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At least 127 records · Page 7Linked to original sources
PubMed2006

Monitoring of functional residual capacity by an oxygen washin/washout; technical description and evaluation.

OBJECTIVE: It was the goal of this study to develop and test an automated method for measuring functional residual capacity (FRC) by an oxygen washin/washout in intensive care settings. Such a method is required to work with conventional ventilator breathing systems and to use only medical grade sensors. METHODS: The oxygen setting on a standard intensive care ventilator is changed by at least 10%. Ventilatory pressure and flow are measured by the built-in sensors of the intensive care ventilator. Oxygen concentration is measured by a diverting medical oxygen analyzer. In order to overcome the known problem that synchrony between flow and concentration measurement is corrupted by the change of gas viscosity and by the cyclic change of airway pressure, a physical/mathematical model of the pneumatic circuit of the analyzer was developed. With this model, the change of sample flow is calculated continuously. Thus, synchrony between flow and gas concentration measurement is restored. This allows the determination of volumetric gas fluxes as needed for the FRC measurement. The setup was tested in the laboratory with a lung simulator. Simulated lung compliance, breathing frequency and tidal volume were varied. Results. The mean difference between measured and simulated FRC (range 1.7 to 5 L) was less than 1% at tidal volumes greater than 400 mL. This difference ranged from -5% to 8%, depending on simulated lung compliance and ventilator setting. The variability of consecutive measurements was about 2.5%. CONCLUSIONS: A method has been developed for reliable measurement of the FRC with an oxygen washin/washout technique. This method is sufficiently easy to use to suit for application in intensive care units. It does not require any action by the operator except a manual change of inspired oxygen concentration. Accuracy and sensitivity of the method have been proven sufficient to meet clinical and scientific requirements. Future clinical studies will reveal the applicability of the chosen procedure under clinical conditions.

Diagnosis, Computer-Assisted↗
PubMed1999

Compliance and functional residual capacity after staple versus combined staple/holmium laser lung volume reduction surgery in a rabbit emphysema model.

BACKGROUND: There is some evidence to suggest that laser exposure, when added to standard staple reduction techniques, may result in improved physiologic response to lung volume reduction surgery (LVRS). In this study, we compared physiologic responses of staple LVRS with combined staple/laser in a rabbit emphysema model. METHODS: Ninety-three New Zealand White rabbits underwent emphysema induction with aerosolized elastase 4 weeks before surgery and were killed 1 week after surgery. Treatment groups were bilateral moderate volume staple LVRS (< or =3 g, n = 39), combined moderate volume staple (< or =3 g)/holmium laser LVRS (n = 18), large-volume staple LVRS (> or =3 g, n = 27), or sham surgery (n = 9). RESULTS: Decrease in postoperative static respiratory system compliance by combined moderate-volume staple/laser treatment (1.22 cc/cm H2O) was similar to large-volume staple resection (1.40 cc/cm H2O, p = 0.39), and superior to moderate staple resection (0.82 cc/cm H2O, p = 0.01) or sham surgery (0.09 cc/cm H2O, p = 0.0001). Functional residual capacity decrease was greater after combined moderate staple/laser resection (6.46 cc) than large-volume staple resection (4.52 cc, p = 0.33), moderate-volume staple resection (4.59 cc, p = 0.43), or sham surgery (4.10 cc, p = 0.29). Perioperative mortality was highest after laser/staple LVRS (22%, 4/18). CONCLUSIONS: In this rabbit model, combined staple/ holmium laser reduction for emphysema results in significant improvement in compliance and trends toward improvement in functional residual capacity above staple reduction alone, but with higher mortality.

Animals↗
PubMed1996

The influence of sleeping position on functional residual capacity and effective pulmonary blood flow in healthy neonates.

