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PubMed1998

Three-dimensional volumetric assessment of abnormally low attenuation of the lung from routine helical CT: inspiratory and expiratory quantification.

OBJECTIVE: The purpose of this investigation was to quantitatively assess abnormally low attenuation of the lung by use of three-dimensional volumetric reconstructions from routine helical CT and to assess their correlation with pulmonary function tests. MATERIALS AND METHODS: Helical CT was performed in 100 patients in full inspiration. Examination was also performed in full expiration in 53 of these patients. Three-dimensional volumetric reconstructions were performed for total lung volumes at inspiration and at expiration, with a threshold of -896 H on inspiratory CT and -790 H on expiratory CT, to quantify emphysematous change. Correlation was made with pulmonary function tests in 79 patients. RESULTS: CT volumetric assessments of abnormally low attenuation of the lung at inspiration and expiration had a high correlation (r2 = .84, p < or = .0001). In comparison with pulmonary function tests, both inspiratory low attenuation of the lung and expiratory low attenuation of the lung correlated well with the logarithm of the ratio of the forced expiratory volume in 1 sec (FEV1) to the forced vital capacity (r2 = .74, p < or = .0001 and r2 = .74, p < or = .0001, respectively) and with the percentage of predicted ratio of the FEV1 to the forced vital capacity (r2 = .69, p < or = .0001 and r2 = .69, p < or = .0001, respectively). Linear correlations were also seen with FEV1, residual volume, and forced residual capacity. CONCLUSION: Three-dimensional volumetric reconstructions of hypoattenuating lung correlate well with pulmonary function tests. In addition, inspiratory and expiratory data are also correlative, suggesting that a dedicated expiratory examination is not needed. This easily obtainable information will prove useful for patients with obstructive lung disease from emphysema, providing a measure of pulmonary function status in this population.

Adolescent↗
PubMed1978

Effect of force environment on regional pulmonary displacements and volumes in dogs.

Regional displacements of lung parenchyma due to respiratory movements at 1 G and 7 Gy were studied in anesthetized dogs in the left decubitus position in a water-filled respirator that provided control of respiratory volumes and rate and minimized inertial shifts in position and shape of the thorax and abdominal contents and related effects on the lungs. Inspiratory movements at 1 G were relatively uniform, although regional volume increased more in the nondependent (right) lung than in the dependent (left) lung. Regional functional residual capacity (FRC) increased in the nondependent lung and decreased in the dependent lung during exposures to 7 Gy. The greatest inspiratory increase in volume occurred near the midlung, where regional FRC changed the least during acceleration. The decrease in dependent and increase in nondependent lung volumes during acceleration are attributed to the increased weight and consequent downward displacement of the higher specific gravity mediastinal contents concomitantly with upward displacement of pulmonary gas, producing an exaggeration of the dependent-to-nondependent gradient in alveolar size.

Adaptation, Physiological↗
PubMed1992

A factor analysis of dyspnea ratings, respiratory muscle strength, and lung function in patients with chronic obstructive pulmonary disease.

The purpose of this study was to demonstrate that clinical ratings of dyspnea and physiologic function are separate dimensions underlying the pathophysiology of chronic obstructive pulmonary disease (COPD). We used principal-components factor analysis to confirm these dimensions using data collected prospectively in 86 symptomatic patients with COPD. Three different instruments were used to rate dyspnea: a modified Medical Research Council (MRC) scale, the oxygen cost diagram (OCD), and the baseline dyspnea index (BDI). Measures of physiologic function included standard spirometric measures (forced vital capacity [FVC] and forced expiratory volume in one second [FEV1]) and maximal inspiratory (PImax) and expiratory (PEmax) mouth pressures. Age of the 65 male and 21 female subjects was 62.9 +/- 1.2 yr (mean +/- SEM). All three clinical scales were significantly correlated with physiologic function (range of r values, 0.32 to 0.45; p less than 0.05), except for the relationship between the MRC scale and PEmax (r = -0.14; p = NS). The factor analysis yielded three factors that accounted for 71.9% of the total variance of the data: clinical ratings of dyspnea (MRC scale, OCD, and BDI) loaded on the first factor; maximal respiratory pressures and gender loaded on the second factor; and lung function and age loaded on the third factor. Additional post hoc factor analysis provided similar results when the sample was divided into two subgroups by randomization, by severity of dyspnea ratings, or by severity of airflow obstruction. We conclude that dyspnea ratings, maximal respiratory pressures, and lung function are separate factors or quantities that independently characterize the condition of patients with COPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Dyspnea↗
PubMed1987

Effects of expiratory resistive load on respiratory motor output in conscious humans.

