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PubMed2002

Effect of gravity and posture on lung mechanics.

The volume-pressure relationship of the lung was studied in six subjects on changing the gravity vector during parabolic flights and body posture. Lung recoil pressure decreased by approximately 2.7 cmH(2)O going from 1 to 0 vertical acceleration (G(z)), whereas it increased by approximately 3.5 cmH(2)O in 30 degrees tilted head-up and supine postures. No substantial change was found going from 1 to 1.8 G(z). Matching the changes in volume-pressure relationships of the lung and chest wall (previous data), results in a decrease in functional respiratory capacity of approximately 580 ml at 0 G(z) relative to 1 G(z) and of approximately 1,200 ml going to supine posture. Microgravity causes a decrease in lung and chest wall recoil pressures as it removes most of the distortion of lung parenchyma and thorax induced by changing gravity field and/or posture. Hypergravity does not greatly affect respiratory mechanics, suggesting that mechanical distortion is close to maximum already at 1 G(z). The end-expiratory volume during quiet breathing corresponds to the mechanical functional residual capacity in each condition.

Adult↗

PubMed1983

Effect of the Mueller manoeuvre at different lung volumes on left ventricular performance in normal subjects.

The effect of reduced intrathoracic pressure at different lung volumes on cardiac function was assessed by echocardiographic measurements of left ventricular size in normal subjects who performed the Mueller manoeuvre at two preselected lung volumes. At functional residual capacity (FRC), both mean end-diastolic dimension and mean end-systolic dimension increased (5.1 +/- 0.4 to 5.4 +/- 0.5 cm; P less than 0.001 and 3.7 +/- 0.4 to 3.9 +/- 0.4 cm; P less than 0.025, respectively). At high lung volume (HLV), midway between FRC and total lung volume, mean end-diastolic dimension increased from 5.1 +/- 0.5 to 5.3 +/- 0.5 cm (P less than 0.001), less than than the increase at FRC, and mean end-systolic dimension increased from 3.5 +/- 0.4 to 3.9 +/- 0.4 cm (P less than 0.001), similar to the increase at FRC. Thus, mean stroke dimension and shortening fraction were reduced at HLV (1.5 +/- 0.2 to 1.3 +/- 0.2 cm and 30 +/- 4 to 26 +/- 2% respectively, P less than 0.025). At FRC and HLV respectively, mean left ventricular transmural pressure increased from 111 to 129 Torr (P less than 0.001) and from 111 to 128 Torr (P less than 0.001) in response to the Mueller manoeuvre, although intraesophageal (intrathoracic) pressure was significantly lower (P less than 0.001) during the Mueller manoeuvre at HLV. These results show that lung volume affects the left ventricular response to the Mueller manoeuvre. Furthermore, the changes in left ventricular dimensions induced by the Mueller manoeuvre are determined by the level of reduced intrathoracic pressure, through differing effects on left ventricular afterload and filling.

Adult↗

PubMed1989

The influence of anesthesia and postoperative analgesic management of lung function.

General anesthesia itself may influence postoperative lung function. It leads to a depression of the functional residual capacity, which, in combination with surgical trauma and postoperative pain, can provoke insufficient breathing, retention of bronchial secretions, and atelectasis. Regional anesthesia has no influence on lung function. After upper abdominal or thoracic surgery, postoperative epidural analgesia causes a significant increase of lung function as compared with systemic analgesia. The combination of regional anesthesia and general anesthesia intraoperatively appears to reduce lung function much less than general anesthesia alone.

Analgesia, Epidural↗

PubMed1991

Gastro-oesophageal reflux and respiratory function in infants with respiratory symptoms.

This study aimed to define the incidence and severity of gastro-oesophageal reflux (GOR), as measured using 24 hour oesophageal pH monitoring, in 38 infants with recurrent respiratory symptoms and to relate these findings to measures of respiratory function. Twenty one infants had a pH under 4 for more than 5% of the time (one definition of abnormal GOR) and nine had GOR exceeding age related normal values. Maximum expiratory flow at functional residual capacity was reduced in 37 infants, airways resistance was raised in 19 infants, and thoracic gas volume was abnormal in 11 infants. There was no association between indices of GOR and measures of lung function whether assessed by correlation or by chi 2 analysis for normal versus abnormal values. However, individual infants appeared to have respiratory symptoms produced by GOR. This suggests that host responsiveness to GOR may be of greater relevance than the amount of GOR.

Female↗

PubMed1993

Inhaled ipratropium bromide and terbutaline in asthmatic children.