Variation in body position has been shown to affect respiratory function in adults and neonates with and without respiratory illness. At present it remains unclear why respiratory function should be affected by different body positions. We hypothesized that the effect of body weight on the relatively compliant chest wall of the newborn infant in the prone position would cause a reduction in functional residual capacity (FRC) and a compensatory improvement in ventilation/perfusion matching as measured by effective pulmonary blood flow. To evaluate this, a paired crossover study was performed on 12 normal newborn infants. The inert gas (argon) rebreathing method adapted for neonates was used to measure FRC. Simultaneously effective pulmonary blood flow (Qpeff) was determined using Freon 22 and a mass spectrometer with computerized analysis. The babies were studied in three different positions in random order: prone, supine and right lateral decubitus. The means (95% confidence intervals) of the three groups of FRC were 23.8 (19.2 to 28.4), 23.8 (20.2 to 27.5), and 24.3 (19.5 to 29.2) ml/kg, respectively (P = 0.59) and for Qpeff were 104 (91 to 116), 108 (95 to 122), 109 (97 to 122) ml/ kg-min, respectively (P = 0.11). Thus no significant differences were demonstrated. In nine of the babies, a repeat supine measurement was taken at the end of the study to assess repeatability of the method. In these nine babies alone the results were 22.7 (19.1 to 26.3) and 22.1 (18.6 to 25.6) ml/kg for FRC, and 102 (89 to 116) and 98 (90 to 107) ml/kg-min for Qpeff. The coefficients of repeatability were 4.7 ml/kg for FRC (21%) and 30 ml/kg-min for Qpeff (30%).

Argon↗
PubMed1981

Measurement of functional residual capacity during mechanical ventilation by simultaneous exchange of two insoluble gases.

A precise method for rapid measurement of functional residual capacity (FRC) during mechanical ventilation that uses the simultaneous exchange of argon and nitrogen is described. Circuit leaks were immediately recognizable upon completion of a run, and pneumotachygraphic inaccuracies due to turbulent flows, changes in viscosity, and time delays between pneumotachygraph and mass spectrometer signals were avoided. For 166 duplicate determinations, the first measurement of FRC differed from the second by 0.5 +/- 0.5 per cent (mean +/- SE). The technique does not affect pulmonary gas exchange. During 35 consecutive determinations of FRC (with an inspired oxygen of 50 per cent), mixed expired oxygen and carbon dioxide tensions varied less than 7 and 1.5 torr, respectively.

Argon↗
PubMed1983

Postoperative nitrous oxide analgesia and the functional residual capacity.

Surgery of the upper abdomen is associated with the greatest demand for postoperative analgesia and also is marked by depressed pulmonary function, arterial hypoxemia, and pulmonary complications. Nitrous oxide (N2O) in concentrations of 15-25% is a potent analgesic and is relatively free of untoward side effects if administered for a maximum of 48 h. In the present study, the effect of N2O analgesia on postoperative lung function, in particular, the functional residual capacity (FRC), is examined. Eighteen cholecystectomy patients received either a narcotic (N = 11) or N2O (N = 7) for postoperative analgesia. N2O-treated patients had satisfactory analgesia and maintained FRC at normal levels. Narcotic treated patients had a fall of 22% in FRC. N2O had no effect on the formed elements in peripheral blood.

Cholecystectomy↗
PubMed1983

Mechanism of functional residual capacity increase in haemorrhagic shock.

Shock was elicited in anaesthetized dogs by maintaining a haemorrhagic hypotension of 4 kPa until 30 per cent spontaneous refusion, followed by total reinfusion. Functional residual capacity (FRC) and minute ventilation increased considerably similarly to our previous experiments. Lactate content in both the external intercostal and the biceps femoris muscles increased significantly in advanced shock. The expiratory external abdominal oblique muscle showed electromyographic signs of fatigue. At the height of the FRC changes tonic contraction of the external intercostal muscle could be demonstrated electron microscopically. This tonic contraction is the main factor in the large FRC rise in late shock forming the basis of a hitherto unknown vicious circle.

Abdominal Muscles↗
PubMed1981

Temporal responses of functional residual capacity and oxygen tension to changes in positive end-expiratory pressure.

PEEP is widely accepted as a therapy for some forms of acute respiratory failure (ARF). PEEP increases functional residual capacity (FRC), decreases intrapulmonary shunt fraction, and improves arterial oxygenation. The time required for FRC and arterial oxygen tension (PaO2) to stabilize after an adjustment in the level of PEEP is not clearly established. Therefore, to determine the temporal relationship between PEEP, FRC, and PaO2 after adjusting the level of PEEP, aspiration pneumonitis was produced in swine. The FRC and the PaO2 decreased within seconds after intratracheal instillation of 0.1 N HCl; FRC of all animals was restored to its control value after the application of PEEP, 5 cm H2O, but PaO2 remained low. It was necessary to increase PEEP to 20 cm H2O and FRC to twice the control value to return arterial oxygenation to control levels. After PEEP was applied, an average of 15 sec was required to increase FRC; the less compliant the lung, the more rapid the change. After PEEP was removed, FRC stabilized within an average of 22 sec. When PEEP, 25 cm H2O, was removed, arterial oxygenation decreased suddenly and substantially which suggests that PEEP, especially at higher levels, should not be discontinued, even momentarily, for nonessential maneuvers.

