in littermate controls. FRC returned to normal after the rats had returned to air for 9 days. There was no constant difference in the pattern of breathing between control and chronically hypoxic rats. 3. Pressure-volume curves measured post mortem showed no difference in the volume of the lung at 25 cm H2O pressure or in the compliance of the lung between chronically hypoxic and control rats. Thus there was no gross mechanical change in the lung to account for the increase in FRC. 4. Acute hypoxia caused by breathing 12% O2 increased FRC in control but not in chronically hypoxic rats. The increase in FRC in control rats was abolished by combined blockade of the vagus nerves and carotid bodies (with procaine) but not by vagal blockade alone. 5. The combined vagal and carotid body blockade reduced FRC significantly in rats which had been in 10% O2 for 3 days but not in those which had been in 10% O2 for 21 days. 6. Lung area measured from radiographs was not reduced by a muscle relaxant in chronically hypoxic rats. Electromyograms from anterior intercostal muscles and the diaphragm showed no electrical activity in expiration in chronically hypoxic rats which might indicate an active muscular basis for their increased FRC. However when FRC was raised by acute hypoxia in control animals there was also no increase in electrical activity in expiration which could have explained their increase in lung volume. 7. We concluded that the increase in FRC during acute hypoxia in control rats was probably due to a reflex from the carotid body. The increase in FRC in chronically hypoxic rats, which was present while they breathed air, may have had an active muscular component in the early stages but later on there was possibly a structural factor in the chest wall.

Evagination of smooth muscle cells in the hypoxic pulmonary trunk

Six female Wistar albino rats were exposed to the hypoxia of a simulated altitude of 5500 m, three for a period of one week and three for a month. They developed ultrastructural changes in the pulmonary trunk consisting of evaginations of muscle cells of its media through gaps in the internal elastic lamina to press into the underlying endothelial cells. Such evaginations were usually devoid of myofilaments and organelles. Some appeared so electron-lucent as to be unrecognisable as muscle apart from the unequivocal connection with the parent smooth muscle cells. Elsewhere we have demonstrated that muscular evaginations in normal pulmonary blood vessels are an artefact brought about by collapse of lung tissue and that they can be avoided by distending the lung. Hence in the present investigation, in which the pulmonary trunk was fixed in distension, the evaginations are interpreted as indicating contraction of the muscle cells able to overcome the distending force. We interpret them as evidence of constriction of muscle cells in the media of the pulmonary trunk in response to hypoxia.

A study of pulmonary artery pressure, electrocardiography, and mechanocardiography in thoracic scoliosis

Cardiac catheterisation was carried out in 40 patients with thoracic scoliosis in order to measure the pulmonary artery pressure. Statistical correlations were calculated between these results and the electrocardiographic and mechanocardiographic findings determined on a separate occasion. The pulmonary artery pressure was normal in 72% of subjects. It was inversely correlated with arterial oxygen tension but not with the aetiology, severity, or age at onset of the scoliosis. The accuracy of electrocardiography and mechanocardiography in predicting the pulmonary artery pressure was assessed. The closet correlates were found to be a tall P wave in lead II or III and a prolonged interval between pulmonary valve closure and tricuspid valve opening.