Management of Patient Requiring Breathing Assistance

Management of Patient Requiring Breathing Assistance
Topic 2 (Q and A session) Dr. S. Nishan Silva (MBBS)

Q : Parts of the Respiratory System?

Q : Explain the different “Lung volumes”

Q : Indications for Ventilation?

Initiation of Mechanical Ventilation
Indications Indications for Ventilatory Support Acute Respiratory Failure Prophylactic Ventilatory Support Hyperventilation Therapy 6

Indications Acute Respiratory Failure (ARF) Respiratory activity is inadequate or is insufficient to maintain adequate oxygen uptake and carbon dioxide clearance. Inability of a patient to maintain arterial PaO2, PaCO2, and pH acceptable levels PaO2 < 70 on on O2 PaCO2 > 55 mm Hg and rising pH 7.25 and lower 7

Indications Acute Respiratory Failure (ARF) Hypoxic lung failure (Type I) Ventilation/perfusion mismatch Diffusion defect Right-to-left shunt Alveolar hypoventilation Decreased inspired oxygen Acute life-threatening or vital organ-threatening tissue hypoxia 8

Indications Acute Respiratory Failure (ARF) Clinical Presentation of Severe Hypoxemia Tachypnea Dyspnea Central cyanosis Tachycardia Hypertension Irritability, confusion Loss of consciousness Coma 9

Indications Acute Respiratory Failure (ARF) Acute Hypercapnic Respiratory Failure (Type II) CNS Disorders Reduced Drive To Breathe: depressant drugs, brain or brainstem lesions (stroke, trauma, tumors), hypothyroidism Increased Drive to Breathe: increased metabolic rate (CO2 production), metabolic acidosis, anxiety associated with dyspnea 10

Indications Acute Respiratory Failure (ARF) Acute Hypercapnic Respiratory Failure (Type II) Neuromuscular Disorders Paralytic Disorders: Myasthenia Gravis, Guillain-Barre´, ALS, poliomyelitis, etc. Paralytic Drugs: Curare, nerve gas, succinylcholine, insecticides Drugs that affect neuromuscular transmission; calcium channel blockers, long-term adenocorticosteroids, etc. Impaired Muscle Function: electrolyte imbalance, malnutrition, chronic pulmonary disease, etc. 11

Indications Acute Respiratory Failure (ARF) Acute Hypercapnic Respiratory Failure Increased Work of Breathing Pleural Occupying Lesions: pleural effusions, hemothorax, empyema, pneumothorax Chest Wall Deformities: flail chest, kyphoscoliosis, obesity Increased Airway Resistance: secretions, mucosal edema, bronchoconstriction, foreign body Lung Tissue Involvement: interstitial pulmonary fibrotic diseases 12

Indications Acute Respiratory Failure (ARF) Acute Hypercapnic Respiratory Failure Increased Work of Breathing (cont.) Lung Tissue Involvement: interstitial pulmonary fibrotic diseases, aspiration, ARDS, cardiogenic PE, drug induced PE Pulmonary Vascular Problems: pulmonary thromboembolism, pulmonary vascular damage Dynamic Hyperinflation (air trapping) Postoperative Pulmonary Complications 13

Indications Acute Respiratory Failure (ARF) Clinical Presentation of Hypercapnia Tachypnea Dyspnea Tachycardia Hypertension Headache (hallucinations when severe) Confusion (loss of consciousness, even coma when severe) Sweating 14

Prophylactic Ventilatory Support Clinical conditions in which there is a high risk of future respiratory failure Examples: Brain injury, heart muscle injury, major surgery, prolonged shock, smoke injury Ventilatory support is instituted to: Decrease the WOB Minimize O2 consumption and hypoxemia Reduce cardiopulmonary stress Control airway with sedation 15

Hyperventilation Therapy Ventilatory support is instituted to control and manipulate PaCO2 to lower than normal levels Acute head injury 16

Contraindications Untreated pneumothorax Relative Contraindications Patient’s informed consent Medical futility Reduction or termination of patient pain and suffering 20

Nomenclature

Nomenclature Airway Pressures Inspiratory Time or I:E ratio
Peak Inspiratory Pressure (PIP) Positive End Expiratory Pressure (PEEP) Pressure above PEEP (PAP or ΔP) Mean airway pressure (MAP) Continuous Positive Airway Pressure (CPAP) Inspiratory Time or I:E ratio Tidal Volume: amount of gas delivered with each breath These are some of the basic terms used with ventilators. CPAP is equivalent to PEEP except the term is usually used when referring to patients who are not intubated (i.e., on nasal CPAP).

