Different Causes of Shortness of Breath.
Respiratory Failure.
Physiological Role of Respiratory Centers in the mechanism of
pulmonary Ventilations.
Learning Objectives:
At the end of the lecture, the student should be able to:
1.
2.
3.
4.
5.
6.
Define Shortness Of Breath.
Causes of Shortness of Breath.
Define Respiratory Failure.
Types OF Respiratory Failure.
Respiratory Center.
Physiological Role of Respiratory Centers in the mechanism
of pulmonary Ventilations.
Shortness Of Breath (SOB)
Definition:
An unpleasant subjective awareness of
the sensation of breathing.
It is a common symptom of cardiac
and respiratory disease but may also
occur as a result of disorders of other
systems, e.g. diabetic ketoacidosis or
severe anemia.
Different Causes of Shortness of Breath.
SYSTEM
ACUTE DYSPNEA CHRONIC
AT REST
EXERTIONAL
DYSPNOEA
Cardiovascular
Acute Pulmonary
oedema,
Chronic Heart Failure,
Myocardial Ischemia
Myocardial Ischemia
Acute Severe
Asthma.
Acute exacerbation
of COPD.
Pneumothorax.
COPD.
Chronic Asthma.
Bronchial Carcinoma.
Respiratory
Pneumonia.
Pulmonary Embolus. Large Pleural Effusions.
Acute Respiratory
Distress Syndrome.
Inhaled Foreign
body ( especially in
the child).
Severe Anemia and Obesity are also the cause of SOB.
Respiratory Failure
Definition:
• Inability of the lungs to perform their basic task of gas
exchange, the transfer of oxygen from inhaled air into the
blood and the transfer of carbon dioxide from the blood into
exhaled air.
The basis of respiratory failure may be :
• Failure of the exchange of oxygen and carbon dioxide within
the tiny air sacs (alveoli) in the lungs;
• Failure of the muscles required to expand the lungs;
• Failure of the brain centers controlling respiration.
Classification Of Respiratory Failure:
• Type 1 Respiratory Failure:
– involves low oxygen, and normal or
low carbon dioxide levels.
– occurs because of damage to lung
tissue,
–
• Type II respiratory failure :
– involves low oxygen, with high
carbon dioxide.
– also known as ‘ ventilatory failure'. It occurs when
alveolar ventilation is insufficient to excrete the carbon
dioxide being produced.
Physiological Role of Respiratory Centers in the mechanism of
pulmonary Ventilations
RESPIRATORY CENTER:
Definition:
The center in the medulla
oblongata and pons that
integrates sensory information
about the level of oxygen and
carbon dioxide in the blood
and determines the signals to
be sent to the respiratory
muscles.
Control of ventilation
• Physiological mechanisms are involved in the control of
physiologic Ventilation.
• Gas exchange primarily controls the
rate of respiration.
• The most important function of
breathing is gas exchange (of oxygen
and carbon dioxide). Thus the
control of respiration is centered
primarily on how well this is achieved by the lungs.
Ventilatory Pattern
• The pattern of motor stimuli during breathing can be divided
into
- inspiratory.
- expiratory phases.
• Inspiration shows a sudden, ramped increase in motor
discharge to the inspiratory muscles (including pharyngeal
dilator muscles).
• Before the end of inspiration, there is a decline in motor
discharge.
• Exhalation is usually silent, except at high minute
ventilation rates.
• Ventilatory pattern involves the integration of neural
signals by respiratory control centers in the medulla and
pons.
• The nuclei known to be
involved are divided into
regions known as the
following:
1 .medulla (reticular formation)
2.Pons.
Medulla
Include:
• Ventral respiratory group (nucleus retroambigualis, nucleus
ambiguous, nucleus parambigualis and the pre-botzinger
complex). The
ventral respiratory
group controls
voluntary forced
exhalation and
acts to increase
the force of
inspiration.
• dorsal respiratory
group (nucleus
tractus solitarius).
The dorsal
respiratory group
controls mostly inspiratory movements and their timing.
Pons
• Pneumotaxic center.
– Coordinates transition between
inhalation and exhalation
– Sends inhibitory impulses to the
inspiratory area
– The pneumotaxic center is
involved in fine tuning of
respiration rate.
– Apneustic center
• Coordinates transition between inhalation and
exhalation
• Sends stimulatory impulses to the inspiratory area
– activates and prolongs inhalation (long deep
breaths)
• overridden by pneumotaxic control from the
apneustic area to end inspiration