We examined, in five conscious human subjects, the steady-state effects of expiratory resistive loading (ERL; R = 8 cmH2O.l-1.s) on the time course of inspiratory and postinspiratory muscle activities (IA and PIA, respectively) and ventilatory pattern during quiet breathing. Driving pressure (DP) was calculated by means of a respiratory neuromechanical model (J. Appl. Physiol. 51: 963-989, 1981) that permitted the derivation, from tidal volume and flow, of the occlusion pressure equivalent (at functional residual capacity) of respiratory neural output throughout the breath. ERL caused a prolongation of both neural inspiratory duration (12.2 +/- 6.9% SD) and expiratory duration (25.0 +/- 10.1%) and an increase in the amplitude of DP (16.5 +/- 10.2%) without any changes in the waveshape of IA and in end-expiratory level. The relative time course of PIA was not altered by ERL. Minute ventilation was depressed (-6.75 +/- 2.88%) during ERL with little change in alveolar PCO2. The results indicate that pulmonary gas exchange may be improved during ERL through increased tidal volume as well as delayed expiratory lung emptying secondary to sustained PIA.

Adult↗
PubMed1991

Maximum airflow through the nose in humans.

Inspiratory and expiratory flow via the nose and via the mouth during maximum-effort vital capacity (VC) maneuvers have been compared in 10 healthy subjects. Under baseline conditions maximum flow via the nose was lower than that via the mouth in the upper 50-60% of the VC on expiration and throughout the VC on inspiration. The mean ratio of maximum inspiratory to maximum expiratory flow at mid-VC was 1.38 during mouth breathing and 0.62 during nasal breathing. Inspiratory flow limitation with no increase in flow through the nose as driving pressure was increased above a critical value (usually between 12 and 30 cmH2O) was found in all six subjects studied. Stenting the alae nasi in seven subjects increased peak flow via the nose from a mean of 3.49 to 4.32 l/s on inspiration and from 4.83 to 5.61 l/s on expiration. Topical application of an alpha-adrenergic agonist in seven subjects increased mean peak nasal flow on inspiration from 3.25 to 3.89 l/s and on expiration from 5.03 to 7.09 l/s. Further increases in peak flow occurred with subsequent alan stenting. With the combination of stenting and topical mucosal vasoconstriction, nasal peak flow on expiration reached 81% and, on inspiration, 79% of corresponding peak flows via the mouth. The results demonstrate that narrowing of the alar vestibule and the state of the mucosal vasculature both influence maximum flow through the nose; under optimal conditions, nasal flow capacity is close to that via the mouth.

Adult↗
PubMed1983

A re-evaluation of the hemodynamic consequences of intermittent positive pressure ventilation.

The hemodynamic effects of intermittent positive pressure ventilation (IPPV) have generally been considered straightforward, being dominated by the inspiratory reduction in systemic venous return. Paradoxically, there is considerable debate regarding the effects of PEEP. We have studied both right ventricular (RV) and left ventricular (LV) performance during a single IPPV respiratory cycle in dogs with intact circulatory systems or the right heart bypassed in open and closed chest conditions. We have found that the "reverse pulsus paradoxus" during inspiration reflects both transmission of the increased intrathoracic pressure to the thoracic aorta and an increase in LV stroke volume (SV). This inspiratory increase in LVSV has been found to be influenced by, but not dependent on: (a) respiratory variations in RVSV; (b) variations in functional residual capacity or tidal volume altering pulmonary venous return and the degree of physical compression of the heart by the lungs; (c) an inspiratory decrease in RV volume, increasing LV diastolic compliance and, thus, probably improving pulmonary venous return; (d) a decreased transmural aortic diastole pressure reflecting an effective decrease in LV afterload produced by both the general increase in intrathoracic pressure and the direct compression of the heart; and (e) variations in the pulmonary vascular volume as indicated by changes in the transmural LV end-diastolic pressure. An understanding of IPPV during a single respiratory cycle facilitates an appreciation of the steady state hemodynamic effects of IPPV with or without PEEP. Our results imply that measurements made only at end-expiration, ignoring inspiratory events, may have serious limitations. Furthermore, they suggest that IPPV with PEEP should be evaluated as a form of LV assist in LV failure.

