Differences In Functional Residual Capacity Research Articles

Signal-correction errors in the EasyOne Pro LAB multiple-breath washout device significantly impact outcomes in children and adults.

Multiple-breath washout (MBW) is an established technique to assess functional residual capacity (FRC) and ventilation inhomogeneity in the lung. Indirect calculation of nitrogen concentration requires accurate measurement of gas concentrations. To investigate the accuracy of the CO2 concentration and molar mass (MM) values used for the indirect calculation of nitrogen concentration in a commercial MBW device [EasyOne Pro LAB (EOPL), ndd Medizintechnik AG, Switzerland] and its impact on outcomes. We used high-precision gas mixtures to evaluate CO2 and MM sensor output in vivo and in vitro. We developed updated algorithms to correct observed errors and assessed the impact on MBW outcomes and FRC measurement accuracy compared with body plethysmography. The respiratory exchange ratio (RER)-based adjustment of the measured CO2 signal used in the EOPL led to an overestimated CO2 signal (range -0.1% to 1.0%). In addition, an uncorrected dependence on humidity was identified. These combined effects resulted in an overestimation of expired nitrogen concentrations (range -0.7% to 2.6%), and consequently MBW outcomes. Corrected algorithms reduced the mean (SD) cumulative expired volume by 15.8% (9.7%), FRC by 6.6% (3.0%), and lung clearance index by 9.9% (7.6%). Differences in FRC between the EOPL and body plethysmography further increased. Inadequate signal correction causes RER- and humidity-dependent expired nitrogen concentration errors and overestimation of test outcomes. Updated algorithms reduce average signal error, however, RER values far from the population average still cause measurement errors. Despite improved signal accuracy, the updated algorithm increased the difference in FRC between the EOPL and body plethysmography.NEW & NOTEWORTHY We investigated the accuracy of the molar mass (MM) and CO2 sensors of a commercial multiple-breath washout device (ndd Medizintechnik AG, Switzerland). We identified humidity and respiratory exchange ratio-dependent errors that in most measurements resulted in an overestimation of expired nitrogen concentrations, and consequently, MBW results. Functional residual capacity and lung clearance index decreased by 6.6% and 9.9%, respectively. Despite improved signal accuracy, the difference in FRC between the EOPL and body plethysmography increased.

Infant multiple breath washout using a new commercially available device: Ready to replace the previous setup?

Multiple breath washout (MBW) is a sensitive test to measure lung volumes and ventilation inhomogeneity from infancy on. The commonly used setup for infant MBW, based on ultrasonic flowmeter, requires extensive signal processing, which may reduce robustness. A new setup may overcome some previous limitations but formal validation is lacking. We assessed the feasibility of infant MBW testing with the new setup and compared functional residual capacity (FRC) values of the old and the new setup in vivo and in vitro. We performed MBW in four healthy infants and four infants with cystic fibrosis, as well as in a Plexiglas lung simulator using realistic lung volumes and breathing patterns, with the new (Exhalyzer D, Spiroware 3.2.0, Ecomedics) and the old setup (Exhalyzer D, WBreath 3.18.0, ndd) in random sequence. The technical feasibility of MBW with the new device-setup was 100%. Intra-subject variability in FRC was low in both setups, but differences in FRC between the setups were considerable (mean relative difference 39.7%, range 18.9; 65.7, P = 0.008). Corrections of software settings decreased FRC differences (14.0%, -6.4; 42.3, P = 0.08). Results were confirmed in vitro. MBW measurements with the new setup were feasible in infants. However, despite attempts to correct software settings, outcomes between setups were not interchangeable. Further work is needed before widespread application of the new setup can be recommended.

Airway clearance techniques for bronchiectasis.

