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PubMed2003

Accelerometry of adductor pollicis muscle predicts recovery of respiratory function from neuromuscular blockade.

BACKGROUND: Residual paralysis increases the risk of pulmonary complications but is difficult to detect. To test the hypothesis that accelerometry predicts effects of residual paralysis on pulmonary and upper airway function, the authors related tests of pulmonary and pharyngeal function to accelerometry of adductor pollicis muscle in 12 partially paralyzed volunteers. METHODS: Rocuronium (0.01 mg/kg + 2-10 microg x kg-1 x min-1) was administered to maintain train-of-four (TOF) ratios (assessed every 15 s) of approximately 0.5 and 0.8 over a period of more than 5 min. The authors evaluated pharyngeal and facial muscle functions during steady state relaxation and performed spirometric measurements every 5 min until recovery. Upper airway obstruction was defined as a mean ratio of expiratory and inspiratory flow at 50% of vital capacity of greater than 1. The TOF ratio associated with "acceptable" pulmonary recovery (forced vital capacity and forced inspiratory volume in 1 s of > or =90% of baseline) was calculated using a linear regression model. RESULTS: At peak blockade (TOF ratio 0.5 +/- 0.16), forced inspiratory flow was impaired (53 +/- 19%) to a greater degree than forced expiratory flow (75 +/- 20%) with a mean ratio of expiratory and inspiratory flow at 50% of vital capacity of 1.18 +/- 0.6. Upper airway obstruction, observed in 8 of 12 volunteers, paralleled an impaired ability to swallow reported by 10 of 12 volunteers. In contrast, all volunteers except one could sustain a head lift for more than 5 s. The authors calculated that a mean TOF ratio of 0.56 (95% confidence interval, 0.22-0.71) predicts "acceptable" recovery of forced vital capacity, whereas forced inspiratory volume in 1 s was impaired until a TOF ratio of 0.95 (0.82-1.18) was reached. A 100% recovery of TOF ratio predicts an acceptable recovery of forced vital capacity, forced inspiratory volume in 1 s, and mean ratio of expiratory and inspiratory flow at 50% of vital capacity in 93%, 73%, and 88% of measurements (calculated negative predictive values), respectively. CONCLUSION: Impaired inspiratory flow and upper airway obstruction frequently occur during minimal neuromuscular blockade (TOF ratio 0.8), and extubation may put the patient at risk. Although a TOF ratio of unity predicts a high probability of adequate recovery from neuromuscular blockade, respiratory function can still be impaired.

Adult↗
PubMed1993

Plethysmographic parameters in the assessment of reversibility of airways obstruction in patients with clinical emphysema.

Slow inspiratory vital capacity (IVC) and forced expiratory volume in 1 s (FEV1) before and after an inhaled beta-agonist are widely used to detect reversible airflow limitation in patients with chronic obstructive lung disease. The measurement of airways resistance (Raw) during quiet breathing with the body plethysmograph is less frequently used. It may well be of importance in clinical emphysema where measurement of FEV1 is confounded by the collapse of the bronchi, which does not occur when measuring Raw during quiet breathing. We assessed whether Rrs, in addition to IVC and FEV1, can be used to gain a better insight into the reversibility with 400 micrograms of fenoterol in patients with clinical emphysema. We studied a group of 51 patients (9 women and 42 men; mean [+/- SD] age, 64.7 [7.7] years) who had a clinical diagnosis of emphysema. Significant reversibility was identified by spirometry (IVC, FEV1) and body plethysmography (Raw) in 20 patients (39 percent). Inspiratory vital capacity alone identified reversibility of airflow limitation in 11 patients (22 percent). In 5 patients (10 percent), the postbronchodilator improvement was seen exclusively in the Raw measurement. In the remaining patients, absence of improvement in spirometric and plethysmographic parameters was found. Subjective improvement occurred to the same extent in patients whose Raw and IVC improved. We concluded that Raw gives important information about the reversibility of airways obstruction in patients with clinical emphysema. Therefore, we suggest that tests during quiet breathing should be part of the routine examination of airways obstruction in patients with "irreversible" obstruction by conventional spirometry.

