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PubMed2002

Increased surface tension decreases pulmonary capillary volume and compliance.

Increased surface tension is an important component of several respiratory diseases, but its effects on pulmonary capillary mechanics are incompletely understood. We measured capillary volume and specific compliance before and after increasing surface tension with nebulized siloxane in excised dog lungs. The change in surface tension was sufficient to increase lung recoil 5 cm H(2)O at 50% total lung capacity. Increased surface tension decreased both capillary volume and specific compliance. The changes in capillary volume and compliance were greatest at the lung volumes at which the surface tension change was greatest. Near functional residual capacity, capillary volume postsiloxane was approximately 30% of control. Presiloxane capillary specific compliance was approximately 7%/cm H(2)O near functional residual capacity and approximately 2.5%/cm H(2)O near total lung capacity. Postsiloxane capillary-specific compliance was 3%/cm H(2)O, and was independent of lung volume. We conclude that in addition to their well-known effects on lung mechanics, changes in surface tension also have important effects on capillary mechanics. We speculate that these changes may in turn affect ventilation and perfusion, worsen gas exchange, and alter leukocyte sequestration.

Animals↗

PubMed1989

Pulmonary function in preterm infants whose lungs were ventilated conventionally or by high-frequency oscillation.

To test the hypothesis that high-frequency ventilation may reduce the risk of barotrauma and thus the incidence of chronic pulmonary damage in preterm infants who need mechanical ventilation, we measured lung function before discharge in 53 infants who needed mechanical ventilation on the first day after birth and were randomly assigned to receive intermittent mandatory ventilation (n = 26) or to receive high-frequency oscillatory ventilation (n = 27). There were no significant differences between the groups in birth weight (mean +/- SD: 1010 +/- 240 vs 1030 +/- 230 gm), gestational age (29.1 +/- 2.0 vs 28.9 +/- 2.1 weeks), initial ventilatory support (mean airway pressure 7.2 +/- 1.8 vs 8.1 +/- 2.1 cm H2O; FiO2 0.62 +/- 0.24 vs 0.75 +/- 0.22), duration of mechanical ventilation (median (range): 6 (1 to 61) vs 10 (1 to 50) days) and duration of oxygen therapy (13 (1 to 109) vs 27 (4 to 227) days) for the intermittent mandatory ventilation group and the high-frequency oscillatory ventilation group, respectively. At the time of testing, weight was 1830 +/- 340 vs 1830 +/- 290 gm, and age was 68 +/- 24 vs 70 +/- 31 days. Respiratory flows were determined by pneumotachygraphy, esophageal pressure through a water-filled feeding tube, and functional residual capacity by N2 washout. Both groups had abnormal lung function with decreased lung compliance (1.65 +/- 0.51 vs 1.54 +/- 0.36 ml/cm H2O) and elevated pulmonary resistance (102 +/- 24 vs 107 +/- 36 cm H2O/L/sec). Functional residual capacity was in the normal range (30.6 +/- 6.0 vs 28.2 +/- 10.7 ml) in both groups. There were no significant differences in lung function between the two treatment groups. These results do not support the hypothesis that high-frequency oscillatory ventilation reduces the risk of lung damage in preterm infants.

Female↗

PubMed1993

Effect of positive expiratory pressure on breathing pattern in healthy subjects.

The purpose of this study was to register breathing patterns, in healthy subjects, during breathing with a positive expiratory pressure. Integrated electromyographic (IEMG) activity of the following muscles was assessed: scalene muscle, parasternal muscle and abdominal muscles, using surface electrodes. Inspiration time, expiration time, total breathing cycle time, tidal volume and breathing frequency were measured using a water-sealed spirometer. Functional residual capacity was measured using a body plethysmograph. Oxygen uptake and carbon dioxide output were measured using an automatized ergometry set-up. All measurements were performed during undisturbed breathing and during breathing with positive expiratory pressures of 5 and 15 cmH2O. Phasic activity, but not tonic activity, of the scalene muscles and the abdominal muscles increased significantly during breathing with the expiratory pressures. No significant change was observed in phasic or tonic activity of the parasternal muscle. Mean (SD) tidal volume increased significantly from 0.8(0.2) l during undisturbed breathing to 1.1(0.3) l and 1.5(0.7) l during breathing with the expiratory pressures of 5 cmH2O and of 15 cmH2O, respectively. Respiration times, breathing frequency, oxygen uptake, carbon dioxide output and functional residual capacity remained unchanged. It can be concluded that, in healthy subjects, positive expiratory pressure increases tidal volume by activity of both expiratory and inspiratory muscles, while functional residual capacity remains unchanged. The changes appeared to be pressure dependent.

