Changes in lung volume, lung density, and distribution of ventilation during hypobaric decompression.
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Adaptation, Physiological↗
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Effects of 10% formalin fixation on fixed lung volume and lung tissue shrinkage. A comparison of eleven laboratory species.
This species comparative study examined tissue shrinkage from a known physiologic lung volume through to the processed histologic section. Eleven mammalian species with body weights that spanned 3 orders of magnitude were studied. Air pressure-volume curves were determined to obtain total lung capacity (TLC) at 30 cmH2O. The lungs were then fixed by airway filling at 25 cmH2O pressure, and a displacement fixed lung volume was determined. Linear dimensions were systematically measured on fixed tissue blocks, embedded tissue blocks, and stained sections. Results indicated that the ratio of fixed lung volume to TLC ranged between 0.6 and 2.0. The corresponding ratios for linear dimensions ranged between 0.8 and 1.3 for all species. Histologic processing caused further shrinkage; the ratios of linear dimensions measured after and to those measured before processing ranged between 0.6 and 0.7. Thus, the degree of fixed lung volume achieved relative to TLC varies considerably more among species than does the histologic shrinkage caused by processing. We conclude that measurement of these changes in lung dimensions caused by fixation and histologic processing in the different species is essential, particularly in quantitative interspecies physiologic studies.
Animals↗
Ventilation, lung volumes and lung mechanics of young adult and old Syrian hamsters.
The breathing pattern, subdivisions of lung volume and quasistatic pressure-volume relationships of 15 and 65 week old hamsters (Mesocricetus auratus) anesthetized with halothane were measured by plethysmography. Body weights, tidal volumes and minute volumes of the younger and older groups were nearly identical. All lung volumes were larger in the older hamsters but there were no significant age-related differences in the relative proportions of lung volume subdivisions. Quasistatic lung compliance was greater in the older group but differences in pressure-volume relationships were not significant when volume was expressed as percent of total lung capacity. It appears that hamster lungs undergo significant volume changes with age during adulthood, but the pattern of change is different from that observed in man and dogs.
Age Factors↗
Acute changes of lung volumes and lung mechanics in asthma and in normal subjects.
Lung volumes, pulmonary mechanics, and specific airway conductance (sGaw) were studied before and 15 minutes after 200 microgram of aerosol salbutamol in nine asthmatics undergoing mild spontaneous exacerbations of their disease and in five normal subjects. In addition, three of the normal subjects were studied after voluntarily breathing at high lung volumes for one minute. The normal subjects and four of the asthmatics showed no overall changes in lung volumes or pressure-volume (PV) curves after salbutamol, even though airway dilatation was produced in the asthmatic subjects. In another five asthmatics, salbutamol induced a significant fall in the total lung capacity (TLC) in three, and in the residual volume and functional residual capacity in all five. There was a significant displacement of the PV curve downwards and to the right in all five, with increased lung compliance (Cl stat) in two. The fall in TLC could be accounted for by the increase in lung elasticity. There is reason to believe that this change in lung mechanics could be due to the reversal of asthma-induced stress relaxation. Sustained breathing at high lung volume is known to cause stress relaxation of the lung. However, this breathing pattern did not alter the PV curve or TLC in two of three normal subjects, which is consistent with stress relaxation being rapidly reversible. The other normal subject had an acute shift of the PV curve upwards and to the left after breathing at high lung volume. It has been concluded that stress relaxation is usually rapidly reversed but that in some individuals it may only be slowly reversed. This more persistent form of stress relaxation may contribute to the acute changes of TLC found in some asthmatics.
Adult↗
Effect of breathing helium-oxygen on static lung volumes and lung recoil in normal man.
Static lung volumes and static elastic recoil pressure (Pel) were measured in normal subjects breathing air and 80% helium plus 20% oxygen (He+O2). In 22 subjects, He+O2 produced small but significant increases in total lung capacity (TLC) (mean 0.11 liter, P less than 0.001) and residual volume (mean 0.10 liter, P less than 0.01) without change in vital capacity or functional residual capacity. The mechanisms for this change are obscure. In 10 subjects, breathing He+O2 had no significant effect on Pel (paired t-test) at any lung volume measured (50-80% TLC). In one subject, Pel at 70 and 80% TLC was significantly higher on air than on He+O2 (unpaired t-test, P less than 0.05). Because changes in lung volumes and lung recoil were small, we concluded that these effects do not negate the clinical utility of He+O2 flow-volume curves.