Administration, Inhalation↗
PubMed1978

Maturation of respiratory control in unanesthetized newborn rabbits.

The maturation of control of breathing was studied in unanesthetized rabbit pups breathing room air in a body plethysmograph during the first 8 postnatal days. Measurements include pulmonary ventilation (VE), tidal volume (VT), inspiratory (TI) and total breathing cycle (Ttot) durations, TI/Ttot, mean inspiratory flow (VT/TI), and tracheal pressure developed by the inspiratory muscles 0.1 and 0.2 s after the onset of inspirations with airways occluded at functional residual capacity (P0.1 and P0.2). All of the above variables increased progressively from the 1st to the 8th day, except for P0.1, P0.2, and TI/Ttot which remained constant. The constancy of TI/Ttot implies that the increase in VE with age was due entirely to increased VT/TI. The constancy of P0.1 and P0.2 implies that the increase in VT/TI with age was due to decreased "effective" impedance of the respiratory system. The latter probably mainly reflects increased compliance and decreased flow resistance with growth. The results also show that during the first 8 days of life there is a progressive shift to the right in the VT vs. TI relationship.

Aging↗
PubMed1996

Pulmonary function in obese subjects with a normal FEV1/FVC ratio.

STUDY OBJECTIVE: To determine pulmonary function test (PFT) profile and respiratory muscle strength (RMS) of a group of obese individuals who did not have evidence of obstructive airway disease or other underlying diseases affecting their respiratory system. DESIGN: Prospective, open. SETTING: PFT laboratory, VA Medical Center. PARTICIPANTS: Sixty-three consecutive obese (body mass index greater than 27.8 kg/m2) male subjects without overt obstructive airway disease (FEV1/FVC ratio greater than 80%). MEASUREMENTS AND RESULTS: Standard PFTs and maximum static inspiratory (PImax) and expiratory (PEmax) mouth pressures were determined. RMS was calculated from the following formula: (PImax+PEmax):2. Two distinct groups were identified, those with normal maximum voluntary ventilation (MVV) (> 80% predicted) and those with low MVV. Both inspiratory and expiratory flow rates (FVC, FEV1, forced expiratory flow at 50% vital capacity [V50], maximum inspiratory flow rate [MIFR]), lung volumes (vital capacity [VC], inspiratory capacity [IC], expiratory reserve volume), PImax, and RMS were significantly lower, and residual volume/total lung capacity (RV/TLC) ratio was significantly higher in obese subjects with low MVV compared with those in whom MVV was normal. MVV correlated significantly with FVC, FEV1, V50, MIFR, TLC, VC, IC, RV/TLC, and RMS; the strongest correlation was with MIFR (r = 0.76, p < 0.0001). CONCLUSIONS: Standard PFTs allow recognition of a subgroup of obese subjects without overt obstructive airway disease who have more severe lung dysfunction, the marker of which is a low MVV. Peripheral airway abnormalities may be responsible for these observations.

Adult↗
PubMed1988

Inspiratory muscles during exercise: a problem of supply and demand.

