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PubMed2000

The differing patterns of subclinical pulmonary involvement in connective tissue diseases as shown by application of factor analysis.

To explore common patterns of interstitial lung disease (ILD) in symptomless patients with connective tissue disease (CTD), we applied factorial analysis to determine the relationship among the factors. A selected cohort of 71 non-smoking patients with a confirmed diagnosis of CTD [24 with primary Sjögren's syndrome (pSS), 21 with systemic sclerosis (SS), 20 with rheumatoid arthritis (RA) and six with polymyositis/ dermatomyositis (PM/DM)] were identified. The diagnostic techniques included pulmonary function tests, bronchoalveolar lavage (BAL), chest radiographs and high-resolution computed tomography (HRCT). Disease extent and severity were assessed by a radiological and HRCT grading system. Three factors, accounting for 67% of the total variance, were extracted. The first factor (disease duration, diffusing lung capacity, neutrophils and CD8+ T cells on BAL, radiographic score and HRCT reticular score), with the highest percentage of variance (36.5%), defines a fibrotic lung pattern. The second factor (17.9% of variance) identifies an inflammatory lung pattern (macrophages, lymphocytes and eosinophils on BAL and HRCT ground-glass score). The third factor (12.6% of variance) represents a ventilatory function pattern (forced vital capacity, total lung capacity and forced respiratory volume in 1 s). The negative correlation between the fibrotic lung pattern and ventilatory function pattern, but not with the inflammatory lung pattern, suggests the presence of a significant derangement of the alveolar structures. In conclusion, application of factor analysis reveals various lung disease patterns in patients with CTD that might have different prognostic implications.

Adult↗
PubMed1982

Morphologic changes in the lung during the lifespan of Fischer 344 rats.

Pulmonary structure and function were quantitatively investigated over the lifespan of the Fischer 344 rat by morphometric and physiologic techniques. Male animals 1 week, 6 weeks, 5 months, 14 months, and 26 months of age and female animals 5 months, 14 months, and 26 months of age were studied. All alveolar tissue compartments demonstrated significant increases in volume, surface area, and cell number during the first 5 months of life. From 5 to 26 months of age, remodelling in the epithelial and interstitial compartments continued to take place while the endothelial compartment remained relatively unchanged. In the epithelial compartment the ratio of type II cells to type I cells lining the alveolar surface decreased as age increased. In the interstitial compartment the volume of the noncellular components of the interstitium increased by 39% in males and by 89% in females from 5 to 26 months of age. Physiologic measurements of lung volumes in males at 6 weeks, 14 months, and 26 months demonstrated progressive increases in vital capacity (VC) and total lung capacity (TLC). Morphometric pulmonary-diffusion capacity (DLO2) increased in males from 1 week to 5 months of age and remained relatively unchanged from 5 to 26 months of age in both sexes.

Aging↗
PubMedDate not supplied

[Farmer's lung with antibodies against Thermoactinomyces vulgaris and Aspergillus fumigatus. Clinical course and treatment].

We present a case of Farmer's lung with antibodies to Thermoactinomyces vulgaris and Aspergillus fumigatus. A 56-year-old male patient with an atopic family medical history came to our hospital complaining of cough, dyspnea, fever, asthenia and anorexia. His condition worsened after being exposed to cereal powder, becoming symptomatic after 20 minutes or on occasion after 6 hours. Physical examination showed basal crepitant rales in lung auscultation. The radiograph of the thorax showed a bilateral interstitial reticulo-nodular pattern. An obstructive pattern was found on functional respiratory examination. There was also a slight restriction along with the decrease of the VC and a significant reversal of the M.M.E.F. with anticholinergics. The tests for intradermal cutaneous allergies were positive after 20 minutes and for Aspergillus fumigatus Niger and Terreus (Bencard) after 6 hours. With immunoelectrophoresis and double diffusion, precipitation bands in the presence of Aspergillus fumigatus and Thermoactinomyces, were detected. IgG and IgE were high-1570 mg% and 1000 U/ml respectively. The histological study of the transbronchial biopsy showed dilatation of the alveolar septum caused by a lymphocytic infiltration with fragments of collagenous fibres. In bronchoalveolar lavage there was a predominance of lymphocytes and histiocytes. After exertion, arterial blood gases showed desaturation with hypoxemia. The static lung volumes and the flow and diffusion of carbon monoxide (CO) showed a moderate decrease of vital capacity, with the total lung capacity being below normal. Diffusion was markedly attenuated. The provocation test by indirect bronchial inhalation using cereal powder (Alfalfa) was positive. After six hours dyspnea, cough and leukocytosis appeared with an outbreak of fever and an increase in the erythrocyte sedimentation rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Fungal↗
PubMed1987

An emphysema model in rats treated intratracheally with elastase.