People with non-cystic fibrosis bronchiectasis commonly experience chronic cough and sputum production, features that may be associated with progressive decline in clinical and functional status. Airway clearance techniques (ACTs) are often prescribed to facilitate expectoration of sputum from the lungs, but the efficacy of these techniques in a stable clinical state or during an acute exacerbation of bronchiectasis is unclear. Primary: to determine effects of ACTs on rates of acute exacerbation, incidence of hospitalisation and health-related quality of life (HRQoL) in individuals with acute and stable bronchiectasis. Secondary: to determine whether:• ACTs are safe for individuals with acute and stable bronchiectasis; and• ACTs have beneficial effects on physiology and symptoms in individuals with acute and stable bronchiectasis. We searched the Cochrane Airways Group Specialised Register of trials from inception to November 2015 and PEDro in March 2015, and we handsearched relevant journals. Randomised controlled parallel and cross-over trials that compared an ACT versus no treatment, sham ACT or directed coughing in participants with bronchiectasis. We used standard methodological procedures as expected by The Cochrane Collaboration. Seven studies involving 105 participants met the inclusion criteria of this review, six of which were cross-over in design. Six studies included adults with stable bronchiectasis; the other study examined clinically stable children with bronchiectasis. Three studies provided single treatment sessions, two lasted 15 to 21 days and two were longer-term studies. Interventions varied; some control groups received a sham intervention and others were inactive. The methodological quality of these studies was variable, with most studies failing to use concealed allocation for group assignment and with absence of blinding of participants and personnel for outcome measure assessment. Heterogeneity between studies precluded inclusion of these data in the meta-analysis; the review is therefore narrative.One study including 20 adults that compared an airway oscillatory device versus no treatment found no significant difference in the number of exacerbations at 12 weeks (low-quality evidence). Data were not available for assessment of the impact of ACTs on time to exacerbation, duration or incidence of hospitalisation or total number of hospitalised days. The same study reported clinically significant improvements in HRQoL on both disease-specific and cough-related measures. The median difference in the change in total St George's Respiratory Questionnaire (SGRQ) score over three months in this study was 7.5 units (P value = 0.005 (Wilcoxon)). Treatment consisting of high-frequency chest wall oscillation (HFCWO) or a mix of ACTs prescribed for 15 days significantly improved HRQoL when compared with no treatment (low-quality evidence). Two studies reported mean increases in sputum expectoration with airway oscillatory devices in the short term of 8.4 mL (95% confidence interval (CI) 3.4 to 13.4 mL) and in the long term of 3 mL (P value = 0.02). HFCWO improved forced expiratory volume in one second (FEV1) by 156 mL and forced vital capacity (FVC) by 229.1 mL when applied for 15 days, but other types of ACTs showed no effect on dynamic lung volumes. Two studies reported a reduction in pulmonary hyperinflation among adults with non-positive expiratory pressure (PEP) ACTs (difference in functional residual capacity (FRC) of 19%, P value < 0.05; difference in total lung capacity (TLC) of 703 mL, P value = 0.02) and with airway oscillatory devices (difference in FRC of 30%, P value < 0.05) compared with no ACTs. Low-quality evidence suggests that ACTs (HFCWO, airway oscillatory devices or a mix of ACTs) reduce symptoms of breathlessness and cough and improve ease of sputum expectoration compared with no treatment (P value < 0.05). ACTs had no effect on gas exchange, and no studies reported effects of antibiotic usage. Among studies exploring airway oscillating devices, investigators reported no adverse events. ACTs appear to be safe for individuals (adults and children) with stable bronchiectasis and may account for improvements in sputum expectoration, selected measures of lung function, symptoms and HRQoL. The role of these techniques in acute exacerbation of bronchiectasis is unknown. In view of the chronic nature of bronchiectasis, additional data are needed to establish the short-term and long-term clinical value of ACTs for patient-important outcomes and for long-term clinical parameters that impact disease progression in individuals with stable bronchiectasis, allowing further guidance on prescription of specific ACTs for people with bronchiectasis.

Pulmonary hyperpolarized (129) Xe morphometry for mapping xenon gas concentrations and alveolar oxygen partial pressure: Proof-of-concept demonstration in healthy and COPD subjects.

