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Results for “Functional Residual Capacity”

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PubMed1977

The bronchodilator effects of aerosolized terbutaline. A controlled, double-blind study.

The bronchodilator effects of aerosols of a high-dose of terbutaline sulfate (1.5 mg), a low-dose of terbutaline sulfate (0.75 mg), isoproterenol (0.3 mg), and placebo were compared using forced expiratory spirometry, flow-volume curves, and body plethysmography in a double-blind, six-hour, controlled study in 25 patients with reversible airflow obstruction. After isoproterenol therapy, the values peaked at 15 minutes, and none were significantly different (P less than .05) from placebo after the 30-minute observation point. The values for high-dose terbutaline peaked at one hour at a level that exceeded responses to isoproterenol. All values except the forced vital capacity at five and six hours and functional residual capacity at six hours were significantly greater than placebo (P less than .05) at all observation points. The low-dose terbutaline values peaked earlier and at a lower value than the high-dose terbutaline values, and several indexes were significantly greater (P less than .05) than after isoproterenol therapy beyond the two-hour point.

Adolescent↗

PubMed1995

Hypoxic ventilatory response predicts the extent of maximal breath-holds in man.

To understand the factors influencing breath-holding performance, we tested whether the hypoxic (HVR) and hypercapnic ventilatory responses (HCVR) were predictors of the extent of maximal breath-holds as measured by breath-hold duration, the lowest oxyhemoglobin saturation (SpO2min), lowest calculated PaO2 (PaO2min) and highest end-tidal PCO2 (PETCO2max) reached. Steady state isocapnic HVR and hyperoxic HCVR were measured in 17 human volunteers. Breath-holds were made at total lung capacity (TLC), at TLC following hyperventilation, at functional residual capacity, and at TLC with FIO2 = 0.15. SpO2 was measured continuously by pulse oximetry, and alveolar gas was measured at the end of breath-holds by mass spectrometry. PaO2min was calculated from SpO2min and PETCO2max. HVR was a significant predictor of both SpO2min and PaO2min. HVR and forced vital capacity were predictors of breath-hold duration by multiple linear regression. HCVR had no significant predictive value. We conclude that HVR, but not HCVR, is a significant predictor of breath-holding performance.

Adult↗

PubMed1995

Central and reflex neural control of genioglossus in subjects who underwent laryngectomy.

Inspiratory activation of the genioglossus (GG) may occur by central drive or as a reflex to negative airway pressure. To distinguish between these, we studied seven laryngectomy patients who breathe via tracheal stomas. Negative pressure stimuli (-15 and -25 cmH2O for 500 ms) were applied 1) at functional residual capacity and 2) during early inspiration via (i) the upper airway (UA) and (ii) the tracheal stoma. Intraoral surface GG electromyogram was quantified, as described previously (R. L. Horner, J. A. Innes, K. Murphy, and A. Guz, J. Physiol. Lond. 436: 15-29, 1991). Phasic GG activity was also measured from an integrated electromyogram during spontaneous and inspiratory loaded breathing. Reflex GG activation occurred with negative UA pressure both at functional residual capacity and during inspiration (P < 0.001), but pressure stimuli at the stoma caused no significant activation (P = 0.07). Phasic inspiratory activation occurred in four patients at rest and in all seven patients during inspiratory loading (P < 0.02). These patients demonstrate 1) reflex activation of the GG by negative UA pressure without airflow or respiratory effort and 2) central inspiratory GG activation that is not mediated by negative airway pressure.

Aged↗

PubMed1980

Detrimental effects of removing end-expiratory pressure prior to endotracheal extubation.

