Pulmonary lesions associated with oxygen therapy and artificial ventilation

Effects of PEEP on pulmonary mechanics and oxygen transport in the late stages of acute pulmonary failure

In 23 patients with advanced stages of acute respiratory failure, the value of various parameters for estimating the efficiency of ventilation with PEEP were analysed. PEEP increments of 1 cm of water corresponded to an increase of PaO2 of 2 mmHg. The cardiac output decreased from 8.3 +/- 0.3 l/min mean value at ZEEP to 7.3 +/- 0.3 L/min at a PEEP of +15 cm H2O. Corresponding to this, the oxygen transport showed a decrease from 1042 +/- 62 ml/min to 894 +/- 115 ml/min. The total compliance of 34 ml/cm H2O at ZEEP is already significantly reduced (a sign of the severe respiratory failure) and falls still further at a PEEP of 15 cm H2O to 22 ml/cm H2O. No notable recruitment of non ventilated alveolar spaces can be expected, in spite of the slight increase in the arterial oxygen tension. Taking the "best PEEP" (PEEP with maximum oxygen transport) as a reference point, arterial and mixed venous oxygen tension increase, the cardiac output decreases above this point and the total respiratory compliance shows no obvious changes. In the advanced stage of severe respiratory failure one cannot use the mixed venous oxygen tension or the compliance to find the best PEEP. The danger of barotrauma by PEEP ventilation in cases of significantly reduced compliance has to be considered in the choice of the ventilation pattern. The arterial oxygen tension may lead to a wrong estimation of the total efficiency of PEEP.

Histopathological study of the adverse effects of prolonged respiratory therapy on the neonate lung

Pulmonary alterations of 4 premature babies treated with mechanical ventilation and oxygen therapy for long duration ranged from 26 to 172 days, following respiratory distress syndrome, were studied. Loss of cilia, hyperplasia of reserve cells of bronchi and bronchioles, proliferation of elastic and collagenous fibers of alveolar ducts and saccules, and occasional hyperplasia of smooth muscle cells were usually observed. In the air spaces, emphysematous foci were intermingled with atelectatic area. Hyperplasia of II type alveolar cells and proliferation of interstitial cells were correlated with the effects of high concentrations of oxygen. Medial hypertrophy and intimal thickening of muscular type pulmonary arteries were prominent in long survivors. These pulmonary lesions may result from both mechanical ventilation and oxygen therapy.

Multiple pulmonary lesions in a patient treated with BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) for glioblastoma multiforme

A patient with a glioblastoma multiforme who was treated with BCNU, developed rapidly progressive pulmonary disease. The pulmonary changes were studied pathologically and included atypical alveolar cell hyperplasia, hyaline membranes, and interstitial fibrosis. These lesions contributed to the patient's demise and may be related to the administration of BCNU.

Pulmonary function following the adult respiratory distress syndrome

Fifteen patients (range of ages, 18 to 35 years) who survived an acute episole of the adult respiratory distress syndrome caused by mechanical or thermal injuries, sepsis, and shock were studied during 1 to 30 months after recovery. The patients had had no previous pulmonary diseases, and only two had been smokers. All of the patients were asymptomatic, and their chest x-ray films were normal on follow-up examination. Tests of pulmonary function revealed mild abnormalities which consisted of reduction of pulmonary volumes, decreased carbon monoxide diffusing capacity, and a mild increase of alveolar-arterial oxygen pressure gradients in the early stage ofter recovery. Improvement was noted after a few months, but eight patients still had mild reduction of pulmonary volume after one to two years. No correlation could be established between the severity of the adult respiratory distress syndrome, therapy with mechanically assisted ventilation, the duration of exposure to supplemental oxygen, the fractional concentration of oxygen in the inspired gas, and the degree of residual functional defect.

The pulmonary air-blood barrier of human shock lungs (a clinical, ultrastructural and morphometric study)

Interstitial edema in the alveolar septa is the first morphologically recognisable change to be observed in cases of shock. It is brought about by the altered function of the membranes of the damaged epithelium and endothelium in the alveolar wall. At the same time there is an impairment of gaseous exchange, which is rendered more difficult by the exudative process in the interstitium. Pari passu with these events there is injury to the cells of both the alveolar epithelium and the alveolar capillary endothelium. Both these processes are still reversible. The point of irreversibility appears to be reached--so far as time is concerned--at the end of the first week, after which the injurious effects on the cell are established, since the thin alveolar wall necessary for the exchange of gases becomes overgrown with bulky alveocytes (Tpye II), and the fibroblasts in thealveolar interstitium push the capillaries away from the surface of the alveolus. In most of the advanced cases of shock this process of thickening of the alveolar wall exceeds the critical value, and respiratory exchange is so impaired that satisfactory functioning of the lungs is no longer possible.

