A brief introduction to mechanical ventilation. contains details on the various variables, modes and settings on the mechanical ventilator. a simple explanation of what seems to be so complicated.
Patient ventilator interactions during mechanical ventilationDr.Mahmoud Abbas
Patient Ventilator Interaction during Mechanical Ventilation lecture presented by Dr.Lluis Blanch at Pulmonary Critical Care Egypt Meeting and Exhibition, January 2014. www.pccmegypt.com
A mechanical ventilator is a machine that helps a patient breathe (ventilate) when they are having surgery or cannot breathe on their own due to a critical illness. The patient is connected to the ventilator with a hollow tube (artificial airway) that goes in their mouth and down into their main airway or trachea
An excellent tool to treat refractory hypoxia. Target audience are ICU junior physicians and Respiratory Therapists. It will take away the fear of "What is APRV?" from your hearts and you will feel ready to give it a try.
Patient ventilator interactions during mechanical ventilationDr.Mahmoud Abbas
Patient Ventilator Interaction during Mechanical Ventilation lecture presented by Dr.Lluis Blanch at Pulmonary Critical Care Egypt Meeting and Exhibition, January 2014. www.pccmegypt.com
A mechanical ventilator is a machine that helps a patient breathe (ventilate) when they are having surgery or cannot breathe on their own due to a critical illness. The patient is connected to the ventilator with a hollow tube (artificial airway) that goes in their mouth and down into their main airway or trachea
An excellent tool to treat refractory hypoxia. Target audience are ICU junior physicians and Respiratory Therapists. It will take away the fear of "What is APRV?" from your hearts and you will feel ready to give it a try.
This slide include information regarding ventilators, modes of ventilators , its parts, weaning process, nursing care of patient in mechanical ventilation.
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.
HERE IS A SEMINAR BASED ON ALL THE NEWER MODES OF MECHANICAL VENTILATION .
MY SINCERE APOLOGIES , BECAUSE I HAD TO TAKE INFORMATION FROM OTHERS SLIDES TOO , SINCE THERE IS VERY LESS INFORMATION AVAILABLE ABOUT THIS TOPIC
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
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.
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
New Drug Discovery and Development .....NEHA GUPTA
The "New Drug Discovery and Development" process involves the identification, design, testing, and manufacturing of novel pharmaceutical compounds with the aim of introducing new and improved treatments for various medical conditions. This comprehensive endeavor encompasses various stages, including target identification, preclinical studies, clinical trials, regulatory approval, and post-market surveillance. It involves multidisciplinary collaboration among scientists, researchers, clinicians, regulatory experts, and pharmaceutical companies to bring innovative therapies to market and address unmet medical needs.
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
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
263778731218 Abortion Clinic /Pills In Harare ,sisternakatoto
263778731218 Abortion Clinic /Pills In Harare ,ABORTION WOMEN’S CLINIC +27730423979 IN women clinic we believe that every woman should be able to make choices in her pregnancy. Our job is to provide compassionate care, safety,affordable and confidential services. That’s why we have won the trust from all generations of women all over the world. we use non surgical method(Abortion pills) to terminate…Dr.LISA +27730423979women Clinic is committed to providing the highest quality of obstetrical and gynecological care to women of all ages. Our dedicated staff aim to treat each patient and her health concerns with compassion and respect.Our dedicated group ABORTION WOMEN’S CLINIC +27730423979 IN women clinic we believe that every woman should be able to make choices in her pregnancy. Our job is to provide compassionate care, safety,affordable and confidential services. That’s why we have won the trust from all generations of women all over the world. we use non surgical method(Abortion pills) to terminate…Dr.LISA +27730423979women Clinic is committed to providing the highest quality of obstetrical and gynecological care to women of all ages. Our dedicated staff aim to treat each patient and her health concerns with compassion and respect.Our dedicated group of receptionists, nurses, and physicians have worked together as a teamof receptionists, nurses, and physicians have worked together as a team wwww.lisywomensclinic.co.za/
2. INTRODUCTION
-Mechanical ventilation is a therapeutic method that is used to either assist or replace
spontaneous breathing.
