8. ventilator nursing care

CARE OF THE PATIENT ON VENTILATOR

CARE OF THE PATIENT ON VENTILATOR

1Prof. Dr. RS Mehta, BPKIHS

VENTILATORA mechanical ventilator is a positive or negative pressure breathing device that can maintain ventilation and oxygen delivery for a prolonged period.

Mechanical ventilation has been used for decades to support the respiratory functions of patients with various degrees of respiratory distress or failure.




PURPOSESTo maintain gas exchange in case of acute and chronic respiratory failure.

To maintain ventilatory support after CPR.

To reduce pulmonary vascular resistance.

To excrete increased CO2 production.

To give general anesthesia with muscle relaxants.


Indications for Mechanical VentilationUpper airway obstruction and Lower airway obstruction as a result of blockage.

Neuromuscular disorders as in Myasthenia gravis, Poliomyelitis, Gullian-Barre syndrome, Snake bite and inadequate reversal of anesthesia.


ContDLung diseases which prevent proper exchange of O2 and CO2 as in Chest Injuries Pneumothorax, lung Infections, COPD, Acute Respiratory Distress Syndrome (ARDS).Post-operative cardiac surgery, any other surgery, shock & trauma.Respiratory arrest. 7Prof. Dr. RS Mehta, BPKIHS

Criteria for institution of ventilator support:Normal range (adult) Ventilation indicated Parameters 10-20

5-7

65-75

75-100 > 35

< 5

< 15

50 B- Arterial blood Gases

PH PaO2 (mmHg) PaCO2 (mmHg)


Classification of VentilatorsVentilator

Positive pressure Negative pressure


NEGATIVE PRESSURE VENTILATORElongated tank, which encases the patient up to the neck. The neck is sealed with a rubber gasket, the patient's face are exposed to the room air.These exert negative pressure on the external chest decreasing the intra-thoracic pressure during inspiration, allows air to flow into the lungs, filling its volume.The cessation of the negative pressure causes the chest wall to fall and exhalation to occur.



ContdThese are simple to use and do not require intubations of the airway; consequently, they are especially adaptable for home use.It is used mainly in chronic respiratory failure associated with neuromuscular conditions such as poliomyelitis, muscular dystrophy and myasthenia gravis. The use of negative-pressure ventilators is restricted in clinical practice, however, because they limit positioning and movement and they lack adaptability to large or small body torsos (chests).




POSITIVE PRESSURE VENTILATIONPositive pressure ventilators inflate the lungs by exerting positive pressure on the airway forcing the alveoli to expand during inspiration.

Expiration occurs passively.


ContDPositive-pressure ventilators require an artificial airway (Endotracheal or tracheostomy tube) and use positive pressure to force gas into a patient's lungs.

Inspiration can be triggered either by the patient or the machine.


Origins of mechanical ventilationNegative-pressure ventilators (iron lungs)Non-invasive ventilation first used in Boston Childrens Hospital in 1928Used extensively during polio outbreaks in 1940s 1950sPositive-pressure ventilatorsInvasive ventilation first used at Massachusetts General Hospital in 1955Now the modern standard of mechanical ventilation

The era of intensive care medicine began with positive-pressure ventilation

The iron lung created negative pressure in abdomen as well as the chest, decreasing cardiac output.Iron lung polio ward at Rancho Los Amigos Hospital in 1953.18Prof. Dr. RS Mehta, BPKIHS

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Mechanical Ventilators Classification19Prof. Dr. RS Mehta, BPKIHS

1. Control: How the ventilator knows how much flow to deliver? Volume Controlled (volume limited, volume targeted) and Pressure Variable Pressure Controlled (pressure limited, pressure targeted) and Volume Variable Dual Controlled (volume targeted, pressure limited)


2. Cyclinghow the ventilator switches from inspiration to expirationTime, flow, volume & pressure cycling mechanism.Time cycled: - is terminated to the expiratory phase once a predetermined inspiratory time elapses - it is used for neonates and in the operating room


Flow cycled: - When the flow reaches to a predetermined level, the ventilator cycles from inspiration into expiration irrespective of inspiratory time & VT. - Have pressure and flow sensors. Pressure-cycled: - Terminate into the expiratory phase when airway pressure reaches to a predetermined level, irrespective of VT, inspiratory time or inspiratory flow rate. -Pressure-cycled ventilators are generally most useful for short-term use only (transport).


Volume cycled: Terminate in inspiration when a preselected volume is delivered. Many adult ventilators are volume cycled but also have secondary limits on inspiratory pressure to guard against pulmonary barotrauma. If inspiratory pressure exceeds the pressure limit, the machine cycles into expiration even if the selected volume has not been delivered.


3. Triggering (What causes the ventilator to cycle to inspiration? )Time: The ventilator cycles at a set frequency as determined by the controlled rate.

Pressure: The ventilator senses the pt's inspiratory effort by way of a in the baseline pressure.

