Biomedical subjects
Publications and source records attributed to D J Pierson.
This article discusses pneumothorax and barotrauma from the viewpoints of both the intensivist/pulmonologist and the emergency room physician because both groups of clinicians frequently encounter these potentially life-threatening conditions. The discussion focuses primarily on pneumothorax and barotrauma as they occur in adults rather than in neonates and children.
Bronchopleural fistula occurring as a complication in patients with the adult respiratory distress syndrome typically appears after 1 to 2 wks of illness, and is associated with a poor prognosis. Whether the bronchopleural fistula per se worsens outcome is not known because of the lack of studies on its natural history. There are several potential adverse effects of bronchopleural fistula in adult respiratory distress syndrome (e.g., incomplete lung expansion, loss of effective tidal volume or positive end-expiratory pressure, inability to remove CO2, etc.), but the actual frequency of these problems among patients with this complication appears to be low, and their magnitude and clinical impact remain uncertain. Most of the literature consists of anecdotal reports of innovative measures for reducing the leak, such as manipulation of chest tube suction, high-frequency jet ventilation, independent lung ventilation, and various maneuvers using the fiberoptic bronchoscope. Controlled studies are lacking, however, and the application of sound, general management principles is of primary importance. The great majority of patients can be managed satisfactorily without resort to unfamiliar, labor-intensive, potentially hazardous measures.
High frequency jet devices are not only used as 'internal percussors' to aid clearance of pulmonary secretions, but are also a mode of ventilatory support. As physical stimuli can cause bronchospasm in asthmatic individuals, we hypothesized that direct airway vibration may induce bronchospasm. To ascertain whether an airway vibration jet device could cause bronchoconstriction, we exposed eight asthmatic and six normal subjects to 5 min of jet-induced airway vibration or placebo treatment with cross-over at 3 h. Subjects breathed spontaneously for 5 min through an open mouthpiece into which either jet (10 Hz, 25 psi) or sham pulsations (same device, pressure vented to room at compressor) were delivered in a double-blind, random order. A constant-volume body plethysmography measured functional residual capacity and specific airway conductance (SGAW) and a water seal spirometer measured forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC). These pulmonary function measurements were taken before and at 5, 10, 20, 30, 60, 90 and 120 min after each exposure. In the normal subjects there was no significant change in any pulmonary function. There was not statistically significant change in the pulmonary function in the asthmatic patients. However, the oral high frequency oscillator induced a clinical asthmatic attack in one asthmatic patient. In this one patient, the FEV1 fell 35% from its initial value at 5 min following exposure to a maximum of 49% decline from initial value at 1 h following exposure.(ABSTRACT TRUNCATED AT 250 WORDS)
Sputum induction (SI) is a sensitive and specific method for diagnosing Pneumocystis carinii pneumonia (PCP) in patients with AIDS. Although less expensive than bronchoscopy with bronchoalveolar lavage (BAL), SI followed by BAL does not necessarily reduce costs compared with BAL alone. Cost analysis demonstrates that the cost of diagnosing PCP is dependent on the prevalence of PCP (PCPprevalence) in the studied population, the sensitivity of SI (SIsensitivity) for diagnosing PCP, and the relative costs of SI and BAL (SIcost and BALcost) for diagnosing PCP. In any given clinical setting, SI reduces the cost of diagnosing PCP if (PCPprevalence)(SIsensitivity) greater than SIcost/BALcost. A graphic approach relating these parameters is also presented. Evaluation of reported PCPprevalence and SIsensitivity from recent literature illustrates that SI is not always the least costly method for diagnosing PCP. Cost reduction is not the only measure of a diagnostic procedure's value, and other aspects, such as discomfort, availability, risks, and patient prognosis, must be considered. The cost analysis approach used in this study identifies those variables that can be manipulated to reduce the cost of diagnosing PCP.
