Percentage Of Total Lung Capacity Research Articles

Lung and physical function in post COVID-19 and clinical and functional associations: a cross-sectional study in Brazil

The purpose of this study was to assess exercise capacity, lung and physical function in COVID-19 survivors, and the association of lesion-level characteristics assessed by chest computed tomography, probable sarcopenia, and percentage of diffusing capacity of the lung for carbon monoxide with clinical and functional variables. This study was conducted in Salvador, Bahia, Brazil. All patients had a laboratory-confirmed SARS-CoV-2 infection. The sociodemographic characteristics, COVID-19 exposure history, pulmonary function, computed tomography, and functionality of the participants between 1 and 3 months of diagnosis of the disease were collected. A total of 135 patients after COVID-19 recovery were included in this study. Probable sarcopenia, reduction in percentage of diffusing capacity of the lung for carbon monoxide, and a lower 6-min walk distance were observed after COVID-19 infection. Computed tomography>50% was associated with a longer length of stay and a lower percentage of diffusing capacity of the lung for carbon monoxide. Probable sarcopenia diagnosis was associated with a worse percentage of the predicted 6-min walk distance in relation to the predicted, absolute 6-min walk distance (m), percentage of diffusing capacity of the lung for carbon monoxide, and percentage of total lung capacity. Muscle disability and lung dysfunction are common in COVID-19 survivors. Hospitalization was associated with the worst muscle force and diffusing capacity of the lung for carbon monoxide. Computed tomography characteristics could be a marker of prolonged hospital stay after the acute phase of COVID-19. Additionally, the probable diagnosis of sarcopenia could be a marker of impact on walking distance. These results highlight the need for long-term follow-up of those patients and rehabilitation programs.

The effect of quantifying pulmonary contusion extent on the treatment management of blunt chest trauma in children

Objective: Post-traumatic pulmonary contusion in children is often asymptomatic at diagnosis and has a good prognosis. The aim of this study was to investigate the clinical significance of the extent of post-traumatic pulmonary contusions and evaluate the timing of complications to determine the safe follow-up period in children with lung contusions. Methods: The study included pediatric patients who presented to the emergency department after blunt chest trauma and had pulmonary contusion detected on chest computed tomography (CT) between January 2017 and January 2020. Based on the percentage of total lung capacity occupied on thorax CT, pulmonary contusions were classified as grade 1: <19% (mild), grade 2: 19%-27% (moderate) and grade 3: ≥28% (severe). The relationship between pulmonary contusion grade and pulmonary functional status; complications and intensive care admission was examined and the mean time to complication development was determined. Results: The mean extent of pulmonary contusion after trauma was 17.8±8.6% (min-max, 5-100%) and mild (grade 1) contusion was significantly associated with spontaneous breathing (p=0.009). Contusion grade was not associated with the development of atelectasis, pneumonia, pleural effusion, pneumothorax (p=0.719) or intensive care admission (p=0.176). The mean time to detection of complications (atelectasis, pneumonia, pleural effusion, pneumothorax) on chest X-ray was 6.33±3.78 days (range, 2-9 days). Conclusion: The results suggest that although no statistically significance between the extent of pulmonary contusion and complications, patients should be hospitalized for at least 48 hours, then followed-up with chest X-ray for 1 week due to possible complications after blunt chest trauma in children.

Normative Cardiopulmonary Exercise Test Responses at the Ventilatory Threshold in Canadian Adults 40 to 80 Years of Age

