Initiating ventilatory support
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Initiating Ventilatory Support. 215a. Objectives. List the indications for ventilatory support List the factors analyzed to determine initial ventilator modes and settings Define the current modes of ventilation, listing The advantages and disadvantages of each Basic intro to settings.

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Initiating ventilatory support

Initiating Ventilatory Support

215a


Objectives

Objectives

  • List the indications for ventilatory support

  • List the factors analyzed to determine initial ventilator modes and settings

  • Define the current modes of ventilation, listing The advantages and disadvantages of each

  • Basic intro to settings


First a review of ventilation formulas

First a Review of Ventilation formulas…

  • http://www.youtube.com/watch?v=mF4OvuzlfXc&feature=related

  • Ve, VA, Compliance


Indications for ventilatory support

Indications for Ventilatory Support

  • Respiratory failure (type I or II)

    • Exacerbation of COPD

    • Neuromuscular disease

    • Coma


Initiating ventilatory support

The volume of carbon dioxide eliminated per minute (which in a steady state is equal to that produced by the body (V'CO2) is dependent on the concentration of carbon dioxide in alveolar gas and οnV'A.

V'CO2=V'A× alveolar CO2 concentration or alveolar CO2 concentration=V'CO2/V'A.


Hypoxemia

Hypoxemia

The condition of hypoxemia refers to the low partial pressure of oxygen in the arterial blood. Hypoxemia is often confused with either anoxia, asphyxia, hypoxia or anemia. Although, these are in some way related to reduction in the levels of oxygen in the body, these are distinct medical conditions.

  • Anoxiais the absence of oxygen supply in the body. This implies extremely low levels of oxygen in the body.

  • Asphyxiais the absence of oxygen along with the accumulation of carbon dioxide.

  • Hypoxiais the deficiency of oxygen in some specific part of the body.

  • Anemia refers to a condition when oxygen content in the arterial blood is low and the partial pressures in the arterial blood are high.

  • Hypoxemiarefers to refers to a condition when oxygen content in the arterial blood is low as also the partial pressures in the arterial blood.

  • http://www.youtube.com/watch?v=f8zIVc9yTMg


Arterial oxygen content cao 2

Arterial Oxygen Content (CaO2)

  • The arterial oxygen content can be given by the following equation:

    Arterial Oxygen Content = (Hgb x 1.34 x SaO2) + (0.0031 x PaO2) where,

    Hgb is the hemoglobinSaO2 is the percentage of hemoglobin saturated with oxygen PaO2 is the partial pressure of arterial oxygen


Clinical manifestations of type i respiratory failure

Clinical Manifestations of Type I Respiratory Failure

  • Clinical signs of hypoxemia

    • Dyspnea

    • Tachycardia

    • Tachypnea

  • Use of accessory muscles of ventilation

  • Nasal flaring

  • Cyanosis – peripheral and central

  • Central nervous system dysfunction – irritability, confusion, coma


Symptoms of hypoxemia

Symptoms of Hypoxemia

(The symptoms of hypoxemia depend on the severity i.e. the amount by which the partial pressure has reduced.)

  • Symptoms of mild hypoxemia:

    • Restlessness

    • Anxiety

    • Disorientation, confusion, lassitude and listlessness

    • Headaches


Symptoms of hypoxemia1

Symptoms of Hypoxemia

  • Symptoms of acute hypoxemia:

    • Cyanosis (Skin appearing bluish due to insufficient oxygen)

    • Cheyne-Stokes respiration (irregular pattern of breathing)

    • Increased blood pressure

    • Apnea (temporary cessation of breathing)

    • Tachycardia (increased rate of heartbeats, more than 100 per min)

    • Hypotension (abnormally low blood pressure, below 100 diastolic and 40 systolic. Here, as an effect of an initial increase in cardiac output and rapid decrease later.)

    • Ventricular fibrillation (irregular and uncoordinated contractions of the ventricles)

    • Asystole (severe form of cardiac arrest, heart stops beating)

    • Polycythemia (abnormal increase in RBCs. The bone marrow may be stimulated to produce excessive RBCs in case of patients suffering from chronic hypoxemia)

    • Coma


Clinical manifestations of acute ventilatory failure

Clinical Manifestations of Acute Ventilatory Failure


Clinical manifestations of type i respiratory failure1

Clinical Manifestations of Type I Respiratory Failure

  • Auscultation

    • Wheezing indicates bronchospasm (asthma?)