Modes Control Modes: every breath is fully supported by the ventilator
in classic control modes, patients were unable to breathe except at the controlled set rate in newer control modes, machines may act in assist-control, with a minimum set rate and all triggered breaths above that rate also fully supported. In a control mode, the ventilator will guarantee that the patient receives the set tidal volume or PAP with every breath. The patient can breathe “above” the set rate but will receive full support regardless of their effort.

Modes IMV Modes: intermittent mandatory ventilation modes - breaths “above” set rate not supported SIMV: vent synchronizes IMV “breath” with patient’s effort Pressure Support: vent supplies pressure support but no set rate; pressure support can be fixed or variable (volume support, volume assured support, etc) IMV modes support breaths only at the set rate and interval. If the set rate is 10, then every six seconds the patient will receive a machine triggered breath (synchronized to their own effort if the mode is SIMV). In between those 10 breaths, the patient is free to breathe but those breaths are not supported. These breaths can be supported with pressure support (see more below). Lastly, the vent may not give any breaths at all but support the patient’s spontaneous efforts - this is pressure support/CPAP. Newer machines allow for the pressure support to be fixed (e.g., 10 mmHg) or variable (enough support so that the patient receives a tidal volume of 200cc).

Ventilator Settings Terminology (con’t)
PRVC: Pressure Regulated Volume Control PEEP: Positive End Expiratory Pressure CPAP: Continuous Positive Airway Pressure PSV: Pressure Support Ventilation NIPPV: Non-Invasive Positive Pressure Ventilation 25

Modes Whenever a breath is supported by the ventilator, regardless of the mode, the limit of the support is determined by a preset pressure OR volume. Volume Limited: preset tidal volume Pressure Limited: preset PIP or PAP As stated before, the limit of support can be volume or pressure.

Modes of Ventilation: The Basics
Assist-Control Ventilation Volume Control Assist-Control Ventilation Pressure Control Pressure Support Ventilation Synchronized Intermittent Mandatory Ventilation Volume Control Synchronized Intermittent Mandatory Ventilation Pressure Control

Control Mode 29

Assist Control Ventilation
A set tidal volume (if set to volume control) or a set pressure and time (if set to pressure control) is delivered at a minimum rate Additional ventilator breaths are given if triggered by the patient

A/C cont. Negative deflection, triggering assisted breath
Notice how the patient’s breath reflects the ventilator breath. Not for conscious patients! 32

Synchronized Intermittent Mandatory Ventilation
Breaths are given are given at a set minimal rate, however if the patient chooses to breath over the set rate no additional support is given One advantage of SIMV is that it allows patients to assume a portion of their ventilatory drive SIMV is usually associated with greater work of breathing than AC ventilation and therefore is less frequently used as the initial ventilator mode Like AC, SIMV can deliver set tidal volumes (volume control) or a set pressure and time (pressure control)

SIMV cont. Machine Breaths Spontaneous Breaths

PSV(pressure support ventilation)
Spontaneous inspiratory efforts trigger the ventilator to provide a variable flow of gas in order to attain a preset airway pressure. Can be used in adjunct with SIMV.

Pressure Support Ventilation
The patient controls the respiratory rate and exerts a major influence on the duration of inspiration, inspiratory flow rate and tidal volume The model 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.

Tidal Volume or Pressure setting
Maximum volume/pressure to achieve good ventilation and oxygenation without producing alveolar overdistention Max cc/kg? = 10 cc/kg Some clinical exceptions

Flow Rate The peak flow rate is the maximum flow delivered by the ventilator during inspiration. Peak flow rates of 60 L per minute may be sufficient, although higher rates are frequently necessary. An insufficient peak flow rate is characterized by dyspnea, spuriously low peak inspiratory pressures, and scalloping of the inspiratory pressure tracing

Inspiratory flow Varies with the Vt, I:E and RR
Normally about 60 l/min Can be majored to l/min

Inspiratory Time: Expiratory Time Relationship (I:E Ratio)
During spontaneous breathing, the normal I:E ratio is 1:2, indicating that for normal patients the exhalation time is about twice as long as inhalation time. If exhalation time is too short “breath stacking” occurs resulting in an increase in end-expiratory pressure also called auto-PEEP. Depending on the disease process, such as in ARDS, the I:E ratio can be changed to improve ventilation

