Inspiratory muscle training during pulmonary rehabilitation in chronic obstructive pulmonary disease: A randomized trial.

Although recommended by international guidelines, the benefit of inspiratory muscle training (IMT) in addition to rehabilitation remains uncertain. The objective was to demonstrate the effectiveness of IMT on dyspnea using Borg scale and multidimensional dyspnea profile questionnaire at the end of a 6-minute walk test (6MWT) in patients with chronic obstructive pulmonary disease (COPD) with preserved average maximum inspiratory pressure (PImax) of 85 cm H2O (95% of predicted (pred.) value) and admitted for a rehabilitation program in a dedicated center. In a randomized trial, comparing IMT versus no IMT in 32 COPD patients without inspiratory muscle weakness (PImax >60 cm H2O) who were admitted for pulmonary rehabilitation (PR) for 3 weeks, we evaluated the effect of IMT on dyspnea, using both Borg scale and multidimensional dyspnea profile (MDP) at the end of the 6MWT, and on functional parameters included inspiratory muscle function (PImax) and 6MWT. All testings were performed at the start and the end of PR. In unadjusted analysis, IMT was not found to be associated with an improvement of either dyspnea or PImax. After adjustment on confounders (initial Borg score) and variables of interaction (forced expiratory volume in 1 second (FEV1)), we found a trend toward an improvement of "dyspnea sensory intensity", items from MDP and a significant improvement on the variation in the 2 items of MDP ("tight or constricted" and "breathing a lot"). In the subgroup of patients with FEV1 < 50% pred., 5 items of MDP were significantly improved, whereas no benefit was observed in patients with FEV1 > 50% pred. IMT did not significantly improve dyspnea or functional parameter in COPD patients with PImax > 60 cm H2O. However, in the subgroup of patients with FEV1 < 50% pred., MDP was significantly improved.

[Pulmonary arterial hypertension in the elderly subject]. / Hypertension artérielle pulmonaire du sujet âgé. La cohorte d'un centre régional.

OBJECTIVE: To describe the features of pulmonary arterial hypertension (PAH) in elderly patients. METHODS: A single centre, descriptive study of PAH patients consecutively referred to a regional centre, from September 2002 to February, 1st, 2009. The group of patients aged 65 and above at the time of the diagnosis was compared to the younger patients. RESULTS: Sixty-six patients suffering from PAH (group 1) have been investigated by means of right heart catheterisation. There were 24 patients aged 65 and above. Mean pulmonary arterial pressure was lower in the patients aged over 65. The older patient group had more respiratory and/or cardiac co-morbidities, a lower median distance in the 6minute walk test and a higher median Pro-BNP level. Specific PAH treatments were prescribed in both groups. Fifteen patients aged 65 and above were on long-term oxygen therapy (vs four younger patients, p<0.0001). The elderly patients had a median survival of 32 months. CONCLUSION: The diagnosis of PAH in elderly patients is associated with a poor prognosis. The management of these patients needs further studies.

[A bilateral diaphragmatic paralysis due to Parsonage and Turner syndrome--its evolution over eight years]. / Paralysie diaphragmatique bilatérale imputable à un syndrome de Parsonage-Turner. Evolution à huit ans.

The diaphragmatic paralysis is a rare disease whose causes and evolving forms are numerous. We report the development to eight years of paralysis diaphragmatic bilateral attributed to a Parsonage-Turner syndrome: the lack of recovery is proved by respiratory functional follow-up. The therapeutic possibilities, limited, are discussed.

Pulmonary function in men after repeated sessions of oxygen breathing at 0.25 MPa for 90 min.