Animals↗
PubMed1990

Importance of inspiratory flow rate in the cough response to citric acid inhalation in normal subjects.

1. The cough response to inhalation of citric acid is produced mainly by irritation of the larynx and trachea. Variations in the inspiratory flow rate might lead to changes in deposition of the drug, and consequently in the cough threshold. 2. We have studied the effect of three different inspiratory flow rates in 11 normal, non-smoking subjects (nine males, aged 23-39 years), who inhaled nebulized citric acid (2.5-640 mg/l). The test finished when a cough was produced at each inhalation (cough threshold) or the maximum concentration was reached. 3. The inspiratory flow rate was limited with a fixed resistance and displayed on a screen so that the subjects could reach a constant inspiratory flow rate of 50, 100 and 150 l/min with a submaximal inspiratory effort. 4. The mean (SD) inspiratory flow rates achieved were 51.4 (5.3), 86.2 (16.6) and 134.4 (22.9) l/min. Baseline forced expiratory volume in 1 s and functional vital capacity were not different on the 3 study days. 5. The cough threshold (geometric mean and 95% confidence intervals) was 21 (9-54) mg/l at an inspiratory flow rate of 50 l/min and 43 (13-141) mg/l at 150 l/min (P less than 0.05). The amount of drug tolerated by the subjects before the cough threshold was achieved was 5.2 (2.0-13.8) mg at an inspiratory flow rate of 50 l/min and 11.6 (3.4-39.8) mg at 150 l/min (P less than 0.05). The number of coughs per inhalation was 1.6 (1.1-2.0) at an inspiratory flow rate of 50 l/min and 1.1 (0.7-1.5) at 150 l/min (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2006

Maximum static inspiratory and expiratory pressures with different lung volumes.

BACKGROUND: Maximum pressures developed by the respiratory muscles can indicate the health of the respiratory system, help to determine maximum respiratory flow rates, and contribute to respiratory power development. Past measurements of maximum pressures have been found to be inadequate for inclusion in some exercise models involving respiration. METHODS: Maximum inspiratory and expiratory airway pressures were measured over a range of lung volumes in 29 female and 19 male adults. A commercial bell spirometry system was programmed to occlude airflow at nine target lung volumes ranging from 10% to 90% of vital capacity. RESULTS: In women, maximum expiratory pressure increased with volume from 39 to 61 cmH2O and maximum inspiratory pressure decreased with volume from 66 to 28 cmH2O. In men, maximum expiratory pressure increased with volume from 63 to 97 cmH2O and maximum inspiratory pressure decreased with volume from 97 to 39 cmH2O. Equations describing pressures for both sexes are: Pe/Pmax = 0.1426 Ln( %VC) + 0.3402 R2 = 0.95 Pi/Pmax = 0.234 Ln(100 - %VC) - 0.0828 R2 = 0.96 CONCLUSION: These results were found to be consistent with values and trends obtained by other authors. Regression equations may be suitable for respiratory mechanics models.

Adult↗
PubMed1995

Muscle strength, symptom intensity, and exercise capacity in patients with cardiorespiratory disorders.

The contribution of muscle strength to symptom intensity and work capacity was examined in normal individuals and patients with cardiorespiratory disorders. Respiratory muscle strengths (maximal inspiratory and expiratory pressures) and peripheral muscle strengths (leg extension, leg flexion, seated bench press, and seated row) were measured in 4,617 subjects referred for clinical exercise testing. Subjects then rated the intensity of leg effort, discomfort with breathing (dyspnea), and chest pain (Borg scale) during an incremental exercise task (100 kpm/min each minute) to capacity on a cycle ergometer. Subjects were classified into groups on the basis of pulmonary function, drug therapy for cardiac disorders, and the presence of chest pain during exercise with electrocardiographic changes indicative of myocardial ischemia. Respiratory and peripheral muscle strengths, normalized for differences in age, sex, and height, were significantly reduced in patients with cardiorespiratory disorders compared with normal individuals. Muscle strength was a significant contributor to symptom intensity and work capacity in both health and disease; a two-fold increase in muscle strength was associated with a 25 to 30% decrease in the intensity of both leg effort and dyspnea and a 1.4- to 1.6-fold increase in work capacity. These results emphasize the need for an integrative approach in the assessment and therapeutic management of exercise intolerance, which considers the contribution of muscle weakness to excessive symptoms and reduced work capacity, in addition to the contribution of ventilatory, gas exchange, and circulatory impairments.

