Breathing is controlled by respiratory centers located in the brain stem and spinal cord. The medullary respiratory centers include the dorsal respiratory group (DRG), ventral respiratory group (VRG), and Botzinger complex. The DRG contains inspiratory neurons that promote inspiration, while the VRG contains expiratory neurons that promote expiration. The pontine respiratory group in the pons modulates the medullary centers. Rhythmic breathing occurs through reciprocal inhibition between inspiratory and expiratory neurons. Inspiration is an active process involving contraction of the diaphragm and rib muscles, while expiration is usually passive due to lung elasticity.
introduction>muscles of respiration>muscles are involved>respiratory pressure>movement of thoracic cage and lungs during respiration>movement of expiration
Presentation of Dr. Lluis Blanch at 10th Pulmonary Medicine Update Course, Cairo, Egypt. Pulmonary Medicine Update Course is organized by Scribe : www.scribeofegypt.com
introduction>muscles of respiration>muscles are involved>respiratory pressure>movement of thoracic cage and lungs during respiration>movement of expiration
Presentation of Dr. Lluis Blanch at 10th Pulmonary Medicine Update Course, Cairo, Egypt. Pulmonary Medicine Update Course is organized by Scribe : www.scribeofegypt.com
Neural regulation of resp by Dr. Mrs Sunita M. Tiwale Professor Dept of Phys...Physiology Dept
Describe Nervous mechanism of regulation of respiration & significance of dual control.
Describe the different respiratory centres in brain stem with their interconnections & functions.
Describe the genesis of basic rhythm of respiration
Describe the clinical relevance of the nervous control of respiration
You can watch the video on my you tube channel: https://youtu.be/I0FaX-iQfa0
Medulla oblongata or more simply medulla is part of brain stem which forms base of the brain stem. It contains pyramid, olive and above pyramidal structure, there is decussation of pyramids which explains why each part of brain controls opposite part of body. Adding to that medulla also has several nuclei which controls activity of cardiovascular system and respiratory system. Medulla also has nuclei for controlling reflexes of vomiting, swallowing, hiccuping, coughing and sneezing. It has also nuclei for test, hearing and balance. Medulla also contains nuclei of cranial nerve number VIII, IX, X, XI and XII.
Here is anatomy and physiology of brain stem. Where we will discuss all three parts of brain stem. Starting from medulla, second is pons and third is mid brain. In this video I am presenting anatomy and physiology of medulla. Anatomy of medulla: Medulla Oblongata or more simply medulla is part of brain stem which forms base of the brain stem. Location of medulla oblongata is superior to spinal cord and inferior to Pons. It contains pyramid, olive and above pyramidal structure, there is decussation of pyramids which explains why each part of brain controls opposite part of body. Adding to that medulla also has several nuclei which controls activity of cardiovascular system and respiratory system. Medulla also has nuclei for controlling reflexes of vomiting, swallowing, hiccuping, coughing and sneezing. It has also nuclei for test, hearing and balance. Medulla also contains nuclei of cranial nerve number VIII, IX, X, XI and XII. Functions of medulla or what dose medulla do? So medulla controls blood pressure, diameter of wall of arteries, heart rate, basal respiration rate and also vomiting, swallowing, hiccuping, coughing and sneezing.
In this video, we explain you about anatomy and physiology of Pons. The reference material used to make video is: Principles of Anatomy and Physiology Gerard J. Tortora, Bryan H. Derrickson. Pons is part of brain stem, present superior to medulla, inferior to mid brain and anterior to cerebellum. Pons means a bridge. As the name denotes, it connects other areas of brain. Neurons extending from cerebral cortex to pons makes corticopontine tract. Pons is connected to cerebellum by middle cerebral peduncle. Pons has vestibular nuclei, which is part of equilibrium pathways from inner ear to brain. Pons has also respiratory nuclei. Along with rhythmicity area of medulla, pons controls basal respiratory rhythm. Pons also contains nuclei for cranial nerve number V, VI,VII, and VIII.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
- Video recording of this lecture in English language: https://youtu.be/kqbnxVAZs-0
- Video recording of this lecture in Arabic language: https://youtu.be/SINlygW1Mpc
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
The Gram stain is a fundamental technique in microbiology used to classify bacteria based on their cell wall structure. It provides a quick and simple method to distinguish between Gram-positive and Gram-negative bacteria, which have different susceptibilities to antibiotics
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
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Muktapishti is a traditional Ayurvedic preparation made from Shoditha Mukta (Purified Pearl), is believed to help regulate thyroid function and reduce symptoms of hyperthyroidism due to its cooling and balancing properties. Clinical evidence on its efficacy remains limited, necessitating further research to validate its therapeutic benefits.