Patients recovering from acute respiratory insufficiency are usually not extubated until they can ventilate adequately while breathing spontaneously at ambient end-expiratory pressure (T-tube). It is hypothesized that this period of T-tube breathing might be detrimental to gas exchange since the endotracheal tube abolishes the expiratory retard produced by the glottis and thereby inhibits the patient's ability to maintain adequate functional residual capacity (FRC). To test this hypothesis, pulmonary function of 17 patients was compared during T-tube breathing and Continuous Positive Airway Pressure (CPAP) and after extubation. Intrapulmonary shunt was higher (p less than 0.05) and arterial PO2 and FRC were lower (p less than 0.05) during T-tube breathing than during CPAP or after extubation. In contrast, shunt, PaO2 and FRC were similar during CPAP and after extubation. Furthermore, after extubation there was an increase (p less than 0.05) in mean expiratory airway pressure as compared to T-tube breathing. A comparison of patients extubated from T-tube with patients extubated from CPAP showed no difference in postextubation shunt, PaO2 or FRC. These data suggest that endotracheal intubation should be accompanied by low levels of CPAP and that patients should be extubated directly from CPAP. The practice of placing patients in T-tube prior to extubation should be abandoned as unnecessary and potentially harmful.

Adult↗

PubMed2004

Pressure-volume curve does not predict steady-state lung volume in canine lavage lung injury.

To better understand strategies for recruiting and maintaining lung volume in acute lung injury, we examined relationships between steady-state lung volume and cumulative cyclic recruitment/derecruitment volume history and the quasi-static pressure-volume curve, in an animal saline lavage lung injury model. Small-volume tidal pressure-volume loops performed after inflation from functional residual capacity demonstrated incremental, cyclic recruitment only if the peak pressure achieved exceeded the pressure at which the compliance increased (Pflex) on the pressure-volume curve, whereas loops performed after deflation from total lung capacity remained close to the envelope deflation curve. Recruitment continued to occur up to and beyond a peak inspiratory airway pressure of 40 cm H(2)O, as demonstrated by both the tidal loops and by computed tomography-derived lung volume data. Tidal-specific compliance was relatively constant across positive end-expiratory pressure levels after inflation from functional residual capacity, but peaked at moderate positive end-expiratory pressure after deflation from total lung capacity, further demonstrating the effects of volume history and providing experimental validation of the recruitment models of Hickling (AJRCCM 2001;163:69-78). These results support the interpretation of Pflex as pressure threshold for recruitment, but otherwise do not suggest a role for the pressure-volume curve in predicting steady-state lung volume.

Airway Resistance↗

PubMed1982

Pulmonary function tests in standing ponies: reproducibility and effect of vagal blockade.

Arterial blood gas tensions, pulmonary mechanics, and lung volumes were measured in 4 sedated ponies every hour for 6 hours and in 5 ponies 4 times at 2-month intervals to assess the short- and long-term reproducibility of pulmonary function measurements. Variability in blood gas tensions was small over the short- and long-term measurement periods, whereas the variability in total respiratory resistance and functional residual capacity was small over the short term but larger over the long term. The variability in tidal volume, minute ventilation, respiratory rate, and dynamic and quasistatic compliance was relatively large over the short and long term. When data from 5 ponies were pooled, significant change did not occur in any of the variables over a 6-month period. Vagal blockade increased tidal volume and decreased respiratory rate and total respiratory resistance, but arterial blood gas tensions, minute ventilation, dynamic compliance, quasistatic compliance, functional residual capacity, and lung and thoracic cage pressure-volume curves were unaffected. Total respiratory resistance decreased with increasing lung volume, with the vagus intact. After vagal blockade, the decrease in total respiratory resistance with lung volume was minimal. Dynamic compliance was frequency independent over a range of 15 to 60 breaths/min-1, suggesting that measurable inhomogeneity of peripheral time constants did not exist in our clinically normal ponies.

Animals↗

PubMed1999

Infant lung function after inhaled nitric oxide therapy for persistent pulmonary hypertension of the newborn.

