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To determine whether gastric intramural pH (pHi), an indirect measure of gastric mucosal ischemia, can be used to predict the success of weaning from mechanical ventilation. Gastric mucosal ischemia (and, therefore, acidosis) may develop in patients during unsuccessful attempts to wean them from mechanical ventilation because blood flow from nonvital areas (for example, splanchnic bed) is diverted to meet the increased demands of respiratory muscles.Cohort study.Intensive care unit.Twenty-nine patients receiving assisted mechanical ventilation for respiratory failure who were thought by their physicians to be weanable from mechanical ventilation.Simultaneous samples of arterial blood and gastric juice were obtained from patients during assisted mechanical ventilation, as well as during weaning trials. The predictor variable, pHi, was calculated using the following equation: 6.1 + log HCO3/(gastric PCO2 x 0.0307). The outcome was success or failure of weaning, decided by physicians blinded to the study.Patients who could not be weaned from mechanical ventilation had a substantially reduced gastric pHi (7.36 during mechanical ventilation compared with 7.09 during weaning [difference, 0.27; 95% Cl, 0.12 to 0.42; P0.01]). Patients who were successfully weaned from mechanical ventilation showed no change in pHi (7.45 during mechanical ventilation compared with 7.46 during weaning [difference, 0.01; Cl, -0.01 to 0.03; P = 0.29]). The sensitivity and specificity of pHi in predicting weaning success or failure were both 100% (Cl, 81 to 100 and 72 to 100, respectively).Gastrointestinal acidosis may be an early sign of weaning failure. Measurement of pHi, which is simple and rapid, may be of practical value in predicting the likelihood of weaning success or failure during weaning trials.

Objective To compare inhaled pentamidine with intravenous pentamidine for the treatment of Pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome (AIDS). Design A randomized trial. Setting Community teaching hospital and hospital-based outpatient treatment center. Patients Twenty-one homosexual men with pneumocystis pneumonia; 11 received inhaled pentamidine and 10 received intravenous pentamidine. Intervention Inhaled (8 mg/kg body weight) or intravenous (4 mg/kg body weight) pentamidine administered daily for 21 days. Measurements and main results All patients responded to intravenous pentamidine, whereas 6 of 11 (55%; 95% CI, 23% to 83%; P = 0.02, Fisher exact test) responded to inhaled pentamidine therapy. Two patients who failed inhaled pentamidine therapy eventually died despite appropriate intravenous therapy (mortality rate, 18%; CI, -6% to 42%). Nonresponders to inhaled pentamidine had a greater severity of illness compared with responders to this therapy, as shown by a lower mean (+/- SE) Pao2 (8.0 +/- 0.4 kPa compared with 10.8 +/- 0.6 kPa; P = 0.005) and higher alveolararterial Po2 difference (6.8 +/- 0.6 kPa compared with 2.8 +/- 0.8 kPa; P = 0.003). Conclusions Inhaled pentamidine is probably as effective as intravenous pentamidine in patients with mild pneumocystis pneumonia. However, its use as sole therapy in patients with moderate to severe pneumocystis pneumonia is not supported by the results of our study and is not warranted.

To study the relationship between the distribution of pulmonary blood flow, pulmonary ventilation, and pulmonary capillary wedge pressure, we studied six patients with chronic congestive heart failure (CHF) (New York Heart Association classes II and III) at rest and during exercise. We used krypton 81m (81mKr) and technetium 99m (99mTc) to assess lung ventilation and perfusion at rest and during exercise. Hemodynamic measurements were obtained with a balloon floatation thermodilution catheter. At rest, the upper lung zones of patients with CHF received significantly higher proportions of the blood flow compared with previously published data in normal volunteers. During exercise, however, the fractional perfusion to apices did not change, which suggests that apical flow redistribution is already maximized at rest. Measured pulmonary capillary wedge pressure failed to correlate with the upper zone or the ratio of upper-to-lower zone perfusion counts. Our findings suggest that upper zone flow redistribution may be associated with high, normal, or low capillary wedge pressure and therefore does not correlate with the pulmonary capillary wedge pressure in patients with chronic CHF.

