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PubMed1995

Pulmonary function abnormalities in Prader-Willi syndrome.

OBJECTIVE: To determine whether individuals with Prader-Willi syndrome (PWS) have abnormalities in pulmonary function as a result of thoracic muscle weakness. DESIGN: Testing of spirometry, flow-volume curves, lung volumes, and static respiratory pressures was performed in patients with PWS who are followed at the University of Connecticut. All tests were performed in triplicate on two or more occasions. Only reproducible tests were accepted. Established normative data were applied for all test results. RESULTS: A total of 18 male subjects (age, 17.9 +/- 10.2 years (mean +/- SD); range, 5-39 years) and 17 female subjects (age, 23.5 +/- 13.0 years; range, 5-54 years) completed the tests. Forced vital capacity and forced expiratory volume in 1 second were reduced; the forced expiratory volume in 1 second/forced vital capacity ratio was normal, total lung capacity was in the low normal range, and residual volume was elevated. Maximum inspiratory (PImax) and expiratory (PEmax) pressures were markedly reduced in 32 subjects tested. Fifteen subjects had PEmax values and 20 subjects had PImax values < 60 cm H2O, respectively. There was a linear correlation between forced expiratory volume in 1 second and both PImax and PEmax (r = 0.71; r = 0.62, respectively), and between forced vital capacity and both PEmax and PImax (r = 0.62 and r = 0.74, respectively). There was an inverse relationship between both PImax and PEmax, and residual volume (r = 0.47 and r = 0.72, respectively). CONCLUSION: Children and adults with PWS have restrictive ventilatory impairment primarily as a result of respiratory muscle weakness. Efforts to improve thoracic muscle strength may be useful in improving pulmonary function in individuals with PWS.

Adolescent↗
PubMed2005

Shape and tension distribution of the active canine diaphragm.

Both diaphragm shape and tension contribute to transdiaphragmatic pressure, but of the three variables, tension is most difficult to measure. We measured transdiaphragmatic pressure and the global shape of the in vivo canine diaphragm and used principles of mechanics to compute the tension distribution. Our hypotheses were that 1) tension in the active diaphragm is nonuniform with greater tension in the central tendon than in the muscular regions; 2) maximum tension is essentially oriented in the muscle fiber direction, whereas minimum tension is orthogonal to the fiber direction; and 3) during submaximal activation change in the in vivo global shape is small. Metallic markers, each 2 mm in length, were implanted surgically on the peritoneal surface of the diaphragm at 1.5- to 2.0-cm intervals along the muscle bundles at the midline, ventral, middle, and dorsal regions of the left costal diaphragm and along a muscle bundle of the crural diaphragm. Postsurgery, a biplane videofluoroscopic system was used to determine the in vivo three-dimensional coordinates of the markers at end expiration and end inspiration during quiet breathing as well as at end-inspiratory efforts against an occluded airway at lung volumes of functional residual capacity and at one-third maximum inspiratory capacity increments in volume to total lung capacity. A surface was fit to the marker locations using a two-dimensional spline algorithm. Diaphragm surface was modeled as a pressurized membrane, and tension distribution in the active diaphragm was computed using the ANSYS finite element program. We showed that the peak of the diaphragm dome was closer to the ventral surface than to the dorsal surface and that there was a depression or valley in the crural region. In the supine position, during inspiratory efforts, the caudal displacement of the dorsal region of the diaphragm was greater than that of the dome, and the valley along the crural diaphragm was accentuated. In contrast, at lower lung volumes in the prone posture, the caudal displacement of the dome was greater than that of the crural region. At end of inspiration, transdiaphragmatic pressure was approximately 6.5 cmH2O, and tensions were nonuniform in the diaphragm. Maximum principal stress sigma(1) of central tendon was found to be greater than sigma(1) of the costal region, and that was greater than sigma(1) of the crural region, with values of 14-34, 14-29, and 4-14 g/cm, respectively. The corresponding data of the minimum principal stress sigma(2) were 9-18, 3-9, and 0-1.5 g/cm, respectively. Maximum principal tension was approximately parallel to the muscle fibers, whereas minimum tension was essentially orthogonal to the longitudinal direction of the muscle fibers. In the muscular region, sigma(1) was approximately 3-fold sigma(2), whereas in the central tendon, sigma(1) was only approximately 1.5-fold sigma(2.).

Animals↗
PubMed2005

The deflation limb of the pressure-volume relationship in infants during high-frequency ventilation.

