Blood Gas Abnormalities Research Articles

Laryngeal and diaphragmatic muscle activities after central nervous system lesions in cats

Aim: To examine the central control and coordination of respiratory pump muscles and laryngeal valve muscles by systematic decerebration (DECER), cerebellectomy (CBELL), pontine respiratory group lesioning (PRG) and pontomedullary section (PMED). Methods: Activities of posterior cricoarytenoid (PCA), thyroarytenoid (TA) and diaphragm (D) muscles and their responses to inspiratory (I) and expiratory (E) total occlusions were determined in 10 adult cats. Results: INTACT anesthetized cats (n= 6) exhibited inspiratory PCA (PCAI) and D activities. Expiratory PCA (PCAE) was present but TA activity was absent. It was found that successive DECER, CBELL and PRG lesions attenuated PCAE, the intact pattern being noted in 7/10, 4/10 and 0/6 cats, respectively. After PMED, variable PCA, TA and continuous D activities occurred only with blood gas abnormalities. Augmented PCA and D responses to I- and E-loads occurred after PRG lesions: the I-load PCAI and D responses resembled apneusis and the E-load PCAE and D responses resembled central apnea. Conclusion: The decreasing PCAE activity observed with successive DECER, CBELL and PRG lesions suggests that these areas influence laryngeal abductor control of glottic size. The synchronous activities after PMED transection suggest a role for more rostral structures in coordinating laryngeal and diaphragmatic muscle activities.

Laryngeal and diaphragmatic muscle activities after central nervous system lesions in cats

To examine the central control and coordination of respiratory pump muscles and laryngeal valve muscles by systematic decerebration (DECER), cerebellectomy (CBELL), pontine respiratory group lesioning (PRG) and pontomedullary section (PMED). Activities of posterior cricoarytenoid (PCA), thyroarytenoid (TA) and diaphragm (D) muscles and their responses to inspiratory (I) and expiratory (E) total occlusions were determined in 10 adult cats. INTACT anesthetized cats (n = 6) exhibited inspiratory PCA (PCA(I)) and D activities. Expiratory PCA (PCA(E)) was present but TA activity was absent. It was found that successive DECER, CBELL and PRG lesions attenuated PCA(E), the intact pattern being noted in 7/10, 4/10 and 0/6 cats, respectively. After PMED, variable PCA, TA and continuous D activities occurred only with blood gas abnormalities. Augmented PCA and D responses to I- and E-loads occurred after PRG lesions: the I-load PCA(I) and D responses resembled apneusis and the E-load PCA(E) and D responses resembled central apnea. The decreasing PCA(E) activity observed with successive DECER, CBELL and PRG lesions suggests that these areas influence laryngeal abductor control of glottic size. The synchronous activities after PMED transection suggest a role for more rostral structures in coordinating laryngeal and diaphragmatic muscle activities.

