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Results for “Functional Residual Capacity”

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PubMed1993

Comparison of mask and nasal continuous positive airway pressure after extubation and mechanical ventilation.

OBJECTIVE: To examine the effects of continuous positive airway pressure applied via face masks and nose masks on the change in functional residual capacity and gas exchange. DESIGN: Descriptive and prospective study. SETTING: Intensive care unit of a university hospital. PATIENTS: Ten patients with acute lung injury who had required mechanical ventilation. INTERVENTIONS: Continuous positive airway pressure at a level of 10 cm H2O applied in random order via face and nose masks. MEASUREMENTS AND MAIN RESULTS: Both continuous positive airway pressure methods resulted in an almost identical increase of functional residual capacity. During nasal continuous positive airway pressure, the increase in functional residual capacity was 294 +/- 82 mL. During mask continuous positive airway pressure, the increase in functional residual capacity was 290 +/- 85 mL. PaO2 increased and the alveolar-arterial oxygen tension/alveolar oxygen tension quotient decreased significantly during mask continuous positive airway pressure and nasal continuous positive airway pressure at a level of 10 cm H2O. Two patients showed a periodic change in their breathing patterns; they took a few breaths at an increased lung volume, followed by one deep expiration caused by mouth opening. Change in mask pressure was negligible in these two patients. Using a visual analog scale (10 = highly comfortable; 0 = severely uncomfortable), the patients rated nasal continuous positive airway pressure (8.6 +/- 0.9) significantly more comfortable than mask continuous positive airway pressure (2.6 +/- 0.8). CONCLUSION: The major advantages of continuous positive airway pressure (the improvement of functional residual capacity and oxygen transfer) can also be achieved with nasal continuous positive airway pressure in the postextubation period in patients who have been mechanically ventilated for acute lung injury.

Acute Disease↗

PubMed1988

Changes in ventilation homogeneity from preschool through young adulthood as determined by moment analysis of nitrogen washout.

This study was designed to assess potential differences in ventilation homogeneity related to growth. One hundred thirty-three healthy subjects representing four stages of growth were studied: group 1, preschool, ages 34-74 months; group 2, preadolescent, ages 8-10 yr; group 3, postpubertal, ages 15-17 yr; group 4, young adult, ages 26-40 yr. Ventilation homogeneity was assessed by moment analysis of multibreath nitrogen washout with functional residual capacity, the ratio of the 1st to 0th moment (MR 1/0), and the ratio of the 2nd to 0th moment (MR 2/0) being the outcome variables of interest. Across the four groups functional residual capacity increased as a curvilinear function of height. At all heights functional residual capacity was larger in males than females and the slope of the regression was steeper in males than females (p less than 0.001). Both MRs 1/0 and 2/0 were significantly higher in group 1 than the other groups, indicating that ventilation washout was less homogeneous in the preschool subjects than in older children or adults. Males of group 1 had significantly higher values for both moment ratios (more ventilation nonuniformity) than females. In the other groups there were no significant sex based differences although there was a trend for males to have a lower MR 1/0 than females in the young adults, p = 0.08. The results indicate that both age and sex are important determinants of the growth of distribution of ventilation.

Adolescent↗

PubMed1977

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↗

PubMed1991

Endotracheal resuscitation of neonates using a rebreathing bag.

Thirty asphyxiated neonates were resuscitated endotracheally with an anaesthetic rebreathing bag. The system was not limited either by pressure or by volume and chest movement was used as the criterion for adequate inflation. Inflation pressure and flow were recorded during resuscitation, and flow was integrated to obtain volume. Median mean pressure over the first 10 inflations was 40 cm H2O and this dropped during later resuscitation to 29 cm H2O. The volume delivered did not change significantly, so volume divided by pressure increased from a median of 0.18 to 0.35 ml/kg/cm H2O. Fourteen infants formed part of their functional residual capacity with artificial ventilation and five with spontaneous breaths. Eleven infants showed no evidence of functional residual capacity formation. In the 22 preterm infants there was a strong association between absence of functional residual capacity formation and later hyaline membrane disease that required ventilation. We suggest that pressures of more than than 30 cm H2O may be helpful during initial resuscitation and that there should be further study of devices using positive end expiratory pressure for resuscitation of preterm infants.