Flow: Modern ventilators deliver a constant flow around the circuit throughout the respiratory cycle. A deflection in this flow by patient inspiration, is monitored by the ventilator and it delivers a breath, requires less work by the patient than pressure triggering.


VENTILATION STRATEGIESAssisted spontaneous breathing: Continuous Positive Airway Pressure (CPAP)Positive End Expiratory Pressure (PEEP)

Supported spontaneous breathing: (Pressure or volume support in spontaneous breathing)Pressure Support Ventilation Volume Support Ventilation25Prof. Dr. RS Mehta, BPKIHS

ContDMixed respiratory support: Intermittent Mandatory Ventilation (IMV) Synchronized Intermittent Mandatory Ventilation (SIMV).

Controlled mechanical ventilation: Pressure Controlled VentilationVolume Controlled VentilationControlled VentilationHigh Frequency Ventilation26Prof. Dr. RS Mehta, BPKIHS

important ventilation modesControlled Mechanical Ventilation (CMV) - Pressure Controlled Ventilation (PCV) - Volume Controlled Ventilation (VCV) Intermittent Positive Pressure Ventilation (IPPV) Pressure Support Ventilation (PSV) Synchronized Intermittent Mandatory Ventilation (SIMV)Bi-level Positive Airway Pressure (BIPAP)Continuous positive airway pressure (CPAP) Inverse Ratio Ventilation (IRV)


Pressure-cycled modesPressure Support Ventilation (PSV)Pressure Control Ventilation (PCV)CPAPBiPAP

Volume-cycled modesAssist/Control VentilationIntermittent Mandatory Ventilation (IMV)Synchronous Intermittent Mandatory Ventilation (SIMV)


CPAPThe effect of CPAP is compared to inflating a balloon but not letting it completely deflate before inflating it again. The second inflation is easier to perform because resistance is decreased. A continuous level of elevated pressure is provided through the patient circuit to maintain adequate oxygenation, decrease the work of breathing.CPAP may be used invasively through an endotracheal tube or tracheostomy or non-invasively with a face mask or nasal prongs.29Prof. Dr. RS Mehta, BPKIHS

PEEP

PEEP is positive pressure that is applied by the ventilator at the end of expiration.

This mode does not deliver breaths but is used as an adjunct to CV and SIMV to improve oxygenation by opening collapsed alveoli at the end of expiration. 30Prof. Dr. RS Mehta, BPKIHS

CONTdComplications from the increased pressure can include decreased cardiac output, lung rupture, and increased intracranial pressure.

It is used to increase the surface area to prevent collapse of alveoli and to prevent atelectasis.

PEEP is functionally the same as CPAP, but refers to the use of an elevated pressure during the expiratory phase of the ventilatory cycle.


INTERMITTENT MANDATORY VENTILATION (IMV) A mode of mechanical ventilation in which the patient is allowed to breathe independently except during certain prescribed intervals, when a ventilator delivers a breath either under positive pressure or in a measured volume.32Prof. Dr. RS Mehta, BPKIHS

Synchronized Intermittent Mandatory Ventilation (SIMV)In this mode the ventilator provides a pre-set mechanical breath (pressure or volume limited) every specified number of seconds (determined by dividing the respiratory rate into 60 - thus a respiratory rate of 12 results in a 5 second cycle time). Within that cycle time the ventilator waits for the patient to initiate a breath using either a pressure or flow sensor. When the ventilator senses the first patient breathing attempt within the cycle, it delivers the preset ventilator breath. If the patient fails to initiate a breath, the ventilator delivers a mechanical breath at the end of the breath cycle.


CONTDSIMV is used as a primary mode of ventilation as well as a weaning mode. (During weaning, the preset rate is gradually reduced, allowing the patient to slowly regain breathing on their own.) The disadvantage of this mode is that it may increase the effort of breathing and cause respiratory muscle fatigue. When patient is breathing independently and adequately, ventilator does not support.Note: The ventilator initiates each breath in synchrony with the patient's breaths .


CONTROLLED VENTILATION: IPPV The ventilator initiates and controls both the volume delivered and the frequency of breaths. This mode is used for patients who are unable to initiate a breath. It is indicated in patients with apnea, drug overdose, spinal cord injuries, CNS dysfunction, flail chest, neuromuscular disease, and paralysis from drugs. If it is used with spontaneously breathing patients, they must be sedated and/or pharmacologically paralyzed so they don't breathe out of synchrony with the ventilator.35Prof. Dr. RS Mehta, BPKIHS

ASSIST CONTROL VENTILATIONThis mode is used for pts. who can initiate a breath but who have weakened respiratory muscles.In this mode, the ventilator provides a mechanical breath with either a pre-set tidal volume or peak pressure every time the pt. initiates a breath.If the pt. fail to initiate inspiration, the ventilator automatically goes into the back up mode and delivers the pre set rate and tidal volume until it senses an inspiratory effort.It is used in disease conditions like Myasthenia gravis, GB syndrome, post cardiac/respiratory arrest, pulmonary edema, ARDS, etc.