Physiologic and symptom responses at the ventilatory threshold (Tvent) during incremental cardiopulmonary exercise testing (CPET) can provide important prognostic information. This study aimed to develop an updated normative reference set for physiologic and symptom responses at Tvent during cycle CPET (primary aim) and to evaluate previously recommended reference equations from a 1985 study for predicting Tvent responses (secondary aim). Participants were adults 40 to 80 years of age who were free of clinically relevant disease from the Canadian Cohort Obstructive Lung Disease. Rate of oxygen consumption (V˙O2) at Tvent was identified by two independent raters; physiologic and symptom responses corresponding to V˙O2 at Tvent were identified by linear interpolation. Reference ranges (5th-95th percentiles) for responses at Tvent were calculated according to participant sex and age for 29 and eight variables, respectively. Prediction models were developed for nine variables (oxygen pulse, V˙O2, rate of CO2 production, minute ventilation, tidal volume, inspiratory capacity, end-inspiratory lung volume [in liters and as percentage of total lung capacity], and end-expiratory lung volume) using quantile regression, estimating the 5th (lower limit of normal), 50th (normal), and 95th (upper limit of normal) percentiles based on readily available participant characteristics. The two one-sided test of equivalence for paired samples evaluated the measured and 1985-predicted V˙O2 at Tvent for equivalence. Reference ranges and equations were developed based on 96 participants (49%men) with a mean ± SD age of 63 ± 9 years. Mean V˙O2 at Tvent was 50%of measured V˙O2 peak; the normal range was 33%to 66%. The 1985 reference equations overpredicted V˙O2 at Tvent: mean difference in men, -0.17 L/min (95%CI, -0.25 to -0.09 L/min); mean difference in women, -0.19 L/min (95%CI, -0.27 to -0.12 L/min). A contemporary reference set of CPET responses at Tvent from Canadian adults 40 to 80 years of age is presented that differs from the previously recommended and often used reference set from1985. ClinicalTrials.gov; No.: NCT00920348; URL: www.clinicaltrials.gov.

Inhaled granulocyte-macrophage colony stimulating factor for mild-to-moderate autoimmune pulmonary alveolar proteinosis - a six month phase II randomized study with 24\u2009months of follow-up

BackgroundTreatment of autoimmune pulmonary alveolar proteinosis (aPAP) by inhaled granulocyte-macrophage colony stimulating factor (GM-CSF) is considered safe and effective. Evidence of benefit from GM-CSG inhalation for mild to moderate aPAP patients is limited.MethodsIn this multicenter, randomized, open-labeled clinical trial, 36 aPAP patients with mild to moderate disease severity were randomized into either the GM-CSF treatment group or control group. Inhaled GM-CSF was prescribed for 6 months, and patients received follow-up for another 18 months without treatment. Physiological features of the patients were analyzed.ResultsThere were 36 patients (19 in the treatment group, 17 in the control group) included. There were no significant differences in the primary endpoints as measured by the change of alveolar arterial oxygen gradient (A-aDO2) from the baseline values to the values obtained during treatment or during the following 18-month non-treatment observation period [control group vs. treatment group: 0.51 ± 12.09 mmHg vs. -0.35 ± 13.76 mmHg, p = 0.848 (3 month); 1.85 ± 11.21 mmHg vs. 7.31 ± 8.81 mmHg, p = 0.146 (6 months); 6.05 ± 11.14 mmHg vs. 6.61 ± 10.64 mmHg, p = 0.899 (24 months)]). Percentage of diffusion capacity predicted (DLCO%) and percentage of total lung capacity predicted (TLC%), however, were significantly improved in the treatment group by the end of the study (P = 0.010 and 0.027). St. George Respiratory questionnaire (SGRQ) scores were better after 6 months treatment with GM-CSF compared to the control group, and the benefits of treatment were maintained throughout the observation period. No severe side effects were observed during the study.ConclusionSix months of inhaled GM-CSF treatment had no effect on the alveolar–arterial oxygen gradient in patients with mild to moderate pulmonary alveolar proteinosis. There were changes in some clinical or laboratory measures, but no clinically important changes were noted at the end of study. (Clinical Trial Registry: NCT02243228, Registered on September 17, 2014, https://www.clinicaltrials.gov/ct2/show/NCT02243228?term=NCT02243228&draw=2&rank=1)

The Mozart study: a relation between dynamic hyperinflation and physical activity in patients with chronic obstructive pulmonary disease?

Many patients with chronic obstructive pulmonary disease (COPD) experience dyspnoea during exercise, resulting in a reduction of physical activity (PA). Dynamic hyperinflation (DH) is seen as a major cause of dyspnoea in COPD. The objective of the current study was to investigate the relationship between DH, in terms of the amount of DH and the development and recovery rate of DH in patients with COPD, and PA. Thirty-five patients with stable COPD were included from an outpatient clinic (14 GOLD II and 21 GOLD III, median age 65). PA was assessed using an accelerometer. Subjects underwent metronome-paced tachypnoea (MPT) to induce DH. To quantify the amount of DH during MPT, a decrease in inspiratory capacity (IC) or a change in IC as percentage of total lung capacity was used. No significant correlations were found between the parameters describing DH and PA. Secondary correlation analyses showed a negative correlation between static hyperinflation (SH) and PA (r=-0·39; P=0·02). The pattern of breathing during MPT and the test itself showed high interpatient variability. The absence of a significant correlation between DH and PA is contrary to previous studies. SH did show a correlation with PA. The variety in results and the technical difficulties in execution of the measurements ask for a new, more reliable, method to detect DH and investigate its relation with PA in patients with COPD.

