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Biomedical subjects

B Hannhart

Publications and source records attributed to B Hannhart.

At least 37 records · Page 2Linked to original sources
PubMed1992

Nalbuphine analgesia preserves ventilation after thoracotomy despite a reduction in inspiratory drive.

The respiratory effects of analgesia with nalbuphine were studied in 9 patients after thoracotomy. The pain score was measured by a visual analogue scale. Ventilatory pattern and occlusion pressure (P0.1) were studied during spontaneous breathing and during CO2 rebreathing, before and 0.5, 1, 2.5, 3.5 and 6 h after a 0.3-mg.kg-1 dose of intravenous nalbuphine. Compared to baseline values obtained before the injection, nalbuphine produced a decrease in the pain score (p < 0.001) during the 6-hour experiment period. In spontaneous breathing, P.01 was reduced by 15% in 1 h and remained decreased during 3.5 h (p < 0.05), whilst PaCO2 and ventilation (VE) remained unchanged. The P0.1 responsiveness to CO2 was decreased from 0.5 to 2.5 h after the nalbuphine injection (p < 0.05), but the VE responsiveness to CO2 was reduced only after 1 h (p < 0.01). This study shows that, while post-thoracotomy pain was reduced by analgesia, neuromuscular inspiratory drive and chemosensitivity to CO2 were weakened, without any change in spontaneous ventilation. A partial improvement in the thoracopulmonary mechanics induced by the reduction in chest pain could explain the maintenance of ventilatory level in spite of a decreased neuromuscular inspiratory drive.

Analysis of Variance↗
PubMed1991

Influences of gender and sex hormones on hypoxic ventilatory response in cats.

Hypoxic ventilatory response (HVR) is known to be increased by female as well as male sex hormones, but whether there are differences in HVR between men and women remains unclear. To determine whether gender differences exist in HVR, we undertook systematic comparisons of resting ventilation and HVR in awake male and female cats. Furthermore to explore the potential contribution of sex hormones to gender differences observed, we compared neutered and intact cats of both sexes. Resting ventilation differed among the four groups, but differences disappeared with correction for body weight. Intact females had a lower end-tidal PCO2 than intact male cats (females: 31.6 +/- 0.4 Torr vs. males: 33.6 +/- 0.4 Torr, P less than 0.05), indicating an increased alveolar ventilation per unit CO2 production. HVR expressed as the shape parameter A was similar among the four groups of animals. However, baseline (hyperoxic; end-tidal PO2 greater than 200 Torr) minute ventilation [VI(PO2 greater than 200)] differed among the groups. Therefore we normalized HVR by dividing the shape parameter A by VI(PO2 greater than 200) to compare the relative hypoxic chemosensitivity among the various groups of animals. In addition, we further normalized HVR for body weight, because body size influences ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Reliability of six pulse oximeters in chronic obstructive pulmonary disease.

Six pulse oximeters with finger probes were studied in three groups of 17 hypoxemic patients with COPD aged 50 to 75 years. Transcutaneous arterial oxygen saturation (SpO2) was measured with the Nellcor N101 (oximeter 1a), the Ohmeda Biox III (oximeter lb), the Nellcor N200 (oximeter 2a), the Critikon Oxyshuttle (oximeter 2b), the Radiometer Oxi100 (oximeter 3a), and the Ohmeda Biox 3700 (oximeter 3b). The SpO2 was compared with SaO2 measured in simultaneously withdrawn samples of arterial blood (Radiometer OSM2) at three 20-minute steady-state levels of FIO2 ranging from 0.21 to 0.40 (SaO2, 62 to 100 percent). The bias (mean SpO2-SaO2 difference) and the error in precision (SD of the differences) were both below 4 percent for instruments 1a and 1b and remained below 1.2 and 3 percent, respectively, for the others. A good agreement between SpO2 and SaO2, as reflected by the Bartko intraclass correlation coefficient, was observed in instruments 2a, 3a, and 3b. The individual relationships between SpO2-SaO2 differences and SaO2 appeared to be linear and parallel. With four instruments (1a, 1b, 2a, and 2b), the mean slope of this relationship was negative, showing a systematic instrumental error: the lower the SaO2, the larger the overestimation of SaO2. The scattering of the data (precision) principally reflects a subject source of error. In most instruments a technical adjustment could greatly improve instrumental errors and accuracy. The correction of the errors due to between-subject variation would require a system of calibration adjustable by the users to each individual.

