RATIONALE: Obstructive sleep apnea (OSA) is common in patients with coronary artery disease (CAD), many of whom do not report daytime sleepiness. First-line treatment for symptomatic OSA is continu ...

Effect of Positive Airway Pressure on Cardiovascular Outcomes in Coronary Artery Disease Patients with Nonsleepy Obstructive Sleep Apnea. The RICCADSA Randomized Controlled Trial.

The purpose of this review is to outline the physiological responses associated with the diving response, its functional significance, and its cardiorespiratory control. This review is separated into four major sections. Section one outlines the diving response and its physiology. Section two provides support for the hypothesis that the primary role of the diving response is the conservation of oxygen. The third section describes how the diving response is controlled and provides a model that illustrates the cardiorespiratory interaction. Finally, the fourth section illustrates potential adaptations that result after regular exposure to an asphyxic environment. The cardiovascular and endocrine responses associated with the diving response and apnea are bradycardia, vasoconstriction, and an increase in secretion of suprarenal catecholamines. These responses require the integration of both the cardiovascular system and the respiratory system. The primary role of the diving response is likely to conserve oxygen for sensitive brain and heart tissue and to lengthen the time before the onset of serious hypoxic damage. We suggest that future research should be focused towards understanding the role of altered ventilatory responses in human breath-hold athletes as well as in patients suffering from sleep-disordered breathing. A lack of oxygen even for short periods can be detrimental to most birds, mammals, and humans. However, many diving birds, mammals, and humans have adapted to endure hypoxia or anoxia for extended periods (Hermes-Lima & Zenteno-Savin, 2002). The major physiological adaptation allowing animals to endure the lack of oxygen during apnea is the diving response. The diving response has been demonstrated across a variety of diving birds, mammals (Butler & Jones, 1997), and humans (Hong, 1989). It is qualitatively similar between species and involves both bradycardia and peripheral vasoconstriction triggered in response to respiratory arrest (Daly, 1997) and stimulation of facial cold receptors (Elsner & Gooden, 1983). For the purpose of this review, we will use the following terms: diving response, apnea, and face immersion and define them as follows. The diving response is a reduction in heart rate because of an increase in cardiac parasympathetic nerve activity, peripheral vasoconstriction on the arterial vascular tree, and an increase in sympathetic activity triggered in response to the cessation of respiration and, but not necessarily including, the stimulation of facial cold receptors. We will refer to the cessation of respiration as apnea and the stimulation of facial cold receptors by water will be referred to as face immersion. The human diving response involves bradycardia (Asmussen & Kristiansson, 1968), vasoconstriction

/pdf/the-human-diving-response-its-function-and-its-control-1lhltpnae0.pdf

The human diving response, its function, and its control

The aging respiratory system--pulmonary structure, function and neural control.

This review provides a pulmonary-focused description of the age-associated changes in the integrative physiology of exercise, including how declining lung function plays a role in promoting multimorbidity in the elderly through limitation of physical function. We outline the ageing of physiological systems supporting endurance activity: 1) coupling of muscle metabolism to mechanical power output; 2) gas transport between muscle capillary and mitochondria; 3) matching of muscle blood flow to its requirement; 4) oxygen and carbon dioxide carrying capacity of the blood; 5) cardiac output; 6) pulmonary vascular function; 7) pulmonary oxygen transport; 8) control of ventilation; and 9) pulmonary mechanics and respiratory muscle function. Deterioration in function occurs in many of these systems in healthy ageing. Between the ages of 25 and 80 years pulmonary function and aerobic capacity each decline by ∼40%. While the predominant factor limiting exercise in the elderly likely resides within the function of the muscles of ambulation, muscle function is (at least partially) rescued by exercise training. The age-associated decline in pulmonary function, however, is not recovered by training. Thus, loss in pulmonary function may lead to ventilatory limitation in exercise in the active elderly, limiting the ability to accrue the health benefits of physical activity into senescence.

https://erj.ersjournals.com/content/erj/48/5/1471.full.pdf

Exercise, ageing and the lung.

Obstructive sleep apnea (OSA) is common in the general population and highly prevalent in patients with cardiovascular disease. In this paper, we review (1) the pathophysiological mechanisms of OSA that may causally contribute to cardiovascular disease; (2) current evidence regarding the association between OSA and hypertension, stroke, ischemic heart disease, heart failure, atrial fibrillation, and cardiovascular mortality; and (3) the impact of continuous positive airway pressure (CPAP) treatment on cardiovascular risk factors and outcomes. We emphasize the importance of obesity as a comorbidity of OSA and a confounder in the association between OSA and cardiovascular disease. We also discuss the importance of addressing obesity in patients with OSA, as a strategy to reduce the burden of cardiovascular risk factors in this population. Implications for the approach of patients' OSA in clinical practice and future research directions are discussed.

The Link Between Obstructive Sleep Apnea and Cardiovascular Disease.

CPAP effect on recurrent episodes in patients with sleep apnea and myocardial infarction.

The progressive effects of ageing on chemosensitivity in healthy subjects.

The aim of the present study was to examine the relationships between the responses to progressive isocapnic hypoxia and hypoxic withdrawal test in patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS) and to analyse the determinants of carotid body sensitivity in OSAHS.

Nineteen consecutive OSAHS patients and 13 healthy subjects were selected. Ventilatory (Δ V ′I/ S a,O2/BSA) and inspiratory neural drive (Δ P 0.1/ S a,O2) responses to progressive isocapnic hypoxia were determined. Peripheral chemosensitivity was evaluated by the hypoxic withdrawal test, which measures the decrease in ventilation caused by two breaths of 100% oxygen (%Δ V ′I).

Withdrawal response and ventilatory and inspiratory neural drive responses to hypoxia were lower in OSAHS patients than in control subjects. In patients with OSAHS, %Δ V ′I correlated significantly with Δ V ′I/ S a,O2/BSA and with Δ P 0.1/ S a,O2. On stepwise multiple linear regression analysis, a strong correlation between %Δ V ′I and Δ P 0.1/ S a,O2 was found. Moreover, %Δ V ′I, Δ V ′I/ S a,O2/BSA and Δ P 0.1/ S a,O2 were significantly correlated with minimum arterial oxygen saturation and with arousal index.

Obstructive sleep apnoea-hypopnoea syndrome patients have a strong relationship between peripheral chemosensitivity and respiratory response to hypoxia, suggesting that hypoxic stimulation of central chemoreceptors is minimally relevant in obstructive sleep apnoea-hypopnoea syndrome. Moreover, sensitivity of the carotid body in patients with obstructive sleep apnoea-hypopnoea syndrome is related to sleep disruption and to nocturnal hypoxia.

This study was supported by FIS (96/1280 and 99/0252) and Neumomadrid (2000) Grants.

https://erj.ersjournals.com/content/erj/20/3/724.full.pdf

Inspiratory neural drive response to hypoxia adequately estimates peripheral chemosensitivity in OSAHS patients

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Papers

CPAP effect on recurrent episodes in patients with sleep apnea and myocardial infarction.

The progressive effects of ageing on chemosensitivity in healthy subjects.

Inspiratory neural drive response to hypoxia adequately estimates peripheral chemosensitivity in OSAHS patients