Sleep dysfunction in neuromuscular disorders

There is an increasing awareness of sleep dysfunction in neuromuscular disorders. Most of the sleep disturbances in neuromuscular disorders are secondary to sleep disordered breathing. Sleep-disordered breathing in neuromuscular disorders is commonly associated with a slowly developing chronic respiratory failure, particularly in the advanced stages, but the condition often remains unrecognized and untreated. The most common sleep-disordered breathing in neuromuscular disorders is sleep-related hypoventilation which initially manifests during REM sleep and later as the disease advances, it is also noted during non-REM sleep and even during daytime. In addition to the hypoventilation, central and upper airway obstructive apneas as well as hypopneas occur. Hypoventilation during sleep gives rise to hypoxemia and hypercapnea causing chronic respiratory failure. The abnormal blood gases may later persist during the daytime. Some patients may, however, have sleep onset or maintenance insomnia as a result of associated pain, muscle immobility, contractures, joint pains and muscle cramps as well as anxiety and depression.The commonest complaint in patients with neuromuscular disorders associated with sleep-disordered breathing is excessive daytime somnolence as a result of repeated arousals and sleep fragmentation due to sleep hypoventilation and transient nocturnal hypoxemia. Sleep-disordered breathing causing sleep disturbance is well known in patients with poliomyelitis, postpolio syndrome, amyotrophic lateral sclerosis, also known as motor neuron disease, primary muscle disorders including muscular dystrophies and myotonic dystrophy, congenital or acquired myopathies, neuromuscular junctional disorders and polyneuropathies. All of these conditions may cause weakness of the diaphragm, the intercostal and accessory muscles of respiration causing breathlessness and other respiratory dysrhythmias. As a result of the respiratory and upper airway muscle weakness, the normal sleep-related respiratory physiologic vulnerability becomes pathological in these patients with neuro-muscular disorders causing hypoventilation or central and upper airway obstructive apneas during sleep. Multiple factors are responsible for sleep-disordered breathing in neuromuscular disorders causing sleep hypoventilation and other respiratory dysrhythmias, and these include: impaired chest bellows, increased work of breathing, hypo-responsive respiratory chemoreceptors, increased upper airway resistance, decreased minute and alveolar ventilation, REM-related marked hypotonia or atonia of the respiratory muscles except the diaphragm, respiratory muscle fatigue and kyphoscoliosis secondary to neuromuscular disorders causing extrapulmonary restriction of the lungs. Nocturnal hypoventilation and chronic respiratory failure in neuromuscular disorders may present insidiously and initially may remain asymptomatic. A high index of clinical suspicion is needed. Clinical clues suggesting sleep-disordered breathing include daytime hypersomnolence, breathlessness, disturbed nocturnal sleep and unexplained leg edema. If the clinical clues strongly suggest sleep-disordered breathing, a physical examination must be directed to uncover bulbar and respiratory muscle weakness. Patients with neuromuscular disorders showing these clinical features must be investigated to uncover nocturnal hypoventilation to prevent serious consequences of chronic.

Mechanical Ventilation in Foals with Botulism: 9 Cases (1989–2002)

"Shaker foal" disease, toxicoinfectious botulism of foals, was 1st described as a clinical entity in 1967. The reported mortality rate was 90%, with death occurring within 24-72 hours of the onset of the characteristic clinical signs. The mortality rate decreased when equine-origin botulism antitoxin became available; however, a certain percentage of foals continued to die of respiratory failure. Mechanical ventilation is an important part of the treatment of infant botulism and is essential to the survival of many affected infants. We report a retrospective study of 9 foals with toxicoinfectious botulism where early mechanical ventilation was employed as part of the treatment. Foals receiving mechanical ventilation were progressively acidemic and had increased PaCO2 tensions before mechanical ventilation. These arterial blood gas abnormalities were ameliorated with mechanical ventilation. One foal was euthanized for economic reasons; survival in treated foals was 87.5%. Mechanical ventilation of foals with botulism and respiratory failure appears to be an effective therapy.

Dopplerfluxometria do ducto venoso: relação com a gasometria em fetos prematuros com centralização de fluxo sangüíneo

OBJETIVO: avaliar o desempenho da dopplerfluxometria do ducto venoso (DV) na detecção da acidemia em fetos prematuros apresentando centralização de fluxo sangüíneo. MÉTODOS: estudo observacional transversal. A população em estudo consistiu de 48 gestantes entre a 25ª e a 33ª semana de gestação, que apresentavam centralização de fluxo sangüíneo fetal (relação umbílico/cerebral >1). O tempo decorrido entre o diagnóstico de centralização fetal e o nascimento (cesariana sob anestesia peridural) foi de até cinco horas. Os seguintes parâmetros foram estudados: relação sístole ventricular atrial (S/A) do ducto venoso, pH e base excess (BE) de amostra de sangue da veia umbilical colhida imediatamente após o nascimento. A relação S/A do DV foi considerada anormal quando maior que 3,6. Os conceptos foram classificados quanto ao resultado da gasometria, sendo considerada gasometria anormal quando pH <7,26 e BE <6 mmol/L. O estudo estatístico utilizado foi o teste de Fisher, considerado significativo quando p < 0,05. RESULTADOS: a correlação entre a gasometria do cordão umbilical de fetos prematuros centralizados e a relação S/A do DV foi significativa (p=0,0000082; teste de Fisher). A dopplervelocimetria do DV foi capaz de identificar 10 dos 14 fetos com gasometria anormal. Por outro lado, 32 dos 34 fetos com gasometria normal foram corretamente identificados. A sensibilidade da dopplerfluxometria do DV para o diagnóstico de acidemia fetal ao nascimento foi de 71%, a especificidade foi de 94%, a taxa de falso-negativo de 8%, a taxa de falso-positivo de 4%, o valor preditivo positivo de 83% e o valor preditivo negativo de 89%. A probabilidade pré-teste para um feto centralizado de apresentar acidemia ao nascimento foi de 31%. Já a probabilidade de acidemia após resultado do DV anormal (probabilidade após teste anormal) foi de 84%, ao passo que a probabilidade de acidemia fetal com o DV normal (probabilidade após-teste normal) foi de apenas 10%. CONCLUSÃO: a análise da relação S/A do ducto venoso se mostra adequada para o diagnóstico de gasometria anormal em fetos prematuros, centralizados.