-It is indicated in patients who have developed either ventilation failure or oxygenation
failure which may be caused by one of the following pathophysiological mechanisms:
1.Increased airway resistance
2.Changes in lung compliance
3.Hypoventilation
4.V/Q mismatch
5.Intrapulmonary shunting
6.Diffusion defect.
2
4. VENTILATORY WORK
• The work that the muscles and/or the ventilator must perform is proportional to the
pressure required for inspiration times the tidal volume.
• The pressure required is referred to as the “load” either the muscles or the ventilator
has to work against.
• This is of 2 types- an ELASTIC LOAD (proportional to volume and inversely
proportional to compliance) and a RESISTANCE LOAD (proportional to the airway
resistance).
4
6. NON INVASIVE MECHANICAL
VENTILATION
• Usually provided by using a tight fitting face mask or nasal mask similar to the masks
traditionally used for sleep apnea.
• Very similar to invasive ventilation in that it supports improved gas exchange and
decreased respiratory muscle work.
• The main difference between NIV and MV is that it uses a mask or a helmet interface
rather an endotracheal tube.
• This offers the advantages of being readily taken on and off to facilitate weaning,
maintaining some ability to communicate and also avoids the complications of
sedation and ventilator associated pneumonia.
6
7. • The ideal candidate for NIV:
1. Has a strong cough and minimal secretions
2. Tolerates the interface well
3. Has a quickly reversible condition
• Useful in patients with respiratory failure from acute exacerbations of chronic
obstructive pulmonary disease.
• NIV works on the principle of bilevel positive airway pressure ventilation or pressure
support ventilation.
• It has an End Positive Airway Pressure (EPAP) and an Inspiratory Positive Airway
Pressure (IPAP).
7
8. INITIATING NIV
• The patient requires appropriate acclimatization to the interface before the initiation
• The pressures have to be titrated to the optimal levels.
• One of the strategy recommended is to start by holding the mask on the patient’s face
while talking with them and titrating up the pressures.
• The mask should then be strapped on and adjusted for optimal comfort.
• Most sensitive objective measure of response to NIV- RESPIRATORY RATE.
• All improvements should occur within the first 30-60 minutes of initiating NIV.
8
9. DISADVANTAGES OF NIV
• No direct protection of the airway
• No deep suctioning below the vocal cords
• Limited ability to apply high pressures
• Development of intolerance to the mask over time.
9
10. CONTRAINDICATIONS TO NIV
In patients with
• Restless and agitated patient
• Poor airway protection
• Copious secretions
• Recent esophageal surgery
• Cardiac or respiratory arrest
• Unstable angina and myocardial infarction
• Severe encephalopathy
• Severe GI bleed
• Hemodynamic instability
• Facial trauma or burns
• Upper airway obstruction
10
13. Cardiovascular disease : CHF, cardiac arrest, severe shock of any etiology
Others: pneumothorax, trauma, pulmonary embolism
Post operative management: for patients who are not able to be safely extubated
following the surgical procedure, either due to an underlying condition, the nature of
the surgery or complications of the surgery. Examples : Patients with
•Morbid obesity
•Post operative hypothermia
•Pre existing lung disease
•Cardiac surgery
•Gross abdominal distension
13
14. CLINICAL PARAMETERS
Obtundation or coma
Restless or agitated patient
Inability to clear secretions
Respiratory rate of >35/ minute
Rising PaCO2 (>50 mmHg) on the ABG, despite interventions
Severe hypoxemia (PaO2 <40mmHg, SaO2 <75%)
Progressive acidosis (pH < 7.30)
Hypotension
14
15. CONTROL VARIABLES
When providing ventilatory support, the mechanical ventilator can control 4 primary
variables:
PRESSURE
VOLUME
FLOW
TIME
15
16. VOLUME CONTROLLER: uses volume change as a feedback signal to control the
volume delivered. It measures volume by the displacement of the piston or bellows
that serve as the ventilator’s drive mechanism.