    • Diminished (COPD?)

    • Unilateral wheezing – endobronchial lesion, FBAO

    • Unilaterally diminished or absent – atelectasis, infection, effusion


Clinical manifestations of type i respiratory failure2

Clinical Manifestations of Type I Respiratory Failure

  • Radiologic Findings

    • “Black” radiograph

      • Hyperinflated lungs (COPD) – V/Q mismatch

    • “White” radiograph

      • Occlusion of alveoli – shunt


Clinical manifestations of type ii respiratory failure

Clinical Manifestations of Type II Respiratory Failure

  • Decreased respiratory drive

    • Bradypnea leading to apnea

    • Clinical signs of decrease in respiratory drive

    • Respiratory rate < 12 bpm

    • Altered state of consciousness (increase CO2, amonia, blood sugar, ICB…)

    • Rapid, shallow breathing pattern (obesity, neuromuscular)

    • Evidence of trauma (brain injury)

    • Fatigue (hypothyroidism, sleep apnea)

    • Radiologic findings – atelectasis secondary to hypoventilation


Clinical manifestations of type ii respiratory failure1

Clinical Manifestations of Type II Respiratory Failure

  • Neurological disease

    • Drooling, dysarthria (unable to speak), weak cough (ALS)

    • Unable to swallow (Dysphagia)

    • Muscle wasting

    • Diaphragmatic weakness

    • Supine paradoxical breathing (ALS)

    • Lower extremity weakness, progressing superiorly (Guillain-Barre)

    • Ocular muscle weakness (myasthenia gravis)


Clinical manifestations of type ii respiratory failure2

Clinical Manifestations of Type II Respiratory Failure

  • Increased work of breathing

    • Increasingly rapid, but shallow breathing (exacerbation of COPD)

    • Diminished breath sounds

    • Irritability, confusion


Chronic respiratory failure

Chronic Respiratory Failure

  • Development of respiratory failure in patients with chronic respiratory conditions over an extended period of time, as much as years

    • Allows compensatory mechanisms to adapt to the disease state

    • Most commonly Type II failure with compensatory metabolic alkalosis (COPD)

    • Compensation for Type I is polycythemia (Fibrosis/COPD)

    • May be complicated by superimposed acute respiratory failure


Chronic respiratory failure with superimposed acute rf

Chronic Respiratory Failure With Superimposed Acute RF

  • Precipitating factors

    • Bacterial or viral infections

    • Congestive heart failure http://www.youtube.com/watch?v=JJAMYHAwCMs&feature=related

    • Pulmonary embolism

    • Chest wall dysfunction

    • Non-compliance with medical orders

    • “Normal” blood gases for these patients may be outside normal limits


Chronic respiratory failure with superimposed acute rf1

Chronic Respiratory Failure With Superimposed Acute RF

  • Goals of therapy

    • Normalization of pH

    • Elevation of SaO2

    • Improvement of airflow

    • Treatment of infections

    • Maintain fluid status


Indications for ventilatory support1

Indications for Ventilatory Support

  • Acute respiratory failure

    • Post-Operative respiratory failure (over sedation, complications)

    • Sepsis (sudden increase in VO2 and CO2 production)

    • Cardiac failure (MI, CHF…)


Indications for ventilatory support2

Indications for Ventilatory Support

  • Acute respiratory failure

    • ARDS (from PN, Sepsis…)

    • Trauma (blood loss, head trauma…)

    • Pneumonia (causing plugs…)


Indications for ventilatory support3

Indications for Ventilatory Support

  • Apnea (sedation, drug OD…)

  • Impending respiratory failure

  • Inability to oxygenate


Clinical manifestations of acute ventilatory failure1

Clinical Manifestations of Acute Ventilatory Failure

Rapid, shallow respiratory pattern frequently have pleural space disease (pleural effusion, hemothorax, pneumothorax).


Clinical manifestations of acute ventilatory failure2

Clinical Manifestations of Acute Ventilatory Failure

  • Patients with end-expiratory effort and wheezes on chest auscultation frequently have small airway obstructive disease (asthma).

  • Patients with deep, labored chest movements frequently have pulmonary parenchymal disease (pulmonary edema, pulmonary contusions, space-occupying masses).