Aged↗
PubMed1991

Accuracy and precision of fourteen pulse oximeters.

Two sets of seven pulse oximeters (Criticare CSI-502; Nellcor-N200; Datex-Satlite; Physio-Control-Lifestat 1600; Critikon-Oxyshuttle; Ohmeda-Biox 3700; Ohmeda-Biox 3740; Radiometer-Oxi; Spectramed-Pulsat; Kontron-7840; Biochem-Ox2000; Invivo-4500; Engström-EOS; Novametrix-505) were studied in two groups of eight healthy subjects, aged 26-50 yrs. The transcutaneous oxygen saturation (SpO2) was compared with arterial oxygen saturation (SaO2) measured in simultaneously with drawn blood samples (OSM2 Radiometer) at four 20 min steady-state levels of inspired oxygen fraction (FIO2) (0.21, 0.10, 0.08 and 0.07; SaO2 99-55%) in a conditioned chamber. Both the error in accuracy (mean SpO2-SaO2 difference), and the error in precision (SD of the differences) remained less than 3% for the two highest FIO2 levels (SaO2 greater than 83%) but, during deeper hypoxia, they were increased to 8% and 5%, respectively. An instrumental systematic bias affected accuracy in particular. We concluded that a good agreement between SpO2 and SaO2, as reflected by the Bartko's intraclass coefficient, was observed in nine instruments.

Adult↗
PubMed1990

Effects of estrogen and progesterone on carotid body neural output responsiveness to hypoxia.

Pregnancy increases ventilatory and carotid body neural output (CBNO) responsiveness to hypoxia in cats (J. Appl. Physiol. 67: 797-803, 1989). To determine whether progesterone and estrogen stimulated hypoxic ventilatory and CBNO responsiveness, we studied 24 castrated male cats before and after 1 wk of placebo, estrogen, progesterone, or estrogen plus progesterone treatment. Estrogen plus progesterone treatment decreased end-tidal PCO2 (-3.8 +/- 0.8 Torr) and increased hypoxic ventilatory responsiveness, whereas estrogen or progesterone alone had no effect. Animals receiving progesterone alone or in combination with estrogen had higher CBNO responsiveness than placebo or estrogen-treated animals (shape parameter A = 45 +/- 7 vs. 27 +/- 4, P less than 0.05). However, the group treated with estrogen plus progesterone did not have greater CBNO responsiveness to hypoxia than the group receiving progesterone alone. The cross plot of the simultaneously measured CBNO and ventilation during progressive hypoxia revealed a greater slope in the estrogen-treated than in the placebo animals, suggesting that estrogen treatment increased central nervous system transduction of CBNO into ventilation. Thus the data taken together suggested that progesterone and estrogen had a combination of peripheral (carotid body) and central sites of action such that the administration of both hormones together had a more consistent stimulatory effect on hypoxic ventilatory responsiveness than either hormone alone.

Animals↗
PubMed1989

Influence of pregnancy on ventilatory and carotid body neural output responsiveness to hypoxia in cats.