Diffusion-weighted (DW) hyperpolarized (129) Xe morphometry magnetic resonance imaging (MRI) can be used to map regional differences in lung tissue micro-structure. We aimed to generate absolute xenon concentration ([Xe]) and alveolar oxygen partial pressure (pA O2 ) maps by extracting the unrestricted diffusion coefficient (D0 ) of xenon as a morphometric parameter. In this proof-of-concept demonstration, morphometry was performed using multi b-value (0, 12, 20, 30 s/cm(2) ) DW hyperpolarized (129) Xe images obtained in four never-smokers and four COPD ex-smokers. Morphometric parameters and D0 maps were computed and the latter used to generate [Xe] and pA O2 maps. Xenon concentration phantoms estimating a range of values mimicking those observed in vivo were also investigated. Xenon D0 was significantly increased (P = 0.035) in COPD (0.14 ± 0.03 cm(2) /s) compared with never-smokers (0.12 ± 0.02 cm(2) /s). COPD ex-smokers also had significantly decreased [Xe] (COPD = 8 ± 7% versus never-smokers = 13 ± 8%, P = 0.012) and increased pA O2 (COPD = 18 ± 3% versus never-smokers = 15 ± 3%, P = 0.009) compared with never-smokers. Phantom measurements showed the expected dependence of D0 on [Xe] over the range of concentrations anticipated in vivo. DW hyperpolarized (129) Xe MRI morphometry can be used to simultaneously map [Xe] and pA O2 in addition to providing micro-structural biomarkers of emphysematous destruction in COPD. Phantom measurements of D0 ([Xe]) supported the hypotheses that differences in subjects may reflect differences in functional residual capacity.

Evaluation of sternochondroplasty efficacy in treatment of pectus deformities.

This study aimed to evaluate the efficacy of sternochondroplasty for repair of pectus deformities. Thirty-three patients underwent repair of pectus deformity with a sternochondroplasty technique between 1989 and 2009. Studied variables were age, sex, symptoms, pulmonary function tests before and after surgery, Haller index, complications, recurrence, and cosmetic results. The median age at operation was 13.27 years. Twenty patients (13 male and 7 female) had pectus excavatum, and 13 (11 male and 2 female) had pectus carinatum. Congenital anomalies associated with pectus excavatum included a skeletal anomaly in 6 (30%) patients and a cardiac anomaly in 4 (20%); only 1 patient with pectus carinatum had cardiac anomaly. Inspiratory vital capacity and forced expiratory volume in 1 s were significantly different before and after surgery in patients with pectus excavatum, but there was no significant difference in functional residual capacity. Pulmonary function tests showed no significant differences before and after surgery in patients with pectus carinatum. Complications after surgery were seroma in 2 cases and 1 case each of pneumothorax and atelectasis. Recurrence was observed in 2 cases of pectus excavatum. The cosmetic result was excellent in 93.9% of cases. Hospital mortality was zero. Sternochondroplasty is a desirable procedure for repairing pectus deformities. This procedure has minimal complications and the cosmetic and physiologic results are excellent.

Unilateral mechanical asymmetry: positional effects on lung volumes and transpulmonary pressure.