Angina Pectoris↗
PubMed1997

Respiratory muscle function and control of breathing in patients with acromegaly.

Increase in lung size has been described in acromegalic patients, but data on respiratory muscle function and control of breathing are relatively scarce. Lung volumes, arterial blood gas tensions, and respiratory muscle strength and activation during chemical stimulation were investigated in a group of 10 patients with acromegaly, and compared with age- and sex-matched normal controls. Inspiratory muscle force was evaluated by measuring pleural (Ppl,sn) and transdiaphragmatic (Pdi,sn) pressures during maximal sniffs. Dynamic pleural pressure swing (Ppl,sw) was expressed both as absolute value and as percentage of Ppl,sn. Expiratory muscle force was assessed in terms of maximal expiratory pressure (MEP). In 8 of the 10 patients, ventilatory and respiratory muscle responses to hyperoxic progressive hypercapnia and to isocapnic progressive hypoxia were also evaluated. Large lungs, defined as total lung capacity (TLC) greater than predicted (above 95% confidence limits), were found in five patients. Inspiratory or expiratory muscle force was below normal limits in all but three patients. During unstimulated tidal breathing, respiratory frequency (fR) and mean inspiratory flow (tidal volume/inspiratory time (VT/tI)) were greater, while inspiratory time (tI) was shorter than in controls. Minute ventilation (V'E) and mean inspiratory flow response slopes to hypercapnia were normal In contrast, four patients had reduced delta(VT/tI)/arterial oxygen saturation (Sa,O2) and three had reduced deltaV'E/Sa,O2. Ppl,sw(%Ppl,sn) response slopes to increasing end-tidal carbon dioxide tension (PET,CO2) and decreasing Sa,O2 did not differ from the responses of the normal subjects, suggesting normal central chemoresponsiveness. At a PET,CO2 of 8 kPa or an Sa,O2 of 80%, patients had greater fR and lower tI compared with controls. Pdi,sn and Ppl,sn related both to deltaV'E/deltaSa,O2 (r=0.729 and r=0.776, respectively) and delta(VT/tI)/deltaSa,O2 (r=0.860 and r=0.90, respectively). Pdi,sn also related both to deltaV'E/deltaPET,CO2 (r=0.8) and delta(VT/tI)/deltaPET,CO2 (r=0.76). In conclusion, the data suggest the relative independence of pneumomegaly and respiratory muscle strength. Peripheral (muscular) factors appear to modulate a normal central motor output to give a more rapid pattern of breathing.

Acromegaly↗
PubMed1999

Effect of lung volume reduction surgery on bony thorax configuration in severe COPD.

