This document discusses various modes of mechanical ventilation. It begins by describing the basic components and functions of a ventilator. The document then explains the key parameters that ventilators can control including tidal volume, frequency, pressure, and time settings. Several common ventilation modes are described including controlled mandatory ventilation (CMV), assist-control ventilation, intermittent mandatory ventilation (IMV), and synchronized intermittent mandatory ventilation (SIMV). Each mode is defined by how the ventilator delivers breaths in terms of being time-triggered or patient-triggered and how breaths are cycled. The advantages and disadvantages of different modes are also briefly discussed.
Mechanical ventilation ppt including airway, ventilator, tubings and connections, nursing management, trouble shooting common problems and issues, suctioning etc.
Comprehensive presentation on intra arterial blood pressure with a good insight into the the basic physics and brief look into the risks and complications.
Mechanical ventilation ppt including airway, ventilator, tubings and connections, nursing management, trouble shooting common problems and issues, suctioning etc.
Comprehensive presentation on intra arterial blood pressure with a good insight into the the basic physics and brief look into the risks and complications.
Mechanical ventilation uses endotracheal intubation and a ventilator to replace spontaneous respiration and ventilation.
The ventilator provides the function of the respiratory muscles, endotracheal tube establishes a patent and unobstructed airway and the exogenous oxygen source gives a patient a therapeutic concentration of the gas.
Sepsis is leading cause of death in children. septic shock and multi organ dysfunction is final common pathway for death in various infections. We discuss here evidence based management of sepsis and septic shock in children.
Kumar m, tiwari l. snake bite a review jpcc 2018Lokesh Tiwari
Snake bite is a common but under-reported medical emergency accounting for 0.5% of all deaths with greater risk of fatal envenomation in children. In India, four species of venomous snake are most common but better classification of medically significant species is warranted. Snake venom is a mixture of peptides with enzymatic & toxic properties which mediate activation of cytokine cascades along with organ specific toxicities, manifesting into local and systemic symptoms. The syndromic approach of attributing a constellation of signs & symptoms to a particular family of venomous snake has clinical acceptance but overlaps exist. Management of snake bite victim starts with a first aid measures of reassurance, immobilization and quick transfer to hospital. Measures such as application of tourniquet, incision and suction are harmful & should not be done. On arrival at hospital, triage and stabilization of Airway, Breathing & Circulation (ABC) is done followed by a focused assessment to ascertain the severity of envenomation. Antivenom treatment is the mainstay of snake bite management. ASV should be started only when specific indications such as signs of neurotoxicity, coagulopathy, hypotension, hematuria are present. Indiscriminate use of ASV is strongly condemned.Currently 8-10 vials of ASV as initial dose with a maximum of 25 vials is recommended. There is no role of test dose of ASV. Measures to treat any ASV induced anaphylaxis should be ready prior to start of ASV treatment. Supportive treatment is as important in determining the final outcome of envenomation as ASV
Myocardial dysfunction in sepsis jpcc jul aug 2018Lokesh Tiwari
Septic shock is a major cause of mortality in children. Myocardial dysfunction in severe sepsis and septic shock
is well recognized but its pathogenesis could be multifactorial. As a result of complex interplay of various factors,
hemodynamic changes observed in pediatric age group may be different from those observed in adult. Sepsis induced myocardial dysfunction (SIMD) is a known consequence of severe sepsis and septic shock. Although there is no
universally accepted defi nition of this entity, it can be best defi ned as reversible intrinsic myocardial systolic and diastolic dysfunction of both the left and right sides of the heart induced by sepsis. In this review we discuss the pathogenesis, pathophysiology of clinical manifestations, diagnosis and management of SIMD in children.
Key words: Sepsis induced myocardial dysfunction (SIMD), Severe Sepsis, Septic Shock
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.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
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.
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- 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
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
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
2. What are ventilators ?
A machine that generates a controlled flow of gas into a patient’s airways
Supportive role to buy time
3. Mechanical ventilation
Several models have evolved over time-
Negative pressure ventilation
Positive pressure ventilation
Simple pneumatic system
New generation microprocessor controlled systems.
The basic function and applications remain common.
