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Biomedical subjects

C Iber

Publications and source records attributed to C Iber.

At least 37 records · Page 2Linked to original sources
PubMed1991

Single night studies in obstructive sleep apnea.

The role of single night studies and the determinants of effective nasal continuous positive airway (CPAP) pressures were determined in 412 consecutive patients between 1984 and 1989. Patients chosen for analysis had an apnea index (AI) of greater than or equal to 20 hr-1 prior to CPAP. The AI was 67 +/- 30 hr-1, the body mass index (BMI) was 36 +/- 9 kg/m2, the age was 51 +/- 13 yr and the lowest oxygen saturation was 72 +/- 14%. Effective CPAP (9 +/- 3 cm H2O) was documented in 320 patients on single night studies and resulted in a 99% reduction in the frequency of obstructive events and improvement in the lowest O2 saturation to 94 +/- 5%. Only 18% of the variability in effective CPAP could be explained by AI and BMI. Single night studies are sufficient to establish effective CPAP in 78% of patients and offer considerable conservation of resources compared to routine multiple night studies. Effective CPAP pressures are variable and must be determined by incremental CPAP trials.

Arousal↗
PubMed1990

Influence of acid-base status on plasma catecholamines during exercise in normal humans.

The influence of acid-base status on plasma catecholamines during exercise was investigated in six healthy volunteers. Incremental exercise to 175 W was performed on a bicycle ergometer under four conditions: 1) control, 2) during forced hyperventilation (HV), 3) after pretreatment with acetazolamide (AZE), and 4) while breathing 4% CO2. Resting plasma norepinephrine (PNE) and epinephrine (PE) were not different among the four protocols despite higher resting pH during HV and lower resting pH after AZE [control, 7.4 +/- 0.02; HV, 7.48 +/- 0.03 (P less than 0.005); AZE, 7.36 +/- 0.01 (P less than 0.005) (P values indicate significant differences from the control protocol)]. Resting pH was not different from control during the 4% CO2 study (7.4 +/- 0.01). At the 175-W exercise load, there were significant differences in both pH and PNE. During the control test, pH was 7.38 +/- 0.02, PNE was 951 +/- 164 pg/ml, and PE was 264 +/- 132 pg/ml. During HV, pH was 7.46 +/- 0.5 (P less than 0.001), PNE was 976 +/- 67 pg/ml, and PE was 210 +/- 27 pg/ml. After AZE, pH was 7.31 +/- 0.2 (P less than 0.001), PNE was 1,866 +/- 561 pg/ml (P less than 0.005), and PE was 382 +/- 264 pg/ml. While subjects breathed 4% CO2, pH was 7.29 +/- 0.02 (P less than 0.001), PNE was 1.842 +/- 617 pg/ml (P less than 0.01), and PE was 467 +/- 275 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetazolamide↗
PubMed1990

Continuous intravenous terbutaline infusions for adult patients with status asthmaticus.

Since absorption of nebulized and subcutaneous terbutaline may be delayed or decreased during episodes of severe asthma, a preliminary trial of intravenous terbutaline was instituted in five adult patients with status asthmaticus. The terbutaline was administered as a bolus followed by a continuous infusion of 0.1-0.4 micrograms/kg/min. Although three patients may have received some improvement, the impact of intravenous terbutaline could not be distinguished from other concomitant therapy. All patients experienced tolerable adverse reactions. Further research to evaluate higher doses administered early in the hospital course and to determine receptor sensitivity needs to be conducted.

Adult↗
PubMed1989

An outbreak of nitrogen dioxide-induced respiratory illness among ice hockey players.

During February 1987 an outbreak of nitrogen dioxide-induced respiratory illness occurred among players and spectators of two high school hockey games played at an indoor ice arena in Minnesota. The source of the nitrogen dioxide was the malfunctioning engine of the ice resurfacer. Case patients experienced acute onset of cough, hemoptysis, and/or dyspnea during, or within 48 hours of attending, a hockey game. One hundred sixteen cases were identified among hockey players, cheerleaders, and band members who attended the two games. Members of two hockey teams had spirometry performed at 10 days and 2 months after exposure; no significant compromise in lung function was documented. Nitrogen dioxide exposure in indoor ice arenas may be more common than currently is recognized; only three states require routine monitoring of air quality in ice arenas, and the respiratory symptoms caused by exposure to nitrogen dioxide are nonspecific and easily misdiagnosed.

Disease Outbreaks↗
PubMed1989

Awake inspiratory airway occlusion in normal humans is followed by hyperpnea and hypocapnia.