HYPOTHESIS: We wanted to evaluate the pulmonary effects of discontinuous oxygen breathing (15 min O2, 2 min air breaks, 15:2), at 0.25 MPa once a day for 90 min O2 (6 sequences) over 10 d. This sequence, which has never been evaluated, is currently used in our hyperbaric therapy center. METHODS: Clinical and functional pulmonary status (questionnaire, spirometry, flow/volume loop, pulmonary diffusing capacity for carbon monoxide) was assessed in 10 non-smoking healthy volunteers after one exposure at 0.25 MPa consisting of 90 min of discontinuous oxygen breathing (15:2) and in 10 non-smoking patients who received a hyperbaric treatment consisting of 90 min of the same discontinuous O2 breathing (15:2) once a day over 10 d. The patients received daily intravenous methylprednisolone (1 mg x kg(-1)) and nicergoline (60 mg). RESULTS: There were no respiratory symptoms in either group. As expected, for a single exposure of that duration, lung function did not change in volunteers; however, a significant decrease in maximal expiratory flows (MEF) at 50 (-15%) and 25% (-33%) of forced vital capacity (p < 0.05) without change in forced vital capacity (FVC) appeared in patients treated over 10 d. CONCLUSION: Repetition of the 15:2 oxygen breathing sequence for 90 min once a day over 10 d led to greater flow limitation in peripheral airways than reported after continuous oxygen breathing of 210 min at 0.3 MPa which showed a 7% decrement in MEF50 and a 12% decrement in MEF25. No studies reporting these indexes were found in the 0.2-0.25 MPa range. Similar decrements in MEF50 and MEF25 with steady FVC have been reported after 14 d of daily hyperbaric therapy (0.24 MPa) with 30:5 sequence (-9% and -13%, respectively), 80% of the patients were symptom free. Similarily, our patients were all symptom free and remained so 1 yr after the study, hence, this toxicity is of weak clinical significance in subjects free of inflammatory lung diseases. HBO therapy, though safe, is not totally without effect on the lung.

Regional brain bioamine levels under hyperbaric oxygen in two unequally susceptible strains of mice.

BACKGROUND: Hyperbaric oxygen (HBO) increases monoamine deamination with related toxic products which aggravates hyperbaric oxygen (HBO) neurotoxicity. However, the possibility of some protective action of monoamines balanced by the toxicity of their metabolites have received little attention. HYPOTHESIS: To try to unmask this protective action, we compared brain monoamine levels in two strains of mice differing in HBO-sensitivity and their sensitivity to HBO after norepinephrine (NE) depletion by N-(2-chloroethyl)-N-ethyl-2-bromo benzylamine (DSP4). METHODS: Mice were exposed to 6 ATA O2 for 90 min (C57 strain) and 24 min (HBO-sensitive CD1 strain) so that 50% of mice of each strain had preconvulsive symptoms when decompressed and 50%), had one generalized convulsion. After microwave sacrifice, monoamines in the cerebral cortex, the striatum and the brainstem were analyzed. Another series studied the effect of DSP4 on the delay to symptoms of these HBO)-exposed mice. RESULTS: NE normoxic levels in the striatum were greater in the HBO-sensitive CD1 than in the C57 strain. Under HBO, NE levels in the striatum and the cortex of CD1 fell without any concomitant increase in its metabolite whereas in the C57 strain, NE decreased less and its metabolite increased. There was no strain difference and little change in the NE levels in the brainstem. The increase in toxicity induced by DSP4 was highly significant in both strains; moreover C57 strain was more affected than CD1. CONCLUSION: Monoamine depletion before HBO aggravates HBO neurotoxicity. As monoamine deamination is known to be toxic, this demonstrates that monoaminergic activation is protective. The greater toxicity of DSP4 in the C57 strain suggests the involvement of monoamines in the strain-differential susceptibility to HBO. The lower sensitivity of CD1 mice to DSP4 may be related to a combination of less NE activation under HBO that in C57 and greater activation of peroxidation and amino acids in CD1 sensitive strain.

Simultaneous measurement of monoamines, their metabolites and 2,3- and 2,5-dihydroxybenzoates by high-performance liquid chromatography with electrochemical detection. Application to rat brain dialysates.

A reversed-phase chromatographic method with electrochemical detection was developed for the simultaneous determination of 2,3- and 2,5-dihydroxybenzoates, indicators of in vivo hydroxyl free radical formation, monoamines (NE, DA, 5-HT) and their metabolites (MHPG, DOPAC, HVA, 3MT, 5-HIAA). Linearity was observed from 10 pg to 10 ng injected. Reproducibility is correct (C.V. about 9%) except for 3MT and 5-HT. The limit of detection for almost all products was about 20 pg injected on the column. An application of this method in the study of the neurotoxicity of high pressure oxygen in rat is described. The limit of quantification for all compounds was 5 ng/ml except for HVA (10 ng/ml). Some basal levels DA, 5-HT, 5-HIAA, HVA, DOPAC, 3MT, 2,5-DHBA and 2,3-DHBA in microdialysates coming from striatum of normoxic restrained rats are given.

A longitudinal study of lung impairment in patients with primary Sjögren's syndrome.

