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

An in Vitro Physiologic Model for Cardiopulmonary Simulation: A System for ECMO Training

Extracorporeal life support (ELS) systems may be run by certified perfusionists, specially trained nurses or respiratory therapy staff. Guidelines for the training, certification and retraining of ELS operators have been established by the Extracorporeal Life Support Organization. Recommendations include “… a well defined program for staff training, certification, and retraining”. Some clinicians have suggested that ELS operators be certified and recertified in an animal laboratory. But such practice involves veterinary expenses, animal use issues and considerable clean-up and disposal. We describe an alternative method of training, using an in vitro physiologic model designed to simulate various pathophysiologic states. In addition, the in vitro physiologic model may be used to evaluate membrane lung characteristics. This model's ease of construction, maintenance and use for training compared with live animal techniques are discussed. Research capabilities may be more flexible than with the use of the live animal technique. The in vitro physiologic model can be a useful and convenient asset to an extracorporeal membrane oxygenation/extracorporeal carbon dioxide removal (ECMO/ECCO2R) program.

Long-term assessment of lung function in survivors of severe ARDS

STUDY OBJECTIVES

To investigate the long-term outcome of lung function in survivors of severe ARDS after modern treatment strategies including lung protective mechanical ventilation and prone positioning maneuvers.

DESIGN

Follow-up cohort study.

SETTING

University hospital pulmonary division and level 1 trauma center.

PATIENTS

Sixteen survivors of severe ARDS (from 1992 to 1994) with a lung injury score > or = 2.5.

MEASUREMENTS

The follow-up study (from 1995 to 1996) included interview, physical examination, chest radiographs, static and dynamic lung volumes, diffusion capacity of the lung for carbon monoxide (DLCO), blood gas analysis, and cardiopulmonary exercise testing (CPET).

RESULTS

The mean +/- SD interval between hospital discharge and functional assessment was 29.5 +/- 8.7 months (range, 15.0 to 40.7 months). In approximately one half of the patients, mild abnormalities in static and dynamic lung volumes were found. In 25% (4 of 16 patients), lung function was obstructive; in 25% (4 of 16 patients), lung function was restrictive; and in 6.3% (1 of 16 patients), a combined obstructive-restrictive pattern was revealed. DLCO was impaired in 12.5% (2 of 16 patients); gas exchange during exercise was impaired in 45.5% (5 of 11 patients).

CONCLUSIONS

Residual obstructive and restrictive defects as well as impaired pulmonary gas exchange remain common after severe ARDS. CPET is a very sensitive measure to evaluate residual impairment of lung function after ARDS. Using CPET, reduced pulmonary gas exchange can be detected in many patients with normal DLCO.

Effects of sustained inflation and postinflation positive end-expiratory pressure in acute respiratory distress syndrome: focusing on pulmonary and extrapulmonary forms

OBJECTIVE

To investigate whether the response to sustained inflation and postinflation positive end-expiratory pressure varies between acute respiratory distress syndrome with pulmonary (ARDS(exp)) and extrapulmonary origin (ARDS(exp)).

DESIGN

Prospective clinical study.

SETTING

Multidisciplinary intensive care unit in a university hospital.

PATIENTS

A total of 11 patients with ARDS and 13 patients with ARDS.

INTERVENTIONS

A 7 ml/kg tidal volume, 12-15 breaths/min respiratory rate, and an inspiratory/expiratory ratio of 1:2 was used during baseline ventilation. Positive end-expiratory pressure levels were set according to the decision of the primary physician. Sustained inflation was performed by 45 cm H2O continuous positive airway pressure for 30 secs. Postinflation positive end-expiratory pressure was titrated decrementally, starting from a level of 20 cm H2O to keep the peripheral oxygen saturation between 92% and 95%. Fio2 was decreased, and baseline tidal volume, respiratory rate, inspiratory/expiratory ratio were maintained unchanged throughout the study period.