Anesthesia, Closed-Circuit↗

PubMed1993

Effect of lung volume on lung resistance and elastance in awake subjects measured during sinusoidal forcing.

BACKGROUND: Although lung volume may be changed by certain procedures during anesthesia and mechanical ventilation, dependence of the dynamic mechanical properties of the lungs on lung volume are not clear. Based on studies in dogs, the authors hypothesized that changes in lung mechanics caused by anesthesia in healthy humans could be accounted for by immediate changes in lung volume and that lung resistance will not be decreased by positive end-expiratory airway pressure if tidal volume and respiratory frequency are in the normal ranges. METHODS: Lung resistance and dynamic lung elastance were measured in six healthy, relaxed, seated subjects during sinusoidal volume oscillations at the mouth (5 mL/kg; 0.4 Hz) delivered at mean airway pressure from -9 to +25 cmH2O. Changes in lung volume from functional residual capacity were measured with inductance plethysmographic belts. RESULTS: Decreases in mean mean airway pressure that caused decreases in lung volume from functional residual capacity comparable to those typically observed during anesthesia were associated with significant increases in both dynamic lung elastance and lung resistance. Increases in mean mean airway pressure that caused increases in lung volume from functional residual capacity did not increase lung resistance and increased dynamic lung elastance only above about 15 cmH2O. CONCLUSIONS: Increases in dynamic lung elastance and lung resistance with anesthesia can be explained by the accompanying, acute decreases in lung volume, although other factors may be involved. Increasing lung volume by increasing mean airway pressure with positive end-expiratory pressure will decrease lung resistance only if the original lung volume is low compared to awake, seated functional residual capacity.

Adult↗

PubMed1993

Forced expiratory flows and lung volumes in normal infants.

Forced expiratory flows at functional residual capacity (VmaxFRC) by the rapid compression technique and functional residual capacity (FRC) by the helium dilution technique were assessed in 112 normal infants with a mean age of 10.7 months (range, 1.0-31.0). In predicting FRC, log transformation was appropriate and body length was the best predicator. For VmaxFRC, age was a better predictor than length, and logarithmic transformation was not required. In(FRC) = -5.465 + 2.49 x In(length) SD = 0.178; r2 = 0.83 VmaxFRC = -397 + 9.36 x (age) SD = 88; r2 = 0.52 There were no gender differences for FRC or VmaxFRC; however, male infants exposed to passive cigarette smoke tended to have lower flows than male infants not exposed (P < 0.07). This study establishes normative values for VmaxFRC and FRC in infants between 1 and 31 months of age, and suggests that passive cigarette smoke exposure has an adverse effect upon forced expiratory flows in male infants.

Age Factors↗

PubMed1993

Pulmonary function tests in cirrhotic and non-cirrhotic portal hypertension.

OBJECTIVE: To determine pulmonary functions in portal hypertension of different etiologies and with various grades of ascites. SETTING: Gastrointestinal clinic in a large community based and secondary referral hospital. PATIENTS AND METHODS: Forty five patients with portal hypertension, including 19 cirrhotics with tense ascites, 8 with moderate ascites, 6 with no ascites and 12 patients with non-cirrhotic portal hypertension. All patients underwent basal pulmonary function testing by spirometry and helium dilution technique, and arterial blood gas estimation and measurement of ascitic fluid pressure. Patients with tense ascites underwent paracentesis of up to 2 liters following which ascitic fluid pressure and pulmonary functions were estimated again. MAIN RESULTS: In cirrhotic patients without ascites, FVC (forced vital capacity), RV (residual volume), TLC (total lung capacity) and FRC (functional residual capacity) were lower than predicted values. In patients with ascites, FVC, FEV1 (forced expired volume in one second) and FEF25-75 (forced expired volume in one second) and FEF25-75 (forced expiratory flow rate between 25% and 75% of forced vital capacity) were significantly lower as compared to predicted values. FVC, FEV1, FEF25-75, pO2, pCO2 and SaO2% decreased significantly with increasing ascites. Paracentesis in patients with tense ascites led to clinical improvement and significantly improved lung volumes. CONCLUSIONS: Pulmonary functions are impaired in patients with cirrhosis, and ascites causes further deterioration. Patients with non-cirrhotic portal hypertension have normal pulmonary functions.

Adult↗

PubMed2002

Specific compliance and gas exchange during high-frequency oscillatory ventilation.