Our objectives were to determine whether the use of inhaled nitric oxide (iNO) for severe persistent pulmonary hypertension of the newborn (PPHN) causes impaired lung function during infancy. We therefore performed a prospective study of lung function in 22 infants after neonatal intensive care unit (NICU) discharge who had been treated for severe persistent pulmonary hypertension of the newborn (PPHN) with (n = 15) or without (n = 7) iNO, and compared these findings in lung function to those of healthy control infants (n = 18). Five infants with interstitial lung disease (ILD) were included to assure that the pulmonary function tests (PFT) were sensitive enough to detect abnormalities of lung function in this age group. We measured passive respiratory mechanics and functional residual capacity (FRC) using a commercially available system. All data were expressed as means and standard deviation. Statistical analysis was performed by analysis of variance (ANOVA). A Bonferroni multiple comparisons test was used for variables that showed overall group differences. Twenty-two infants were studied during follow-up 4-12 months after NICU discharge. None of the infants were actuely ill, and only one infant was on 0.25 L of oxygen per minute at the time of study. We found no differences in lung function between the treatment groups (iNO + mechanical ventilation (MV), or MV alone), or between either treatment group and healthy control infants of the same age. We were able to detect significant differences in functional residual capacity adjusted for weight or height, and compliance of the respiratory system adjusted for weight or lung volume in the ILD infants compared to the healthy controls or infants who had PPHN, indicating that these PFTs were sensitive enough to determine abnormal lung function in this age group. We conclude that inhaled nitric oxide therapy for the treatment of severe PPHN does not alter lung function as determined by lung volume and passive respiratory mechanics measurements during early infancy.

Administration, Inhalation↗

PubMed1996

Ventilation with constant versus decelerating inspiratory flow in experimentally induced acute respiratory failure.

BACKGROUND: Recognition of the potential for ventilator-associated lung injury has renewed the debate on the importance of the inspiratory flow pattern. The aim of this study was to determine whether a ventilatory pattern with decelerating inspiratory flow, with the major part of the tidal volume delivered early, would increase functional residual capacity at unchanged (or even reduced) inspiratory airway pressures and improve gas exchange at different positive end-expiratory pressure levels. METHODS: Surfactant depletion was induced by repeated bronchoalveolar lavage in 13 anesthetized piglets. Decelerating and constant inspiratory flow ventilation was applied at positive end-expiratory pressure levels of 22, 17, 13, 9, and 4 cm H(2)O. Tidal volume, inspiration-to-expiration ratio, and ventilatory frequency were kept constant. Airway pressures, gas exchange, functional residual capacity (using a wash-in/washout method with sulfurhexafluoride), central hemodynamics, and extravascular lung water (using the thermo-dye-indicator dilution technique) were measured. RESULTS: Decelerating inspiratory flow yielded a lower arterial carbon dioxide tension compared to constant flow, that is, it improved alveolar ventilation. There were no differences between the flow patterns regarding end-inspiratory occlusion airway pressure, end-inspiratory lung volume, static compliance, or arterial oxygen tension. No differences were seen in hemodynamics and oxygen delivery. CONCLUSIONS: The decelerating inspiratory flow pattern increased carbon dioxide elimination, without any reduction of inspiratory airway pressure or apparent improvement in arterial oxygen tension. It remains to be established whether these differences are sufficiently pronounced to justify therapeutic consideration.

Acute Disease↗

PubMed2003

Tracking of airway and tissue mechanics during TLC maneuvers in mice.

A tracking impedance estimation technique was developed to follow the changes in total respiratory impedance (Zrs) during slow total lung capacity maneuvers in six anesthetized and mechanically ventilated BALB/c mice. Zrs was measured with the wave-tube technique and pseudorandom forced oscillations at nine frequencies between 4 and 38 Hz during inflation from a transrespiratory pressure of 0-20 cmH2O and subsequent deflation, each lasting for approximately 20 s. Zrs was averaged for 0.125 s and fitted by a model featuring airway resistance (Raw) and inertance, and tissue damping and elastance (H). Lower airway conductance (Glaw) was linearly related to volume above functional residual capacity (V) between 0 and 75-95% maximum V, with a mean slope of dGlaw/dV = 13.6 +/- 4.6 cmH2O-1. s-1. The interdependence of Raw and H was characterized by two distinct and closely linear relationships for the low- and high-volume regions, separated at approximately 40% maximum V. Comparison of Raw with the highest-frequency resistance of the total respiratory system revealed a marked volume-dependent contribution of tissue resistance to total respiratory system resistance, resulting in the overestimation of Raw by 19 +/- 8 and 163 +/- 40% at functional residual capacity and total lung capacity, respectively, whereas the lowest frequency reactance was proportional to H; these findings indicate that single-frequency resistance values may become inappropriate as surrogates of Raw when tissue impedance is changing.

Airway Resistance↗

PubMed2001

Comparison of resistance measured by the interrupter technique and by passive mechanics in sedated infants.

