Cardiovascular-pulmonary interaction in chronic obstructive pulmonary disease with special reference to the pathogenesis and management of cor pulmonale

Deep learning to predict elevated pulmonary artery pressure in patients with suspected pulmonary hypertension using standard chest X ray

Accurate diagnosis of pulmonary hypertension (PH) is crucial to ensure that patients receive timely treatment. We hypothesized that application of artificial intelligence (AI) to the chest X-ray (CXR) could identify elevated pulmonary artery pressure (PAP) and stratify the risk of heart failure hospitalization with PH. We retrospectively enrolled a total of 900 consecutive patients with suspected PH. We trained a convolutional neural network to identify patients with elevated PAP (> 20 mmHg) as the actual value of PAP. The endpoints in this study were admission or occurrence of heart failure with elevated PAP. In an independent evaluation set for detection of elevated PAP, the area under curve (AUC) by the AI algorithm was significantly higher than the AUC by measurements of CXR images and human observers (0.71 vs. 0.60 and vs. 0.63, all p < 0.05). In patients with AI predicted PH had 2-times the risk of heart failure with PH compared with those without AI predicted PH. This preliminary work suggests that applying AI to the CXR in high risk groups has limited performance when used alone in identifying elevated PAP. We believe that this report can serve as an impetus for a future large study.

[Alveolar epithelial cell injury as an etiopathogenic factor in pulmonary fibrosis]

Idiopathic pulmonary fibrosis (IPF) is characterized by a progressive accumulation of extracellular matrix and an imbalance between profibrotic and antifibrotic mediators. In the last few years, understanding of the mechanisms of the biology of IPF has increased. One of the most significant discoveries is the finding that alveolar epithelial cell injury plays an important role in the pathogenesis of this disease. In this review, we describe some of the mechanisms involved in alveolar cell injury and their contribution to the development of IPF.

Real-time MR imaging of aortic flow: influence of breathing on left ventricular stroke volume in chronic obstructive pulmonary disease

PURPOSE

To assess real-time changes of left ventricular stroke volume (SV) in relation to the breathing pattern in healthy subjects and in patients with chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

Real-time magnetic resonance (MR) imaging flow measurements were performed in the ascending aorta of 10 healthy volunteers and nine patients with severe COPD. Breathing maneuvers were registered with an abdominal pressure belt, which was synchronized to the electrocardiographic signal and the flow measurement. Healthy subjects performed normal breathing, deep breathing, and the Valsalva maneuver. Patients with COPD performed spontaneous breathing. Paired two-tailed Student t tests were used in healthy volunteers to assess significant SV differences between normal breathing and deep breathing or the Valsalva maneuver. The results of measurements in the patients with COPD were compared with the results during normal breathing in healthy subjects with the unpaired two-tailed Student t test.

RESULTS

In healthy subjects, SV decreased during inspiration and increased during expiration (r2 = 0.78, P <.05). When compared with the SV during normal breathing, mean SV did not change during deep breathing but declined during the Valsalva maneuver (P <.05). The difference between minimal and maximal SVs (ie, SV range) increased because of deep breathing or the Valsalva maneuver (P <.05). In normal and deep breathing, velocity of SV elevation and velocity of SV decrease were equal (which resulted in a ratio of 1), whereas during the Valsalva maneuver, this value increased (P <.05). Spontaneous breathing in COPD resulted in SV changes (P <.05) similar to those observed in healthy subjects who performed the Valsalva maneuver.

CONCLUSION

Real-time MR imaging of aortic flow reveals physiologic flow alterations, which are dependent on variations in the breathing pattern.

Effect of medroxyprogesterone on pulmonary arterial pressure, exhaled nitric oxide, ECG and arterial blood gases

OBJECTIVES

To evaluate the effect of medroxyprogesterone acetate (MPA) therapy on pulmonary arterial pressure (PAP), exhaled nitric oxide (NO), electrocardiogram (ECG), and on arterial blood gases (ABG).

DESIGN

A double-blind randomized placebo-controlled cross-over trial.

SETTING

University hospital in Turku, Finland.

SUBJECTS

Fourteen postmenopausal women with respiratory impairment.

INTERVENTIONS

A 2-week placebo and a 2-week MPA period (60 mg day -1) followed by 6-week placebo or MPA washout periods.