The ventilatory response following 15 seconds of inspiratory airway occlusion at functional residual capacity (FRC) was studied in nine normal supine awake subjects. Expired minute ventilation (VE), CO2 output (VCO2), tidal volume (VT), and end-tidal PCO2 (PETCO2) were measured on a breath-by-breath basis. Alveolar PCO2 rose 5.6 mm Hg during the apnea (P less than 0.001). Ventilation rose 10.8 L/min on the first breath following apnea and remained elevated above control measurements for five breaths (P less than 0.05). The persistent hyperpnea was due to an increase in tidal volume and was associated with alveolar hypocapnia for 6 breaths or 30 sec (P less than 0.05) and an increase in CO2 output for 4 breaths (P less than 0.05). Changes in end-tidal PCO2 correlated with excess CO2 output relative to control measurements immediately prior to airway occlusion (P less than 0.03). After 15 sec airway occlusion at FRC, there is alveolar hypercapnia with a 2.6-fold first breath rise in ventilation. Persistent alveolar hyperventilation lasting 30 sec following airway occlusion may be due to delays in central chemoreceptor response or an afterdischarge phenomenon. This overshoot hypercapnia following airway occlusion may have some relevance to the development of central apneas following obstructive apnea episodes.

Adolescent↗
PubMed1989

Nocturnal rocking bed therapy: improvement in sleep fragmentation in patients with respiratory muscle weakness.

Three patients with respiratory muscle weakness developed sleep fragmentation due to nonobstructive apnea and hypopnea. In two patients in whom inspiratory muscle electromyogram was recorded, the apneas and hypopneas were terminated only by arousal and excessive recruitment of accessory muscles. Nocturnal rocking bed ventilatory support resulted in immediate improvement in sleep fragmentation and inhibited arousal-associated phasic accessory muscle activation, resulting in improvement in daytime hypercapnia and subjective sleepiness. Sleep fragmentation may occur more commonly than generally appreciated in neuromuscular disease patients who are independent of daytime ventilatory support. The use of nocturnal rocking bed is an effective noninvasive method of reversing sleep fragmentation and daytime sequelae when obstructive apnea is absent.

Adult↗
PubMed1989

Comparative effects of transdermal clonidine and oral atenolol on acute exercise performance and response to aerobic conditioning in subjects with hypertension.

We compared the effects of transdermal clonidine and oral atenolol on acute exercise performance and on conditioning response to an 8-week program of regular aerobic exercise in young, otherwise healthy subjects with mild hypertension. The study was a double-blind, randomized, parallel-group study with placebo control. Twenty-seven subjects (11 receiving transdermal clonidine, 8 receiving oral atenolol, and 8 receiving placebo) completed the study. Atenolol controlled blood pressure in all 8 subjects, vs 6 of 11 in the transdermal clonidine group and 0 of 8 in the placebo group. Both active drugs lowered systolic blood pressure during exercise. With clonidine treatment, the antihypertensive effect during exercise was smaller and was observed only at low and moderate workloads. Acute exercise performance (subjects receiving drug but still unconditioned) was assessed by endurance time at a constant workload equal to the highest workload completed on a previous 2-minute incremental exercise test. Endurance time was reduced 35% by atenolol but not by transdermal clonidine or placebo. Neither active drug interfered with the progress of the conditioning program, as measured by gradual lengthening of exercise time. However, as assessed by change in oxygen uptake standardized to a heart rate of 170 beats per minute, the improvement in conditioning was twice as great in subjects receiving transdermal clonidine and placebo (+20%, +18%) as it was in those receiving atenolol (+8%). Subjects receiving placebo and transdermal clonidine lost weight; subjects receiving oral atenolol gained weight. The changes in weight were small.

Administration, Cutaneous↗
PubMed1988

Foamy alveolar casts: diagnostic specificity for Pneumocystis carinii pneumonia in bronchoalveolar lavage fluid cytology.

Pneumocystis carinii pneumonia (PCP) is a major infectious complication of immunodeficiency states, including the acquired immunodeficiency syndrome (AIDS). Bronchoalveolar lavage (BAL) is a safe and effective procedure for making this diagnosis. In addition to the characteristic organisms, both histologic and cytologic material often reveals exudate in the form of foamy alveolar casts (FACs). To test the diagnostic utility of FACs in BAL fluids, we compared 20 PCP-positive and 28 PCP-negative fluids as assessed by silver stains. All PCP-positive fluids contained FACs on Papanicolaou-stained material. Only one PCP-negative lavage contained FACs, and transbronchial biopsy in this case revealed PCP. We suggest that FACs in BAL fluids are highly sensitive and specific for the diagnosis of PCP.