MEASUREMENTS AND MAIN RESULTS

Blood gas, airway pressure, and hemodynamic measurements were performed at the following time points: at baseline and at 15 mins, 1 hr, 4 hrs, and 6 hrs after sustained inflation. After sustained inflation, the Pao2/Fio2 ratio improved in all of the patients both in ARDS(p) and ARDS(exp). However, the Pao2/Fio2 ratio increased to >200 in four ARDS(p) patients (36%) and in seven ARDS(p) patients (54%). In two of those ARDS patients, the Pao2/Fio2 ratio was found to be <200, whereas none of the ARDS(p) patients revealed Pao2/Fio2 ratios of <200 at the 6-hr measurement. Postinflation positive end-expiratory pressure levels were set at 16.7 +/- 2.3 cm H O in ARDS(p) and 15.6 +/- 2.5 cm H2O in ARDS. The change in Pao /Fio ratios was found statistically significant in patients with ARDS(p) (p =.0001) and with ARDS(p) (p =.008). Respiratory system compliance increased in ARDS patients (p =.02), whereas the change in ARDS was not statistically significant.

CONCLUSIONS

Sustained inflation followed by high levels of postinflation positive end-expiratory pressure provided an increase in respiratory system compliance in ARDS; however, arterial oxygenation improved in both ARDS forms.

Acute respiratory distress syndrome: imaging of the injured lung

In patients with the acute respiratory distress syndrome (ARDS), there is non-specific but widespread exudation of oedema and inflammatory fluid into the lungs. The clinical corollary (dyspnoea, refractory hypoxia, reduced pulmonary compliance and diffuse pulmonary infiltrates) is catastrophic and generally associated with a poor outcome. Imaging is integral to the care of these critically ill patients on the intensive care unit. In the present review, the radiological changes on plain radiography and computed tomography (CT) in patients with ARDS are discussed. Particular attention is directed at the appearances on CT: the relationships between CT features, histopathological changes and the inevitable alterations in pulmonary physiology are explored.

At surfactant deficiency, application of "the open lung concept" prevents protein leakage and attenuates changes in lung mechanics

OBJECTIVE

To evaluate whether mechanical ventilation using "the open lung concept" during surfactant depletion can attenuate the deterioration in pulmonary function.

DESIGN

Experimental, comparative study.

SETTING

Research laboratory of a large university.

SUBJECTS

Eighteen adult male Sprague-Dawley rats, weighing 280-340 g.

INTERVENTIONS

Twelve rats were anesthetized, mechanically ventilated with 100% oxygen, and randomly divided into two groups (n = 6 each). The open lung group underwent six saline lavages at different ventilator settings that prevented alveolar collapse. The settings (expressed as frequency/peak inspiratory pressure/positive end-expiratory pressure/inspiratory:expiratory ratio) were 30/26/6/1:2 during the first lavage, 100/27/10/1:1 during the next two lavages, and 100/33/15/1:1 during the last three lavages and during the remaining ventilation period. The ventilated control group underwent six saline lavages with settings at 30/26/6/1:2. After the lavages, peak inspiratory pressure and positive end-expiratory pressure were increased in this group by 2 cm H2O each for the remaining study period. An additional group of six animals were killed immediately after induction of anesthesia and served as healthy controls. Blood gases were measured before lavage, immediately after the last lavage, and thereafter hourly. At the end of the 4-hr study period, we constructed pressure-volume curves from which we determined total lung capacity at a distending pressure of 35 cm H2O (TLC35). Subsequently, total lung volume at a distending pressure of 5 cm H2O (V5) was determined, followed by bronchoalveolar lavage.

RESULTS

In the ventilated control group, PaO2, V5, and TLC35 were significantly decreased and protein concentration of bronchoalveolar lavage was significantly increased compared with the healthy control group. In the open lung group, PaO2 did not decrease after the lavage procedure, and V5, TLC35, and the protein concentration of bronchoalveolar lavage were comparable with the healthy controls.

CONCLUSION

We conclude that application of the open lung concept during surfactant depletion attenuates deterioration in pulmonary function.

Use of recruitment maneuvers and high-positive end-expiratory pressure in a patient with acute respiratory distress syndrome

OBJECTIVE

To present the use of a novel high-pressure recruitment maneuver followed by high levels of positive end-expiratory pressure in a patient with the acute respiratory distress syndrome (ARDS).

DESIGN

Observations in one patient.

SETTING

The medical intensive care unit at a tertiary care university teaching hospital.

PATIENT

A 32-yr-old woman with severe ARDS secondary to streptococcal sepsis.