Risk factors for osteoporosis in Caucasian patients with moderate chronic obstructive pulmonary disease: A case control study

The prevalence of osteoporosis is high in chronic obstructive pulmonary disease (COPD) patients. The gold standard for the diagnosis of osteoporosis is bone mineral density (BMD) measurements as assessed by dual energy absorptiometry (DXA) scanning as well as vertebral fractures as assessed by instant vertebral assessment (IVA). The aim of this study was to compare COPD GOLD II patients (that is, patients with moderate COPD, stage II, according to the GOLD classification) with osteoporosis (cases) to COPD GOLD II patients without osteoporosis (controls) to identify risk factors for osteoporosis.The diagnosis of osteoporosis was based on BMD and vertebral fractures. Cases (n=49) were matched for gender, age and forced expiratory volume in the first second to controls (n=49). We assessed pulmonary function, body composition, vitamin D, emphysema score (by high-resolution computer tomography), medical history and medication use in all patients. Variables that were significantly different between the cases and controls were included in a logistic regression analysis.COPD patients with osteoporosis had a significantly lower body mass index (BMI) and higher residual volume as the percentage of total lung capacity (RV%TLC) compared to COPD patients without osteoporosis. Decreasing BMI and increasing RV%TLC increased the odds ratio for osteoporosis. Overweight and obese BMI values were protective for osteoporosis.Screening for osteoporosis should be performed even in moderate COPD patients, especially in those with a low BMI and/or a high RV%TLC.

The effects of respiratory training on pulmonary function in patients with chronic obstructive pulmonary disease

Objective To observe the effects of respiratory training on pulmonary function in the patients with chronic obstructive pulmonary disease(COPD). Methods A total of 74 patients with COPD were recruited and randomly divided into a treatment group and a control group with 37 subjects in each.The treatment group re-ceived respiratory training including lip-contracting breathing,abdominal breathing and breathing exercises for 6 months in addition to routine medical treatment.The control group received only routine medical treatment.Pulmona-ry function was evaluated before and after treatment. Results After treatment,both groups improved in terms of all the pulmonary function measures,showing increased vital capacity(VC),forced expiratory volume after 1 s(FEVl),peak forced expiratory flow rate(PEFR),as well as forced expiratory flow at 25%of Vcmax(V25),de-creased residual volume and residual volume as a percentage of total lung capacity(RV/TCL).The difference be-tween the two groups was significant with regard to the extent of improvement. Conclusion Respiratory training can improve the pulmonary function of COPD patients. Key words: Chronic obstructive pulmonary disease; Respiratory training; Pulmonary function

Effects of Imposed Pursed-Lips Breathing on Respiratory Mechanics and Dyspnea at Rest and During Exercise in COPD

To investigate the effect of volitional pursed-lips breathing (PLB) on breathing pattern, respiratory mechanics, operational lung volumes, and dyspnea in patients with COPD. Eight COPD patients (6 male and 2 female) with a mean (+/-SD) age of 58 +/- 11 years and a mean FEV1 of 1.34 +/- 0.44 L (50 +/- 21% predicted). Wearing a tight-fitting transparent facemask, patients breathed for 8 min each, with and without PLB at rest and during constant-work-rate bicycle exercise (60% of maximum). PLB promoted a slower and deeper breathing pattern both at rest and during exercise. Whereas patients had no dyspnea with or without PLB at rest, during exercise dyspnea was variably affected by PLB across patients. Changes in the individual dyspnea scores with PLB during exercise were significantly correlated with changes in the end-expiratory lung volume (EELV) values estimated from inspiratory capacity maneuvers (as a percentage of total lung capacity; r2 = 0.82, p = 0.002) and with changes in the mean inspiratory ratio of pleural pressure to the maximal static inspiratory pressure-generating capacity (PcapI) [r2 = 0.84; p = 0.001], measured using an esophageal balloon, where PcapI was determined over the range of inspiratory lung volumes and adjusted for flow. PLB can have a variable effect on dyspnea when performed volitionally during exercise by patients with COPD. The effect of PLB on dyspnea is related to the combined change that it promotes in the tidal volume and EELV and their impact on the available capacity of the respiratory muscles to meet the demands placed on them in terms of pressure generation.

