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Biomedical subjects

K R Chapman

Publications and source records attributed to K R Chapman.

At least 127 records · Page 7Linked to original sources
PubMed1985

Thoracoabdominal motion during hypercapnia, hypoxia, and exercise.

We measured, in 11 healthy volunteers, the contributions of rib cage and abdomen--diaphragm compartments to increased ventilation caused by hypercapnia, hypoxia, and exercise to determine whether different stimuli produce similar or different patterns of ventilation with respect to the motion of rib cage and abdominal compartments. Progressive hyperoxic hypercapnia and progressive isocapnic hypoxia were induced by rebreathing methods and graded exercise performed on a treadmill, and compartmental tidal volume (VT) was measured by respiratory inductive plethysmography. For each stimulus, the wide range of VT responses among individuals was determined primarily by the range of rib cage contributions to VT, the abdominal compartment VT response slopes accounting for less of this range. There were no significant differences between hypercapnia and hypoxia in either rib cage or abdominal contributions to ventilation (for both, p less than 0.3). However, exercise rib cage and abdominal contributions to ventilation were significantly different from those during chemically driven breathing: for the rib cage compartment, p less than 0.0001 and for the abdominal compartment, p less than 0.05. Whereas, in 8 of 10 subjects the rib cage contribution to VT during exercise was similar to or exceeded that during rebreathing, in 7 of 10 subjects the abdomen-diaphragm contribution fell below that measured during both hypercapnia and hypoxia. There was a significant correlation between hypercapnia and hypoxia in the VT contribution of each compartment at equivalent levels of ventilation (rib cage, p less than 0.0001; abdomen, p less than 0.0005), but there was no significant correlation in the VT contribution of either compartment between exercise and hypercapnia or exercise and hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1985

Effect of elastic loading on ventilatory pattern during progressive exercise.

Ventilatory responses to progressive exercise, with and without an inspiratory elastic load (14.0 cmH2O/l), were measured in eight healthy subjects. Mean values for unloaded ventilatory responses were 24.41 +/- 1.35 (SE) l/l CO2 and 22.17 +/- 1.07 l/l O2 and for loaded responses were 24.15 +/- 1.93 l/l CO2 and 20.41 +/- 1.66 l/l O2 (P greater than 0.10, loaded vs. unloaded). At levels of exercise up to 80% of maximum O2 consumption (VO2max), minute ventilation (VE) during inspiratory elastic loading was associated with smaller tidal volume (mean change = 0.74 +/- 0.06 ml; P less than 0.05) and higher breathing frequency (mean increase = 10.2 +/- 0.98 breaths/min; P less than 0.05). At levels of exercise greater than 80% of VO2max and at exhaustion, VE was decreased significantly by the elastic load (P less than 0.05). Increases in respiratory rate at these levels of exercise were inadequate to maintain VE at control levels. The reduction in VE at exhaustion was accompanied by significant decreases in O2 consumption and CO2 production. The changes in ventilatory pattern during extrinsic elastic loading support the notion that, in patients with fibrotic lung disease, mechanical factors may play a role in determining ventilatory pattern.

Adult↗
PubMed1985

Hemodynamic effects of inhaled ipratropium bromide, alone and combined with an inhaled beta 2-agonist.

Inhaled ipratropium bromide's reported lack of cardiovascular side effects has led to recommendations for its use as a bronchodilator in patients with coexisting cardiovascular disease and in combination regimens with adrenergic agents. To assess the hemodynamic effects of ipratropium, we monitored 10 volunteers by M-mode echocardiography following metered-dose ipratropium administered alone and with fenoterol. On 2 separate days, subjects were monitored for 90 min as they received either 160 micrograms of ipratropium or placebo in divided doses plus 400 micrograms of fenoterol at time 60 min. Following ipratropium alone, heart rate (HR) decreased 3 beats/min, a small but significant difference from placebo (p less than 0.04). Stroke volume (SV) and ejection fraction rose significantly (3 ml and 2%, respectively; p = 0.05) so that cardiac output (CO) was unchanged. By contrast, fenoterol alone (following placebo) produced marked increases in HR (13 beats/min), SV (14 ml), and CO (44%), with a marked fall in total peripheral vascular resistance (29%). Ipratropium administered before and with fenoterol had minimal additive effect. Although SV was slightly higher with the combination of drugs than with fenoterol alone (100.1 ml versus 93 ml; p = 0.05), CO was not significantly greater (6.9 L/min versus 6.4 L/min; p greater than 0.10). We conclude that metered-dose ipratropium alone has small and clinically unimportant hemodynamic effects and produces no clinically significant increases in the cardiovascular side effects of the bronchodilator regimen when given with fenoterol.