INTERVENTIONS

The patient had severe gas exchange abnormalities because of acute lung injury and marked lung collapse. Attempts to optimize recruitment based on the inflation pressure-volume (PV) curve were not sufficient to avoid dependent lung collapse. We used a recruitment maneuver using 40 cm H2O of positive end-expiratory pressure (PEEP) and 20 cm H2O of pressure controlled ventilation above PEEP for 2 mins to successfully recruit the lung. The recruitment was maintained with 25 cm H2O of PEEP, which was much higher than the PEEP predicted by the lower inflection point (P(Flex)) of the PV curve.

MEASUREMENTS AND MAIN RESULTS

Recruitment was assessed by improvements in oxygenation and by computed tomography of the chest. With the recruitment maneuvers, the patient had a dramatic improvement in gas exchange and we were able to demonstrate nearly complete recruitment of the lung by computed tomography. A PV curve was measured that demonstrated a P(Flex) of 16-18 cm H2O.

CONCLUSION

Accumulating data suggest that the maximization and maintenance of lung recruitment may reduce lung parenchymal injury from positive pressure ventilation in ARDS. We demonstrate that in this case PEEP alone was not adequate to recruit the injured lung and that a high-pressure recruitment maneuver was required. After recruitment, high-level PEEP was needed to prevent derecruitment and this level of PEEP was not adequately predicted by the P(Flex) of the PV curve.

Acute respiratory distress syndrome: CT abnormalities at long-term follow-up

PURPOSE

To document abnormalities at computed tomography (CT) in adult survivors of acute respiratory distress syndrome (ARDS), to determine the relationships between CT patients during the acute phase and at follow-up, and to assess the effects of mechanical ventilation on the development of CT abnormalities.

MATERIALS AND METHODS

Thin-section CT scans were obtained during the acute illness and at follow-up in 27 patients with ARDS. The extent and distribution of individual CT patterns were independently analyzed.

RESULTS

At follow-up CT, a reticular pattern was the most prevalent (23 patients [85%]) and extensive CT abnormality, with a striking anterior distribution (more anterior distribution than posterior distribution, P < .001). A reticular pattern at follow-up was inversely correlated with the extent of intense parenchymal opacification on scans obtained during the acute illness (Spearman r = -0.26; P < .001). The extent of a reticular pattern at follow-up CT was independently related to the total duration of mechanical ventilation (P = .02) but was most strongly related to the duration of pressure-controlled inverse-ratio ventilation (P < .001).

CONCLUSION

A reticular pattern, with a striking anterior distribution, is a frequent finding of follow-up CT in ARDS survivors and is most strongly related to the duration of pressure-controlled inverse-ratio ventilation.

High-level positive end expiratory pressure management in the surgical patient with acute respiratory distress syndrome

Although the exact incidence of ARDS is not know, it is frequently reported that there are 150,000 cases in the United States each year. Despite major advances in medical and respiratory intensive care, the mortality for patients with ARDS remains exceedingly high and has not changed appreciably from the 50% to 75% reported during the last 25 years. Currently there is no widespread, acceptable, specific therapeutic approach or agent available for the prevention or treatment of ARDS. Clinical management remains entirely supportive in nature. Although most practitioners agree that patients with severe ARDS require mechanical ventilation to maintain adequate gas exchange, controversies center on the amount of supplemental oxygen, level of positive end expiratory pressure (PEEP), and mode of ventilation needed to increase patient survival but reduce ventilator-associated complications. This review provides supportive evidence for the use of high-level PEEP (more than 15 cm H20) in the care of the surgical patient with severe ARDS.

Severe pulmonary dysfunction following acute respiratory distress syndrome

Recovery of lung function following the acute respiratory distress syndrome (ARDS) is thought to be related to the severity of the initial insult. We report a case demonstrating virtually complete functional recovery following severe ARDS. The significance of this and the need for comprehensive follow-up of such patients is discussed.