OBJECTIVE: A longitudinal evaluation of lung involvement in primary Sjögren's syndrome (SS). METHODS: Eighteen non-smoking women fulfilling the European criteria for primary SS were followed for 55 months (range 26-137 mos.). These were consecutive patients with exclusion for current smokers and patients with lung diseases. Every patient underwent clinical examination, chest radiographs and lung function tests (spirography, flow/volume loop and CO lung diffusing capacity measurements). No patient was given any immunosuppressive or mucolytic therapy. RESULTS: Cough, dyspnea on exertion and recurrent bronchitis were observed in 50, 40 and 20% of the patients respectively and their frequency did not change with time. Chest radiographs were and remained normal. At presentation, lung volumes and diffusing capacity were in the normal range, whereas expiratory flows in the small airways tended to be in the low range. With time, the peak expiratory flow (PEF) significantly increased (95.8 +/- 4.6 v 103.5 +/- 4.6, mean +/- SE, % of predicted, Wilcoxon, p < 0.05) whereas the lung transfer factor for CO (TLCO) and the transfer coefficient (KCO = TLCO/alveolar volume) decreased (92.9 +/- 4.0 v 87.0 +/- 4.0 and 89.7 +/- 2.4 v 84.2 +/- 2.6 respectively, p < 0.05 for both). The TLCO decrease, corrected for the duration of follow-up, correlated with the titers of IgA circulating immune complexes (CIC) at presentation and to a lesser extent with the occurrence of cough. CONCLUSION: During the follow-up of these primary SS patients, respiratory symptoms did not change, the recurrent respiratory infection rate was low, and no cases of pulmonary hypertension or lymphoma was observed. The diffusion capacity decrease was associated with IgA CIC titers at presentation. This impairment could contribute to dyspnea during its evolution over a lifetime but is too slight to explain the dyspnea on exertion seen in most of our patients.

Amino acids and ammonia in the cerebral cortex, the corpus striatum and the brain stem of the mouse prior to the onset and after a seizure induced by hyperbaric oxygen.

The contents of amino acids (AA) and ammonia (NH3) were measured in corpus striatum, brain stem and cerebral cortex of two strains of mice exposed to hyperbaric oxygen (HBO). Mice of the HBO-sensitive strain (CD1) were exposed to 600 kPa O2 for 24 min versus 90 min for mice of the normal C57 strain, so that 50% of the mice in both strains developed a generalized convulsion. In the cortex of exposed but unconvulsed (EXUN) C57 mice, the contents of taurine, glutamine and NH3 increased while that of GABA decreased when compared to control mice. In the CD1 mice, NH3 content was increased while that of Asp decreased. After a convulsion, NH3 was increased in both strains, the AA contents returned to normal in C57 but Asp remained low in CD1 mice. Somewhat similar changes occurred in the striatum except that NH3 levels were less affected while GABA ones were significantly decreased in the CD1 mice exposed to HBO, whether convulsed or not. In the EXUN brain stem, Asp and Glu contents decreased. These decreases were greater in C57 on a percentage basis than in CD1 mice. GABA content was decreased in the C57 strain. After a convulsion, Asp and Glu levels remained low and NH3 accumulated in CD1 whereas in C57 only the Glu level was decreased. The cortical and striatal changes may indicate a lesser GABA supply in C57 strain and some Asp release in CD1 strain. In the brain stem of both strains, Asp and Glu release is possible in addition to GABA in C57 strain.(ABSTRACT TRUNCATED AT 250 WORDS)

[Normal values of respiratory function tests. Safety of normalized regression equations]. / Normalité des explorations fonctionnelles respiratoires. Sécurité des équations de régression "normatrices".

A frequent question in lung function testing is the extent of the margin of error in the measurements. Is the confidence interval (CI) of the usual summary equations for reference values larger than the sum of every possible error including interindividual variations and measurement errors which come from the apparatus, the technician and the patient? The analysis of the data of several authors including our data (lung function laboratory of Brest University hospital) leads to the conclusion that the summary equations of Quanjer et al. (1993) may be used safety as the CI is larger than the sum of all errors. However, this is only true if lung function testing is performed in optimal conditions, i.e. with frequently checked and carefully calibrated apparatus used by professional technicians in cooperating patients.

Effect of hyperbaric oxygen on prostaglandin and thromboxane synthesis in the cortex and the striatum of rat brain.