Adrenergic beta-Agonists↗
PubMed1984

Hemodynamic effects of an inhaled beta-2 agonist.

We examined echocardiographically in a single-blind crossover trial the circulatory effects of an inhaled selective beta 2-adrenergic bronchodilator, fenoterol. Eight healthy subjects were studied on the first and fourteenth day after randomly assigned therapy with either no drug or 400 micrograms fenoterol by metered dose inhaler four times a day. Heart rate (HR) and systolic (SBP) and diastolic (DBP) blood pressure responses to fenoterol were small (means +/- SE; HR: +4 +/- 1.3 bpm; SBP: +6 +/- 1.3 mm Hg; DBP: -3 +/- 1.4 mm Hg). In contrast, mean cardiac output increased 26% (1.1 +/- 0.2 l/min), accompanied by an 18% fall in total peripheral vascular resistance (-6 +/- 1.3 U), a 16% increase in stroke volume (+12 +/- 2.5 ml), and an 18% increase in the mean velocity of circumferential shortening (+0.2 +/- 0.04 c/s). Responses varied widely among subjects; maximum observed increase in cardiac output was 117% (+5.48 l/min) in one subject. There was no evidence to suggest development of tolerance to these hemodynamic effects, as the response of measured variables did not differ after 2 wk of regular fenoterol therapy. We conclude that selective beta 2-bronchodilators are not without potential for hemodynamically significant effects when taken by metered inhalers in recommended therapeutic doses and that the magnitude of such effects is underestimated when measured by HR and blood pressure changes.

Adult↗
PubMed1984

Thoracoabdominal motion during progressive isocapnic hypoxia in conscious man.

Respiratory frequency and separate rib-cage and abdomen-diaphragm compartmental tidal volume (VT) responses to progressive isocapnic hypoxia to a level of 75% O2 saturation (PO2 approximately 40 torr) were measured in eight healthy subjects in both seated and supine postures. Hypoxia was induced by a rebreathing technique and compartmental contributions to VT were measured by inductive plethysmography. The ventilatory, frequency and spirometric VT responses to hypoxia did not differ significantly between sitting and supine trials. The range of VT responsiveness to hypoxia among sitting individuals (0.71 +/- S.D. = 0.56% VC X % fall in Sa,O2(-1), where VC is vital capacity and Sa,O2 is arterial O2 saturation) was determined by both rib-cage (0.507 +/- S.D. = 0.378% VC X % fall in Sa,O2(-1) ) and abdomen-diaphragm (0.194 +/- S.D. = 0.178% VC X % fall fall in Sa,O2(-1) ) compartments. Among supine individuals the range of VT responsiveness to hypoxia (0.49 +/- S.D. = 0.45% VC X % fall in Sa,O2(-1) was determined equally by both rib-cage (0.27 +/- S.D. = 0.31% VC X % fall in SA,O2(-1) ) and abdomen-diaphragm (0.23 +/- S.D. = 0.29% VC X % fall in Sa,O2(-1) ) compartments. Thus, the VT response to progressive isocapnic hypoxia in conscious man is determined by both rib-cage and abdomen-diaphragm compartments regardless of posture.

Abdomen↗
PubMed1984

Pulmonary function in adolescents with mild idiopathic scoliosis.

Spirometric indices, lung volumes, maximum voluntary ventilation, and maximum inspiratory and expiratory pressures were measured in 44 adolescents with mild idiopathic scoliosis (spinal curvature less than 30 degrees). All were symptom free, but six (13.6%) showed a restrictive defect with forced vital capacity less than 80% of predicted. In 12 subjects (27.3%) maximum voluntary ventilation was reduced to less than 80% of predicted normal. Forced vital capacity was significantly correlated with maximum inspiratory pressure and with maximum expiratory pressure, measures of respiratory muscle strength, but was not related to the degree of thoracic curvature. When maximum inspiratory pressure and forced vital capacity were corrected for differences in body size these variables remained positively correlated, most significantly in the girls. These data indicate that ventilatory function may be impaired in mild, idiopathic scoliosis and that the force developed by the respiratory muscles is a more important determinant of this impairment than the radiologically determined degree of spinal curvature.