AIDS-Related Complex↗
PubMed1988

Diagnosis of pulmonary embolism.

Pulmonary embolism (PE) is often unrecognized or misdiagnosed because of the lack of specificity of clinical signs and symptoms. PE shares many of the clinical features of pneumonia and is therefore often unrecognized in elderly patients who present with low-grade fever, modest leukocytosis, and pulmonary infiltrates. Assessment of clinical risk factors increases the usefulness of diagnostic tests. The accuracy of diagnosis is improved if specific tests are performed. Ventilation-perfusion lung scans, noninvasive or contrast venography, and pulmonary angiography increase the likelihood of correct diagnosis. Since pulmonary angiography is a relatively low-risk procedure, it should be performed in most patients suspected of having PE who have nondiagnostic lung scans and negative lower extremity venous studies.

Adult↗
PubMed1987

Extreme dyspnea from unilateral pulmonary venous obstruction. Demonstration of a vagal mechanism and relief by right vagotomy.

A 43-yr-old woman developed severe exertional dyspnea after an unsuccessful attempt to correct a total right anomalous pulmonary venous connection. A clotted anastomosis resulted in unilateral pulmonary venous obstruction. Investigation excluded airway disease, left ventricular failure, and severe pulmonary hypertension as the cause of dyspnea. Exercise studies demonstrated a markedly abnormal ventilatory pattern consistent with excess vagal stimuli to the respiratory center. Temporary and then permanent vagal interruption markedly altered the respiratory pattern and improved her functional status from New York Heart Association Class III to Class I, confirming that vagal afferents were the cause of the dyspnea.

Adult↗
PubMed1987

Intravenous verapamil for treatment of multifocal atrial tachycardia with and without calcium pretreatment.

Verapamil was given to 16 consecutive patients with multifocal atrial tachycardia. Intravenous verapamil was administered at a rate of up to 1 mg/min while heart rate and systolic blood pressure were being monitored. The final 5 patients received 1 g of intravenous calcium gluconate 5 minutes before treatment with verapamil; the first 11 received no calcium. The mean +/- SD heart rate decreased by 21% from 129 to 101 beats/min, a difference of 28, 95% confidence interval (CI), 18 to 38 (p less than 0.0005 by t-test), after a mean of 22 +/- 13 minutes from the start of verapamil administration. The mean verapamil dose was 17 +/- 7 mg (6 to 30 mg). Sinus rhythm was restored in 8 patients. Pretreatment with calcium did not block the effect of verapamil on heart rate (27% decrease with calcium compared with 19% decrease without calcium, a difference of 8%, 95% CI, -7 to 23; p = 0.29) but minimized the decrease in systolic pressure (11% decrease with calcium compared with 27% decrease without calcium, a difference of 16%, 95% CI, 7 to 27; p less than 0.01). Verapamil caused transient asymptomatic hypotension in 1 patient. Arterial blood gases were unchanged by verapamil. Thus, verapamil is safe and effective therapy for multifocal atrial tachycardia, consistently slowing the heart rate and often restoring sinus rhythm. Calcium pretreatment may reduce drug-induced hypotension without preventing the antiarrhythmic effect.

Aged↗
PubMed1986

Effect of respiratory alkalosis during exercise on blood lactate.

A biofeedback model of hyperventilation during exercise was used to assess the independent effects of pH, arterial CO2 partial pressure (PaCO2), and minute ventilation on blood lactate during exercise. Eight normal subjects were studied with progressive upright bicycle exercise (2-min intervals, 25-W increments) under three experimental conditions in random order. Arterialized venous blood was drawn at each work load for measurement of blood lactate, pH, and PaCO2. Results were compared with those from reproducible control tests. Experimental conditions were 1) biofeedback hyperventilation (to increase pH by 0.08-0.10 at each work load); 2) hyperventilation following acetazolamide (which returned pH to control values despite ventilation and PaCO2 identical to condition 1); and 3) metabolic acidosis induced by acetazolamide (with spontaneous ventilation). The results showed an increase in blood lactate during hyperventilation. Blood lactate was similar to control with hyperventilation after acetazolamide, suggesting that the change was due to pH and not to PaCO2 or total ventilation. Exercise during metabolic acidosis (acetazolamide alone) was associated with blood lactate lower than control values. Respiratory alkalosis during exercise increases blood lactate. This is due to the increase in pH and not to the increase in ventilation or the decrease in PaCO2.

Acetazolamide↗
PubMed1986

A possible mechanism for mixed apnea in obstructive sleep apnea.