FLOW CONTROLLER: allows pressure to vary with changes in the patient’s
compliance and resistance while directly measuring and controlling flow. Flow may be
measured by vortex sensors, heated wire grids, Venturi pneumotachometers, strain
gauge flow sensors and other devices.
TIME CONTROLLERS: are ventilators that measure and control inspiratory and
expiratory time.
16
17. PRESSURE CONTROLLER
When the ventilator controls the trans respiratory system pressure (airway
pressure minus body surface pressure).
It can be further classified as a POSITIVE PRESSURE VENTILATOR when it
applies pressure inside the chest to expand it and once the pressure is stopped,
the patient exhales passively through the recoil of the lungs and chest wall. This
type of ventilator requires the use of a tight fitting mask or an airway.
17
18. Regardless of the type of pressure applied, the lungs expand as a result of positive
TRANS RESPIRATORY SYSTEM PRESSURE which will determine the depth and
volume of inspiration. Hence, a typical pressure controller is unaffected by changes in
the patient’s compliance or resistance.
18
19. PHASE VARIABLE
A ventilator supported breath may be
divided into four distinct phases:
I. The change from expiration to
inspiration
II.Inspiration
III.The change from inspiration to
expiration
IV.Expiration
19
20. TRIGGER VARIABLE
The variable that determines the start of inspiration in a ventilator.
Any of the four control variables may be used by the ventilator to initiate inspiration.
Time triggered breath: initiated and delivered by the ventilator when a preset time
interval has elapsed. This is determined by the respiratory rate which has been set
on the ventilator.
EX: If the ventilator respiratory rate is set at 12 breaths per minute, the time triggering
interval for each complete breath is 5 seconds and the ventilator automatically delivers
one mechanical breath every 5 seconds without regard to the patient’s breathing effort.
20
22. PRESSURE TRIGGERED
BREATH
It is initiated and delivered by the ventilator when it senses the patient’s spontaneous
(negative pressure) inspiratory effort.
Pressure triggering uses the drop in airway pressure that occurs at the beginning of a
spontaneous inspiratory effort to signal the ventilator to begin inspiration.
The amount of negative pressure below the patient’s baseline airway pressure (or
end expiratory pressure) a patient must generate to trigger the ventilator into
inspiration is the sensitivity level. The range of acceptable sensitivity levels is -1 to -
5cm of H20 below the patient’s baseline pressure.
22
24. FLOW TRIGGERED
When the patient’s inspiratory flow reaches a specific value, a ventilator supported
breath is delivered.
It is more sensitive and responsive to to a patient’s efforts
Here, a continuous flow passes through the ventilator circuit and returns to the
ventilator (delivered flow= returned flow).
As the patient initiates a breath, part of the delivered flow goes to the patient and the
return flow to the ventilator is therefore reduced. The ventilator senses this flow
differential and instantly supplies enough flow to satisfy the mechanical or
spontaneous tidal volume.
CMV, SIMV and PSV can all be flow triggered.
24
26. LIMIT VARIABLE: The variable which is not allowed to rise above a preset value
during the inspiratory time.
CYCLE VARIABLE: Inspiration ends when a specific cycle variable is reached which
will be measured by the ventilator and used as a feedback signal to end the
inspiratory flow delivery which then allows the exhalation to begin.
26
27. MODES OF MECHANICAL
VENTILATION
A ventilator mode is a set of operating characteristics that control how the ventilator
functions.