In order to assess the effect of breathing pattern on measurements of dead space ventilation (VD/VT) during exercise, we studied 6 patients with the complaint of exertional dyspnea. They had essentially normal resting pulmonary function studies and the only abnormality noted during an initial exercise study was an elevated VD/VT associated with a rapid respiratory rate. A second exercise study was then performed during which they were coached to breathe at a slower rate and larger tidal volume. During the exercise study with coaching, the VD/VT response was normal. We conclude that breathing pattern during exercise influences VD/VT and that an increase in total minute ventilation which is accomplished by a preferential increase in respiratory rate may result in an abnormally high VD/VT.

Dependency of oxygen consumption (VO2) on oxygen delivery (DO2) in patients with adult respiratory distress syndrome and with congestive heart failure has been reported previously. We evaluated this relationship in 11 patients with pulmonary hypertension, 8 with primary pulmonary hypertension (PPH), and 3 with pulmonary hypertension secondary to chronic obstructive lung disease (SPH) at baseline and during treatment with vasodilating calcium channel antagonists. The mean baseline DO2 and VO2 were 11.0 +/- 4.2 and 3.9 +/- 1.1 ml/min/kg, respectively. After increasing cardiac output via vasodilators, we obtained an average of 3 additional data points per patient. We found a significant relationship between changes in VO2 and changes in DO2 (delta VO2 = -0.19 +/- 0.27 x delta DO2; r = 0.88, n = 37). In 4 patients, VO2 was determined both by respired gas analysis and by calculation from thermodilution cardiac output and measured arteriovenous oxygen gradient; results by the 2 methods were virtually identical. There was no significant relationship between cardiac output and mixed venous oxygen content or mixed venous oxygen tension (r = 0.20 and 0.47, respectively). Mean baseline oxygen extraction ratio was 36.7 +/- 6.4% and did not increase significantly after vasodilator therapy. We conclude that in patients with pulmonary hypertension, changes in oxygen consumption appear to be dependent on changes in oxygen delivery. This may represent evidence of tissue hypoxemia, which is otherwise not apparent. This dependency may support the use of vasodilators in these patients.

We have previously reported a drop on wasted ventilation fraction (VD/VT) during exercise in patients with pulmonary vaso-occlusive diseases associated with collagen vascular disorders, despite an abnormally high mean pulmonary artery pressure and pulmonary vascular resistance at rest and during exercise. To further evaluate the diagnostic value of VD/VT measurements, we studied 8 subjects with normal spirometry, lung volumes and single-breath diffusing capacity who had previously demonstrated a high VD/VT at rest and during exercise. We found normal pulmonary hemodynamics in these subjects despite an abnormal rest and exercise VD/VT. Our findings effectively exclude hemodynamically significant pulmonary vascular obstruction, and do not support the use of VD/VT as a screening method for detecting diffuse pulmonary vaso-occlusive diseases.

We evaluated the relationship between O2 delivery and oxygen consumption (VO2) in ten patients with the adult respiratory distress syndrome (ARDS) over the course of their illness (mean 7 +/- 5 days) while they were receiving positive mechanical ventilation with varying levels of positive end-expiratory pressure (PEEP). Mean values and standard deviations for O2 delivery and VO2 were 15.2 +/- 4.8 ml/min/kg and 4.1 +/- 1.2 ml/min/kg, respectively. In our ten patients, below an O2 delivery of 21 ml/min/kg, VO2 was linearly related to O2 delivery (VO2 = 0.32 X O2 delivery--0.53, n = 83, r = 0.76). However, at an O2 delivery rate higher than 21 ml/min/kg, there was no correlation between VO2 and O2 delivery. Mixed venous O2 content (CvO2) and arteriovenous oxygen content difference (C(a-v)O2) did not correlate with O2 delivery, nor was there a significant correlation between cardiac output (Qt) and mixed venous O2 tension (PvO2) or saturation (SvO2). We conclude that in patients with ARDS on mechanical ventilation with PEEP, VO2 and O2 delivery are linearly related except at high levels of O2 delivery. PvO2 and (C(a-v)O2) do not correlate with O2 delivery and are not sensitive indicators of tissue oxygenation in ARDS.