4. Basic Ventilator Parameters
Tidal volume
Frequency
PIP
Plateau Pressure
PEEP
Inspiratory Time
Expiratory time
I:E Ratio
5. Basic Ventilator Parameters
Mode
Tidal volume
Frequency
PIP
Plateau Pressure
PEEP
Inspiratory Time
Expiratory time
I:E Ratio
6. Starting a ventilator: Mode
Mode denotes interplay b/w patient and the
ventilator
Describes the style of breath support based on
relationship between the various possible types of
breath and inspiratory – phase variables
7. Where to Start ?
CPAP, IPAP, EPAP, NIV
Pressure control, Volume control
CMV, Assist Control, IMV, SIMV,
PSV, ASV, MMV,
APRV
PCV, PRVC, PSV, VCIRV, Volume
Support,
Auto Mode,
BiLevel, BiPAP,
HFJV, HFOV
10. Objectives
Understand how ventilators control breath delivery, phase and
control variables.
Understand the basic modes of ventilation.
Combinations, tailor-making, mix and match…
12. The ventilator circuit
50 psi air
50 psi O2
Blender
Air-O2 mixture
of desired FiO2
at 50 psi
Stepped down
pressure
Flow
regulator
Pressure
regulating
valve
T-piece & ETT
tube
Insp limb
Exp limb
13. Flow regulators / PEEP
Flow in
ventilator
circuit-
constant
Flow in ET & patient
airway-
keeps changing in
magnitude &
direction !!
T-connection
ET
T
Baby’s
airway
PEEP
PIP
Flow
sensor
14. What does flow sensor do?
Flow in
ventilator
circuit-
constant
T-connection
E
T
T
Flow
sensor
Insp flow
RR
= tidal vol
Exp flow
- insp flow
= peri-tube leak
15.
16. Ventilatory Phases
• Inspiration: Inspiratory valve opens and
expiratory valve is closed
• Inspiratory pause: inspiratory valve and
expiratory valve closed
• Expiration: Inspiratory valve closed and
expiratory valve open
• Expiratory pause: Inspiratory valve and
expiratory (or PEEP) valve closed at end
of expiration
Ti Te
0
18. Phase variables
Trigger : ventilator (time)- triggered or patient (pressure or flow)
triggered
Limit: flow-limited or pressure-limited
Cycling: volume, time, flow or pressure cycled.
19. Phase variables: Trigger
What causes the breath to begin (signal to open the
inspiratory valve)
Machine (controlled): the ventilator will trigger regular breaths at a
frequency which will depend on the set respiratory rate, ie, they will be
ventilator time triggered.
Patient (assisted): If the patient does make an effort to breathe and the
ventilator can sense it (by either sensing a negative inspiratory pressure
or an inspiratory flow) and deliver a breath, it will be called a patient-
triggered breath.
22. Phase variables: Limit
Factor which controls the inspiration inflow
Flow Limited: a fixed flow rate and pattern is set and maintained throughout inspiration.
An adequate tidal volume (Ti dependent)
Pressure will be variable (comp and resistance dependent)
Pressure limited: the pressure is not allowed to go above a preset limit.
The tidal volume will be variable (comp and resistance dependent)
23. Phase variables: Cycling
Signal that stops the inspiration and starts the expiration.
Without inspiratory pause: one signal
With inspiratory pause: two cycling signals (one to close inspiratory valve and
the second to open the expiratory valve)
Volume
Time
Flow
Pressure : back-up form of cycling when the airway pressure reaches the
set high-pressure alarm level
26. Control variables
Pressure: Pressure signal is the feedback signal (Pressure Preset)
Volume: Volume signal is the feedback signal. usually measure the flow
and turn it into volume signal electronically. (volume preset)
Time
Flow
Combinations
29. Basic Modes of Ventilation
Controlled Mechanical Ventilation
Assist Control Ventilation
Intermittent Mandatory Ventilation
Synchronized Intermittent Mandatory Ventilation
Pressure Support
Combinations
30. Controlled mandatory ventilation
(CMV)
The ventilator delivers
Preset tidal volume (or pressure) at a time triggered (preset) respiratory
rate.
As the ventilator controls both tidal volume (pressure) and respiratory rate,
the ventilator “controls” the patients minute volume.
