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Biomedical subjects

E Ballester

Publications and source records attributed to E Ballester.

At least 37 records · Page 2Linked to original sources
PubMed1998

Forced oscillation technique for the evaluation of severe sleep apnoea/hypopnoea syndrome: a pilot study.

The forced oscillation technique (FOT) is a noninvasive method of potential clinical interest for quantitatively assessing airway mechanics during sleep. We investigated the applicability of FOT as a diagnostic tool for noninvasive assessment of airflow obstruction in patients with sleep apnoea/hypopnoea syndrome (SAHS) during sleep. In seven patients previously diagnosed with severe SAHS (mean+/-SD apnoea/ hypopnoea index (AHI) 67+/-14) we performed a full polysomnography (PSG) together with on-line measurement of respiratory impedance (IZI) using FOT. For each patient we determined: 1) number of respiratory events conventionally detected by full PSG, those obtained by FOT and their degree of concordance; and 2) the characteristics and values of IZI during the respiratory events. FOT was well tolerated and easily applied in conjunction with a conventional sleep setup. The mean number of respiratory events x h(-1) detected by PSG and FOT were 55+/-16 and 58+/-17, respectively, with a strong concordance. IZI increased from a baseline of 11+/-4 to 50+/-20 cmH2O x L(-1) x s during apnoea (mean+/-SD). In all but one patient intermittent increases of IZI occurred immediately before each obstructive apnoea. In four patients, the increases of IZI developed at end-expiration whereas in two others occurred during inspiration. During hypopnoea most of the patients showed decreases of IZI during expiration. In conclusion, forced oscillation technique can be used as a noninvasive and complementary tool for the diagnosis of respiratory events and provides an on-line quantitative approach for continuous monitoring of airflow obstruction during sleep in patients with sleep apnoea/hypopnoea syndrome.

Adult↗
PubMed1997

Evaluation of nasal prongs for estimating nasal flow.

Nasal prongs (NP) connected to a pressure transducer have been suggested as a useful alternative for measuring nasal flow in sleep apnea/hypopnea patients. However, flow measured with NP is expected to be nonlinear. The aim of the present study was to analyze and correct the nonlinearity of nasal flow measurements with NP (VNP). Nasal flow was simultaneously measured with a pneumotachograph (PNT; V) and (NP; VNP) in six healthy subjects during 60 s of breathing at different tidal volumes. Nonlinearity of VNP was assessed by fitting separately, for inspiration and expiration, a Rorher-model equation (VNP x K1 x V + K2 x V2). In addition, we fitted the data to a simpler nonlinear quadratic model (P = K x V2). The main findings were: (1) an excellent fit of the Rorher equation to measured data in all cases; (2) although differences in the Rorher equation coefficients between inspiration and expiration were observed, they were not statistically significant; (3) a substantial intersubject variability was found; and finally, (4) the square root of VNP acceptably fitted the nasal flow data measured by PNT (V) in most cases. We conclude that in order to quantitatively assess nasal flow with NP, data should be corrected for their nonlinear pressure-flow relationships and, that the square root of the flow signal measured with NP is the simplest method of correcting for the observed nonlinearity.

Adult↗
PubMed1996

Comparison of manual and automatic CPAP titration in patients with sleep apnea/hypopnea syndrome.

Automatic CPAP (auto-CPAP) is engineered to automatically provide a positive pressure to the upper airway in response to apnea, hypopnea, airflow limitation, or snoring in patients with the sleep apnea/ hypopnea syndrome (SAHS). Self-adjusted CPAP has theoretical advantages over traditional fixed CPAP. We investigated the value of auto-CPAP regulation in 20 patients with SAHS in order to predict future fixed-level CPAP needs, as an alternative method to conventional polysomnographically (PSG)-controlled CPAP titration. This was accomplished through comparison of the optimal CPAP level obtained with PSG with that obtained with auto-CPAP. There were no significant differences between the optimal CPAP level achieved with full PSG or with auto-CPAP. As a secondary analysis, we analyzed auto-CPAP performance with regard to sleep-stage distribution and arousals in a group of nine male patients, and compared it with the previous group of 20 patients in which manually CPAP titration was guided by PSG. After adequate CPAP was reached, upward and downward fluctuations in the CPAP level had no significant effect on sleep architecture or fragmentation. We conclude that auto-CPAP permits the prediction of future fixed-level CPAP needs, and does so without sleep disruption.