MAIN OUTCOME MEASURES

The systolic PAP was estimated by Doppler echocardiography. PAP, ECG, NO and ABG were monitored at baseline, after 2-week placebo and MPA periods, and after 3- and 6-week placebo and MPA washout periods.

RESULTS

The mean PaCO2 at baseline was 5.4 +/- 0.6 kPa (mean +/- SD). The average decrease of PaCO2 on MPA was -0.8 +/- 0.3 kPa (P < 0.001) and 0.3 +/- 1.0 kPa (P = 0.007) at the 3-week washout. The mean systolic PAP at baseline was 44.3 +/- 14.5 mm Hg. MPA did not change PAP until the 6-week washout, when the average increase of + 6.9 +/- 19.8 mm Hg (P = 0.002) was observed. No changes occurred in PaO2, exhaled NO or the ECG axes. The PR interval was shorter only on MPA (15.9 +/- 27.0 ms, P = 0.020) whereas the QRS duration remained shorter up to 3-week washout (3.9 +/0 5.5 ms, P = 0.008 and 4.0 +/- 14.3 ms, P = 0.032). The systolic and diastolic BP and the heart rate did not change.

CONCLUSIONS

Despite prolonged decrease in PaCO2, short-term MPA had no effect on exhaled NO and did not decrease systolic PAP in postmenopausal women with respiratory impairment. MPA shortened the PR interval and the QRS duration, the latter effect being sustained at least up to 3 weeks.

Pulmonary artery remodeling modifies pulmonary hypertension during exercise in severe emphysema

To clarify the relation between the vessel remodeling and the physiology of pulmonary circulation in chronic obstructive pulmonary disease (COPD), we studied the pulmonary hemodynamics at rest and during exercise (25W) and the morphology of pulmonary arteries with external diameters of 100-200 microm in ten patients with severe emphysema. The wall thickness (WT) was defined as the intima plus media. The percent WT of the external diameter (% WT) in emphysema (36.0 +/- 4.3%) was significantly increased compared with that (22.6 +/- 3.3%) in five control lungs. The % WT was not related to pulmonary arterial pressure (Ppa) at rest, but was highly correlated with exercise Ppa (r = 0.721, P = 0.02) and with deltaPpa (Ppa during exercise-Ppa at rest) (r = 0.899, P = 0.0004). These findings suggest that pulmonary artery remodeling leads to reduced recruitability and distensibility of pulmonary vessels and is closely related to exercise pulmonary hypertension.

Effects of lung volume reduction surgery on exercise pulmonary hemodynamics in severe emphysema

STUDY OBJECTIVES

To clarify the effects of lung volume reduction surgery (LVRS) on pulmonary hemodynamics in severe emphysema and to evaluate the role of pulmonary circulation in the increased exercise performance after LVRS.

DESIGN

In eight male patients with severe emphysema, we measured pulmonary artery (Ppa) and occlusion (Pop) pressures and cardiac output through a Swan-Ganz thermodilution catheter, and we calculated cardiac index (CI), pulmonary vascular resistance index, and driving pressure. The study was performed at rest and during exercise using a supine bicycle ergometer at 25 W, under room air and O2 inhalation. Exercise performance was expressed as endurance time in minutes. Pulmonary function tests were performed. The patients underwent an identical study before and 6 months after LVRS.

RESULTS

The patients' exercise performance was significantly increased after LVRS (5.9+/-1.8 min) compared with that before LVRS (3.6+/-0.9 min). LVRS resulted in a significant increase in FEV1 and a significant decrease in residual volume. Before LVRS, Ppa was increased both at rest and during exercise. LVRS did not change rest or exercise Ppa. LVRS significantly decreased Pop during exercise from 24+/-10 mm Hg to 18+/-7 mm Hg. CI at rest and during exercise were significantly increased after LVRS. O2 administration significantly decreased Ppa during exercise both before and after LVRS.

CONCLUSIONS

These findings suggest that LVRS does not improve pulmonary hypertension at rest or during exercise in patients with severe emphysema and that elevated Pop during exercise before LVRS is probably related to lung mechanic abnormalities.