  • Patients with obvious stridor, minimal air movement at the nares or mouth, and marked inspiratory effort typically have upper airway obstruction (laryngeal edema or paralysis, foreign body aspiration).

  • These patterns are hardly exclusive: Often patients have multiple problems, and some patients may have serious underlying respiratory problems and yet clinically appear normal.


Initiating ventilatory support

What nonrespiratory conditions can mimic acute respiratory distress?

Numerous disorders cause tachypnea, orthopnea, and other signs referable to the respiratory system in the absence of true respiratory disease. These disorders can confuse the clinician. Disorders such as hyperthermia, shock, metabolic acidosis and alkalosis, hyperthyroidism, fear or anxiety, pericardial tamponade, anemia, abdominal organ enlargement or ascites, and abnormalities with central control of respiration from drugs and metabolic or organic central nervous system disease are all causes of signs that may mimic true respiratory distress.


Clinical manifestations of acute ventilatory failure3

Clinical Manifestations of Acute Ventilatory Failure

  • Cardiovascular symptoms

    • Tachycardia; when severe bradycardia

    • Hypertension; when severe, hypotension

    • Vasodilation


Clinical manifestations of acute ventilatory failure4

Clinical Manifestations of Acute Ventilatory Failure

  • Neurologic symptoms

    • Headache

    • Drowsiness; when severe non-responsiveness

    • Convulsions

    • Biots/Cheyne stokes breathing


Clinical manifestations of acute ventilatory failure5

Clinical Manifestations of Acute Ventilatory Failure

  • Other signs

    • Sweating

    • Redness of the skin


Goals of ventilatory support

Goals of Ventilatory Support

  • Maintenance of adequate alveolar ventilation and oxygen delivery

  • Restore acid-base balance


Goals of ventilatory support1

Goals of Ventilatory Support

  • Reduce the work of breathing

  • Reduce myocardial work secondary to hypoxemia And increased work of breathing


Considerations when initiating ventilatory support

Considerations When Initiating Ventilatory Support

  • Type of airway: endotracheal tube vs. tracheostomy tube

  • Pressure-controlled vs. volume-controlled ventilation- depends on if patient has pre-existing congestion, loss of compliance, known lung problems

  • http://www.youtube.com/watch?v=4O4vGPqM2RM


Pressure controlled ventilation

Pressure-Controlled Ventilation

  • Pressure support ventilation (PSV)

    • Designed to augment spontaneous ventilation (increases Spontaneous tidal volume)

    • Patient-triggered, pressure- limited, flow-cycled ventilation

    • Used to overcome RAW imposed by ETT

    • May be stand-alone mode or used with SIMV/CPAP

    • http://www.youtube.com/watch?v=oLZ0fcJ9Rhw&NR=1


Pressure controlled ventilation1

Pressure-Controlled Ventilation

  • Pressure control ventilation (PCV)

    • Delivery of mandatory support breaths at a set inspiratory pressure (pressure limited/time cycled)

    • May be used in assist-control mode or with SIMV

    • Set pressure limit (PIP) and Inspiratory time

    • Volume and flow vary


Pressure controlled ventilation2

Pressure-Controlled Ventilation

  • Pressure control ventilation (PCV)

    • Useful in limiting airway pressure and providing a decreasing flow, which may improve gas distribution and synchrony

    • Can be set in any patient, however most often used for patients with low compliant lungs, especially if high PEEP levels will be used