Adult↗
PubMed1996

Visual and different automatic scoring profiles of respiratory variables in the diagnosis of sleep apnoea-hypopnoea syndrome.

The purpose of our study was to explore the diagnostic accuracy of different methods of scoring night time recording of respiratory variables (NTRRV) for the diagnosis of the sleep apnoea-hypopnoea syndrome (SAHS). Within a 2 week period, we performed a partially attended night time recording of respiratory variables and a full polysomnography (PSG) for reference in patients with suspected SAHS. Night time recording of respiratory variables was carried out using equipment which records, and continuously displays on a monitor, oximetry, airflow, chest and abdominal motion and body position. Night time recording of respiratory variables was scored manually and automatically, according to different combinations of the parameters described previously. Full polysomnography was performed in the Sleep Laboratory following conventional standards. Thirty six patients were studied. Visual analysis and different automatic scoring profiles of night time recording of respiratory variables were compared to full polysomnography in terms of agreement, sensitivity and specificity. Visual scoring of night time recording of respiratory variables gave the finest agreement-sensitivity-specificity relationship. Automatic scoring of nighttime recording of respiratory variables showed a trend to underestimate the apnoea-hypopnoea index (AHI) with respect to full polysomnography due mainly to underrecognition of hypopnoeas. Agreement-sensitivity-specificity relationships of automatic night time recording of respiratory variables with respect to full polysomnography varied depending on the automatic profile used. Some had a good agreement and sensitivity whilst others had a good specificity. These findings show that visual scoring of night time recording of respiratory variables is the most accurate method of analysis when compared to full polysomnography. The usefulness of the automatic methods of scoring of respiratory variables depends on the end-point chosen and is not reliable enough to be used in all situations. Night time recording of respiratory variables represents a real complement to conventional full polysomnography in clinical practice.

Adult↗
PubMed1995

Measurement of general health status in obstructive sleep apnea hypopnea patients.

Sleep apnea hypopnea syndrome (SAHS) is an entity that occurs frequently in the population and produces an elevated morbidity and mortality, especially at an apnea index greater than 20 events per hour. To our knowledge there are only a few studies available addressing the general health status of sleep apnea hypopnea patients. Such information may be useful for both clinical management and better understanding of the physiopathological mechanisms of the disease, particularly with the consideration that not infrequently the physiological disturbances found in such patients do not always agree with their own health perception. Therefore, the aim of the present study was to assess the general health status and the degree of daytime somnolence, as a major symptom in SAHS patients, and relate them to the number of respiratory events per hour. Measurements of general health status and the degree of daytime somnolence were assessed in 103 consecutive patients 50.4 +/- 12 years old [mean +/- standard deviation (SD)] with an apnea/hypopnea index (AHI) of 38 +/- 27 events per hour. Forty nonsnoring healthy subjects were used as the control group. During the afternoon preceding the full polysomnography, a medical history was taken; basic anthropometric data and the presence of other diseases were recorded. The Nottingham Health Profile (NHP) questionnaire and a questionnaire assessing the degree of daytime somnolence were administered to the patients. No significant differences were found in the general health status and the degree of daytime hypersomnolence when patients were divided into three groups according to the severity of the respiratory events during the night, but there were significant differences between SAHS patients and control subjects. It was concluded that in spite of the fact that SAHS patients showed a deterioration of general health status parameters in comparison with healthy subjects, these parameters do not correlate with the physiological disturbances of SAHS, expressed as the number of respiratory events per hour.

Adult↗
PubMed1995

In vitro release of arachidonic acid metabolites, glutathione peroxidase, and oxygen-free radicals from platelets of asthmatic patients with and without aspirin intolerance.