Pregnancy increases ventilation and ventilatory sensitivity to hypoxia and hypercapnia. To determine the role of the carotid body in the increased hypoxic ventilatory response, we measured ventilation and carotid body neural output (CBNO) during progressive isocapnic hypoxia in 15 anesthetized near-term pregnant cats and 15 nonpregnant females. The pregnant compared with nonpregnant cats had greater room-air ventilation [1.48 +/- 0.24 vs. 0.45 +/- 0.05 (SE) l/min BTPS, P less than 0.01], O2 consumption (29 +/- 2 vs. 19 +/- 1 ml/min STPD, P less than 0.01), and lower end-tidal PCO2 (30 +/- 1 vs. 35 +/- 1 Torr, P less than 0.01). Lower end-tidal CO2 tensions were also observed in seven awake pregnant compared with seven awake nonpregnant cats (28 +/- 1 vs. 31 +/- 1 Torr, P less than 0.05). The ventilatory response to hypoxia as measured by the shape of parameter A was twofold greater (38 +/- 5 vs. 17 +/- 3, P less than 0.01) in the anesthetized pregnant compared with nonpregnant cats, and the CBNO response to hypoxia was also increased twofold (58 +/- 11 vs. 29 +/- 5, P less than 0.05). The increased CBNO response to hypoxia in the pregnant compared with the nonpregnant cats persisted after cutting the carotid sinus nerve while recording from the distal end, indicating that the increased hypoxic sensitivity was not due to descending central neural influences. We concluded that greater carotid body sensitivity to hypoxia contributed to the increased hypoxic ventilatory responsiveness observed in pregnant cats.

Animals↗
PubMed1989

Small airways dysfunction in asymptomatic ex-smokers.

'Conventional' (lung volumes, airway conductance, CO transfer factor) and 'small-airway dysfunction' (single-breath N2 washout, maximal expiratory flows with air and a helium-oxygen mixture) tests were performed in a group of asymptomatic male ex-smokers (n = 20) with normal spirometry and compared to those of a similar group of middle-aged nonsmokers (n = 41). The study group had a mean life-long consumption of 13.2 +/- (SD) 8.8 pack-years and had stopped smoking 1-21 years ago, mean 7.3 +/- (SD) 5.8 years. Among the conventional tests, a minimal increase in residual volume and residual volume/total lung capacity ratio was found. Ex-smokers had a steeper phase III slope, a higher closing volume/vital capacity ratio, lower forced flows with air and a higher volume of isoflow, but neither difference between the group means was significant. There was a trend to more abnormal small-airway tests as a function of increased smoking, but only the correlation between percent of predicted closing volume and pack-years reached significance (r = +0.51, p less than 0.05). We conclude that small-airway function normalizes in the long term in most ex-smokers if they become asymptomatic, with less than 10% still having abnormal results years after they stopped smoking.

Adult↗
PubMed1989

[Physiology of ventilatory regulation during sleep].

During light slow-wave sleep, ventilation is principally regulated by automatic metabolic control system. An instability in the respiratory control may be the predominant disturbance leading to very irregular or periodic breathing. During deep sleep, ventilation is progressively more stable. During REM sleep, automatic regulation is abolished and ventilation is particularly dependent on the compartmental control system. The reduction in airways and respiratory muscles tone favors the occurrence of obstructive apneas. The elevation in arousal threshold leads prolongation of the obstructive events.

Arousal↗
PubMed1988

Thoracic gas volume measurements in chronic obstructive pulmonary disease by low frequency ambient pressure changes.

The validity of a new method for measuring thoracic gas volume (Vtg) was studied in 18 bronchitic patients with mild to severe airway obstruction. The method entailed submitting the subject to very slow sinusoidal variations of ambient pressure (delta Pam) and studying the relationship between delta Pam and the resulting gas displacement at the mouth (delta Vaw): Vtgapc = PB.delta Vaw/delta Pam.cos phi, where PB is barometric minus alveolar water vapor pressure, and phi is the phase angle between Pam and Vaw. delta Pam of 40 cm H2O at 0.05 Hz were achieved by placing the subject in a 410-I body chamber connected to a large stroke volume reciprocating pump. Pam and Vaw were processed digitally by Fourier transform to obtain their amplitude ratio and phase angle at the frequency of interest. Vtg was also measured by body plethysmography (Vtgplet) during slow panting maneuvers (0.79 +/- 0.19 Hz) and also in order to detect any artifactual frequency dependence at a higher panting frequency (1.71 +/- 0.27 Hz); the agreement between the 2 estimates in all subjects (r = 0.975) suggested that Vtgplet could be taken as a valid reference. Functional residual capacities derived from Vtgapc and Vtgplet were not significantly different (5.113 +/- 1.198 versus 5.260 +/- 1.328 L) and were highly correlated (r = 0.915). Intermethod differences averaged 1.7 +/- 10.5% and were not significantly correlated to functional indices. We conclude that the new method provides accurate Vtg values in patients with chronic airway obstruction.