RATIONALE: The importance of applying high-frequency oscillatory ventilation with a high lung volume strategy in infants is well established. Currently, a lack of reliable methods for assessing lung volume limits clinicians' ability to achieve the optimum volume range. OBJECTIVES: To map the pressure-volume relationship of the lung during high-frequency oscillatory ventilation in infants, to determine at what point ventilation is being applied clinically, and to describe the relationship between airway pressure, lung volume, and oxygenation. METHODS: In 12 infants, a partial inflation limb and the deflation limb of the pressure-volume relationship were mapped using a quasi-static lung volume optimization maneuver. This involved stepwise airway pressure increments to total lung capacity, followed by decrements until the closing pressure of the lung was identified. MEASUREMENTS AND MAIN RESULTS: Lung volume and oxygen saturation were recorded at each airway pressure. Lung volume was measured using respiratory inductive plethysmography. A distinct deflation limb could be mapped in each infant. Overall, oxygenation and lung volume were improved by applying ventilation on the deflation limb. Maximal lung volume and oxygenation occurred on the deflation limb at a mean airway pressure of 3 and 5 cm H(2)O below the airway pressure approximating total lung capacity, respectively. CONCLUSIONS: Using current ventilation strategies, all infants were being ventilated near the inflation limb. It is possible to delineate the deflation limb in infants receiving high-frequency oscillatory ventilation; in doing so, greater lung volume and oxygenation can be achieved, often at lower airway pressures.

High-Frequency Ventilation↗
PubMed1975

Idiopathic scoliosis. Mechanical properties of the respiratory system and the ventilatory response to carbon dioxide.

The aims were to examine the effects of scoliosis (angle), and age on lung volumes, elastic properties of the respiratory system, and the ventilatory response to CO2. The mean age of the 55 patients was 25.4 plus or minus SEM 2.5 yr, and the mean angle was 80 plus or minus SEM 4.2. The mean plus or minus SEM percent predicted lung volumes were vital capacity (VC), 60.5 plus or minus 2.7; total lung capacity (TLC), 70,2 plus or minus 2.6; functional residual capacity (frc), 79.3 plus or minus 3.2; and residual volume (RV), 99.7 plus or minus 5.2. The correlation coefficients between the angle of scoliosis and each of the following were significant: TLC (-0.548), percent predicted TLC (-0.547), VC (-0.485), percent predicted VC (-0.523), FRC (-0.533), percent predicted FRC (-0.338), RV (-0.438), and percent predicted RV (-0.318). The mean compliance of the total respiratory system (Crs) was 0.049 litter/cm H2O plus or minus SEM 0.004, and the mean compliance of the chest wall (Ccw) was 0.080 liter/cm H2O plus or minus SEM 0.012. The Crs and Ccw were inversely proportional to the angle (r-0.620 and -0.721) and directly proportional to the height and the weight. The mean deltaV/deltaPco2 was 1.32 liter/min per mm Hg (SEM 0.171), and the mean deltaVt/deltaPco2 was 28.9 ml/mm Hg (SEM 3.64). The correlation coefficients between deltaV/deltaPco2 and the following were height, 0.499; VC, 0.792; TLC, 0.632; AND Crs, 0.520; and between the deltaTt/deltaPco2 and the following were height, 0.500; VC, 0.878; TLC, 0.802; and Crs, 0.590. We conclude that body size and the deformity were the determinants of the lung volumes and the mechanical properties of the respiratory system, and that these variables were the major factors in both the magnitude and pattern of the ventilatory response to CO2. The correlations between age and the mechanical properties of the respiratory sytem, deltaV/deltaPco2, and deltaVt/deltaPco2, were not significant, but the correlation coefficients between age and several of the derivatives of deltaV/deltaPco2 and deltaVt/deltaPco2 were significant.

Adolescent↗
PubMed1992

Volume infusion produces abdominal distension, lung compression, and chest wall stiffening in pigs.

