2. •
Sickest patients (multiple diagnosis, multi organ failure,
immunocompromised, septic and trauma)
•
Move less
•
Malnourished
•
More obtunded (Glasgow coma scale)
•
May be associated Diabetics and Heart failure
3.
“Repeated or continuous observations or measurements of the
patient, physiological function, and the function of life support
equipment, for the purpose of guiding management decisions,
including when to make therapeutic interventions, and
assessment of those interventions”
A patient monitor may not only alert caregivers to potentially lifethreatening events; many provide physiologic input data used to
control directly connected life-support devices.
4.
There are at least four categories of patients who need physiologic monitoring:
1. Patients with unstable physiologic regulatory systems; for example, a patient whose respiratory
system is suppressed by a drug overdose or anesthesia.
2. Patients with a suspected life-threatening condition; for example, a patient who has findings
indicating an acute myocardial infarction (heart attack).
3. Patients at high risk of developing a life-threatening condition; for example, patients immediately
post open-heart surgery, or a premature infant whose heart and lungs are not fully developed.
4. Patients in a critical physiological state; for example, patients with multiple trauma or septic
shock.
5.
Common to all patients
◦ Pulse oxymetry
◦ BP monitoring
◦ Non invasive
Invasive
CVP
◦
◦
◦
◦
ECG
Temprature
Urine output
ABG
8. Sensor Application
Apply sensor on forehead at angle
Circle #1: Centered, 2 inches above nose
Circle #4: Directly above eyebrow
Circle #3: On temple, between corner of eye
and hairline
Press around the edges of each circle to assure adhesion
Press each circle for 5 seconds
11. Mixed venous saturation
◦ Measured with PA catheter
◦ Normal is 65-75%
◦ Low SvO2 may indicate inadequate tissue O2 delivery (even if arterial O2 is OK)
Lactates
◦ Increased lactate concentration and metabolic acidosis suggests anaerobic
metabolism and inadequate tissue oxygenation. lactate also increases with liver
failure and sepsis,
ABG monitoring
◦ Monitors acid-base balance, PaO2, and PaCO2
Gastric tonometry
Used to detect shock-induced splanchnic ischemia by measure gastric luminal PCO2 and
deriving the mucosal pH
14.
NM- monitor: standard method of monitoring drug induced NM block is to apply a
series of four low frequency(2Hz) electrical pulse to ulnar nerve at forearm, and
observe for adduction of thumb.
Total absence of thumb adduction is evidence of excessive block.
Desired goal is 1or 2 preceptible twitches, and drug infusion is adjusted to
achieve end point.
Capnography
◦ End-tidal CO2 concentration is close to artrial PaCO2 levels
◦ Indicates the adequacy of alveolar ventilation
Pain scoring
Spirometry
Plasma level of various drugs
X-ray chest
15.
Global measures
◦ Reflect the adequacy of total tissue perfusion but could be normal
with local perfusion abnormalities
◦ SvO2 <55% indicates global tissue hypoxia.
Organ-specific Measures
◦ Urine flow
A sensitive indicator of renal perfusion provided the kidneys aren’t
damaged
Normal is 1ml/kg
◦ Core-peripheral temperature
The gradient between peripheral (skin) temp and core (rectal) is
often used as an index of peripheral perfusion
The less perfusion, the colder the periphery
17. 1- Acute respiratory failure due to:
Mechanical failure, includes neuromuscular diseases as Myasthenia Gravis,
Guillain-Barré Syndrome, and Poliomyelitis (failure of the normal respiratory
neuromuscular system)
Musculoskeletal abnormalities, such as chest wall trauma (flail chest)
Infectious diseases of the lung such as pneumonia, tuberculosis.
2- Abnormalities of pulmonary gas exchange as in:
Obstructive lung disease in the form of asthma, chronic bronchitis or emphysema.
Conditions such as pulmonary edema, atelectasis, pulmonary fibrosis.
Patients who has received general anesthesia as well as post cardiac arrest patients
often require ventilatory support until they have recovered from the effects of the
anesthesia or the insult of an arrest.
20. Negative-pressure ventilators
Early negative-pressure ventilators were known as “iron lungs.”
The patient’s body was encased in an iron cylinder and negative pressure was
generated .
Intermittent short-term negative-pressure ventilation is sometimes used in patients
with chronic diseases.