Adolescent↗
PubMed1984

Effect of posture on thoracoabdominal movements during CO2 rebreathing.

To determine whether the rib cage and abdomen-diaphragm contributions to tidal volume (VT) during CO2 rebreathing are affected by postural change, using respiratory inductive plethysmography, we measured in eight healthy volunteers the compartmental VT responses to progressive hypercapnia in both seated and supine postures. The ventilatory, frequency, and VT responses to CO2 of the total respiratory system were not significantly different between postures. VT responses, corrected for body size, ranged from 1.67 to 3.71% vital capacity (VC) X Torr-1 (mean 2.27) in seated subjects and from 1.08 to 3.79% VC X Torr-1 (mean 2.06), in supine subjects. In both postures, the VT response of the abdominal compartment was nearly uniform among subjects and independent of the total respiratory system VT response (slope = 0.091, r = 0.210 P greater than 0.3 seated; slope = 0.043, r = 0.077, P greater than 0.3 supine), whereas the VT response of the rib cage varied among subjects and was significantly correlated to the total VT response (slope = 0.815, r = 0.84, P less than 0.01, seated; slope = 1.125, r = 0.859, P less than 0.01, supine). Thus high tidal volume responses to CO2 rebreathing are determined largely by recruitment of the rib cage compartment in both seated and supine postures.

Abdominal Muscles↗
PubMed1984

Maximal inspiratory and expiratory pressures in adolescents. Normal values.

The measurement of maximal inspiratory and expiratory pressures at the mouth (MIP and MEP, respectively) provides a noninvasive clinical method for evaluating the strength of respiratory muscles. In an attempt to reconcile the widely divergent normal values reported in the literature for healthy adolescents, we have measured, using simple manometry, MIP and MEP in 112 white subjects, 76 adolescents and 36 healthy adults. For female adolescents the values for MIP and MEP were 76 +/- 25 and 86 +/- 22 cm H2O, respectively, and were significantly less than those for male adolescents (p less than 0.01), whose mean values were 107 +/- 26 and 114 +/- 35 cm H2O, respectively. Mean values for adolescents were comparable to values measured in adult control subjects, and for both adolescents and adults, mean values approximated the lower end of the previously reported ranges of normal values in healthy subjects. Thus, MIP and MEP in healthy adolescents are significantly greater in male subjects than female subjects, but are comparable to those of healthy adults of the same sex. Furthermore, these studies suggest that the choice of normal values for MIP and MEP must take into account significant methodologic differences among laboratories.

Adolescent↗
PubMed1983

Anticholinergic and sympathomimetic combination therapy of asthma.

The role of the anticholinergic drug, ipratropium bromide, in maintenance antiasthmatic therapy was evaluated in a double-blind crossover trial of three bronchodilator regimens: (1) inhaled ipratropium, placebo, and oral oxtriphylline; (2) inhaled fenoterol, placebo, and oral oxtriphylline; and (3) both inhaled ipratropium and fenoterol plus oral oxtriphylline. Twenty-two asthmatics were treated with all three regimens, each for 1 mo, allocated in random sequence. On the first and last treatment days of each month, spirometric measurements were performed before and 0.5, 1, 2, 3, 4, and 6 hr after administration of the test drugs. On the first treatment day of each month, all regimens produced significant bronchodilatation at 30 min after dose, an improvement that declined between 3 and 6 hr after dose. After continuous administration for 1 mo the two combinations employing fenoterol showed a decline in bronchodilator responsiveness from the initial treatment day, measured as the level of response (V50) or duration of response (FEV1, VC). Ipratropium plus oxtriphylline showed no such decline, suggesting the development of tolerance to long-term administration of fenoterol. Overall benefit at the end of 1 mo, measured as the area under the curves of FEV1, VC, or V50 vs time after dose, was greatest for the triple drug regimen. There were no differences in heart rate, blood pressure response, or side effects among the three treatments. It is concluded that when the anticholinergic drug ipratropium is administered concurrently with an inhaled beta 2 agonist and an oral theophylline derivative, increased bronchodilatation occurs with no detectable additional side effects.

Adolescent↗
PubMed1983

Inspiratory and expiratory resistive loading as a model of dyspnea in asthma.