The effect of severe generalized edema on respiratory system mechanics is not well described. We measured airway pressure, gastric pressure, and four vertical pleural pressures in 13 anesthetized paralyzed pigs ventilated in the upright position. Pressure-volume relationships of the respiratory system, chest wall, and lung were measured on deflation from total lung capacity to residual volume and during tidal breathing both before (control) and 50 min after one of two interventions. In one series of experiments, a volume equal to 15-20% of the pig's body weight was infused intravenously. In a second series, a balloon was placed in the peritoneal space to distend the abdomen to the same gastric pressures as achieved in the first series. Measurements were compared before and after either abdominal balloon inflation or volume infusion. Volume infusion increased the pleural pressure in dependent lung regions, decreased both total lung capacity (34%) and functional residual capacity (62%) (both P less than 0.05), and markedly shifted the respiratory system and chest wall pressure-volume curves to the right, but it only moderately affected the lung deflation curve. Tidal compliances of the respiratory system, chest wall, and lung decreased 36, 31, and 49%, respectively (all P less than 0.05). The effect of abdominal balloon inflation on respiratory system mechanics was similar to that of volume infusion. We conclude that infusing large volumes of fluid markedly alters chest wall mechanics, mainly by causing abdominal distension that prohibits descent of the diaphragm.

Abdomen↗
PubMed1996

Thoracoscopic sympathicolysis for essential hyperhidrosis: effects on pulmonary function.

Bilateral interruption of the upper dorsal sympathetic chain at the D2 and D3 level represents the only permanent cure for essential hyperhidrosis. Following surgical sympathectomy, significant and symptomatic changes in pulmonary function have been observed. Since functional effects of the surgical intervention cannot be excluded, we wondered whether such alterations also occurred after thoracoscopic sympathicolysis; these should then be attributable to the surgical denervation itself. Pulmonary function tests (PFTs), including spirometry and body plethysmographic measurement of lung volumes and airway resistance and conductance, were compared before and 6 weeks after thoracoscopic sympathicolysis in 47 patients. In order to virtually exclude any effects of thoracoscopy on the test results PFTs were repeated 6 months after thoracoscopic sympathicolysis in 35 patients. Essential hyperhidrosis was completely relieved in all patients, thereby confirming the interruption of the D2-D3 sympathetic chain. None of the patients developed respiratory symptoms after thoracoscopic sympathicolysis. Forced expiratory volume in one second (FEV1) (-3%), forced expiratory flow after exhaling 75% of vital capacity (FEF75) (-8%) and total lung capacity (TLC) (-3%) were slightly but significantly reduced at six weeks after thoracoscopic sympathicolysis; whereas airway resistance (Raw) had increased (+12%). After correction for the small decrease in lung volume (FEV1/forced vital capacity (FVC), specific airway resistance (sRaw), specific airway conductance (sGaw))significant changes in "volume-dependent" PFT parameters were no longer observed. Smoking status had no influence on the reduction in FEF75. At 6 months after thoracoscopic sympathicolysis, TLC had returned to preoperative values, whereas FEF75 remained decreased (-8.6%). The decrease in airway calibre was confirmed by small but significant changes in FEV1/FVC (-2%) and Raw (+29%). We conclude that thoracoscopic sympathicolysis in patients with essential hyperhidrosis causes only minimal and subclinical changes in pulmonary function secondary to a temporary small decrease in lung volume, which in turn is probably inherent to the thoracoscopic procedure. D2-D3 sympathicolysis, in itself, is responsible only for a small and permanent decrease in forced expiratory flow, which suggests that, at least in essential hyperhidrosis patients, airway bronchomotor tone is influenced by sympathetic innervation.

Adolescent↗
PubMed2001

Prognosis of patients with advanced idiopathic pulmonary fibrosis requiring mechanical ventilation for acute respiratory failure.

STUDY OBJECTIVE: To evaluate the beneficial effect of mechanical ventilation (MV) in patients with idiopathic pulmonary fibrosis (IPF) who develop acute respiratory failure (ARF), with special emphasis on prognosis. DESIGN: Retrospective study. SETTING: Ten-bed respiratory ICU that is a part of a respiratory department actively involved in lung transplantation (LTx). PATIENTS: From 1991 to 1999, 23 patients (mean age, 52.9 years; range, 21 to 82 years) with IPF required MV for ARF. At admission to the ICU, 16 patients were potential candidates for LTx, with 5 patients already on the waiting list. MEASUREMENTS AND RESULTS: Survival and gas exchange under MV were assessed. The precipitating cause of ARF was also analyzed. With the exception of 1 patient who successfully received a single-lung transplant 6 h after initiation of MV, all the remaining 22 patients died while receiving MV (median survival, 3 days; range, 1 h to 60 days). The duration of MV correlated positively with baseline vital capacity (percent predicted) (R = 0.54; p = 0.01) and baseline total lung capacity (percent predicted) (R = 0.71; p < 0.001), and correlated negatively with baseline PaCO(2) (R = - 0.47; p = 0.03) and the duration of evolution of IPF (R = -0.50; p = 0.01). Duration of MV did not correlate with the duration of immunosuppressive therapy (R = - 0.24; p = 0.27) or duration of oxygen therapy (R = - 0.32; p = 0.14) prior to admission. The precipitating cause of ARF was most often not identified. CONCLUSIONS: Our data support the general belief that MV does not benefit IPF patients presenting with ARF. Initiation of MV in IPF patients is thus questionable and should, in our opinion, be restricted to patients in whom LTx can be performed within a few days after initiation of MV.