8 healthy dogs were anesthetized with a continuous infusion of pentobarbital (1 mg/kg/h) and were weakened but not paralyzed by intravenous succinylcholine (1 mg/kg/h). They were then studied during alternating periods of spontaneous breathing and assisted ventilation (IPPB). After succinylcholine, there was a significant increase in PaCO2, no significant change in respiratory frequency, a significant decrease in tidal volume, no significant change in P100 and a significant decrease in peak diaphragm EMG. Comparing periods of IPPB with periods of spontaneous breathing, there was a decrease in PaCO2 to a mean approximating that before succinylcholine, an increase in tidal volume, no change in frequency, and significant decreases in P100 and diaphragm EMG. In three experiments in which PaCO2 was maintained constant during IPPB, IPPB again resulted in a decrease in EMG and P100. Assisted mechanical ventilation of partially paralyzed dogs resulted in a fall in PaCO2 and a decrease in respiratory center output as measured by diaphragm EMG and P100. The fall in PaCO2 could be ascribed to decreasing the limited muscular work of breathing even in the presence of normal mechanics. A major part of the changes in EMG and P100 could be ascribed to chages in chemoreceptor drive but alteration of other inputs which were not specifically indentified, such as lung reflexes and/or chest wall reflexes, must also have had an effect.

To assess the effect of conventional chest physiotherapy and mechanical chest vibration on arterial blood gas levels, spirometry, and sputum production, we studied 20 stable outpatients with chronic obstructive lung disease. All patients had severe obstructive ventilatory defects with a mean FEV1/FVC ratio of 30 percent and all produced moderate amounts of sputum. Patients were randomized and received chest physiotherapy or mechanical vibration for 20 minutes. Arterial blood gas levels and spirometry obtained 20 minutes and 40 minutes after completion of the treatment did not show any significant change compared to the baseline. We conclude that neither chest physiotherapy nor chest mechanical vibration improved gas exchange, flow rates, or clearance of secretions in stable outpatients with severe chronic obstructive lung disease.

The fiberoptic bronchoscopic procedure (with brushings, washings, and biopsies) was performed and specimens of sputum were obtained before the procedure in 37 patients with cancer metastatic to the lung. Of the 37 patients studied, endobronchial lesions were visualized at bronchoscopic examination in 14 (group 1), and no endobronchial lesion was seen in 23 (group 2). The yield of bronchial brushing and washings was not significantly different in group 1 and 2, whereas examination of sputum obtained before the bronchoscopic procedure and bronchial biopsy in group 1 yielded higher results than the same procedures in group 2. The radiographic findings did not influence the yield with any of the bronchoscopic procedures. The overall positive diagnostic yield from fiberoptic bronchoscopic procedures among these patients was 54 percent (20/37), regardless of their bronchoscopic or radiologic findings.

The diagnostic yields of prebronchoscopy sputum specimens and fiberoptic bronchoscopy (including brushings, washings, and/or biopsies) were determined in 35 patients who presented primarily with middle or anterior mediasttnal and/or paratracheal mass(es) on chest radiographs. The diagnosis was confirmed on histopathology of tissue obtained by needle biopsy, mediastinoscopy, thoracotomy, and/or autopsy. Thirty-one of the patients were found to have primary bronchogenic carcinomas. At bronchoscopy, extrinsic compression of trachea and/or bronchi was visualized in 23 (Group I) and the tracheobronchial tree appeared normal in 12 (Group II). Prebronchoscopy sputa gave a positive yield in only three of the 35 (8%) patients; the yield was similar in both groups of patients. One or more of the bronchoscopic modalities were diagnostic in 69% of Group I patients but were not helpful in Group II patients. The diagnostic yield of brushings, washings, and biopsies in Group I patients was 52%, 61%, and 37%, respectively. The addition of biopsies to washings and/or brushings did not significantly alter the yield. Washings and brushings are recommended as useful, non-invasive procedures in diagnosing middle mediastinal masses with extrinsic compression. Sputum cytology gives a very low yield.

A patient twice developed the adult respiratory distress syndrome following an adverse reaction to administration of lidocaine. To our knowledge, such an association has not been reported previously.

We performed YAG laser photoresection in 11 patients with tracheal or mainstem bronchial obstruction due to malignant or benign disorders. We used maximal inspiratory-expiratory flow-volume loops and expiratory volume-time plots to assess air flow limitation. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF) and iso-volume maximal flows at 50 percent of forced inspiratory and expiratory volume were calculated. Spirograms and flow-volume loops were repeated within 12 to 72 hours of laser resection. All patients had flattened expiratory limbs on their flow-volume loops. All spirometric parameters increased significantly following laser photoresection. In particular, peak flow improved in all patients, and FEV1 improved in nine of 11 patients, even though four patients had moderate to severe obstructive ventilatory defects which persisted after resection and were probably due to longstanding chronic obstructive pulmonary disease. We conclude that flow-volume loops and spirometry are helpful in assessing the site and nature of malignant large airway obstructive processes and, moreover, provide reliable information for evaluating the efficacy of laser photoresection. Serial physiologic studies indicate changes in the caliber of the upper airways and can be used as a simple means of following these patients.

