Airtravel in MCI

I K Rina

Dept of Cardiology/ Internal Med

Med Fac / UNUD

Arrow indicates atherosclerosis (stenosis) of the coronary artery

Medical needs The principal factors to be considered when assessing a patient’s

fitness for air travel are:

• Reduced atmospheric pressure. Cabin air pressure changes greatly during 15-30 minutes after takeoff and before landing, and gas expansion and contraction can cause pain and pressure effects.

• Reduction in oxygen tension. The cabin is at a pressure equivalent to an altitude of 6,000 to 8,000 feet and oxygen partial pressure is approximately 20% less than on the ground.

Conditions usually considered unacceptable for air travel

Although these are suggested limiting factors, each individual case must be considered on its merits and is dependent upon whether or not the passenger is accompanied by a professional escort.

• Severe anaemia, otitis media or sinusitis. • Acute, contagious or communicable disease. • Congestive Cardiac Failure (CCF) or other cyanotic conditions which are not fully controlled. • Uncomplicated Myocardial Infarction (MI) within 2 weeks of onset or complicated Myocardial Infarction (MI) within 6 weeks of onset. • Severe respiratory disease or recent pneumothorax. • Gastrointestinal (GI) lesions which may cause heamatemesis, melaena or intestinal obstruction.

Conditions usually considered unacceptable for air travel

• • Post-operative cases: a) Within 10 days of simple abdominal

operations. b) Within 21 days of chest or invasive eye surgery (not laser). • Fractures of the mandible with fixed wiring of the jaw (unless medically escorted) • Unstable mental illness without escort and suitable medication for the journey. • Uncontrolled seizures (unless medically escorted). • Pregnancies beyond the end of the 36 weeks. • Infants within 7 days of birth. • Introduction of air to body cavities for diagnostic or therapeutic purposes within 7 days.

Lung or Heart Disease:

• Guests suffering from cardiopulmonary disease which causes dyspnoea on walking more than 100m on the flat, or which has resulted in them requiring oxygen in hospital or at home (or in-flight previously) may require supplementary oxygen. The aircraft oxygen is for emergency use only.

• Guests with serious cardiopulmonary diseases and guests requesting continuous oxygen and the use of a stretcher should enclose a recent detailed medical report with their MEDIF requests.

Flight role for airtravel

Contraindications To Flying

• Uncomplicated MCI within 10 days;

• Complications during recovery, 3-4 weeks;

• Non-stabilized or severe heart failure; unstable angina; open heart surgery within 10 days.

• Acute deep vein thrombosis until stabilized on antiocoagulant therapy.

• Patients can safely travel unescorted after AMI if their risk of ischemia is low risk stratification examination prior to repatriation.

• People traveling abroad have a similar or even greater risk of becoming ill compared to the risk they have at home.

• Travelers suffer from essentially the same diseases abroad as they do at home.

• Accordingly, acute myocardial infarction (AMI) is an important disease both in terms of the number of patients affected while traveling and in terms of morbidity.

• Air transport of AMI and post-AMI patients confers special problems. The oxygen partial pressure drops from 150 mm Hg at sea level to 107 mm Hg at 8,000 feet, which corresponds to the cabin pressure in commercial flights at cruising altitude.

• The decreased oxygen pressure results in a lowering of the arterial blood oxygen saturation to 0.90 in healthy subjects, which is compensated for by an increase in tidal volume and a higher cardiac output caused by an increased heart rate.

• Limited oxygen delivery to the myocardium is central in the pathophysiology of AMI, and the decreased oxygen saturation during flight could aggravate the ischemia. The increased workload for the heart is known to lower the threshold of ischemic symptoms in patients with stable angina.

• A decrease in saturation has also been shown to increase plasma catecholamines and the risk of supraventricular cardiac arrhythmias in patients with ischemic heart disease transported by air.

• What the actual impact is of these physiological changes on post-AMI patients during flight is largely unknown because only few safety studies exist.

• How this should affect decision making on mode of home transportation for physicians responsible for patient transport is even less investigated.

• Current recommendations are from the pre-percutaneous coronary intervention (PCI) period and are based on theoretical considerations on the impact of flying on the post-AMI patients and tend to be quite simple (eg, that flying is not allowed for 2 wk after AMI).

• Risk stratification has become an important tool in evaluating the need of therapy for patients with ischemic heart disease.

• However, it is our experience that risk stratification is not always employed by the local hospitals. We speculated that the use of a risk stratification–based decision-making algorithm for planning the home transportation of post-AMI patients could allocate the need of costly medical escort to patients considered at risk and allow low-risk patients to travel safely without medical escort.

• Suggested that patients who have not been fully revascularized by PCI can be repatriated 14 days after the AMI, according to current guidelines.

• Recommended that AMI patients are handled and repatriated according to a risk stratification algorithm and that patients at low risk can safely be repatriated unescorted.