Animals↗
PubMed1987

Exercise-induced changes in functional residual capacity.

We used a helium-rebreathe technique in nine healthy subjects to determine the effects of exercise intensity and duration on end-expiratory lung volume (EELV). The rebreathe functional residual capacity (FRC) technique was shown: (a) to be similar to that measured in the body plethysmograph, at rest; (b) to agree closely with volitionally induced changes in EELV as determined by inductance plethysmography, at rest; (c) to be reproducible within subjects between trials conducted at rest or exercise on different days (r = 0.96, coefficient of variation +/- 3%); (d) to correlate significantly with coincident changes in end-expiratory esophageal pressure from rest to exercise, with increasing exercise intensity and over time at a constant exercise load. Exercise-induced reductions in EELV occurred in all subjects, averaging 0.3 L (-0.1 to -0.7 L) in light exercise and 0.79 L (-0.5 to -1.2 L) in heavy or maximum exercise. This reduction in EELV accounted for slightly more than one-half of the increase in VT during light exercise and slightly less than one-half of the increased VT in heavy exercise. In heavy prolonged exercise lasting 8-15 min, EELV fell in the initial 2 min and was either sustained at this reduced level or fell further with exercise duration to exhaustion. We found that FRC was reduced even in very light exercise when changes in TE and VE from rest were minimal; further reductions in EELV occurred as end-inspiratory lung volume increased and expiratory time shortened with increasing exercise intensity and duration. Based on these types of changes we speculate that active expiration during exercise in humans may be controlled by a combination of locomotor-related feed-forward and lung volume related feed-back mechanisms.

Adult↗
PubMed1994

Functional residual capacity and total respiratory system impedance in wheezing infants.

Airways obstruction has been demonstrated in acutely wheezing infants. The aim of the present study was to assess functional abnormalities as detected by measurement of total respiratory system resistance (Rrs) and functional residual capacity (FRC) in infants with a history of recurrent episodes of wheezing, while not acutely ill. In 30 such infants (mean age, 10 months; range, 4-17) and in 10 healthy infants (mean age, 6 months; range, 0-14) four Rrs measurements, performed with the forced pseudo-random noise (PRN) oscillation technique, and three FRC determinations, using the closed-circuit helium dilution technique, were averaged. A lower than predicted FRC was demonstrated in 20/30 (66%) patients. At 16 Hz, Rrs was significantly above predicted in 3/30 (10%) patients. Specific Rrs (Rrs x FRC) at 16 Hz was increased in 5/30 (17%) patients. In conclusion, the PRN oscillation technique combined with FRC measurement by helium dilution detects lung function abnormalities in a minority of wheezing infants during symptom-free intervals.

Airway Resistance↗
PubMed1981

A system to measure functional residual capacity in critically ill patients.

The use of continuous positive airway pressure (CPAP) and intermittent mandatory ventilation (IMV) in spontaneously breathing, intubated patients has prompted the development of new procedures for measuring functional residual capacity (FRC). The authors have developed a system for measuring FRC by the multiple breath nitrogen washout technique, which is suitable for use on intubated patients breathing with CPAP, IMV, or intermittent positive pressure ventilation (CONTROL) and on nonintubated patients. This system uses a pair of synchronized volume ventilators to permit a step change in inspired N2 fraction while providing therapeutic ventilatory support. A rapid-response nitrogen analyzer and a modified bellows spirometer are used for continuous measurement of airway nitrogen concentration and expired gas flow rate. FRC is calculated on-line by a digital computer. The system accuracy was tested on a mechanical lung simulator in the CPAP and CONTROL modes. The measured volume was found to agree within 58 +/- 52 ml of the actual volume in the CONTROL mode and within 104 +/- 22 ml in the CPAP mode. The system was also tested for repeatability by making duplicate FRC determinations in patients with respiratory insufficiency. In the 18 patients studied, the correlation coefficient of these duplicate measurements was r = 0.987 and the mean difference between measurements was 49 +/- 24 ml. This noninvasive system also provides data used to calculate anatomical deadspace by Fowler's method (VSDS) and uniformity of ventilation (V/V) for multicompartment lung models.