BackgroundVentilated patients with asymmetry of lung or chest wall mechanics may be vulnerable to differing lung stresses or strains dependent on body position. Our purpose was to examine transpulmonary pressure (PTP) and end-expiratory lung volume (functional residual capacity (FRC)) during body positioning changes in an animal model under the influence of positive end-expiratory pressure (PEEP) or experimental pleural effusion (PLEF).MethodsFourteen deeply anesthetized swine were studied including tracheostomy, thoracostomy, and esophageal catheter placement. Animals were ventilated at VT = 10 ml/kg, frequency of 15, I/E = 1:2, and FIO2 = 0.5. The animals were randomized to supine, prone, right lateral, left lateral, and semi-Fowler positions with a PEEP of 1 cm H2O (PEEP1) or a PEEP of 10 cm H2O (PEEP10) applied. Experimental PLEF was generated by 10 ml/kg saline instilled into either pleural space. PTP and FRC were determined in each condition.ResultsNo significant differences in FRC were found among the four horizontal positions. Compared to horizontal positioning, semi-Fowler's increased FRC (p < 0.001) by 56% at PEEP1 and 54% at PEEP10 without PLEF and by 131% at PEEP1 and 98% at PEEP10 with PLEF. Inspiratory or expiratory PTP showed insignificant differences across positions at both levels of PEEP. Consistently negative end-expiratory PTP at PEEP1 increased to positive values with PEEP10.ConclusionsFRC did not differ among horizontal positions; however, semi-Fowler's positioning significantly raised FRC. PTP proved insensitive to mechanical asymmetry. While end-expiratory PTP was negative at PEEP1, applying PEEP10 caused a transition to positive PTP, suggestive of reopening of initially compressed lung units.Electronic supplementary materialThe online version of this article (doi:10.1186/2197-425X-2-4) contains supplementary material, which is available to authorized users.

The Measurement of Lung Volumes Using Body Plethysmography: A Comparison of Methodologies

The statement of the American Thoracic Society and European Respiratory Society on the measurement of static lung volumes (SLV) suggests a preferred and alternate method for measuring and calculating SLV. To determine if differences in functional residual capacity (FRC), vital capacity (VC), residual volume (RV), and total lung capacity (TLC), obtained using preferred and alternate measurement and calculation methodologies, exist in a clinical setting. Patients attending for SLV at a hospital-based laboratory were recruited. Following spirometry, SLV was measured via body plethysmography, using the preferred and alternate methods in random order. Volumes were calculated using the preferred and alternate calculation methods. Subjects were classified according to standard ventilatory function interpretative strategies. Differences of the means between the measurement methods, and calculation methods were assessed. One hundred eight data sets were analyzed. Significant, but small differences (< 150 mL) in the means for VC and TLC, and RV and TLC were found in the normal and restricted groups, respectively. No significant differences in SLV parameters were found in subjects with air-flow obstruction. Twelve of the 108 changed ventilatory function classification between methods, with the alternate method delivering a lower inspiratory capacity and TLC without a change in RV in 66% of this subgroup. Identical results were obtained when data were analyzed using both calculation methods. Differences in FRC, VC, RV, and TLC obtained using the preferred and alternate measurement methodologies exist in the clinical setting in select classification groups and individuals. Differing calculation methods dependent on measurement method used may be unnecessary.

Manual hyperinflation partly prevents reductions of functional residual capacity in cardiac surgical patients - a randomized controlled trial

IntroductionCardiac surgery is associated with post-operative reductions of functional residual capacity (FRC). Manual hyperinflation (MH) aims to prevent airway plugging, and as such could prevent the reduction of FRC after surgery. The main purpose of this study was to determine the effect of MH on post-operative FRC of cardiac surgical patients.MethodsThis was a randomized controlled trial of patients after elective coronary artery bypass graft and/or valve surgery admitted to the intensive care unit (ICU) of a university hospital. Patients were randomly assigned to a "routine MH group" (MH was performed within 30 minutes after admission to the ICU and every 6 hours thereafter, and before tracheal extubation), or a "control group" (MH was performed only if perceptible (audible) sputum was present in the larger airways causing problems with mechanical ventilation, or if oxygen saturation (SpO2) dropped below 92%). The primary endpoint was the reduction of FRC from the day before cardiac surgery to one, three, and five days after tracheal extubation. Secondary endpoints were SpO2 (at similar time points) and chest radiograph abnormalities, including atelectasis (at three days after tracheal extubation).ResultsA total of 100 patients were enrolled. Patients in the routine MH group showed a decrease of FRC on the first post-operative day to 71% of the pre-operative value, versus 57% in the control group (P = 0.002). Differences in FRC became less prominent over time; differences between the two study groups were no longer statistically significant at Day 5. There were no differences in SpO2 between the study groups. Chest radiographs showed more abnormalities (merely atelectasis) in the control group compared to patients in the routine MH group (P = 0.002).ConclusionsMH partly prevents the reduction of FRC in the first post-operative days after cardiac surgery.Trial registrationNetherlands Trial Register (NTR): NTR1384. http://www.trialregister.nl