BACKGROUND: An abnormal platelet release of oxygen-free radicals has been described in acetylsalicylic acid (aspirin)-induced asthma, a finding which might suggest the existence of an intrinsic, specific platelet abnormality of arachidonic acid metabolism in these patients. The objective of this study was to evaluate platelet arachidonic acid metabolism in asthmatic patients with or without intolerance to aspirin. METHODS: Thirty subjects distributed into three groups were studied: group 1, 10 healthy subjects; group 2, 10 asthmatic patients with aspirin tolerance; and group 3, 10 aspirin-intolerant asthmatics. Platelets were isolated from blood, preincubated with 3H-arachidonic acid for 30 minutes and then incubated for 10 minutes with platelet activating factor (PAF) and aspirin. Cyclo-oxygenase (thromboxane, PGE2, PGF2 alpha, and HHT) and lipoxygenase (12-HETE) arachidonic acid metabolites were measured by high pressure liquid chromatography. Release of oxygen free radicals after incubation with PAF and aspirin was measured by chemiluminescence. Platelet levels of glutathione peroxidase (GSH-Px) were also measured using spectrophotometry. RESULTS: Platelets from aspirin-intolerant asthmatic patients produced higher quantities of arachidonic acid metabolites than the control group at baseline conditions. This increase was significant only for lipoxygenase products. No differences were found amongst the three groups in the response of arachidonic acid metabolism to PAF and aspirin. Incubation with aspirin but not with PAF caused an increase in oxygen-free radical production in aspirin-intolerant patients whereas in aspirin-tolerant patients PAF, rather than aspirin, was the more potent stimulus for oxygen-free radical production. No differences in GSH-Px levels were found amongst the three groups. CONCLUSIONS: These results suggest that the platelet lipoxygenase pathway is activated in aspirin-intolerant patients and that the production of oxygen-free radicals may differentiate aspirin-tolerant from aspirin-intolerant asthmatic subjects. Our study, however, does not support the hypothesis that an increase in lipoxygenase products may be responsible for oxygen-free radical production. Moreover, a lowered platelet GSH-Px activity does not seem to be involved in this phenomenon.

Adult↗
PubMed1995

Adequacy of prescribing nasal continuous positive airway pressure therapy for the sleep apnoea/hypopnoea syndrome on the basis of night time respiratory recording variables.

BACKGROUND: The increased demand of full polysomnographic studies, not only for diagnostic purposes but also for continuous positive airway pressure (CPAP) titration, has produced long waiting lists. Simpler methods are therefore needed to avoid having to refer all patients for full polysomnography. The hypothesis that CPAP therapy for the sleep apnoea/hypopnoea syndrome (SAHS) can be performed exclusively on the basis of recording night time respiratory variables was tested. METHODS: The level of CPAP in a group of 41 patients (three women) of mean (SD) age 52 (10) years, body mass index 31.5 (4.4) kg/m2, and apnoea/hypopnoea index (AHI) 53(16) events/hour was measured. During a two week period CPAP titration was performed in a random order in two settings: (1) in the sleep laboratory using full polysomnography; and (2) in the respiratory ward using equipment which continuously recorded and displayed pulse oximetry, airflow, chest and abdominal motion, and body position. The level of CPAP was increased progressively until apnoea, hypopnoea, snoring, and thoraco-abdominal paradox disappeared. RESULTS: No differences in CPAP levels (9.34(2.2) versus 9.68 (2.1) cm H2O) were found between full polysomnography and night time respiratory recordings. The accuracy of the measurement of both procedures showed good agreement. Only one patient showed a significant difference in CPAP level requirements between the two methods. CONCLUSIONS: Night time respiratory recording is sufficient to permit a reasonable choice of CPAP levels to abolish all the respiratory disturbances in most of the patients studied.

Female↗
PubMed1995

Time-course of stepwise CPAP titration. Behavior of respiratory and neurological variables.

Because successful medical treatment of obstructive sleep apnea/hypopnea syndrome (SAHS) depends on adequate CPAP treatment, we have analyzed in nine SAHS patients the behavior of respiratory and neurological parameters during a stepwise, polysomnography-controlled CPAP titration to achieve an optimal CPAP. Particularly, we have focused on which simple variable could predict the optimal CPAP pressure and could better define a distinctive optimal-suboptimal pattern. Main parameters analyzed through the CPAP titration procedure were respiratory events (apnea, hypopnea), the contour of inspiratory flow, the pleural pressure behavior, the thoraco-abdominal motion, oximetry, arousals, and sleep stage. During the CPAP titration we observed: (1) a rounded shape in the inspiratory flow contour was associated with the lowest esophageal pressure; (2) during stepwise increases in CPAP, almost all apnea events changed to hypopnea periods, followed by prolonged periods of limited inspiratory flow with still high esophageal pressure but without arousals (probably suboptimal CPAP); and (3) as CPAP reached suboptimal levels, sleep stage moved to deeper stages without arousals. We conclude that if during CPAP titration the end point is the disappearance of arousals, most patients with SAHS will still exhibit periods of high intrathoracic pressures with limited inspiratory flow. Alternatively, if the end point to be reached is the lowest esophageal pressure, higher CPAP levels will be needed. The contour of inspiratory flow appears as the simplest variable that best correlates with lowest esophageal pressure during CPAP titration.