Substantial changes in arterial blood gases during thoracoscopic surgery can be missed by conventional intermittent laboratory blood gas analyses

Substantial and clinically relevant changes in arterial blood gases are likely to occur during thoracoscopic surgery with one-lung ventilation (OLV). We hypothesized that they may be missed when using the conventional intermittent blood gas sampling practice. Therefore, during 30 thoracoscopic procedures with OLV, the sampling intervals between consecutive intermittent laboratory blood gas analyses (BGA) were evaluated with respect to changes of PaO2, PaCO2, and pHa ([H+]) using a continuous intraarterial blood gas monitoring system. Frequency and timing of BGA were based on the clinical judgment of 16 experienced anesthesiologists who were blinded to the continuously measured values. Extreme fluctuations of PaO2 (37-625 mm Hg), PaCO2 (27-56 mm Hg), and pHa (7.24-7.51) were observed by continuous blood gas monitoring. During 63% of all sampling intervals, PaO2 decreased >20% compared with the preceding BGA value, which remained undetected by intermittent analysis. In 10 patients with a continuously measured minimal PaO2 value < or = 60 mm Hg, the preceding BGA overestimated this minimal PaO2 by > 47%. Correspondingly, PaCO2 increases of > 10% were observed in 35% of all sampling intervals, and [H+] increases of > 10% were observed in 24% of all sampling intervals. Because these blood gas changes were not reliably detected by using noninvasive monitoring and their magnitude is not predictable during OLV, intermittent BGA with short sampling intervals is warranted. In critical cases, continuous blood gas monitoring may be helpful.

IMPLICATIONS

The magnitude of blood gas changes during thoracoscopic surgery with one-lung ventilation is not predictable and not reliably detected by noninvasive monitoring. Using a continuous intraarterial blood gas monitoring device, we demonstrated that intermittent laboratory blood gas analysis with short sampling intervals is warranted to detect arterial hypoxemia.

The effect of right ventricular hypertrophy on left ventricular ejection fraction in pulmonary emphysema

STUDY OBJECTIVE

The development of right ventricular (RV) hypertrophy in emphysema is accompanied by involvement of the left ventricle (LV) and its systolic function. Our objective was to study the relation between RV hypertrophy and LV ejection fraction in emphysema by means of MRI.

PATIENTS

Ten emphysematous patients (FEV1, 0.99+/-0.32 L; FEV1/vital capacity (VC), 0.32+/-0.11 [mean+/-SD]) and 10 age-matched control subjects were included. Exclusion criteria were any history of systemic hypertension, ischemic or valvular heart disease, or episodes of right- and/or left-sided cardiac failure.

MEASUREMENTS AND RESULTS

Rapid scout imaging was used to measure RV and LV wall mass, wall thickness, and end-diastolic volume. Stroke volume was derived from the main pulmonary artery flow. RV wall volume, RV wall thickness, and the ratio of RV to LV wall thickness were significantly larger in the patient group than in the control group (p<0.01). Furthermore, patients had significantly lower values of LV ejection fraction (p<0.01) than the control subjects. A flattening or leftward displacement of the ventricular septum during systole was observed. In addition, our study showed an increase of LV ejection fraction proportional with the RV wall thickness (r=0.78, p<0.01) in severely emphysematous patients.

CONCLUSION

These data are in support of the hypothesis that flattening of the interventricular septum explains the relatively normal LV ejection fraction in emphysematous patients with severe RV hypertrophy.

Anesthetic management of patients undergoing unilateral video-assisted lung reduction for treatment of end-stage emphysema

OBJECTIVES

Nonanatomic resection of peripheral areas of lung is being performed via sternotomy for the treatment of end-stage emphysema. Recent technologic advances have allowed the resection of lung tissue using video-assisted thoracic surgery (VATS) techniques. The study was performed to document the physiologic changes that occur during unilateral VATS lung reduction in hopes of determining appropriate monitoring and intraoperative management strategies.

DESIGN

Prospective trial of unilateral VATS lung reduction.

SETTING

Tertiary care university hospital.

PARTICIPANTS

Twenty patients with end-stage emphysema.

INTERVENTIONS

Participants underwent unilateral VATS lung reduction.

MEASUREMENTS AND MAIN RESULTS

Invasive hemodynamic monitoring was performed using radial and pulmonary artery catheters. Hemodynamic and respiratory gas exchange data were collected at four intraoperative points: (1) supine, two-lung ventilation; (2) lateral decubitus, two-lung ventilation; (3) lateral decubitus, one-lung ventilation, and (4) end of surgery, supine, two-lung ventilation. Data were compared with that collected at the first point. Patients tolerated lengthy surgical procedures and remained hemodynamically stable with no episodes of hypoxemia requiring treatment. Extubation was tolerated by 19 of 20 patients at the conclusion of surgery without further requirement of mechanical ventilation.