Hering–Breuer reflex, lung volume and position in prematurely born infants

To investigate the effect of position on the strength of the Hering-Breuer reflex in prematurely born infants and determine whether any differences seen were related to differences in lung or tidal volume between positions. Position related differences in the strength of the Hering-Breuer reflex relate to differences in lung or tidal volume. Prospective observational study. PATIENT/SUBJECT SELECTION: Eighteen infants, median gestational age 30 (range 25-32) weeks were studied. Infants were examined in the supine and prone position, each position was maintained for 2 hr. At the end of each 2-hr period, the strength of the Hering-Breuer reflex was assessed by determining the prolongation of expiration following an end inspiratory occlusion. In addition, tidal volume and functional residual capacity (FRC) were assessed in each position. The strength of the Hering-Breuer reflex was greater (P = 0.01) and the mean FRC was higher (P < 0.0001) in the prone compared to the supine position. The position related differences in the strength of the reflex correlated significantly with position related differences in FRC (P = 0.05). The Hering-Breuer reflex is stronger in the prone compared to the supine position. Our results suggest this is explained by position related differences in lung volume.

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 acutely 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. Pediatr Pulmonol. 1999; 28:24–30. © 1999 Wiley-Liss, Inc.

Longitudinal evaluation of pulmonary function in infants and very young children with cystic fibrosis

Thirty-two infants with cystic fibrosis (CF) had pulmonary function testing and chest radiographs at the time of diagnosis and on average 1 year later, when they had no acute respiratory symptoms. At diagnosis, 14 of 32 infants had respiratory symptoms (RESP) and 18 did not have respiratory symptoms (NRESP). There were no significant differences in age, weight, or length between the RESP and NRESP groups. At diagnosis, the RESP group had significantly lower forced expiratory flows compared to the NRESP group (41 +/- 32% vs. 98 +/- 48% predicted); however, there were no significant differences in functional residual capacity or chest radiographic scores. Between diagnosis and follow-up, the NRESP group had no significant change in pulmonary function but a decline in chest roentgenographic (CXR) scores (22 +/- 2 to 21 +/- 2). For infants in the RESP group, there were no significant changes in FRC or CXR score. Maximal expiratory flow at functional residual capacity (Vmax FRC) rose from diagnosis to 1 year follow-up (41 +/- 32% to 74 +/- 27% predicted; P < 0.002); however, at follow-up flows for the RESP group remained significantly lower than flows for the NRESP group (74% vs. 113% predicted; P < 0.0005). For the 32 infants with CF, there was significant correlation between percent predicted Vmax FRC at follow-up and at diagnosis (r = 0.47; P < 0.02). Those infants with lower percent predicted flows at diagnosis were more likely to have lower percent predicted flows 1 year later.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory function at follow-up after neonatal surfactant replacement therapy

Respiratory function was assessed at a median of 7 months (range 6–12) in 17 preterm infants who, in the neonatal period, had been entered into a multi-centre randomized placebo-controlled trial of prophylactic surfactant replacement therapy. Seven infants (median gestational age 28 weeks) received surfactant and the remaining ten infants (median gestational age 27 weeks) placebo. Respiratory function was assessed by measuring functional residual capacity (FRC), thoracic gas volume (TGV) and airways resistance ( R aw). Specific conductance ( SG aw) was calculated from R aw and TGV. There was no significant difference in FRC or TGV between the two groups. R aw, however, was significantly lower in the surfactant (median 41, range 21–48 cmH 2O l −1 s −1) compared to the placebo group (median 57, range 40–68 cmH 2O l −1 s −1),P < 0·05 and SG aw significantly higher in the surfactant (median 0·136, range 0·063–0·289 l cmH 2O −1 s −1) compared to the placebo group (median 0·081, range 0·062-0·134 l cmH 2O −1 s −1), P < 0·05. These results suggest that surfactant replacement therapy improves lung function at follow-up.

