Reduced pulmonary capillary blood volume as a long-term sequel of ARDS

1-year pulmonary function and health status in survivors of severe acute respiratory syndrome

Study objectives

To characterize the long-term pulmonary function and health status in a prospectively identified cohort of patients who survived the severe acute respiratory syndrome (SARS).

Design

Prospective follow-up cohort study.

Setting

University-affiliated hospital.

Patients

Ninety-four patients who recovered from SARS were assessed at a uniform time point of 1 year after hospital discharge.

Measurements

The study included the measurement of static and dynamic lung volumes, the determination of the diffusing capacity of the lung for carbon monoxide (Dlco), and a health status evaluation using the St. George Respiratory Questionnaire (SGRQ).

Results

Eleven patients (12%) had mild impairment of FVC, 20 (21%) had mild impairment of FEV₁, 5 (5%) had mild impairment of the FEV₁/FVC ratio, and 17 (18%) had mild impairment of the Dlco. There was one patient (1%) who had moderate impairment of FVC, one patient (1%) who had moderate impairment of the FEV₁/FVC ratio, and three patients (3%) who had moderate impairment of the Dlco. No pulmonary function abnormalities were detected in 59 patients (63%). Mean scores were significantly higher (ie, worse) than the population norms in the activity (p < 0.001), impacts (p < 0.001), and total (p < 0.001) domains of the SGRQ.

Conclusions

One year after recovery from SARS, persistent pulmonary function impairment was found in about one third of patients. The health status of SARS survivors was also significantly worse compared with the healthy population. The main determinants of morbidity in recovered SARS patients need to be further defined.

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.

Alveolar basement membrane breaks down in diffuse alveolar damage: an immunohistochemical study

Sequential structural changes of the alveoli in diffuse alveolar damage (DAD) were examined by immunohistochemical methods. Lung specimens obtained at autopsy from 52 patients with DAD were stained with antibodies to laminin, 7S collagen (7S) and type IV collagen (type IV) for alveolar basement membrane, to von Willebrand factor, CD-31 and thrombomodulin (TM) for the alveolar capillary endothelial cell, and to epithelial membrane antigen and surfactant apo-protein (PE-10) for the alveolar epithelium. Forty-two of the patients had the exudative form of DAD; 10 of the patients had the proliferative form of DAD. The results were summarized as follows: (i) laminin was most easily impaired both in the epithelial and capillary basement membrane in the early exudative stage; (ii) following laminin, 7S and type IV in the capillary basement membrane were also injured in the early exudative stage, and recovered in the proliferative stage; (iii) subsequently, 7S and type IV in the epithelial basement membrane were also impaired in the late exudative stage, and remained impaired even in the proliferative stage; and (iv) alveolar epithelium regenerated almost completely in the late exudative stage, but staining for TM in the alveolar capillary recovered in the proliferative stage. Because the alveolar basement membrane must govern the homeostasis of alveolar tissue architecture, it was concluded that its preservation is necessary to avoid the abnormal remodeling of the alveoli in the reparative stage of DAD, if the patient survives the acute episodes of the disease.

Upper airway obstruction following adult respiratory distress syndrome. An analysis of 30 survivors

To evaluate the effects of current supportive care measures for the adult respiratory distress syndrome (ARDS) upon the upper airway, we studied 30 survivors of ARDS. All patients were interviewed and examined and performed inspiratory and expiratory maximal flow-volume curves more than six months after the onset of ARDS. Three women had developed symptomatic upper airway obstruction due to laryngotracheal stenosis 4 to 12 months after discharge from the hospital. Potential etiologic factors included difficult orotracheal intubation (one) and high tracheal cuff pressures (one). The three survivors who developed laryngotracheal stenoses did not differ from the 27 survivors of ARDS without symptomatic upper airway obstruction with respect to age, duration of tracheal intubation, or maximum level of positive end-expiratory pressure. Each patient with upper airway obstruction required more than one operation for laryngotracheal reconstruction. Although corrective surgery improved airflow, two survivors of ARDS had upper airway obstruction and exertional dyspnea more than five years after the ARDS. We conclude that upper airway obstruction is an important cause of dyspnea and impairment following ARDS. Exertional dyspnea weeks to months following treatment for ARDS suggests the possibility of laryngotracheal stenosis.

Pulmonary occlusion (wedge) angiography in adult respiratory distress syndrome. A survey of angiographic appearances and outcomes

Pulmonary occlusion angiography was performed in 34 patients admitted to the intensive therapy unit with a diagnosis of adult respiratory distress syndrome. Twenty angiograms were normal. Ten patients survived. No patient with abnormal angiography survived.