Cardiopulmonary support during electrophysiological procedures for ventricular tachycardias not haemodynamically tolerated.

The objectives of this study were to evaluate the efficacy of percutaneous cardiopulmonary support (CPS) for circulatory assistance during electrophysiological endocavitary procedures for ventricular tachycardia (VT) in high-risk patients. From January to June 1999, eight patients with VT not haemodynamically tolerated, underwent an electrophysiological mapping and ablation while supported with percutaneous CPS in the cardiac surgery service of the University of Milan. The CPS system allowed for the maintenance of an arterial pressure of 60-70 mmHg during the tachycardia episodes. CPS was used for 10-20 min periods to restore haemodynamic stability. With the haemodynamic support of CPS, it was possible to target and induce 21 VTs, with a mean cycle of 325 ms. The mean support time was 140 min (120-160 min). Stabilization of the arterial pressure at a mean value of 65 mmHg (55-85 mHg) was achieved over a mean period of 26 seconds. Oxygen saturation remained over 90% throughout the support for all patients, with no blood gas or electrolyte abnormalities. No CPB-related complications were observed. In conclusion, percutaneous CPS guarantees effective haemodynamic support during mapping and ablation of VTs not haemodynamically tolerated, with no complications related to the extracorporeal circulation or the cannulation.

Predictors of severe morbidity and death after elective abdominal aortic aneurysmectomy in patients with chronic obstructive pulmonary disease.

This study sought to identify risk factors associated with an unfavorable outcome after elective abdominal aortic aneurysm (AAA) repair in patients with chronic obstructive pulmonary disease (COPD). The clinical records of 158 patients who underwent elective open AAA repair with COPD determined from preadmission International Classification of Diseases-ninth revision codes during a 12-year period at the University of Michigan were reviewed. Patients with uncomplicated outcomes (group I) were compared with those with unfavorable postoperative outcomes (group II). The unfavorable outcomes were defined as myocardial infarction, acute renal failure, worsening respiratory insufficiency necessitating tracheostomy, or death within 30 days of surgery. Logistic regression analyses of variables that were identified as being statistically significant in the univariate analysis were used to develop a predictive model of these events. Group I included 133 patients (77 men, 56 women) with a mean age of 70.1 years, and group II included 25 patients (13 men, 12 women) with a mean age of 71.4 years. Preoperative factors statistically related (P =.002) to an unfavorable outcome in group II patients included: suboptimal COPD management (fewer prescribed inhalers), lower hematocrit, preoperative renal insufficiency, and coronary artery disease. Importantly, abnormal preoperative spirometry and arterial blood gases were not predictive of a poor outcome. Univariate analysis also revealed increased hospital (25 versus 13 days; P =.0001) and intensive care unit (14 versus 4 days; P =.001) length of stays and a greater need for prolonged ventilation (8 versus 1 day; P =.039) for group II patients compared with group I patients. The 30-day mortality rate in the entire experience was 3.2% (5/158). No specific variables associated with mortality were identified. Fewer prescribed inhalers, lower hematocrit, renal insufficiency, and coronary artery disease are preoperative factors associated with unfavorable outcomes after open elective surgical repair of AAA in patients with COPD. Intensive management of these factors may reduce the hazards of AAA operations in these patients. COPD alone should not be considered a deterrent to the surgical treatment of AAAs.

