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PubMed1991

Abdominal distension alters regional pleural pressures and chest wall mechanics in pigs in vivo.

Abdominal distension (AD) occurs in pregnancy and is also commonly seen in patients with ascites from various causes. Because the abdomen forms part of the "chest wall," the purpose of this study was to clarify the effects of AD on ventilatory mechanics. Airway pressure, four (vertical) regional pleural pressures, and abdominal pressure were measured in five anesthetized, paralyzed, and ventilated upright pigs. The effects of AD on the lung and chest wall were studied by inflating a liquid-filled balloon placed in the abdominal cavity. Respiratory system, chest wall, and lung pressure-volume (PV) relationships were measured on deflation from total lung capacity to residual volume, as well as in the tidal breathing range, before and 15 min after abdominal pressure was raised. Increasing abdominal pressure from 3 to 15 cmH2O decreased total lung capacity and functional residual capacity by approximately 40% and shifted the respiratory system and chest wall PV curves downward and to the right. Much smaller downward shifts in lung deflation curves were seen, with no change in the transdiaphragmatic PV relationship. All regional pleural pressures increased (became less negative) and, in the dependent region, approached 0 cmH2O at functional residual capacity. Tidal compliances of the respiratory system, chest wall, and lung were decreased 43, 42, and 48%, respectively. AD markedly alters respiratory system mechanics primarily by "stiffening" the diaphragm/abdomen part of the chest wall and secondarily by restricting lung expansion, thus shifting the lung PV curve as seen after chest strapping. The less negative pleural pressures in the dependent lung regions suggest that nonuniformities of ventilation could also be accentuated and gas exchange impaired by AD.

Abdomen↗
PubMed1989

Diaphragmatic electromyography using a multiple electrode array.

We have developed a new technique for diaphragmatic electromyography using an array of seven sequential electrode pairs at 1.0-cm spacing on an esophageal catheter. This array provides information about the spatial distribution of the electrical field generated by the diaphragm and reveals a sharply peaked variation of electrical potential with distance along the esophagus. The rectified and integrated information from each of the seven pairs is summed to give an approximation to the total electrical activity over the span of the array, providing a signal that is relatively insensitive to the position of the array over approximately 4 cm of catheter movement and removes the requirement for balloon stabilization of the catheter. With our array, we have confirmed the artifact in the evoked compound muscle action potential that seems to be related to diaphragmatic shape as reported by others who used supramaximal phrenic nerve stimulation, but the magnitude of this artifact (compared with the functional residual capacity level) was modest near functional residual capacity, averaging 12 +/- 14% (SD) for lung volumes 1.0 l above and -4 +/- 15% for lung volumes 1.0 l below functional residual capacity along the rib cage-abdomen relaxation line.

Action Potentials↗
PubMed1997

Comparison of helium dilution and plethysmographic lung volumes in pregnant women.

The multibreath helium equilibration method is the technique recommended for routine measurement of static lung volumes in normal subjects. However, pregnancy could be an exception to this general rule, due to airway closure during the second half of gestation. The aim of this study was to compare the measurements of lung volumes by plethysmography and helium dilution during pregnancy. Twenty three healthy women were studied at 12, 24 and 36 weeks of pregnancy, and 4 months postpartum. Total lung capacity (TLC), functional residual capacity (FRC) and residual volume (RV) were measured by multibreath helium equilibration (TLCHe, FRCHe and RVHe) and by plethysmography (TLCbox, FRCbox and RVbox). Only at 36 weeks were there differences between the two methods. RVbox was significantly larger than RVHe (1.01+/-0.18 vs 0.77+/-0.21 L; p<0.001). FRCbox was larger than FRCHe (1.95+/-0.32 vs 1.60+/-0.32 L; p<0.001) and TLCbox was larger than TLCHe (4.83+/-0.52 vs 4.45+/-0.51 L; p<0.05). The 95% limits of agreement for differences between lung volumes measured by the two techniques (helium dilution - plethysmography) at 36 weeks were: -0.42 to -0.06 L for RV; -0.54 to -0.17 L for FRC; and -0.66 to -0.11 L for TLC. We conclude that using the multibreath helium equilibration method to measure lung volumes in at-term pregnant women results in underestimation of functional residual capacity and total lung capacity.