(1)Positive End Expiratory Pressure (PEEP)
(2)Continuous Positive Airway Pressure (CPAP)
(3)Bi level Positive Airway Pressure (BiPAP)
(4)Controlled Mandatory Ventilation (CMV)
(5)Assist Control (AC)
(6)Intermittent Mandatory Ventilation (IMV)
(7)Synchronised Intermittent Mandatory Ventilation (SIMV)
(8)Mandatory Minute Ventilation (MMV)
(9)Pressure Support Ventilation (PSV)
(10)Pressure Control Ventilation (PCV)
(11)Airway Pressure Release Ventilation (APRV)
(12)Inverse Ratio Ventilation (IRV)
27
29. 29
CHARACTERISTI
CS
VOLUME TARGETED
MODES
PRESSURE TARGETED
MODES
EXAMPLES CMV, A/C, SIMV PSV, PCV
VOLUME
Constant
Guarantees volume at expense of
letting airway pressure vary
Variable
Guarantees pressure at expense
of letting tidal volume vary
INSPIRATION
Terminates when the preset tidal
volume is delivered
Terminates when preset
pressure is reached
PEAK AIRWAY
PRESSURE
Variable
It increases as needed to deliver
prescribed tidal volume
Fixed
Volume delivered will decrease
with increased airway resistance
or decreased lung compliance
INSPIRATORY
FLOW RATE
Fixed
If patient breathes faster, work of
breathing increases
Variable
If patient inspires faster, variable flow
rate may match change in inspiratory
demand or may be insufficient.
31. PEEP
It increases the baseline airway pressure
or the end expiratory pressure to a value
greater than atmospheric pressure.
Indications: (a) Increased intrapulmonary
shunt (b) Decreased lung compliance (c)
refractory hypoxemia (when the patient’s
PaO2 is 60mmHg or less at an FiO2 of
50% or more)
31
32. 32
Basic principle is that PEEP
reinflates the collapsed alveoli and
maintains alveolar inflation during
exhalation. Once “recruitment” is
over, PEEP lower the alveolar
distending pressure and facilitates
gas diffusion and oxygenation.
Disadvantages: (a) decreased
venous return (b) Barotrauma (c)
Increased ICP (d) alteration in the
renal function
33. CPAP
33
PEEP applied to the airway of a
patient who is breathing
spontaneously.
When EPAP is same as IPAP,
CPAP results.
34. BIPAP
34
•Applies positive pressures to both inspiration
and expiration
•IPAP provides positive pressure breaths
which improves hypoxemia and/or
hypercapnia.
•EPAP is in essence CPAP which improves
the recruitment of the alveoli.
•Indications: chronic respiratory failure.
•It may be used in one of the following modes:
a)Spontaneous
b)Spontaneous /time (S/T)
c)Timed
•EPAP can never be increased to more than
IPAP.
35. CMV
35
The preset tidal volume is delivered at a set
time interval (time triggered respiratory rate)
Hence, the ventilator is controlling both the
tidal volume and the respiratory rate I.e it is
controlling the minute ventilation
Requires sedation
Used when the patient “fights” the ventilator
in the initial stages of ventilatory support.
Their spontaneous respiratory efforts
become asynchronous with the ventilator’s
ability to to provide adequate inspiratory
flow.
36. ASSIST CONTROL
36
The patient is allowed to increase
the ventilatory respiratory rate (i.e
assist) in addition to preset
mechanical ventilatory respiratory
rate.
Cycling mechanism: Inspiration
is terminated when a preset tidal
volume is delivered and the
ventilator is cycled to expiration.
It does not allow the patient to
take spontaneous breaths but both
the ventilatory breath and the
assist breath have the same
preset tidal volume.
37. Indications: Used as an initial setting in patients with stable respiratory drive
(spontaneous inspiratory efforts of at least 10-12/ minute)
Advantages : Patient’s work of breathing is very small when the triggering sensitivity
(pressure or flow) is set appropriately. It allows the patient to control the respiratory
rate and therefore the minute ventilation to normalize the PaCO2.
Disadvantages : Alveolar hyperventilation.