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
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NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
Basavarajeeyam is an important text for ayurvedic physician belonging to andhra pradehs. It is a popular compendium in various parts of our country as well as in andhra pradesh. The content of the text was presented in sanskrit and telugu language (Bilingual). One of the most famous book in ayurvedic pharmaceutics and therapeutics. This book contains 25 chapters called as prakaranas. Many rasaoushadis were explained, pioneer of dhatu druti, nadi pareeksha, mutra pareeksha etc. Belongs to the period of 15-16 century. New diseases like upadamsha, phiranga rogas are explained.
2. Breathing is produced by rhythmic discharge of signals from the
spinal motor neurons (= anterior horn cells) that supply the
respiratory muscles, which are located in the cervical and thoracic
parts of the spinal cord.
This discharge is controlled by 2 mechanisms :
1. An involuntary automatic (subconscious) mechanism : This is
the principal mechanism that controls respiration, and is
performed by the respiratory centres
3. (2) A voluntary (conscious) mechanism : Breathing can voluntarily
be stopped (e.g. during talking) or accelerated (when required)
However, this can be performed for only a short time, and is
produced by signals discharged from the motor area of the
cerebral cortex via the corticospinal (= pyramidal) tract, which
directly affect the activity respiratory spinal motor neurons.
Ondine's curse: This is an old legend that tells about a man who
had lost his automatic control of respiration.
In such case, respiration can occur only by voluntary control,
and to maintain life, he should stay awake to remember to breathe
voluntarily, which is evidently fatal due to either exhaustion or the
resulting apnea if he fell asleep
4. Historical background
In the early 1920s, Lumsden performed brainstem transections
concluded that respiratory control was provided by centers which
he called the pneumotaxic center (in the upper pons), the
apneustic center (in the lower pons) and the inspiratory and
expiratory centers in the medulla oblongata
The pontine centers were postulated because a transection
between upper and lower pons effectively removing the
pneumotaxic center, produces slow deep breathing
If done in conjunction with a bilateral vagotomy, to remove vagal
sensory input from the lungs, inspirations become prolonged,
separated by only brief expirations (a pattern referred to as
apneustic breathing)
5. This led to the conclusion that the pneumotaxic center normally
promoted expiration and the apneustic center normally promoted
inspiration
Postulation of the medullary inspiratory and expiratory centers
arose because, after a transection between the pons and medulla,
breathing was dominated by prolonged expiratory spasms and
irregular short inspiration
However, more refined techniques for pons ablation have since
demonstrated that the medulla by itself will produce a relatively
normal pattern of rhythmic inspiration/expiration.
6. This pattern becomes slower and deeper when the incoming
vagal sensory information is blocked.
As breathing is abolished only by a transection between the
medulla and spinal cord, the rhythmic drive to the respiratory
muscles must be generated within the medulla
7. Recent Developments
No specific group of neurons has ever been found in the so-
called apneustic center, so that it and any theories of respiratory
control involving it, have been abandoned
The pneumotaxic center is now referred to as the pontine
respiratory group (PRG)
It is now known to comprise expiratory neurons in the nucleus
parabrachialis medialis and inspiratory neurons in the
parabrachialis lateralis and laterally sited Kolliker-Fuse nucleus.
8. Modern evidence indicates that rather inspiratory and expiratory
centers, the medulla is composed of three bilateral aggregations
known as the DRG, VRG and Botzinger complex.