Detection of Peripheral Ventilation Inhomogeneity in Smokers

BACKGROUND: In smokers, ‘small airways’ narrowing alters the conventional, vital capacity single breath washout (SBWVC). Although, in some studies, the test predicts smokers at risk of developing chronic airflow limitation, its wide variability partly explains its poor positive predictive value. An alternative explanation for the test’s poor predictive value is that it may not accurately reflect small airway narrowing in the lung periphery.OBJECTIVE: To determine whether smoke-induced increases in ventilation inhomogeneity differ between SBWVCmanoeuvres, which augment topographical (apex-to-base) ventilation inhomogeneity, and submaximal manoeuvres (SBWSM), which enhance peripheral ventilation inhomogeneity.STUDY GROUP AND DESIGN: Cross-sectional study of 21 current smokers and 21 nonsmokers with similar age and forced expiratory volumes in 1 s (FEV1).METHODS: Smokers and nonsmokers performed SBW with either slow vital capacity inhalation and exhalation of test gas without breath holding (SBWVC); or slow inhalation of test gas from functional residual capacity to one-half inspiratory capacity and, after 0 s or 10 s of breath holding, slow exhalation to residual volume (SBWSM). For all SBW the normalized phase III helium slope (Sn), closing capacity (CC) as a percentage of total lung capacity (TLC) and mixing efficiency (Emix) were measured.RESULTS: For SBWVC, smoking had no effect on Snor Emix. However, CC/TLC was increased in smokers (P&lt;0.05), but did not correlate with pack years or age. For SBWSM, smoking had no effect on Emixor CC/TLC, but resulted in a steeper Sn(P &lt;0.05), which decreased more with breath holding (P&lt;0.01) and correlated with pack years (P&lt;0.05) at 0 s but not 10 s of breath holding.CONCLUSIONS: In smokers with normal FEV1, SBWSM manoeuvres reveal increases in breath hold time-dependent ventilation inhomogeneity in the lung periphery, not detected by conventional SBWVC.

Pressure-volume relations of the respiratory system in healthy children.

Static pressure-volume (P-V) curves of the respiratory system were obtained in 48 healthy children (1 mo to 16 yr of age) during anesthesia and muscle paralysis. The lungs were inflated to a pressure of 25 to 40 cm H2O, and during the subsequent deflation an interrupter placed in the airway tubing opened and closed every 0.16 s. Airway flow was integrated to obtain the volume decrement between consecutive flow interruptions. Airway pressure was measured during interruptions, and a curve relating pressure to lung volume was plotted, assuming the lung volume at zero pressure to equal functional residual capacity (FRC). FRC was measured using tracer gas washout. The maximum slope of the P-V curve (maximum compliance = Crsmax, ml/cm H2O) was closely related to length (in centimeters) of the child: Crsmax = 7.7 x 10(-4) x length2.38; r = 0.97. The pressure coinciding with Crsmax was 6 +/- 1 cm H2O (mean +/- SD) in infants (1 to 6 mo of age) and 12 +/- 1 cm H2O in older children (> 1.5 yr of age). Total lung capacity (TLC) per kg body weight increased with age and was 52 +/- 13 ml/kg in infants and 87 +/- 11 mg/kg in older children. The FRC/TLC ratio was greater in infants (38 +/- 4%) than in older children (30 +/- 5%). The lung volume coinciding with Crsmax was nearly the same at all ages, when expressed as a percentage of TLC: 62 +/- 3%. Specific compliance of the respiratory system, that is, Crsmax/TLC, decreased with growth and was 0.044 +/- 0.006 cm H2O-1 in infants and 0.035 +/- 0.004 cm H2O-1 in older children. It is concluded that although the P-V relations of the respiratory system changed markedly with growth, especially during the first year of life, the lung volume (%TLC) at which maximum compliance occurred varied little.