Pressure
34. Controlled mandatory ventilation
(CMV)
Patient can not breath spontaneously
Patient can not change the ventilator respiratory rate
Suitable only when patient has no breathing efforts
Disease or
Under heavy sedation and muscle relaxants
35. Controlled mandatory ventilation
(CMV)
Asynchrony and increased work of breathing.
Not suitable for patient who is awake or has own respiratory efforts
Can not be used during weaning
37. Time (sec)
Control ventilation (CMV) Assist / control ventilation
Pressure
Control Control Assisted
Assist Control Ventilation
38. Control ventilation (CMV)
Assist / control ventilation
Pressure
Assist Control Ventilation
A set tidal volume (volume control) or a set pressure and time (pressure
control) is delivered at a minimum rate
Additional ventilator breaths are given if triggered by the patient
Mandatory breaths: Ventilator delivers preset volume and preset flow rate
at a set back-up rate
Spontaneous breaths: Additional cycles can be triggered by the patient but
otherwise are identical to the mandatory breath.
39. Assist Control Ventilation
Tidal volume (VT) of each delivered breath is the same, whether it is
assisted breath or controlled breath
Minimum breath rate is guaranteed (controlled breaths with set VT)
Control ventilation (CMV)
Assist / control ventilation
Pressure
41. Time (sec)
Patient / TimeTriggered, Pressure Limited, Time Cycled Ventilation
Pressure
Flow
Volume
Set PC level
Time-Cycled
Pt triggered Time triggered
Assist Control Ventilation (Pressure)
42. Patient / Time triggered, Flow limited, Volume cycled Ventilation
Assist Control Ventilation (Volume)
Time (sec)
Flow
Pressure
Volume
Preset VT
Volume Cycling
43. Assist Control Ventilation
Asynchrony taken care of to some extent
Low work of breathing, as every breath is
supported and tidal volume is guaranteed.
Hyperventilation
Respiratory alkalosis.
Natural breaths are not allowed
Breath stacking
High volumes and pressures
Control ventilation (CMV)
Assist / control ventilation
Pressure
44. Assist Control Ventilation
Hyperventilation and breath stacking can usually be
overcome by choosing optimal ventilator settings and
appropriate sedation.
Control ventilation (CMV)
Assist / control ventilation
Pressure
46. Intermittent Mandatory Ventilation
(IMV)
Pressure
Machine breaths are delivered at a set rate (volume or pressure
limit)
Patient is allowed to breath spontaneously from either a
demand valve or a continuous flow of gases but not offering
any inspiratory assistance.
Time (sec)
50. Intermittent Mandatory Ventilation
(IMV)
Pros:
Freedom for natural spontaneous
breaths even on machine
Lesser chances of hyperventilation
Cons:
Asynchrony
Random chance of breath stacking.
Increase work of breathing
Random high airway pressure
(barotrauma) and lung volume
(volutrauma)
Setting appropriate pressure limit is important to reduce the risk of barotrauma
52. Synchronized Intermittent Mandatory
Ventilation
Ventilator delivers either patient triggered assisted breaths or time
triggered mandatory breath in a synchronized fashion so as to avoid
breath stacking
If the patient breathes between mandatory breaths, the ventilator will
allow the patient to breathe a normal breath by opening the demand
(inspiratory) valve but not offering any inspiratory assistance.
53. Synchronization windowPressure
Time interval just prior to time triggering in which the ventilator
is responsive to the patient’s inspiratory effort.
Time (sec)
Time trigerring
54. SIMVPressure
Patient trigerred
synchronized breath
If the patient makes a spontaneous inspiratory effort that falls in sync window,
the ventilator is patient triggered to deliver an assisted breath and will count it
as mandatory breath
Time trigerred
mandatory breath
56. SIMVPressure
Patient trigerred
synchronized breath
if patient does not make an inspiratory effort then ventilator will deliver a
time triggered mandatory breath.
Time trigerred
mandatory breath
If the pt triggers outside this window, vent will allow this spontaneous breath to occur by opening the
demand (inspiratory) valve but does not offer any inspiratory assistance.