The iron lung are still occasionally used today.
Positive-pressure ventilators are deliver gas to the patient under positive-pressure,
during the inspiratory phase.
23.
ventilator provides the patient with a pre-set tidal volume at a pre-set rate .
Patient may initiate a breath on his own, but the ventilator assists by
delivering a specified tidal volume to the patient. pt can initiate breaths that
are delivered at the preset tidal volume.
Pt. can breathe at a higher rate than the preset number of breaths/minute.
The total respiratory rate is determined by the number of spontaneous
inspiration initiated by the patient plus the number of breaths set on the
ventilator.
In A/C mode, a mandatory (or “control”) rate is selected.
If the patient wishes to breathe faster, pt. can trigger the ventilator and
receive a full-volume breath.
24.
Often used as initial mode of ventilation
When the patient is too weak to perform the work of breathing (e.g.,
when emerging from anesthesia).
Disadvantages:
Hyperventilation,
25.
The ventilator provides the patient with a pre-set number of
breaths/minute at a specified tidal volume and FiO2.
In between the ventilator-delivered breaths, the patient is able to
breathe spontaneously at his own tidal volume and rate with no
assistance from the ventilator.
However, unlike the A/C mode, any breaths taken above the set
rate are spontaneous breaths taken through the ventilator circuit .
The tidal volume of these breaths can vary drastically from the tidal volume
set on the ventilator, because the tidal volume is determined by the
patient’s spontaneous effort.
26.
Adding pressure support during spontaneous breaths can minimize the
risk of increased work of breathing.
Ventilators breaths are synchronized with the patient spontaneous
breathe( no fighting).
Used to wean the patient from the mechanical ventilator.
Weaning is accomplished by gradually lowering the set rate and
allowing the patient to assume more work
27. Ingento EP & Drazen J: Mechanical Ventilators, in Hall JB, Scmidt GA, &
Wood LDH(eds.): Principles of Critical Care
28.
Ventilation is completely provided by the mechanical ventilator with
a preset tidal volume, respiratory rate and oxygen concentration
Ventilator totally controls the patient’s ventilation i.e. the ventilator
initiates and controls both the volume delivered and the frequency
of breath.
Client does not breathe spontaneously.
Client can not initiate breathe
29.
30.
The PCV mode is used
◦ If compliance is decreased and the risk of barotrauma is high.
◦ It is used when the patient has persistent oxygenation problems
despite a high FiO2 and high levels of PEEP.
The inspiratory pressure level, respiratory rate, and inspiratory–
expiratory (I:E) ratio must be selected.
31.
Sedation and the use of neuromuscular blocking agents are frequently
indicated, because any patient–ventilator asynchrony usually results in
profound drops in the SaO2.
This is especially true when inverse ratios are used. The “unnatural” feeling of
this mode often requires muscle relaxants to ensure patient–ventilator
synchrony.
Inverse ratio ventilation (IRV) mode reverses this ratio so that inspiratory
time is equal to, or longer than, expiratory time (1:1 to 4:1).
Inverse I:E ratios are used in conjunction with pressure control to improve
oxygenation by expanding stiff alveoli by using longer distending times,
thereby providing more opportunity for gas exchange and preventing
alveolar collapse.
32.
The patient breathes spontaneously while the ventilator applies a predetermined amount of positive pressure to the airways upon inspiration.
Pressure support ventilation augments patient’s spontaneous breaths with
positive pressure boost during inspiration i.e. assisting each spontaneous
inspiration.
Helps to overcome airway resistance and reducing the work of breathing.
Indicated for patients with small spontaneous tidal volume and difficult to wean
patients.
Patient must initiate all pressure support breaths.
Pressure support ventilation may be combined with other modes such as
SIMV or used alone for a spontaneously breathing patient.
33.
The patient’s effort determines the rate, inspiratory flow, and tidal
volume.
In PSV mode, the inspired tidal volume and respiratory rate must be
monitored closely to detect changes in lung compliance.
It is a mode used primarily for weaning from mechanical ventilation.
34.
Constant positive airway pressure during spontaneous breathing
CPAP allows the nurse to observe the ability of the patient to
breathe spontaneously while still on the ventilator.
CPAP can be used for intubated and nonintubated patients.
It may be used as a weaning mode and for nocturnal ventilation
(nasal or mask CPAP)
36.