Spinal penetration index: new three-dimensional quantified reference for lordoscoliosis and other spinal deformities

AbstractWe studied and conceptually analyzed a retrospective case series of patients with airway compression due to an anterior vertebral body protrusion. The goal was to describe the pathology, methods of management, and a new concept for quantifying deformity. Case reports have been published on this pathology, but there has been no case series to date. In this study 18 patients with ages ranging from 7.3 to 18.0 years had thoracic lordoscoliosis due to a variety of etiologies; most (n = 10) had a neuromuscular disorder. Following treatment, which most commonly was anterior subtotal subperiosteal vertebral body resection followed by posterior instrumentation and arthrodesis, atelectasia disappeared and any abnormal blood gases normalized; however, the effect on vital capacity was variable. Based on computed tomographic studies, the concept of the deformity as an endothoracic vertebral hump was developed and quantified. Study of this series of patients with compression of the airway due to vertebral body protrusion into the thorax provided the opportunity to describe treatment, define a new concept (the spinal penetration index), and make general recommendations about the management of both the endothoracic hump and the exothoracic rib hump.

Doxapram for ventilatory failure due to exacerbations of chronic obstructive pulmonary disease.

COPD is a progressive illness and in the later stages, exacerbations may lead to ventilatory failure. The combination of hypoxia and hypercapnia can lead to coma and death. Correction of these blood gas abnormalities is a medical emergency. Doxapram is a respiratory stimulant used to stimulate breathing in this setting. The objective of this review was to assess the effects of doxapram on gas exchange and clinical outcomes in people with ventilatory failure due to acute exacerbations of chronic obstructive pulmonary disease. We searched the Cochrane Airways Group trials register and reference lists of articles. We also contacted experts in the field, study authors and drug companies. Randomised trials comparing doxapram with other treatments or placebo in people with ventilatory failure due to exacerbations of chronic obstructive pulmonary disease. One reviewer assessed trial quality and extracted data. Three trials involving 127 people were included. The trials were of variable quality. Doxapram was marginally superior to placebo in preventing blood gas deterioration (odds ratio 0.38, 95% confidence interval 0.14 to 1.02). In one small study, of 17 patients, doxapram and non-invasive ventilation appeared equally effective in terms of blood gases changes, although there were slightly more deaths with doxapram (odds ratio 11.34, 95% confidence interval 1.00 to 128.03). Doxapram may improve blood gas exchange in the short term, but newer techniques such as non-invasive ventilation may be more effective.

Obstructive sleep apnea and the prefrontal cortex: towards a comprehensive model linking nocturnal upper airway obstruction to daytime cognitive and behavioral deficits.

Obstructive sleep apnea (OSA) is accompanied by significant daytime cognitive and behavioral deficits that extend beyond the effects of sleepiness. This article outlines a causal model by which to understand these psychological effects among OSA patients. The model proposes that sleep disruption and blood gas abnormalities prevent sleep-related restorative processes, and further induce chemical and structural central nervous system cellular injury. This, in turn, leads to dysfunction of prefrontal regions of the brain cortex (PFC), manifested behaviorally in what neuropsychologists have termed 'executive dysfunction'. Executive dysfunction is proposed to markedly affect the functional application of cognitive abilities, resulting in maladaptive daytime behaviors. The proposed model (1) accounts for the specific psychological phenotype associated with OSA, (2) accommodates developmental components in this phenotype, (3) bridges between physical and psychological phenomena, (4) suggests mechanisms by which the nocturnal disorder might have effects on daytime functioning, (5) is empirically testable, (6) generates unique research hypotheses, and (7) has practical implications. The model is intended to act as a catalyst for future research and as a preliminary guide for clinicians.