CONCLUSIONS

VATS lung reduction under general anesthesia with one-lung ventilation is well tolerated. Permissive hypercapnia was well tolerated by all patients. Early extubation can be routinely accomplished in these patients.

Neutral endopeptidase inhibitors and the pulmonary circulation

1. Neutral endopeptidase (NEP) EC 3.4.24.11 is a zinc-metallopeptidase which is partly responsible for the degradation of atrial natriuretic peptide (ANP) in vivo. 2. ANP inhibits vascular smooth muscle cell proliferation, and elicits vasorelaxation of the systemic and, more potently, the pulmonary vasculature. Plasma ANP levels are elevated in human disease states characterized by pulmonary hypertension, and in animal models of these diseases. 3. However, the short in vivo half-life of ANP suggests that it has limited therapeutic potential. Therefore, it has been hypothesized that inhibition of the metabolism of ANP may prove successful in the treatment of pulmonary hypertension. 4. Several inhibitors of NEP have been shown to reduce the development of pulmonary hypertension secondary to chronic hypoxia in rats. In addition, the inhibitor SCH 42495, partially reversed the established cardio-pulmonary remodelling associated with this disease model, without elevating plasma ANP levels. 5. The physiological actions of ANP are many of the properties desirable in a treatment for pulmonary hypertension. Thus, attenuating the metabolism of this peptide using NEP inhibitors, should potentially enhance the effects of ANP, either by maintaining plasma levels or at a local, tissue level.

Neutral endopeptidase (NEP) inhibition in rats with established pulmonary hypertension secondary to chronic hypoxia

1. Atrial natriuretic peptide (ANP) causes vasorelaxation in the pulmonary vasculature. ANP levels are elevated in conditions characterized by pulmonary hypertension and it has been hypothesized that ANP may be autoregulatory in the pulmonary circulation. 2. One route of ANP metabolism in vivo is by the action of the enzyme neutral endopeptidase (NEP). We have studied the effects of the NEP inhibitor, SCH 42495, in rats with established pulmonary hypertension secondary to chronic hypoxia. 3. Rats (n = 32) were divided into 4 groups. Normoxic controls were kept in air for 10 days (NC10) and all other animals were placed in a normobaric hypoxic chamber (F1 O2 10%). Chronic hypoxic controls were studied at 10 days (CHC10). After 10 days hypoxia the two remaining groups received oral treatment for a further 10 days, consisting of either SCH 42495 (30 mg kg-1, twice daily CHT20) or methyl cellulose vehicle (0.4%, twice daily, CHV20). 4. Animals were anaesthetized and blood collected for measurement of plasma ANP. Hearts were dissected and ventricles weighed and the histology of the pulmonary vasculature examined. 5. CHC10 rats had significant right ventricular hypertrophy (0.53 +/- 0.08) and pulmonary vascular remodelling (29.0 +/- 0.01%) and had gained significantly less body weight (33.2 +/- 5.5 g) than NC10 rats (0.31 +/- 0.04, 10.9 +/- 0.01%, and 59.2 +/- 11.9 g respectively). CHC10 rats had significantly elevated plasma ANP levels (58.4 +/- 9.9 pM) compared with NC10 rats (23.9 +/- 32 pM). Treatment with SCH 42495 caused a significant reduction in pulmonary vascular remodelling (25.0 +/- 0.01%) and right ventricular hypertrophy (0.52 +/- 0.09) in CHT20 rats compared with CHV20 controls (33.0 +/- 0.02% and 0.61 +/- 0.09 respectively). Pulmonary vascular remodelling was also significantly lower in CHT20 rats than CHC1O animals.6. Thus, short term inhibition of NEP causes regression of established pulmonary vascular remodelling and may be a useful therapeutic strategy in pulmonary hypertension.

Haemodynamic effects of atrial natriuretic peptide in hypoxic chronic obstructive pulmonary disease

BACKGROUND

Pulmonary artery pressure is elevated in patients with advanced chronic obstructive pulmonary disease (COPD). Release of atrial natriuretic peptide (ANP) is increased in pulmonary hypertension and this hormone may both selectively vasodilate pulmonary vessels and inhibit pulmonary vascular remodelling. The hypothesis that ANP has a physiological role in protection of the pulmonary circulation from pressure overload, and that it may be beneficial in patients with COPD, has been examined.