Prevent atelactasis or collapse of alveoli
Treat atelactasis or collapse of alveoli
Improve gas exchange & oxygenation
Treat hypoxemia refractory to oxygen therapy.(prevent oxygen
toxicity
Treat pulmonary edema ( pressure help expulsion of fluids from
alveoli
37.
BiPAP is a noninvasive form of mechanical ventilation provided by
means of a nasal mask or nasal prongs, or a full-face mask.
The system allows the clinician to select two levels of positivepressure support:
An inspiratory pressure support level (referred to as IPAP)
An expiratory pressure called EPAP (PEEP/CPAP level).
39.
Awake and alert
Hemodynamically stable, adequately resuscitated, and not requiring
vasoactive support
Arterial blood gases (ABGs) normalized or at patient’s baseline
- PaCO2 acceptable
- PH of 7.35 – 7.45
- PaO2 > 60 mm Hg ,
- SaO2 >92%
- FIO2 ≤40%
Positive end-expiratory pressure (PEEP) ≤5 cm H2O
Vt 5 ml / kg
VC > 10- 15 ml / kg
PEP (positive expiratory pressure) > - 20 cm H2O ( indicates patient’s ability
to take a deep breath & cough),
41.
Movement
Sequential Compression Devices
Pharmacologic treatment
◦ UFH decrease incidence of DVT by 20%.(initial bolus dose of 80 IU/kg
and follow with continuous infusion of 18IU/kg/hr, check PTT 6hr after
start of infusion)
◦ LMWH decrease incidence of DVT by 30% over UFH .
42.
Type of fluid that is best designed to correct a specific problem with fluid
balance is:
Crystalloid fluids are designed to fill extracellular space are would be use in
pt. With dehydration, (loss of interstitial &intravascular fluid).
Colloid fluid are designed to expand the plasma volume and are appropriate
for pt. With hypovolemia due to blood loss.
Albumin containing colloid fluid are appropriate for pt. With hypovolemia
associated with hypoalbuminemia.
43.
Regular oral and teeth cleaning should be done at lest 12 hrly.
Prevent aspiration
1. Positioning—lateral position with head turned to the side or side-lying.
Position back of head on a pillow so that the face tips forward and fluid/
secretions will flow out of the mouth, not back into the throat.
Place a bulb syringe or suction machine with suction equipment nearby.
Care of eyes :
Clean from inner to outer conthus with wet (normal saline), warm cotton
ball or compress.
Use artificial tear solution or normal saline every four hour, if blink reflex is
absent.
Care for eye glass, contact lens.
44.
Repositioning the ETT move it to a different location on the patient’s mouth avoiding
areas of breakdown and ulceration.
Skin preparation is required when using tapes or devices with adhesives. This may
include:
-Shaving (consent may be required before shaving),
cleaning and drying.
- Preparation with skin prep solutions such antiseptic.
If an ETT requires advancing or withdrawing, the patient’s oral airway should be
suctioned and then the cuff deflated prior to moving the ETT.
ETT cuff pressure is monitored to minimize the risk of tracheal necrosis and to
reduce aspiration of oral secretions into the airway.
45.
ETT cuff pressure should be maintained at a minimum of 25 cmH2O to reduce the risk of
secretions leaking into the trachea and bronchi.
Maximum cuff pressure is 30 cmH20 to avoid the risk of tracheal necrosis.
The measuring device connects to the one way valve of the ETT pilot balloon and the
pressure is read at end of inspiration.
ETT suctioning should be performed at least 4-6hrly to ensure airway patency.
Perform hand hygiene prior to using the in-line suction.
Always wear gloves and eye protection.
46.
Suctioning is the mechanical aspiration of pulmonary secretions from a
patient with an artificial airway in place.
Indications
◦ Inability to cough effectively
◦ Sputum plugging
To assess tube patency
Contraindication
Frank haemoptysis
Severe brochospasm
Undrained pneumothorax
Compromised cardiovascular system
47.
The suction catheter used must be less than half the diameter of
endotracheal tube.
The vacuum pressure should be as low as possible. (60-150mmHg)
Suction should never be routine, only when there is an indication
Hazards of suctioning
Mucosal trauma
Cardiac arrhythmias
Hypoxia
Raised intracranial pressure
48.