Adult↗
Effects of end-expiratory lung volume on lung mechanics in normal and edematous lungs.
This study determined the effects of end-expiratory pressures (EEP) and alterations in end-expiratory lung volume (EELV) on lung compliance (CL) and pulmonary resistance to gas flow (RP) in 20 cats with normal and edematous lungs. EELV was varied using EEP ranging from -8 to +10 cm H2O. Negative EEP was used to decrease EELV of the healthy lung causing CL to decrease and RP to increase. Positive EEP in the healthy lung also caused CL to decrease but did not significantly affect RP. After inducing pulmonary edema using alloxan, functional residual capacity (FRC) decreased 38%, CL decreased 66% and RP increased 106% (p less than 0.001). An EEP of 4 cm H2O returned EELV to normal FRC levels and produced maximum values for CL. Increases in EEP to 4 cm H2O also caused decreases in RP in the edematous lungs but further increase did not cause significant changes in RP. These results show that (1) relatively low levels of EEP returned EELV to normal FRC levels in alloxan-induced pulmonary edema, and (2) optimal lung mechanics were obtained when EELV was equal to or slightly above normal FRC values in both healthy and edematous lungs.
Alloxan↗
Effects of continuous distending pressure on lung volumes and lung mechanics in the immediate neonatal period.
The effects of CPAP and CNEP on lung mechanics and lung volumes were investigated in a group of 12 healthy newborn infants. Both resulted in a mild suppression of respiration. The fall in TPR50 was far greater during CPAP than during CNEP. Both led to a one third fall in dynamic compliance. Approximately 50% of the distending pressure was transmitted to the mediastinal structures whether applied as CPAP or CNEP.
Airway Resistance↗
Role of lung volume in lung injury: HFO in the atelectasis-prone lung.
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Animals↗
Lung volume maintenance prevents lung injury during high frequency oscillatory ventilation in surfactant-deficient rabbits.
Controversy exists whether high frequency oscillatory ventilation with an active expiratory phase (HFO-A) should be used at low ventilator pressures or high alveolar volumes to minimize lung injury in the atelectasis-prone lung. We therefore ventilated 20 anesthetized, tracheostomized rabbits made surfactant-deficient by lung lavage in 1 of 3 ways: HFO-A at a high lung volume (HFO-A/HI), HFO-A at a low lung volume (HFO-A/LO), or conventional mechanical ventilation (CMV); all received 100% oxygen for 7 h. We examined oxygenation, lung mechanics, and lung pathology. Arterial oxygenation in the HFO-A/HI rabbits was kept greater than 350 mm Hg. Mean lung volume above FRC in these animals was 23.4 ml/kg. In rabbits ventilated with HFO-A/LO and CMV, arterial oxygen tensions were 70 to 100 mm Hg. Mean lung volumes were 7.8 and 4.3 ml/kg, respectively. Total respiratory system pressure-volume curves (P-V curves) showed no change from baseline in the HFO-A/HI group after 7 h of ventilation. The low lung volume groups (HFO-A/LO and CMV) showed a diminution in hysteresis of their P-V curves, lower total respiratory system compliance, more hyaline membranes and severe airway epithelial damage. (All changes significant with p less than 0.05). We conclude that maintenance of alveolar volume is a key mechanism in the prevention of lung injury during mechanical ventilation of the atelectasis-prone lung. For optimal outcome using high frequency oscillatory ventilation, alveoli must be actively reexpanded and then kept expanded using appropriate mean airway pressures.
Airway Resistance↗
Flow-volume relationship at low lung volumes in healthy term newborn infants.