Adult↗

PubMed1984

Analysis of alveolar ventilation in the newborn.

Twelve healthy term infants were examined at the median ages of 2 1/2 and 26 hours. Their alveolar ventilation, efficiency of ventilation, functional residual capacity, and lung nitrogen elimination patterns were studied by means of a computerised nitrogen wash out method. The results showed that alveolar ventilation and functional residual capacity increased over the period studied. At the same time effective dead space decreased leaving minute ventilation unchanged. Distribution of ventilation did not change.

Aging↗

PubMed1993

Respiratory mechanics in infants and young children before and after repair of left-to-right shunts.

In an attempt to investigate the relationship between respiratory mechanics and pulmonary hemodynamics, we evaluated pulmonary function in 31 infants with left-to-right shunts and subsequent high pulmonary blood flow, undergoing cardiac surgery. Measurements were performed 1 d before and repeated 10 d and 4-5 wk after correction. The age of the patients ranged from 4 d to 24 mo, body weight from 2.7 to 11.8 kg. Pulmonary artery pressure, assessed by Doppler echocardiography, was preoperatively elevated in 23 patients (group 1), whereas it was within normal values in eight infants (group 2). Respiratory mechanics were measured using the single-breath occlusion technique in sedated infants. To evaluate specific compliance, functional residual capacity was determined by using an open circuit nitrogen washout technique. A reduced preoperative compliance value (mean with 95% confidence interval) was found in group 1: 34.8 (26.5-43.1) mL.kPa-1. After hemodynamic correction, a progressive significant (p < 0.01) improvement was demonstrated at 10 d and 1 mo with values of 47.5 (39.2-55.8) mL.kPa-1 and 56.5 (45.6-67.4) mL.kPa-1, respectively. A similar trend was noted evaluating specific compliance with values of 0.27 (0.24-0.30) kPa-1 and 0.44 (0.42-0.46) kPa-1, respectively before and after surgery. Preoperative functional residual capacity value was 130 (100-160) mL. In group 2, normal preoperative compliance values were obtained, without significant changes after surgery. In both groups, resistance was within the normal range both before and after surgical correction, and functional residual capacity did not change either. No correlations were found between compliance and pulmonary artery pressure and pulmonary blood flow values.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗

PubMed2002

Evaluation of work of breathing in spontaneously breathing animals during partial liquid ventilation.

BACKGROUND: Partial liquid ventilation improves lung mechanics and gas exchange in paralyzed mechanically ventilated animals. OBJECTIVE: Examine the work of breathing (WOB) in a spontaneously breathing animal model during partial liquid ventilation with and without the use of pressure-support ventilation (PSV). METHODS: This was a prospective study including 6 lambs (mean weight 10.9 +/- 1.3 kg). Baseline measurements, including total work of breathing (WOB(T)), elastic work of breathing (WOB(E)), and resistive work of breathing (WOB(R)), were obtained using pressure-controlled synchronized intermittent mandatory ventilation with positive end-expiratory pressure of 5 cm H(2)O at PSV levels of 0, 5, and 10 cm H(2)O. The animals' lungs were filled with perflubron through an endotracheal tube, in 10-20 mL aliquots, until filled, approximately 30 mL/kg or functional residual capacity. Repeat measurements were obtained at 10 mL/kg, 20 mL/kg, and full. Perflubron was then allowed to evaporate from the lungs and repeat measurements were obtained 3 additional times, with at least a 1 hour separation between phases, for up to 7 hours after the lungs were filled. RESULTS: No differences were detected in WOB(T), WOB(R), or WOB(E) between the gas-filled lung and the lung filled to functional residual capacity with perflubron. However, compared to the gas-filled lung, WOB(T) and WOB(R) were higher during the filling (p < 0.05) and evaporative phases (p < 0.05). The PSV level affected WOB. Work of breathing was least at PSV 10 cm H(2)O. CONCLUSION: In this pilot study of healthy animals breathing spontaneously with perflubron-filled lungs, there was an acceptable amount of WOB, which decreased with the addition of PSV. However, WOB increased when the perflubron level was not maintained at functional residual capacity.

