Archive for the ‘Health’ Category

Sleeping and Breathing: REM Atonia Compromises Rib Cage Inspiratory Muscles

Rib cage inspiratory muscles (external intercostal, parasternal, scalene and sternocleidomastoid) contribute to a minor extent to normal breathing in adult males. Accordingly, loss of their action during REM sleep is compatible with maintenance of a normal alveolar ventilation during this stage of sleep, particularly in view of associated reduction in metabolic rate. This situation is […]

Sleeping and Breathing: Sleep Modifies Chemical Control of Breathing (Part 2)

The shift from wakefulness to non-REM sleep is not without effect on chemical control of breathing, however. A dramatic effect appears when chemical stimuli are reduced rather than increased. With mechanically assisted hyperventilation or with hyperventilation induced by hypoxic stimulation of breathing, the respiratory efforts are eliminated when arterial Pco2 decreases 2-4 mm Hg. Although […]

Sleeping and Breathing: Sleep Modifies Chemical Control of Breathing (Part 1)

Studies in man have revealed alveolar hypoventilation and diminution of ventilatory responsiveness to chemical stimuli during non-REM sleep, while results in tracheostomized dogs and intact cats reveal little alteration in alveolar ventilation and chemoventilatory responsiveness. Demonstration that upper airway resistance rises dramatically during sleep has led to the speculation that ventilatory responsiveness declines in man […]

Sleeping and Breathing: Sleep Removes Wakeful Motor Compensations (Part 2)

Patients with primary abnormalities of the respiratory pump, eg, restrictive chest wall or neuromuscular affecting the respiratory muscles, provide similar lessons to the observant physician. Alveolar ventilation during the day is normal in early stages of such diseases. However, during non-REM sleep, alveolar ventilation declines and arterial blood gas values deteriorate. This manifests wakefulness-dependent influences […]

Sleeping and Breathing: Sleep Removes Wakeful Motor Compensations (Part 1)

An obvious example of an anatomic abnormality causing sleep disordered breathing is obstructive sleep apnea caused by micrognathia. When the patient is awake, the pharyngeal airway is patent, but with sleep onset it occludes. We can infer, therefore, that wakefulness provides enhanced motor activation of upper airway muscles, which compensates for the tendency of a […]

Sleeping and Breathing: The Respiratory Controller

A basic view of the neural mechanisms controlling breathing is provided in Figure 1. The notion of a respiratory central pattern generator, essentially a timer that paces the rhythm, now enjoys wide acceptance but limited experimental proof.2 According to this concept, the output of this generator somehow gates the activity of neuronal networks that shape […]

Sleeping and Breathing (Part 2)

Breathing, the quintessential interaction between the organism and its environment, must continue when all other such interactions have ceased. As might be expected, this is not always successfully accomplished. Despite complex neural machinery automatically controlling the motor act of breathing, many individuals sustain respiratory failure during sleep. The present communication reviews how sleep and interact […]

Sleeping and Breathing (Part 1)

In Night Thoughts of a Classical Physicist, McCormack portrays a beleagered 19th century physicist struggling to cope with revolutionary advances in physics. The “ether” theory of light has been replaced by the daunting mathematics of quantum mechanics, and the insomniac scientist broods through the night about the fundamental nature of light as inferred from its […]