Biomedical subjects

M H Kryger

Publications and source records attributed to M H Kryger.

95 records · Page 6Linked to original sources

PubMed1976

Exercise tolerance at 4 and 6 ATA.

Seven normal male subjects performed 5-min bicycle exercise ranging from 50-100% maximum oxygen uptake at 4 ATA and three were also studied at 6 ATA. At all pressures, the subjects breathed 0.2 ATA O2 plus nitrogen. All subjects were able to perform maximum work at all pressures. No pressure-dependent variations in heart rate, O2 uptake, or CO2 output were noted. At both 4 and 6 ATA, ventilation was decreased at exercise levels greater than 80% maximum O2 uptake. The magnitude of the decrease was not great, however, and signified only minor CO2 retention. In some instances exercise ventilation closely approached the 15-S maximum breathing capacity and these subjects noted severe dyspnea, possibly due to dynamic compression of large airways. In three subjects, respiratory frequency was measured as well as minute ventilation; this relationship did not change with depth. Subjects performing heavy exercise at 6 ATA noted disturbances of consciousness, presumably due to N2 narcosis.

Adaptation, Physiological↗

PubMed1975

Effect of inspiratory resistance of occlusion pressure in hypoxia and hypercapnia.

The authors measured ventilation and the mouth pressure developed during the first 0.1 sec of inspiratory effort against a closed airway (P 0.1) in response to normoxic hypercapnia and normocapnic hypoxia, with and without added inspiratory resistance. Hypercapneic responses were elicited by a steady-state technique, hypoxic responses by a non-steady-state technique. External resistance depressed the ventilatory response to CO2 but in general augmented the P 0.1 response. The degree of change of response was not predictable on the basis of the response in the absence of resistance. Hypoxic ventilatory response was also diminished by resistance and P 0.1 increased. The authors concluded that in normal subjects added inspiratory resistance increased inspiratory drive as assessed by P 0.1.

Adult↗

PubMedDate not supplied

Clinical presentations of obstructive sleep apnea syndrome.

Obstructive sleep apnea syndrome (OSAS) is a common but still underrecognized disorder. It affects 2% to 4% of middle-aged adults, a significant proportion of whom are female. The spectrum of clinical presentations of OSAS and their severity is variable, ranging from neurocognitive complaints to cardiorespiratory failure. OSAS has a significant impact on quality of life, cardiovascular morbidity, and mortality. Its major sequelae include daytime somnolence and its consequences (motor vehicle accidents, poor work performance, disrupted social interactions), systemic and pulmonary hypertension, and ischemic heart disease. Treatment of OSAS results in improvement in symptoms, quality of life, and blood pressure control, and may improve mortality. An expansion of our understanding of this condition has resulted in increased awareness of its consequences, but the recognition of OSAS in clinical practice is still delayed. Identification of these patients in clinical practice requires attention to risk factors (history of snoring and witnessed apneas, obesity, increased neck circumference, hypertension, family history) and careful examination of the upper airway. Clinical impression alone, however, has poor (50% to 60%) sensitivity and specificity (63% to 70%) and the diagnosis is usually obtained on polysomnography. Physicians and other health care professionals need to be aware of the progress made in this area and recognize the necessity for prompt evaluation and treatment of these patients.

Diagnosis, Differential↗

PubMedDate not supplied

Effect of aminophylline and relief from hypoxia on central sleep apnoea due to medullary damage.

A 17-year old boy presented with severe, predominantly central sleep apnoeas secondary to structural damage in the medulla. At low O2 saturation, the electroencephalogram showed the sudden onset of slow waves. Hypercapnic ventilatory response was low and hypoxic ventilatory response was absent. Low flow oxygen therapy dramatically improved the apnoea score, probably by relieving hypoxic brain depression. Slow waves also disappeared with oxygen therapy. Aminophylline was effective on apnoea score and duration (p less than 0.001). This beneficial effect could be explained by an improvement of the normal oscillations of respiration at the onset of sleep, a change in arousability or a stimulation of the ascending reticular system. These findings suggest a possible role of hypoxic depression in the manifestations of central sleep apnoeas and demonstrate the beneficial effect of low flow oxygen and aminophylline in treating certain central sleep apnoeas.

Adolescent↗

PubMedDate not supplied

The role of protriptyline in obstructive sleep apnea.

Protriptyline, a non-sedating tricyclic agent, was evaluated in a double blind drug-placebo crossover trial in five obese patients with obstructive sleep apnea. Four of the five patients had improvement in somnolence. Protriptyline improved oxygenation. This seemed related primarily to a reduction (from 23% to 11%) in REM, with fewer of the more severe REM apneas. Arousal frequency remained quite high; thus the reason for the reduction in somnolence remains unclear. In three patients, at six months the improvement in clinical status and oxygenation persisted. We have now attempted long term treatment in nine patients. In five, anticholinergic side-effects necessitated stopping therapy. Four patients continue to do well. A trial of protriptyline is thus indicated in treatment of mild to moderate obstructive apnea or when the patient refuses more invasive treatment.

Adult↗