Effects of Pharmacological Dose of Dexamethasone Given Postnatally on Blood-Brain Barrier Permeability and Brain Water Content

To the Editor: We read with interest the paper from G. D. Sysyn et al. ([2][1]), who published their observations regarding the effects of postnatal corticosteroid (intramuscular dexamethasone injections, doses: 0.01, 0.25, and 0.5 mg/kg) on regional blood-brain barrier permeability (transfer

Efficacy of diaphragmatic breathing in persons with chronic obstructive pulmonary disease: a review of the literature.

The evidence base for diaphragmatic breathing (DB) as an adjunctive treatment modality for persons with COPD is questionable. This article reviews the literature regarding the efficacy of DB in persons with chronic obstructive pulmonary disease (COPD), and reports on the beneficial and detrimental effects of DB in persons with COPD. Diaphragmatic breathing has been described as breathing predominantly with the diaphragm while minimizing the action of accessory muscles that may assist with inspiration. No single or combined patient characteristic has been identified consistently to help predict which person with COPD may benefit from DB. However, it has been suggested that persons with moderate to severe COPD and marked hyperinflation of the lungs without adequate diaphragmatic movement and increase in tidal volume during DB may be poor candidates for instruction in DB. Conversely, persons with COPD who have elevated respiratory rates, low tidal volumes that increase during DB, and abnormal arterial blood gases with adequate diaphragmatic movement may benefit from DB. Identification of an abdominal paradoxical breathing pattern and worsening dyspnea and fatigue during or after DB are criteria to modify or terminate DB. Persons with COPD demonstrating an abdominal paradox during DB may benefit from a more upright body position or trunk flexion. Several methods to examine diaphragmatic movement and the potential for success with DB will be discussed. Future research is needed to better identify which patients may benefit from DB.

Caesarean delivery of breech babies is beneficial for infant health but has no impact on maternal health

Objective: To compare maternal and neonatal outcomes in elective cesarean vs. attempted vaginal delivery for breech presentation at or near term. Methods: We reviewed the maternal and neonatal charts of all singleton breech deliveries of at least 35 weeks’ gestation or 2000 g delivered between 1986 and 1997 at our institution. Patients delivered by elective cesarean were compared to those attempting a vaginal delivery. The neonatal outcomes analyzed were: corrected mortality; Apgar scores less than 7 at 5 min; abnormal umbilical cord blood gases; birth trauma; and admissions to the intensive care nursery. Maternal morbidity was also assessed and compared. Results: Of 848 women meeting criteria for evaluation, 576 were delivered by elective cesarean while 272 attempted a vaginal delivery. Of 272 women undergoing a trial of labor, 203 (74.6%) were delivered vaginally, while 69 (25.4%) failed an attempt at vaginal delivery and underwent a cesarean. When comparing patients delivered by elective cesarean with those attempting a vaginal delivery, no significant differences were noted in neonatal outcomes. However, maternal morbidity was higher among women delivered by cesarean, regardless of the indications for the procedure. Similar neonatal and maternal results were noted when nulliparous patients were analyzed separately. Conclusions: Cesarean delivery of selected near-term infants presenting as breech is associated with increased maternal morbidity without corresponding improvement in neonatal outcomes.

Diagnosis of Pulmonary Embolism

Pulmonary embolism (PE) is a common, lethal yet treatable disease. The clinical diagnosis of PE remains to be a problem due to the nonspecific presenting signs, symptoms, electrocardiographic findings, arterial blood gas abnormalities and chest X-ray changes. Despite these nonspecific clinical findings, clinicians are adept at assigning pretest probability using overall clinical assessment. Clinical models have been developed to improve the accuracy of pretest probability assessment. D-dimers are becoming a widely available clinical tool useful in the diagnostic management of suspected PE. The limitations of the imaging modalities for PE [ventilation–perfusion (V/Q) scanning, spiral computerised tomography, pulmonary angiography and venous leg imaging] necessitate the use of these tests in series and in combination with clinical pretest probability assessment and D-dimer in diagnostic management algorithms. These algorithms permit safe diagnostic management of patients with suspected PE while limiting invasiveness, inaccessibility and expense.