Acute Disease↗
PubMed2005

Measurement of neural respiratory drive in patients with COPD.

Assessment of neural respiratory drive may be useful in patients with chronic obstructive pulmonary disease (COPD) for diverse clinical and academic reasons. We hypothesised that the oesophageal diaphragm EMG during CO2 rebreathing and treadmill exercise could be used for this purpose. The oesophageal catheter consisted of nine consecutive recording electrode coils, which formed five pairs of electrodes with an inter-electrode distance 3.2 cm within a recording pair. Each coil was 1cm in length and the gap between adjacent coils was 0.5 mm. Maximal isometric contractions at functional residual capacity (FRC) and maximal voluntary inspirations from FRC to total lung capacity (TLC) were performed. All subjects performed CO2 rebreathing until end-tidal CO2 was approximately 9% or they became intolerably breathless. There was a good linear relationship between peak of root mean square (RMS) of the diaphragm EMG and end-tidal CO2 (r = 0.92 +/- 0.06) during CO2 rebreathing. The method was also shown to be feasible during exercise. It is concluded that the diaphragm EMG recorded from an oesophageal electrode is a useful technique to assess neural respiratory drive in patients with COPD.

Aged↗
PubMed1991

Effect of mean airway pressure on gas exchange during high-frequency oscillatory ventilation.

We studied the effect of mean airway pressure (Paw) on gas exchange during high-frequency oscillatory ventilation in 14 adult rabbits before and after pulmonary saline lavage. Sinusoidal volume changes were delivered through a tracheostomy at 16 Hz, a tidal volume of 1 or 2 ml/kg, and inspired O2 fraction of 0.5. Arterial PO2 and PCO2 (PaO2, PaCO2), lung volume change, and venous admixture were measured at Paw from 5 to 25 cmH2O after either deflation from total lung capacity or inflation from relaxation volume (Vr). The rabbits were lavaged with saline until PaO2 was less than 70 Torr, and all measurements were repeated. Lung volume change was measured in a pressure plethysmograph. Raising Paw from 5 to 25 cmH2O increased lung volume by 48-50 ml above Vr in both healthy and lavaged rabbits. Before lavage, PaO2 was relatively insensitive to changes in Paw, but after lavage PaO2 increased with Paw from 42.8 +/- 7.8 to 137.3 +/- 18.3 (SE) Torr (P less than 0.001). PaCO2 was insensitive to Paw change before and after lavage. At each Paw after lavage, lung volume was larger, venous admixture smaller, and PaO2 higher after deflation from total lung capacity than after inflation from Vr. This study shows that the effect of increased Paw on PaO2 is mediated through an increase in lung volume. In saline-lavaged lungs, equal distending pressures do not necessarily imply equal lung volumes and thus do not imply equal PaO2.

Animals↗
PubMed1996

Effect of surgical lung volume reduction on respiratory muscle function in pulmonary emphysema.