To be given every four hours
Skin around tracheostomy tube cleaned with betadine
Inner cannula of metal tracheostomy
-cleaned under running water
-immersed in hydrogen peroxide for 10mts
- washed with water and gauze wick
-boiled for 10 mints and replaced once
It is cool
49.
Nosocomial infections
◦ occur in approximately 10% of ICU patients at a rate of 21 to 25
infections per 1000 ICU patient-days.
◦ The most common nosocomial infections in medical ICUs are
urinary tract infections (31%), followed by pneumonia (27%) and
primary bloodstream infections (19%).
50.
VAP is defined as pneumonia developing in mechanically ventilated patients
after more than 48 hours of intubation, with no clinical evidence suggesting
the presence or probable development of pneumonia at the time of initial
intubation.
VAP is a leading cause of morbidity and mortality in mechanically ventilated,
critically ill patients.
51.
The incidence of VAP is estimated to be 10% to 25%, and the estimated mortality
rate from VAP is 5% to 27%. VAP also increases hospital length of stay and cost.
The diagnosis of VAP is challenging. presumptive diagnosis of pneumonia is
made when fever, leukocytosis, purulent secretions, and a new infiltrate on chest
radiography develop and when bacteria are isolated by nonquantitative analysis of
endotracheal aspirates.
These nonspecific diagnostic criteria may lead to unnecessary antibiotic use,
increased hospital cost, emergence of resistant microorganisms, and a potential
delay in diagnosis of the true cause of the fever.
52. Host Factors Factors that facilitate reflux
& aspiration into the lower RT
•
Elderly
•
Severe Illness
•
Underlying Lung Disease
- Mechanical ventilation
•
Depressed Mental Status
- Tracheostomy
•
Immunocompromising
- Use of a Nasogastric Tube
Conditions or Treatments
- Supine Position
•
Viral Respiratory Tract
Factors that impede normal
Infection
Pulmonary Toilet
Colonisation - Abdominal or thoracic surgery
•
Intensive Care Setting
- Immobilisation
•
Use of Antimicrobial Agents
•
Contaminated hands
•
Contaminated Equipment
02/07/14
Dr.T.V.Rao MD
52
53.
Early onset VAP is caused by Streptococcus pneumonia, H influenza,
Moraxella catarrhalis and methicillin-sensitive Staphylococcus
aureus (MSSA).
Late onset VAP is caused commonly by Pseudomonas aeruginosa,
Acinetobacter, Enterobacter species and methicillin
resistant staphylococcus aureus (MRSA).
VAP is frequently polymicrobial and gram negative bacilli are the
predominant organism’s isolated.
54.
Prevention of Ventilator-Associated Pneumonia
Gastric pH
The use of sucralfate, an agent that does not increase gastric pH, may be preferable
to H2 receptor antagonists or proton pump inhibitors. Three studies found decreased
mortality rates in patients treated with sucralfate rather than H 2 receptor antagonists or
proton pump inhibitors.
Positioning
Positioning of the head of the bed at 30 degrees is the most cost-effective intervention
for prevention of VAP. This position results in decreased gastroesophageal reflux.
Subglottic Aspiration of Secretions
Pooling of secretions above the endotracheal tube cuff may increase the volume of
bacteria that enter the airways. Removal of these secretions by continuous aspiration
in the subglottic region requires the use of a specialized endotracheal tube with a
second lumen that permits a suction catheter to exit proximal to the endotracheal tube
cuff.
55.
Aminoglycosides and quinolones are bactericidal in a concentration dependent
fashion.
In addition these agents have a prolonged postantibiotic effect (PAE), allowing
them to suppress bacterial growth even after their concentrations are below
target level.
vancomycin and the beta-lactams (penicillins, cephalosporins, aztreonam) are
also bactericidal but act in a time-dependent rather than in a concentrationdependent fashion, do not possess significant postantibiotic effect against gram
negative bacilli,
Generally speaking, empirical therapy should be commenced once NP is
suspected and altered as microbiologic data become available
56.
Catheter-Related Bloodstream Infections
It is estimated that more than 5 million CVCs are inserted every year in the United States.
Unfortunately, more than 15% of patients have complications from these lines.
Infectious complications are reported to occur in 5% to 26% of patients with CVCs.
The mortality rate attributable to CRBSIs ranges from 12% to 25%,
Prevention of Central Venous Catheter Infections
Antibiotic-Impregnated Central Venous Catheters
Examine the efficacy of antimicrobial-impregnated catheters in an effort to decrease the
incidence.