Adult↗
PubMed1995

Diffuse alveolar hemorrhage in allogeneic bone marrow transplantation. A postmortem study.

To define better the syndrome of diffuse alveolar hemorrhage (DAH), we conducted a postmortem study in 77 patients who died of pulmonary complications, distributed into three groups. Group A included 47 patients with hematologic diseases treated with allogeneic bone marrow transplant (BMT); Group B, 20 patients with hematologic diseases treated with conventional chemotherapy; and Group C, 10 patients without hematologic diseases. The diagnosis of DAH was established when there was blood in at least 30% of the lung tissue evaluated without evidence of infection or any other pathologic change that could account for its presence. The presence of an associated pulmonary complication was considered only when there was normal lung parenchyma between both blood and the specific lesions. Diffuse alveolar hemorrhage was shown in 11 patients in Group A (23%) compared with 1 patient in Group B (5%) (p < 0.05). Of the 11 patients with DAH in Group A, 10 had some associated pulmonary complication: 7 presented with diffuse alveolar damage (DAD), 2 with associated bacterial pneumonia and 1 with invasive aspergillosis, 2 others had an associated cytomegalovirus (CMV) pneumonitis, and the remaining patients had an associated herpes pneumonia. There were no clinical differences between patients with and without DAH. Of 8 patients with confirmed DAH in Group A, who had been submitted to a bronchoscopic examination within 1 wk of death, 4 had normal BAL fluid; by contrast, 7 of 13 patients without DAH had hemorrhagic BAL fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Role of bronchoalveolar lavage in the diagnosis of fat embolism syndrome.

Fat embolism syndrome (FES) is a serious clinical disorder occurring in trauma patients. The diagnosis of fat embolism syndrome may be difficult to establish clinically. We therefore wanted to investigate the usefulness of bronchoalveolar lavage (BAL) in the diagnostic evaluation of fat embolism syndrome. We analysed the presence of fat droplets in BAL cells in 32 trauma patients (7 with full diagnostic criteria of fat embolism syndrome, 17 with incomplete diagnostic criteria, and 8 with no diagnostic criteria at the time of bronchoscopy), 9 nontrauma patients with acute respiratory failure and radiographic pulmonary infiltrates, and a control group composed of 10 individuals. An increased percentage of oil red O positive alveolar macrophages (cut-off point > 3%) in BAL was found in 6 out of 7 patients with definite clinical criteria of fat embolism syndrome, and in 6 out of 20 trauma patients without the clinical diagnosis of fat embolism syndrome. In two patients with fat embolism syndrome, sequential BAL showed that the percentage of positive macrophages decreased when the clinical manifestations disappeared. An increased number of BAL macrophages with fat droplets was also observed in two trauma patients without evidence of fat embolism syndrome after long-bone surgical intervention. By contrast, all non-trauma patients had a percentage of positive cells lower than 3%. Our findings suggest that BAL oil red O positive macrophages are frequently observed in trauma patients irrespective of the presence of fat embolism syndrome. Conceivably, a high number of oil red O positive macrophages could reflect clinically silent fat embolization.

Adult↗
PubMed1994

Response of the nose to exercise in healthy subjects and in patients with rhinitis and asthma.

BACKGROUND: Although the nose and the bronchi are both involved in the process of regulating respiratory heat exchange, thermal changes may precipitate airway obstruction during exercise but rarely cause nasal obstruction in patients with rhinitis. The cause of the different response of the nose and bronchial tree has hardly been investigated. This study was performed to assess the response of the nose during exercise in the presence of rhinitis, asthma, and in normal controls. METHODS: Ten healthy subjects (group 1), 15 patients with asthma and rhinitis (group 2), 10 with rhinitis only (group 3), and 11 with asthma only (group 4) were included in the study. Exercise was performed on a bicycle ergometer for six minutes, reaching a heart rate of 80% of predicted. Bronchial and nasal responses were measured by forced expiratory volume in one second (FEV1) and posterior rhinomanometry, respectively. A drop in the FEV1 of 20% or more was considered a positive exercise induced asthma challenge test. RESULTS: Heart rate and ventilation increased by a similar proportion in the four groups. The FEV1 significantly decreased in asthmatic patients (groups 2 and 4) but it did not change in healthy subjects (group 1) or in those with rhinitis (group 3). Thirteen asthmatic patients developed exercise induced asthma. Nasal patency increased with exercise by a similar proportion in all groups, and no differences were detected between those with rhinitis (groups 2 and 3) and those without (groups 1 and 4). Nasal patency had returned to basal values at 25 minutes after completion of exercise in the four groups. The nose of patients with exercise induced asthma, however, remained significantly more patent than in patients without exercise induced asthma between 10 and 30 minutes after exercise. CONCLUSIONS: These results suggest that the nose responds differently from the bronchi during exercise induced airway obstruction: whereas the bronchial tree responds by becoming narrowed, the nose becomes more patent. These findings suggest that the mechanisms regulating the response of the nose to exercise are different from those involved in the response of the bronchial tree.