Pulmonary functions, morphology, and morphometry were examined in rats at 3, 7, and 10 weeks after a single intratracheal administration of 6.5 units of porcine pancreatic elastase in order to obtain a model of pulmonary emphysema which would be suitable for studying the responses of emphysematous lungs to atmospheric pollutants. Functional residual capacity and residual volume of the elastase-treated rats increased at all the times studied, but their total lung capacity increased only at 7 and 10 weeks compared with those of the saline-treated control rats. The increase in static lung compliance and the decrease in peak flow and maximum flow at 50% of total lung capacity during forced expiration were also observed in all except the 3-week elastase animals. The elastase-treated lungs showed morphological changes characteristic of emphysematous lesions. The increase in mean linear intercept length and the decrease in total alveolar surface area were demonstrated by these elastase-treated lungs. Based on these results, we conclude that an adequate and suitable model of pulmonary emphysema could be obtained in rats 7-10 weeks after treatment with the present dose of elastase.

Animals↗
PubMed1987

An isovolume method for analysis of density dependence of maximal expiratory flows.

The usual method of measuring density dependence of maximum expiratory flows is superimposition at total lung capacity or residual volume of maximum expiratory flow volume (MEFV) curves obtained breathing air and a mixture of 80% He plus 20% O2 (HeO2). A major problem with this technique is the large variability in results, which has been thought to be due to errors in matching lung volumes on both gases. Accordingly, we obtained MEFV curves breathing air and HeO2 using a bag-in-the-box system so that the curves breathing the two gas mixtures could be directly superimposed without removing the mouthpiece (isovolume). Ten healthy, nonsmoking subjects performed MEFV curves on each gas mixture for six consecutive experiments. We compared the increase in flow at 50% of vital capacity (delta Vmax50) and volume of isoflow (Viso) by superimposing and matching the MEFV curves at total lung capacity, at residual volume, and using the isovolume method. The variability of each method was assessed by the mean intersubject and intrasubject coefficients of variation. In all subjects, the mean delta Vmax50 and Viso as well as their corresponding coefficients of variation were not significantly different among the three methods. We conclude that, in healthy nonsmoking young adults, the method chosen for superimposing and matching MEFV curves has no effect on the variability of delta Vmax50 and Viso.

Adult↗
PubMed1979

Effects of lung volume on collateral and airways resistance in man.

The effects of changing lung volume (VL) on collateral resistance (Rcoll) and total airways resistance (Raw) were compared in six young volunteers. At functional residual capacity (FRC) = 55% total lung capacity (TLC), mean Rcoll was 4,664 +/- 1,518 (SE) cmH2O/(l/s) and mean Raw was 1.57 +/- 0.11 (SE) cmH2O/l/s). When VL increased to 80% TLC, Rcoll decreased by 63.3 +/- 7.8%, and Raw decreased by 50.3 +/- 4.2 (SE) %. The decrease in Rcoll with increasing lung volume was not statistically different from that of Raw (P less than 0.05). If the airways obstructed for measurements of Rcoll served between 2 and 5% of the lungs, then Rcoll was approximately 50 times as great as the resistance to flow through airways serving the same volume of lung at FRC. The relationship did not change significantly when VL increased by 25% TLC. If changes in Raw reflect changes in airways supplying sublobar portions of lung, these results indicate that there is no tendency for the redistribution of ventilation through airways and collateral pathways with changes in VL in young subjects.

Adult↗
PubMed2006

Recovery of pulmonary function following endoscopic anterior scoliosis correction: evaluation at 3, 6, 12, and 24 months after surgery.