Effects of the heat-moisture exchangers on dynamic hyperinflation of mechanically ventilated COPD patients

In recent years the use of devices called Heat and Moisture Exchangers (HME) has become widespread as gas conditioners for ICU patients requiring mechanical ventilation. As an important variation of the resistive properties of the HME, related to flow and duration of use, has recently been pointed out during "in vitro" studies, the use of these devices in COPD patients could increase the levels of auto PEEP and dynamic hyperinflation. In this study we have compared the levels of auto PEEP and difference in functional residual capacity (delta FRC) in a group of COPD patients, requiring controlled mechanical ventilation (CMV), at basal conditions and after the insertion into the circuit of three HMEs (Dar Hygrobac, Pall Ultipor, Engstrom Edith) at random: the results obtained excluded a significant increase of auto PEEP and delta (FRC) both with "new" HMEs and after 12 h of continuous use.

Measurement of lung volumes during active and quiet sleep in infants.

The question of whether functional residual capacity (FRC) falls in infants during active sleep has been clouded by studies using different subject groups and techniques for measurements of lung volume and determination of sleep state. Twenty healthy full-term infants within the first week of life participated in the present study. Neurophysiological and behavioral criteria were used to define sleep state, and measurements of FRC were made using a specially constructed closed-circuit helium dilution system. Regularity of respiration was recorded using magnetometers on the chest and a modified respirator monitor. Results showed that no significant changes in FRC occurred, related either to sleep state or to regularity of respiration. In addition, we failed to detect any differences in FRC between the sexes.

Total respiratory system compliance in asymptomatic infants with cystic fibrosis.

Total respiratory system compliance (Crs) was assessed by the weighted spirometer method in 11 asymptomatic infants (mean age, 11.1 months) with cystic fibrosis (CF) who had normal chest radiographs. In addition to Crs, functional residual capacity (FRC), respiratory rate (RR), and mixing index (MI) were measured. There was no significant difference in FRC between normal controls (n = 36) and CF infants (190 +/- 69 versus 186 +/- 63 ml; p less than 0.8), although the CF group had a higher RR (32 +/- 7 versus 37 +/- 7 BPM; p less than 0.05) and a lower MI (45 +/- 7 versus 40 +/- 8%; p less than 0.05), reflecting an abnormal distribution of ventilation. The lower Crs (9.0 +/- 3.4 versus 5.7 +/- 2.8 ml/cm H2O; p less than 0.01) and the lower specific compliance, Crs/FRC (0.049 +/- 0.013 versus 0.029 +/- 0.007 1/cm H2O; p less than 0.0001), in the CF group were the parameters that best distinguished the normal control and CF infants. We conclude that the measurement of Crs represents a noninvasive method for detecting early pulmonary function abnormalities in CF infants.

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.

The effect of ketamine on the functional residual capacity in young children.

The effect of ketamine on the functional residual capacity (FRC) was measured in nine ASA class I children prior to elective surgery. FRC was determined by the closed-circuit helium dilution method on the day prior to surgery in the awake state and also following induction of anesthesia on the day of the operation. Anesthesia consisted of ketamine by continuous intravenous infusion following preanesthetic sedation with atropine and triclofos or flunitrazepam. There were no significant differences in FRC between the measurements in the awake state and anesthetized (392 +/- 43 SEM ml, and 411 +/- 53 SEM ml, respectively), and the authors conclude that ketamine does not affect resting lung volume in young children.