STUDY OBJECTIVES: Hyperinflation in patients with severe COPD is associated with an increased anteroposterior (AP) rib cage diameter. We sought to determine whether bilateral lung volume reduction surgery (LVRS) affects bony thorax configuration. DESIGN: Prospective of clinical data collection before and after LVRS. SETTING: Tertiary-care university medical center. PATIENTS: We measured multiple AP and transverse thoracic diameters, by using plain chest roentgenograms (CXRs) in 25 patients (11 men, 14 women), and thoracic CT scans in 14 patients (7 men, 7 women), preoperatively and 3 months postoperatively. A subgroup of 7 patients (reference data) also had CXR thoracic diameter measurements made, using films obtained previously within a year of their presurgical evaluation. Another subgroup of 10 patients had CT scan measurements also made 12 months postoperatively. MEASUREMENTS AND RESULTS: CXR dimensions were taken at the level of the manubrium sterni (M) and thoracic T7 and T11 levels. CT dimensions were taken at T4, T6, T8, and T10 levels. At each level, left (L), midsagittal (C), and right (R) AP and maximal transverse diameters were measured. The sum of the three AP diameters (Total) was used for calculations. Patients also underwent tests such as spirometry, lung volumes, diffusing capacity of the lung for carbon monoxide, 6-min walk distance (6MWD), and transdiaphragmatic pressures during maximum static inspiratory efforts (Pdimax sniff) measured before and 3 months after LVRS. Patients were (mean +/- SD) 58+/-8 years old, with severe COPD and hyperinflation (FEV1, 0.68+/-0.23 L; FVC, 2.56+/-7.3 L; and total lung capacity [TLC], 143+/-22% predicted). After LVRS, AP diameters were reduced at thoracic level T7 (from 24.2+/-2.0 cm to 23.3+/-2.2 cm, p = 0.0002), and transverse diameters were reduced at T7 (from 26.8+/-1.9 cm to 26.4+/-1.7 cm, p = 0.001) and T11 (from 29.9+/-2.2 cm to 29.5+/-2.2 cm, p = 0.03), as measured using the CXR. In contrast, thoracic diameters were similar in subjects with CXRs before LVRS and within 1 year before evaluation. CT-measured AP diameters were significantly reduced 3 months after LVRS at T6, (from 48.8+/-6.0 cm to 46.7+/-5.4 cm, p = 0.02), T8 (from 54.2+/-7.0 cm to 52.3+/-6.5 cm, p = 0.004), and T10 (from 53.8+/-7.5 cm to 51.2+/-8.0 cm, p = 0.001), but not at T4. These AP diameter reductions directly correlated with the postoperative reductions in TLC and residual volume, and also with the increases in Pdimax sniff and 6MWD after LVRS. The reduction in AP diameters at thoracic levels T8 and T10 seen 3 months after LVRS remained stable at 12-month follow-up, whereas those measured at T6 lost statistical significance. CT-measured transverse diameters were unchanged at all levels after LVRS. CONCLUSIONS: We conclude that LVRS decreases mid-to-lower AP rib cage diameter as assessed by CXR and thoracic CT. Although transverse diameters were reduced on CXR, the magnitude was small and was not confirmed with CT. After LVRS, AP diameter reductions are most likely the result of reduction in lung volume, and they are associated with improvements in diaphragm strength and exercise endurance.

Female↗
PubMed1996

Lung mechanics during induced bronchoconstriction.

To elucidate differences in lung mechanics, we investigated the relative changes of partial forced expiratory flows at 50 and 30% of vital capacity, pulmonary resistance (RL), dynamic elastance (Edyn), and the effects of a deep inhalation (DI) on maximal flows, Edyn, and RL in eight asthmatic and eight normal individuals during bronchial challenges with methacholine, histamine, and ATP. RL was partitioned into inspiratory and expiratory resistance. Different constrictor agents did not induce specific patterns of response. For a given decrement of flow at 50 and 30% vital capacity, RL increased significantly more in normal than in asthmatic individuals. The ratio of inspiratory to expiratory RL was always < 1 at baseline but became > 1 in the majority of asthmatic and normal individuals when RL exceeded 12.2 +/- 0.9 cmH2O.1-1.s, suggesting that tidal inspiration may have induced transient bronchodilation in more constricted subjects. In asthmatic individuals, DI had a significantly smaller effect on flow but not on RL compared with normal individuals. The recovery of RL and Edyn after DI was faster than Edyn for both normal and asthmatic individuals. These findings are consistent with the idea that asthmatic individuals have a stronger peripheral response to agonists than normal individuals.

Adenosine Triphosphate↗
PubMed1990

Effects of inspiratory and expiratory time and high mouth pressures on calculated DLCO by the single-breath procedure. Results with different methods to measure the effective breath-holding time.