I:E Ratio 1:2 Prolonged at 1:3, 1:4, … Inverse ratio

Fraction of Inspired Oxygen
The lowest possible fraction of inspired oxygen (FiO2) necessary to meet oxygenation goals should be used. This will decrease the likelihood that adverse consequences of supplemental oxygen will develop, such as absorption atelectasis, accentuation of hypercapnia, airway injury, and parenchymal injury

FIO2 The usual goal is to use the minimum Fio2 required to have a PaO2 > 60mmhg or a sat >90% Start at 100% Oxygen toxicity normally with Fio2 >40%

Inspiratory Trigger Normally set automatically 2 modes:
Airway pressure Flow triggering

Positive End-expiratory Pressure (PEEP)
What is PEEP? What is the goal of PEEP? Improve oxygenation Diminish the work of breathing Different potential effects

Positive End-Expiratory Pressure (PEEP)
Applied PEEP is generally added to mitigate end-expiratory alveolar collapse. A typical initial applied PEEP is 5 cmH2O. However, up to 20 cmH2O may be used in patients undergoing low tidal volume ventilation for acute respiratory distress syndrome (ARDS)

PEEP What are the secondary effects of PEEP? Barotrauma
Diminish cardiac output Regional hypoperfusion NaCl retention Augmentation of I.C.P.? Paradoxal hypoxemia

PEEP Contraindication: No absolute CI Barotrauma Airway trauma
Hemodynamic instability I.C.P.? Bronchospasm?

PEEP What PEEP do you want? Usually, 5-10 cmH2O

PEEP cont. Pressure above zero
PEEP is the amount of pressure remaining in the lung at the END of the expiratory phase.

Continuous Positive Airway Pressure (CPAP):
This IS a mode and simply means that a pre-set pressure is present in the circuit and lungs throughout both the inspiratory and expiratory phases of the breath. CPAP serves to keep alveoli from collapsing, resulting in better oxygenation and less WOB. The CPAP mode is very commonly used as a mode to evaluate the patients readiness for extubation. Please note that the patient has to be spontaneously breathing to use this mode! Often used in conjunction with weaning the patient from the ventilator. 52

Advantages of Each Mode
Assist Control Ventilation (AC) Reduced work of breathing compared to spontaneous breathing AC Volume Ventilation Guarantees delivery of set tidal volume AC Pressure Control Ventilation Allows limitation of peak inspiratory pressures Pressure Support Ventilation (PSV) Patient comfort, improved patient ventilator interaction Synchronized Intermittent Mandatory Ventilation (SIMV) Less interference with normal cardiovascular function

Disadvantages of Each Mode
Assist Control Ventilation (AC) Potential adverse hemodynamic effects, may lead to inappropriate hyperventilation AC Volume Ventilation May lead to excessive inspiratory pressures AC Pressure Control Ventilation Potential hyper- or hypoventilation with lung resistance/compliance changes Pressure Support Ventilation (PSV) Apnea alarm is only back-up, variable patient tolerance Synchronized Intermittent Mandatory Ventilation (SIMV) Increased work of breathing compared to AC

Intubation Miller Blade is straight – directly lifts the epiglottis to allow visualization of the vocal cords. MacIntosh – blade is curved; inserted into the vallecula to indirectly lift the epiglottis. Infants are always intubated with the Miller die to the floppy airway. 55

Intubation Procedure Check and Assemble Equipment:
Oxygen flowmeter and O2 tubing Suction apparatus and tubing Suction catheter or yankauer Ambu bag and mask Laryngoscope with assorted blades 3 sizes of ET tubes Stylet Stethoscope Tape Syringe Magill forceps Towels for positioning 56

Position your patient into the sniffing position
Intubation Procedure Position your patient into the sniffing position 57

Do not allow more than 30 seconds to any intubation attempt.
Intubation Procedure Preoxygenate with 100% oxygen to provide apneic or distressed patient with reserve while attempting to intubate. Do not allow more than 30 seconds to any intubation attempt. If intubation is unsuccessful, ventilate with 100% oxygen for 3-5 minutes before a reattempt. 58