37
38. IMV
38
A mode in which the ventilator delivers the
mandatory breath and also allows the
patient breathe spontaneously at any tidal
volume the patient is capable of in
between the mandatory breaths.
39. 39
Disadvantage : BREATH STACKING- when the patient takes a
spontaneous breath while the mandatory breath is being delivered
and thus increasing the lung volume and airway pressure
significantly.
40. SIMV
40
•A mode in which the ventilator delivers the
mandatory breaths to the patient at or
near the time of a spontaneous breath.
Hence, the mandatory breaths are
synchronized with the spontaneous
breaths.
•Patient triggering might be based on
either pressure or flow.
•During the time interval just before the
mandatory breath is being delivered, the
ventilator is responsive to the patient’s
spontaneous inspiratory efforts and is
called as the SYNCHRONISATION
WINDOW.
41. In between the mandatory breaths, the patient is allowed to breathe spontaneously to
any tidal volume the patient desires. The gas source is supplied by a demand valve
which is always patient triggered and is either pressure or flow dependent.
Indications: To provide partial ventilatory support.
Advantages : (a) avoids muscle atrophy (b) reduces ventilation to perfusion
mismatch (c) facilitates weaning.
41
42. MMV
An additional function of the SIMV mode where a predetermined minute ventilation is
delivered to the patient when there is an apnea episode. Then, there will be an
automatic increase in the mandatory breath rate, thereby increasing the minute
ventilation.
42
43. PSV
43
A preset pressure is applied to the
patient’s airway for the duration of a
spontaneous breath.
It lowers the work of spontaneous
breathing and augments the tidal
volume of a spontaneous breath.
It may be used along with SIMV mode
to facilitate weaning in a difficult to
wean patient.
44. PCV
44
The pressure controlled breaths are time triggered by a preset respiratory rate and hence req
Indicated in severe ARDS.
45. SUMMARY
45
MODE FUNCTION CLINICAL USE
CONTROL
VENTILATION
Delivers preset volume or
pressure regardless of patient’s
own inspiratory efforts
Usually used for apneic patients
ASSIST
VENTILATION
Delivers breath in response to
patient efforts
Used for spontaneously
breathing patients with
weakened respiratory muscles
SIMV
Breaths are synchronized with
patient’s respiratory efforts
Used for weaning patients
PRESSURE
SUPPORT
VENTILATION
Preset pressure that augments
the patient’s inspiratory efforts
Often used with SIMV during
weaning
46. 46
MODE FUNCTION CLINICAL USE
PEEP
Positive pressure applied at the
end of expiration
Used along with A/C, CV and
SIMV to improve oxygenation by
recruitment
CPAP
Similar to PEEP but used only
spontaneously breathing
patients
Maintains constant positive
pressure in airways
47. NEGATIVE PRESSURE
VENTILATION
NEGATIVE PRESSURE VENTILATORS apply sub atmospheric pressure outside the
chest wall, which causes the chest wall to expand, and the pressure difference
between the lungs and the atmosphere causes air to flow into the lungs. Once
negative pressure is no longer applied, the patient is allowed to exhale passively to
ambient pressure.
Unless an airway obstruction is present, this type of ventilation doesn’t require an
artificial airway.
47
48. IRON LUNGS
It encloses the patient’s body except for the head and neck in a tank and the air in it
is evacuated to produce a negative pressure around the chest cage.
The tidal volume delivered is directly proportional to the negative pressure applied to
the chest wall.
Since this type of ventilation does not require intubation, it has been extensively used
to support chronic respiratory failure.
The disadvantages include poor patient access, decreased cardiac output, known as
“tank shock”
48
50. CHEST SHELL/ CUIRASS
Designed to alleviate disadvantages associated with iron lungs where only the
patient’s chest is covered and leaves the arms and lower body exposed. Best suited
for home care settings.