Hypopneas or pauses in respiratory effort frequently precede episodes of obstructive sleep apnea resulting in mixed apneas. We studied five subjects after chronic tracheostomy for obstructive sleep apnea. During stable non-REM (NREM) sleep, subjects breathed entirely through the tracheostomy. Tracheostomy occlusion caused experimental obstructive apnea which lasted 13.9 +/- 4.7 sec and ended with transient arousal and pharyngeal opening. At the end of the apnea there was marked hyperventilation (inspired minute ventilation rose 21.6 +/- 3.5 L on the first breath) followed by hypocapnia, hypopnea, and pauses in inspiratory effort as the subjects resumed NREM sleep. Hypocapnia was greater before inspiratory pauses lasting at least 5 sec than before shorter pauses (PETco2, 4.2 +/- 1.8 mm Hg below baseline vs 1.2 +/- 2.5 mm Hg below baseline). In three patients, pauses in inspiratory effort following experimental obstructive apnea were prevented by administration of 4 percent CO2 and 40 percent O2 inspired gas. This study suggests that: hyperventilation with hypocapnia occurs at the termination of obstructive apneas, and hypocapnia may be responsible for the attenuation or cessation of respiratory effort initiating the subsequent cycle of obstruction.

Adult↗
PubMed1984

Cavitation in bacteremic pneumococcal pneumonia. Causal role of mixed infection with anaerobic bacteria.

Cavitation developed in 4 of 24 patients with bacteremic pneumococcal pneumonia seen in 1 yr. Two of them had roentgenographic evidence of massive pulmonary gangrene. A total of 3 patients developed putrid sputum at the time of cavitation, proving that anaerobes were present. Culture confirmation of anaerobic etiology (Bacteroides fragilis) was obtained in 1 patient who had a thoracotomy for pulmonary gangrene. Putrid sputum was observed only in cavitary cases. Other clinical and epidemiologic features (bilateral infiltrates, alcoholism), which were more frequent in cavitary than in noncavitary cases, are often associated with anaerobic infection. These findings support the hypothesis that concomitant anaerobic infection may be responsible for cavitation in bacteremic pneumococcal pneumonia.

Adult↗
PubMed1983

Mechanisms of hypoxia-induced periodic breathing during sleep in humans.

Ventilation was studied during wakefulness and sleep in six healthy humans in normoxia (mean barometric pressure (PB) = 740 torr), and in hypobaric hypoxia (PB = 455 torr). Hypoxia caused hyperventilation and hypocapnic alkalosis (delta Pa,CO2 = -7 torr) during wakefulness and in all sleep states. Periodic breathing was the predominant pattern of breathing in all stages of non-rapid eye movement (non-r.e.m.) sleep in hypoxia, but was rarely observed during wakefulness or r.e.m. sleep. Periodic breathing was composed of repetitive oscillations of reproducible cycle length characterized by clusters of breaths with augmented inspiratory effort (VT/TI) and highly variable distribution of breath-to-breath minute ventilation (VE) and tidal volume (VT), which alternated regularly with prolongations of the expiratory pause of the last breath of each cluster (apnea duration = 5-18 sec). Hypoxia-induced periodic breathing was eliminated by: (a) acute restoration of normoxia coincident with a 3-6 torr increase in Pa,CO2; and (b) augmented FI,CO2 (at constant arterial oxygen saturation) which rapidly and reversibly eliminated apneas and stabilized breathing pattern with a less than 2 torr increase in Pa,CO2. If hypocapnia was prevented (by augmented FI,CO2) during acute induction of hypoxia in non-r.e.m. sleep, periodic breathing was also prevented. We propose that the genesis of hypoxia-induced periodic breathing requires the combination of hypoxia and hypocapnia. Periodicity results from oscillations in CO2 about a CO2-apnea threshold whose functional expression is critically linked to sleep state.

Adult↗
PubMed1983

Obstructive sleep apnea associated with adult-acquired micrognathia from rheumatoid arthritis.

The onset of severe obstructive sleep apnea occurred in one patient as he developed adult-acquired micrognathia from destruction of the temporomandibular joints by rheumatoid arthritis. Despite the anatomic deformity, nearly normal upper airway patency was maintained during wakefulness, as measured by upper airway resistance during peak tidal flow rates. Adult-acquired micrognathia from rheumatoid arthritis may be associated with obstructive sleep apnea. Anatomic deformity of the upper airway in patients with obstructive sleep apnea is not necessarily associated with marked decreases in airway patency during wakefulness.

Aged↗