Adult↗
PubMed1987

Computerized single-breath nitrogen washout in children: variability and reproducibility.

The variability, short-term (1 hour) and long-term (2 weeks) reproducibility of the variables derived from the single-breath N2 test were evaluated in a group of 56 healthy children aged 10 to 16 years with a computerized system. The variability was low for vital capacity and total lung capacity (coefficient of variation less than 3%), moderate for residual volume and phase III N2 slope (9 and 13%) and very high for closing volume (more than 50%). A closing volume could not be identified by the computer algorithm in 18.3% of the trials. The reproducibility of the variables was satisfactory both at 1 hour and at 2 weeks, with the exception of the closing volume, whose increase at 2 weeks seemed to be due to methodological factors. We conclude that reliable results of static lung volumes and phase III N2 slope, but not of closing volume, may be obtained in children by a computerized system in epidemiological studies.

Adolescent↗
PubMed1987

Measurement of thoracic gas volume by low-frequency ambient pressure changes.

When the whole body is exposed to sinusoidal variations of ambient pressure (delta Pam) at very low frequencies (f), the resulting compression and expansion of alveolar gas is almost entirely achieved by gas flow through the airways (Vaw). As a consequence thoracic gas volume (TGV) may be computed from the imaginary part (Im) of the delta Pam/Vaw relationship: TGV = PB/[2 pi f X Im(delta Pam/Vaw)], where PB is barometric minus alveolar water vapor pressure. The method was tested in 35 normal subjects and compared with body plethysmography. The subjects sat in a chamber connected to a large-stroke-volume reciprocating pump that brought about pressure swings of 40 cmH2O at 0.05 Hz. delta Pam and Vaw were digitally processed by fast Fourier transform to extract the low-frequency component from the much larger respiratory flow. Total lung capacities (TLC) obtained by ambient pressure changes and by plethylsmography were highly correlated (r = 0.959, p less than 0.001) and not significantly different (6.96 +/- 1.38 l vs. 6.99 +/- 1.38). TLC obtained by ambient pressure changes were not influenced by lowering the frequency to 0.03 Hz, adding an external resistance at the mouth, or increasing abdominal gas volume. We conclude that the method is practical and in agreement with body plethysmography in normal subjects.

Adolescent↗
PubMed1987

[Evaluation of the performance of 2 mini-flow meters].

Two mini-peak flow meters, the Airmed (mini-Wright) and the Medicheck (Pulmonary Monitor), were assessed against a reference electronic spirometer (Spiromatic, based on a pneumotachograph, integrator and an Apple II computer) in a series of 10 healthy subjects and 20 patients with chronic obstructive lung disease. The devices to be tested were mounted in series with the reference instrument; each subject did five trials. It was found that the Airmed instrument overestimated the flows up to 9 l X s-1 (i.e. in patients, average difference 0.86 l X s-1, p less than 0.001; in healthy subjects, average difference 0.35 l X s-1, p less than 0.001). The correlation with the results of the reference instrument was high (r = 0.992) in healthy subjects, whose regression slope was less than unity (0.763). In patients the correlation was satisfactory (r = 0.974), and the slope close to 1 (1.05). The Medicheck overestimated slightly the results of patients (difference 0.17 l X s-1, p less than 0.01); in normal subjects the overestimation was present only below 10 l X s-1 and the difference with the reference instrument nonsignificant (average 0.19 l X s-1). The results were closely related to those of the reference spirometer in both healthy subjects (r = 0.960) and patients (r = 0.936). As for the first instrument the slope of the regression was below 1 in healthy subjects (0.751) and practically one (1.01) in patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Comparison between ventilatory and mouth occlusion pressure responses to hypoxia and hypercapnia in healthy sleeping man.