STUDY DESIGN: A series of patients with scoliosis undergoing endoscopic anterior instrumentation and fusion undertaking repeated pulmonary function assessments. OBJECTIVE: To assess recovery of pulmonary function in the 2 years following endoscopic anterior scoliosis correction. SUMMARY OF BACKGROUND DATA: Recent studies have found that pulmonary function returns to preoperative levels 12-24 months following endoscopic anterior scoliosis correction, and a small improvement in forced expiratory volume (FEV1) has also been reported. METHODS: A series of 44 patients with endoscopic anterior scoliosis correction had pulmonary function tests before surgery, and at 3, 6, 12, and 24 months after surgery. Forced vital capacity (FVC), FEV1, and total lung capacity (TLC) were measured. Nonparametric statistical analysis was used to investigate changes in pulmonary function between successive assessments. RESULTS: Pulmonary function decreased by approximately 10% at 3 months after surgery. At 24 months after surgery, FVC and FEV1 recovered to 5% to 8% higher than preoperative levels, while TLC returned to preoperative levels. Statistically significant improvements in most pulmonary function values occurred between 3 and 6, and 6-12 months. Improvements in mean FVC, FEV1, and TLC continue between 12 and 24 months, although only the increase in absolute FVC for this time is statistically significant. CONCLUSIONS: Endoscopic anterior scoliosis surgery has no lasting negative effect on pulmonary function, and with prolonged follow-up, pulmonary capacity improves beyond preoperative levels.

Adolescent↗
PubMed1982

Validation of the plain chest radiograph for epidemiologic studies of airflow obstruction.

The chest radiographs of 125 industrial workers from rural New South Wales were examined for overinflated lungs, with and without attenuated midzonal vessels. Although the mean values of a comprehensive range of pulmonary function tests in the whole group were within normal limits, the nine subjects whose radiographs showed overinflated lungs and attenuated vessels had significantly impaired pulmonary function in comparison with 85 subjects with normal radiographs. The mean values for these nine subjects, expressed as a percentage of the mean value for subjects with normal radiographs, were: forced expiratory volume in 1 second, 75%; total lung capacity, 107%; residual volume, 143%; transpulmonary pressure at maximum inspiration, 60%; static deflation compliance, 158%; lung volume at transpulmonary pressure 10 cm H2O, 132%; transfer factor, 79%; and transfer factor/alveolar volume, 77%. Similar results were obtained by a second observer. Those subjects with overinflation but no vascular attenuation had significantly larger mean values for vital capacity and alveolar volume but no significant difference in total lung capacity or other tests of the mechanical properties of the lungs. Agreement on the presence of a positive sign between the two observers expressed as a percentage of those considered positive by either was 81% for overinflation and 62% for attenuated midzonal vessels. The results indicate that in groups of subjects with normal-average values of pulmonary function, the plain chest radiograph may provide information concerning pulmonary structure that is reflected in tests of function.

Adolescent↗
PubMed1977

[Effect of beta-adrenergic stimulation on the closing volume in normal subjects (author's transl].

In 12 normal subjets we studies the effects of beta-adrenergic stimulation (Salbutamol, 500 microgram inhaled) on the closing volume (CV) and the closing capacity and on the ratios of these indexes to the vital capacity (VC) and the total lung capacity, respectively. CV and CV/VC % increased in ten subjects wereas it decreased in two subjects. On an average, the changes were small but significant (p less than 0.01) and could be duplicated in four subjects. Similar studies have yielded variable results. The reasons for those variation could be attributed either to technical or/and individual differences in the resulting effect of beta stimulation on respiratory mechanics.

Adrenergic beta-Agonists↗
PubMed1991

Lung volume, diffusing capacity, chest roentgenogram and dyspnea index in interstitial lung disease.

To investigate the physiologic impairment and the role played by pulmonary function tests in interstitial lung disease (ILD), we performed spirometry tests and tested the single-breath carbon monoxide diffusing capacity of 27 patients with diffuse interstitial pulmonary fibrosis (DIPF) and 35 patients with collagen vascular disease (CVD). All of the patients showed irregular linear opacities on their chest X-ray films. Corresponding chest roentgenograms for each patient were evaluated according to the International Labour Organization (ILO) classification. A modified Baseline Dyspnea Index (BDI), which incorporate a patient's physical activity into the recording, was used to quantitate dyspnea. Patients with DIPF demonstrated a comparable reduction in both lung volumes and diffusing capacity. In contrast, patients with CVD had a greater reduction in diffusing capacity than in forced vital capacity (FVC) and total lung capacity (TLC). There were no significant correlations between the type of linear opacities and the severity of the pulmonary function abnormalities, or between the opacities and the dyspnea in either disease group. The profusion of pulmonary infiltrates also did not affect the lung function except for diffusing capacity in patients with DIPF. However, there was a significant loss of FVC, TLC, forced expiratory volume in one second (FEV1) and diffusing capacity with increasing levels of dyspnea. We conclude that pulmonary function parameters may not be equally affected in DIPF and CVD. Approaches using the ILO classification for analysis of chest roentgenograms provide limited information regarding the functional status of patients. Pulmonary functions are significantly related to the extent of a patient's physical activity, if the severity of dyspnea is evaluated carefully using a quantifiable system.