In order to study the effect of acute internal ventilatory loading and subsequent unloading on both ventilation and respiratory drive, we studied nine healthy dogs (18–24 kg) under a variety of conditions during constant anesthesia. Airways were obstructed by plastic beads to increase airways resistance 2–3 fold. The dogs were then put on IPPB and measurements were repeated. We then added CO2 to inspired air in order to increase PaCO2 to the same level as during spontaneous breathing after obstruction while they remained on IPPB. While dogs were on IPPB and at the same PaCO2, a bilateral cervical vagotomy was performed.

In order to study the effect of different levels of hematocrit on the single breath diffusing capacity (DLCO), we studied 90 lifelong nonsmokers with either iron deficiency anemia, polycythemia vera or normal hematocrits, age range 9 to 81 years, with expiratory normal flow rates and lung volumes. The DLCO ranged from 10.6 to 41.3 ml/min/mmHg and hematocrit ranged from 28%–64%. We noted a significant relationship between the DLCO and age, height, and hematocrit. We recommend that DLCO measured in the conventional manner be corrected for anemia and polycythemia by incrementing or decrementing the measured value, if expressed as a percent of predicted, by 1.35% for each percent of measured hematocrit below or above the normal values of 44%.

Postpericardiotomy syndrome has been recognized as a frequent complication following coronary artery bypass graft (CABG) surgery. We observed five cases of postpericardiotomy syndrome resulting in exudative pleural effusions with white blood cell differential counts greater than 80% lymphocytes. Tuberculosis, lymphoma, and other neoplasma have been major diseases associated with lymphocytic exudative pleural effusions. We feel postpericardiotomy syndrome is another important etiology that should be considered in post-CABG patients with lymphocytic pleural effusion.

We compared two modes of aerosol bronchodilator delivery in 34 patients hospitalized with obstructive airways diseases. The standard mode, therapist-administered up-draft nebulization (UDN), is labor-intensive and therefore relatively costly. The alternative mode, self-administration by a metered dose inhaler (MDI), is less costly, but its efficacy over an entire hospitalization has heretofore not been established. Patients were enrolled after transfer to the pulmonary ward from the emergency room or intensive care units (ICU). We then randomized them to receive metaproterenol q4h either via MDI or UDN. Daily spirometry revealed that MDI and UDN were associated with equivalent bronchodilation initially and equivalent improvement at discharge. The duration of hospitalization for the two groups was also the same. Thus, the two delivery methods were equally effective. We could not attribute this equivalence to pretreatment intergroup differences or to differences in concomitant therapy with steroids, theophylline, other bronchodilators, or antibiotics. Routine use of MDI rather than UDN in all non-ICU adult patients would save $253,487 per year at our institution alone.

We previously have shown that in patients with adult respiratory distress syndrome (ARDS) oxygen consumption (VO2) is linearly related to oxygen delivery (DO2) below a threshold DO2 of 21 ml/min/kg. To evaluate this relationship in chronic congestive heart failure (CHF), we studied eight patients with chronic CHF at baseline and during treatment with nitroglycerin. The resting DO2 and VO2 were 10.7 +/- 2.3 ml/min/kg and 3.8 +/- 0.87 ml/min/kg, respectively. In our eight patients, we found a significant relationship between changes in VO2 and in DO2 (delta VO2 = 0.16 + 0.34 X delta DO2, r = 0.84, n = 29). There was no significant relationship between DO2 and mixed venous oxygen tension (PvO2, r = 0.16), nor was there a significant relationship between cardiac output (Qt) and PvO2 (r = 0.21). We conclude that in patients with chronic CHF, changes in VO2 appear to be dependent on changes in DO2. This may represent an adaptive tissue response to chronically reduced systemic oxygen transport.