The capacity of inspiratory muscles to generate esophageal pressure at several lung volumes from functional residual capacity (FRC) to total lung capacity (TLC) and several flow rates from zero to maximal flow was measured in five normal subjects. Static capacity was 126 +/- 14.6 cmH2O at FRC, remained unchanged between 30 and 55% TLC, and decreased to 40 +/- 6.8 cmH2O at TLC. Dynamic capacity declined by a further 5.0 +/- 0.35% from the static pressure at any given lung volume for every liter per second increase in inspiratory flow. The subjects underwent progressive incremental exercise to maximum power and achieved 1,800 +/- 45 kpm/min and maximum O2 uptake of 3,518 +/- 222 ml/min. During exercise peak esophageal pressure increased from 9.4 +/- 1.81 to 38.2 +/- 5.70 cmH2O and end-inspiratory esophageal pressure increased from 7.8 +/- 0.52 to 22.5 +/- 2.03 cmH2O from rest to maximum exercise. Because the estimated capacity available to meet these demands is critically dependent on end-inspiratory lung volume, the changes in lung volume during exercise were measured in three of the subjects using He dilution. End-expiratory volume was 52.3 +/- 2.42% TLC at rest and 38.5 +/- 0.79% TLC at maximum exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Spirometric data in South Indian subjects 60-80 years of age.

Forced expiratory and inspiratory vital capacities and the timed expiratory and inspiratory volumes and forced expiratory and inspiratory flow rates were determined in 50 old men and women between 60-80 years of age. Some of the ratios between expiratory and inspiratory volumes and flow-rates that have been found to be useful for detecting some forms of ventilatory defects are also given.

Aged↗
PubMed1997

Relationship between dyspnoea, pulmonary function and exercise capacity in patients with cystic fibrosis.

The median age of survival in patients with cystic fibrosis (CF) has improved considerably. Despite this improvement, deterioration of pulmonary function and decrease in exercise capacity are still the main problems for many patients. Although dyspnoea is a common complaint in CF patients, relatively little regard has been paid to this symptom. This study examined the relationship between dyspnoea, bicycle exercise capacity and pulmonary function in patients with CF. In 14 patients in a stable clinical condition, pulmonary function [forced expiratory volume in 1 s (FEV1), inspiratory vital capacity (IVC)], bicycle exercise capacity [maximum exercise capacity (Wmax)], subjective degree of dyspnoea during daily living [Medical Research Council (MRC) dyspnoea scale], and during exercise (Borg scale) were assessed. The mean (SD) age of the patients was 25 (6.8) years, FEV1 was 41 (19)% predicted, IVC was 63 (17)% predicted and FEV1/IVC ratio was 47 (10)%; median (range) Wmax was 55 (0-79)% predicted. Bicycle exercise test performance appeared to be mainly determined by pulmonary function and MRC dyspnoea grade; multiple regression equation containing FEV1 and dyspnoea accounted for 76% of the variance in Wmax (% predicted) (Wmax = -7.9 dysp + 1.1 FEV1, +24). Exercise dyspnoea, assessed by the Borg scale, showed a significant linear correlation with minute ventilation. (VE), maximal voluntary ventilation (MVV) (%) (r = 0.76; P < 0.001). Medical Research Council dyspnoea score correlated relatively poorly with FEV1 (% predicted) (r = -0.17; n.s.) and IVC (% predicted) (r = -0.48; n.s.). Borg score at maximal exercise did not correlate with MRC dyspnoea score (r = -0.07). Borg50% score correlated significantly with MRC dyspnoea score (r = 0.61; P < 0.05). These results show that dyspnoea has an influence on exercise capacity. Dyspnoea score showed a large inter-individual variation, not strongly related to pulmonary function. It is concluded that dyspnoea deserves more attention in CF patients and needs to be assessed in rehabilitation programmes and other intervention studies in these patients.

Adolescent↗
PubMed1990

A long-term study of interstitial lung disease in systemic lupus erythematosus.

The clinical course of chronic diffuse interstitial lung disease (ILD) was studied in 14 patients with SLE. The mean duration of follow-up was 7.3 years. All patients had dyspnea on exertion, pleuritic chest pain, chronic cough, and basilar rales. Chest roentgenogram showed diffuse or basilar infiltrates, pleural disease, and elevation of both diaphragms. Systemic corticosteroids were given early in the course of the illness for lung involvement and multisystem disease. Diffusing capacity for carbon monoxide (DLCO) and inspiratory vital capacity (IVC) improved or remained unchanged in the majority of patients. Respiratory complaints improved in all patients; however, two patients died of pulmonary fibrosis and another died of bacterial pneumonia. Alveolar septal deposits of immunoglobulins and complement were found. This study showed that while variability existed among individual subjects, the clinical progression of ILD was slow and tended to improve or stabilize with time.