Growth of lung and thorax dimensions during the pubertal growth spurt

In the follow-up study of adolescents residual volume (RV), vital capacity (VC), closing volume (CV), thorax height and thorax width were measured at six month intervals over a six year period; 149 girls and 477 boys, whose ages ranged between 11.5 and 18.5 yr during the follow-up, were investigated. In healthy subjects and in those with respiratory symptoms the rates of change of thoracic dimensions, as calculated by a robust linear regression technique, were moderately well correlated; the growth rates of RV and VC were only slightly correlated, and both were moderately well correlated with changes in thorax dimensions. Thorax height increased relative to thorax width in boys and girls during the follow-up. In boys, thorax height continued to grow, when standing height and thorax width had attained adult values in girls. Thus the thorax attains a more elongated shape. During the adolescent growth spurt the residual volume as a percentage of total lung capacity (RV%TLC) within subjects increased on average 0.6% per yr, and closing volume as a percentage of vital capacity (CV%VC) decreased on average 0.5% per yr. Both of these changes can be accounted for by decreased thorax compliance and increased outward chest recoil at low lung volumes.

Moderately severe chronic airflow obstruction. Can corticosteroids slow down obstruction?

In a former study in patients with severe chronic airflow obstruction (CAO), (forced expiratory volume in one second (FEV1) ranging from 350-910 ml), we concluded that daily oral corticosteroids might slow down the progression of disease. The results of the present long-term (14-20 yr) study on 139 non-allergic patients with less severe CAO (FEV1 greater than or equal to 1200 ml, FEV1 as a percentage of vital capacity (FEV1%VC) 40-55%) confirm and extend our former observations. Four patterns of the course of FEV1 and inspiratory vital capacity (VC) in time were recognized: 1) linear decrease; 2) no change; 3) initial increase, followed by decrease; 4) initial decrease, followed by increase. Groups 1 and 3 had a higher functional residual capacity as a percentage of total lung capacity (FRC%TLC) as compared to group 2 and 4; the work of breathing was lower in group 2 than in the other three groups. Otherwise the initial 82 parameters, including the degree of reversibility of airflow obstruction and smoking habits were comparable in the four groups. The four patterns of FEV1 showed a strong association with the long-term use of prednisolone. When oral prednisolone was instituted or increased to a dose of at least 10 mg/day continuously, FEV1 either remained constant, decreased more slowly or even increased over many years of follow-up. When the oral dose was diminished to below 10 mg/day, FEV1 decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Lung diseases after bone marrow transplantation. Results of a clinical, radiological, histological, immunological and lung function study.

SummaryThe case histories of 72 subsequently treated patients — 44 with acute leukemia, 10 with chronic myeloid leukemia, 16 with severe aplastic anemia and 2 with neuroblastoma — were analyzed after bone marrow transplantation (BMT) with respect to pulmonary diseases. Thirty-eight patients suffered from a total of 51 pulmonary complications, which led to death in 20. Of 13 patients, 3 died of bacterial pneumonia, all of them during granulocytopenia; 2 of 6 patients died of fungal pneumonia and 2 out of 3 of a mixed bacterialmycotic infection. Adult respiratory distress syndrome (ARDS) led to death in 2 patients. A granulocyte count under 500/µl correlated significantly (P<0.002) with the fatal outcome of bacterial, fungal and ARDS pneumonia as well as with bronchitis. Viral pneumonia led to death in 8 of 9 patients; in each there was a significant correlation (P<0.05) with graft-versus-host disease (GvHD). Patients with repeated episodes of pulmonary illness had significantly more chronic GvHD (P<0.05); several of these patients displayed a reduction in helper T cells and an increase in suppressor T cells in the peripheral blood. The natural killer (NK) cells were reduced and the percentage of activated NK cell level lay between 6% and 69%. B-cells were absent or deficient. These findings explain in part the absence of specific antibody reactivity. Five of these patients also contracted GvHD-associated obstructive bronchiolitis, which did not respond to therapy. Pulmonary infiltrates of unknown origin (including idiopathic interstitial pneumonia) occurred in 8 of the patients (11.1%), with a fatal outcome in 3 patients. Significant changes (P<0.05) in lung function after BMT appeared in the form of reduced vital capacity (VC) increased residual volume (RV) and an increase in RV expressed as the percentage of total lung capacity. Pulmonary diseases were the most common complication and cause of death in our patients after BMT.

Trapped gas and airflow limitation in children with cystic fibrosis and asthma.