Inhaled bronchodilator therapy in young asthmatic children reduces symptoms and improves lung function. After a single dose of therapy, however, lung function may still be abnormal, as evidenced by an elevated function residual capacity (FRC). The aims of this study were to assess if a second dose of bronchodilator therapy resulted in further improvement in lung function and to determine whether additional therapy was more effective if given as a second dose of a beta-adrenergic agonist or if instead an anticholinergic was used. Twenty-one asthmatics (median age 7.5 years) received in random order on two separate occasions, 1 week apart, either two doses of terbutaline (500 micrograms) or terbutaline plus ipratropium bromide (20 micrograms). FRC and peak expiratory flow rate (PEFR) were measured immediately prior to and then 20 min after each dose of bronchodilator therapy. In the group, overall FRC and PEFR improved after the first and second dose of bronchodilator, regardless of regime used, the response to the second dose, however, was smaller than the first dose. There was no significant difference overall between the two regimes in baseline FRC or PEFR, or FRC and PEFR measured after each dose of bronchodilator. Eight children failed to show a significant change in FRC following two doses of terbutaline, but seven of these eight did have a significant change in FRC in response to the combination of terbutaline and ipratropium bromide. We conclude that a second dose of bronchodilator therapy does further improve lung function. Our results suggest the more efficacious regime consists of a combination of single doses of ipratropium bromide and terbutaline.

Administration, Inhalation↗

PubMed1986

Resting lung function in children after repair of tetralogy of Fallot.

Children with tetralogy of Fallot had pulmonary function tests (PFT) after intracardiac repair (ICR). According to the age at time of ICR and to the existence or not of palliative surgery preceding ICR, they were divided into three groups. Group 1 had ICR at a mean of one year one month of age (range four months to one year seven months), that is, during the active period of postnatal lung growth. Groups 2 and 3 had ICR later in childhood, that is, respectively, at four years seven months (range two years nine months to 11 years 9 months) and at five years four months (range two years seven months to 11 years five months). In group 3, ICR was preceded by palliative surgery. The PFT at rest included measurement of lung volumes (functional residual capacity), vital capacity (VC), dynamic or static compliance (CL), total pulmonary resistance, lung transfer factor for CO (TLCO) and blood gases. Group 1 had normal lung function suggesting that early repair of TOF saves lung development. In groups 2 and 3, significant decrease in VC(p less than 0.01) and CL (p less than 0.01) were found suggesting impaired alveolar growth. Additional defect in TLCO (p less than 0.01) in group 3 suggested that palliative surgery induces abnormal vascular growth. Thus, the present functional results suggest repair of TOF during the two first years of life, ie, the active period of postnatal lung growth.

Adolescent↗

PubMed2001

Functional magnetic stimulation for conditioning of expiratory muscles in patients with spinal cord injury.

OBJECTIVE: To evaluate the effectiveness of functional magnetic stimulation (FMS) in conditioning expiratory muscles patients with spinal cord injury (SCI). DESIGN: A prospective before-after trial. SETTING: The Functional Magnetic Stimulation Laboratory of the SCI Health Care Group, VA Long Beach Health Care System, and the Spinal Cord Injury Services, Department of Veterans Affairs, Palo Alto Health Care System. PARTICIPANTS: Eight men with tetraplegia. INTERVENTION: Expiratory muscle training was achieved by placing a magnetic stimulator with a round magnetic coil along subjects' lower thoracic spine. MAIN OUTCOME MEASURES: Measures taken were the maximal expired pressure at total lung capacity (MEP-TLC) and at functional residual capacity (MEP-FRC), expiratory reserve volume (ERV), and the forced expiratory flow rate at TLC (FEF-TLC) and at FRC (FEF-FRC) by subjects' voluntary maximal efforts. RESULTS: After 4 weeks of conditioning, the mean +/- standard error of the mean values were: MEP-TLC, 55.3 +/- 8.6cmH(2)O; MEP-FRC, 29.6 +/- 5.6cmH(2)O; ERV,.57 +/-.08L; FEF-TLC, 4.3 +/- 0.5L/s; and FEF-FRC, 1.9 +/- 0.2L/s. These values correspond to, respectively, 129%, 137%, 162%, 109%, and 127% of pre-FMS conditioning values. When FMS was discontinued for 2 weeks, the MEP-TLC returned to its pre-FMS training value. CONCLUSION: A 4-week protocol of FMS of the expiratory muscles improves voluntary expiratory muscle strength significantly, indicating that FMS can be a noninvasive therapeutic technology in respiratory muscle training for persons with tetraplegia.