Airways resistance measured by the interrupter technique (Rint) requires little patient cooperation and has been successfully used in young children, but little studied in infants. The authors aimed to evaluate the measurement of Rint in infants, using a commercially available device (the MicroRint), by comparing it with an established technique to measure respiratory resistance: the single breath occlusion technique (SBT); and a measure of airflow obstruction during forced expiration. Infants <18 months old with a history of wheeze, sedated with triclofos for pulmonary function testing, had measurements taken and compared to Rint (using the MicroRint), respiratory system resistance (Rrs) by SBT, and to maximal flow at functional residual capacity (V'maxFRC). Paired data from 25 of 37 infants studied was obtained. There was a significant difference between Rint (mean 2.94+/-0.68) and Rrs (4.02+/-0.87), but the two measures were strongly correlated (r=0.7). Rint was negatively correlated with V'maxFRC (r=-0.63). Smaller infants failed to trigger the MicroRint. Interrupter resistance values in infants are significantly lower than values of respiratory system resistance obtained by passive mechanics. However, there is a strong correlation between the two measurements, as well as between resistance measured using the interrupter technique and maximal flow at functional residual capacity, which indicates that resistance measured using the interrupter technique may be a useful marker of airway obstruction in infants. There remain a number of theoretical and technical problems which require further exploration.

Airway Obstruction↗

PubMed1994

Evaluation of a technique for detection of pulmonary hemorrhage in horses, using carbon monoxide uptake.

The diffusing capacity for carbon monoxide (DLCO) and the functional residual capacity (FRC) of the lung were measured in 5 healthy Thoroughbreds before and after instillation of autologous blood into their lungs, in an attempt to develop a method to quantitate extravascular blood in the lungs of horses with exercise-induced pulmonary hemorrhage. Mean (+/- SD) baseline values of DLCO and FRC were 333.8 +/- 61.9 ml/min/mm of Hg and 21.464 +/- 4.156 L, respectively. Blood instillation resulted in decreases in DLCO and FRC. The paradoxic decrease in DLCO (we were expecting to find an increase owing to blood in the airspaces, as has been reported in people) appears to be associated with the bronchoscopic procedure and with presence of blood in the airways. We concluded that rebreathing DLCO measurements were not effective for detecting blood introduced bronchoscopically into the lungs of horses.

Animals↗

PubMed1989

Comparison of pathophysiologic changes in the lungs of calves challenge exposed with Escherichia coli-derived endotoxin and Pasteurella haemolytica, alone or in combination.

Pulmonary responses to intratracheal challenge exposure with Pasteurella haemolytica, with or without Escherichia coli-derived endotoxin, E coli endotoxin alone, or saline solution were compared in anesthetized, mechanically ventilated neonatal calves. Baseline values for dynamic compliance, total pulmonary resistance, functional residual capacity, arterial blood gas tensions, hemogram, leukogram, and systemic and pulmonary arterial pressures were recorded for each calf. After baseline data were obtained, calves were challenge exposed with logarithmic-growth phase P haemolytica organisms with or without E coli endotoxin, E coli endotoxin alone, or saline solution (0.9% NaCl). Physiologic data were obtained immediately after challenge exposure and at various intervals over the next 6 hours. Calves challenge exposed with P haemolytica alone developed sever hypoxemia, had increased alveolar-arterial oxygen difference and threefold increases in total pulmonary resistance, became hypercarbic, had decreased functional residual capacity, and developed systemic hypotension without change in pulmonary arterial pressure. At necropsy, these calves had extensive multifocal areas of necrohemorrhagic and purulent pneumonia. Ratio of extravascular lung water to lung dry weight was not significantly increased in lung specimens obtained from calves challenge exposed with P haemolytica, but ratio of lung wet weight to dry weight was increased, indicating that increased lung wet weight was attributable largely to increased solids and not to fluid alone. (Extravascular lung water measurement excludes fluid from the vascular compartment.) Intratracheal challenge exposure with endotoxin failed to alter lung function and caused minor changes in lung structure consisting of focal areas of hemorrhage and edema.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Effect of passive smoking on the lung of young lambs.