Volume controlled ventilation

Volume-Controlled Ventilation

  • Used primarily to maintain constant tidal volume

  • Useful when lung mechanics are changing due to pathophysiology

  • Set Tidal volume based on patient’s IBW in a range of 8-12 ml/kg and flow rate

  • IBW= men 106 + 6 lbs for every inch over 60 inches

  • IBW=woman 105 + 5 lbs for ever inch over 60 inches

  • For restrictive disease 5-7 ml/kg


Volume controlled ventilation1

Volume-Controlled Ventilation

  • Volume control is volume limited and flow cycled

  • Can be set in AC or SIMV modes

  • Direct control over Ve

  • I-time and pressure vary depending on patients lung compliance


Pressure regulated volume control prvc ventilation

Pressure-Regulated Volume Control (PRVC) Ventilation

  • Offers pressure-controlled ventilation while guaranteeing a volume

  • Pressure and flow fluctuate to maintain a constant minimum TV

  • May not work well with restrictive lungs


Non invasive nppv vs invasive ppv

Non-Invasive (NPPV) vs. Invasive PPV

  • Advantages of NPPV

    • Avoidance of intubation

    • Preservation of natural airway defenses

    • Patient comfort


Non invasive nppv vs invasive ppv1

Non-Invasive (NPPV) vs. Invasive PPV

  • Advantages of NPPV

    • Maintenance of speech and swallowing

    • Intermittent use


Non invasive nppv vs invasive ppv2

Non-Invasive (NPPV) vs. Invasive PPV

  • Disadvantages of NPPV

    • Patient cooperation essential

    • Limited access to airway during ventilation

    • Discomfort from mask


Non invasive nppv vs invasive ppv3

Non-Invasive (NPPV) vs. Invasive PPV

  • Disadvantages of NPPV

    • Ulceration, face sores, eye irritation, rhinitis, dry nose

    • Stomach pain from gastric inflation

    • Leak from improper fit

    • Aspiration risk


Non invasive nppv vs invasive ppv4

Non-Invasive (NPPV) vs. Invasive PPV

  • Disadvantages of NPPV

    • Transient hypoxemia from mask disconnection

    • BiPAP limited to maximum of 30 cmH2O

    • Time consuming procedure

    • Drying of secretions/plugs


Partial vs full ventilatory support

Partial vs. Full Ventilatory Support

  • Partial ventilatory support

    • Use of ventilator settings requiring patient to provide portion of the ventilation


Modes of partial ventilation

Modes of Partial Ventilation

  • Synchronized intermittent mandatory ventilation (SIMV)

  • Pressure support ventilation (PSV)

  • Volume support ventilation (VSV), PSV will fluctuate depending on set minimum VT


Modes of partial ventilation1

Modes of Partial Ventilation

  • Adaptive pressure ventilation (APV)

  • Adaptive support ventilation (ASV)

  • Mandatory minute volume ventilation (MMV)

  • WE WILL TALK ABOUT THE ADAPTIVE MODES IN A SEPARATE LECTURE


Full ventilatory support

Full Ventilatory Support

  • Ventilator provides the full minute ventilation; no patient contribution

  • Assist-control mode


Initial ventilator settings

Initial Ventilator Settings

  • Choice of mode (AC, IMV/SIMV, PCV, PRVC, APRV)

  • Tidal volume (VT) – 8 to 12 ml/kg IBW

  • Rate (f) – typically backup rate of 8-12 breaths /min


Initial ventilator settings1

Initial Ventilator Settings

  • Trigger sensitivity (either flow or pressure)

    • Typically -0.5 to -2.o cmH2O to minimize effort

    • May need to be adjusted to avoid auto-cycling on some ventilators

    • Applies only to patient triggered breaths


Initial ventilator settings2

Initial Ventilator Settings

  • Trigger sensitivity

    • Flow triggering may have slightly less work than pressure triggering


Initial ventilator settings3

Initial Ventilator Settings

  • Inspiratory flow

    • 60 to 80 L/min. to achieve an inspiratory time of 1 second and an I:E ratio of 1:2 or better

    • May require higher flows in patients with COPD to lengthen expiratory time, allowing improved gas exchange


Initial ventilator settings4

Initial Ventilator Settings

  • Flow waveform

    • Decelerating or decreasing flow waveform generally delivered in pressure ventilation

    • Decelerating waveforms generally decrease peak inspiratory pressure, but increase mean airway pressure


Decelerating set in vc automatic in pc

Decelerating – set in VC, automatic in PC


Constant flow vc only

Constant Flow – VC only

Increases MAP, decreased I-time


Initial ventilator settings5

Initial Ventilator Settings

  • Oxygen percentage (FIO2)

    • If little is known concerning patient, begin with FIO2 of 1.0, decreasing to 0.4 to 0.5 as quickly as possible

    • Patients with known blood gas results should be given FIO2 consistent with the known data


Initial ventilator settings6

Initial Ventilator Settings

  • Positive end-expiratory pressure (PEEP)

    • PEEP of 5 cmH2O is advocated by some as “physiologic PEEP”

    • Should be adjusted as necessary to allow FIO2 to be reduced to 0.4 as quickly as possible


Initial ventilator settings7

Initial Ventilator Settings

  • Pressure limit

    • Start at 50 cmH2O

    • Adjust to 10 to 20 cmH2O above peak pressure when patient is stable


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