Analysis of Variance↗

PubMed1986

Effect of lung volume on pulmonary mechanics in guinea pigs.

The lung volume (VL) dependence of several dynamic pulmonary mechanical properties of the guinea pig lung were determined over the range of the vital capacity (10-100% VC) with the vagi intact and sectioned. We found dynamic compliance to be strongly VL dependent, decreasing as much as 85% between functional residual capacity (FRC) and total lung capacity (TLC). Below FRC, dynamic compliance either remained unchanged or decreased, depending upon the technique used in its measurement. Pulmonary resistance (RL) decreased monotonically with increasing VL, whereas pulmonary conductance was linearly related to VL. Conductance was much less sensitive to VL than compliance, increasing only 28% between FRC and TLC. The sensitivity of pulmonary conductance to VL was substantially increased by subtracting the resistance of the tracheal cannula from RL. Specific pulmonary conductance was not independent of VL but decreased approximately 45% over the range of the VC. Pulmonary inertance was found to be unaffected by VL. Extrapolation from these data indicate that small differences in FRC, which might be expected within and between studies relying on pulmonary mechanical measurements, would most strongly affect compliance estimates and only moderately alter resistance estimates. It also indicates that the use of specific pulmonary conductance does not remove VL as an independent variable.

Airway Resistance↗

PubMed2002

Deep breaths, methacholine, and airway narrowing in healthy and mild asthmatic subjects.

Deep breaths taken before inhalation of methacholine attenuate the decrease in forced expiratory volume in 1 s and forced vital capacity in healthy but not in asthmatic subjects. We investigated whether this difference also exists by using measurements not preceded by full inflation, i.e., airway conductance, functional residual capacity, as well as flow and residual volume from partial forced expiration. We found that five deep breaths preceding a single dose of methacholine 1) transiently attenuated the decrements in forced expiratory volume in 1 s and forced vital capacity in healthy (n = 8) but not in mild asthmatic (n = 10) subjects and 2) increased the areas under the curve of changes in parameters not preceded by a full inflation over 40 min, during which further deep breaths were prohibited, without significant difference between healthy (n = 6) and mild asthmatic (n = 16) subjects. In conclusion, a series of deep breaths preceding methacholine inhalation significantly enhances bronchoconstrictor response similarly in mild asthmatic and healthy subjects but facilitates bronchodilatation on further full inflation in the latter.

Adult↗

PubMed1988

[Cardiopulmonary adaptation to birth].

The cardio-pulmonary situation of the foetus is very special; certain changes occurring at the end of pregnancy make preparations for extra-uterine life. In the foetus, the two ventricles eject different outputs to the systemic and pulmonary circulation, these communicate between each other by the ductus arteriosus and the foramen ovale. The pulmonary output is very small on account of the high pulmonary resistance. The lungs do not participate in gas exchange (ensured by the placenta) they secrete a liquid maintaining airway distension; the synthesis of surfactant, whose role will be vital after birth, begins at the end of the second trimester of pregnancy. Dramatic changes occur at birth. The two ventricles now function in series, the shunts between the two circulations are shut. The lowering of the pulmonary vascular resistance, the aeration of the lungs, the formation of the functional residual capacity and the appearance of a regular and rhythmic respiration now enable the new born to ensure its own gas exchange.

Adaptation, Physiological↗

PubMed2000

Overall and peripheral inhomogeneity of ventilation in patients with stable cystic fibrosis.

We studied distribution of ventilation in patients with cystic fibrosis (CF) who had not had an exacerbation for some time. Patients performed either the vital capacity nitrogen (N(2)) single-breath washout test (VC test) or a modified single-breath washout consisting of 1 L inspired from functional residual capacity (FRC test) of 90% oxygen (O(2)), 5% helium (He), and 5% sulfur hexafluoride (SF(6)). We computed the slopes of phase III of N(2) concentration from the VC test (S(N2) (VC)) and the phase III slopes of the He (S(He)): The SF(6) (S(SF6)), and curves from the FRC test. S(N2) (VC) may be regarded as an index of overall ventilation and the difference (S(SF6) - S(He)) as an index of peripheral ventilation. Three groups were studied: CF, 28 CF patients (8-36 years of age); normal controls (NC), 33 normal nonsmokers (9-55 years of age); and a smoking group (SG), 42 non-CF smoking patients (39-79 years of age). Compared to the NC group, S(N2) (VC) is increased in the CF group, reflecting an overall ventilation impairment. There is no difference in S(N2) (VC) between the CF group and the SG group, suggesting that S(N2), though sensitive, is nonspecific. Compared to both NC and SG groups, (S(SF6) - S(He)) is decreased in the CF group, being on the average negative. This may imply that there is a peripheral impairment in the distribution of ventilation that originates in terminal and respiratory bronchioles. Negative (S(SF6) - S(He)) is statistically associated with the youngest CF patients, suggesting that terminal and respiratory bronchiolar involvement is linked to early stages of the disease. In older CF patients, (S(SF6) - S(He)) is more often positive, suggesting that even more distal airways, such as alveolar ducts, become involved in peripheral inhomogeneity of ventilation.