Ventilatory and mouth occlusion pressure (P0.1) responses to progressive isocapnic-hypoxia and hyperoxic-hypercapnia were compared in eleven healthy sleeping men during the same night. Hypoxic and hypercapnic responses were determined during wakefulness, non-rapid and rapid-eye-movement sleep. The following parameters were measured: minute ventilation (VE), tidal volume (VT), 'duty cycle' (TI/TT), mean inspiratory flow rate (VT/TI) and P0.1, an index of the neuromuscular inspiratory drive. To allow a direct comparison between the two types of chemostimuli, responses were characterized by the value of the different parameters at 'equivalent' levels of hypoxia and hypercapnia, i.e., at levels which produced the same P0.1 during wakefulness: an oxyhaemoglobin saturation (Sao2) of 94% during the isocapnic-hypoxic tests (PETCO2 = 42.5 +/- 1.2 mmHg) was found to be equivalent to a PETCO2 of 47.4 +/- 3.7 mmHg during hypoxic-hypercapnic tests. For both tests, the arousal levels of the stimulus and of P0.1 were similar in all sleep stages. Sleep did not significantly modify P0.1 or breathing pattern responses to hypoxia (Sao2 = 94%). In contrast, at the 'equivalent' level of hypercapnic stimulation, P0.1 (P less than 0.05) and VE (P less than 0.01) responses were significantly impaired, particularly in REM sleep, with a decrease in VT (P less than 0.01) and VT/TI (P less than 0.05) responses. The results suggest that CO2 intracranial receptor mechanisms are more affected by sleep than the O2 peripheral receptor activity.

Adult↗
PubMed1986

Tests of small airway dysfunction: their correlation with the "conventional" lung function tests.

"Sensitive" and "conventional" lung function tests were compared in a group of 114 males, aged 35-55 years, including healthy non-smokers, asymptomatic smokers with normal spirometry, and smokers with chronic bronchitis with or without mild airflow limitation. In non-smokers, with the exception of a MEF vs. FEV1 correlation, "sensitive" and "conventional" tests were independent of each other. In asymptomatic smokers the phase III slope and the closing volume were significantly related to FEV1, RV/TLC and CO transfer factor. In smokers with chronic bronchitis all the "sensitive" tests were related to the "conventional" tests (with the exception of the total lung capacity). Hyperinflation and CO transfer impairment suggest that early emphysema may accompany mucus hypersecretion in smokers.

Adult↗
PubMed1985

Evaluation of phase correction and low gas density to improve thoracic gas volume measurement.

We investigated two methods of decreasing the error on plethysmographic determinations of thoracic gas volume (TGV) related to cheeks movements during panting maneuvers: lowering gas density in the airways with an 80% He-20% O2 mixture and computing TGV from the in-phase component of the plethysmographic signal (TGVr). The methods were tested by measuring how TGV estimates varied when panting frequency was raised from 0.8 to 2.5 Hz during the same occlusion. The measurements were performed in 6 normal subjects and 12 patients with chronic bronchitis with and without cheeks support and when the airway was connected to an external device simulating an increased cheeks compliance. A small negative frequency dependence of TGV (delta TGV/delta f = -1.2 +/- 0.8%/Hz with cheeks support), most probably unrelated to upper airway walls, was found in normal subjects. Delta TGV/delta f was positive and algebraically larger in patients than in normals, reaching 2.2 +/- 3.4%/Hz without cheeks support and 11.8 +/- 8.0%/Hz with the additional cheeks. The latter value was only 20% smaller when computed on the basis of TGVr, demonstrating the limited usefulness of the phase-based correction. In contrast, breathing He-O2 decreased delta TGV/delta f to approximately 50% of its air value (P less than 0.01) and appears as an effective way to diminish the error in obstructive patients.

Adult↗