To describe the maximum expiratory flow-volume relationship in newborn infants, we simulated forced expiration by transiently applying positive pressure in a chamber surrounding the infant's body. Maximum expiratory flows were reached at any given lung volume when increases in chamber pressure failed to produce increases in flow. Maximum expiratory flows were achieved in seven of nine healthy newborn infants at lung volumes equal to functional residual capacity (FRC) andin all infants at lung volumes below FRC. The volume expired below FRC (6.4 ml/kg) was roughly equivalent to previously calculated values of expiratory reserve volume in newborn infants (7 ml/kg). The maximum expiratory flow volume curves showed that the infants were able to increase expiratory flow rates well above those achieved during tidal breathing. The convex shape of the curves at low lung volumes is compatible with flow limitation occurring in peripheral airways.
Functional Residual Capacity↗
[Donor-recipient lung volume matching in double lung transplantation. Value of left lower lobe graft].
For double lung transplantation, lung volume matching is easier comparing the predicted total lung capacities of the donor and recipient and the recipient's true TLC. The major concern in the inability to close the chest when the donor lungs are too large. The technique reported of left lower lobe implantation during bilateral single lung transplantation might be of great value in patients with small lung volume.
Adult↗
Effects of lung volume, volume history, and methacholine on lung tissue viscance.
We examined the effects of lung volume change and volume history on lung resistance (RL) and its components before and during induced constriction. Eleven subjects, including three current and four former asthmatics, were studied. RL, airway resistance (Raw), and, by subtraction, tissue viscance (Vtis) were measured at different lung volumes before and after a deep inhalation and were repeated after methacholine (MCh) aerosols up to maximal levels of constriction. Vtis, which average 9% of RL at base line, was unchanged by MCh and was not changed after deep inhalation but increased directly with lung volume. MCh aerosols induced constriction by increasing Raw, which was reversed by deep inhalation in inverse proportion to responsiveness. such that the more responsive subjects reversed less after a deep breath. Responsiveness correlated directly with the degree of maximal constriction, as more responsive subjects constricted to a greater degree. These results indicate that in humans Vtis comprises a small fraction of overall RL, which is clearly volume-dependent but unchanged by MCh-induced constriction and unrelated to the degree of responsiveness of the subject.
Adult↗
Measurement of lung volumes.
Measurements of lung volume play an integral role in the laboratory evaluation of patients with known or suspected lung disease. Several techniques are available to measure absolute lung volumes (containing residual volume). It should be noted that these techniques measure different theoretical volumes and may produce different results in patients with lung disease. Lung volume measurements are typically elevated in obstructive diseases and reduced in restrictive diseases, making them useful tests in diagnosing and distinguishing these two general classes of disease.
Humans↗
Changes in lung volume and lung-thorax compliance during cardiac surgery in children 11 days to 4 years of age.
To examine the effects of cardiac surgery and cardiopulmonary bypass (CPB) on the lung, functional residual capacity (FRC) and lung-thorax compliance were measured at four stages during open heart surgery in 15 children. The patients were anesthetized with fentanyl/droperidol and N2O/O2, paralyzed, and ventilated with volume-controlled mechanical ventilation at 20-30 breaths/min. FRC was measured by tracer gas washout. Static lung-thorax compliance (CLT) was calculated as tidal volume divided by the airway pressure difference between the end of the postinspiratory pause and the end of the expiration, and also from the increase in FRC caused by adding 5 cmH2O of PEEP (CLT[FRC]). Before skin incision, both FRC and compliance were closely correlated with weight and length. During this stage, FRC was 21 +/- 5 ml/kg, CLT 0.90 +/- 0.21, and CLT(FRC) 1.28 +/- 0.35 ml X cmH2O-1 X kg-1 X PEEP 5 increased FRC by 34 +/- 9%. In patients with intact pleural cavities throughout the operation (n = 10), FRC increased by 4 +/- 2 ml/kg when the sternum was retracted (P less than 0.01). During CPB, FRC decreased by 4 +/- 3 ml/kg (P less than 0.01), and FRC at the end of surgery was 5 +/- 4 ml/kg less than before skin incision (P less than 0.01). In these ten children, there was a 13% and 6% decrease in mean CLT and CLT(FRC), respectively, during the operation (P less than 0.05) and mean CLT(FRC) was at least 40% greater than CLT during all four stages (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Anesthesia↗
Lung volumes after an increase in lung distension in pneumonectomized ferrets.