The effect of passive smoking on lung histology, lung mechanics, and airway responsiveness (AR) was studied in 2-month-old lambs. Two groups of lambs were studied; 17 were exposed to cigarette smoke (CS) and 13 served as age- and sex-matched controls. Starting at 1 month of age, CS lambs had 25 daily exposures to the smoke generated from eight cigarettes. A smoking machine was constructed for the study using a Bird Ventilator. Two days prior to lung function testing, lambs were anesthetized and a Silastic balloon was placed in the pleural space for later measurement of pleural pressure. At the beginning of each study, lambs were intubated with a nasotracheal tube over a flexible fiberoptic bronchoscope. Lung mechanics (dynamic compliance, resistance of the lung, functional residual capacity) and AR were measured using a whole body plethsymograph. AR to inhaled histamine, carbachol, and citric acid was measured in each lamb on 3 separate days by giving five breaths of increasing concentrations of the aerosol in a noncumulative fashion. AR was measured both within 24 h of the final exposure to CS and at 3-7 days after CS. After the final AR was measured, lambs were anesthetized and an open lung biopsy performed. Control lambs had the same studies as CS lambs performed at an equivalent age. After 25 daily exposures to CS in 17 lambs, mean dynamic compliance was 0.024 +/- 0.009 liter/cm H2O, lung resistance was 2.56 +/- 1.32 cm H2O X liter-1 X s, and functional residual capacity was 0.725 +/- 0.234 liter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1971

Regional lung function in patients with hepatic cirrhosis.

The lung volume at which the dependent lung zones begin to trap gas as a result of airway closure (i.e., the "closing volume") was measured with (133)Xe in 10 seated patients with hepatic cirrhosis. In all of them the closing volume was increased above normal, and in eight it was greater than the functional residual capacity, indicating the presence of airway closure and gas trapping during resting tidal volume breathing. Direct measurements made with (133)Xe in five cirrhotic patients (a) confirmed the presence of increased gas trapping in the lower lung zones both at residual volume and at functional residual capacity, and (b) indicated that in liver cirrhosis the ventilation-perfusion ratio of the dependent lung zones may be very low, primarily as a result of decreased ventilation due to airway closure. It is concluded that in hepatic cirrhosis, gas trapping in the dependent lung zones may be an important cause of impaired gas exchange within the lungs. It is suggested that the premature airway closure observed in this disease may be due to mechanical compression of small airways by dilated blood vessels and/or interstitial pulmonary edema.

Adolescent↗

PubMed1978

Arterial oxygenation during artificial ventilation. The effect of airway closure and of its prevention by positive end-expiratory pressure.

Airway closure and arterial blood gases were measured in 11 healthy subjects both before and during anaesthesia with artificial ventilation, prior to routine surgery. The functional residual capacity was then increased by positive end-expiratory pressure (PEEP), so that ventilation took place at a lung volume where no airway closure was present, and the effect on arterial oxygenation was again investigated. A significant increase in alveolar-arterial oxygen gradient occurred in the group of seven patients in whom airway closure within a tidal breath could be demonstrated during anaesthesia, but there was no significant change in the four patients in whom airway closure could not be demonstrated. There was no improvement in arterial oxygenation on increasing functional residual capacity (FRC) in either group. It may well be that this failure to improve oxygenation was due to a deleterious effect of PEEP on the circulation, even though the PEEP was the minimum required to abolish airway closure.

Adult↗

PubMed1993

Comparison of thoracoabdominal calibration methods in normal human subjects.

In 19 normal subjects in the supine posture, we compared accuracy and precision of calibration methods that utilized different ranges of tidal volumes and thoracoabdominal partitioning: spontaneous quiet breathing (QB), isovolume maneuvers, and voluntary efforts to breathe with variable tidal volume and thoracoabdominal partitioning. Thoracic and abdominal movements were measured with the respiratory area fluxometer. Calibration methods utilizing one or more types of respiratory efforts were applied to three measurement situations: QB, variable breathing (volume and thoracoabdominal partitioning), and simulated obstructive apnea (isovolume efforts). Qualitative diagnostic calibration (QDC) included QB data only. The isovolume method (ISOCAL) included isovolumetric efforts at end expiration (functional residual capacity) and QB. Multilinear regression analyses were performed on data sets that included 1) voluntary efforts to breathe with variable volume and thoracoabdominal partitioning (CAL 1), 2) QB in addition to variable volume and partitioning (CAL 2), and 3) isovolume maneuvers in addition to QB and variable volume and partitioning efforts (CAL 3). When calibration data included a wide range of tidal volume, variable thoracoabdominal partitioning, and isovolume efforts (CAL 3), a stable calibration with small bias and scatter during all respiratory patterns was obtained. Excluding isovolume maneuvers (CAL 2) and QB (CAL 1) did not diminish accuracy. Limiting data to isovolume efforts at functional residual capacity plus QB (ISO-CAL) caused a significant increase in scatter during variable breathing patterns. Limiting calibration data to that portion of QB with small variation in the uncalibrated sum of thoracic and abdominal movements (QDC) caused significant increases in scatter in both isovolume efforts and variable breathing.