Functional Residual Capacity↗
PubMed1995

The prone positioning during general anesthesia minimally affects respiratory mechanics while improving functional residual capacity and increasing oxygen tension.

We investigated the effects of the prone position on the mechanical properties (compliance and resistance) of the total respiratory system, the lung, and the chest wall, and the functional residual capacity (FRC) and gas exchange in 17 normal, anesthetized, and paralyzed patients undergoing elective surgery. We used the esophageal balloon technique together with rapid airway occlusions during constant inspiratory flow to partition the mechanics of the respiratory system into its pulmonary and chest wall components. FRC was measured by the helium dilution technique. Measurements were taken in the supine position and after 20 min in the prone position maintaining the same respiratory pattern (tidal volume 10 mL/kg, respiratory rate 14 breaths/min, FIO2 0.4). We found that the prone position did not significantly affect the respiratory system compliance (80.9 +/- 16.6 vs 75.9 +/- 13.2 mL/cm H2O) or the lung and chest wall compliance. Respiratory resistance slightly increased in the prone position (4.8 +/- 2.5 vs 5.4 +/- 2.7 cm H2O.L-1.s,P < 0.05), mainly due to the chest wall resistance (1.3 +/- 0.6 vs 1.9 +/- 0.8 cm H2O.L-1.s, P < 0.05). Both FRC and PaO2 markedly (P < 0.01) increased from the supine to the prone position (1.9 +/- 0.6 vs 2.9 +/- 0.7 L, P < 0.01, and 160 +/- 37 vs 199 +/- 16 mm Hg, P < 0.01, respectively), whereas PaCO2 was unchanged. In conclusion, the prone position during general anesthesia does not negatively affect respiratory mechanics and improves lung volumes and oxygenation.

Adult↗
PubMed1986

The functional residual capacity of infants with respiratory distress syndrome.

Positive end-expiratory pressure (PEEP) is used in the treatment of infants with respiratory distress syndrome (RDS) to prevent atelectasis, recruit alveolar space and return the functional residual capacity (FRC) toward normal volumes. This study determined the FRC range of 15 prematurely born infants with RDS receiving PEEP. Ventilator settings were controlled clinically using predominantly results of arterial blood-gas analyses. Measurements of arterial blood-gases and FRC (N2 washout) were made during the infants' second day of life. The FRC of the infants on a PEEP of 4.5 +/- 1.3 cmH2O ranged widely from 3 to 33 ml/kg with a mean of 14.5 ml/kg; 17 +/- 2 ml/kg was considered normal. The FRC was within one SD of the mean in only three of the 15 infants (20%) and outside of two SD of normal in seven (47%). A linear regression of calculated alveolar-arterial oxygen gradient (AaDo2) with FRC yielded a correlation coefficient r = 0.825. The AaDo2 values could be used to identify six of the seven infants having FRC outside of 2SD from normal. We conclude that convential methods of PEEP selection for infants with RDS seldom result in a normalization of FRC. Calculated AaDo2 values may be used to identify most RDS infants with FRC widely divergent from normal values.

Functional Residual Capacity↗
PubMed1995

Functional residual capacity to thoracic gas volume (FRC:TGV) ratio in healthy neonates.

Gas trapping has been suggested to be common in healthy newborns in the immediate postnatal period. To determine the veracity of that finding, functional residual capacity (FRC) and thoracic gas volume (TGV) were measured in such a population and the FRC:TGV ratios were related to measurements of airway resistance (RAW). FRC was assessed by a helium gas dilution technique, TGV and RAW by plethysmography. Twenty-four healthy infants born at term were studied at a median age of 2 days (range 1-5 days). None had respiratory problems, nor had their mothers undergone invasive antenatal procedures. Their median FRC, which was 27.1 (range 23.8-32.0) ml kg-1, was significantly lower than their TGV (median 29.8, range 26-33 ml kg-1, P < 0.01). The mean 'within subject' difference between FRC and TGV was 2.5 (range 0.3-5.5) ml kg-1. The median FRC:TGV ratio was 0.93 (range 0.82-0.99). Eight infants had an FRC:TGV ratio less than 0.9, two of whom were studied on the first postnatal day. No infant with a low (< 0.9) FRC:TGV ratio had an abnormal RAW. The differences between FRC and TGV demonstrated in this study were smaller than documented in earlier series, suggesting the degree of gas trapping may previously have been over-estimated.

Airway Resistance↗
PubMed1996

Effect of apparatus on functional residual capacity.