OBJECTIVES: To evaluate the use of specific compliance (static compliance/functional residual capacity) to adjust mean airway pressure, resulting in optimal gas exchange during high-frequency oscillatory ventilation in a surfactant-deficient newborn piglet. DESIGN: Prospective controlled animal study. SETTING: Laboratory. SUBJECTS: Eight newborn piglets at 5 days of age. BACKGROUND: High-frequency oscillatory ventilation enables the use of relatively high mean airway pressures without the lung damage associated with conventional positive pressure ventilation. Mean airway pressures can be increased, resulting in static lung expansion that approaches total lung capacity with its negative impact on venous return. Therefore, knowledge of lung volume is important for safe patient management. A simple, noninvasive technique to enable the clinician to determine the optimal mean airway pressure likely would improve patient management. INTERVENTIONS: The lungs were lavaged after placement of central catheters and tracheostomy to lower respiratory system compliance and worsen ventilation perfusion matching. The animals were ventilated with high-frequency oscillatory ventilation at the same mean airway pressure as before lung lavage. Mean airway pressures then were increased in a step-wise fashion up to 30 cm H2O or until clinical deterioration occurred. All other ventilator variables, Fio2, frequency, and pressure amplitude were constant throughout the experiment. MEASUREMENTS AND MAIN RESULTS: Before lavage and at each level of mean airway pressure after lung lavage, respiratory system compliance and functional residual capacity were measured. Additionally, central arterial pressure, central venous pressure, heart rate, arterial blood gas, and pulse oximetric saturation were recorded. Lung lavage significantly lowered respiratory system compliance (static as well as specific compliance) and worsened ventilation perfusion matching as evidenced by an increase in Paco2 and a decreased arterial to alveolar oxygen ratio. With increasing mean airway pressures, static/specific compliance improved and then peaked before declining, functional residual capacity increased, and blood gas improved until reaching the flat portion of the pressure-volume relationship of the lung. Optimal gas exchange as reflected by the highest arterial to alveolar oxygen ratio and lowest Paco2 at constant ventilation was found at a mean airway pressure that maintained the functional residual capacity and static respiratory system compliance at the same level as the preinjury levels ("normalized" functional residual capacity and respiratory system compliance). CONCLUSIONS: These results suggest that specific compliance measurement that incorporates static respiratory system compliance and functional residual capacity during high-frequency oscillatory ventilation can be used to adjust mean airway pressure and achieve "normalized" functional residual capacity, static compliance, and gas exchange. These measurements may provide a simple method to optimize lung volume in a surfactant-deficient patient during high-frequency oscillatory ventilation.

Animals↗

PubMed1977

Comparison of the effects of continuous negative external chest pressure and positive end-expiratory pressure on cardiac index in dogs.

Continuous negative external chest pressure was used to increase the functional residual capacity in 6 dogs, and the effects were compared with the effects of increasing functional residual capacity using positive end-expiratory pressure. Cardiac index and mixed venous O2 stauration each decreased from control values during positive end-expiratory pressure, but did not decrease with continuous negative external chest pressure. Continuous negative external chest pressure may provide an alternative to positive end-expiratory pressure for increasing the functional residual capacity of patients in whom the latter causes unacceptable decreases in venous return and cardiac output.

Animals↗

PubMed1998

Influence of acute lung volume change on contractile properties of human diaphragm.

The effect of stimulus frequency on the in vivo pressure generating capacity of the human diaphragm is unknown at lung volumes other than functional residual capacity. The transdiaphragmatic pressure (Pdi) produced by a pair of phrenic nerve stimuli may be viewed as the sum of the Pdi elicited by the first (T1 Pdi) and second (T2 Pdi) stimuli. We used bilateral anterior supramaximal magnetic phrenic nerve stimulation and a digital subtraction technique to obtain the T2 Pdi at interstimulus intervals of 999, 100, 50, 33, and 10 ms in eight normal subjects at lung volumes between residual volume and total lung capacity. The reduction in T2 Pdi that we observed as lung volume increased was greatest at long interstimulus intervals, whereas the T2 Pdi obtained with short interstimulus intervals remained relatively stable over the 50% of vital capacity around functional residual capacity. For all interstimulus intervals, the total pressure produced by the pair decreased as a function of increasing lung volume. These data demonstrate that, in the human diaphragm, hyperinflation has a disproportionately severe effect on the summation of pressure responses elicited by low-frequency stimulations; this effect is distinct from and additional to the known length-tension relationship.