Pneumonia is common among patients with artificial airways in place. Most prior studies of such pneumonia involve a heterogeneous group of patients, usually with major medical or surgical illnesses. We studied the incidence of pneumonia in a group of patients with isolated closed head injury (CHI) in an effort to determine the pattern of the problem in the absence of other injuries and to determine whether the pattern of development of pneumonia in these patients was comparable to that in more heterogeneous groups of mechanically ventilated patients. We studied 109 initially comatose patients with isolated CHI who were ventilated 24 h or more. The mean age was 30.3 +/- 20.2 yr, 72% were male, and the admission Glasgow coma score was 4.9T +/- 1.4. Overall, 45 patients (41%) developed pneumonia, with the majority (29/45) occurring during the first 3 days of hospitalization. No patient developed pneumonia after the first week despite the fact that many were still ventilated, others remained intubated, and yet others were extubated but comatose. Patients who developed pneumonia experienced a longer ICU stay (10.5 +/- 5.4 days versus 7.2 +/- 4.3 days, p = 0.001) and hospital stay (34.8 +/- 27.6 versus 22.5 +/- 20.2 days, p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Cholinergically induced bronchoconstriction is thought to be a major cause of bronchospasm during anesthesia. We used tracheally intubated rabbits (4-mm endotracheal tube) stimulated with methacholine to assess the efficacy of beta-adrenergic agonist and anticholinergic treatment in reversing the increases in respiratory system resistance. Four groups were compared: (a) inhaled metaproterenol, 20 puffs via metered dose inhaler (0.65 mg/puff); (b) inhaled ipratropium bromide, 20 puffs from a metered dose inhaler (18 micrograms/puff); (c) 2 mg of intravenous atropine; and (d) no treatment after methacholine challenge as a control group. Methacholine increased respiratory system resistance from 0.041 +/- 0.001 (mean +/- SEM) to 0.098 +/- 0.006 cm H2O.mL-1.s-1 (P < 0.001). Whereas beta-adrenergic agonist treatment was ineffective in ameliorating bronchoconstriction, inhaled ipratropium bromide and atropine were highly effective, causing an 86%-88% reversal in the methacholine-induced increase in respiratory system resistance. Both these agents were also effective in improving dynamic compliance. We conclude that inhaled ipratropium bromide is effective in treating cholinergic bronchospasm even when administered via a small endotracheal tube and that the beta-adrenergic agonist metaproterenol is ineffective in rabbits in the face of maximal cholinergic stimulation.
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Portable pulse oximeters are now widely available for the assessment of arterial oxygenation, and the U.S. Medicare program considers saturation readings to be acceptable substitutes for arterial PO2 in selecting patients for long-term oxygen therapy (LTOT). Current oximeters are reasonably accurate (plus or minus 4 or 5 percent of the co-oximetry value), but the clinician should be aware of several potential problems. Readings may be inaccurate in the presence of hemodynamic instability, carboxyhemoglobinemia, jaundice, or dark skin pigmentation, and also during exercise. Indicated saturation may substantially overestimate arterial PO2 if the patient is alkalemic. Pulse oximetry cannot detect hypercapnia or acidosis. For these and other reasons, pulse oximetry should not be used in initial selection of patients for LTOT, as a substitute for arterial blood gas analysis in the evaluation of patients with undiagnosed respiratory disease, during formal cardiopulmonary exercise testing, or in the presence of an acute exacerbation. Pulse oximetry is an important addition to the clinician's armamentarium, however, for titrating the oxygen dose in stable patients, in assessing patients for desaturation during exercise, for sleep studies, and for in-home monitoring.
A constellation of adverse effects and complications may be associated with mechanical ventilation, although in many instances the causal role of the ventilator itself has not been established. Complications occur with greater frequency than is generally appreciated, and tend to be under-reported in the medical literature. Among the potential adverse physiologic effects of positive-pressure ventilation are decreased cardiac output, unintended respiratory alkalosis, increased intracranial pressure, gastric distension, and impairment of hepatic and renal function. Failure of the ventilator to cycle, of safety alarms to function properly, and of inspired gas to be properly heated or humidified are examples of equipment-related complications. Perhaps most feared among medical complications occurring during mechanical ventilation are pneumothorax, bronchopleural fistula, and the development of nosocomial pneumonia; these entities may owe as much to the impairment of host defenses and normal tissue integrity as to the presence of the ventilator per se. Finally, a variety of avoidable "misadventures," due primarily to lapses of understanding and communication among the physicians, nurses, and respiratory care practitioners managing the ventilated patient, can adversely affect comfort, morbidity, and ultimate outcome.
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Home respiratory care (provision of respiratory care services in patients' homes rather than in institutions or providers' offices) includes long-term oxygen therapy and home ventilatory assistance. I review the selection of patients, the role of physicians and other health care professionals, the types of equipment used, the administrative structures, and sources of payment or reimbursement in different countries. Because more has been published about home respiratory care in France and the United States, current practices in these two countries are reviewed in some detail; where available, information about long-term oxygen therapy and home ventilatory assistance in other countries is also included. As these and other modalities become more firmly established both scientifically and in clinical practice, and as technological advances continue to be introduced, home respiratory care will probably be made available to more patients, and in an increasing number of countries. Physicians, other health care workers, representatives of industry, administrative agencies, and those responsible for payment or reimbursement should work together to provide the best possible care of patients with chronic respiratory insufficiency.