Trapped gas (TG) has been shown to be present in cystic fibrosis (CF) and asthma, but its relationship with airflow limitation (AL) has not been explored. TG was defined as the difference between the functional residual capacity measured by body plethysmography [FRC(BP)] and that measured by helium dilution [FRC(He)] expressed as a percentage of total lung capacity (TLC). We studied 21 children with CF and 15 with asthma who had a similar degree of AL and hyperinflation, however the children with CF had greater amounts of TG compared with asthma [15% +/- 2 (mean +/- 1 SE) vs 8 +/- 2, P less than 0.05]. Mixing efficiency (ME), an index of the distribution of ventilation, was found to be lower in the CF children than in those with asthma (34 +/- 4 vs 54 +/- 4). In CF, TG correlated with forced expiratory flow between 25 and 75% of vital capacity (FEF25-75), ME, RV/TLC, and maximal expiratory flow rates at 25 and 50% of vital capacity (Vmax25 and 50, respectively; r = -0.66, -0.61, 0.72, -0.71, -0.74). ME also correlated with the above measures. In asthma, TG did not correlate with the FEF25-75, ME, RV/TLC, Vmax25, or Vmax50. Furthermore, TG was frequently found in patients with asthma with moderate AL while it was often absent in patients with severe AL. For both CF and asthma, neither the severity of AL nor the magnitude of the TG could be predicted from the increase in Vmax50 with helium (delta V50).(ABSTRACT TRUNCATED AT 250 WORDS)

Prognosis in severe chronic obstructive pulmonary disease with regard to the electrocardiogram

A long-term prognostic study of 128 patients with severe chronic obstructive pulmonary disease (initial value for Forced Expiratory Volume in one second, [FEV1] less than or equal to 1,000 ml) with regard to electrocardiographic and lung function parameters as obtained at the entry visit is reported. Many initial ECG-variables and lung function parameters were significantly different between survivors and non-survivors after five years. We used a discriminant analysis to determine which factors actually provided independent information for detection of those subjects with a survival less than five years. In a discriminant analysis of the initial 25 ECG-variables only P-amplitude in lead II and S-amplitude in lead V6 were predictors of five-year survival (diagnostic accuracy 66.1%). In a discriminant analysis in which initial lung function variables were also considered next to the ECG-variables, the best prediction of five-year survival was made by P-amplitude in lead II, increase of FEV1 after thiazinamium i.m., and residual volume as percentage of total lung capacity [RV/TLC, %] (diagnostic accuracy 73.2%).

Lung function data on 123 persons followed up for 20 years after total pneumonectomy.

Consecutive spirographic data of 123 pneumonectomized patients obtained before pneumonectomy, at discharge from hospital, in 1955 (CU1) and in 1975 (CU2) are presented. The mean observation time was of more than 20 years. The loss in inspiratory vital capacity (VC) proved considerably smaller than predicted from transversal studies. It was most pronounced in patients with thoracoplasties and in persons with left remaining lungs. The FEV1 as a percentage of total lung capacity (FEV1%TLC) evidently obviated the qualitative pulmonary function loss over the years. At the same time, data from 25 of 33 patients who died between CU1 and CU2 are reported (mean survival time 15.1 years). The survival rate of the initial group of 168 persons at CU1 was 14% below that of a control group of the same population. Life expectancy in pneumonectomized patients proved to depend more on the quantity of the lung parenchyma available, i.e. the actual inspiratory VC than on the quality as judged from the FEV1 in relation to lung volume.

Effects of hexoprenaline on the lecithin/sphingomyelin ratio and pressure-volume relationships in fetal rabbits

A placebo-controlled, double-blind trial was carried out on 74 New Zealand White rabbit fetuses from 15 does to assess the effect of a fetal injection of hexoprenaline on surfactant release. After the uterus was exposed, half the fetuses received 0.1 ml (0.25 μg) of hexoprenaline injected intraperitoneally through the intact uterine wall; the other half received an equivalent volume of placebo. After 3 hours, the abdomen was reopened, and the fetuses were surgically delivered and killed before breathing. The lecithin/sphingomyelin (L/S) ratios, obtained from lung washings, revealed a mean of 1.59:1 for the placebo group and 1.92:1 for the hexoprenaline group (p < 0.001). Pressure/volume curves were generated from the lungs of 24 fetuses from 10 does, and the volume of air in the lungs for each pressure was analyzed in four ways: total volume, volume per gram of fetal body weight, volume per gram of dry lung weight, and as a percentage of total lung capacity at a pressure of 40 cm H2O. A first and second inflation-deflation curve was obtained for each experiment. The lungs from the hexoprenaline-treated group retained significantly more air than those from the placebo group. The most significant comparison was obtained when lung volume was expressed per gram of dry lung weight. The possibility of administering a β2-sympathomimetic drug to the mother in advanced preterm labor, specifically to release surfactant in the fetal lung, is suggested.