Adult↗

PubMed1993

Lung function in children and adolescents with tetralogy of Fallot after intracardiac repair.

We studied lung function in 41 patients, aged 6-27 years, 1-5 years after intracardiac surgical repair (ICR) of tetralogy of Fallot (TOF) and about 5 years after the establishment of the Pediatric Cardiac Center in Prague. The measurements included vital capacity (VC), total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV), forced expiratory flows (FEF), specific airway conductance (SGaw), lung recoil pressure (Pst), and specific static lung compliance (SC1st). Single or multiple abnormal lung function parameters were found in 83% of patients. Lung function was not related to shunting operations prior to ICR, hemoglobin concentration, and hematocrit, and had no specific pattern. Pst at 100% TLC and 90% TLC declined with increasing age at ICR and at lung function testing, while SC1st rose, as did the ratio FRC/TLC. Fifteen patients were studied before and after surgery. Single or multiple lung function tests were abnormal in 93% before and in 84% after ICR. After ICR the ratios FRC/TLC and also RV/TLC, FEF at 25% VC, and FEF at 60% TLC were less frequently abnormal, while Pst at 100% TLC and at 90% TLC, as well as SGaw and TLC, were more frequently abnormal after ICR. The results indicated a regression of smaller airway obstruction and lung hyperinflation after ICR. The evolution of abnormally compliant (emphysematous) lungs with growth of the patients might be a sign of permanent sequelae of early lung damage from abnormal pulmonary hemodynamics.

Adolescent↗

PubMed2001

Effects of vagal denervation on cardiorespiratory and behavioral responses in the newborn lamb.

Recently, Wong et al. (Wong KA, Bano A, Rigaux A, Wang B, Bharadwaj B, Schurch S, Green F, Remmers JE, and Hasan SU, J Appl Physiol 85: 849-859, 1998) demonstrated that fetal lambs that have undergone vagal denervation prenatally do not establish adequate alveolar ventilation shortly after birth. In their study, however, vagal denervation was performed prenatally and the deleterious effects of vagal denervation on breathing patterns and gas exchange could have resulted from the prenatal actions of the neurotomy. To quantify the relative roles of pre- vs. postnatal vagal denervation on control of breathing, we studied 14 newborn lambs; 6 were sham operated, and 8 were vagally denervated below the origin of the recurrent laryngeal nerve. Postoperatively, all denervated animals became hypoxemic and seven of eight succumbed to respiratory failure. In vagally denervated lambs, expiratory time increased, whereas respiratory rate, minute ventilation, and lung compliance decreased compared with the sham-operated animals. In the early postoperative period, the frequency of augmented breaths was lower but gradually increased over time in the denervated vs. sham-operated group. The dynamic functional residual capacity was significantly higher than the passive functional residual capacity among the sham-operated group compared with the denervated group. No significant differences were observed in the prevalence of various sleep states and in the amount of total phospholipids or large- and small-aggregate surfactants between the two groups. We provide new evidence indicating that intrauterine actions of denervation are not required to explain the effects of vagal denervation on postnatal survival. Our data suggest that vagal input is critical in the maintenance of normal breathing patterns, end-expiratory lung volume, and gas exchange during the early neonatal period.

Animals↗

PubMed1995

Perfluorochemical liquid ventilation: from the animal laboratory to the intensive care unit.

Perfluorochemical or perfluorocarbon liquids have an enormous gas-carrying capacity. During tidal liquid ventilation the respiratory medium of both functional residual capacity and tidal volume is replaced by neat perfluorocarbon liquid. Tidal liquid ventilation is characterized by convective and diffusive limitations, but offers the advantage of preserved functional residual capacity, high compliance and improved ventilation-perfusion matching. During partial liquid ventilation only the functional residual capacity is replaced by perfluorocarbon liquid. Both tidal and partial liquid ventilation improve gas exchange and lung mechanics in hyaline membrane disease, adult respiratory distress models and meconium aspiration. Compared to gas ventilation, there is less histologic evidence of barotrauma after liquid ventilation. Cardio-pulmonary interaction, inherent to the high density of liquid, and long term safety need further study. However, extrapolating from animal data, and taking into account promising human pilot studies, liquid ventilation has the desired properties to occupy an important place in the therapy of restrictive lung disease in man.