A new method for evaluation of changes in the distribution of pulmonary perfusion and ventilation during exercise was applied to normal male volunteers. Ventilation and perfusion scans were done with the subjects seated on a bicycle ergometer. The resting studies utilized krypton 81 ( 81m Kr) for ventilation and technetium 99m ( 99m Tc) macroaggregate albumin intravenously for perfusion. Exercise studies were done when 80 percent of maximum predicted heart rate was maintained for five minutes and utilized 81m Kr for ventilation and a tenfold dose of 90m Tc for perfusion. Higher dose of 99M Tc would minimize the effect of radioactivity left over from the resting study. This method allowed us to assess changes in ventilation and perfusion in normal subjects induced by exercise, but may also be applicable in a variety of cardiopulmonary conditions that affect pulmonary ventilation and perfusion or both.

To evaluate the complaint of exertional dyspnea in asbestos-exposed shipyard workers, pulmonary function tests were performed at rest and during exercise on 90 subjects with pleural plaques. We divided the subjects into four groups based on resting pulmonary function studies. Group I subjects (eight) had a restrictive defect; group II subjects (30) had an obstructive defect; group III subjects (six) had an isolated reduction in diffusing capacity; and group IV subjects (46) had a normal study. Subjects with a restrictive defect demonstrated minor physiologic abnormalities during exercise. Subjects with an obstructive defect demonstrated abnormalities consistent with their obstructive defect. Subjects in groups III and IV demonstrated an abnormally elevated wasted ventilation fraction, which may be an early indicator of interstitial disease due to asbestos exposure. We believe exercise testing was a useful tool in excluding the presence of significant functional exercise limitation due to asbestos exposure in the majority of subjects and also in disclosing some physiologic abnormalities in some of the subjects in our study.

It is often difficult to demonstrate objective evidence of physiologic improvement following a pulmonary rehabilitation program, despite subjective increases in exercise tolerance. In an attempt to identify sensitive indices of improvement, we studied resting and exercise lung function extensively in 15 patients (age range 45 to 73) with severe chronic obstructive lung disease before and after a pulmonary rehabilitation program. The six-week outpatient rehabilitation program consisted of exercise at 70 percent of the maximum predicted heart rate and diaphragmatic breathing for 20 minutes three times weekly. There were no significant changes in resting pulmonary function following exercise training. Exercise measurements were unchanged after completion of the program, with the exception of two parameters: heart rate and arterial lactate levels. The observed small but significant reductions in exercise heart rate and blood lactate levels following training may be due to conditioning of skeletal muscles, although respiratory muscle conditioning may be a contributing factor. Measurements of blood lactate may be a useful marker of conditioning in patients with chronic obstructive pulmonary disease who complete a pulmonary rehabilitation program.

We describe a case of air embolism complicating neodymium-YAG laser resection of an endobronchial carcinoid tumor. A 27-year-old man experienced an acute neurologic syndrome during laser photoresection which responded to acute hyperbaric therapy. (Chest 1988; 94:660-62)

Recently, it was shown that under certain conditions, there is a linkage between oxygen delivery (DO2) and oxygen consumption (VO2) so that any increase in DO2 is accompanied by an increase in VO2. We investigated this phenomenon in 10 patients with severe obstructive sleep apnea who had nocturnal oxygen desaturations to less than 85% (Group I), 10 patients with mild sleep apnea and no significant desaturations (Group II), and six obese control subjects (Group III). VO2 was measured by respired gas analysis before and after passive leg raising, which has been shown to increase DO2 by 10 to 12%. This was verified by thermodilution cardiac output measurements in four obese patients. In patients with severe sleep apnea, mean apnea index was 53 +/- 11, and supine VO2 was 141 +/- 40 ml/min/m2, whereas with leg elevation it rose to 163 +/- 41 ml/min/m2 (p less than 0.005). In patients with mild sleep apnea and in obese control subjects (mean apnea indices of 24 +/- 6 and 4 +/- 1, respectively), supine VO2 was 144 +/- 11 and 152 +/- 10 ml/min/m2, respectively; with leg elevation, VO2 was 144 +/- 13 and 151 +/- 6 ml/min/m2, respectively (p greater than 0.6). The study was repeated in nine of the Group I patients after 8 wk of treatment with nasal CPAP (Group IA). The repeated supine VO2 in these patients was 138 +/- 28 ml/min/m2, and a significant difference was not observed after leg raising (140 +/- 29 ml/min/m2; p greater than 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)