Adult↗
PubMed1975

Anaesthesia for intestinal short circuiting in the morbidly obese with reference to the pathophysiology of gross obesity.

Sixteen extremely obese patients were anaesthetized for intestinal short circuiting operations. Severe obesity may cause pathological cardio-pulmonary changes. Cardiovascular alterations include increased systemic, pulmonary artery and pulmonary capillary venous pressure. Cardiac output, total blood volume and left ventricular work increase. Expiratory reserve volume and consequently functional residual capacity decrease with gross obesity. Functional residual capacity falls below closing volume and inspired gas may be distributed to non-dependent lung zones, resulting in decreased ventilation/perfusion ratios and arterial hypoxaemia. Low total respiratory compliance increases the oxygen cost of the work of breathing. Obesity may change the dose requirements for regional anaesthesia and long-acting muscle relaxants. General anaesthesia may also reduce functional residual capacity. We used a technique of anaesthesia which consisted of epidural analgesia with intra-operative mechanical ventilation and which specifically avoided volatile inhalation agents and long-acting muscle relaxants. All patients were extubated immediately after operation and returned to the recovery room for an average duration of 26 hours. Post-operative treatment included humidified oxygen, chest physiotherapy and elevation of the head of the bed to 45 degrees. Each patient's respiratory progress was monitored by repeated determinations of arterial blood gases and vital capacity and by serial chest X-rays. None of the patients in this group required post-operative tracheal intubation and mechanical ventilation.

Anesthesia, Epidural↗
PubMed1984

Partial expiratory flow-volume curves in young children.

The purpose of this study was to examine the variability and possible uses of partial maximal expiratory flow-volume curves as a measurement of lung function in young children. Repeated partial flow-volume curves followed by measurement of resting lung volume were obtained from 45 healthy children and 12 with generally mild lung disease caused by cystic fibrosis; the age range was 3 to 6 yr. At each test session, each child completed 3 runs; for each run, values of functional residual capacity, maximal flow at functional residual capacity, and maximal flow compensated for lung size were obtained. Within-subject, day-to-day, and among-subject variabilities in the healthy group were very close to those reported for similar flow rates and lung volume in older subjects who are able to produce a full forced vital capacity. When compensated for lung volume, healthy boys had significantly lower flow rates than did girls. Test sensitivity and specificity were such that the cystic fibrosis and healthy groups were easily discernible. Among-subject variability of flow rates in healthy children was large enough to make the accurate detection of mild airways dysfunction in any given individual difficult.

Child↗
PubMed1984

Functional residual lung capacity in rats affected by a carotid body stimulant.

The respiratory response and changes of functional residual lung capacity were measured in the rat after intravenous administration of the drug S 2620 in a dose of 0.4 mg/kg. This substance induced a significant decrease of arterial PCO2 and an increase of minute ventilation. The stimulating effect of S 2620 was maximal in the 10th min; after 60 min, ventilation and PCO2 approached control levels. The CO2 ventilatory response was determined 10 min after the administration of S 2620. The slope of the control and S 2620 stimulated curves was similar with a shift towards higher ventilation and lower PCO2 after S 2620 administration. Functional capacity rose with increasing minute ventilation. The increase of functional residual capacity disappeared after bilateral cervical vagotomy.

Almitrine↗
PubMed1986

Diaphragmatic contractility after upper abdominal surgery.