We have studied the influence of several manoeuvres modifying inspiratory and expiratory flow, with and without an external obstruction, on measured single-breath diffusing capacity (DLCO). By this method, we could evaluate the effects of increased inspiration or expiration time, independently of the influence of high (negative or positive) mouth pressures. Ten tests were performed in each of 11 trained normal subjects. The sequence of repeated manoeuvres was as follows: (1) basal; (2) inspiratory obstruction (IO); (3) expiratory obstruction (EO); (4) slow inspiration without obstruction (SI), and (5), slow expiration without obstruction (SE). A second, inverted sequence was then performed. The obstructive manoeuvres were forced by a unidirectional valve with a circular hole of 5 mm in diameter. Mouth pressures were registered. The slow flows were voluntarily controlled to be similar to the corresponding flows during the obstructive manoeuvre (approximately 15% of each vital capacity/second). Determinations of breath-holding time (tBH) were calculated by the methods of Jones-Meade, Ogilvie and the American Epidemiology Standardization Project (ESP), but using the same expiratory sample. We found that (DLCO) obtained with the three methods were statistically different (p less than 0.0001) from each other for all manoeuvres. Regarding the basal manoeuvre, there were statistical differences (p less than 0.01) with SI on the Jones-Meade, with IO on the ESP and with SI and IO on the Ogilvie timing methods. Between IO and SI, statistical differences (p less than 0.01) were observed in the three methods, but there was no statistical difference between SE and EO by any method.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMedDate not supplied

Maximal static pressures and lung volumes in young female swimmers: one year follow-up.

The relationship between the growth of lung volumes and the development of maximal static pressures was examined in a 1 year follow-up study of 17 female swimmers, initially less than 12 years of age. Lung volumes were measured by body plethysmography, and maximal static inspiratory and expiratory pressures were generated near residual volume, at functional residual capacity and near total lung capacity (TLC). The results were compared to the regressions obtained from cross-sectional data generated on 59 girls randomly selected from a local school. Height was similar in swimmers and controls. Vital capacity and total lung capacity increased during the year to exceed normal limits in 11 of 17 swimmers. The only significant increase of maximal static pressures during 1 year occurred in expiration near TLC in those swimmers initially less than 10 years of age, and all pressures fell within normal limits. We conclude that large lung volumes in swimmers cannot be accounted for by an increased ability to inflate and deflate the lung by the respiratory muscles.

Age Factors↗
PubMed1992

Pulmonary function and resting breathing pattern in myotonic dystrophy.

In 17 patients with myotonic dystrophy, spirometric, flow-volume, and maximal mouth occlusion variables were obtained and compared with 8 normal subjects. Ventilatory CO2 response was measured by the estimation of the steady-state effect of a sufficiently large serial dead space. Variability of resting breathing pattern was expressed by the variation coefficients of respiratory cycle time and tidal volume. The group means of the total lung capacity (TLC), vital capacity (VC), forced expiratory volume in 1 sec (FEV)1 and forced inspiratory volume in 1 sec (FIV)1 showed a restrictive pattern. Only maximal static mouth pressure (Pi,max), measured at residual volume (RV) level, showed a significant positive correlation with both VC (p = 0.03) and FIV1 (p = 0.02), suggesting inspiratory muscle weakness as a determinant of the restriction. Although the differences were just not significant, both variation coefficients of the respiratory cycle time and tidal volume were larger in the group with a CO2 sensitivity below the lower limit of normal compared to those with a normal ventilatory response to CO2. In 3 patients, fluctuations in FRC were also present. We hypothesize that, in addition to the already documented FRC fluctuations by uncoordinated spontaneous intercostal muscle action, a defect of integration of afferent neural input and chemical drive in the medullary region may also be present in these patients.

Adult↗
PubMed1996

Weaning and extubation in the intensive care unit. Clinical or index-driven approach?

