Search PubMed⌕ Search

Biomedical subjects

M Pokorski

Publications and source records attributed to M Pokorski.

81 records · Page 5Linked to original sources
PubMedDate not supplied

Are central respiratory chemoreceptors confined to ventrolateral medulla?

There is ample evidence that the ventrolateral medulla (VLM) is involved in regulation of respiration. The VLM is considered to be the site of location of the central respiratory chemoreceptors. Neither neuroanatomical nor neurophysiological coordinates of the chemoreceptor have ever been indisputably identified or verified, despite decades of research. This commentary addresses new hypotheses concerning the process of central chemoreception and recent findings calling into question the exclusivity of VLM for the chemoreceptor location and function. These findings rekindle the possibility of medullary respiratory neurons being chemosensors. Crucial issues concerning the central chemoreception remain unsettled and are open to further research.

Chemoreceptor Cells↗
PubMedDate not supplied

Decrease of oxygen difference between arterial blood and cerebrospinal fluid after intravenous injection of sodium bicarbonate in hyperoxic patients, anaesthetized, paralyzed and artificially ventilated.

In the subjects being prepared to neurosurgical treatment an i.v. injection of NaHCO3 (2 mEq/kg) elicited a significant increase in PCSFO2 from 69 +/- 6.4 (SEM) Torr to 75.5 +/- 3.9 (SEM) Torr. This change ws accompanied by a significant drop of PaO2 from 150.5 +/- 6.0 Torr to 138.0 +/- 5.8 Torr. Metabolic alkalosis (pH 7.54 +/- 0.02 SEM) elicited by bicarbonate administration was accompanied by arterial blood hyperoxia. Both these factors reduce the cerebral flow (CBF). We suppose that changes in the blood--CSF oxygen relationship reflect the presence of a mechanism which might protect the CNS against a decrease in CBF.

Adult↗
PubMedDate not supplied

Venous return as stimulus for respiration in rabbit.

The "exercise hyperpnoea" problem was studied in 44 anaesthetized rabbits by increasing the cardiac output by: a) tilting by 12 degrees the hindlimbs up; b) injecting into the right heart 15 ml of dextran; c) normocapnic or d) hypocapnic blood. In all cases there was an increase in minute ventilation, VE, independently of the presence or absence of an increase in CO2 flux to the lungs. We decreased the cardiac output by tilting up the head by 10 degrees; this elicited a decrease in VE accompanied by an increase in the fractional end-tidal CO2. For elucidating the role played by carotid body chemoreceptors in eleven rabbits the legs were tilted up before and while the animals breathed pure oxygen. The results were very similar. When the hindlimbs were tilted up after cervical bilateral vagotomy the VE response diminished about fifty per cent. We conclude that: a) hyperpnoea and hypopnoea elicited by a change in cardiac output are due to stimulation or depression of mechanoreceptors localized in the pulmonary circulation, b) carotid body chemoreceptors are not required for these responses, c) fifty per cent of the VE response depends on the integrity of the vagus nerves, d) it is probable that the increase in venous return plays an important role in the hyperpnoea at the onset of muscular exercise.

Animals↗
PubMedDate not supplied

Effect of acute haemorrhage and autotransfusion on respiration in the pig.

The effect of haemorrhage and transfusion of blood on minute ventilation, VE, in eight anaesthetized pigs was studied by bleeding the animals from the jugular vein and retransfusion of the same quantity of blood. Bleeding the pig from the jugular vein at approximately 50 ml/min, during 2 min, decreased V/ by 8.4 +/- 5.6 per cent of the pre-bleeding control valve (p = 0.0004) and when the same quantity of blood was retransfused the VE increased by 11.8 +/- 12.4 per cent (p=0.03). The possible mechanisms are discussed. We conclude that: a) mechanoreceptors localized in pulmonary circulation play an important role in the VE response during the first seconds of venous haemorrhage and venous transfusion, b) autotransfusion from moving legs and its effect on pulmonary mechanoreceptors may explain in part hyperpnoea at the onset of muscular exercise.

Animals↗
PubMedDate not supplied

Breathing pattern in tetraplegics during exposure to hypoxia and hypercapnia.

The question was investigated of whether thoracic feedback could play a role in shaping the tidal and frequency components of the breathing pattern. The changes in the breathing pattern of tetraplegic subjects were examined and compared with those of normal subjects during hypoxic and hypercapnic rebreathing tests, using data from our previous study. The breathing pattern was evaluated from diagramatic spirograms, constructed at an SaO2 80% and P(ET)CO2 of 55 mmHg. Chemical drive increased VT and shortened T1 and TE in both groups, but tetraplegics responded with a 60% smaller increase in VT. Since the mean inspiratory flow, VT/T1, was the same in either gas condition in both groups, the smaller VT in tetraplegics was due entirely to a shorter T1. These results show that ventilation in tetraplegics is more shallow and rapid, and it implicates thoracic feedback in modulation of the respiratory pattern.

Humans↗