INVERSE RATIO VENTILATION (IRV)The normal inspiratory: expiratory ratio is 1:2, but this is reversed during IRV to 2:1 or greater (the maximum is 4:1).

This method is used for patients who are still hypoxic, even with the use of PEEP.


CONTDLonger inspiratory time increases the amount of air in the lungs at the end of expiration (the functional residual capacity) and improves oxygenation by re-expanding collapsed alveoli.

The shorter expiratory time prevents the alveoli from collapsing again.

This method requires sedation and therapeutic paralysis because it is very uncomfortable for the patient.


Time Cycled Ventilators Time-cycled ventilators terminate or control inspiration after a pre-set time. These ventilators are used in newborn & infants.


There are several ventilation modes, the most important are: SummaryControlled Mechanical Ventilation (CMV) - Pressure Controlled Ventilation (PCV) - Volume Controlled Ventilation (VCV) Intermittent Positive Pressure Ventilation (IPPV) Pressure Support Ventilation (PSV) Synchronized Intermittent Mandatory Ventilation (SIMV)Bi-level Positive Airway Pressure (BIPAP)Continuous positive airway pressure (CPAP) Inverse Ratio Ventilation (IRV)40Prof. Dr. RS Mehta, BPKIHS

SummaryPressure-cycled modesPressure Support Ventilation (PSV)Pressure Control Ventilation (PCV)CPAPBiPAPVolume-cycled modesAssist/ControlIntermittent Mandatory Ventilation (IMV)Synchronous Intermittent Mandatory Ventilation (SIMV)


Initiating Mechanical VentilationInitial ventilator settings:FiO2 1.0 initially but then reducePEEP 5 -7 cmH2O Tidal volume 7-10 ml/kgInspiratory pressure 20 cmH2O (15cmH2O above PEEP) Frequency 10 - 15 breaths per minutePressure support (ASB) 20 cmH2O (15cmH2O above PEEP) I:E Ratio 1:2 Flow trigger 2 l/minPressure trigger -1 to -3 cmH2OInspiratory flow 60 L/min **These settings should be titrated against the pt.'s clinical state and level of comfort.



Indications for intubationCriteriaClinical deteriorationTachypnea: RR >35Hypoxia: pO2 55mm HgMinute ventilation 7.25General approachesSIMV WeaningPressure Support Ventilation (PSV) WeaningSpontaneous breathing trials and use of T-pieceDemonstrated to be superior

No weaning parameter completely accurate when used aloneNumerical ParametersNormal RangeWeaning ThresholdP/F> 400> 200Tidal volume5 - 7 ml/kg5 ml/kgRespiratory rate14 - 18 breaths/min< 40 breaths/minVital capacity65 - 75 ml/kg10 ml/kgMinute volume5 - 7 L/min< 10 L/minGreater Predictive ValueNormal RangeWeaning ThresholdNIF (Negative Inspiratory Force)> - 90 cm H2O> - 25 cm H2ORSBI (Rapid Shallow Breathing Index) (RR/TV)< 50< 100

Marino P, The ICU Book (2/e). 1998.45Prof. Dr. RS Mehta, BPKIHS



Spontaneous Breathing TrialsSettingsPEEP = 5, PS = 0 5, FiO2 < 40%Breathe independently for 30 120 minABG obtained at end of SBTFailed SBT CriteriaRR > 35 for >5 minSaO2 30 secHR > 140Systolic BP > 180 or < 90mm HgSustained increased work of breathingCardiac dysrhythmiapH < 7.32

SBTs do not guarantee that airway is stable or pt can self-clear secretionsCauses of Failed SBTsTreatmentsAnxiety/AgitationBenzodiazepines or haldolInfectionDiagnosis and txElectrolyte abnormalities (K+, PO4-)CorrectionPulmonary edema, cardiac ischemiaDiuretics and nitratesDeconditioning, malnutritionAggressive nutritionNeuromuscular diseaseBronchopulmonary hygiene, early consideration of trachIncreased intra-abdominal pressureSemirecumbent positioning, NGTHypothyroidismThyroid replacementExcessive auto-PEEP (COPD, asthma)Bronchodilator therapy

Sena et al, ACS Surgery: Principles and Practice (2005).46Prof. Dr. RS Mehta, BPKIHS



Guidelines Suggesting the Need for Mechanical Ventilation Parameters that help us to guide to take the decision whether mechanical ventilation is needed or not? 1. Cl. Indices: Apnea with respiratory arrest RR >35 breaths per minute Paralysis of breathing muscle- GBS, MGhead trauma, coma - an absent gag or cough reflex. - Effect of anesthetic and muscle relaxant - Others: shock, CCF, sepsis


2. Mechanical indices Vital capacity 110 b/m, Sustained heart rate >20% higher or lower than baseline


CriteriaIncrease or decrease in blood pressure of > 20 mm HgSystolic blood pressure >180 mm Hg or 10 above baseline or > 30Sustained respiratory rate greater than 35 breaths/minuteTidal volume 5 ml/kg, Sustained minute ventilation

8. ventilator nursing care

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