Adult↗
PubMed1996

Mechanisms of relief of exertional breathlessness following unilateral bullectomy and lung volume reduction surgery in emphysema.

STUDY OBJECTIVE: To explore mechanisms of relief of exertional breathlessness following surgery to reduce thoracic gas volume in patients with emphysema. MATERIALS AND METHODS: We studied 8 patients with emphysema (FEV1 = 39 +/- 3% predicted; residual volume [RV] = 234 +/- 12% predicted; mean +/- SEM) who were severely breathless despite optimal pharmacotherapy and who underwent unilateral bullectomy for giant bullae (greater than one third hemithorax); 4 of these also had ipsilateral lung reduction (pneumectomy). Pulmonary function and cycle exercise performance (n = 6) were evaluated before and 13 +/- 3 weeks after surgery. Chronic breathlessness was measured with the Baseline Dyspnea Index and the Medical Research Council dyspnea scale. Exertional breathlessness was measured using Borg ratings at a standardized work rate (BorgSTD). RESULTS: FEV1, FVC, and maximal inspiratory pressures increased postsurgery by 29 +/- 7% (p < 0.05), 24 +/- 10% (p = 0.06), and 39 +/- 12% (p < 0.01), respectively. Plethysmographic total lung capacity, RV, and functional residual capacity fell by 14 +/- 2%, 30 +/- 4%, and 18 +/- 3%, respectively (p < 0.001). All measures of chronic breathlessness improved significantly (p < 0.05). During exercise at a standardized work rate, BorgSTD fell 45% (p < 0.05), end-expiratory lung volume (EELV) fell 22% (p < 0.01), and breathing frequency (F) fell 25% (p = 0.08). By multiple stepwise regression analysis, 99% (p = 0.007) of the variance in symptom relief (delta BorgSTD) was explained by the combination of decreased ratio of the end-expiratory lung volume to total lung capacity, decreased F, and diminished mechanical constraints on tidal volume (tidal volume to vital capacity ratio). CONCLUSION: Reduced exertional breathlessness at a given workload after volume reduction surgery was attributed to a combination of reduced thoracic hyperinflation, reduced F, and reduced mechanical constraints on lung volume expansion.

Dyspnea↗
PubMed1992

Capillary and fiber geometry in rat diaphragm perfusion fixed in situ at different sarcomere lengths.

To determine the potential range of diaphragm sarcomere lengths in situ and the effect of changes in sarcomere length on capillary and fiber geometry, rat diaphragms were perfusion fixed in situ with glutaraldehyde at different airway pressures and during electrical stimulation. The lengths of thick (1.517 +/- 0.007 microns) and thin (1.194 +/- 0.048 microns) filaments were not different from those established for rat limb muscle. Morphometric techniques were used to determine fiber cross-sectional area, sarcomere length, capillary orientation, and capillary length and surface area per fiber volume. All measurements were referenced to sarcomere length, which averaged 2.88 +/- 0.08 microns at -20 to -25 cmH2O airway pressure (residual volume) and 2.32 +/- 0.05 microns at +20 to +26 cmH2O airway pressure (total lung capacity). The contribution of capillary tortuosity and branching to total capillary length was dependent on sarcomere length and varied from 5 to 22%, consistent with that shown previously for mammalian limb muscles over this range of sarcomere lengths. Capillary length per fiber volume [Jv(c,f)] was significantly greater at residual volume (3,761 +/- 193 mm-2) than at total lung capacity (3,142 +/- 118 mm-2) and correlated with sarcomere length [l; r = 0.628, Jv(c,f) = 876l + 1,156, P less than 0.01; n = 18]. We conclude that the diaphragm is unusual in that the apparent in situ minimal sarcomere length is greater than 2.0 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Late effects of bone marrow transplantation on pulmonary function in children.