Postoperative dysfunction of the diaphragm has been reported after upper abdominal surgery. This study was designed to determine whether an impairment in diaphragmatic contractility was involved in the genesis of the diaphragmatic dysfunction observed after upper abdominal surgery. Five patients undergoing upper abdominal surgery were studied. The following measurements were performed before and 4 h after surgery: vital capacity (VC), functional residual capacity (FRC), and forced expiratory volume in 1 s. Diaphragmatic function was also assessed using the ratio of changes in gastric pressure (delta Pga) over changes in transdiaphragmatic pressure (delta Pdi). Finally contractility of the diaphragm was determined by measuring the change in delta Pdi generated during bilateral electrical stimulation of the phrenic nerves (Pdi stim). Diaphragmatic dysfunction occurred in all the patients after upper abdominal surgery as assessed by a marked decrease in delta Pga/delta Pdi from 0.480 +/- 0.040 to -0.097 +/- 0.152 (P less than 0.01) 4 h after surgery compared with preoperative values. VC also markedly decreased after upper abdominal surgery from 3,900 +/- 630 to 2,060 +/- 520 ml (P less than 0.01) 4 h after surgery. In contrast, no change in FRC and Pdi stim was observed 4 h after surgery. In contrast, no change in FRC and Pdi stim was observed 4 h after upper abdominal surgery compared with the preoperative values. We conclude that contractility of the diaphragm is not altered after upper abdominal surgery, and diaphragmatic dysfunction is secondary to other mechanisms such as possible reflexes arising from the periphery (chest wall and/or peritoneum), which could inhibit the phrenic nerve output.

Abdomen↗
PubMed2005

Lung volumes in healthy Afro-Caribbean children aged 4-17 years.

Lung volumes in healthy children differ according to their ethnic origin. We wished to determine if any differences in the lung volumes of Afro-Caribbean (AC) children from those predicted by Caucasian reference values disappeared if the results were related to sitting height or to 90% or 77% of lung volumes predicted for height from Caucasian reference values based on standing height. We took, as our working hypothesis, that it is inappropriate to use Caucasian reference values to interpret data from Afro-Caribbean children, and that ethnic-specific reference values are required. This was a prospective, observational study. Subjects included 80 AC children with a median age of 9 (range, 4.3-17.8) years. Standing and sitting height were measured. Lung volumes were measured by body plethysmography (total lung capacity, TLC(pleth); functional residual capacity, FRC(pleth); and vital capacity, VC(pleth)), helium gas dilution (functional residual capacity, (FRC(He)), spirometry (forced expiratory volume in 1 sec, FEV(1)), and forced vital capacity (FVC). The lung volumes of AC children correlated significantly with standing height, but differed significantly from values predicted from Caucasian reference values based on standing height (P < 0.05). Significant differences remained for TLC(pleth), FRC(pleth), FRC(He), RV(pleth), VC(pleth), FEV(1), and FVC when the results were related to sitting height or 90% or 77% of values predicted from Caucasian reference values based on height (P < 0.05). Lung volumes in Afro-Caribbean children should be compared to ethnic-specific reference values.

Adolescent↗
PubMed1998

Mechanical advantage of the canine diaphragm.

The mechanical advantage (mu) of a respiratory muscle is defined as the respiratory pressure generated per unit muscle mass and per unit active stress. The value of mu can be obtained by measuring the change in the length of the muscle during inflation of the passive lung and chest wall. We report values of mu for the muscles of the canine diaphragm that were obtained by measuring the lengths of the muscles during a passive quasistatic vital capacity maneuver. Radiopaque markers were attached along six muscle bundles of the costal and two muscle bundles of the crural left hemidiaphragms of four bred-for-research beagle dogs. The three-dimensional locations of the markers were obtained from biplane video-fluoroscopic images taken at four volumes during a passive relaxation maneuver from total lung capacity to functional residual capacity in the prone and supine postures. Muscle lengths were determined as a function of lung volume, and from these data, values of mu were obtained. Values of mu are fairly uniform around the ventral midcostal and crural diaphragm but significantly lower at the dorsal end of the costal diaphragm. The average values of mu are -0.35 +/- 0.18 and -0.27 +/- 0.16 cmH2O. g-1. kg-1. cm-2 in the prone and supine dog, respectively. These values are 1. 5-2 times larger than the largest values of mu of the intercostal muscles in the supine dog. From these data we estimate that during spontaneous breathing the diaphragm contributes approximately 40% of inspiratory pressure in the prone posture and approximately 30% in the supine posture. Passive shortening, and hence mu, in the upper one-third of inspiratory capacity is less than one-half of that at lower lung volume. The lower mu is attributed primarily to a lower abdominal compliance at high lung volume.