Adult↗
PubMed1993

Aerosolised ribavirin in patients with advanced cryptogenic fibrosing alveolitis: a pilot study.

BACKGROUND: A report has recently been published concerning a patient with a cryptogenic fibrosing alveolitis who showed a striking improvement after being treated with the antiviral drug ribavirin (tribavirin, Virazid). The objective of this study was to further evaluate, in an open trial, the efficacy of rivabirin in cryptogenic fibrosing alveolitis. METHODS: Ten patients (eight women) with advanced cryptogenic fibrosing alveolitis received aerosolised ribavirin (6 g/day for 15 days). Chest radiographs, lung function, and severity of dyspnoea were evaluated before and after two weeks of rivabirin treatment and also at three and 12 months. RESULTS: No differences in radiographs, lung function impairment, or severity of dyspnoea were found after treatment. No side effects were detected. CONCLUSIONS: Administration of high doses of aerosolised ribavirin has no beneficial effects in patients with advanced cryptogenic fibrosing alveolitis.

Aerosols↗
PubMed1993

[Thoracic actinomycosis. Presentation of 3 cases].

We have had the chance to follow three patients with thoracic actinomycosis in a relatively short period of time (18 months). They were three male patients, with chronic dental infections. The illness appeared as toxic syndrome and fever. In all three cases diagnosis was made through samples obtained through fibropticbronchoscopy. At the same time all of them evolved favorably to the antibiotic treatment (penicillin and/or tetracyclines) prescribed. We conclude that the diagnosis of thoracic actinomycosis should be suspected in those patients with a compatible clinical and radiological condition, and who has suffered previous weakening diseases and periodontal lesions.

Actinomycosis↗
PubMed1991

[Pulmonary hemorrhage as the initial manifestation of Behçet's disease].

Pulmonary hemorrhage in Behçet's disease is exceptional. It usually presents as a hemoptysis and appears in advanced stages. A patient is described who sought medical care for oral and genital lesions, arthritis and progressive dyspnea. Analytical data showed anemia and chest X-ray revealed a bilateral interstitial pattern. A fiber bronchoscopy was performed which confirmed the existence of a diffuse pulmonary hemorrhage. Corticosteroid and azatioprine administration resolved the hemorrhage. Pulmonary hemorrhages in Behçet's disease are reviewed and in view of a available literature therapeutic possibilities are discussed.

Adult↗
PubMed1990

Pulmonary gas exchange in severe chronic asthma. Response to 100% oxygen and salbutamol.

Ventilation-perfusion (VA/Q) inequality has been evaluated using the multiple inert gas technique in nine nonsmoking patients (mean +/- SD, age 56 +/- 10 yr) with stable, severe, chronic asthma (partially reversible airway obstruction; baseline FEV1, 39 +/- 10% predicted) before and during 100% O2 breathing and then 15 min after three puffs (300 micrograms) of inhaled salbutamol. The aim of this study was to investigate whether this type of asthma was associated with a different pattern of VA/Q inequality from that observed in acute episodes and in particular to determine whether the VA/Q pattern was fixed or could be altered by bronchodilator agents or O2 breathing. The predominant pattern of VA/Q distribution was broad and unimodal but without shunt (VA/Q = 0) or low VA/Q areas (VA/Q less than 0.1 to greater than 0.005). The amount of VA/Q inequality as assessed by the dispersion of the distribution of pulmonary bloodflow (log SDQ) was not great (log SDQ, 0.77 +/- 0.09), and no correlation was found with the degree of airway obstruction, PaO2 or AaPO2. During 100% O2 breathing, VA/Q inequality worsened (from log SDQ of 0.77 +/- 0.09 to 1.11 +/- 0.21, p = 0.01) with an increase in the perfusion of low VA/Q units (from 0.43 +/- 0.66% to 6.3 +/- 6.5%, p = 0.02) but still no development of shunt. This suggests the presence of hypoxic pulmonary vasoconstriction breathing air, possibly contributing to the preservation of VA/Q relationships.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1989

Ventilation-perfusion mismatching in acute severe asthma: effects of salbutamol and 100% oxygen.