Lung volume reduction surgery (LVRS) in patients with severe lung emphysema restores the thoracic configuration to a more normal functional capacity. The aim of this study was to investigate whether reduction in intrathoracic volume by LVRS improves the inspiratory muscle force generation of the respiratory pump. Pulmonary function tests, maximal inspiratory mouth pressure (MIP), sniff nasal inspiratory pressure (SNIP), sniff transdiaphragmatic pressure (Pdi), and inspiratory mouth occlusion pressure (P0.1) were measured in 17 emphysematous patients (mean (+/- SEM) age 53 +/- 2 yrs) before and 1 month after LVRS. The mean value of forced expiratory volume in one second (FEV1) increased (0.82 +/- 0.07 vs 1.12 +/- 0.08 L; p < 0.0001), whilst there was a decrease (p < 0.0001) in residual volume (RV) (337 +/- 31 vs 250 +/- 21 % of predicted), functional residual capacity (FRC) (210 +/- 9 vs 159 +/- 9% pred), and total lung capacity (TLC) (138 +/- 6 vs 110 +/- 5% pred). The mean value of MIP increased by 52% from 4.8 +/- 0.4 to 7.3 +/- 0.6 kPa (p < 0.001), the mean value of SNIP increased by 66% from 3.9 +/- 0.4 to 6.5 +/- 0.5 kPa (p < 0.001), and the mean value of Pdi increased by 28% from 6.0 +/- 0.6 to 7.7 +/- 0.8 kPa (p < 0.05) after LVRS. P0.1 decreased on average by 24% from 0.46 +/- 0.03 to 0.35 +/- 0.02 kPa after LVRS. No significant correlations were found between inspiratory muscle (MIP, SNIP, Pdi) and respiratory drive (P0.1) indices, lung function data, 6 min walk distance, or dyspnoea score. In conclusion, the observed clinical improvement of patients with severe emphysema after lung volume reduction surgery results, in part, from an increased ability of the inspiratory muscles to generate force, which is paralleled by a significant decrease in central respiratory drive.

Adult↗
PubMed1988

Pulmonary function of guinea pigs exposed to freshly generated ultrafine zinc oxide with and without spike concentrations.

Exposure of guinea pigs 3 hr/day for 5 consecutive days to freshly formed ultrafine zinc oxide (ZnO) (count median diameter: 0.05 micron; geometric standard deviation: 2.0) at a concentration of 7 mg/m3 produced a gradual decrease in total lung capacity and vital capacity over the course of the exposure period. The carbon monoxide (CO) diffusing capacity (DLCO) was not affected until the fourth day, when it dropped abruptly to 30% below control levels. Wet-lung weight/body weight ratios and wet-lung/dry-lung weight ratios increased, indicating the presence of edema. Exposures to 2.7 mg/m3 ZnO, using the same 3 hr/day, 5 day time frame, did not alter any parameters measured. In 2 experiments a single high peak of ZnO (25-34 mg/m3) occurred. In one experiment exposure was stopped, but pulmonary function measurements were made as scheduled; in the other case, exposures to ZnO were continued. In both, lung volumes were decreased abruptly and to a greater extent than when peaks were absent. Continued exposure caused greater decrements in total lung capacity (TLC) and vital capacity (VC) as well as decrements in functional residual capacity (FRC) and residual volume (RV) than were observed when exposure was stopped. Peak exposures reduced DLCO to 45%-60% below control. These values rose to 25%-30% below control with or without continued exposure. Airway resistance increased and compliance decreased following peak exposures. When exposure was stopped, these changes were reversible; with continued exposure they still were different from control levels on the fifth day.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1991

Extent of pulmonary emphysema in man and its relation to the loss of elastic recoil.

1. We assessed lung density, determined by computerized tomography, as a measure of emphysema and related this to lung function and measurement of the elastic recoil of the lung in normal subjects and patients with chronic obstructive lung disease. 2. We found a significant correlation between measurements of elastic recoil pressure at 90% of total lung capacity and both the forced expiratory volume in 1 s (r = 0.80, P less than 0.001) and the transfer factor for carbon monoxide (r = 0.70, P less than 0.001). Measurements of elastic recoil of the lung also correlated with lung density as measured by computerized tomography scanning (P less than 0.001). 3. Multiple regression analysis demonstrated a correlation between the density of the lowest fifth percentile of the computerized tomography lung-density histogram, and both the natural logarithm of the shape parameter of the pressure-volume curve (P less than 0.01), and the transfer factor for carbon monoxide (P less than 0.01). However, the mean computerized tomography lung density correlated, in addition, with the elastic recoil pressure of the lungs at 90% of total lung capacity (P less than 0.001). 4. Since the elastic recoil pressure correlates with computerized tomography lung density, and hence with emphysema, and since elastic recoil pressure also correlates with the forced expiratory volume in 1 s, these results suggest that loss of elastic recoil is one determinant of airflow limitation in patients with chronic obstructive lung disease.

Adult↗
PubMed1987

Dilatation, compensatory growth, or both after pneumonectomy during childhood and adolescence. A thirty-year follow-up study.