Animals↗
PubMed1986

Measurement of cardiopulmonary function in ventilated neonates with respiratory distress syndrome using rebreathing methodology.

The feasibility of using a multiple gas rebreathing technique to evaluate cardiopulmonary function in the ventilated neonate was assessed by measuring functional residual capacity, diffusing capacity of lung for carbon monoxide, and effective pulmonary capillary blood flow in 10 neonates with respiratory distress syndrome. Measurements were first made on the level of positive end expiratory pressure (PEEP) selected by the clinicians caring for the infants ("clinical" PEEP, mean of 4.4 +/- 0.3 cm H2O). To evaluate the effect of PEEP on cardiopulmonary function, PEEP was then changed above (mean of 6.7 +/- 0.4 cm H2O) and below (mean of 1.9 +/- 0.3 cm H2O) this level and measurements were repeated. Mean functional residual capacity on clinical PEEP (10.8 +/- 1.6 ml/kg) was far below the predicted normal and varied directly with changes in PEEP (mean change of 1.2 ml/kg/cm H2O). Diffusing capacity of the lung for carbon monoxide on clinical PEEP was 0.04 +/- 0.01 ml/min/mm Hg/kg and did not change significantly with changes in PEEP. Mean effective pulmonary capillary blood flow was highest (70 ml/min/kg) at the lowest level of PEEP. However, the effect of increasing PEEP on effective pulmonary capillary blood flow in individual infants varied. Increasing PEEP increased arterial oxygen tension but did not cause changes in systemic arterial pressure or heart rate. We conclude that infants with respiratory distress syndrome have severe lung injury with decreased functional residual capacity and diffusing capacity of the lung for carbon monoxide, and that lung volume improves with the use of PEEP.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Monoxide↗
PubMed1977

Evaluation of the risk of postoperative pulmonary complications.

Ten of 40 patients who underwent major thoracic or abdominal operations developed postoperative pulmonary complications, consisting of six massive atelectasis, three pneumonias and one edema. They were mostly thoracotomy cases and cigarette smokers. Many of these complications would have been prevented, if reliable pulmonary function tests are available to predict preoperatively such occurrence. Flow-volume curve tracing and closing volume measurement were evaluated in this respect. Both flow at the point of functional residual capacity on flow-volume curve, and the closing capacity subtracted from functional residual capacity were found to be well correlated with the occurrence of postoperative complications and can be used to evaluate the risk of pulmonary complications developing in postoperative period.

Abdomen↗
PubMed1979

Determination of bronchodilation in the clinical pulmonary function laboratory. Role of changes in static lung volumes.

Improved airway resistance following bronchodilator inhalation is not always accompanied by improvement in forced expiratory flow. We studied 241 patients with airways obstruction to learn whether changes in static lung volumes (vital capacity and function residual capacity measured by body plethysmography [FRCB]) would reveal bronchodilation not demonstrated by expiratory flow rates (the ratio of forced vital capacity at one second to the total forced vital capacity [FEV1/FVC]), and the forced expiratory flow for the midportion of the forced vital capacity (FEF25--75%). A significant fall in Raw occurred in 129 patients, 46 of whom had a significant increase in vital capacity (mean of + 465 ml +/- 43, P less than 0.001) and a fall in FRCB (mean of -763 ml +/- 78 P less than 0.001) with no change in FEV1/FVC% of FEF25--75%. We interpret these data to indicate that improvement in static lung volumes can reflect bronchodilation in the absence of improved expiratory flow.