20 ambulatory asthmatics were questioned regarding their perception of the dyspnea of acute asthmatic attacks; in particular, its relationship to the phase of respiration. 19 (95%) stated that inspiration was more difficult than expiration although 5 (25%) reported that they had been taught that the reverse was 'correct'. In order to explore further these observations, we applied psychophysical methods to determine the phase relationship of the conscious perception of resistive loads in healthy volunteers. 14 subjects of similar age and sex distribution to the asthmatics estimated numerically the magnitude of resistive loads applied in random sequence to either the inspiratory or expiratory arm of a low-resistance breathing circuit. The relationship between perceived magnitude (psi) and physical magnitude (phi) was described by Steven's law: psi = k phi n, where k and n are constants. The mean exponent (n) for inspiratory resistances was 0.69 +/- 0.28 (+/- SD) and for expiratory resistances was 0.51 +/- 0.27 (p less than 0.01 by two-tailed, paired t test). There was a positive correlation (r = 0.82) between inspiratory and expiratory exponents within individuals. In 12 of 14 subjects, the perceived magnitude of inspiratory loads was greater than the perceived magnitude of expiratory loads for all resistances greater than 10 cm H2O/l/s. At a load of 25 cm H2O/l/s, the inspiratory sensation of load exceeded the expiratory sensation in all subjects. Our findings that normal subjects scaled greater breathlessness with inspiratory versus expiratory flow resistive loads were consistent with the clinical observation that inspiratory, rather than expiratory difficulty contributed more to the dyspnea of asthma.

Adolescent↗
PubMed1983

The accuracy and response characteristics of a simplified ear oximeter.

We evaluated the accuracy and speed of response of a newly available, lightweight, and relatively inexpensive ear oximeter (Biox II oximeter). The instrument was compared with another oximeter (Hewlett-Packard 47201A) under conditions of both steadily maintained and progressively increasing hypoxia induced in normal subjects by rebreathing. The new oximeter (Biox II), which can be operated in either a "normal" or "fast" response mode, as selected by a switch on the front panel, was evaluated in its "normal" mode during steady-state hypoxic conditions and in both "normal" and "fast" modes during progressive hypoxic conditions. The other oximeter (HP 47201A) was operated in its factory preset "normal" mode for all measurements. During steady-state hypoxia the relationship between oximetric arterial oxygen saturation (SaO2) readings (y) and spectrophotometrically measured SaO2 in samples of arterial blood (x) when SaO2 exceeded 65 percent was as follows: for the new oximeter (Biox), y = 0.95x + 3.25 (r = 0.96); and for the other oximeter (HP 47201A), y = 1.03x - 2.31 (r = 0.94). Neither of these relationships differed significantly from the line of identity. During trials of progressive isocapnic hypoxia induced acutely in ten normal subjects, SaO2 was measured continuously by both oximeters. With the new oximeter (Biox) operated in the "normal" mode, the relationship between values for SaO2 from it (y) and the other oximeter (Hewlett-Packard) (x) was y = 0.85x + 12.91 (r = 0.93). When the new oximeter (Biox) was switched to its "fast" response mode, the relationship more closely approximated the line of identity such that y = 1.05x - 5.95 (r = 0.98). The response of the new oximeter (Biox II) to an in vitro step change in saturation followed a complex nonexponential function characterized by small initial changes in output signal with the greatest changes in output occurring during the latter portion of the response period. The 50 percent response times of the new oximeter (Biox II) were 5.65 seconds and 2.86 seconds in the "normal" and "fast" modes, respectively, by contrast to the 50 percent response time of 2.87 seconds for the other oximeter (H-P 47201A). We conclude that the new oximeter (Biox II) demonstrated accuracy comparable to a more complex and expensive oximeter and had response characteristics that may be useful in clinical and laboratory settings.

Adult↗
PubMed1982

Medical services for outdoor rock music festivals.

This paper describes the medical services provided at an outdoor rock music festival near Toronto and reviews similar services at other outdoor concerts as reported in the literature. Between 0.5% and 1.5% of concertgoers were reported to have used medical services, proportions that may be useful in planning for future festivals. Most of the medical problems encountered were minor, although life-threatening problems occasionally occurred. Alcohol and drug abuse were common but led to major medical problems in only small proportions of patients. Guidelines for planning are suggested that include recommendations about facilities, supplies and equipment, transportation and communications, staffing and procedures. The need for liaison with the concert promoters, the police, ambulance officials and local hospital personnel is noted, and the use of the nonmedical ancillary staff is encouraged.

Adolescent↗