Airway Resistance↗

PubMed2000

Thermodilution versus inert gas rebreathing for estimation of effective pulmonary blood flow.

OBJECTIVE: To compare measurements of the effective pulmonary blood flow (Qep, i.e., nonshunted fraction of cardiac output, Qt) by the inert gas rebreathing (RB) method and the thermodilution (TD) technique in critically ill patients. DESIGN: Prospective, comparative study of a noninvasive method and an established invasive technique. SETTING: An 11-bed general intensive care unit in a university hospital. PATIENTS: A total of 14 critically ill patients, all mechanically ventilated and monitored with systemic and pulmonary artery catheters. MEASUREMENTS AND MAIN RESULTS: Qep was determined in duplicate by RB using a mass spectrometer for gas analysis. For each determination, Qt was measured in triplicate by the cold water bolus TD technique and averaged. Simultaneously mixed venous and arterial blood samples were analyzed to calculate the intrapulmonary shunt fraction and thereby convert estimates of Qt to Qep. Mean difference between paired estimates (RB - TD) was 0.01 L/min, so for differences was 1.19 L/min, and 95% confidence interval for the bias was -0.45 to 0.47 L/min. Coefficients of variation for repeated Qep estimates were 8% (RB) and 12% (TD), respectively. Coefficients of variation for RB estimates of functional residual capacity and lung tissue volume were 6% and 17%, respectively. CONCLUSIONS: The RB method is a promising method for simultaneous noninvasive estimation of Qep and functional residual capacity in mechanically ventilated patients. However, further investigations are needed to evaluate potential problems of the method before it can be recommended for clinical purposes.

Adult↗

PubMed1998

Role of reaction resistance in limiting carbon monoxide uptake in rabbit lungs.

The contribution of reaction resistance to overall resistance to pulmonary carbon monoxide (CO) uptake [DLCO/(ThetaCO . Vc), where DLCO is lung CO diffusing capacity, ThetaCO is CO uptake conductance of erythrocytes, and Vc is pulmonary capillary blood volume] was determined in 10 anesthetized, paralyzed, and artificially ventilated rabbits. On the basis of the classical double-reciprocal equation of F. G. W. Roughton and R. E. Forster (J. Appl. Physiol. 11: 290-302, 1957), DLCO/(ThetaCO . Vc) was obtained by solving the relation DLCO/(ThetaCO . Vc) = 1 - 2/(DLNO/DLCO), where DLNO/DLCO represents the ratio between the respective single-breath diffusing capacities (DL) of nitric oxide (NO) and CO pulmonary capillary blood. The lungs of eight rabbits were inflated, starting from residual volume, by using 55 ml of indicator gas mixture (0.2% CO and 0.05% NO in nitrogen). DL values were calculated by taking the end-tidal partial pressures of CO and NO as analyzed by using a respiratory mass spectrometer. The overall value was DLCO/(ThetaCO . Vc) = 0.4 +/- 0.025 (mean +/- SD). Because of the use of O2-free indicator gas mixtures, the end-tidal O2 partial pressures were approximately 21 Torr. In one other rabbit, the application of 0.2% CO and 0.001% NO yielded DLCO/(ThetaCO . Vc) = 0.39; in the tenth rabbit, however, inspiratory volume was varied, and an identical value was found at functional residual capacity. We conclude that the contribution of reaction resistance to overall resistance to pulmonary CO uptake is independent of the inspiratory NO concentration used, including, with respect to the pertinent literature, the conclusion that in rabbits, dogs, and humans this contribution amounts to 40% when determined at functional residual capacity.

Animals↗

PubMed1993

Effect of posture on static lung volumes and pulmonary mechanics in pneumonectomized rabbits.