Adolescent↗

PubMed1989

Computer-controlled large-animal pulmonary function system.

Breath by breath determination of lung volume and specific lung conductance is challenging, yet desirable particularly when rapid changes in lung function accompany abrupt changes in lung volume. We have developed a large-animal pulmonary function data acquisition system using two personal computers with custom-made software which continuously tracks breath by breath changes in pulmonary function and lung volume. Accurate measurement of respiratory flow signals is accomplished by collecting separate pneumotachometer-derived expiratory and inspiratory flow signals, correcting them to standard temperature pressure dry (STPD) and summing them into a single flow data array. Calibration of inspiratory and expiratory flow is software corrected by comparison of the integrated flow signals with a sinusoidal pump system. Data are collected continuously for up to 120 min at 100 Hz/channel. Subroutines which configure the system to perform functional residual capacity, dosimetry and partial expiratory flow-volume maneuvers are user selected at any time during data collection.

Animals↗

PubMed1980

Intercostal muscle reflexes and sleep breathing patterns in the human infant.

Breathing variability and apnea characteristic of rapid eye movement (REM) sleep was investigated in a newborn infant with complete interruption of intercostal to phrenic neural pathways due to intrapartem transection of the cervical spinal cord. Breath-to-breath variability in inspiratory duration (TI), breath duration (Ttot), tidal volume (VT), and ventilation (VI) was significantly greater in REM than in quiet sleep and was similar to the variability in these parameters seen in normal infants. In addition, brief periods of diaphragmeatic apnea were observed during REM sleep. The phenomenon of shortened TI during airway occlusion previously attributed to intercostal-to-phrenic reflexes was examined in the quadriplegic infant and in seven healthy term infants. The frequency of this response was increased when airway occlusion was delayed until after onset of inspiration. Shortening of TI by occlusion occurred no less frequently in the quadriplegic than in the control infants. The constant paradoxical inward movement of the rib cage during inspiration observed in the quadriplegic infant suggests that supraspinal innervation of intercostal muscle limits such paradoxical movements in the normal infant. The quadriplegic infant's end-expiratory volume was consistently above his passive functional residual capacity, as inferred from respiratory volume and pressure measurements.

Birth Injuries↗

PubMed1997

Perioperative assessment of respiratory compliance and lung volume in infants with congenital diaphragmatic hernia: prediction of outcome.

BACKGROUND/PURPOSE: Infants who have congenital diaphragmatic hernia (CDH) have high mortality and morbidity. The aim of this study was to determine the relative ability of the results of serial measurements of compliance of the respiratory system (CRS) and lung volume (functional residual capacity (FRC)) to predict poor outcome: death or oxygen dependency at 28 days. In addition, the authors wished to document the evolution of any lung function abnormalities during the perioperative period. METHODS: Daily measurements of CRS and FRC were made in the first week of life and subsequently during week 2 in 16 infants who had a median gestational age of 38 weeks and birth weight of 3.2 kg. RESULTS: Seven infants had a poor outcome: five died and two others remained oxygen dependent beyond 28 days. The infants who had a poor outcome were characterized on day 1 by a significantly lower CRS, but not FRC (P < .05). In comparison with results from day 1, the median CRS of the infants overall had significantly improved only by week 2 (P < .05), there was no such significant change in FRC with increasing postnatal age. At week 2, only the CRS results differed significantly between those infants who had and who did not have poor outcome (P < .05). CONCLUSION: The results of serial measurements of CRS, rather than FRC are the more useful predictor of outcome in infants who have CDH.

Female↗

PubMed2005

Which pulmonary volume should be used in physiotherapy to obtain higher maximal inspiratory pressure in COPD patients?