The ventilatory function of 230 patients with pneumonectomy, performed at ages ranging from 2 to 40 years, has been followed for more than 30 years (mean 33 years). We have tried to analyze whether the available data gave information about the nature and the mechanisms adapting the remaining lung to the larger than normal pleural space and about the persistence of this adaptation in the longer term. There were 32 patients with a persistent, disturbed forced expiration (mean 50% of vital capacity). This group of patients was excluded from the study to answer the above questions, because the subdivisions of the total lung capacity in this group differed significantly from those in the group of 98 patients with a normal forced expiratory volume of 72% (mean) of vital capacity. The data of the 98 patients, who were subdivided into seven age groups at the time of pneumonectomy, permitted the following conclusions: In the youngest age group (0 to 5 years), the ventilatory capacity is hardly smaller than the predicted capacity for two lungs; this suggests that compensatory growth by way of hyperplasia might have been the most important adaptive mechanism in this group. In the age group 6 to 20 years, a significant difference is still found as compared to the group of patients operated on at an older age; this difference indicates that in this period compensatory growth, possibly mainly simple hypertrophy, still played an important but gradually decreasing role. The fact that the effect of the adaptational mechanisms could be observed more than 30 years after ablation of one lung, without loss in quality of function (i.e., forced expiratory volume constituting a normal percentage of the vital capacity), indicates that the adaptive mechanisms also compensate for the loss in lung tissue in the longer term. A striking finding was the stability of the tidal volume/functional residual capacity ratio, which, especially in the younger age groups, was very close to the predicted value for two lungs. This finding is in agreement with the fact that most persons with a healthy remaining lung lead a normal family and social life after pneumonectomy.

Adaptation, Physiological↗
PubMed1979

Post-mortem lung volumes.

The volumes of 78 adult human lungs at necropsy after fixation with intrabronchial 10% formaldehyde at a transpulmonary pressure of 25 cm of water (VL) were similar to their total lung capacity (TLC) as assessed radiologically (VX). Corrected for stature, VL and VX did not increase with age in non-emphsematous lungs, nor did the radio of VL to VX (VL/VX) change with age. VL and VX relative to body length increased with emphysema, and the increase even occurred in lungs from men with trivial or equivocal amounts of emphysema. Thus alteration of the mechanical properties of the lung may precede the appearance of obvious emphysema. VL/VX was not affected by the presence or severity of emphysema. The right lung formed 53% of VL with a range of 49-58% in apparently normal lungs. The amount of air in 13 human lungs at necropsy averaged 61% of TLC with a wide variation, indicating that this is not a useful point at which to measure lung dimensions. It is concluded that the volume of lungs fixed with formaldehyde at a transpulmonary pressure of 25 cmH2O closely approximates to total lung capacity.

Adult↗
PubMedDate not supplied

Aerosol measurement of airspace diameter correlates with morphometry in normal and papain-exposed air dried lungs.

Aerosol measures of effective airspace diameter (EAD) were correlated with morphometric parameters in a series of 8 canine lungs, 5 of which had been exposed to papain in order to cause experimental emphysema. In an effort to preserve alveolar dimensions without shrinkage, the lungs were fixed by air drying at total lung capacity. EAD was measured with 400-cm2 boluses, with mean penetration index (Pen), defined as volumetric bolus penetration/total lung capacity, equal to 0.34 (EAD400), and with 800-cm2 aerosol boluses, with mean Pen equal to 0.59 (EADdeep). Morphometric analysis, following measurement of EADs, determined the mean linear intercept and other parameters of the chordlength distribution, including the 90th, 95th, and 99th percentiles (p90, p95, p99), the standard deviation, and the geometric standard deviation (GSD). EAD400 was significantly correlated with Lm (r2 = .68, P < .05), p95, (r2 = .85, P < .01), p99 (r2 = .94, P < .001), and GSD (r2 = .94, P < .001). Similar results were found with EADdeep. In general, correlations were stronger between EAD and p95, p99, or GSD than between EAD and Lm. A comparison with a previous similar study relating EAD to morphometry in a series of lungs fixed by formalin fixation found closer agreement between EAD and morphometry when lungs were fixed by air drying. Overall, the data support the validity of EAD as an in vivo method of determining airspace size at total lung capacity.

Aerosols↗
PubMed2006

Vibration and its effect on the respiratory system.