Static lung volumes, lung (CL) and respiratory system compliance (Crs), and the slope of phase III of the single-breath O2 test (slope III) were measured in rabbits in the prone, supine, and right and left lateral positions. Control rabbits, rabbits that had the left lung removed (Px), and rabbits that had the left lung removed and replaced with wax (Px + W) were studied. Surgeries were performed > or = 7 wk before study. Lung volumes, Crs, and slope III were not different among groups. Total lung capacity, vital capacity, residual volume, Crs, and slope III were smallest in all rabbits in the prone position. Functional residual capacity and expiratory reserve volume were unaffected by posture in control rabbits but were larger in Px and Px + W rabbits in the left lateral position. CL was unaffected by posture but was smaller in Px and Px + W rabbits than in control rabbits. Pneumonectomy-induced changes in lung shape altered the effect of posture on functional residual capacity but not on regional lung function, as assessed by the single-breath O2 test.

Airway Resistance↗

PubMed2004

Comparison of lung volume measurements in individuals with spinal cord injury by two different methods.

BACKGROUND/OBJECTIVE: Few detailed studies have been performed among subjects with spinal cord injury (SCI) using whole body plethysmography for measurement of static lung volumes. Because abdominal gas volumes and respiratory patterns among subjects with varying levels of SCI may differ significantly from able-bodied individuals, methodological concerns related to this technique could conceivably lead to inaccuracies in lung volume measurements. The purpose of this study was to compare lung volume parameters obtained by whole body plethysmography with those determined by the commonly used nitrogen washout technique among individuals with SCI. PARTICIPANTS: Twenty-nine clinically stable men, 14 with chronic tetraplegia (injury C4-C7) and 15 with paraplegia (injury below T5) participated in the study. METHODS: Lung volumes were obtained using whole body plethysmography and the open-circuit nitrogen washout technique. Within both study groups, data were evaluated by the paired Student's t test and by determination of correlation coefficients. RESULTS: No statistically significant differences for any lung volume parameter were found within either group. In subjects with tetraplegia on paraplegia, respectively, strong correlation coefficients were found for measurements of total lung capacity (.86 and .97), functional residual capacity (.87 and .96), and residual volume (.77 and .85). CONCLUSION: These findings indicate that body plethysmography is a valid technique for determining lung volumes among subjects with SCI. Because airway resistance measurements can also be obtained during same study sessions for assessment of airway caliber and bronchial responsiveness, body plethysmography is a useful tool for examining multiple aspects of pulmonary physiology in this population.

Adult↗

PubMed1998

Total respiratory system compliance after thoracoplasty.

Recent attention has been directed towards the deleterious effects of the sequelae of pulmonary tuberculosis on respiratory function. Thus, a study was undertaken to find out to what extent the deformity of thorax after thoracoplasty increases the mechanical work of breathing. Compliance of the total respiratory system (Crs) was measured with a pressure-type body plethysmograph in nine post-thoracoplasty tuberculosis patients, 15 patients with pulmonary tuberculosis and three patients with pleural diseases. Mean Crs in nine post-thoracoplasty tuberculosis patients was 0.0861 cmH2O-1, and that in six patients with moderately advanced pulmonary tuberculosis was 0.0841 cmH2O-1. Mean Crs (0.1301 cmH2O-1) in nine patients with a minimum lesion of tuberculosis was not different from the reference Crs values reported to date by several authors. Crs was significantly correlated with vital capacity, but not with functional residual capacity. There was no difference in specific Crs between post-thoracoplasty tuberculosis patients and patients with moderately advanced pulmonary tuberculosis. Crs of patients with a pleural disease was smaller than Crs of patients with a minimal lesion of pulmonary tuberculosis. The deformity of thorax after thoracoplasty caused a decrease of Crs. However, ventilation is not as severely impaired as anticipated from the degree of thorax deformity on chest X-ray film, providing that movement of the diaphragm is unrestricted.

Adult↗

PubMed1980

Postural effects on lung volumes and asynchronous ventilation in anesthetized horses.