They receive sensory information and after integration adjust
appropriately the efferent activity to the respiratory muscles
The pontine nuclei somehow modulate DRG and possibly VRG
activity
9. THE RESPIRATORY CENTRES
These centres control breathing automatically, and each
consists of a collection of neurons. They are located bilaterally in
the reticular formation of the brain stem. and include the following:
10. (A) MEDULlARY CENTRES
There are 2 groups of neurons in the medulla oblongata that
indirectly control the respiratory muscles (by discharging signals
downwards via special respiratory tracts to the spinal motor
neurons that supply these muscles)
1- A dorsal respiratory group (DRG)
It is part of the nucleus tractus solitarius
The NTS receives information from respiratory-related
mechanoreceptors and chemoreceptors
It is composed mainly of i-neurons
These are the upper motor (premotor) neurons that project
downward to the lower motor neurons of mainly the phrenic
nerves which supply the diaphragm
The DRG i-neurons exert inhibitory effect on the e-neurons in
the VRG
11. 2- A ventral respiratory group (VRG)
Located rostrally in the nucleus ambiguus and caudally in the
nucleus retroambigualis
The nucleus ambiguus contain not only premotor i-neurons but
also motor neurons to the laryngeal muscles and parasympathetic
neurons to the bronchioles and heart
The rostral part of the nucleus retroambigualis contains more i-
premotor neurons and like those of the nucleus ambiguus supply
the external intercostal and accessory muscles rather than the
diaphragm
The caudal part of the nucleus retroambigualis contains mainly
e-neurons to the internal intercostals and abdominal muscles
12. During resting breathing, in which expiration is passive, the
activity in these VRG expiratory neurons is insufficient to
discharge their lower motor neurons
The VRG expiratory neurons appear to have inhibitory effects
on inspiratory neurons late in the inspiratory phase, contributing to
the termination of inspiration, the so-called inspiratory cut-off
switch
13. Botzinger Complex
Rostral to the nucleus ambiguus
Contains entirely e-neurons
Receives sensory inputs relayed through the NTS
Exerts inhibitory effects on the i-neurons in the nucleus
ambiguus and nucleus retroambigualis
Exerts excitatory effects on the e-neurons of the VRG
It is not known where respiratory rhythmicity originates in the
medulla.
It maybe that the DRG inspiratory neurons have pacemaker
properties and spontaneously discharge in a phasic manner,
inhibiting when they do so the expiratory neurons.
14. An alternative hypothesis, is a neural network of local re-
excitation within each of the inspiratory and expiratory neuronal
pools and oscillating reciprocal inhibition between the phasic firing
of the two pools
15. Genesis of the breathing rhythm (role of the respiratory centres)
During eupnea (= normal resting breathing), the breathing
rhythm (i e. the alternation of inspiratory and expiratory phases)
occurs as follows :
The Ap. C. has an inherent tonic (=continuous) activity and is
called the pacemaker of respiration
It discharges stimulatory signals to the i neurons in the medulla
oblongata Such discharge is rendered rhythmic: by 2 mechanisms
that potentiate each other :
1- The Pn C discharges rhythmic inhibitory signals to the Ap. C.
2- The afferent vagal nerve fibres carry inhibitory signals to the Ap.
C from the inflated lungs during inspiration
16. Accordingly. the medullary i-neurons discharge rhythmically at a
rate of 12-16 bursts per minute, which produces rhythmic
inspirations.
On the other hand, the e-neurons remain quiet all the time (i.e.
do not discharge), and expiration follows inspiration passively
The signals discharged from the i-neurons start weakly then
increase in a crescendo manner (= ramp signals) for about 2
seconds, after which they stop for 3 seconds (during which
expiration occurs), then a new cycle starts
17. MECHANISM (MECHANICS) OF INSPIRATION
Inspiration is an active process.
The signals discharged from the I neurons are conducted
downwards via special respiratory tracts to the spinal cord,
where they stimulate the spinal motor neurons that supply the
inspiratory muscles, which are located in the 3rd, 4th and 5th
cervical segments as well as in all thoracic segments.
The phrenic nerves arise from the cervical neurons and supply
the diaphragm, while the intercostal nerves arise from the thoracic
segments and supply the external intercostal muscles which
extend obliquely downward and forward between the ribs.
18. When the diaphragm contracts, it moves down leading to an
increase in the vertical diameter of the chest (about 1.5 cm during
eupnea and up to 7-l 0 cm during deep inspiration)
On the other hand, contraction of the external intercostal
muscles leads to:
(a) Elevation and eversion of the ribs (a bucket-handle movement)
(a) Movement of the sternum forwards and its tilt upwards These
movements increase the antero-posterior diameter of the chest
markedly and its lateral (or transverse) diameter to some
extent.
19. Accordingly, the chest cavity expands in all dimensions, leading
to movement of the parietal pleura outwards. This decreases the
intrapleural pressure, becoming more negative, which causes
expansion of the lungs.
As a result, the intrapulmonary pressure decreases from zero to
about - I mmHg, which causes rush of about 500 ml of
atmospheric air (= tidal volume) into the lungs, leading to its
inflation.
20. The inspiratory muscles
(I) During eupnea (normal resting breathing), the basic inspiratory
muscles are the diaphragm and external intercostal muscles
(2) During forced inspiration : In addition to the basic muscles, the
following accessory inspiratory muscles also contract to widen the
chest cavity
1- The sternomastoid and scaleni muscles (elevate the upper
ribs).