CVCs coated with the antimicrobials chlorhexidine and silver sulfadiazine or impregnated
with the antibiotics minocycline and rifampin are commercially available.
Chlorhexidine/sulfadiazine-coated catheters lowered the rate of bloodstream infection
from 7.6 to 1.6 infections per 1000 catheter-days (P = .03).
57.
The use of antimicrobial-impregnated catheters should be considered in all
critically ill patients who require long-term (at least 3 days) indwelling central
venous access.
Immunocompetent patients who will be catheterized for less than 3 or 4
days may not need these catheters because infection is rare during this
period.
Sterile Technique
Optimal sterile technique is the most cost-effective means of reducing the
incidence of central line colonization and CRBSI.
Use of maximal sterile barrier precautions such as mask, cap, sterile gown,
sterile gloves, and a large sterile drape.
Use of chlorhexidine solution for skin decontamination reduces the risk of
catheter colonization and is therefore preferred over the use of povidoneiodine solution.
Ultrasound Guidance
With the development of portable, inexpensive ultrasound machines, for
reducing the complications associated with central venous cannulation .
58.
Ultrasound guidance has been shown to reduce the number of complications,
unsuccessful attempts, and time required for insertion of an internal jugular vein catheter,
Clinical trials assessing whether use of ultrasound can decrease the incidence of central
venous line infections remain to be completed, but this technology can decrease the
number of attempts required to locate the internal jugular vein and should be used
routinely when available.
Duration
The need for a CVC should be reassessed daily, and unnecessary catheters should be
removed because the probability of catheter-related infections increases with time.
The risk of infection with catheterization stays relatively low until about the fifth to seventh
days and then increases.
61.
Treatment of perceived & prevention of anticipated pain
Opiates – principal agents in ICU
- potent / lack of ceiling effects
- mild anxiolytic & sedative
- relieves air hunger & suppress cough in resp failure
- improved patient – ventilator synchrony
- effective antagonist - naloxone
Lack amnesic effects /additional sedatives required
62.
Morphine & Hydromorphine accumulation of metabolites
Pethidine - only for shivering/ drug induced rigors
Codeine/oxycodone – oral - not effective
Methadone for c/c pain/ complex pain syndromes
Fentanyl / sufentanil/ remifentanil/ alfentanil popular
Flexibility of choice essential
63.
In the agitated, ventilated & for procedure discomfort
To avoid self extubation & removal of catheters
NM blockade mandates analgesia & sedation
Control of pain before sedation
All have side effects – dose dependent
Analgesics are not sedatives/ Sedatives are not analgesics
64.
Benzodiazepines most popular for sedation
Short term sedation – midazolam<3h (amnesic/ hypotension)
- propofol – infusion syndrome/ pancreatitis
Long term – lorazepam<20h /diazepam>96h (not for infusion)
Delirium – haloperidol - neurolept syndrome/torsade pointes
Antagonist- flumazenil 0.2mg-1mg (withdrawal seizures)
65.
Dexmedetomidine- ∝2 agonist/ GABA sparing effects
Short term analgesia, sedation, anxiolysis
No cardio-respiratory depression/ easily arousable
Continuous infusion in ventilated /prior,during &post- extbn
No amnesia/ crosses placenta/
Antagonised by atipamezole – combinations useful in ICU
66.
Assess levels to vary according to course of ICU stay
Observational scales - 4 levels – min, mod, deep, GA
Ramsay sedation scale 1-6 (vocal, glabellar tap)--aim for 3-4
Direct information- ideal to assess analgesia & sedation
BIS – for deep sedated & paralysed
68.
Cleaning more Important than
Disinfection and Sterilization
Cleaning
Removes
contaminants,
Dust, organic matter,
Disinfection
Reduces number of
microbes
69.
Sterilization is absolute,
removes microbes and spores
too.
To achieve Sterilization is
Expensive, not sustainable,
many times not needed.
An effective Disinfection
reduces the infections
drastically.
70.
To Sterilization of ICU formaldehyde gas (bactericidal &
sporicidal,viricidal) is widely employed as it is cheaper for
sterilization of huge areas like operation theatres and ICU.
Formaldehyde kills the microbes by alkylating the amino acids and
sulfydral group of proteins and purine bases.