BACKGROUND AND PURPOSE: Patients with chronic obstructive pulmonary disease (COPD) present pulmonary hyperinflation as the main cause of mechanical disadvantages in respiratory muscles. Measurement of the force generated by those muscles is converted into pressure changes. The aim of the present study was to evaluate the maximal inspiratory pressure (MIP) from the residual volume (RV) and from the functional residual capacity (FRC), in patients with COPD, and to determine which pulmonary volume should be used in physiotherapy so as to obtain higher MIP results. METHOD: An investigation of 18 male patients with stable COPD. Patients were examined using a manual vacuometer to measure the MIP of 20 daily manoeuvres. Ten measurements were taken from the RV and 10 from the FRC, taken alternately with an interval of 1 minute between each measurement, for five consecutive days. RESULTS: Increases in MIP were obtained from the RV measurements (mean +/- SE) from 59.7 (+/- 5.2) to 66.6 (+/- 5.3) cm H2O (F(4,64) = 3.34; p < 0.015) and from the FRC measurements, from 55.4 (+/- 4.9) to 64.4 (+/- 4,8) cm H2O (F(4,64) = 6.72; p < 0.001). Post hoc analysis showed an increase, over consecutive days, in both RV and FRC. For FRC, an increase was revealed on the second and third days, a fall was found on the fourth day and a new increase was found on the last day. MIP reached different levels, between RV and FRC, on the first (t = 2.888; p = 0.010) and fourth (t = 2.165; p = 0.045) days. CONCLUSION: In the present study, MIP reached higher levels at FRC during the five days of evaluation, and a learning effect occurred in the patients. Motor units from the respiratory muscles may have been recruited in order to perform the manoeuvres during the days of evaluation. The study suggests that there is good evidence for the use of the FRC as a parameter to find the major MIP value.

Aged↗

PubMed1981

Pulmonary function testing of animals chronically exposed to diluted diesel exhaust.

The purpose of this work was to assess the potential effect that chronic inhalation of diesel exhaust may have on lung mechanics and lung volume. Noninvasive pulmonary function tests that produced data on lung air flows and volumes have been conducted repeatedly on 25 male Fischer-344 rats exposed to diesel exhaust at a particulate concentration of 1500 micrograms m-3, 20 h per day, 5 1/2 days per week, for 612 days. The same tests were conducted on 25 clean air control animals. When the data were normalized, the majority of tests did not reveal any significant deviation from the norm for the first year of exposure. In the second year, the functional residual capacity and its component volumes - expiratory reserve and residual volume, maximum expiratory flow at 40% of vital capacity, maximum expiratory flow at 20% of vital capacity and the forced expiratory volume in 0.1 s - were significantly greater in the diesel exposed animals. The data are inconsistent with known clinically significant adverse health effects. Although the lung volume changes in the diesel exposed animals could be indicative of emphysema or other forms of chronic obstructive lung disease, this interpretation is contradicted by the air flow data which suggest simultaneous lowering of the resistance of the smaller airways. The observations are not consistent with documented clinical lung disease in man.

Aerosols↗

PubMed2004

Nitrous oxide uptake in man: a new concept of uptake of inhalation anesthetics.

BACKGROUND: With proper recognition of the functional residual capacity (FRC) and the existence of the alveolar membrane in consideration of gas uptake, the uptake of nitrous oxide does not follow the previously described power function of time, 1,000 ml x t(-1/2). METHODS: By use of a simple subtraction method, nitrous oxide uptake was measured in patients undergoing anesthesia with nitrous oxide in oxygen and a high-dose narcotic for cardiac surgery. RESULTS: When FRC washin was considered separately, the uptake of nitrous oxide which started from zero, reached its peak value at the end of washin, and then diminished slowly. CONCLUSIONS: In contrast to previous publications, in which the time course of FA/FI was used to express the uptake of nitrous oxide, in spite of the area under the curve of FA/FI should not be used to express uptake, instead, the area above the curve, (1-FA/FI), fits the results and should be considered as representing uptake.

Anesthetics, Inhalation↗

PubMed1991

Ipratropium bromide for symptomatic preterm infants.

Twelve preterm infants, median gestational age 31.5 weeks, were entered into a randomised, placebo-controlled trial of bronchodilator therapy. Their postnatal age was a median of 17.5 months and all suffered from recurrent respiratory symptoms. The infants received either inhaled placebo or 40 micrograms of ipratropium bromide (active therapy) three times a day utilising a coffee cup as a spacer device. Each therapy was administered for 2 weeks. The symptom score during the active period was reduced by 59% compared to the placebo period (P less than 0.01) and this was associated with 38% improvement in lung function in the active period compared to a 20% change in functional residual capacity over the placebo period (P less than 0.01). We conclude inhaled ipratropium bromide appears to be an effective treatment for symptomatic infants at follow up.

Birth Weight↗