To clarify the clinical value of the International Labor Office (ILO) roentgenographic classification of pneumoconiosis in assessing asbestos-exposed persons, we determined the relationships among spirometric values, radiographic evidence of parenchymal pulmonary fibrosis and/or pleural thickening, and cigarette smoking history in 684 consecutively enrolled male plumbers and pipefitters participating in a larger cross-sectional prevalence study. The subjects were mainly marine pipefitters (35%), plumbers (24%), and steamfitters/welders (23%); 28% had never smoked, 39% were ex-smokers, and 33% currently smoked cigarettes. Mean values for FVC and FEV1 were 95.0 and 91.9% of predicted, respectively, with mean FEV1/FVC ratio 77.7%; by standard criteria, 7.8% had restrictive impairment, and 21.7%, obstructive defects. Chest radiographs were normal in 63% and showed pleural abnormalities only in 17%, parenchymal abnormalities only in 7%, and both pleural and parenchymal abnormalities in 12%. Both FVC and FEV1 correlated with the degree of small opacity profusion, as assessed by ILO grade. Pleural abnormalities were associated with lower FVC values, independently of ILO profusion grade for Grades less than or equal to 1/0, and were unexplained by smoking status. In addition, there was a positive association between smoking history and degree of ILO parenchymal abnormality, particularly in those with the heaviest cumulative smoking history. Our results suggest that the ILO classification of pneumoconiosis, although a useful epidemiologic tool, should be applied with caution in persons with asbestos exposure, and that pleural abnormalities may be associated with physiologic impairment in such persons.
Zindotrine, a new bronchodilator, may be an alternative to theophylline in treating reversible airflow obstruction. Efficacy and cardiovascular effects of a single 300 mg oral dose of zindotrine were compared with placebo in a two-period, double-blind, crossover trial. Twelve subjects with airflow obstruction reversible after isoproterenol and theophylline completed the trial. Improvement in pulmonary function (forced vital capacity [FVC], forced expiratory volume in one second, and forced expiratory flow rate from 25 to 75 percent of FVC) was greater after zindotrine than with placebo. Pulmonary function tests increased 15 percent or more over baseline in 30 minutes after active drug, lasting up to 6 hours. Mild decreases in heart rate and mean blood pressure occurred after both treatments, with changes equal in both treatment groups. Six subjects had mild subjective side effects after zindotrine (headache, dizziness, vertigo, flushing, and heartburn) compared with one report of lightheadedness after placebo. A single dose of zindotrine 300 mg provides effective bronchodilator action with a relatively prolonged response and tolerable side effects.
The total lung capacity (TLC) is frequently used as a measure of respiratory impairment in patients with asbestosis. Because asbestosis and chronic obstructive pulmonary disease (COPD) exert opposite effects on the TLC, it may be an insensitive measure of impairment in patients with both abnormalities. To assess this, we compared asbestos-exposed patients with functional evidence of COPD and radiographic evidence of interstitial fibrosis (group 1) to those with interstitial fibrosis alone (group 2). Despite the two groups being comparable in degree of radiographic "fibrosis," no case of restrictive impairment (reduced TLC) was identified among those with both interstitial fibrosis and COPD (group 1), compared to 33 percent of those with interstitial fibrosis alone (group 2). In addition, those patients with both interstitial fibrosis and COPD, compared to those with interstitial fibrosis alone, were found to have greater impairment as measured by alveolar-arterial oxygen difference and diffusing capacity. We conclude that the TLC is an insensitive measure of impairment due to asbestosis in patients with the common setting of coexistent asbestosis and COPD.
Expired gas and gas leaked via thoracostomy tubes was collected in nine patients with the adult respiratory distress syndrome (ARDS) and bronchopleural fistulas. Mean minute ventilation in the group was 23.9 +/- 7.5 L/min with 31 +/- 23 percent of the gas escaping via the leak. Carbon dioxide was present in the leaked gas in every patient, with the fraction of CO2 excreted via the leak highly correlated with the fraction of minute ventilation exiting via the leak (r = 0.86, p less than 0.005). Mean concentration of CO2 in leaked gas was 1.3 +/- 0.5 percent. We conclude that some of the gas leaked via a bronchopleural fistula in such patients participated in gas exchange.
We studied eleven patients during 14 attempts at weaning from mechanical ventilation to determine whether central ventilatory drive, measured as airway occlusion pressure 0.1 s after onset of inspiration (P 0.1), during spontaneous breathing before and during a brief hypercapnic challenge, could accurately predict the success or failure of the attempt. All patients were recovering from acute respiratory failure and could breathe spontaneously for 20 minutes on a T-piece but were judged clinically to be marginal weaning candidates. Minute ventilation (VI) and P 0.1 were measured while breathing spontaneously and were repeated during a hypercapnic challenge that raised end-tidal PCO2 approximately 10 mm Hg. Seven of the 14 weaning attempts were unsuccessful, requiring reinstitution of mechanical ventilation. Although the failure group had lower mean maximum inspiratory force and higher spontaneous respiratory rate, no threshold value separated the failure from the success group. Ventilation increased more during hypercapnic challenge in those patients whose weaning attempt was successful, but overlap of results between the two groups rendered this test inaccurate for predicting weaning success. In contrast, successfully weaned patients had greater augmentation of P 0.1 during hypercapnia, expressed as the ratio of P 0.1 during CO2-stimulated to P 0.1 during baseline values, than did those who failed weaning (p less than 0.005). This ratio succeeded, and was thus both specific and sensitive as a predictor of successful weaning from mechanical ventilation in these patients.