Intubation Procedure Insert Laryngoscope
Laryngoscope is always held in the left hand and is used to displace the tongue to the left so that the epiglottis may be seen. 59

Intubation Procedure Laryngoscope is always held in the left hand and is used to displace the tongue to the left so that the epiglottis may be seen. 60

Intubation Procedure After displacing the epiglottis insert the ETT.
The depth of the tube for a male patient on average is cm at teeth The depth of the tube on average for a female patient is at teeth. An easy trick to use is tube size X 3 – works almost all the time. 61

Intubation Procedure Confirm tube position:
By auscultation of the chest Bilateral chest rise Tube location at teeth CO2 detector – (esophageal detection device) You must rule out an esophageal intubation with capnography or by BS. Always listen over the epigastrium after listening to the chest. These are bedside procedures that must be done immediately after intubation prior to an XRAY. 62

Intubation Procedure Stabilize the ETT
Can be done with tape or a commercially available ETT stabilizer. Always tape above the ETT and never to the chin. 63

Q: Describe suction procedure for ventilated patients.

TROUBLESHOOTING

Troubleshooting Look at the patient !! Listen to the patient !!
Is it working ? Look at the patient !! Listen to the patient !! Pulse Ox, ABG, EtCO2 Chest X ray Look at the vent (PIP; expired TV; alarms) Nothing ever replaces the clinical exam. Look at the patient and listen to judge for yourself how the patient is doing. Does the patient appear pink and well perfused? Has the respiratory rate of the patient decreased? Is the chest moving? Are breath sounds present and equal? Now look at the pulse oximeter; send an ABG and maybe check an end-tidal CO2. These tests are used more often than not to confirm your clinical impression. They certainly have a role when the clinical exam may be indeterminate and they can be more sensitive in detecting small changes. A chest x-ray can be used to confirm that the tube is in good position and can be used to follow the progression of the patient’s disease process. Chest x rays may also be helpful if there are acute changes, such as a pneumothorax or right upper lobe collapse. The ventilator can also be a source of information. Is it delivering what it is set for? Has the PIP increased suddenly? Has the expired tidal volume dropped? A significant difference between the inhaled tidal volume and exhaled tidal volume may be indicative of a leak within the circuit.

TROUBLESHOOTING Attempt to fix the problem Call your doctor
Anxious Patient Can be due to a malfunction of the ventilator Patient may need to be suctioned Frequently the patient needs medication for anxiety or sedation to help them relax Attempt to fix the problem Call your doctor

Low Pressure Alarm Usually due to a leak in the circuit.
Attempt to quickly find the problem Bag the patient and call your doctor

High Pressure Alarm Usually caused by:
A blockage in the circuit (water condensation) Patient biting his ETT Mucus plug in the ETT You can attempt to quickly fix the problem Bag the patient and call for your doctor

Low Minute Volume Alarm
Usually caused by: Apnea of your patient (CPAP) Disconnection of the patient from the ventilator You can attempt to quickly fix the problem Bag the patient and call for your doctor

Accidental Extubation
Role of the Nurse: Ensure the Ambu bag is attached to the oxygen flowmeter and it is on! Attach the face mask to the Ambu bag and after ensuring a good seal on the patient’s face; supply the patient with ventilation. Bag the patient and call for your doctor

OTHER Call for your doctor NEVER hit the silence button!
Anytime you have concerns, alarms, ventilator changes or any other problem with your ventilated patient. Call for your doctor NEVER hit the silence button!

Trouble Shooting

ABG Goal: Keep patient’s acid/base balance within normal range:
pH – 7.45 PCO mmHg PO mmHg Any variance in these values will require a change made to this patient’s ventilator. 74

Complications Ventilator Induced Lung Injury Oxygen toxicity
Barotrauma / Volutrauma Peak Pressure Plateau Pressure Shear Injury (tidal volume) PEEP Positive pressure ventilation can be injurious to the lungs, which were designed as a negative pressure circuit. What exactly qualifies as a dangerous pressure or even what is the best pressure to follow is not exactly known. Recently, a plateau pressure of >35 mmH2O has been proposed as a limit. Plateau pressures are measured during an inspiratory “pause” - the lungs are kept inflated but there is no gas flow occurring. Also, recent studies have demonstrated that cyclic overdistention/collapse of an alveolus can contribute to lung injury by causing the release of inflammatory mediators. You want to keep the alveolus on the steep part of the compliance curve - not ride between the bottom plateau and the upper plateau (refer to slide #22). See below for the side effects of PEEP. What constitutes a safe FiO2 is also not exactly known is an acceptable limit to some, albeit arbitrary. Oxygen toxicity results in the production of free radicals with resulting cell damage and death.