Tracheal banding in weanling rats diminishes lung growth and alters lung architecture.

We banded the trachea of 4-wk-old male rats and studied lung growth, lung morphometry, and static pulmonary mechanics 4 wk later. We compared the experimental animals to sham-operated male littermates of the same age, 8-wk-old normal male littermates, and weight-matched rats of a younger age. Tracheal banded animals were smaller and had significantly smaller absolute lung volumes fewer alveoli, larger interalveolar wall distances, and increased alveolar duct size compared to the other groups. Their lung volumes were significantly smaller than were those of weight-matched controls. Air-filled pressure-volume curves from the tracheal ligation group were shifted to the left and upward when expressed as a percentage of total lung capacity or by fitting exponentials to the pressure-volume curves. There was no difference in saline-filled pressure-volume curves. We conclude that tracheal banding slows somatic growth and alters normal lung growth. Loss of elastic recoil appears to be due to alteration of surface forces.

Sites of airway dilatation in asthma following inhaled versus subcutaneous terbutaline: Comparison of physiologic tests with radionuclide lung images

In 12 asthmatic subjects with mild to severe airways obstruction, we compared the relative magnitude and sites of airway dilatation of a beta-adrenergic stimulant administered by different routes. Specific airway conductance (SG aw), peak expiratory flow, the sum of the absolute volume of isoflow and residual volume as a percentage of total lung capacity (capacity of isoflow) and the ratio of maximal expiratory flow at 50 per cent of vital capacity breathing 80 per cent helium-20 per cent oxygen to that breathing air (ratio V̇max 5) were determined before and after the administration of aerosolized terbutaline (0.5 mg), subcutaneous terbutaline (0.5 mg) or placebo. Increases in SG aw and peak expiratory flow of ≥ 25 per cent were considered to indicate significant dilatation of central airways; increases in ratio Vmax 50 of ≥ 0.10 and decreases in capacity of isoflow of ≥10 per cent were assumed to reflect dilatation of peripheral airways. In addition, radioaerosol and radioxenon lung imaging was performed to determine the relationship between changes in lung imaging patterns and changes in physiologic indices in response to bronchodilator therapy. Placebo caused little change in lung function or lung imaging. After inhaled terbutaline, SG aw and peak expiratory flow increased ≥25 per cent in seven subjects, ratio Vmax 50 increased ≥0.10 in only three subjects, capacity of isoflow decreased ≥10 per cent in only one subject, radioaerosol images showed less central deposition in nine subjects and radioxenon images showed improved distribution and/or washout of xenon in five subjects. After the administration of subcutaneous terbutaline, SG aw and peak expiratory flow increased ≥25 per cent in 10 subjects, ratio Vmax 50 increased ≥0.10 in 10 subjects, capacity of isoflow decreased ≥10 per cent in 11 subjects, and radioaerosol and xenon images showed improvement in 11 and eight subjects, respectively. These findings are consistent with the action of inhaled terbutaline mainly on large airways and of subcutaneous terbutaline on both large and small airways. Although reduced central radioaerosol deposition correlated well with physiologic evidence of large airway dilatation, improvement in xenon distribution and washout could be attributed to dilatation of either large and/or small airways.

Distribution of Ventilation in Normal Children

Measurements of closing volume and the distribution fo ventilation by both single-breath (SBN2) and multiple-breath nitrogen washout methods were obtained in 376 healthy boys and girls, ages 6 to 18 years. A closing volume could be demonstrated in 39 percent of the subjects, and closing volume expressed as percentage of vital capacity did not change with height. Closing capacity expressed as percentage of total lung capacity showed a slight decrease with height. The slope of phase III of the SBN2 curve decreased with height. Single compartment N2 washout curves were observed in 72 percent of the subjects, and the incidence of single compartment curves increased with age. In those subjects with two compartment N2 washout curves, the relative compartmental ventilation became more even with increasing height. Our observations suggest that parallel units among peripheral airways grow at different rates.