Adrenal Cortex Hormones↗
PubMed2002

Respiratory mechanics in mice: strain and sex specific differences.

To assess the contribution of genetic background to respiratory mechanics, we developed a ventilator unit to measure lung function parameters in the mouse. We studied two commonly used inbred mice strains originating from Mus musculus domesticus (C57BL/6 and C3HeB/FeJ) and a third strain derived from Mus musculus molossinus [Japanese fancy mouse 1 (JF1)]. The ventilator allows for accurate performance of the different breathing manoeuvres required for measuring in- and expiratory reserve capacity, quasi-static and dynamic compliance, and airway resistance. In combination with a mass spectrometer for monitoring gas concentrations, single-breath manoeuvres were performed and He-expirograms obtained, from which dead space volume and slope of phase III were determined. From each strain and each sex, 10, 2-month old animals were studied immediately after being killed by an intraperitoneal overdose of xylazine and ketamine. C3HeB/FeJ and C57BL/6 exhibited comparable lung volumes. In male C3HeB/FeJ mice, e.g. vital capacity (VC) was 1072 +/- 79 microL, inspiratory reserve capacity 782 +/- 88 microL, and dead space volume at total lung inflation 216 +/- 18 microL. Lung volumes of JF1 were significantly lower (e.g. VC 611 +/- 53 microL, P < 0.01) even when normalized to body weight. In all three strains, specific lung volumes were significantly higher in females than in males, possibly explained by a higher oxygen demand during pregnancy and lactation, both of which fill most of their life times. Static compliance in C3HeB/FeJ was 64.3 +/- 5.4 microL cmH2O-1. It was smaller in C57BL/6 and JF1 mice, even when related to the lung volume. Analysis of the degree of genetic vs. non-genetic components of the phenotypic variation revealed that at least 80% of the total variation of lung volumes and static compliance in the mixed population is attributable to genetic differences between individuals. These differences will be verified in further studies by segregation and genetic linkage analysis.

Animals↗
PubMed2003

[Sleep-disordered breathing in neuromuscular diseases].

UNLABELLED: Sleep-disordered breathing is common in neuromuscular diseases but remains poorly defined in its relationship to daytime respiratory function. METHODS: We prospectively compared supine lung and respiratory muscle function with results of polysomnography/capnometry in 35 patients with progressive myopathies (age 32.5 +/- 15 years). RESULTS: 32/35 patients had restrictive ventilatory defect, 9/32 had hypercapnic respiratory failure by day (PaCO(2) 66.0 +/- 15.7 mm Hg). Supine inspiratory vital capacity (IVC(S)) correlated with maximal inspiratory muscle pressure (R = 0.75), respiratory muscle strain (P0.1/PImax, R = - 0.68), and daytime blood gases (p < 0.005 for all). SDB in the way of REM-sleep hypopneas, circumscribed hypoventilation episodes and sleep-stage independent continuous hypoventilation (PtcCO(2) > 50 mmHg > 50% of sleep time) was common at IVC(S)< 60% pred, and preceded daytime hypercapnia. IVC(S) correlated with nocturnal SaO(2) (R = 0.64), PtcCO(2) (R = - 0.87), percent light sleep (R = 0.67) and deep sleep (R = - 0.76). IVC(S) correlated only marginally with respiratory disturbance index (total sleep, R = - 0.45; REM-sleep, R = - 0.44). IVC(S) < 60% was 96% sensitive, 78% specific for presence of SDB. IVC(S) < 20 % was 89% sensitive, 96% specific for daytime hypercapnia. CONCLUSIONS: IVC(S) correlates with respiratory muscle function, daytime and nocturnal blood gases, and is highly predictive of SDB and daytime hypercapnia.