50
51. MECHANICAL VENTILATION
IN COPD
NIV is the first line of treatment for these patients
MV is required in patients who have a more severe form of the disease.
Indications:
• MAJOR: (any one of the following):
A. Respiratory arrest
B. Loss of consciousness
C. Psychomotor agitation requiring sedation
D. Hemodynamic instability with systolic BP <70 or >180 mmHg
E. Heart rate <50 BPM
F. Gasping for air
51
52. MINOR (any two of the following):
A. Respiratory rate >35 breath/ min
B. Worsening acidaemia or pH <7.25
C. PaO2 <40 mmHg or PaO2/ FiO2 <200mmHg despite oxygen
D. Decreased alertness
52
53. NIH NHLBI ARDS CLINICAL NETWORK
MECHANICAL VENTILATION PROTOCOL
SUMMARY
INCLUSION CRITERIA:
1. PaO2/ FiO2 < 300 (corrected for altitude)
2. Bilateral patchy, diffuse, or homogenous infiltrates consistent with pulmonary
edema
3. No clinical evidence of left atrial hypertension.
VENTILATOR SETUP AND ADJUSTMENT :
• Calculate predicted body weight- 50 (female- 45.5) + 2.3 [height-60]
53
54. • Select any ventilator mode
• Set ventilator settings to achieve an initial tidal volume of 8ml/ kg PBW
• Reduce tidal volume by 1ml/kg at intervals <2 hours until Vt= 6ml/ kg PBW
• Set initial rate to approximate baseline minute ventilation (<35 /minute)
• Adjust the Vt and RR to achieve pH and plateau pressure goals below.
54
55. WEANING:
• Criteria for conducting SPONTANEOUS BREATHING TRIAL:
1. FiO2 <0.40 and PEEP <8
2. FiO2 and PEEP values lesser than the previous day
3. SBP >90mmHg without vasopressor support
4. No neuromuscular blocking agents being used.
55
56. SPONTANEOUS BREATHING TRIAL:
If all above criteria are met and subject has been in the study for at least 12 hours,
initiate a trial of up to 120 minutes Spontaneous Breathing with FiO2 <0.5 and PEEP <5
If tolerated for at least 30 minutes, consider extubation.
If not tolerated, presume pre weaning settings.
56
57. REFERENCES
1.David WC. Clinical Application of Mechanical Ventilation 2nd edition, Delmar
Thomson Learning Inc. 2001
2. Harrison T, Kasper D. Harrison's principles of internal medicine. New York: McGraw-
Hill Medical Publ. Division; 2017.
3.Tintinalli, J. E., Stapczynski, J. S., Ma, O. J., Yealy, D. M., Meckler, G. D., & Cline, D.
(2016). Tintinalli's emergency medicine: A comprehensive study guide (Eighth
edition.). New York: McGraw-Hill Education.
4.McConachie I. Handbook of ICU Therapy. 3rd ed. Leiden: Cambridge University
Press; 2006.
57
Broadly, patients requiring mechanical ventilation may be divided into three distinct groups:
Depressed respiratory drive
Excessive ventilatory workload
Failure of ventilatory pump
DEPRESSED RESPIRATORY DRIVE:
Leads to a decrease in tidal volume, respiratory rate , or both.
Common causes: drug overdose (narcotics, sedatives, alcohol), head trauma (abnormal breathing patterns and neurogenic pulmonary edema), acute spinal cord injury (respiratory paralysis due to trauma at C1-C3 level), sleep disorders, metabolic alkalosis, neurologic dysfunction.
EXCESSIVE VENTILATORY WORKLOAD:
Causes: acute airflow obstruction (status asthmaticus, epiglottis, COPD), deadspace ventilation(pulmonary embolism, emphysema), acute lung injury (ARDS), congenital heart disease( PPH, TOF), shock (blood loss, peripheral vasodilation), increased metabolic rate (fever), decreased compliance (atelectasis, obesity, diaphragmatic hernia)
FAILURE OF VENTILATORY PUMP:
Structural dysfunction of the respiratory system to include the lung parenchyma and respiratory muscles.