Abdomen↗

PubMed1994

Oxygen and 99mTc-MAA shunt estimations in patients with pulmonary arteriovenous malformations: effects of changes in posture and lung volume.

BACKGROUND: Patients with arteriovenous malformations are routinely monitored with arterial oxygen saturation (SaO2) estimations (breathing air) from which an oxygen shunt fraction can be calculated. This simple estimation has been compared with an anatomically defined estimate of the right to left shunt using a radioisotopic method. The fall in SaO2 which occurs in patients with pulmonary arteriovenous malformations in the erect posture and at high lung volumes was used to test the ability of SaO2 alone to follow changes in right to left shunt. METHODS: Radiolabelled albumin macroaggregates (99mTc-MAA) or microspheres (MS) were injected intravenously and kidneys and lungs were imaged. The shunt fraction (QS/QTTc) in the supine position at functional residual capacity (baseline) was obtained by quantifying right kidney radioactivity. On standing or while breath holding at total lung capacity, shunt fraction was calculated from baseline QS/QTTc and from lung counts and the injected dose. Arterial oxygen saturation (SaO2) was recorded by a pulse oximeter for calculation of the oxygen shunt (QS/QTO2) (breathing air). RESULTS: In the postural study (n = 8) SaO2 decreased from a mean (SD) value of 89 (5)% supine to 80 (6)% erect, corresponding to QS/QTO2 28 (8)% and 44 (8)% respectively. QS/QTTc increased from 28.7 (10.3)% to 39 (14.3)%. In the lung volume study (n = 8) QS/QTTc increased from 16.6 (11.5)% at functional residual capacity to 23.3 (11.9)% at total lung capacity while QS/QTO2 increased from 19.5 (7.5)% to 25.9 (10.6)% respectively. When all measurements were compared for QS/QTTc% and QS/QTO2% (n = 32) the difference in the mean values was 2.5% (absolute) and the limits of agreement between the two methods were +38% to -18% (relative). In neither the postural nor the volume study did delta (QS/QTO2) reliably predict delta (QS/QTTc)%. CONCLUSIONS: In pulmonary arteriovenous malformations the simple physiological shunt calculated from SaO2 breathing air agreed well with the anatomical right to left shunt measured with 99mTc-MAA, but predicted poorly the changes in anatomical shunt induced by postural or lung volume changes.

Adult↗

PubMed1997

Population based standards for pulmonary function in non-smoking adults in Singapore.

Ethnic differences in lung function are well recognized, hence the use of normative data should therefore be based on reference equations that are derived specifically for different ethnic groups. We have collected data (n = 406) for population-based reference values of lung function from randomly selected samples of healthy non-smoking adults of both gender (aged 20-79 years) for each of the three major ethnic groups (Chinese, Malay and Indians) in Singapore. Lung function forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC, diffusion capacity (transfer factor) for carbon monoxide (DLCO), total lung capacity (TLC), residual volume (RV), RV/TLC and functional residual capacity (FRC) was measured using standardization procedures and acceptability criteria recommended by the American Thoracic Society. Lung function values were predicted from age, height, weight, body mass index (BMI) and transformed variables of these anthropometric measures, using multiple regression techniques. Ethnic differences were demonstrated, with Chinese having the largest lung volumes and flow rates, and Indians the smallest. These prediction equations provide improved and additional (TLC, RV, RV/TLC, FRC) population-based reference values for assessment of pulmonary health and disease in Singapore.

Adult↗