Adult↗
PubMed1991

Sulfuric acid-layered ultrafine particles potentiate ozone-induced airway injury.

Urban air pollution in the United States is composed of a complex mixture of particles and gases. Among the most prominent products of the atmospheric pollutants are sulfur oxides and ozone. In this report, we use two exposure protocols to examine the interaction between exposure to these two pollutants. In the first exposure regimen, guinea pigs were exposed to sulfuric acid (pure sulfuric acid mist or sulfuric acid layered on ZnO) for 1 h. Each exposure is followed 2 h later by another exposure to 0.15 ppm ozone for 1 h. Pulmonary function parameters were measured immediately after the ozone exposure. In guinea pigs that were exposed to 300 micrograms/m3 pure sulfuric acid mist, subsequent exposure to 0.15 ppm ozone did not produce additional change in pulmonary functions. In guinea pigs that were exposed to 84 micrograms/m3 sulfuric acid layered on ZnO, subsequent exposure to 0.15 ppm ozone produced more than additive alterations in vital capacity and diffusing capacity. In the second exposure regimen, guinea pigs were exposed to 24 micrograms/m3 sulfuric acid layered on ZnO for 3 h/d for 5 d. On d 8 and 9, animals received two additional daily 3-h exposures to 24 micrograms/m3 sulfuric acid layered on ZnO, and pulmonary functions were measured at the end of the daily exposure. Greater reductions in lung volumes and diffusing capacity were observed in animals on d 9 than would be observed in animals that received no additional exposure. In the third exposure regimen, guinea pigs were exposed to 24 micrograms/m3 sulfuric acid layered on ZnO for 3 h/d for 5 d. On d 9, animals were exposed to 0.15 ppm ozone for 1 h and pulmonary functions were measured at the end of the ozone exposure. Ozone exposure on d 9 induced reductions in lung volumes and diffusing capacity that were not observed in animals receiving exposures to either ozone or sulfuric acid layered ZnO alone. We conclude that single or multiple exposure to sulfuric acid-layered ZnO sensitizes guinea pigs to subsequent sulfuric acid or ozone exposure.

Aerosols↗
PubMed1994

Pressure-volume relations of the respiratory system in healthy children.

Static pressure-volume (P-V) curves of the respiratory system were obtained in 48 healthy children (1 mo to 16 yr of age) during anesthesia and muscle paralysis. The lungs were inflated to a pressure of 25 to 40 cm H2O, and during the subsequent deflation an interrupter placed in the airway tubing opened and closed every 0.16 s. Airway flow was integrated to obtain the volume decrement between consecutive flow interruptions. Airway pressure was measured during interruptions, and a curve relating pressure to lung volume was plotted, assuming the lung volume at zero pressure to equal functional residual capacity (FRC). FRC was measured using tracer gas washout. The maximum slope of the P-V curve (maximum compliance = Crsmax, ml/cm H2O) was closely related to length (in centimeters) of the child: Crsmax = 7.7 x 10(-4) x length2.38; r = 0.97. The pressure coinciding with Crsmax was 6 +/- 1 cm H2O (mean +/- SD) in infants (1 to 6 mo of age) and 12 +/- 1 cm H2O in older children (> 1.5 yr of age). Total lung capacity (TLC) per kg body weight increased with age and was 52 +/- 13 ml/kg in infants and 87 +/- 11 mg/kg in older children. The FRC/TLC ratio was greater in infants (38 +/- 4%) than in older children (30 +/- 5%). The lung volume coinciding with Crsmax was nearly the same at all ages, when expressed as a percentage of TLC: 62 +/- 3%. Specific compliance of the respiratory system, that is, Crsmax/TLC, decreased with growth and was 0.044 +/- 0.006 cm H2O-1 in infants and 0.035 +/- 0.004 cm H2O-1 in older children. It is concluded that although the P-V relations of the respiratory system changed markedly with growth, especially during the first year of life, the lung volume (%TLC) at which maximum compliance occurred varied little.