Adult↗
PubMed2026

Impact of neoprene wetsuits on lung volumes and work of breathing: implications for military diver safety and performance.

INTRODUCTION: Neoprene wetsuits may impose mechanical constraints on the chest wall, potentially altering respiratory function. This study investigated the impact of neoprene wetsuits on lung volumes, airway mechanics, and work of breathing (WOB) in healthy male divers. METHODS: A randomised crossover trial was conducted with 31 male divers at the Royal Netherlands Navy Diving Medical Centre. Participants underwent pulmonary function testing, including spirometry, body plethysmography, the forced oscillation technique (FOT), and diffusion capacity measurements, both with and without a hoodless standardised 5 mm neoprene full body wetsuit with a neoprene neck seal. Primary outcomes included changes in forced vital capacity (FVC), functional residual capacity (FRC), airway resistance (Raw), reactance (Xrs), and WOB. RESULTS: Wearing a neoprene wetsuit led to statistically significant reductions in FVC (2.8%, P < 0.05), forced expiration in one second (2.9%, P < 0.05), FRC (4.0%, P < 0.05), and expiratory reserve volume (10.9%, P < 0.05), alongside increases in inspiratory capacity and tidal volume. Raw increased significantly (P < 0.05), while the FOT revealed altered airway mechanics, evidenced by increased Xrs at multiple frequencies (P < 0.05). Diffusion capacity remained unchanged, suggesting preserved alveolar-capillary function. CONCLUSIONS: Neoprene wetsuits induce mechanically restrictive effects on the chest wall, reducing static and dynamic lung volumes and increasing WOB. While these changes may not be clinically relevant at rest, their impact needs to be determined during strenuous or prolonged dives, particularly when combined with other equipment that limits thorax excursions. Future research should explore the effects of the military 5 mm wetsuit under immersed conditions to better understand their operational impact on diver performance and safety.

Male↗
PubMed1977

Pulmonary mechanics in fibrosing alveolitis: the effects of lung shrinkage.

Pulmonary and airway mechanics were studied in 8 patients with severe fibrosing alveolitis. In this disease, the number of functioning alveoli is probably considerably decreased, but static compliance was low even when related to the decreased lung volume. Lung recoil pressures toward full inflation were high but were not increased at and below functional residual capacity. Airway function was broadly normal for lung recoil pressure but supernormal for absolute lung volume. Analysis of model pressure-volume and maximal flow-volume curves showed that (1) these features could be produced simply by replacement of some units by indistensible fibrous tissue and retention of normal function of the surviving alveoli, respiratory muscles, chest wall, and airways; (2) increased lung tissue volume may prevent an increase in lung recoil pressures in the lower part of the vital capacity; and (3) the decreased lung volume could result in a decrease in upstream conductance without structural change in the airways. Measurement of lung compliance, even when corrected for the decreased lung volumes, may not distinguish between loss of units (lung "shrinkage") and abnormal distensibility of the functioning alveoli, but the latter is likely if maximal expiratory flow is excessive in relation to the lung volume expressed as per cent vital capacity.

Adult↗
PubMed1998

[Lung volumes in non-smoking healthy men in Maracaibo, Venezuela].