POSTOPERATIVE PULMONARY COMPLICATIONS

Patients undergoing elective surgery first need to be screened for operative risks by reviewing factors that relate to the patient and factors that relate to the procedure they are undergoing. The identification of high-risk patients undergoing high-risk procedures may be aided by reviewing the following factors: the presence of symptomatic lung disease, smoking, obesity, abnormal blood gas values, spirometry, and presence of sleep apnea. The more risk factors a patient has, the more likely the patient will develop postoperative complications. Further risk stratification may be accomplished by means of exercise testing, either through formal cardiopulmonary exercise testing or through symptom-limited stair climbing. When high-risk patients are identified, preoperative therapy aimed at reducing overall postoperative morbidity and mortality may help decrease the risk to a minimum.

Route of breech delivery and maternal and neonatal outcomes

Objective: To compare maternal and neonatal outcomes in elective cesarean vs. attempted vaginal delivery for breech presentation at or near term. Methods: We reviewed the maternal and neonatal charts of all singleton breech deliveries of at least 35 weeks’ gestation or 2000 g delivered between 1986 and 1997 at our institution. Patients delivered by elective cesarean were compared to those attempting a vaginal delivery. The neonatal outcomes analyzed were: corrected mortality; Apgar scores less than 7 at 5 min; abnormal umbilical cord blood gases; birth trauma; and admissions to the intensive care nursery. Maternal morbidity was also assessed and compared. Results: Of 848 women meeting criteria for evaluation, 576 were delivered by elective cesarean while 272 attempted a vaginal delivery. Of 272 women undergoing a trial of labor, 203 (74.6%) were delivered vaginally, while 69 (25.4%) failed an attempt at vaginal delivery and underwent a cesarean. When comparing patients delivered by elective cesarean with those attempting a vaginal delivery, no significant differences were noted in neonatal outcomes. However, maternal morbidity was higher among women delivered by cesarean, regardless of the indications for the procedure. Similar neonatal and maternal results were noted when nulliparous patients were analyzed separately. Conclusions: Cesarean delivery of selected near-term infants presenting as breech is associated with increased maternal morbidity without corresponding improvement in neonatal outcomes.

Ventilation-perfusion distributions in different porcine lung injury models.

Acute lung injury is characterized by hypoxemia which may be caused by hypoventilation, ventilation-perfusion (V(A)/Q) mismatch, intrapulmonary shunting and oxygen diffusion impairment. The multiple inert gas elimination technique (MIGET) allows analysis of these four causes of hypoxemia and is therefore the most comprehensive approach to investigate blood gas abnormalities. Using MIGET, we studied whether specific patterns of gas exchange abnormalities occur in different lung injury models and whether gas exchange abnormalities can be related to pathogenic aspects of lung injury. Lung injury was induced with oleic acid injection, endotoxin infusion or repeated lung lavage in groups of 6 mechanically ventilated pigs. PaO2 decreased and PaCO2 increased significantly in all three lung injury models, but gas exchange was more impaired in the oleic acid and lavage, as compared to the endotoxin group. Shunt was the major cause of hypoxemia in our lung injury models, whereas V(A)/Q mismatch contributed to venous admixture only after oleic acid injection and lung lavage. Oxygen diffusion limitation was not observed. Although alveolar ventilation was maintained after induction of lung injury, hypercapnia developed due to an increase of the ventilatory mean towards higher V(A)/Q ratios, increased shunt and increased carbon dioxide production. Shunt and ventilation-perfusion mismatch fully explain the gas exchange disturbances observed in our lung injury models. Although V(A)/Q distributions can be related to pathogenic aspects of the three study groups, we did not observe specific V(A)/Q patterns which allow diagnosis of the type of lung injury from a recovered V(A)/Q distribution.