59. Synchronized Intermittent Mandatory
Ventilation (SIMV)
It allows patients to assume a portion of their ventilatory drive:
Weaning is possible
Greater work of breathing than AC ventilation and therefore some
may not consider it as the initial ventilator mode
Friendly cardiopulmonary interaction: Negative inspiratory
pressure generated by spontaneous breathing leads to increased
venous return, which theoretically may help cardiac output and
function
60. Pressure Support Ventilation
Pressure (or Pressure above PEEP) is the setting variable
No mandatory breaths
Applicable on Spontaneous breaths: a preset pressure assist,
Flow cycling: terminates when flow drops to a specified fraction
(typically 25%) of its maximum.
Patient effort determines size of breath and flow rate.
61. Pressure Support Ventilation
Pressure (or Pressure above PEEP) is the setting variable
No mandatory breaths
Applicable on Spontaneous breaths: a preset pressure assist,
Flow cycling: terminates when flow drops to a specified fraction (typically
25%) of its maximum.
Patient effort determines size of breath and flow rate
62. Pressure Support Ventilation
Pressure (or Pressure above PEEP) is the setting variable
No mandatory breaths
Applicable on Spontaneous breaths: a preset pressure assist,
Flow cycling: terminates when flow drops to a specified fraction (typically
25%) of its maximum.
Patient effort determines size of breath and flow rate.
63. Pressure Support Ventilation
It augments spontaneous VT decreases spontaneous rates and WOB
Used in conjunction with spontaneous breaths in any mode of ventilation.
No guarantee of tidal volume with changing respiratory mechanics,
No back up ventilation in the event of apnea.
64. Pressure Support Ventilation
Provides pressure support to overcome the increased work of breathing
imposed by the disease process, the endotracheal tube, the inspiratory
valves and other mechanical aspects of ventilatory support
Allows for titration of patient effort during weaning.
Helpful in assessing extubation readiness
65. SIMV + PS VentilationPressure
Spontaneous breath with PS
Inspiration: the change from expiration to inspiration. Inspiratory valve opens and expiratory valve is closed
Inspiratory pause: inspiratory valve and expiratory valve closed
Expiration: Inspiratory valve closed and expiratory valve open
Expiratory pause: Inspiratory valve and expiratory (or PEEP) valve closed at end of expiration
When the inspiratory valve is opened, gas from the compressor will rush into the lung (at a compressed pressure of 60 lb/in2) unless limited by some ventilator mechanism. The term 'limit' denotes the factor which controls the inspiration inflow. It implies that the set limit cannot be overcome and yet, on reaching this The ventilator can either deliver gas at a fixedflow rate and pattern or at a fixed
pressure during inspiration. In flow-limited breathing, a fixed inspiratory flow rate
and pattern is set by the clinician and maintained throughout inspiration. As the
flow is assured, the patient will receive an adequate tidal volume for a given
inspiratory time. However, the airway pressure will rise to whatever level is
required to deliver the flow and there is therefore an increased likelihood of
The ventilator delivers the preset tidal volume at a time triggered (preset) respiratory rate. As the ventilator controls both tidal volume and respiratory rate, the ventilator “controls” the patients minute volume. The patient can not change the ventilator respiratory rate or breath spontaneously. Thus this mode should be applied only when patient has no breathing efforts either due to disease or under heavy sedation and muscle relaxants otherwise it will lead to asynchrony and increased work of breathing.
Tidal volume (VT) of each delivered breath is the same, whether it is patient triggered (assist) or ventilator triggered (control)
If the patient does not initiate a breath before a requisite period of time determined by the set respiratory rate (RR), the ventilator will deliver the set VT
Regardless of whether the breath is patient-triggered or time-triggered, the exhalation valve closes and the ventilator generates inspiratory flow at a set rate and pattern (flow limited). Inspiratory flow lasts until the set VT is delivered at which time the breath is cycled-off (volume-cycled).
Thus, the AC mode is patient- or time-triggered, flow-limited, and volume-cycled. The airway pressures generated by chosen ventilator settings are determined by the compliance of the respiratory system and the resistance of the airways.
tachypnea could lead to hyperventilation and respiratory alkalosis. Breath stacking can occur when the patient initiates a second breath before exhaling the first. The results are high volumes and pressures in the system.