Causes: flail chest, tension pneumothorax, premature babies.
NIV works on the principle of bilevel positive airway pressure ventilation or pressure support ventilation.
It has an End Positive Airway Pressure (EPAP) and an Inspiratory Positive Airway Pressure (IPAP).
The ∆P between the IPAP and EPAP is analogous to pressure support in MV. A higher ∆P helps augment respiratory muscular effort- augmenting the tidal volumes to improve carbon di oxide elimination, while decreasing the “work of breathing”.
EPAP is analogous to PEEP (positive end- expiratory pressure ) in MV
Initiating NIV:
The patient requires appropriate acclimatization to the interface before the initiation
The pressures have to be titrated to the optimal levels
One of the strategy recommended is to start by holding the mask on the patient’s face while talking with them and titrating up the pressures. The mask is then strapped on and adjusted for optimal comfort, while minimizing leaks.
Response to NIV needs to be closely monitored. The most sensitive objective measure is the RESPIRATORY RATE which should decrease as the work of breathing decreases. Also the use of accessory muscles of respiration should decrease. The oxygen saturation and pCO2 should also improve. All these improvements should occur within the first 30-60 minutes of initiating NIV.
If not, then necessary adjustments need to be made in the pressure settings and if required MV should be considered.
Adjusting the EPAP pressure:
It is similar to PEEP and has the benefits of decreasing cardiac preload and after load.
It also increases the recruitment of the alveoli with higher opening and closing pressures resulting in more surface area for gaseous exchange and improved oxygenation.
Thus EPAP can be titrated for both its respiratory and cardiovascular effects.
Generally, in congestive cardiac failure, EPAP of at least 8-10 cm of water is used and even higher pressures may be required.
Patients with COPD also benefit from the above range, due to the effect of splinting open of smaller airways allowing relief of gas trapping- similar to what patients accomplish on their own with pursed lip breathing.
Adjusting the IPAP pressure:
It is the maximum pressure the machine delivers when a respiratory effort is detected.
It is very patient specific and requires patient acclimatization.
Time triggered breath: initiated and delivered by the ventilator when a preset time interval has elapsed. This is determined by the respiratory rate which has been set on the ventilator.
EX: if the ventilator respiratory rate is set at 12 breaths per minute, the time triggering interval for each complete breath is 5 seconds and the ventilator automatically delivers one mechanical breath every 5 seconds without regard to the patient’s breathing effort
Pressure triggered breath: it is initiated and delivered by the ventilator when it senses the patient’s spontaneous (negative pressure) inspiratory effort. Pressure triggering uses the drop in airway pressure that occurs at the beginning of a spontaneous inspiratory effort to signal the ventilator to begin inspiration. The amount of negative pressure below the patient’s baseline airway pressure (or end expiratory pressure) a patient must generate to trigger the ventilator into inspiration is the sensitivity level. The range of acceptable sensitivity levels is -1 to -5cm of H20 below the patient’s baseline pressure.
Flow triggered: when the patient’s inspiratory flow reaches a specific value, a ventilator supported breath is delivered. It has been shown to be more sensitive and responsive to to a patient’s efforts than a pressure triggered breath. Here, a continuous flow passes through the ventilator circuit and returns to the ventilator (delivered flow= returned flow). As the patient initiates a breath, part of the delivered flow goes to the patient and the return flow to the ventilator is therefore reduced. The ventilator senses this flow differential and instantly supplies enough flow to satisfy the mechanical or spontaneous tidal volume. CMV, SIMV and PSV can all be flow triggered.
This mode does not deliver breaths but is used as an adjunct to CV, A/C, and sims mode.
In general, IPAP and EPAP may be set at 8 cm and 4cm of H2o respectively and then determined by the patient’s clinical and physiological response.