OBJECTIVE: To assess the outcome of a clinical judgement-based approach to weaning and extubation and to adduce the predictive accuracy of various mechanical respiratory indices measured in parallel. DESIGN: Prospective study. SETTING: Multidisciplinary intensive care unit at a university teaching hospital. PATIENTS: 163 consecutive mechanically ventilated patients, excluding tracheotomy, for weaning trial and extubation. INTERVENTIONS: Using bedside clinical assessment, aided by arterial gas analysis, patients were weaned from mechanical ventilation to spontaneous ventilation via to continuous positive airway pressure (CPAP) circuit (with pressure support) of a microprocessor-controlled ventilator. Extubation occurred from the CPAP circuit at 7 cmH2O pressure support, fractional inspired oxygen (FIO2) < or = 0.5 and CPAP level of < or = 5 cmH2O, such that the partial pressure of oxygen in arterial blood (PaO2) was > or = 65 mmHg. Before extubation, observation for a 1-h (T0 and T60) trial period allowed measurement of vital capacity (VC), expired minute volume (VE), respiratory rate/tidal volume (f/VT) and maximal inspiratory pressure (MIP) using a one-way valve technique over 25 s. MEASUREMENTS AND MAIN RESULTS: Over 7 months, 163 patients (62 females and 101 males; mean (SD) age 64(15) years) were considered. There were 91 surgical (18 with chronic obstructive pulmonary disease; COPD) and 72 medical (28 with COPD) patients. Ventilation was for > or = 1 day (median 5 days, range 1-31) in 115 [group I; APACHE II score 23(8)] and < or = 1 day in 48 [Group II; APACHE II score 17(6)]. Three patients (all Group I: 2 surgical, 1 medical) were reintubated within 24 h, an overall extubation failure rate of 1.8%. In group I, at T0, PaO2/FIO2 was 238(65), f/VT 50(26), MIP 44(21) cmH2O, VE 10.6(3.7) l/min, VC 13(5) ml/kg. Cardiorespiratory variables did not change significantly in either group, T0 to T60. For prediction of reintubation (n = 163), only VE (threshold > 10 l/min) and f/VT (threshold > 100) demonstrated moderate sensitivity and specificity at T60: 67 and 52% and 33 and 94%, respectively. CONCLUSIONS: Bedside clinical judgement of weaning and extubation produces satisfactory outcomes. As a routine, mechanical predictive indices have limited utility.

APACHE↗
PubMed1997

Polysomnographic studies in amyotrophic lateral sclerosis.

We retrospectively reviewed 17 polysomnograms (PSG) in symptomatic amyotrophic lateral sclerosis (ALS) patients to assess the type and frequency of sleep disordered events and correlated these findings with pulmonary function tests (PFTs), presenting complaints, presence of bulbar dysfunction, and response to bi-level positive airway pressure (PAP) treatment. PSG revealed abnormalities in 16 patients. Complaints of orthopnea, daytime sleepiness (but not morning headaches) and a low negative inspiratory force (NIF) correlated with sleep disruption. However, neither the forced vital capacity (FVC) nor the NIF reliably predicted any specific PSG finding. Twelve of 13 patients treated with bi-level PAP responded favorably. Since the response to bi-level PAP is frequently gratifying, PSG should strongly be considered in ALS patients with suspected sleep disturbances.

Adolescent↗
PubMed2002

3He-MRI-based vs. conventional determination of lung volumes in patients after unilateral lung transplantation: a new approach to regional spirometry.

BACKGROUND: To use 3Helium (3He)-MRI in patients with unilateral lung grafts to assess the contributions of graft and native lung to total ventilated lung volume, and second to compare conventional measurements of intrapulmonary gas volume (spirometry, body plethysmography) with image-based volumetry of ventilated lung parenchyma visualized by hyperpolarized 3He-MRI. METHODS: With Ethics Committee approval, five patients with single lung transplantation (SLTX) for idiopathic pulmonary fibrosis (IPF) underwent both conventional pulmonary function testing (PFT) and 3He-MRI of the lung. Intrapulmonary gas volume (GV) during the inspiratory breathhold for 3He-MRI was calculated from measured functional residual capacity (corrected for supine position) and inspired tidal volume. Image-based global and regional lung volumetries (LV) were performed in three-dimensionally reconstructed 3He-MR images (corrected for the fraction of tissue and blood). RESULTS: Transplanted lungs were characterized by a homogeneous distribution of signal intensity, whereas the native lungs of the patients suffering from IPF displayed an inhomogeneous signal distribution pattern with numerous round or wedge-shaped ventilation defects. Total ventilated lung volume determined by 3He-MRI correlated well with PFT-based measurements, but with a systematic overestimation of the 3He-based lung volumetry of approximately 20%. Functioning lung grafts contributed 66+/-6% and their corresponding native IPF lungs 34+/-6% to total ventilated volume (P<0.05; mean+/-SD). CONCLUSION: 3Helium-MRI of the lung offers a novel approach to regional determination of ventilated lung volume, including its blood and tissue compartments. The advantage of this technique over computed tomography or ventilation scintigraphy is the lack of radiation exposure, and hence its repeatability. Follow up of SLTX patients with this new technique may allow the monitoring of functional and structural developments of grafted lungs with better sensitivity and specificity than PFT.

Female↗