The significant applicability of the tests to measure lung volumes makes it necessary to handle them frequently and this implies the comparison of the registered values for lung function parameters with predicted or referential values which are obtained via derivate equations of healthy population studies. The Slow Vital Capacity (SVC), Inspiratory Capacity (IC), Functional Residual Capacity (FRC), Residual Volume (RV), Total Lung Capacity (TLC) and the physical characteristics, were measured in 50 healthy men, non smokers, with ages between 17 and 63 years, in order to deduce++ prediction equations. The functional tests were performed by means of the multiple respiratory technique and Helium Dilution, using a Spinnaker TL Lung Functions Analyzer. Stepwise multiple regression analyses were used to derive equations for predicting lung volumes, that allowed the inclusion of the variables that add prediction with statistical significance (95% of confidence), and obtaining for SVC: R = 0.853, SEE = 0.350 lts; IC: R = 0.822, SEE = 0.296 lts; FRC: R = 0.843, SEE = 0.326 lts; RV: R = 0.891, SEE = 0.153 lts y TLC: R = 0.883, SEE = 0.458 lts. The analysis of variance (ANOVA) was highly significant (p < 0.00001) for each one of the models of regression of the estimated parameters. The fifth percentile was considered as the lower limit of the established volume as the normal value. The calculation of fifth percentiles determined were SVC = 3.59 lts, IC = 2.47 lts, FRC = 2.14 lts, RV = 1.26 lts, and TLC = 4.88 lts. Those values can represent the levels under which the test are considered as reduced. Values which are equal o greater can be considered as "normal" for each one of the parameters studied. The equations of prediction for the SVC, IC, FRC, RV and TLC can be utilized with validity and high confidence to calculate reference static lung volumes in our population (p < 0.00001).

Adolescent↗
PubMed2001

Respiratory muscle strength, lung function, and dyspnea in patients with sarcoidosis.

BACKGROUND: Sarcoidosis is a systemic granulomatous disorder that is estimated to involve the skeletal muscles in up to 50% of patients. There is little information on the relationship among respiratory muscle strength, lung volumes, and the degree of dyspnea in patients with sarcoidosis. DESIGN AND PATIENTS: Lung function and maximal respiratory muscle force generation were measured in 36 patients with sarcoidosis (24 patients with pulmonary parenchymal infiltration) and 25 control subjects free of cardiorespiratory disease. Dyspnea in the sarcoidosis patients was quantitated by a score based on an activity tolerance assessment scale (ranging from rest to climbing hills or stairs). SETTING: Outpatient clinics of two teaching hospitals. RESULTS: Mean FVC, maximal voluntary ventilation, total lung capacity (TLC), functional residual capacity, residual volume (RV), and diffusing capacity of the lung for carbon monoxide (DLCO) were all at least 16% less than corresponding control values (in all cases, p < 0.001), while maximal inspiratory mouth pressure (PImax) and maximal expiratory mouth pressure (PEmax) were 37% and 39% less, respectively, than control values (both at p < 0.0001). PImax and PEmax declined with increasing dyspnea in a more graded, steady manner than did spirometric and DLCO values. For all measurements, however, the lowest mean values were found in patients with the most severe level of dyspnea. Strong inverse relationships were observed between PEmax and PImax with dyspnea level (p < 0.0001 and p < 0.01, respectively). Both PImax and PEmax correlated best with absolute values of FVC, while only PEmax correlated with RV (absolute and percent predicted) and percent predicted values of TLC. CONCLUSIONS: Maximal respiratory pressures correlate more closely with dyspnea level than lung volumes and DLCO. Since dyspnea is the most common presentation in early to moderately advanced sarcoidosis, respiratory pressures may be a more reliable index of functional work capacity and reflection of activities of daily living than standard tests of lung function.

Adult↗
PubMed1984

Effect of postoperative intermittent positive pressure breathing on lung function.

Thirty patients undergoing elective cholecystectomy were randomly assigned to two groups. Fifteen patients received postoperative intermittent positive pressure breathing (IPPB) for four days together with physiotherapy while the other 15 had the same postoperative care but without IPPB. Vital capacity (VC), functional residual capacity (FRC) and PO2 were measured preoperatively and on days 0, 1, 3, and 5 postoperatively. The incidence of postoperative pulmonary complications utilizing chest x-ray films, sputum analysis, temperature, and clinical assessment was determined. Both groups had significant deterioration in pulmonary function but did not differ except for a greater depression in VC in the IPPB group (p less than .05). In patients receiving postoperative physiotherapy, the addition of IPPB did not usually result in improved pulmonary function.

Adult↗