Inhibition of butylated hydroxytoluene-induced mouse lung cell division by oxygen: time-effect and dose-effect relationships

Mice were injected i.p. with 250 or 400 mg/kg of butylated hydroxytoluene (BHT). In vivo incorporation of thymidine into pulmonary DNA was measured on days 1-7 after BHT. 2, 3 and 4 days after BHT, DNA synthesis was inhibited by a 24-h exposure to 100% oxygen, whereas on days 5, 6 and 7 after BHT, oxygen failed to depress synthesis. A similar pattern was observed when incorporation of leucine into protein was measured: 2 and 4 days after BHT, oxygen decreased leucine incorporation, but had no effect 6 days after BHT or in animals not pretreated with BHT. It is concluded that the cells proliferating early after BHT, the type II alveolar cells, are more susceptible to the cytotoxic effects of oxygen than are interstitial and capillary endothelial cells.

Sodium metabolism

This brief review attempts to summarize important basic concepts of sodium metabolism including sodium ion distribution, sodium balance and the renal regulation of sodium excretion. Finally, an attempt has been made to relate these basic concepts to the mechanisms and management of common clinical situations of abnormal salt balance.

Extracorporeal membrane oxygenation in the treatment of respiratory failure--a review

Extracorporeal membrane oxygenation (ECMO) can be used for the treatment of acute respiratory failure. Based on recent experience in establishing such a method of treatment, this paper reviews those aspects of ECMO that need careful consideration before it can be undertaken. Methods of patient selection for ECMO and the physiological changes associated with it are also discussed.

Bronchopulmonary dysplasia in premature infants. A radiological and pathological correlation

In a group of 70 premature and newborn infants, treated with artificial ventilation, 24.3% developed bronchopulmonary dysplasia (BPD). Only in a very few cases did the typical radiological stages, as described by Northway, succeed each other in a chronological order. It is impossible to differentiate BPD stage I or II from RDS stage III and IV without a knowledge of the clinical course and of the duration of artificial ventilation. The lower the gestational age, the more severe and earlier do the radiological and histological changes occur. The radiological differential diagnosis of BPD includes Wilson-Mikity-syndrome, congenital pulmonary lymphangiectasia, neonatal tuberculosis, cystic fibrosis and Hamman-Rich-syndrome.

Pulmonary hypertension in severe acute respiratory failure

We repeatedly assessed pulmonary and systemic hemodynamics in 30 patients undergoing therapy for severe acute respiratory failure of diverse causes. Pulmonary-artery hypertension and elevated pulmonar vascular resistance were observed in all patients after correction of systemic hypoxemia. Increasing pulmonary blood flow by isoproterenol infusion or decreasing pulmonary blood flow by partial bypass of the right side of the heart minimally altered pulmonary-artery pressure. Although neither elevated pulmonary vascular resistance nor low cardiac index reliably predicted death, survivors had preogressive decreases of pulmonary vascular resistance with time, whereas nonsurvivors tended to maintain or increase pulmonary vascular resistance. Right ventricular stroke-work index was markedly elevated in all patients. The work load imposed upon the right ventricle by elevation of pulmonary vascular resistance may be a factor limiting survival in severe acute respiratory failure.

Pulmonary function following severe acute respiratory failure and high levels of positive end-expiratory pressure

In an 18-month period, we treated 561 patients with mechanical ventilation. Fifty-four (10 percent) of these patients had acute respiratory failure, requiring treatment with positive end-expiratory pressure (PEEP) in excess of 20 mm Hg (range, 20 to 40 mm Hg). All patients were allowed to breathe spontaneously between volume-limited mechanical breaths delivered at a rate sufficient to maintain an arterial pH greater than or equal to 7.35. PEEP was applied until calculated pulmonary venous admixture was minimized. Forty-three (80 percent) of these 54 patients were alive and asymptomatic three months after dischage from the hospital, and tests of pulmonary function were performed on ten patients within one year after hospitalization. Abnormalities in pulmonary function appeared to be reversible, and pulmonary function gradually approached normal within one year. It appears that neither acute respiratory failure nor exposure to high airway pressures caused significant permanent pulmonary damage in the ten patients studied.