This study was undertaken to evaluate in a primarily pediatric population whether the late effects of bone marrow transplantation (BMT) on pulmonary function in patients having undergone the procedure for treatment of acute leukemia or lymphoma are worse than that of patients having undergone transplant for treatment of aplastic anemia. Forty-six patients were studied. We did not demonstrate statistically significant differences in group mean forced expiratory flow in one second/forced vital capacity (FEV1/FVC) and percentage predicted forced expiratory volume in one second (FEV1), forced vital capacity (FVC), forced expiratory flow at 25-75% of the forced vital capacity (FEF25-75) and total lung capacity (TLC) values between the two groups of patients before BMT and to 7 years post-transplant. Individual patients with pulmonary function abnormalities were identified. Furthermore, there were no significant differences between the two study groups or within the group of patients with aplastic anemia from pre-transplant to 9-12 months and from pre-transplant to 18-24 months after BMT. However, within the group of patients treated for acute leukemia or lymphoma, there was a significant decline in the group mean percentage predicted FVC (p = 0.0001), FEV1 (p = 0.0006) and FEF25-75 (p = 0.0063) from pre-transplant to 9-12 months and in the FVC (p = 0.004) and FEV1 (p = 0.0006) from pre-transplant to 18-24 months after BMT. The greater decline in the FVC relative to the FEV1 suggests the development of a restrictive process in this group of patients.

Adolescent↗
PubMed1977

Pulmonary function in nonsmoking subjects with alpha1 antitrypsin deficiency (MZ phenotype).

We measured pulmonary functions in 10 nonsmoking asymptomatic subjects, ages 40.5 years +/- 9.2 years, with alpha1 antitrypsin heterozygous deficiency (phenotype MZ). The subjects were longstanding residents of the greater Los Angeles area. The range of physiologic studies and per cent of normal predicted values were forced vital capacity (FVC), 2.8 to 7.0 liters (86 to 124 per cent predicted); ratio of the forced expiratory volume in 1 second to the FVC, 70 to 86 per cent (86 to 104 per cent predicted); the ratio of the residual volume to total lung capacity, 28 to 44 per cent (94 to 119 per cent predicted); total lung capacity, 4.8 to 9.8 liters (80 to 119 per cent predicted); flow at 50 per cent FVC, 3.1 to 7.8 liters per second (69 to 140 per cent); and volume of isoflow, 7.3 to 26 per cent of forced vital capacity (38 to 137 per cent predicted). In eight patients studied, static deflation pressure volume curves were normal, and at respiratory rate of 60 breaths/min the ratio of dynamic compliance to static compliance did not fall below 84 per cent. We have found that these nonsmoking heterozygotes with alpha1 antitrypsin deficiency have normal pulmonary functions (within 1.67 SD of predicted mean).

Adult↗
PubMed2004

Relating maximum airway dilation and subsequent reconstriction to reactivity in human lungs.

Measures of airway resistance (Raw) during deep inspiration (DI) suggest that asthmatic subjects possess stiffer, more reactive airway smooth muscle. There is evidence that one can enhance airway reactivity in healthy lungs by prohibiting DI for an extended period. The present study had two goals. First, we determined whether the maximum dilation capacity of asthmatic subjects depended on the rate of the DI. Second, we investigated whether the enhanced reactivity in healthy humans might derive from additional mechanisms not present in asthmatic subjects. For the first goal, we tracked Raw in seven healthy and seven asthmatic subjects during a noncoached DI, a DI with a 5- to 10-s breath hold at total lung capacity, and a rapid DI. We found that the minimum resistance achieved at total lung capacity was independent of the manner in which the DI was performed. For the second goal, we tracked the rate of return of Raw after a DI as well as dynamic lung elastance before and after the DI, at baseline and after bronchial challenge. A drop in lung elastance post-DI would indicate reopening of lung regions and/or reduced heterogeneities. The data show that constricted healthy but not asthmatic subjects produce longer lasting residual dilation. Hence, a portion of the enhanced reactivity in a healthy subject's response to prohibition of DIs is likely due to airway closure and/or atelectasis that can be ablated with a DI. We conclude that preventing DIs does not ensure that healthy subjects will transition entirely to an asthmatic-like hyperreactive lung state.

Adult↗
PubMed1987

Childhood sequelae of infant lung disease: exercise and pulmonary function abnormalities after bronchopulmonary dysplasia.