High-inflation pressure and positive end-expiratory pressure. Injurious to the lung? No

Survival rates in ARDS with conventional ventilation using high oxygen fractions and low PEEP levels have been reported to be less than 10%. In three prospective evaluations of ARDS in the 1980s, mortality rates remained greater than 60%. Early studies using high-level PEEP therapy in severe ARDS by Douglas, Downs, Kirby, and Civetta showed improved survival rates with ranges between 60% and 80%. In 1979 Gallagher reviewed 59 patients with ARDS who were treated with PEEP greater than 15 cm H2O titrated to improve FRC by achieving an intrapulmonary shunt fraction of 15%. The overall survival was 65%, with only 5% of the patients dying secondary to respiratory failure. In the more recent study by Miller in trauma patients and later by DiRusso in a variety of surgical patients, the overall mortality rate for those patients receiving PEEP greater than 15 cm H2O was 20% to 30%. Of the 14 patients who died, only seven (10% of the total) succumbed to respiratory failure. The remaining patients died from the primary underlying disease with normal oxygenation or after significant weaning from high PEEP levels. By using a goal-oriented approach to the management of patients with severe ARDS, we have found that high-level PEEP therapy was effective in lowering the intrapulmonary shunt and improving the SaO2 at acceptable levels of inspired oxygen. All of these patients were ventilated with traditional high tidal volumes (10 to 15 mL/kg) and therefore exhibited high peak inspiratory airway pressures. This support method did not seem to cause lung injury or an excessive amount of barotrauma in these patients, but in fact, was associated with a lower mortality rate (30%) than reported in other studies of patients with lesser degrees of lung oxygenation dysfunction and extrapulmonary organ system dysfunction. Currently available information indicates that increases in mean airway pressure (induced with PEEP or other modes of ventilatory support to restore losses in FRC that occur during ARDS) and limiting exposure to toxic concentrations of oxygen minimize ventilator-induced secondary lung injury and maximize chances for survival. Arbitrary limitations of peak inspiratory or end-expiratory airway pressure or mandatory tidal volume in patients with severe ARDS seem to be unfounded. Failure to achieve adequate physiologic end-points in these patients may increase morbidity and mortality rates.

Survival in patients with severe adult respiratory distress syndrome treated with high-level positive end-expiratory pressure

OBJECTIVE

To assess the mortality rate and complications in a population of surgical patients with severe adult respiratory distress syndrome (ARDS) treated with positive end-expiratory pressure (PEEP) of > 15 cm H2O in an attempt to reduce intrapulmonary shunt to approximately 0.20 and reduce FIO2 to < 0.50.

DESIGN

Retrospective review of patients treated by a standardized ventilatory support protocol at the time of their illness.

SETTING

A 24-bed surgical intensive care unit in a university medical center.

PATIENTS

All patients admitted to the surgical intensive care unit during a 34-month period who met the criteria for severe ARDS (Pao2 of < or = 70 torr [< or = 9.3 kPa] on an FIO2 of > or = 0.50, diffuse interstitial and/or alveolar infiltrates on chest radiograph, decreased lung compliance, no evidence of congestive heart failure, and a likely predisposing etiology) were evaluated. Patients treated with PEEP of > 15 cm H2O were selected for this review.

INTERVENTIONS

Patients were treated by a protocol to achieve oxygenation end points, which consisted of maintaining arterial oxyhemoglobin saturation (as determined by pulse oximetry of > or = 0.92), while reducing FIO2 to < 0.50 and decreasing intrapulmonary shunt fraction to < or = 0.20 by adding PEEP. With the exception of patients with suspected intracranial hypertension related to closed-head injury, low-rate intermittent mandatory ventilation was the primary mode of ventilation. Pressure-support ventilation was added, when needed, to improve patient comfort, enhance spontaneous tidal volume, or improve CO2 excretion.

MEASUREMENTS AND MAIN RESULTS

Eighty-six patients with severe ARDS were treated with a PEEP of > 15 cm H2O. Nineteen of these patients died early of severe closed-head injury or massive uncontrollable hemorrhage and were excluded from the evaluation. The remaining 67 patients had a mean Lung Injury Score of 3.3 during their treatment with high PEEP. Twenty (30%) of 67 patients died. Eight of the deaths occurred after decrease of ventilatory support and with acceptable blood gases. The other 12 patients who died had continued oxygenation deficits and received increased levels of ventilatory support at the time of death. Twenty-six (39%) of 67 patients had radiographic manifestations of barotrauma (pneumothorax, subcutaneous emphysema, etc.) related to their primary injuries or to complications related to central venous catheter placement. Seven (17%) of 41 patients developed clinical or radiographic signs of barotrauma while receiving high-level PEEP. The hemodynamic effects of increased airway pressure were managed with fluids and inotropic agents, when necessary, and did not limit the application of PEEP to reach the defined end point of treatment.