2- The levator costarum and serratus posterior superior muscles
(help rib elevation).
3- The quadratus lumborum and serratus posterior inferior
muscles (prevent inward movement of the lower ribs when the
diaphragm contracts).
21. Abdominal and costal (or thoracic) breathing
Breathing produced by contraction of the diaphragm is called
abdominal breathing (or respiration) because it is accompanied by
movement of the anterior abdominal wall forwards (due to rise of
the intra-abdominal pressure)
On the other hand breathing by contraction of the external
inlet costal muscles is called the costal or thoracic breathing.
During eupnea, the abdominal breathing accounts for about 75
% of the pulmonary ventilation.
22. However, the diaphragm is not essential (although it is the most
important inspiratory muscle) because if its movement is
compromised, costal breathing can maintain life.
The latter also becomes equally important in deep breathing
and during measurement of the vital capacity.
23. Effects of various lesions on respiration
1. A complete spinal cord transection above the origin of the
phrenic nerves (the 3rd cervical segment) is fatal (e.g. hanging)
due to isolation of the respiratory centres.
On the other hand, if this lesion is below the origin of the phrenic
nerves (the 5th cervical segment), -respiration is not markedly
affected because the diaphragm is still functioning.
2. Bilateral phrenic nerve palsy does not affect pulmonary
ventilation at rest (which can be maintained by costal breathing);
but breathing becomes labored and the pulmonary ventilation is
reduced during exercise
24. MECHANISM (MECHANICS) OF EXPIRATION
During eupnea, expiration is a passive process (i.e. no muscle
activity is involved).
It occurs after relaxation of the inspiratory muscles by the
elastic property of the lungs and the surface tension of the fluid
that lines the alveoli, and is aided by elevation of the diaphragm
and the weight of the thoracic cage.
These effects decrease the chest volume, so the intrapleural
pressure increases, becoming less -ve, which helps the
lungs to recoil.
25. As a result, the intrapulmonary pressure increases to about
+ 1 mmHg leading to rush of about 500 ml of air(tidal volume)
outwards and the lungs are deflated.
Such deflation occurs slowly because the inspiratory muscles
are partially contracted in the early expiration (which exerts a
braking action on the lung recoil forces).
On the other hand, the muscles of expiration contract only
during forced expiration (e.g. during muscular exercise) and in
cases of increased airway resistance (e.g. asthma) and
diminished elasticity of the lungs (e.g. emphysema).
26. The expiratory muscles include mainly the following :
l. The anterior abdominal wall muscles : The contraction of these
muscles increases the intra-abdominal pressure, which causes
bulging of the diaphragm upwards into the chest cavity, thus
helping outward expulsion of the air.
2. The internal intercostal muscles : These muscles extend
obliquely downward and backward in between the ribs, so their
contraction causes depression of the ribs, whicth reduces the
chest volume and helps expiration.
27. Intrapulmonary (or alveolar) pressure changes during eupnea
The intrapulmonary pressure is normally zero (i.e. atmospheric)
during the expiratory pause (in the mid thoracic position).
At the start of inspiration, It decreases to about -I mmHg due to
lung expansion.
This allows rush of about 500 ml of atmospheric air into the
lungs and as a result, it increases gradually till becoming
atmospheric again by the end of inspiration.
At the start of expiration, it rises to about +1 mmHg due to lung
recoil. This allows rush of about 500 ml of air outwards from the
lungs and as a result, it decreases gradually till becoming
atmospheric again by the end of expiration.
28. HERING BREUER REFLEXES
1. Hering Breuer inflation reflex (= inhibito-inspiratory reflex)
Lung inflation leads to stoppage of inspiration and initiation of
expiration.
The receptors are slowly-adapting stretch receptors(= inflation
receptors) located among the airway smooth muscle cells.
Signals from such receptors are conducted via afferent fibres in
the vagi nerves to the brain stem, where they inhibit the activity of
the apneustic centre (thus the inspiratory process stops and
expiration starts).
29. 2. Hering Breuer deflation reflex (= excito-inspiratory reflex)
Lung deflation leads to stoppage of expiration and initiation of
inspiration.
The receptors are certain deflation receptors which are probably
a type of irritant receptors
Signals from such receptors are conducted via afferent fibres in
the vagi nerves to the brain stem, where they stimulate the
apneustic centre (thus the expiratory process stops and
inspiration starts).
30. *** The inflation receptors are not adequately excited till the tidal
volume exceeds 1 litre. Therefore, the Hering Breuer reflexes
normally play a little role during eupnea in adults.