Bronchopulmonary dysplasia: the pulmonary pathologic sequel of necrotizing bronchiolitis and pulmonary fibrosis

A light and electron microscopic study was carried out in 21 infants in whom the pathologic diagnosis of bronchopulmonary dysplasia had been made. All the infants except two had the respiratory distress syndrome at birth, and all 21 had been treated with respirator and oxygen therapy for various periods of time. The pathologic alterations observed in all the infants studied were primarily damage of the bronchial and bronchiolar ciliary apparatus and mucous membranes, severe necrotizing bronchiolitis, and marked bronchiolar and alveolar fibrosis. These changes were more pronounced in infants who survived the longest period of time. Such inflammatory and fibrotic changes are known to predispose to destruction of lung tissue, emphysema, and pulmonary hypertension. Six of these 21 infants developed symptoms and signs of cardiac atrial or ventricular stress, including cor pulmonale, prior to their demise. These infants were among those that survived the longest periods of time, had the longest exposure to supplemental oxygen, and showed histopathologically severe pulmonary fibrosis and emphysema.

The core pathobiology and integrated medical science of adult acute respiratory insufficiency

The straightforward core pathobiologic facts needed for the clinician's basic understanding of the clinical course and pathophysiology of progressive acute respiratory insufficiency (ARI) seen in surgical practice are summarized in the opening paragraphs. The remainder of the article provides the detailed evidence for elucidating the morphogenesis, i.e., the sequence of pathologic events, which determines the natural and the therapeutically altered clinicopathophysiologic courses of ARI. The attempt is to integrate observations concerning altered structure, cell biology, pathophysiology, physiologic function test data, bioengineering principles, clinical course, therapeutic management, and historical aspects of the disease process, into a detailed multidisciplinary but comprehensive explanation of this very complex, difficult disease process.

The lung: responses to trauma, surgery, and sepsis

The adult pulmonary distress syndrome is a disease of many etiologies and significantly contributes to the post-traumatic and postsurgical mortality and morbidity. Pulmonary insufficiency associated with shock and hemorrhage is characterized by its relatively short duration, less severe alterations of pulmonary functions, and normal pulmonary vascular resistance. The judicious use of fluids and emphasis in the early use of blood during resuscitation will minimize the magnitude of the pulmonary insult. Severe changes in oxygenation and ventilation, increases in pulmonary vascular resistance, the need for long-term respiratory assistance, and an increase in mortality and morbidity are characteristic of the adult pulmonary distress syndrome that follows severe systemic sepsis. Early aggressive pulmonary support is required in all life-threatening surgical conditions. Endotracheal intubation is preferred to tracheostomy, and the use of a volume respirator will facilitate the control of ventilation and oxygenation. Significant decreases in the functional residual capacity are responsible for refractory hypoxemia and the use of high concentrations of oxygen can be circumvented by the use of positive end expiratory pressure. PEEP is sometimes associated with a decrease in cardiac output and an increase in the pulmonary shunt and occasionally pneumothorax. Continued hemodynamic and pulmonary monitoring of patients is mandatory when using PEEP. Discontinuance of ventilatory assistance is usually possible if the pulmonary shunts are less than 25 per cent, the tidal volumes greater than 5 cc per kg, and the vital capacity at least twice the tidal volume. Recovery from pulmonary insufficiency is predicated on adequate pulmonary management, nutritional support, and the control of the underlying contributory conditions.

Severe viral pneumonia in young adults

Three patients with primary group-A influenzal pneumonia had diffuse pulmonary infiltrates, arterial oxygen tensions (PaO2) less than 50 mm Hg while breathing oxygen at 1 atm (fractional concentration of oxygen in the inspired gas (FIo2) equals 1.0), and right-to-left pulmonary shunts greater than 45 percent of total pulmonary blood flow. At an FIo2 of 1.0, end-expiratory pressure (EEP) was added in increments of 2 to 5 cm H2O every 30 to 60 minutes until the PaO2 was above 200 mm Hg and right-to-left shunting had fallen to less than 25 percent. The FIo2 was then lowered to 0.5. Using this systematic approach, all three patients required an FIo2 of 1.0 for less than 12 hours, minimizing the risk of oxygen toxicity. Two of the three patients did not require mechanical ventilation and breathed spontaneously while on continuous positive airway pressure (CPAP), and one of them tolerated an EEP of 31 cm H2O. Two patients survived, and one died of a neurologic complication of cardiopulmonary arrest, despite clearing on the chest x-ray film and improved gas exchange. Therapy with CPAP can be safely used in adults and has practical as well as theoretic benefits over continuous positive-pressure ventilation.

Closed circuit halothane anaesthesia. Use of the Narkotest as an in-line monitor in a nonpolluting technique

Theoretical considerations of closed circuit anaesthesia using oxygen and halothane are examined. Clinical experience has confirmed the value of the Narcotest as a reliable in-line monitor of inspired halothane concentration, while the use of an oxygen analyser is a desirable adjunct. The advantages of economy and elimination of theatre pollution are discussed.