CONCLUSIONS

This subset of patients with severe ARDS treated with high-level PEEP had a mortality rate lower than those rates previously reported by other researchers using more conventional ventilatory support and resuscitation techniques. FIO2 may be significantly reduced and PaO2 may be maintained at acceptable values by decreasing intrapulmonary shunt fraction using high-level PEEP.

Low blood flow extracorporeal carbon dioxide removal (ECCO2R): a review of the concept and a case report

Despite advances in respiratory and critical care medicine, the mortality from ARDS remains unchanged. Recent research suggests current ventilatory therapy may produce additional lung injury, retarding the recovery process of the lung. Alternative supportive therapies, such as ECMO and ECCO2R, ultimately may result in less ventilator induced lung injury. Due to the invasiveness of ECMO/ECCO2R, these modalities are initiated reluctantly and commonly not until patients suffer from terminal or near-terminal respiratory failure. Low flow ECCO2R may offer advantages of less invasiveness and be suitable for early institution before ARDS becomes irreversible. We describe a patient with ARDS and severe macroscopic barotrauma supported with low flow ECCO2R resulting in significant CO2 clearance, reduction of peak, mean airway pressures and minute ventilation.

Sequelae of the adult respiratory distress syndrome

Most survivors of ARDS have persistent mild reductions of TLCO even as long as a year after their episode. The lung volumes and flows return to normal in most instances, although a subset of patients will have persistent impairment. Both obstructive and restrictive deficits may be seen. This group may be predicted by the degree of acute lung injury assessed by the level of FIO2, PEEP, and gas exchange abnormality that exists in the first few days. In the first year after ARDS most physiological abnormalities will improve, but if deficits persist at one year further improvement is unlikely. Although many patients report dyspnoea following ARDS, the symptom does not correlate with abnormalities of pulmonary function. The possibility that conventional management may augment the degree of acute injury and worsen outcome must be considered. The effects of chronic hyperoxia in humans with acute lung injury or those of high levels of PEEP compared with low levels are not known. Exploring new ventilator management strategies while we await more specific treatment directed at the primary problem of acute lung inflammation will hopefully reduce acute mortality as well as acute and chronic morbidity.

Open lung biopsy does not correlate with pulmonary function after the adult respiratory distress syndrome

Abnormalities of pulmonary function occur following the adult respiratory distress syndrome (ARDS). To determine if open lung biopsy (OLB) during ARDS predicts late pulmonary function abnormalities, we examined nine survivors of ARDS who had OLB during ARDS. Open lung biopsy was performed within two weeks of the diagnosis of ARDS, and the following were scored by a pulmonary pathologist as to extent and severity: hyaline membranes (HM), interstitial fibrosis (IF), air space organization (AO), interstitial cellularity (IC), and type 2 cell proliferation (T2C). Pulmonary function tests performed at least one year after ARDS were also used for analysis. Percent predicted Dco, TLC, DL/VA, and FVC were regressed against extent, severity, and combined scores. No significant correlation was found despite impressive histologic abnormalities. These data suggest that the severity and extent of HM, IF, AO, T2C, or IC do not correlate with lung function following ARDS.

Extracorporeal gas exchange in adult respiratory distress syndrome: associated morbidity and its surgical treatment

Extracorporeal carbon dioxide removal (ECCO2-R) over a membrane lung is a new therapy for patients with adult respiratory distress syndrome (ARDS) who frequently suffer from lung complications caused by long-term artificial ventilation and who may require major thoracic surgery. This is a report of 76 patients with severe ARDS who were treated by ECCO2-R. Twenty-six of these 76 patients required thoracotomy: 19 for pneumothorax and pneumatocele, and seven for haemothorax, infected lung necrosis or oesophagotracheal fistula. Most pneumothoraces were bilateral. Ten of these 26 patients required reoperation, usually for extensive persisting alveolar air leaks. Sixteen (62 per cent) of the 26 patients who had a thoracotomy and 22 (44 per cent) of the 50 patients without surgery survived. These results demonstrate that performing a thoracotomy, if necessary, does not diminish the survival chance of high-risk patients with severe ARDS.