However. they become important during deep & anaesthesia (in
which they provide a protective mechanism against excessive
inflation and deflation of the lungs).
Also, the inhibitory vagal discharge during inspiration shares in
producing rhythmic breathing
***It was reported that in newly-born infants, lung inflation excites
the apneustic centre leading to a prolonged inspiration and more
lung inflation. Such response is called the paradoxical reflex.
However, its presence is doubtful.
31. Effects of bilateral vagotomy on breathing
The inhibitory input to the apneustic centre (Ap.C) carried by the
vagi nerves potentiates the inhibitory input from the pneumotaxic
centre (Pn.C) and both produce rhythmic breathing.
Therefore, the effects of bilateral vagotomy on breathing depend
on whether the brain stem is intact or transected, and also the
level of transection as follows:
(1) If the brain stem is intact or transected above the pons,
bilateral vagotomy renders breathing to be deep and slow,
because the Pn. C becomes the only source of inhibition to the
Ap.C.
32.
33. (2) If the Pn.C is isolated from the Ap.C by a mid-pontine
transection, bilateral vagotomy deprives the Ap. C from all
inhibitory signals, so it discharges continuously resulting in
apneustic breathing
(3) If the medulla is isolated from the pons breathing remains
rhythmic but becomes irregular whether the vagi are intact or cut
due to spontaneous discharge from the i neurons (which are
stimulated by a special pacemaker in the medulla caned the pre-
Bottzinger complex).
34. (4) lf the medulla is isolated from the spinal cord e.g. in hanging,
breathing stops (= apnea) and death occurs whether the vagi
nerves are intact or cut because the respiratory centres are
separated from the spinal motor neurons that supply the
respiratory muscles.
35. APNEUSTIC BREATHING (=APNEUSIS)
This is a type of breathing that occurs as a result of bilateral
vagotomy together with a midpontine transection.
lt can be produced in experimental animals but is rarely seen
clinically. It is characterized by prolonged spasmodic inspirations
interrupted by short weak expirations (due to exhaustion
ofthe inspiratory muscles).
This occurs as a result of continuous discharge of excitatory
signals from the Ap. C to the inspiratory muscles due to its release
from the inhibitory inputs of both the Pn. C and the vagi nerves.
Such pattern of breathing cannot maintain life and leads to death
due to asphyxia.
36. THE INTRAPLEURAL AND INTRATHORACIC PRESSURES
The intrapleural pressure (IPP) is the pressure inside the pleural
cavity. It is normally negative (i.e. subatmospheric) during eupnea
and it becomes more negative during inspiration.
Such negativity is due to the elastic properties of both the lungs
and chest wall as follows :
1. The elastic property of the lungs : This is due to the elastic
elements in the lungs, the elastin & collagen fibres (1/3) and the
surface tension of the fluid layer that lines the alveoli (.2/ 3 ).
It tends to decrease the lung's volume, thus pulling the visceral
pleura inwards.
37. 2. The elastic property of the chest wall This tends to expand the
thoracic cage, thus pulling the parietal pleura outwards
These opposing forces result in continuous pulling of the 2
pleural layers apart from each other which creates an equal
negative pressure in both the pleural & chest cavities
38. SIGNIFICANCE (IMPORTANCE) OF THE IPP NEGATIVITY
I . It prevents collapse of the lungs and keeps them inflated.
2. It helps lung expansion during inspiration (which decreases the
work of breathing)
3. It helps the venous return by the thoracic pump.
4. It helps lymph drainage through the thoracic lymph ducts.
5. It increases the blood flow in the pulmonary vessels.
39. NORMAL VALUES OF THE IPP
The IPP varies with the body position as well as in the different
parts of the pleural cavity due to the effect of gravity
The following are the average normal values in the standing
position .
1. In the midthoracic position (after a normal expiration), the IPP
averages -4 or- 5 cm H20 (about -3 mmHg), varying from - 2.5 cm
H20 in the lung bases to - I0 cm H20 in the lung apices
2. During normal inspiration, the IPP decreases to - 7.5 or- 8 cm
H20 (about -6 mmHg) due to the increase in the lung recoil forces.
40. 3. During forced inspiration , the IPP decreases to about - 40 cm
H20, i.e. about- 30 mmHg, and is further decreased on performing
the Muller's maneuver (= forced inspiration against a closed
glottis)
4. During forced expiration, the IPP increases and becomes
positive at the lung bases, and is further increased on performing
the Valsalva’s maneuver(= forced expiration against a closed
glottis).