Vibration is a manual technique used widely to assist with the removal of pulmonary secretions. Little is known about how vibration is applied or its effect on the respiratory system. The purpose of this study was to describe mechanical consequences of vibration on the chest wall of a normal subject and the effects of vibration on expiratory flow rates and volumes. The effects of vibration were compared to other interventions of chest wall compression, chest wall oscillation, cough, huff from high lung volume, inspiration to total lung capacity with relaxed expiration, tidal breathing, and sham. Sixteen physiotherapists applied vibration and other interventions in a randomised order to the chest wall of a healthy adult female subject. The magnitude and direction of the force and the frequency of vibration were measured by an instrumented bed with seven load cells. Inductive plethsysmography measured the change in chest wall circumference with vibration. A heated pneumotachometer measured inspiratory and expiratory flow rates, which were integrated to provide volumes. Vibration was applied with a mean resultant force of 74.4 N (SD 47.1). The mean (SD) change in chest wall circumference and frequency of vibration were 0.8 cm (SD 0.4) and 5.5 Hz (SD 0.8) respectively. The mean peak expiratory flow rate was 0.97 l/s (SD 0.27). Peak expiratory flow rates with vibration were less than 20% of those achieved with cough or huff from high lung volume but greater than with chest wall compression, chest wall oscillation, relaxed expiration from total lung capacity, sham treatment or tidal breathing.

Adult↗
PubMed2006

The value of pulmonary function testing prior to bariatric surgery.

BACKGROUND: Pulmonary function tests (PFTs) are often abnormal in the morbidly obese and improve after bariatric surgery. Our aim was to determine the utility of obtaining preoperative PFTs in assessing postoperative risk. METHODS: 146 consecutive patients undergoing open bariatric surgery were analyzed. Patients were divided into those who had postoperative complications (Group A, n=27) and those who did not (Group B, n=119). PFTs and BMI were compared between Groups A and B. PFT parameters are reported as the median percentage of age-matched controls. RESULTS: Patients in Group A compared to Group B were heavier (BMI 58 vs 51 kg/m(2), P=.001) and older (46 vs 40 years, P=.02) than those in group B. They had reduced forced vital capacity (80% vs 97%, P<.001) and forced expiratory volume in 1 second (84% vs 99%, P=.002). They also had reduced vital capacity (VC, 85% vs 102%, P<.001) and total lung capacity (89% vs 99%, P=.01). They had decreased maximal voluntary ventilation (93% vs 106%, P=.003). They had lower arterial pO(2) (76 mmHg vs 85 mmHg, P=.001) and higher arterial-alveolar gradient (23 vs 17, P=.007). The strongest predictors of postoperative complications on multivariate analysis were reduced VC (RR 2.29 for each 10% decrease in VC, P=.0007) and age (RR 6.4 for age >40 years, P=.01). CONCLUSIONS: PFTs help to predict complications after bariatric surgery. The greatest reduction in VC may occur in patients with central obesity, reflecting increased intrabdominal pressure and diminished chest wall compliance.

Adult↗
PubMed2006

The structural basis of airways hyperresponsiveness in asthma.

We hypothesized that structural airway remodeling contributes to airways hyperresponsiveness (AHR) in asthma. Small, medium, and large airways were analyzed by computed tomography in 21 asthmatic volunteers under baseline conditions (FEV1 = 64% predicted) and after maximum response to albuterol (FEV1 = 76% predicted). The difference in pulmonary function between baseline and albuterol was an estimate of AHR to the baseline smooth muscle tone (BSMT). BSMT caused an increase in residual volume (RV) that was threefold greater than the decrease in forced vital capacity (FVC) because of a simultaneous increase in total lung capacity (TLC). The decrease in FVC with BSMT was the major determinant of the baseline FEV1 (P < 0.0001). The increase in RV correlated inversely with the relaxed luminal diameter of the medium airways (P = 0.009) and directly with the wall thickness of the large airways (P = 0.001). The effect of BSMT on functional residual capacity (FRC) controlled the change in TLC relative to the change in RV. When the FRC increased with RV, TLC increased and FVC was preserved. When the relaxed large airways were critically narrowed, FRC and TLC did not increase and FVC fell. With critical large airways narrowing, the FRC was already elevated from dynamic hyperinflation before BSMT and did not increase further with BSMT. FEV1/FVC in the absence of BSMT correlated directly with large airway luminal diameter and inversely with the fall in FVC with BSMT. These findings suggest that dynamic hyperinflation caused by narrowing of large airways is a major determinant of AHR in asthma.

Adrenergic beta-Agonists↗