To investigate the role of lung distension in compensatory lung growth, the right lung of each of 21 adult male ferrets was replaced with a silicone rubber balloon filled with mineral oil. Three to thirteen weeks after surgery, the oil was removed through a subcutaneous port. Lung volumes were measured serially until 3-6 wk after balloon deflation. With pneumonectomy the total lung capacity (TLC) decreased to less than 50% of the preoperative value and remained essentially unchanged while the balloon was inflated. At balloon deflation, TLC and vital capacity did not change immediately, whereas functional residual capacity increased by 44%, indicating a change of 2-3 cmH2O in end-expiratory transpulmonary pressure. TLC increased by 10% within 3 days and continued to increase over the subsequent 3-5 wk by a total of 25% over TLC at balloon deflation. There was little difference in this response between animals whose balloons were deflated 3 wk after surgery and those in which deflation was delayed up to 13 wk. After pneumonectomy in the adult ferret, the remaining lung increases in volume in response to an increase in lung distension even weeks or months after surgery. The extent to which this volume increase involves lung tissue growth or depends on previous lung resection is at present unknown. This model may be useful for studies of the mechanisms by which lung distension influences lung volume and compensatory lung growth.
Animals↗
Effect of increases in lung volume on clearance of aerosolized solute from human lungs.
To study the effect of increases in lung volume on solute uptake, we measured clearance of 99mTc-diethylenetriaminepentaacetic acid (Tc-DTPA) at different lung volumes in 19 healthy humans. Seven subjects inhaled aerosol (1 micron activity median aerodynamic diam) at ambient pressure; clearance and functional residual capacity (FRC) were measured at ambient pressure (control) and at increased lung volume produced by positive pressure [12 cmH2O continuous positive airway pressure (CPAP)] or negative pressure (voluntary breathing). Six different subjects inhaled aerosol at ambient pressure; clearance and FRC were measured at ambient pressure and CPAP of 6, 12, and 18 cmH2O pressure. Six additional subjects inhaled aerosol at ambient pressure or at CPAP of 12 cmH2O; clearance and FRC were determined at CPAP of 12 cmH2O. According to the results, Tc-DTPA clearance from human lungs is accelerated exponentially by increases in lung volume, this effect occurs whether lung volume is increased by positive or negative pressure breathing, and the effect is the same whether lung volume is increased during or after aerosol administration. The effect of lung volume must be recognized when interpreting the results of this method.
Aerosols↗
[Method of determining residual lung volume by vital lung capacity and age].
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Age Factors↗
[Estimation of lung volume and pulmonary blood volume from radioisotopic images].
Lung volume and pulmonary blood volume in man were estimated from the radioisotopic image using single photon emission computed tomography (SPECT). Six healthy volunteers were studied in a supine position with normal and altered lung volumes by applying continuous negative body-surface pressure (CNP) and by positive end-expiratory pressure (PEEP). 99mTc labeled human serum albumin was administered as an aerosol to image the lungs. The CNP caused the diaphragm to be lowered and it increased the mean lung tissue volume obtained by SPECT from 3.09 +/- 0.49 l for baseline to 3.67 +/- 0.62 l for 10 cmH2O (p less than 0.01), and to 4.20 +/- 0.67 l for 20 cmH2O (p less than 0.01 as compared with 10 cmH2O), respectively. The PEEP also increased the lung tissue volume to 3.68 +/- 0.68 l for 10 cmH2O as compared with the baseline (p less than 0.05), but there was no further increase in the volume after applying 15 cmH2O PEEP. The lung tissue volume obtained by SPECT showed a positive correlation with functional residual capacity measured by the He dilution method (r = 0.91, p less than 0.001). Pulmonary blood volume was estimated by taking the ratio of gamma-counts in the lung field to those in the intracardiac space (L/H ratio) after the equilibration of intravascular 99mTc-labeled red blood cells. The L/H ratio decreased after either the CNP or PEEP, suggesting a decrease in the blood volume per unit lung volume.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