Adolescent↗
PubMed1989

Breathlessness induced by dissociation between ventilation and chemical drive.

Suppression of ventilation by tasks such as talking may produce breathlessness in normal individuals under conditions when a strong respiratory drive exists, e.g., during exercise, and in patients with severe lung disease. To investigate the nature of breathlessness produced by a dissociation between ventilation and chemical drive, we studied ten naive normal subjects who breathed at various levels of ventilation while end-tidal PCO2 (PETCO2) was held at 55 mm Hg. After a 10-min equilibration period of free breathing at PETCO2 = 55 mm Hg, subjects used a visual target to adjust ventilation to five different levels ranging from 50% below to 50% above the chemically driven ventilation (CDV). Ratings of breathlessness were made on a visual analogue scale relative to the intensity of breathlessness experience at CDV. As ventilation was targeted to levels below CDV, all subjects became increasingly breathless; the response was more variable when ventilation was targeted to levels above CDV. Overall, the relationship between ventilation and breathlessness was described by a hyperbolic function, for which the coefficient of determination (R2) was 0.92. Ventilation was suppressed below CDV without recruitment of antagonistic muscles during inspiration. The intensity of breathlessness was not correlated with measures of respiratory effort. We conclude that suppressed ventilation is a useful model for the study of breathlessness not fully explained by measures of respiratory effort and we speculate that the dissociation between chemical drive and afferent signals produced by motion of the lung and chest wall is important in modulating the sensation of breathlessness.

Abdominal Muscles↗
PubMed1979

Hypoxemia during exercise in patients with chronic obstructive pulmonary disease.

Arterial oxygenation at rest and during maximal treadmill exercise was studied in a group of 17 patients with chronic obstructive pulmonary disease. Patients who developed exertional hypoxemia (subgroup 1) were compared to others who did not (subgroup 2). There was no significant difference between the 2 subgroups at rest in terms of mixed venous PO2, cardiac output, or venous admixture. Subgroup 1 had more severe respiratory impairment than subgroup 2, but there was marked overlap of their respective lung volumes and flows. Both subgroups showed the same extent of desaturation of mixed venous blood during maximal treadmill exercise, so that exertional hypoxemia cannot be explained on the basis of low mixed venous O2. The marked difference between subgroup 1 and subgroup 2 was that the latter showed decreased venous admixture on exercise. Because of the relative constancy of mixed venous blood desaturation, arterial saturation was closely correlated with venous admixture both at rest (r = 0.931) and during exercise (r = 0.985).

Arteries↗
PubMed1981

Comparison of hydrostatic weighing at residual volume and total lung capacity.

Hydrostatic weighing (HW) was performed at both residual volume (RV) and total lung capacity (TLC) (both measured on land) to determine if underwater weighting at extreme lung volumes affected the measurement of body density. Subjects were 72 middle-aged males (mean age = 43.4 yr) and 51 middle-aged females (mean age = 40.2 yr). Subjects were first assessed for underwater weight at RV for at least 10 trials. Subjects were than instructed to inspire maximally and hold their breath underwater for as long as they could. Three trials at TLC were used for assessment of underwater weight. Forced vital capacity and residual volume (oxygen dilution) were determined separately on land. Small but statistically significant differences in body density (Db) were observed with the use of RV (1.0354 g/ml for men and 1.0196 g/ml for women) vs TLC (1.0367 g/ml for men and 1.0221 g/ml for women) (p less than 0.05). Percent fat values for the RV and TLD data differed by only 0.5% for men and 0.9% for women. Results indicated that the difference between percent fat determination by HW at RV and TLC, was negligible. It was concluded that HW at TLC may be the method of choice for subjects who are uncomfortable with performing the technique of underwater weighing at RV.

