Non-Invasive Ventilation

Readings Pages 760 - 763 Noninvasive Ventilation, Respiratory Care Equipment, Mosby. Pages 766 - 770 Respironics BiPAP Vision, Respiratory Care Equipment, Mosby. Pages 332 - 339 Essentials of Mechanical Ventilation, Hess. Two articles on Web CT named: Early Noninvasive Ventilation Averts Extubation & Supplemental. NIV almost equals Bipap equals Bilevel, but not quite. How we ventilate is part of Vision module. Are we still using Visions? 4/20/2019

Non-Invasive Ventilation NPPV has been reported in the management of acute respiratory failure Pneumonia COPD exacerbation CHF Asthma (very little data to support) Obstructive sleep apnea Other... Change for next year. Other reasons-failure post-extubation. Big uses – COPD and CHF, early intervention in ERs shown to decrease chance of intubation, decrease days in hospital, etc. 4/20/2019

Nosocomial Infection Major source of morbidity and mortality in critically ill patients Use of invasive devices increases risk for developing nosocomial infection Endotracheal tubes leading factor Secondary factors include intravenous catheters, urinary catheters One of the big reasons for use of Bipap. 4/20/2019

Reduction of Nosocomial Pneumonia NPPV maintains natural barriers provided by glottis, upper respiratory tract May decrease duration of mechanical ventilation, need for sedation, and length of stay (LOS) in ICU Reduces mortality in select groups of patients with COPD exacerbation Upper a/w acts as a filter – Limits lower a/w infection, gives ability to swallow, gag, and cough. 4/20/2019

NPPV and Hospital Acquired Pneumonia Matched case control study 50 pts acute COPD or cardiogenic pulmonary edema received NPPV 50 matched controls received invasive ventilation Why does UTI increase in ventilated population? 4/20/2019 Girou et al, JAMA 2000; 248: 2361-2367

Also look at oxygenation. Might be more important then CO2 Also look at oxygenation. Might be more important then CO2. CO2 is WOB, O2 a matter of atelectasis, diffusion gradients. Never like looking at fixed parameters. 4/20/2019

Clinical Application of NPPV Step one Is the patient sick enough? Step two Is the patient too sick? Respiratory arrest Medically unstable Unable to protect airway Uncooperative What parameters need to be looked at for the patient to be sick enough for Bipap? The main one is WOB above all else. Clinical examination! Then RR, PaO2, and PaCO2 The big, big one is that the patient must be able to protect upper a/w, so LOC/GCS is very important! If the patient is not awake, don’t put them on it! Only exception being for palliative care reasons. 4/20/2019

Patient Selection for NPPV Respiratory distress with dyspnea, use of accessory muscles, abdominal paradox pH < 7.35 with PaCO2 > 45 mmHg (acute hypercapnia) Respiratory rate > 25/min (tachypnea) Acute hypoxemic respiratory failure Numbers not as important as presentation. I’m not a number guy; some of your Dr’s will be. 4/20/2019

Exclusions for NPPV Airway protection Unable to fit mask Uncooperative patient – Anxiety, unable to cooperate Uncontrolled dysrhythmias and/or evidence of MI Upper airway obstruction or facial trauma, burns, facial surgery Placing a mask over your face increases anxiety; it takes a while before it is considered more comfortable; it must greatly decrease WOB before pt likes it. They will be more uncooperative with it on; it may lead to panic. Good coaching is essential. So why would you be unable to fit mask? Beard, alternate facial structure, no dentures in. Should you keep dentures in? 4/20/2019

Exclusions cont. Apnea or need for rapid intubation Unstable hemodynamics – BP< 90mmHg High aspiration risk, unable to protect airway, copious secretions Anatomic lesion of upper airway Relative contraindications Asthma Pneumonia Don’t bipap for secretion-related issues – Dries up secretions, pushes them down and prevents clearing. May improve short-term oxygenation, but pt usually deteriorates and is much more difficult to treat when they get intubated. 4/20/2019

Evidence for Effectiveness Initial response may predict success or failure Those who failed were intubated within first 12 hours Success associated with a rapid decrease in PaCO2 4/20/2019

COPD – Evidence 275 patients screened; 75 enrolled NPPV Control Intubation Rate 26% 74% Complications 16% 48% Hospital Stay 23 days 35 days Mortality 9% 29% 4/20/2019 Brochard et al, N Engl J Med 1995; 333: 817-822

Candidates for NPPV Sick, but not too sick COPD, CHF, and perhaps others Short-term requirement for ventilatory support These are the patients that it is most successful on, mainly. 4/20/2019

Weaning COPD Patients After 48 hrs, patients randomized to PSV by ETT or extubated to NPPV by mask NPPV group had reduced weaning time, fewer ICU days, lower nosocomial pneumonia rate, improved 60-day survival Nava et al, Ann Intern Med 1998; 128: 721-728 4/20/2019

Nasal Masks 4/20/2019

Oronasal (Full-Face) Masks 4/20/2019

Nasal Pillows Frequently now used in home CPAP machines. 4/20/2019

Common Problems with Interface Headgear too tight (Should be able to easily fit 2 fingers between headgear and pt head) Chin strap may help with oral leaks when using nasal masks Mask too large (*Most common problem) Full-face Bottom of mask should fit under bottom lip Top of mask should lie at the junction of nasal bone and frontal bone, fitted to cover (but not occlude) nares snuggly Sizes don’t fit that well; much work involved in getting them to fit. Don’t just make it tighter and tighter. 4/20/2019