Animals↗

PubMed2003

Effects of bracing on lung function in idiopathic juvenile kyphosis.

Although considerable information is available on the effects of bracing on lung function in kyphoscoliosis, there is a paucity of data on idiopathic juvenile kyphosis (IJK). The present study was designed to investigate the immediate effect of bracing on lung function in children and adolescents with mild-to-moderate IJK. Spirometry, measurement of lung volumes, and arterial oxyhemoglobin saturation (SaO(2)) were performed in 24 patients, 9-17 years of age, who were treated with a corrective brace for mild-to-moderate IJK (Cobb angle, 46-75 degrees ). Children were studied when braced and unbraced. When children were unbraced, mean percent predicted values (+/-standard deviation) for total lung capacity (TLC), vital capacity (VC), functional residual capacity (FRC), and forced expiratory volume in 1 sec (FEV(1)) were 100.0% (+/-13.0%), 92.7% (+/-14.2%), 108.2% (+/-20.4%), and 95.0% (+/-16.3%), respectively. With the brace on, significant reductions occurred in all lung function measurements: TLC decreased by 9.5% (P < 0.001), VC by 9.3% (P = 0.001), FRC by 14.2% (P = 0.005), and FEV(1) by 8.9% (P = 0.009). SaO(2) decreased from 96.2% (+/-1.6%) to 95.2% (+/-1.4%) (P = 0.027). An inverse relationship was observed between pre- and postbracing change in TLC and Cobb angle children (P = 0.021). Our findings indicate that corrective bracing in mild-to-moderate IJK results in mild lung restriction and a clinically insignificant drop in SaO(2). The effect of bracing on TLC decreases as the severity of kyphosis increases in these patients.

Adolescent↗

PubMed1986

Accuracy of radiographic lung volume using new equations derived from computed tomography.

This study compared radiographic measurements of regional lung volume with corresponding physiologic measurements. The database included 48 normal, supine adults who had previously undergone spirometry and helium-dilution lung volume measurements to determine physiologic functional residual capacity (G-FRC) and total lung capacity (G-TLC). Chest x-rays had also been obtained for these subjects at functional residual capacity and total lung capacity. To calculate radiographic lung volumes at functional residual capacity and total lung capacity (R-FRC and R-TLC, respectively), we traced the lung outline from the chest x-ray, and digitized each outline. We then calculated total and regional lung volumes, using equations previously derived from computed tomographic scans. R-FRC and R-TLC were closely correlated (r = 0.973, maximum SEE 6.8%) with G-FRC and G-TLC, whether or not separate equations were used for regions below the diaphragm. Using only maximum anteroposterior diameter reduced the r-value to 0.957 (SEE 9.6%). The accuracy of our method of radiographic measurement of regional lung volume was validated by the concurrence between the physiologic and radiographic measurements.

Adult↗

PubMed2001

Lung recruitment at birth does not improve lung function in immature lambs receiving surfactant.

BACKGROUND: In mature animals with surfactant deficiency induced by lung lavage, the therapeutic effect of exogenous surfactant is enhanced by a lung recruitment maneuver. We then tested whether a lung recruitment maneuver at birth immediately before surfactant treatment would improve lung function also in preterm lambs with surfactant deficiency due to immaturity. METHODS: Ten newborn lambs with a gestational age of 127 days were randomized to receive surfactant either before the first breath or immediately after a lung recruitment maneuver consisting of five sustained inflations of 8, 16 or 32 ml/kg. Functional residual capacity was measured by sulfur hexafluoride washout, and inspiratory capacity as well as maximal compliance were obtained from a static expiratory pressure-volume curve after the lungs had been inflated to 35 cm H2O. In addition, blood gases were obtained. Measurements were made at 15, 45, 175, 135, 170 and 230 min after birth. Post mortem histological examinations of the lungs were performed in a blinded fashion. RESULTS: The lung recruitment maneuvers did not improve oxygenation. Inspiratory capacity, static compliance and functional residual capacity at 4 h, as well as post mortem intrapulmonary air volume, had an inverse relation to the size of inflations given at birth. There was also a negative correlation between size of inflations at birth and response to surfactant therapy, as assessed by lung microscopy. CONCLUSION: Lung recruitment at birth does not improve the response to surfactant in immature lambs, but may instead have an adverse effect on lung function and morphology.