The effect of respiratory frequency on pulmonary function during artificial ventilation. A review

This is a review of previous studies on the effects of variations between 12 and 24 breaths per minute in ventilation frequency during artificial ventilation, minute ventilation being constant. The total material consisted of 66 healthy subjects investigated under anaesthesia with artificial ventilation and 43 patients investigated during prolonged respiratory treatment. An increase in ventilation frequency resulted in an increased ratio of dead space to tidal volume (VD/VT) and in diminished alveolar ventilation with a subsequent elevation of Paco2. The pressures in airways and alveoli were lowered. The dynamic compliance both of the lungs and of the chest wall was diminished and inspiratory resistance was slightly reduced. Intrapulmonary gas distribution was unaffected. Cardiac output was increased, as was venous admixture. Pao2 was slightly reduced. The more efficient gas exchange occurring at a low ventilation frequency makes this setting preferable in the treatment of patients with chronic obstructive lung disease, whereas a high ventilation frequency, by improving cardiac output, may be advantageous in patients with circulatory failure.

A comparison of deaths from injury. 1947-56 compared with 1962-71

Deaths from injury occurring during a recent 10-year period at the Birmingham Accident Hospital were compared with those occurring during a similar period 15 years earlier. Reliable comparisons were not possible because of changes in policy that tended to reduce the delay in getting badly injured persons to hospital. The figures did show: 1. A slight increase in the number of deaths from domestic accidents which might account for: 2. A slight increase in the number of deaths following fracture of the femur. 3. A slight decrease in the number of deaths from road accidents. 4. A slight decrease in the number of deaths following head injury and a tendency for these deaths to be delayed in the second 10-year period. 5. Deaths following injuries of the trunk were mostly due to bleeding and some of these could be looked on as examples of failure in diagnosis or resuscitation or both. What still remains true is that prompt diagnosis and resuscitation, and well-judged definitive treatment offer the best prospect of reducing mortality. Accurate diagnosis may owe much to technical aids but it also requires observation of physical signs in the light of well-known patterns of injury.

Long-term results of continuous oxygen therapy at sea level

Twelve patients with hypoxemia associated with severe chronic obstructive pulmonary disease were treated with continuous portable oxygen therapy and have been followed up for a mean period of 25.2 months at sea level. Pulmonary function testing has revealed no further significant deterioration at long-term follow-up (17 months). After oxygen therapy was initiated, arterial carbon dioxide tension increased slightly, but decreased to pretreatment levels when patients were allowed to breathe room air. The electrocardiogram, which was unchanged at one month, has shown some reversal of cor pulmonale in five patients. Six patients have died, yielding a 56 percent survival rate at two-and-one-half years by the life table analysis. Five patients were autopsied, with possible oxygen toxicity being present in only one. The quality of life in our patients was improved and was especially represented by a reduction in hospital admissions for respiratory illness. We believe that continuous oxygen therapy is beneficial and worthwhile economically in certain patients.

Histopathological studies on experimentally induced pulmonary adenomatosis in guinea-pig lungs

The main purpose of our experimental series was to induce, in experimental animals, diffuse pulmonary fibrosis resembling that in human lungs. In the lungs of guinea-pigs injected with a soluble immune complex and continuously exposed to a 40-60 per cent oxygen-rich atmosphere, diffuse pulmonary fibrosis occurred in many cases in the course of 2 to 3 months after the injection. After the 100th experimental day, multiple foci of pulmonary adenomatosis occurred. The morphology was similar to that of Jaagsiekte. Electron microscopic observations revealed that these hyperplastic cells originated from type II pneumoncytes.

Central necrosis of the spinal cord induced by hyperbaric oxygen exposure

Seventy-six adult rats were exposed to 60 psig of oxygen on consecutive days until death. At autopsy, 17 of the animals segmental foci of central necrosis of the spinal cord gray matter, often associated with small ball- and flame-shaped hemorrhages in either the cervical and/or lumbosacral enlargements. Paraplegia or quadriplegia were clinically observed prior to death. The oxygen-induced spinal cord lesions are similar though not identical to those observed in experimental and human spinal cord trauma. These observations indicate that the therapeutic use of hyperbaric oxygen in patients with spinal cord injury has a potential danger of causing central spinal cord necrosis.