As the route of breathing and use of airway apparatus such as mask, mouthpiece and noseclip can alter breathing pattern, this study has used the helium dilution method to estimate the effects of mouthpiece and mask breathing on functional residual capacity (FRC) in the supine position, and the change in FRC that occurs between the sitting and supine positions while breathing by mouthpiece. In 13 normal subjects, breathing by mouthpiece, FRC was smaller, by a median of 1.07 litre (interquartile values 0.73-1.43 litre) in the supine compared with the sitting position (P < 0.01), but residual volume (RV) did not change significantly. FRC measured in the supine position was significantly greater when breathing by mask than by mouthpiece (0.25, 0.04-0.38 litre) and RV was greater by similar amounts (0.20, -0.02 to 0.49 litre). This difference may result from increased inspiratory activity while breathing via the mask.

Anesthesiology↗
PubMed1982

The effect of positive end-expiratory pressure on functional residual capacity: role of prostaglandin production.

It has been shown that lung distension can generate prostaglandins. To test the hypothesis that there may be a prostaglandin-mediated peripheral (alveolar duct) bronchodilator effect contributing to the increase in functional residual capacity (FRC) observed with positive end-expiratory pressure (PEEP), we applied PEEP to 8 beagle dogs at 2, 5, 5, 7.5, and 10 cm H2O, and measured FRC at each level and immediately after cessation of PEEP. This experiment was then repeated after the intravenous administration of indomethacin 10 mg/kg. The results indicate a significant reduction of FRC (p less than 0.05) at 5, 7.5, and 10 cm PEEP after the administration of indomethacin. Furthermore, FRC initially failed to return to baseline immediately after cessation of PEEP but did so after indomethacin. We conclude that endogenous prostaglandin production of PEEP but did so after indomethacin. We conclude that endogenous prostaglandin production may be partially responsible for the elevation of FRC with PEEP.

Animals↗
PubMed2002

Exploring the relationship between forced maximal flow at functional residual capacity and parameters of forced expiration from raised lung volume in healthy infants.

The raised volume rapid thoraco-abdominal compression technique (RVRTC) is being increasingly used to assess airway function in infants, but as yet no consensus exists regarding the equipment, methods, or analysis of recorded data. The aim of this study was to explore the relationship between maximal flow at functional residual capacity (V'(maxFRC)) and parameters derived from raised lung volumes, and to address analytical aspects of the latter technique in an attempt to assist with future standardization initiatives. Forced vital capacity (FVC) from lung volume raised to 3 kPa, timed forced expiratory volumes (FEV(t)), and forced expiratory flow parameters at different percentages of expired FVC (FEF(%)) were measured in 98 healthy infants (1-69 weeks of age). V'(maxFRC) using the tidal rapid thoraco-abdominal compression (RTC) technique was also measured. The within-subject relationships and within-subject variability of the various parameters were assessed. Duration of forced expiration was < 0.5 sec in 5 infants, meaning that FEV(0.3) and FEV(0.4) were the only timed volume parameters that could be calculated in all infants during the first months of life, and even when it could be calculated, FEV(0.5) approached FVC in many of these infants. It is recommended that FEV(0.4) be routinely reported in infants less than 3 months of age. Contrary to previous reports, within subject variability of V'(maxFRC) was less than that of FEF(75) (mean CV = 6.3% and 8.9%, respectively).A more standardized protocol when analyzing data from the RVRTC would facilitate comparisons of results between centers in the future.

Crown-Rump Length↗
PubMed1999

Functional residual capacity and pulmonary mechanics in premature infants receiving a 12-day dexamethasone course.

The objective of this paper is to determine the effects of a 12-day dexamethasone course of the pulmonary function of preterm infants. The design consisted of a consecutive sample of eligible patients, before-after trial. The Regional referral center neonatal ICU was the setting. The patients were 13 preterm infants, 545-1315 g, requiring mechanical ventilation. The following was used: Intravenous dexamethasone for a 12-day tapering course beginning at 0.5 mg/kg every 12 hr. Main outcome measures were as follows: Measurements of functional residual capacity (FRC), compliance, resistance, arterial blood gases and alveolar-arterial differences, level of ventilatory assistance, weight, length. All measures of pulmonary function demonstrated significant improvement by Day 12 of treatment. Most improvement occurred in the first 6 days of treatment, in association with increased lung volume.

Anti-Inflammatory Agents↗