• Suggests that, provided that care is taken during the immediate preflight and postflight phases not to overexert the patients, neither supplemental oxygen nor medical escorts are needed in the transportation of patients who fly 2 wk after acute myocardial infarction.

Travel Restriction /Contraindications to Travel

• Background: Air Travel – FAA requires cabin pressure <8000 feet (2438m)

• Contraindications: Cardiac – Acute Myocardial Infarction

• First 4 to 6 weeks after Myocardial Infarction – No travel above 2,000 ft (610m)

• Subsequent (walk 328 ft or 100 m, climb 12 steps) – Limit = 8,000 feet (2438m)

– Congestive Heart Failure • No air travel for 2 weeks after decompensation • Exception: Oxygen and <10,000 ft (3048m)

– Air travel is safe in stable cardiovascular disease • Use below the knee Compression stockings • Walk inside the cabin • Avoid Alcohol and stay well hydrated

• Contraindications: Respiratory • Chronic Obstructive Pulmonary Disease (COPD)

– No air travel if Vital Capacity <50% of predicted

• Pneumothorax – No flight for 10 days

• Asthma – No restriction if stable

• Contraindications: Pregnancy • Physician must certify air travel after 36 weeks • No surface travel above 15,000 feet (4572m) • Contraindications: Hematologic • Anemia

– Oxygen needed if Hemoglobin <8.5 g/dl

• Hemoglobinopathies (Sickle Cell/Thalassemia) – Avoid air travel if SS or SC variant – No pressurized aircraft travel >22,000 ft (6705m)

Physiology and Potential Risks of Flight

• Areas of concern regarding air medical transport of cardiac patients include the effects of hypoxia at altitude, the effects of gas expansion at altitude, the effects of anxiety about flying, and the potential for complications related to movement of patients.

• Concerns regarding the effects of altitude are generally limited to fixed-wing aircraft as opposed to rotary-wing aircraft that fly at altitudes (eg, < 1,000 feet) where barometric pressure changes are minimal.

Effects of Hypoxia at Altitude

• In contrast with rotary-wing aircraft, fixed-wing engine propeller aircraft fly at altitudes of > 15,000 feet and jets fly at altitudes of 28,000 to 43,000 feet.

• Barometric pressure progressively decreases with altitude from 760 mm Hg at sea level to 140 mm Hg at 40,000 feet. The partial pressure of inspired oxygen (P2) decreases proportionally to the decrease in barometric pressure at increasing altitude (P2 = 0.21 × [barometric pressure − water vapor pressure]).

• The water vapor pressure at a normal body temperature is 47 mm Hg regardless of altitude. The P2 at 40,000 feet (approximately 20 mm Hg) is incompatible with human life. In order to make it possible for humans to fly at such altitudes, aircraft are pressurized to achieve cabin pressures at cruising altitudes equivalent to barometric pressures at 5,000 to 8,000 feet of altitude.

• At a cabin pressure of 8,000 feet, P2 decreases from 150 mm Hg at sea level to 107 mm Hg. In normal patients, this has been shown to decrease Pa2 from 98 to 55 mm Hg.

• In healthy individuals, this results in only a small decrease in blood oxygen saturation to approximately 90%; however, if a patient already has a reduced Pa2 on the ground, the decrease in oxygen saturation at altitude will be more significant.

• The physiologic response to a lowered Pa2 is chemoreceptor-induced hyperventilation, mediated primarily by an increase in tidal volume. Any residual systemic hypoxia is compensated for with increased cardiac output, mediated primarily through tachycardia.

• The increase in cardiac output in patients during international air ambulance missions was found to be proportional to the drop in oxygen saturation.

• Altitude-related decreases in P2 have been demonstrated to decrease ischemic threshold in men with exercise-induced angina, with cardiac ischemia occurring at the same internal workload (heart rate-BP product) but lower external workload (treadmill speed and incline) at higher altitude (10,000 feet vs 5,000 feet).

• Hypoxia is also a stimulus for atrial arrhythmias and is associated with premature ventricular contractions.

• The potential for increased sympathetic nervous system activity in-flight is an additional factor predisposing to arrhythmia.

Long-Distance Emergency Air Ambulance Transport

• Three of these studies document long-distance emergent transport of

cardiac patients by fixed-wing air ambulance. • Incenogle described 11 patients in cardiogenic shock (receiving IV

inotropic support, 8 requiring intra-aortic balloon pumps), transported a median of 1,160 miles: 6 patients by air ambulance and 5 patients by ground ambulance. All patients survived the transport without any medical complications of travel.

• Connor and Lyons reported on the air medical evacuation of seven patients after acute MI by the US Air Force. All patients were transported from remote areas to larger medical facilities capable of providing adequate medical care. The patients were transported within 7 days of symptom onset, after thrombolysis and at least 24 h of hemodynamic stability. Transportation time ranged from 4.4 to 12.2 h, and there were no in-flight complications.