To determine the long-term pulmonary sequelae and effect on exercise tolerance of bronchopulmonary dysplasia (BPD), we studied 10 children at a mean age of 10.4 years, who had been born prematurely, survived respiratory distress syndrome, and subsequently developed BPD, and compared them with eight age-matched normal children born at term. Pulmonary function tests and graded exercise stress tests were performed. Residual volume, the ratio between residual volume and total lung capacity, vital capacity, forced expiratory volume in 1 second, forced expiratory flow between 25% and 75% of vital capacity, and maximal expiratory flows at 80%, 70%, and 60% of total lung capacity were all abnormal (P less than 0.02) in the children with BPD, compared with control values. Pre-exercise transcutaneous CO2 tension was higher (P less than 0.05) in the BPD group than in the control group. At maximal workload, tcPCO2 remained high in patients with BPD compared with control values (P less than 0.05). Arterial oxygen saturation at maximal workload fell below pre-exercise levels in the BPD group (P less than 0.05) but not in control children. There were no differences in maximal oxygen consumption between the BPD group and control children. Exercise-induced bronchospasm occurred in 50% of the BPD group, but not in the control group. We conclude that long-term survivors of BPD have evidence of airway obstruction, hyperinflation, and airway hyperreactivity, compared with a control group. Aerobic fitness was not significantly different in the BPD and control groups, but was achieved in the BPD group at the expense of a fall in SaO2 and a rise in tcPCO2.

Asthma↗
PubMed2003

Effects of radiotherapy and chemotherapy on lung function in patients with non-small-cell lung cancer.

PURPOSE: To evaluate the effects of chemoradiation on objective tests of pulmonary function. MATERIALS AND METHODS: One hundred lung cancer patients treated in five protocols between 1992 and 2000 with combinations of thoracic radiotherapy (RT) and chemotherapy were evaluated with pre- and post-RT pulmonary function tests. The pulmonary function tests were analyzed for changes in measures of obstruction (forced expiratory volume in 1 s per unit of vital capacity [FEV(1)/VC]), restriction (total lung capacity [TLC]), and diffusing capacity (diffusing capacity for carbon monoxide [DLCO]). The use and timing of chemotherapy and RT, as well as patient, tumor, and treatment factors, were evaluated using univariate and multivariate analyses. RESULTS: No treatment or patient factors were significantly associated with changes in FEV(1)/VC. Chemotherapy with RT, compared with RT alone, was associated with a lower post-RT TLC (92% vs. 107%, p = 0.002). Nodal status (N2-N3 vs. N1), tumor location (central vs. peripheral), use of >/=6 treatment fields, and tumor volume >/=100 cm(3) were also associated with a significantly lower post-RT TLC. On univariate analysis, the use of any chemotherapy (p = 0.029) and the use of concurrent vs. sequential chemotherapy (p = 0.028) were predictive of a lower post-RT DLCO. Patient age >/=60 years, nodal status (N2-N3 vs. N0-N1), tumor volume >/=100 cm(3), tumor location (central vs. peripheral), and use of >/=6 treatment fields were also associated with a significantly lower post-RT DLCO. The fractional volume of irradiated normal lung correlated with the decrease in DLCO (p <0.001), with a 1.3% DLCO decline for each 1% of total lung volume that received >20 Gy. CONCLUSIONS: The addition of chemotherapy to RT significantly exacerbates the post-RT decrease in TLC and DLCO. The greatest decrease in DLCO occurs in patients treated with concurrent chemoradiation.

Adult↗
PubMed1983

[End inspiratory lung volumes as the limiting factor in PEEP ventilation].

In 17 patients requiring artificial ventilation expiratory pressure-volume curves (VPE) were plotted all over the inspiratory capacity (IC) between total lung capacity (TLC) and functional residual capacity (FRC). Then patients were ventilated with PEEP of 0, 5, 10 and 15 cmH2O for 30 min. The volume excursions with known PEEP were displayed graphically into the VPE to determine the position of end-inspiratory volume within the IC. The steep, quasi-linear part of each VPE was flattening exponentially against TLC in the upper part of the curve. This "overdistension range" was found to be identical with the upper 40% of IC. Heavy side-effects of PEEP ventilation were never seen before the inspiratory volume excursion had reached this upper 40% of IC. If this was the case, the following observations were made: 1. Static compliance (Cst) decreased by more than 10% in all cases. 2. Pulmonary vascular resistance (PVR) increased by more than 20% in 12 cases. 3. Cardiac index (CI) decreased by more than 15% in 12 cases. 4. The alterations observed in Cst, PVR and CI increased rapidly, when the lungs were further distended, and were well correlated parabolically to the position of end-inspiratory volume within IC. --5 patients failed to show important circulatory alterations. It is concluded that overdistension-related side-effects of PEEP on respiratory mechanics and circulation do not occur before the linear part of the pressure-volume curve has been exceeded by hyperinflation. For the first adjustment of controlled ventilation at least the upper third of IC should be avoided.

Adolescent↗