The effect of a previous exposure to hyperbaric oxygen (HBO) on the synthesis capacity of prostaglandin (PG) and thromboxane (TX) was investigated in the brain of male rats. Three groups of rats were used: 1. Neurotoxic HBO (n = 11): The rats were exposed to sixfold the atmospheric pressure (101.3 kPa), i.e., 6 absolute atmospheres (ATA), of pure O2 up to the first convulsion (6 ATA O2); 2. Mild hyperoxia (n = 10): The rats were exposed to compressed air at the same absolute pressure and for a similar time than that of the neurotoxic HBO group (here PO2 is 1.26 ATA); 3. Normoxia at atmospheric pressure (PO2 is 0.21 ATA) for control. There was no convulsion in groups 2 and 3. Decompression of the high pressure groups lasted 15 min. After decapitation, samples of the frontal cortex and the striatum were taken, weighed, washed, and then incubated in Krebs-Ringer bicarbonate for 1 h. The release of eicosanoids in the medium was determined by enzyme immunoassay. Mild hyperoxia only significantly reduced in the striatum the release of 6-keto-PGF1 alpha (1.3 +/- 2.4 vs 10.9 +/- 6.6 pg/mg wet tissue, p < 0.001; mean +/- SD) and PGE2 (3.2 +/- 2.7 vs 7.8 +/- 6.5 pg/mg wet tissue, p < 0.05), whereas TXB2 did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of one hyperbaric oxygen-induced convulsion on cortical polyamine content in two strains of mice.

In rat striatum, after one hyperbaric oxygen (HBO)-induced convulsion, polyamine changes are found that could promote N-methyl-D-aspartate (NMDA) activation. In the HBO-sensitive CD1 mouse, unlike in the common C57 strain, there is some support for NMDA activation after the HBO seizure. We measured PA cortical content before and after the first HBO-induced convulsion (about 608 kPa O2) in CD1 and C57 strains. Putrescine, spermidine and spermine were dansyl derived and analysed by HPLC. Exposure to HBO significantly increased putrescine content only in CD1 though a similar trend was observed in C57. No further increase was observed after convulsion whatever the strain. There were no significant changes in spermidine or spermine to support NMDA activation. Therefore, putrescine increase in CD1 cortex could reflect the free radical formation that is known to be greater in CD1 than in C57 mouse. Attempts to increase putrescine levels before HBO exposure hastened HBO-induced convulsion, less than spermidine or spermine. Because of physiological polyamine interconversion, additional experiments with indirect manipulation of putrescine levels and study of their time-course would precise these preliminary reports on putrescine and HBO.

Locally deposited but not inhaled frusemide reduces nasal potential difference in healthy subjects.

Previous publications suggest that prolonged inhalation of frusemide (F) does not cause a fall in the nasal transepithelial potential difference (PD) whereas locally deposited F does. In an attempt to reconcile these observations, we have measured the effect of inhalation through the nose and local deposition of F, amiloride (A), bumetanide (B) and salbutamol (S) on nasal PD in 7 healthy male volunteers in a randomised, double blind study. Solutions of drugs ranging from 10(-6) M to 10(-3) M (3 x 10(-8) M to 3 x 10(-5) M for B) in phosphate buffered saline 0.5 ml (PBS) were sequentially deposited in both nostrils, and nasal PD was measured 5 min after each dose. In 10 further volunteers, 10(-2) M solutions of A, F and S (3 x 10(-4) M for B) 5 ml were nebulised through the nose for 15 min, when nasal PD was measured. Resting PD was similar in the left and right nostrils averaging -17.1 mV (lumen negative). Placebo, inhaled of deposited B and S, and inhaled F did not change nasal PD. Topically deposited F significantly lowered PDmax in a dose-dependent manner [10(-4) M, -12% from baseline; 10(-3) M, -24%] as did the more potent A [10(-5) M, -19%; 10(-4) M, -31%; 10(-3) M, -47%]. Nebulised A (10(-2) M) had the same effect on nasal PD as deposited A (10(-4) M). The effects of locally deposited F and A (10(-3) M) on nasal PD were additive.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in striatal and cortical amino acid and ammonia levels of rat brain after one hyperbaric oxygen-induced seizure.