Quasi-static pressure-volume curves and single-breath nitrogen washouts were performed simultaneously on eight anesthetized horses (average body wt = 485 kg) in left lateral, right lateral, prone, and supine postures (sequence randomized). The shift from prone to lateral or supine posture decreased expiratory reserve volume (ERV), vital capacity (VC), residual volume (RV), functional residual capacity (FRC), and total lung capacity (TLC); RV and FRC expressed as %TLC were unchanged, suggesting that in the lateral and supine postures a significant portion of the lung volume was not recruited by VC maneuvers. Phase III slope increased from 0.13 %N2/l in prone horses to 0.34 %N2/l in the lateral and supine positions. The onset of phase IV was not significantly different from FRC in the prone or laterally recombent animal, but exceeded FRC in the supine horse. The sequence of body positions had no effect on any of our results indicating that all changes in lung volumes and regional asynchronous ventilation c;n be reversed by placing the horse in the prone posture. The reduction in lung volume and increased asynchronous ventilation in the lateral and supine horse suggests that impaired gas exchange in anesthetized horses is predominantly related to posture, and not general anesthesia.

Anesthesia, General↗

PubMed1993

Longitudinal evaluation of pulmonary function in infants and very young children with cystic fibrosis.

Thirty-two infants with cystic fibrosis (CF) had pulmonary function testing and chest radiographs at the time of diagnosis and on average 1 year later, when they had no acute respiratory symptoms. At diagnosis, 14 of 32 infants had respiratory symptoms (RESP) and 18 did not have respiratory symptoms (NRESP). There were no significant differences in age, weight, or length between the RESP and NRESP groups. At diagnosis, the RESP group had significantly lower forced expiratory flows compared to the NRESP group (41 +/- 32% vs. 98 +/- 48% predicted); however, there were no significant differences in functional residual capacity or chest radiographic scores. Between diagnosis and follow-up, the NRESP group had no significant change in pulmonary function but a decline in chest roentgenographic (CXR) scores (22 +/- 2 to 21 +/- 2). For infants in the RESP group, there were no significant changes in FRC or CXR score. Maximal expiratory flow at functional residual capacity (Vmax FRC) rose from diagnosis to 1 year follow-up (41 +/- 32% to 74 +/- 27% predicted; P < 0.002); however, at follow-up flows for the RESP group remained significantly lower than flows for the NRESP group (74% vs. 113% predicted; P < 0.0005). For the 32 infants with CF, there was significant correlation between percent predicted Vmax FRC at follow-up and at diagnosis (r = 0.47; P < 0.02). Those infants with lower percent predicted flows at diagnosis were more likely to have lower percent predicted flows 1 year later.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗

PubMed1981

[The influence of septum deviation on lung function (author's transl)].

We examined the influence of septal deviations on pulmonary function in 247 study patients, and compared results with a control group of 387 patients without septal deformities. Tracheobronchial resistance, functional residual capacity and nasal resistance were measured by body plethysmography. Those patients with septal deformities had a 2.4 mm mean increase of tracheobronchial resistance, which was highly significant using the T-test between the two groups (P 1/2, 0.003%). We presume a probable reflex influence for this. However, the functional residual capacity in these patients was not significantly increased. Comparative measurements of pulmonary function before and after septal surgery showed decrease of tracheobronchial resistance in 66.7% of the patients. As a result of these findings, we believe that a close interdependence between nasal and pulmonary function seem probable.

Adult↗

PubMed1990

Respiratory changes in diaphragmatic intramuscular pressure.