Ventilators vs. Stand-Alone Units Most newer-generation ventilators have both invasive and non-invasive capabilities The fundamental difference between invasive and NIV is the ability to compensate for leaks What modes would we be using? There are also multiple stand-alone NIV machines on the market Fundamental difference is the use of single-limb circuits on NIV units NIV machines work on same principles as the OSA machines we see so often. So what changes when we only use one limb compared to two limbs? So flow goes in only one direction. How does pt exhale? Must be through a leak in the system as there is no exhalation valve back at the ventilator. How does machine maintain pressure? By varying level of flow; it must have a continual leak. What type of breath do I deliver? It has to be a pressure breath, so you have 2 levels of pressure: low and high. How does it trigger and sense an effort? It goes back to continual leak and the flow needed to maintain pressure; if pressure drops, you need more flow to maintain it – This is how it senses an effort, by a change in flow. This creates problems, as a change in leak will affect the ability to trigger. How does it measure a delivered breath? It doesn’t have an expiratory limb with an expiratory flow sensor to measure an exhaled breath. So is an estimation based on the flow delivered minus the estimated leak? It’s very inaccurate and dependent on the mask seal. 4/20/2019

NIV – Modes and Breath types Three main modes that can be used CPAP Bilevel PAV Note that these are all pressure breaths. Why? Proportional-Assist Ventilation CPAP (What is the difference between CPAP and PEEP?) – For specific uses: When no support is needed. For recruiting alveoli (reversing atelectasis), changing the gradient to improve oxygenation, redistributing fluid in pulm edema. There is one continual pressure; the vent changes flow to keep pressure constant, so more flow is delivered when pt is making an effort. Bilevel – Relates to PSV to levels of pressure, a low and high. Called IPAP and EPAP: When vent senses a breath it cycles from low to high pressure and vice versa. The triggering ability is based on changes in flow which is subject to failure. PAV we will talk about more later. These are all supportive modes. Much discussion in the past about the use of NIV with rates to ventilate patients. Massive problems with this. Can’t force air in non-invasively and know where it is going to go – You don’t know what the glottis is doing, just as likely to ventilate the stomach as the trachea, or ventilate a leak. Very high aspiration risk. Regardless of what you may read in the texts I can’t recommend it. Dysynchrony is a major concern with Bipap, if delivering a breath during exhalation you have discomfort, increase WOB and inflation of the stomach. 4/20/2019

Humidification Is necessary for patient comfort and safety Perhaps even more than invasive Must be used if ventilating for any prolonged period of time Be certain that humidifier does not interfere with operation of ventilator Use only humidifiers recommended by the manufacturer Must humidify if using for any length of time! 4/20/2019

Other Considerations Rebreathing of CO2 If flow through mask not high enough Oxygen concentration Depends on where oxygen is introduced into the machine Medication delivery MDI or SVN can be added in-line How much drug is delivered to patient? CO2 more of a concern in older models – Increase EPAP level to increase flow and washout of mask, or increase leak in/around mask. Changing O2 concentrations depending on the type of unit being used: Newer models can be hooked up to a high-pressure source and can precisely titrate the oxygen levels the machine delivers. For older or home-use models (OSA), you must Tee in oxygen, so O2 concentration will vary t/o breath cycle or if a leak changes. Delivery of medication is questionable through the machine, as the flows are very high to maintain PEEP, so you have large losses of drug compared to invasive delivery. So either give more drug (but how much?), or take pt off to give them drugs. 4/20/2019

Practical Application Choose a ventilator capable of meeting patient needs Choose the correct interface; avoid mask that is too large Explain therapy to the patient Silence alarms and choose low settings Initiate NPPV while holding mask in place Secure mask, avoiding a tight fit 4/20/2019

Practical Application Titrate both pressures to patient comfort Titrate FiO2 to SpO2 > 90% Avoid PIP > 20 cmH20 Titrate PEEP to SpO2 based on reason for initiation of therapy Continue to coach and reassure patient; make adjustments to improve patient compliance 4/20/2019

Strategy for Acute on Chronic Respiratory Failure Maximum conventional therapy Nasal mask ventilation Face mask ventilation Some rewrites needed Endotracheal Intubation and IPPV Wean conventionally Extubate and wean using NPPV/face mask 4/20/2019

Complications Leaks Mask discomfort and facial soreness, necrosis Eye irritation Sinus congestion Oronasal or airway drying Patient-ventilator dyssynchrony Gastric insufflation Hemodynamic compromise Acute MI?????????????? 4/20/2019

Monitoring the Effect Response to NPPV Physiologic – ABG, oximetry Objective – Respiratory rate, hemodynamics Subjective – Dyspnea, comfort, neurologic status Mask – Fit, comfort, leak, skin breakdown Respiratory muscle unloading – Accessory muscle use, paradoxical movement Abdomen – Gastric distension 4/20/2019

Chronic Applications Restrictive lung disease (Chest wall deformity, post-polio, ALS, muscular dystrophy, MS) Symptoms – Fatigue, dyspnea, morning headache PaCO2 > 45 mmHg Nocturnal oximetry with SpO2 < 88% for 5 consecutive minutes For progressive neuromuscular disease, Pimax < 60 cmH20 or FVC < 50% predicted COPD PaCO2 > 55 mmHg Look into more 4/20/2019

Chronic Applications AADL funding for BiPAP difficult without full polysomnographic testing Wait list over 2 years Must show reduction in PaCO2 AADL funding for CPAP requires Level Two Sleep Lab testing Long waiting list for evaluation If BiPAP indicated, must still wait for polysomnographic testing Review! Look into more 4/20/2019

Summary NPPV associated with a lower intubation rate and lower mortality in selected patients with acute respiratory failure, particularly COPD Clinician skill may be more important than the technical aspects Patient comfort may be the most important effect of NPPV to monitor What are the predictors of success? 4/20/2019