Changes in amino acids (AA) and ammonia were investigated in the cerebral cortex and striatum of rats after the following conditions: 1) one hyperbaric oxygen (HBO)-induced seizure (6 ATA O2); 2) exposure to 6 ATA air; and 3) exposure to atmospheric pressure (no seizures in both latter groups). Exposure to 6 ATA air produced no change with respect to atmospheric pressure. After HBO seizure, AA levels (except for gamma-amino butyric acid, GABA, and glutamine), with respect to 6 ATA air levels, were altered in the striatum with a concomitant rise in ammonia (+70%) at variance with the cortex. These changes could be explained by increased oxidative deamination in the striatum. Decrease in taurine content (-66%) in the striatum, where HBO lipoperoxidation exists, suggests an alteration of glial function leading to blockade of uptake and loss of released products in interstitial fluid. This pattern of change recalls the one seen in ischemic conditions, but cannot be confirmed in the absence of measurements of extracellular amino acid levels under HBO conditions. The maintenance in the level of GABA would favor its role in controlling seizure. In the cortex, only a few AA levels decreased, along with a nonsignificant trend for ammonia to increase. The remaining abnormalities in the striatum, after the first HBO seizure, may explain the already known repetition of seizures in continuously exposed animals and are consistent with previous data on the important role of the striatum.

[External resistances and dyspnea. Value of the study of flow-volume loops]. / Résistances externes et dyspnée. Intérêt de l'étude de la boucle débits/volumes.

Breathlessness induced by external resistances (diaphragms with orifice size of 20, 15, 10, 7.5 and 5 mm) introduced in the ventilatory circuit of a spirometer and the corresponding parameters of a maximal flow-volume loop have been studied. 10 healthy subjects (5 men, 5 women), free from any acute or chronic cardiorespiratory disease, volunteered for this study. The results showed that the breathlessness (severe or moderate) was especially correlated with the decrease in peak flows, peak inspiratory flow (PIF) more than peak expiratory flow (PEF): when breathlessness was moderate, PIF was more decreased than PEF, -35% and -28% respectively; when breathlessness became severe, PIF also decreased more than PEF, -60% and -50% respectively; forced vital capacity (FVC) never changed and maximal expiratory flows at 50% and 25% of FVC were only slightly modified despite obvious breathlessness. The increase in diaphragmatic activity seemed more implicated than the activation of expiratory muscles in the genesis of breathlessness. PIF more than the commoner PEF could be a useful marker of the breathlessness perceived by the patient during acute bronchial obstruction (asthma).

The influence of one hyperbaric oxygen-induced seizure on brain eicosanoid content.

The levels of prostaglandin F1 (6-keto-PGF1 alpha), thromboxane B2 (11-dehydro-TxB2), and peptidoleukotriene C4 (LTC4) were measured (acetylcholinesterase immunoassay) in the frontal cortex (FC) and the striatum (SA) of the rat brain to study the possible role of eicosanoids in seizures induced by hyperbaric oxygen (HBO). The rats were exposed to (1) hyperbaric oxygen (HBO, 6 ATA O2) up to the first seizure (2) compressed air (6 ATA air, i.e., approximately equal to 1.25 ATA O2) or (3) atmospheric pressure (1 ATA air, i.e., 0.21 ATA O2); there was no seizure in groups 2 and 3. Transition from 6 ATA to atmospheric pressure was obtained in 15 min; the rats were then decapitated and their heads frozen in liquid nitrogen before extraction and analysis of prostanoids. Whatever the conditions, cortical levels of 6-keto-PGF1 alpha and 11-dehydro-Tx B2 are higher than striatal levels; considering the same area, 11-dehydro-Tx B2 and LTC4 concentrations were not significantly different whatever the condition, but there is a trend for lower 6-keto-PGF1 alpha levels in FC after HBO seizure. Biochemical mechanisms are discussed. Eicosanoids do not seem to play a major role in HBO seizures, although some modifications of their metabolism may take place.

Ammonia and monoamine concentrations in two brain areas in rats after one hyperoxic seizure.

Monoamines (catecholamines, serotonin, and metabolites) and ammonia were studied within two areas of the rat brain--the frontal cortex (FC) and the striatum (SA)--after exposure to hyperbaric oxygen (HBO) at 6 ATA up to the first seizure. An increase of norepinephrine (NE), dopamine (DA), and metabolites (HVA, DOPAC) measured by the HPLC/EC method were found in SA with a parallel increase of ammonia at variance with the FC where no monoamine changes, but a slight increase of ammonia, were found. Blood ammonia did not change with HBO. So, 20 min after one HBO seizure, there are regional differences in the brain, which are consistent with the previous findings of an SA start of electrocortical abnormalities at the onset of a seizure. Elevated DA, and possibly NE, levels may contribute to the accumulation of ammonia in the brain. During prolonged HBO exposure, this rise of ammonia could be one of the mechanisms involved in the relapse of seizures. It might also be implicated in initiation of the first seizure. By their situations and contents, SA glial cells could play an important role in brain HBO susceptibility.