Animals↗

PubMed1997

Long-term pulmonary sequelae after treatment of childhood Hodgkin's disease.

BACKGROUND: Pulmonary sequelae have been reported in patients treated for Hodgkin's disease (HD). Few data are available about patients treated for childhood HD followed over several years. PATIENTS AND METHODS: In a cross-sectional study carried out for 76 months (median time) after treatment completion, we evaluated the lung function abnormalities and respiratory symptoms in 27 patients (16 males and 11 females) with HD diagnosed between 1983 and 1994 (median age at diagnosis 11 years, range 2-16 years). They had been treated with chemotherapy and radiotherapy according to current protocol AIEOP-MH 83 (n = 14) or AIEOP-MH 89 (n = 13). At the time of the study, 26 patients were in first complete remission and one in second remission. Of the 27 patients, 19 had had mediastinal irradiation at a dose of 20 Gy (n = 5) or 20.8-44 Gy (n = 14). Forced vital capacity (FVC), functional residual capacity (FRC), forced expiratory volume in one second (FEV1), FEV1/FVC ratio, and maximal expiratory flow at 25% of FVC were registered; diffusion capacity for carbon monoxide (DLCO) was determined. Data were expressed as standard deviation (SD) score. Four patterns of respiratory function abnormalities were defined: restrictive, obstructive, isolated bronchiolar impairment, isolated diffusing impairment. RESULTS: Twelve patients (44%) were asymptomatic and showed completely normal pulmonary function tests. Three patients reported dyspnea on exertion, and one of them also cough and phelgm: out of these symptomatic subjects, only 1 had functional abnormality (isolated DLCO impairment). A restrictive pattern was found in 5 patients (18%), including 2 who also had a pathological DLCO SD score. Eight additional patients (30%) had isolated diffusing impairment. Oxygen saturation was normal in all patients. Forty-seven percent of patients with normal DLCO had had lower dose irradiation (20 Gy) compared to 10% of patients with impaired DLCO (P = 0.054). Similarly, patients with normal DLCO had had significantly less chemotherapy as compared to patients with abnormal DLCO (P = 0.003). Occurrence of lung abnormalities was not significantly associated with sex, age at treatment, mediastinal irradiation, and time elapsed from treatment completion. CONCLUSION: Adolescents and young adults treated for childhood HD are at risk for lung function abnormalities, significantly more frequent in patients who received more intense treatment, as mediastinal irradiation at a higher dose (> 20 Gy) and more chemotherapy blocks. Long-term follow-up should be offered to these patients because of their possible limited potential for pulmonary function and possible lesser resistance to adverse agents such as smoke, pollution, infections and aging.

Adolescent↗

PubMed2000

Moment ratio analysis of multiple breath nitrogen washout in infants with lung disease.

Measurement of lung volumes at end expiratory level and assessment of ventilation inhomogeneity is important for respiratory management in infants with lung disease. This study compared multiple breath nitrogen washout was compared with body plethysmography to measure functional residual capacity in infants and assessed ventilation inhomogeneity using mean dilution numbers and alveolar based gas dilution numbers. Measurements were performed in 23 infants with lung disorders, eleven had wheezing bronchitis, four bronchopulmonary disease, and eight cystic fibrosis. Mean age was 11.2+/-5.8 months. Functional residual capacity of nitrogen washout (29.8+/-11.4 mL x kg(-1)) was significantly (p<0.05) lower than the plethysmographically measured functional residual capacity (40.3+/-11.4 mL x kg(-1)). Tidal volumes before nitrogen washout (90.4+/-35.1 mL) were significantly larger than at the end of the washout (72.2+/-26.9 mL). Alveolar based gas dilution numbers (6.7+/-2.3) were significantly lower (p<0.001) than mean dilution numbers (10+/-5.7). Functional residual capacity determination by nitrogen washout and plethysmography in infants with lung disease showed evidence of air trapping and ventilation inhomogeneity. Ventilation inhomogeneities are best described by alveolar based dilution numbers, since rebreathing of 100% oxygen changes ventilation pattern.

Breath Tests↗