Pathologic pulmonary changes in hemorrhagic shock

Fifty-seven dogs were subjected to hemorrhagic hypotension by a variety of protocols. Histologic pulmonary changes were studied using the light microscope. Of these 57 dogs, 21 had no demonstrable lesions, 8 had minimal changes, and 28 had moderate or severe lesions, all of a focal nature. No correlation was found between the presence of lesions and mean systemic arterial pressure during shock, the udration of the hemorrhagic period, the fate of the animal, preoperative hematocrits and blood volumes, mean postreinfusion arterial pressure, whether the animals were mongrels or purebred beagles, whether they were awake or sedated, whether they breathed spontaneously or were artifically ventilated, whether they had undergone previous splenectomy or not, whether hilar stripping was performed or not, and finally, whether blood was reinfused after hemorrhage or not. Thus we conclude that multiple factors may exert a harmful effect on the lung in hemorrhagic shock, and that shock probably makes the lungs more vulnerable to other injurious agents rather than there being one single pathogenetic mechanism for the pulmonary damage. The term "adult respiratory distress syndrome" rather than "shock lung" is best used for the human clinical entity since it implies a complex ettiology rather than a discrete pulmonary lesion produced by a single pathogenetic mechanism.

Shock lung: fact or fancy?

Shock lung can be considered a relatively new pathologic syndrome. Its rapidly increasing incidence is a tribute to advanced sophistication in the salvage of severely traumatized patients and in those undergoing major surgery who would not have survived 25 years ago. No single factor can be credited as the sole precipitator of this syndrome. Alone, many of the factors may be insignificant; but combined they are often synergistic and end in a respiratory death. Although all of the mechanisms and interrelationships are not known for every case, early recognition of the specific contributing etiologies aid in both the prevention and, when that fails, in the treatment of shock lung. Today, by careful precise diagnostic monitoring, many cases of post-traumatic pulmonary insufficiency, i.e., shock lung, can be treated with resultant cure. The term shock lung is valuable only in alerting the physician to the fact that the patient is in "big trouble." The physician must then try to sort out all of the possible factors and treat each accordingly. We might compare the end result of shock lung to the end stage of renal disease. The fact is that they are both nonspecific responses of an end organ to many different and interrelated etiologies. To expect to define a single, all encompassing etiology is pure fancy.

The immersion incident

The ever increasing participation in aquatic recreational activities is a major factor in the increasing number of deaths due to accidental immersion. Some of these deaths occur while undergoing resuscitative efforts immediately following rescue, on admission to hospital, or even up to 19 days after the immersion incident. Drowning, either acute or its delayed effects, is chiefly responsible for these deaths, but in a number, hypothermia occurring alone or complicating drowning, is the likely explanation. This paper examines the problem and proposes a regime of management.

Pulmonary mechanics in infants surviving severe neonatal respiratory insufficiency

Pulmonary mechanics was studied in 24 survivors of severe neonatal ventilatory insufficiency, 15 infants had idiopathic respiratory distress syndrome (IRDS), 6 recurrent severe apnoeic spells, and 3 postasphyxia syndrome. Of the infants with IRDS, 5 were treated with intermittent positive pressure ventilation (IPPV), 3 with continuous positive airway pressure (CPAP) via an endotracheal tube and 7 with CPAP applied via a face chamber. The other infants were all treated with IPPV. IPPV-treated infants generally had lower than expected values of dynamic compliance and pulmonary conductance, particularly after prolonged treatment. All infants treated with CPAP via a face chamber had normal mechanics, but a trend towards obstruction of the airways after varying periods of time was observed in most infants, irrespective of diagnosis or treatment. One infant treated with CPAP via an endotracheal tube and given pure oxygen for a long time had gross abnormalities suggesting bronchopulmonary dysplasia. Measurement of pulmonary conductance appears to be a reliable prognostic tool as concerns pulmonary symptoms later in infancy.

Paraquat lung: a reappraisal

Smith, P. and Heath, D. (1974).Thorax, 29, 643-653. Paraquat lung: a reappraisal. The histopathology of the lungs from four human cases of paraquat poisoning is described. In two of them there was a dense mass of fibroblastic tissue which obliterated the lung architecture, and one of these showed an extensive deposit of collagen with honeycomb change. In a third case pulmonary fibrosis was less severe and could be demonstrated exclusively within the alveolar spaces. The fourth showed earlier lesions of capillary congestion, alveolar oedema, and hyaline membrane formation. We suggest that paraquat produces the same effect on the lung in man as in the rat, namely a diffuse, cellular, intra-alveolar fibrosis. The intra-alveolar origin of this fibrosis is often obscured in the advanced stage of the disease and has been misinterpreted as fibrosing alveolitis. This fibrosis is associated with a pulmonary vascular disease. In assessing the histopathology of the lung in paraquat poisoning a history of oxygen therapy must be taken into account, for prolonged exposure to this gas may in itself induce pulmonary fibrosis.