Complications Cardiovascular Complications
Impaired venous return to RH Bowing of the Interventricular Septum Decreased left sided afterload (good) Altered right sided afterload Sum Effect…..decreased cardiac output (usually, not always and often we don’t even notice) Increasing the intrathoracic pressure, as mechanical ventilation does, has several effects on the heart. First and foremost, it decreases venous return to the right side of the heart and subsequently to the left side of the heart. Patients may need a higher CVP to maintain cardiac output. Positive pressure also causes the interventricular septum to bow to the left, which decreases the filling capacity of the left ventricle and thus its output. Positive pressure does decrease the afterload the LV faces. This can be of use in patients with left heart failure. The effects on right sided afterload depend on the lung volumes. If positive pressure increases the total lung volume to FRC then pulmonary vascular resistance will decrease (as hypoxic vasoconstriction is relieved) and right sided afterload will decrease. If positive pressure increases lung volumes beyond FRC, then overdistended alveoli will compress blood vessels, increasing PVR and right sided afterload. More often than not, a patient will have decreased cardiac output when on positive pressure. This can often be ameliorated by fluid administration. The degree of cardiac compromise may often limit the amount of PEEP a patient can tolerate and hence what you are willing to use.

Complications Other Complications Ventilator Associated Pneumonia
Sinusitis Sedation Risks from associated devices (CVLs, A-lines) Unplanned Extubation Other complications from mechanical ventilation are as listed. [Should we discuss post-extubation stridor and laryngeal edema or leave that for the folks doing the airway talk?]

Extubation Weaning Is the cause of respiratory failure gone or getting better ? Is the patient well oxygenated and ventilated ? Can the heart tolerate the increased work of breathing ? In truth, you are always weaning a patient in the sense that you are always trying to minimize the ventilator settings. “True” weaning implies a different expectation - that the patient is improving and will soon not need mechanical ventilation. This usually happens when the disease process is improving or resolved and the patient has acceptable parameters. It is important to assess the ability of the heart to handle the increased demands that extubation may place upon it (e.g., pneumonia/ARDS has resolved but significant septic shock with cardiovascular collapse is present).

Extubation Weaning (cont.)
decrease the PEEP (4-5) decrease the rate decrease the PIP (as needed) What you want to do is decrease what the vent does and see if the patient can make up the difference…. Weaning is really the transfer of demands from the ventilator to the patient. By decreasing the rate, the FiO2 and the PEEP, you are asking the patient to do more. The rate at these parameters are decreased will often depend on the acuity of the disease process. The patient who was intubated because of sedation secondary to a drug overdose may wean rapidly when they are awake as compared to the child recovering from ARDS who may take weeks to completely wean from mechanical ventilatory support. The rate can be decreased in increments of 2-5 breaths/minute (or more) as dictated by the clinical situation. An arterial blood gas or end tidal CO2 monitor can be used to assess the PaCO2 after these changes. PEEP is generally lowered in increments of 1-2 mmH2O per change. As changes in oxygenation or ventilation may not be immediately apparent after a decrease in PEEP, these changes are not made more often than every 6-8 hours. [fair statement?]

Extubation Extubation Control of airway reflexes
Patent upper airway (air leak around tube?) Minimal oxygen requirement Minimal rate Minimize pressure support (0-10) “Awake ” patient When is a patient ready to be extubated? First, they must be able to protect their airway. They should have an acceptable SaO2 on an FiO2 of no more than They should be breathing at a comfortable rate with a set ventilator rate of 5-8. Patients may be trialed on just pressure support/CPAP to make sure they are generating an adequate spontaneous minute ventilation. The amount of pressure support should be just enough to compensate for the added work of breathing imposed by the vent and ETT. The PEEP should be at 5 mmH2O. If these are the circumstances, then the patient is ready for an attempt at extubation and their time on mechanical ventilation (and this presentation) has come to an end.

Mechanical Ventilators
Different Types of Ventilators Available: Will depend on you place of employment 81

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High Frequency Mechanical Ventilator
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Management of Patient Requiring Breathing Assistance

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