We attempted to measure diaphragmatic tension by measuring changes in diaphragmatic intramuscular pressure (Pim) in the costal and crural parts of the diaphragm in 10 supine anesthetized dogs with Gaeltec 12 CT minitransducers. During phrenic nerve stimulation or direct stimulation of the costal and crural parts of the diaphragm in an animal with the chest and abdomen open, Pim invariably increased and a linear relationship between Pim and the force exerted on the central tendon was found (r greater than or equal to 0.93). During quiet inspiration Pim in general decreased in the costal part (-3.9 +/- 3.3 cmH2O), whereas it either increased or slightly decreased in the crural part (+3.3 +/- 9.4 cmH2O, P less than 0.05). Similar differences were obtained during loaded and occluded inspiration. After bilateral phrenicotomy Pim invariably decreased during inspiration in both parts (costal -4.3 +/- 6.4 cmH2O, crural -3.1 +/- 0.6 cmH2O). Contrary to the expected changes in tension in the muscle, but in conformity with the pressure applied to the muscle, Pim invariably increased during passive inflation from functional residual capacity to total lung capacity (costal +30 +/- 23 cmH2O, crural +18 +/- 18 cmH2O). Similarly, during passive deflation from functional residual capacity to residual volume, Pim invariably decreased (costal -12 +/- 19 cmH2O, crural -12 +/- 14 cmH2O). In two experiments similar observations were made with saline-filled catheters. We conclude that although Pim increases during contraction as in other muscles, Pim during respiratory maneuvers is primarily determined by the pleural and abdominal pressures applied to the muscle rather than by the tension developed by it.

Animals↗

PubMed1982

Improvement in lung mechanics as a function of age in the infant with severe bronchopulmonary dysplasia.

Pulmonary function tests were performed in two groups of infants with bronchopulmonary dysplasia; a group less than 7 months of age with severe ventilator-dependent respiratory failure (Group A), and a group 7-22 months of age during resolution of their disease (Group B). Group A patients had significantly elevated minute volume, low specific compliance, elevated inspiratory and expiratory pulmonary resistance, and low functional residual capacity. Group B patients also demonstrated elevated minute volume, whereas specific compliance, inspiratory pulmonary resistance and functional residual capacity were within normal limits, and expiratory pulmonary resistance was only slightly above normal. With the exception of minute volume, the differences between the groups were significant (P less than 0.05). Sequential studies of resistance and compliance over 4-5 months in two patients in the younger group demonstrated values that approached or achieved normal range. It is concluded that pulmonary mechanics improve with age in the infant with severe bronchopulmonary dysplasia.

Aging↗

PubMed1987

Abnormalities of lung mechanics in young asthmatic children.

Measurements of total compliance of the respiratory system by the weighted spirometer technique and of the functional residual capacity by helium gas dilution were attempted in 86 asthmatic children aged 2.2-7.9 years. In all but six of the 86 children reliable measurements could be obtained. Significantly raised functional residual capacity was detected in children with asthma of all degrees of severity. The compliance of the respiratory system was significantly abnormal (reduced) only in children who had symptoms at the time of measurement or who had chronic persistent asthma. The results indicate that these measurements are well tolerated in young asthmatic children. Further work needs to be undertaken to assess the value of this technique in following the response to treatment.

Asthma↗

PubMed1991

Oxygen cost of inspiratory loading: resistive vs. elastic.

We measured the O2 cost of breathing (VO2resp) against external inspiratory elastic (E) and resistive loads (R) when end-expiratory lung volume, tidal volume, breathing frequency, work rate, and pressure-time product were matched in each of six pairs of runs in six subjects. During E, peak inspiratory mouth pressure was 65.7 +/- 1.8% (SD) of the maximum at functional residual capacity. However, during resistive runs, peak inspiratory mouth pressure was 41.1 +/- 2.8% of the maximum at functional residual capacity. In 36 paired runs, where both work rate and pressure-time product were within 10%, VO2resp for E was less than for R (81 and 96 ml/min, respectively; P less than 0.01). During loaded and unloaded breathing with the same tidal volume, we measured the changes in anteroposterior diameter of the lower rib cage in five subjects. In four subjects we also recorded the electromyograms of several fixator and stabilizing muscles. During E and R, the change in anteroposterior diameter of the lower rib cage was -116 +/- 5 and -45 +/- 4% (SE), respectively, of the unloaded value (P less than 0.01), indicating greater deformation during E. Although the peak electromyographic activity was 72 +/- 16% greater during E (P less than 0.01), there was no difference between the loads for area under the electromyogram time curve (P greater than 0.05). However, the time to 50% peak activity was less during R (P less than 0.02). We conclude that, even when work rate and pressure-time product are matched, VO2resp during R is greater than that during E. This difference may be due to preferential recruitment of faster and less efficient muscle fibers.

Adult↗