In spite of the gas being hazardous continues to be used in several
developing countreis
72.
A Chemical compound VIRKON gaining importance as non Aldehyde
compound.
Virkon proved to be safe
Virucidal
Bactericidal,
Fungicidal
Mycobactericidal
used as :
As a Chemical disinfectant.
Disinfects Medical devices.
Disinfects Laboratory equipment.
Decontaminate spillages with Blood and body fluids.
Finding usefulness in replacing autoclaving and saving time.
73.
Sterile water for nebulizer & humidifier
Pneumatic circuit to be changed when visibly soiled
Use heat & moisture exchange filter
Condensate in tubing to be drained only to the
water traps
Humidifier domes (auto claved or sterilized by 2%
glutaraldehyde)
78.
ICU rehabilitation has been shown to accelerate recovery.
Early mobilization for unconscious patients starts right from turning the
patient every two hours.
Graded exercises can be started as soon as the patient regains
consciousness.
Activity is required to maintain sensory input, comfort, joint mobility
and healing ability .
Activity minimizes the weakness caused by loss of up to half the
patients muscle mass.
Graded ambulation can be started depending on patients condition
79.
A treatment intervention employed for improving pulmonary
hygiene including positioning, chest percussion, vibration and
manual hyperinflation to assist in mobilizing secretions in the lungs
from the peripheral airways into the more central airways so that
they can be expectorated or suctioned.
Prevent accumulation of secretions
Improve mobilization and drainage of secretions
Promote relaxation to improve breathing patterns
80.
Prophylactic
- Pre-operative high risk surgical patient
- Post-operative patient who is unable to
mobilize secretions
- Neurological patient who is unable to cough
effectively
- Patient receiving mechanical ventilation who has a
tendency to retain secretions
- Patients with pulmonary disease,
who needs to improve bronchial hygiene
81.
Therapeutic
- Atelectasis due to secretions
- Retained secretions
- Abnormal breathing pattern due to primary or
secondary pulmonary dysfunction
- COPD and resultant decreased exercise
tolerance
- Musculoskeletal deformity that makes breathing
pattern and cough ineffective
83.
Decreased minute ventilation
◦ Respiratory rate
◦ Tidal volume
Treatment:
◦ Increase respiratory rate: assure I-time not too short as rate
increased
◦ Increase tidal volume
◦ Allow permissive hypercarbia
Editor's Notes
USE THIS SLIDE FOR BIS A-2000 OR FOR BIS WITH PATIENT MONITORING SYSTEMS OTHER THAN GE OR PHILIPS
(Hide the Philips and GE slides)
As you can see, the BIS technology is available as a stand-alone monitor or in modular format integrated into leading patient monitoring systems.
To monitor a patient, you will need a monitor or a module and a sensor.
The sensor, placed on the patient’s forehead, detects the electrical activity of the brain, or EEG.
The characteristic changes in the EEG are evaluated by the monitor’s sophisticated algorithm, and an objective measure of the sedative drug effect is displayed as the BIS value.
The EEG information, from which the BIS value is derived, is obtained byplacing the Sensor on the patient’s forehead
It can be place on either side of the patient’s forehead.
It connects to the patient interface cable
The Sensor:
Is an electrode strip that is designed to pick up the typically very small, or low amplitude, EEG signal
Is designed with adhesive to give good contact with patient skin
Has self prepping electrodes, eliminating extensive skin preparation. Each of the electrodes contains a pre-filled conductive gel to allow for conduction of the EEG signal
Has a 4th electrode placed over the eye which improves artifact/EMG resistance (usually secondary to patient muscle movement) for a more accurate and precise measure of sedation
Reads the frontal montage – single channel EEG
Is Single-use, to be changed every 24 hours. The Extend Sensor has date/time area to record time of sensor application
Is Latex-free
Ref: Ingento EP and Drazen J: Mechanical ventilators, in Hall JB, Scmidt GA, and Wood LDH(eds.): Principles of Critical Care. New York, McGraw-Hill, Inc., 1992, p.146.
(Would we also want to put slides with pressure mode graphs as well to show the different flow characteristics ??)
During SIMV, the ventilator divides time by the set rate to determine cycle-length. During the early part of this cycle, the patient may breath spontaneously without support. During the terminal phase of this cycle (% varies by manufacturer) the ventilator will synchronize a full breath with detected effort by the patient.