Establishing the Need for Mechanical Ventilation Chapter 5

Ventilation: to help maintain normal respiratory balance, homeostasis Is the patient awake or asleep? –If asleep/unconscious are they able to be aroused? To what extent? What is the color, appearance and texture of the patient’s skin? –Cyanosis is evident where? - nailbeds and lips –Pale and diaphoretic Take the vital signs. –RR, HR, BP, body temperature, and SpO2

Dyspnea Patients appear alarmed –Eyes wide open –Forehead furrowed –Nostrils are flared May be sweating and flushed or ashen, pale and cyanotic May try to sit up, lean forward –Use accessory muscle of respiration –May complain about not getting enough air Paradoxical or abnormal movement of the thorax and abdomen Abnormal breath sounds Tachycardia arrhythmias and hypotension

Acute Respiratory Failure Respiratory activity is absent or is insufficient to maintain adequate oxygen uptake or carbon dioxide clearance Inability to maintain arterial oxygen carbon dioxide and pH at acceptable levels Two forms –Lung failure accompanied by hypoxemia –Pump failure accompanied by hypercapnia

Acute hypoxic respiratory failure Acute life threatening or vital organ threatening tissue hypoxia Result of: – severe V/Q mismatching –diffusion defects –right to left shunting –alveolar hypoventilation Acute hypercapnic respiratory failure Inability of the body to maintain normal PCO2 Three disorders that lead to pump failure –Central nervous system disorders –Neuromuscular disorders –Disorders that increase the work of breathing

Clinical Rounds 5-1 p.67 Stroke Victim A 58 year old male patient is admitted to the emergency department from his home after a suspected stroke (CVA). Vital signs reveal a HR 94, RR 16, normal temp, BP 165/95. The patients pupils respond slowly and unequally to light. Breath sounds are diminished in the bases. A sound similar to snoring is heard on inspiration. The patient is unconscious and unresponsive to painful stimuli. What is the most appropriate course of action at this time? Intubate to protect the airway Admit the patient to ICU Further evaluate VS, SpO2 monitoring, ABG values. Electrolytes, and neurological status Establishing mechanical ventilation may be necessary as the patient is unconscious and unresponsive

Clinical Rounds 5-2 p.68 Unexplained acute respiratory failure A stat ABG performed on a patient admitted through the ED reveals the following 7.15/83/34/28 on RA. The patient was found unconscious in a nearby park, no other history is available. What is the most appropriate course of action at this time? The problem may be drug related, try naloxone (Narcan) Intubate and begin ventilation Assess further with: –VS –SpO2 monitoring –ECG –breath sounds –ABG values –Electrolytes –blood alcohol levels –toxicology screening –Neurological status evaluation

Clinical Rounds 5-3 p.68 Ventilation in Neuromuscular Disorders CASE ONE A 68 year old female patient with a history of myasthenia gravis has been in the hospital for 12 days. She was admitted because her primary disease had worsened. The patient is unable to properly perform MIP and SVC maneuvers because she cannot seal her lips around the mouthpiece. Her attempts produced these values: MIP -34cmH2O; SVC 1.2L. What should the clinician recommend? In spite of the leak, parameters are still acceptable. Adapt of mouth seal to the system for measurements Continue to monitor MIP and VC q8 Request an evaluation of anticholinesterase therapy Keep the patient NPO and provide suctioning at the bedside until swallowing ability can be evaluated Monitor SpO2 and/or ABG values if symptoms become worse

Clinical Rounds 5-3 p.68 Ventilation in Neuromuscular Disorders CASE TWO A 26 year old male patient who is recovering from mycoplasmal pneumonia complains of tingling sensations and weakness in his hands and feet. He is admitted to the general floor for observation. Over several hours the patient becomes unable to move his legs. A respiratory therapist is called to assess him. What should the RT recommend at this time? The history and symptoms suggest Guillain-Barré syndrome The MIP and VC indicate muscle weakness and the ABG results show acute respiratory failure Provide ventilation if ARF is confirmed – consider possibilities of using NPPV, IPPV (oral, nasal, or tracheostomy)

Clinical Rounds 5-4 p.69 Asthma A 13 year old girl is seen in the ED for acute exacerbation of asthma. Continuous nebulizer therapy with a beta 2 adrenergic bronchodilator is administered. The patient has been given a high dose of corticosteroids and is receiving oxygen. Four hours after admission, she is alert and responsive. Her RR is 20. Course crackles and end- inspiratory wheezes are heard clearly throughout both lung fields. What recommendation for continuous respiratory care should be made for this patient? The patient appears to be improving Continue drug therapy reducing dosage and frequency Continue to monitor the patient

Physiological Measurements in Acute Respiratory Failure Ventilatory Mechanics MIP/NIF: maximum inspiratory pressure or negative inspiratory force; ability to generate enough volume to produce an effective cough –Normal -50 to -100 cm H2O –0-20cmH2O is inadequate VC: vital capacity; ability to take in a large volume of air to generate a strong cough –Normal 65-75ml/kg IBW (as high as 100ml/kg) –<15ml/kg IBW is inadequate PEFR: peak expiratory flow rate; indicator of airway patency –Normal L/min –75-100L/min is inadequate FEV1: forced expiratory volume in one second –Normal 80% VC ml/kg IBW –<10ml/kg IBW is inadequate RR: respiratory rate; elevated RR increases WOB –Normal –>35 inadequate for alveolar ventilation Ve: minute ventilation –Normal 5-6l/min –>10 l/min concerning

Failure of Ventilation Single best indicator of ventilation is PaCO2 Elevated PaCO2 suggested the Vds is increased in relation to Vt –Normal Vd/Vt ; >0.6 is a critical increase in dead space Alveolar Ventilation VA= Vt-Vd

Failure of Oxygenation Indicator of oxygenation status is PaO2 Normal PaO2 is mmHg on room air Total oxygen carrying capacity –CaO2=[(Hb x 1.34) x SaO2] + (PaO2 X 0.003) –Normal vol% Alveolar to arterial oxygen gradient –P A O2 = (P B – P H2O ) x FiO2 – PaCO2 x 1.25) –P(A-a)O2 –2-30 mmHg on RA; mmHg on 100% O2 Arterial to alveolar PO2 ratio PaO2/PAO2 –Normal PaO2/FiO2 –Normal

Standard Criteria for Initiating Mechanical Ventilation Apnea or absence of breathing Acute respiratory failure Impending respiratory failure Refractory hypoxic respiratory failure Ventilatory insufficiency and the need to protect the airway or manage secretions

Consider alternatives to invasive PPV High flow oxygen NPPV Intubation without ventilation Ethical considerations

Case Studies 1-5 p.75