METHODS

Ten patients with hypoxic COPD were infused for 30 minute periods with saline followed by ANP at 0.4, 2, and 10 pmol/kg/min respectively via a pulmonary artery catheter whilst monitoring haemodynamics and oxygenation.

RESULTS

Levels of immunoreactive ANP (irANP) increased from a mean (SD) of 23 (15) pmol/l to a maximum of 94 (41) pmol/l. Neither systemic blood pressure, cardiac output nor total systemic vascular resistance showed any correlation with irANP levels. There were negative correlations between levels of ANP and mean pulmonary artery pressure which fell from 28.7 to 25.9 mm Hg, pulmonary artery wedge pressure which fell from 6.5 to 4.6 mmHg, and total pulmonary vascular resistance which fell from 489 to 428 dynes s cm-5. There was a small fall in PaCO2 from 6.2 to 5.9 kPa, whilst venous admixture and oxygen delivery both increased non-significantly.

CONCLUSIONS

At these pathophysiological concentrations there was evidence that ANP selectively reduced right ventricular afterload. These data support the hypotheses that increased plasma levels of ANP may be beneficial in hypoxic COPD, and that endogenous ANP may ameliorate pulmonary hypertension in humans.

Exercise in patients with chronic obstructive pulmonary disease

Sporadic visits to the local doctor followed sometimes by changes in oral and inhaled bronchodilators and occasionally by the addition of steroids frequently does little to significantly improve symptoms and function in the disabled patient with COPD. As in other chronic diseases, the management of these patients is facilitated by a team approach in conjunction with general rehabilitation principles. The rationale and practical implementation of such a programme has recently been outlined by the American Association of Cardiopulmonary Rehabilitation. These are multifaceted programmes but a key component, as outlined above, is exercise training. In this brief review the various approaches available have been described. Controversy still reigns regarding the optimal modes of training and there are important differences among the several approaches. Two main groups can be delineated. One emphasises the detailed definition of the impaired physiology with therapeutic measures targeted to specific defects. There is good documentation that, conversely, unstructured programmes that use treadmill and free range walking and cycling also improve endurance for walking. Upper extremity training is of additional benefit. Programmes with as little as three sessions per week of 1-2 hours of low intensity activity have achieved success so we know that simple programmes can be helpful. Moreover, without the necessity for complex testing and training methods these programmes can be implemented with relatively low costs. Future investigations to examine the relationship between improved exercise capacity for walking and arm exercise on the one hand, and the ease of performance of activities of daily living on the other, will help to reinforce the effectiveness of exercise programmes.

Right ventricular function at rest and during exercise in chronic obstructive pulmonary disease

Right ventricular ejection fraction (RVEF), a measure of systolic pump performance of the right ventricle, is frequently depressed at rest or during exercise in patients with chronic obstructive pulmonary disease (COPD). The most common cause of reduced RVEF in COPD is augmentation of right ventricular afterload, namely an increase in pulmonary artery pressure and pulmonary vascular resistance. Therapy with agents that decrease the afterload on the right ventricle have the potential to improve the systolic performance of this chamber. Oxygen, vasodilators such as hydralazine and nifedipine, theophylline, and sympathomimetics all may augment RVEF in part by reducing pulmonary vascular resistance and, in some cases, pulmonary artery pressures in patients with COPD and cor pulmonale. However, only oxygen therapy has been shown to improve survival.

Pulmonary hemodynamics and physical training in patients with chronic obstructive pulmonary disease

The main hemodynamic abnormality in COPD is raised pulmonary vascular resistance and pulmonary hypertension. This is particularly evident when the vascular bed is stressed as in exercise; the absence of reserve collateral vessels prevents the normal reduction in pulmonary vascular resistance, and hence, pressure increases with flow. The increased afterload reduces right ventricular ejection fraction and stroke volume, but cardiac output is maintained by a relative tachycardia. Although most patients have a ventilatory limitation to exercise, in the later stages of the disease, hemodynamic factors may contribute. Studies of the effects of physical training on pulmonary hemodynamics have been few but none has shown any significant improvement. Occasionally there may be an increase in arteriovenous oxygen difference, accounting for the increase in symptom-limited oxygen consumption seen in some patients. The absence of hemodynamic effects of training may be due to insufficient training intensity. The often impressive increases in work tolerance after training may be due in part to an increase in muscular coordination and technique, as well as to metabolic training effects and psychologic factors.