Blood gases at rest and during exercise in patients with α1-Pi deficiency

α1-protease inhibitor (Pi) deficiency is associated with a protease–anti-protease imbalance leading to premature destruction of lung tissue and early emphysema. Little is known about the blood gases of these patients in the various stages of the disease. The purpose of this study was to evaluate blood gases in patients with α1-Pi deficiency when patients were at rest and during exercise, and to correlate these with lung function measurements. A total of 369 patients with severe α1-Pi deficiency had pulmonary function test and blood gas analysis, 282 also had blood gases taken during steady state submaximal exercise testing. Only 21% of the patients had normal blood gases at rest; 71% had mild hypoxaemia; 8% had severe hypoxaemia. Surprisingly, 61% of the patients with mild lung disease and a FEV1of more than 65% predicted were hypoxaemic. During exercise 65% of the patients had a drop in PO2of more than 0·40 kPa. FEV1was a significant predictor for the PO2values at rest and during exercise. During exercise the arterial–alveolar gradient increased in about 50% and decreased in 25% of the patients. Many patients with α1-Pi have blood gas abnormalities. Impaired blood gases in early stages of the disease result in a discrepancy between lung function parameters and blood gases. FEV1measurements inadequately capture the extent of lung disease in patients with α1-Pi deficiency, and both blood gases at rest and during exercise are needed in the assessment of all stages of the disease.

Pulmonary Dysfunction in Chronic Liver Disease

Pulmonary abnormalities and symptoms are common in patients with chronic liver disease. If questioned, up to 70% of cirrhotic patients undergoing evaluation for liver transplantation complain of dyspnea. 1 In screening studies of patients with chronic liver disease, arterial blood gas abnormalities are found in as many as 45% and abnormal pulmonary function tests in as many as 50%. 2 A variety of causes for pulmonary dysfunction in liver disease have been identified and include intrinsic cardiopulmonary disorders not specifically related to liver disease as well as unique problems associated with the presence of liver disease and/or portal hypertension (Table 1). The recognition that a subset of patients with hepatic disease develop significant pulmonary vascular alterations, either microvascular dilation leading to the hepatopulmonary syndrome (HPS) or arteriolar vasoconstriction leading to portopulmonary hypertension, indicates that unique changes in the pulmonary vasculature may occur in liver disease. These pulmonary vascular syndromes significantly impact morbidity and mortality in affected patients and influence candidacy for liver transplantation. This review will focus on the most common abnormality in the pulmonary vasculature in liver disease: HPS. It will address the differential diagnosis, clinical features, diagnostic evaluation, therapy, and pathogenesis of this increasingly well-recognized syndrome.

Fetal Doppler Hemodynamic Changes in Spontaneous Versus Prostaglandin E1-Induced Active Labor

Background. To assess fetal hemodynamic changes before and during active labor, either spontaneous or prostaglandin E 1 (PGE 1 )-induced labor. Materials and methods. This is a prospective longitudinal study and a cohort of 49 healthy women at 37-41 + weeks gestation without signs of fetal distress was investigated until in labor. One group of 23 healthy women had spontaneous active labor, the second group of 26 women was in active labor induced by an intra-cervical administration of PGE 1 for elective induction. Blood flow waveform indices (S/D ratio, RI, PI) were assessed by pulsed Doppler ultrasonography from the umbilical artery (UA) and fetal middle cerebral artery (MCA) before and in labor. Both groups were compared for the waveform indices and perinatal outcome including duration of labor, meconium stain, baby sex, birthweight, UA blood gas measurements at delivery, Apgar's scores, prolonged nursery stay (≥5 days), and NICU admission. Results. Demographic data of the two groups were comparable. During spontaneous active labor, the S/D ratio and RI became significantly decreased in the UA (p<0.05) and the three waveform indices were decreased more in the MCA (p<0.01, 0.005, 0.05, respectively) compared with those measured before labor. During PGE 1 -induced active labor, all the waveform indices were not significantly decreased in either the UA or the MCA. The occurrence of abnormal UA blood gas values was significantly more in the PGE 1 -induced group than in the spontaneous labor group (23.1% v.s. 4.3%; p<0.05). No other adverse perinatal outcomes were observed in either group. Conclusions. Decreasing impedance in both the UA and MCA during spontaneous labor is a physiological fetal adaptation to labor to prevent fetal cerebral hypoxia by maintaining adequate brain blood flow during normal parturition. This fetal adaptation phenomenon was not observed in the group of PGE 1 -induced labor with the result of a high incidence of abnormal UA blood gas values.