Adult respiratory distress syndrome in pediatric patients. II. Management

Adult respiratory distress syndrome, a clinical syndrome of respiratory failure that follows many kinds of insults, often in patients with no previous pulmonary disease, occurs in pediatric patients. This group of disorders has a typical clinical, pathologic, and pathophysiologic course, the hallmark of which is injury to the alveolar-capillary membrane with increased permeability of the pulmonary vasculature and pulmonary edema. Resolution may occur at any stage, but most patients die and many develop chronic lung disease requiring respiratory support for weeks or months. Multiple organ system failure, secondary infection, and irreversible respiratory dysfunction are responsible for the poor outcome. The underlying mechanisms that relate injury to the development of pulmonary disease are unclear. In some cases there may be direct injury to the lung, but in others, such as septic shock, there are mediators that link the initial insult to the subsequent lung injury. The leukocyte may have a central role in this process, although this is uncertain. Therapeutic measures needed to support the patient, especially increased inspired oxygen, are additional factors in the progression of lung disease. Current therapy, as summarized in Table II, is primarily supportive. Efforts to treat ARDS after it is clinically apparent have been disappointing. The pathogenic mechanisms that lead to ARDS are probably well advanced by the time the syndrome is diagnosed on the basis of the usual clinical signs. Therefore an emphasis on understanding the mechanisms of lung injury so that specific markers can be used to predict which patients will develop ARDS, allowing intervention in the early stages of the process, may prove rewarding.

Intermittent and continuous positive-pressure ventilation in the prophylaxis of endotoxin-induced lung insufficiency. A study in pigs

The effects of intermittent and continuous positive-pressure ventilation (IPPV and CPPV) instituted prophylactically were evaluated in a porcine model of endotoxin-induced pulmonary and cardiovascular failure. Pigs under ketamine anaesthesia were infused i.v. with E. coli endotoxin over 6 h. Twenty animals, breathing air spontaneously, received endotoxin without treatment. Fifteen animals were treated prophylactically with IPPV (normoventilation with air). Nine animals received prophylactic treatment with CPPV (positive end-expiratory pressure 0.8 kPa (8 cmH2O). Endotoxin infusion in spontaneously breathing animals caused profound deterioration of pulmonary gas exchange, a marked rise in pulmonary vascular resistance (PVR) and a moderate increase in extravascular lung water (EVLW). Cardiac output (Qt) and O2 delivery decreased considerably. Metabolic acidosis indicated oxygen deficit. Eleven of 20 animals died during the observation period. IPPV improved arterial oxygenation during endotoxin infusion, and the increase in EVLW tended to be lower. The alterations in pulmonary haemodynamics, Qt and O2 delivery, were of the same magnitude as in spontaneously breathing animals. Survival was improved. CPPV fully prevented the deterioration in pulmonary gas exchange and the development of pulmonary oedema. There was an accentuated increase in PVR. Qt and O2 delivery decreased markedly and a severe metabolic acidosis developed. All animals treated with CPPV died during the observation period. These results indicate that prophylactic IPPV and CPPV may counteract the development of sepsis-induced lung insufficiency in man. However, it must be emphasized that adequate cardiovascular support is essential in optimizing the treatment.

Specific coagulation and fibrinolysis tests as biochemical markers in traumatic-induced adult respiratory distress syndrome

There is a great demand for more specific methods for assaying individual components of coagulation and fibrinolysis, with the chief aim being to use them as biochemical markers of the Adult Respiratory Distress Syndrome (ARDS) induced by severe trauma. This prospective study was undertaken on 18 severely traumatized patients in various stages of shock admitted to the Intensive Care Unit of the University Hospital in Uppsala, Sweden. After haemodynamic restitution, during which surgery was often required as an intervening procedure, the patients were carefully studied regarding pulmonary function, coagulation and fibrinolysis. Eight patients developed ARDS according to our criteria, and one patient died from this condition. It was found that patients who developed ARDS had significantly lower levels of antithrombin-III, higher levels of von Willebrand factor levels, higher levels of tissue plasminogen activator inhibitors and lower levels of plasminogen as compared with those who did not develop this condition. We believe that these coagulation and fibrinolysis variables can be used along with appropriate pulmonary function tests as specific biochemical markers to disclose the development of traumatic-induced ARDS.

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.

Acute miliary blastomycosis presenting as fluminating respiratory failure

A patient with miliary blastomycosis had acute fulminating respiratory failure requiring prolonged external ventilatory support. Treatment consisted of antifungal chemotherapy with two drugs and administration of corticosteroids. Restrictive ventilatory impairment and exercise-induced hypoxemia persist at one year after completion of therapy.