CO2 chemoreflex drive of ventilation in man: effects of hyperoxia and sex differences.

CO2 single breaths have been performed in 7 men and 7 women in conditions of normoxia (FICO2 congruent to 0.13; FIO2 congruent to 0.21; FIN2 congruent to 0.66) and of hyperoxia (FICO2 congruent to 0.13; FIO2 congruent to 0.87). Ventilatory responses of the subjects and modifications of breathing pattern in the course of the CO2 tests were also explored in the two conditions. The results (mean +/- SEM) show that, whatever the oxygenation, men and women exhibit the same ventilatory response during a CO2 test from a qualitative point of view but with a smaller intensity in women (men: 0.37 +/- 0.088 LBTPS.min-1.Torr-1; women: 0.15 +/- 0.025 LBTPS.min-1.Torr-1; p less than 0.05). Considering men and women together, CO2 tests induced an increase of minute volume VE (p less than 0.001), VT (p less than 0.01) and rate of breathing (NS) but this response is decreased in hyperoxic conditions (p less than 0.05) mainly in men (men: 0.19 +/- 0.043 LBTPS.min-1.Torr-1; women: 0.11 +/- 0.023 LBTPS.min-1.Torr-1). These results show that sensitivity to transient hypercapnia and its interaction with hyperoxia are weaker in women than in men.

[Abnormalities of respiratory function in civil defence firefighter-submarine divers. Respective role of diving and occupational exposure related to occupational firefighter's functions]. / Anomalies de la fonction respiratoire chez les pompiers-plongeurs sous-marins de la protection civile. Rôles respectifs de la plongée et des agressions liées aux fonctions de pompier professionnel.

Lung function was studied in 20 firemen-submarine divers (mean age 36 +/- 1.2 years) of the French civil defence undergoing the medical check-up compulsory for professional divers (lung function tests are not systematically performed in ordinary firemen). Compared with the CECA standards: (1) vital capacity (VC) was increased, residual volume (RV) was decreased and total lung capacity (TLC) was unchanged; (2) with the exception of peak respiratory flow, all expiratory flow values (FEV1, MEF50, MEF25) were decreased; (3) the permeability factor (KCO) was decreased. These functional abnormalities were moderately worse in subjects who smoked. Some abnormalities (increased VC, decreased RV) are typical of diving activities, but the deterioration of effort-dependent expiratory flow values and alveolar-capillary diffusion must be ascribed to specific nuisances (fumes, polluants, toxic substances) associated with fireman's activities. Monitoring lung function in all professional firemen therefore seems to be necessary, if not indispensable.

Effects of maximal breath holding on maximal expiratory flows.

Effects of breath holdings (BH) on bronchomotor tone, maintained until their breaking points, have been studied using maximal expiratory flow volume curves (MEFVC). BHs have been performed either at high lung volume (total lung capacity, EIBH) or at low lung volume (residual volume +250 ml, EEBH), an inspiratory manoeuvre immediately preceding the MEFVC. The results show that: (1) EIBH induces a significant increase of expiratory flow at 25% of FVC; (2) EEBH induces a significant and constant decrease of expiratory flows at 50% and 25% of FVC. The same modifications were recorded after inhalation of 400 micrograms of Fenoterol or 80 micrograms of Ipratropium bromide. The observed results are suggestive of mechanical effects of BH on expiratory flows. After EIBH airway hysteresis dominates over lung hysteresis, with opposite effects after EEBH.

Ventilatory responses to hypoxia in healthy subjects: a comparison between young children and adults.

Ventilatory responses and breathing patterns during acute hypoxia have been studied at sea level in healthy subjects (8 children, 8 adults). While breathing ambient air it appears that, compared to adults, children hyperventilate when ventilation is standardized to body mass unit. During hypoxia, ventilatory strategy differs with age: when adults essentially increase tidal volume (VT), children increase VT and ventilatory frequency (fr). The ventilatory steady-state response to hypoxia is lesser in children than in adults, that is to say, children have a lower O2 ventilatory sensitivity. These results, which show that adults and children have qualitatively and quantitatively different ventilatory responses to hypoxia, are interpreted in terms of the ability to displace gaseous volumes.