Adipose Tissue↗
PubMed2003

Study of Clara cell 16, KL-6, and surfactant protein-D in serum as disease markers in pulmonary sarcoidosis.

STUDY OBJECTIVES: To determine the discriminative value of serum Clara cell 16 (CC16), KL-6, and surfactant protein (SP)-D as markers of interstitial lung diseases, and their ability to reflect pulmonary disease severity and prognosis in sarcoidosis. SUBJECTS: Seventy-nine patients with sarcoidosis and 38 control subjects. MEASUREMENTS: Serum CC16, KL-6, and SP-D concentrations at disease presentation were measured. Pulmonary function tests and chest radiographs were analyzed at presentation and 2-year follow-up. RESULTS: All markers co-correlated, and a significant difference was found between CC16, KL-6 (Krebs von den Lungen-6), and SP-D levels in patients with sarcoidosis and control subjects (p < 0.0001). Receiver operating characteristic curve analysis revealed largest area under the curve for KL-6. Significantly higher levels of CC16 and KL-6 were found in patients with parenchymal infiltration (stage II, III) compared to patients without parenchymal infiltration (stage I). In concordance, CC16 and KL-6 levels inversely correlated with diffusion capacity and total lung capacity, and KL-6 also with inspiratory vital capacity. Moreover, higher KL-6 levels were weakly but significantly associated with persistence or progression of parenchymal infiltrates at 2-year follow-up. CONCLUSION: In this study, KL-6 appears to be the best discriminative marker in differentiating patients with sarcoidosis from healthy control subjects; however, as it is not a specific marker for this condition, this quality is unlikely to be useful as a diagnostic tool. Both CC16 and KL-6 may be of value in reflecting disease severity, and KL-6 tends to associate with pulmonary disease outcome.

Adult↗
PubMed1994

Exercise cardiorespiratory function before and one year after operation for pectus excavatum.

In 35 patients with pectus excavatum (aged 17.9 +/- 5.6 years) pulmonary function and maximal exercise test results were compared before and at 1 year after operation. The lower posteroanterior chest diameter on the lateral x-ray film was significantly smaller than normal (p < 0.0001) and increased significantly after operation (p < 0.0001). Preoperatively, total lung capacity (86.0% +/- 14.4%; p = 0.0001) and inspiratory vital capacity (79.7% +/- 16.2; p = 0.0001) were significantly smaller than predicted and further decreased after operation (-9.2% +/- 9.2%; p = 0.0001 and -6.6% +/- 10.7%; p = 0.0012, respectively). Arterial blood gas values displayed normal patterns with increasing exercise both before and after operation. Only the arterial pH decreased more after operation than before (p = 0.0026). After operation there was a significant increase in maximal oxygen uptake (oxygen uptake; p = 0.0002 and oxygen uptake per kilogram; p = 0.0025) and oxygen pulse (oxygen uptake/heart rate approximates an indirect parameter for stroke volume; p = 0.0333) during exercise, whereas the maximal work performed was unchanged. Efficiency of breathing (ratio of tidal volume/inspiratory vital capacity) at maximal exercise improved significantly after operation (p = 0.0005). Ventilatory limitation of exercise (defined by an increase in carbon dioxide tension during exercise) was found in 43.9% of the patients before operation. A tendency of improvement was noted (not significant) after operation (difference in carbon dioxide tension 0.6 +/- 0.4 kPa before versus 0.3 +/- 0.5 kPa after operation). However, the group with normal preoperative carbon dioxide elimination had a ventilatory limitation of exercise after operation (difference in carbon dioxide tension -0.4 +/- 0.3 kPa before versus -0.1 +/- 0.3 kPa after operation; p = 0.0128) with a significant increase in oxygen consumption (p = 0.0007). In conclusion the subjective physical improvement after operation is not explained by changes in cardiorespiratory function at exercise. The data suggest a higher work of breathing after operation.

Adolescent↗