Ventilation-perfusion (VA/Q) relationships and gas exchange were studied by the multiple inert gas technique in 19 patients admitted to hospital with acute severe asthma (FEV1 41% predicted) before and during the administration of intravenous salbutamol, inhaled salbutamol, or 100% oxygen. Eight patients received a continuous intravenous infusion of salbutamol (4 micrograms/min, total dose 360 micrograms) and were studied before treatment, after 60 and 90 minutes of treatment, and one hour after treatment had been discontinued. Six patients had measurements before and 15 minutes after inhaling 300 micrograms salbutamol from a metered dose inhaler on two occasions (total dose 600 micrograms) and one hour after the last dose. Measurements were also made in five patients before and while they breathed 100% oxygen for 20 minutes. At baseline (fractional inspired oxygen (FiO2) 21%) all patients showed a broad unimodal (n = 10) or bimodal (n = 9) distribution of blood flow with respect to VA/Q. A mean of 10.5% of the blood flow was associated with low VA/Q units without any appreciable shunt. One of the best descriptors of VA/Q inequality, the second moment of the perfusion distribution on a log scale (log SD Q), was moderately high with a mean of 1.18 (SEM 0.08) (normal less than 0.6). Measures of VA/Q inequality correlated poorly with spirometric findings. After salbutamol the increase in airflow rates was similar regardless of the route of administration. Intravenous salbutamol, however, caused a significant increase in heart rate, cardiac output, and oxygen consumption (VO2); in addition, both perfusion to low VA/Q areas and log SD Q increased significantly. Inhaled salbutamol caused only minor changes in heart rate, cardiac output, VO2, and VA/Q inequality. Arterial oxygen tension (PaO2) remained unchanged during salbutamol administration, irrespective of the route of administration. During 100% oxygen breathing there was a significant increase in log SD Q (from 1.11 to 1.44). It is concluded that patients with acute severe asthma show considerable VA/Q inequality with a high level of pulmonary vascular reactivity. Despite similar bronchodilator effects from inhaled and intravenous salbutamol, VA/Q relationships worsened only during intravenous infusion. PaO2 remained unchanged, however, because the change in VA/Q relationships was associated with an increase in metabolic rate and cardiac output.

Acute Disease↗
PubMed1989

Mechanisms of hypoxemia in patients with status asthmaticus requiring mechanical ventilation.

Eight consecutive patients (mean +/- SD age, 43 +/- 11 yr) with acute severe asthma (status asthmaticus) requiring assisted ventilation were studied within the first 24 to 48 h of admission, at maintenance FIO2 and while breathing 100% O2, using the multiple inert gas elimination technique. Ventilation-perfusion (VA/Q) inequality was characterized by a marked bimodal blood flow distribution (perfusion to normal and low VA/Q populations) in all but two patients, with a mean of 27.6 +/- 12.3% of the total perfusion present in the low VA/Q ratio units (between 0.1 and 0.005). As a result, the dispersion of pulmonary blood flow distribution (log SDQ) was severely abnormal (mean, 1.65 +/- 0.28; normal range, 0.3 to 0.6). No patient had a substantial shunt (VA/Q = 0) (mean value, 1.5 +/- 2.3%). The ventilation distribution was never bimodal, but the dispersion of the ventilation distribution (log SDV) was moderately elevated (1.01 +/- 0.24). High VA/Q areas (ventilation to VA/Q units between 10 and 100) were generally absent. While breathing 100% O2, PaO2, PvO2, and PaCO2 significantly rose, as did shunt and blood flow dispersion. Patients with life-threatening acute severe asthma treated by mechanical ventilation show: (1) the most abnormal gas exchange characteristics of the VA/Q spectrum observed to date in human asthma but essentially the same pattern as in patients with less severe disease; (2) a high level of hypoxic pulmonary vascular response; (3) a significant amount of shunt while breathing 100% O2, suggesting the presence of absorption atelectasis or redistribution of blood flow.

Adult↗